Carbonic Anhydrase The Fastest Enzyme Biology Essay

Carbonic Anhydrase The Fastest Enzyme Biology Essay Carbonic anhydrase, abbreviated as CA, is the first identified zinc containing enzyme, (CA; carbonate hydro-lyase, EC 4.2.1.1) It is an enzyme that catalyzes the reversible hydration and dehydration of carbon dioxide to form carbonic acid, bicarbonate ions and protons. Being one of the fastest enzyme known, it is believed that one molecule of CA can process one million molecules of carbon dioxide  per second. The basic molecular structure of CA includes specific amino acid threonine 199, glutamate 106, histidine 64 and histidine residues namely His 93, His 95, and His 118. The mode of regulation of CA is being inhibited by various medically prescribed substances that act as non competitive inhibitors, an example is Acetazolamide. CA plays a major key role in the fluid balance and regulatory of pH in different parts of the body thus, Mutation of this enzyme may lead to several diseases.(1) CARBONIC ANYHYDRASE THE START: Breathing, a fundamental function in life The air that we breathe in has some valuable oxygen, an important molecule wherein it helps the breakdown of fats and sugars in our cells. From the blood, oxygen diffuses then binds with the hemoglobin to be transported in the cells of our body. A by product of sugar and fat breakdown in cells is called Carbon dioxide CO2). It is a key metabolite in all living organism and it needs to be removed from our body. Carbon dioxide is diffuse out of the cells and transported in the blood in different ways to get to the lungs. CA is transported in numerous forms, mainly as bicarbonate, HCO3-. Bicarbonate is a CO2- with an attached OH group. When the HCO3- reaches the lungs, it is transformed back to a CO2, so it can be exhaled from the body. The conversion of bicarbonate to carbon dioxide facilitates its transport into the cell; while the conversion of carbon dioxide to bicarbonate assists trap the carbon dioxide in the cell. This interconversion of carbon dioxide and bicarbonate develop at a slow physiological pH hence organism tend to produces an enzyme to hasten the process. This enzyme responsible for the speed up interconversion, which can be found in the red blood cells, is called carbonic anhydrase. Although the interconversion of bicarbonate to carbon dioxide can happen without the enzyme, CA can great increase the rate of the conversions up to a millions of fold. (2) STRUCTURE The CA molecule in general has ellipsoidal shape with the estimated dimension 4.1 x 4.1 x 4.7 nm. The active site is situated in a cavity having an approximately conical shape. The cavity is assessed 1.5 m wide at the way in and about 1.6 nm deep attaining almost the center of the molecule. The zinc ion is next to the peak of the cone and liganded into 3 imidazole groups. Figure 1. CA Structure (2) Figure 1. shows the structure of CA. Taken as a whole, is composed of 10-stranded anti-parallel beta-sheet enclosed with various elements of other secondary structure. The 6 alpha-helices and 10-beta sheets make up the secondary structure of carbonic anhydrase. The basic function of CA is basically to regulate the oxygen and carbon dioxide content of the blood that is needed in a human body. As the function suggests, the chemical structure of CA extremely lies with the presence of zinc that lies deep within its active site. Its common amino acid composition includes threonine, glutamate and histidine. The specificity of these 3 amino acids (threonine 199, glutamate 106, and histidine 64) plays a critical role in relation to the presence of zinc by charging it with a hydroxyl ion. The zinc cation is associated with three histidine residue protein backbone namely: His93, His95, and His118. As stated, zinc plays a major role in the reaction of CA. The zinc present in the active side of CA is being bound to water to be able to dissociate it into a proton and hydroxyl ion. The hydroxyl ion is being stabilized by the positively charged zinc, in this way; the hydroxyl ion is being prepared to attack the carbon dioxide inside the RBC. A closer look with CA can be seen in the figure below where the amino acid chains in the active site together with the zinc are evident. The role of the zinc basically includes the command of directional transfer of the bound hydroxyl to the carbon dioxide to be able to form bicarbonate ion. From the figure, it shows that the intermediate structure where the bicarbonate ion is still attached to the enzyme. The alanine replicated the side chain for amino acid 199 in this arrangement. Histidine 64 swings in the direction of and away from the zinc ion in every cycle of enzyme action although it is helping the zinc to recharge with a novel hydroxyl ion. The two locations of this residue, revealed in the bottom right figure, symbolize its movement throughout the action of enzyme. Almost immediately as the zinc is reloaded with an original water molecule together with the release of bicarbonate ion, the enzyme is set for another action on some new carbon dioxide molecule. (3) MECHANISM OF CATALYSIS The rate of catalysis of the CA is exceedingly pH dependent. It means that, the higher the pH, the catalysis is faster and as the pH reduces, the speed of the reaction falls down. The mean pH of this transition is near pH 7. (5) Figure 2. Mechanism of CA catalysis (6) Figure 2.0 shows the mechanism of CA catalysis. A zinc atom which is generally bound to four or more ligands differs in CA. In CA, three locations are occupied by imidazole ring of three histidine residues and an additional site is occupied by a water molecule. Thus the geometry form of the active site is tetrahedral. The zinc atom plays an important role in the mechanism of CA catalysis because it is responsible for the release of a proton H+ from a water molecule, which then generates a nucleophilic hydroxide ion. Then the carbon dioxide substrate will attach to the active site of the enzyme to react with the ion of hydroxide. The zinc-bound OH-  attacks the carbon of CO2  therefore converting it into a bicarbonate ion. This occurs since the zinc ion has the +2 charge, which attracts the oxygen of water. It then deprotonates the water, thus, converting it into a better nucleophile so that the newly converted hydroxyl ion can attack the carbon dioxide. After the nucleophilic att ack of zinc bound OH-, addition of water molecule displaces the bicarbonate ion from the metal ion. The CA is then ready for another cycle of catalysis. (7) KINETICS OF REACTIONS CA inhibitors are class of pharmaceuticals that control the activity of carbonic anhydrase. It is inhibited by two classes of compounds, a metal complex forming anions and others are isosteres and sulfonamides. Inhibitors ionize upon binding with the enzyme to give way an NH- group that relocates the zinc hydroxide ions and shares a hydrogen bond. There are roughly 25 clinically used CA inhibitors as a drugs. It is mainly established as antiglaucoma drugs, diuretics, hypotensive agents, anticonvulsants, anticancer agents, antiepileptics, with additional use in the management of duodenal and gastric ulcers, osteoporosis and neurological disorder. (8) Acetazolamide Methazolamide Dorzolamide Topiramate Figure 3. Illustrations of some CA inhibitors (9) Figure 3.0 shows some CA inhibitors like Acetozolamide which acts as a mild diuretic. It cures glaucoma, altitude sickness, and some benign intracranial hypertension. Methazolamide treats glaucoma present in dogs which is called Open-angle glaucoma. While Topiramate which is a weak inhibitor, alleviate epilepsy, lennox gastuat syndrome and migraine headaches. And another CA inhibitor is the, Dorzolamide or sulphonamide which treat ocular hypertension or open-angele glaucoma. (10) CA activator regulates the proton transfer processes between the active site and the solvent system. It also binds at the entrance of the enzyme of the active site. One of the strong activator of CA is Histidine. Some amines and amino acids like l-Trp (tryptophan), l-Phe (Phenylalanine),  d-DOPA (D- 3,4-dihydroxyphenylalanine),  l-Tyr (Tyrosine), 4-amino-l-Phe also works as activators of CA. These CA activators are potentially target for drug development that can be useful as a derivative for the enhancement of synaptic efficacy which can be able to treat various conditions like, depression, alzheimers disease, ageing, spatial learning and memory therapy enhancer. (11) MODE OF REGULATION: Acetazolamide Inhibitor In case of excessive contents of CA in blood and peripheral areas of the lungs, proper regulation and inhibition is needed. Acetazolamide is a non competitive inhibitor that is effective in giving control with the catalytic reaction of the enzyme. This chemical complex substance is medically used o treat different conditions of moderate up to severe metabolic or respiratory alkalosis. Alkalosis may happen if excess CA is being reacted with the bicarbonate and carbon dioxide ions in the RBC, causing extreme absorption of bicarbonate thus giving the erythrocyte more basicity rather than having enough and sufficient pH level. Acetazolamide action is explained by interfering with bicarbonate (HCO3-) reabsorption in the kidneys, thereby giving enough acidity in the RBC, and further results to alkalinizing the urine. The action of inhibition results further to decreased synthesis of aqueous humor of the eye and causes the lowering of intraocular pressure. The interaction of Acetazolamide with CA does not occur with the active site, only close or remote to the active site. The net effect of this inhibitor basically changes the shape of CA that obviously leads to the inability of the substrate to bind properly, results to no catalytic reaction. (12) CARBONIC ANHYDRASE IN HEALTH AND DISEASE: Carbonic Anhydrase is found in numerous places in the body, including in the cerebro-spinal fluid, cytosol of some cells and mainly in the red blood cells. Since CA generates and utilizes protons and bicarbonate ions, it plays a major key role in the fluid balance and regulatory of pH in different parts of the body. Absence or mutation of the CA enzyme may lead to several diseases.  Also, CA inhibitor contributes to several treatments of diseases. One of the linked diseases of CA is the Osteopetrosis with cerebral calcification and renal acidosis. It is a syndrome deficient with CA in the body commonly called as Marble brain disease. This happens because sulfonamide inhibitor of CA can produce metabolic acidosis and have shown that CA inhibitors blocks the parathyroid hormone-induced the release of calcium bone which causes bone resorption. And since CA is present in the brain and CA inhibitors inhibits the production of cerebral spinal fluid, mutation of CA lead to cerebral calcification. Other disease associated with the deficiency of specific type of CAIII is the Myastenia gravis. It is an autoimmune neuromuscular disorder that results to a weak muscle of a person. Defects in CA IV can cause retinitis pigmentosa, a degeneration of retinal photoreceptor, which a patient experiences night vision blindness and loss of midperipheral visual. (13) Glaucoma, a condition wherein a build up of fluid in the eyes occurs and this presses the optic nerve that caused damage, is treated with the use of CA inhibitors like acetazolamide, brinzolamide, dorzolamide, and methazolamide. These inhibitors lessen the amount of fluid in the eye rapidly by 40% to 60% thus lowering the pressure inside the eye of a person with glaucoma. It now lessens the risk of optic nerve damage which promote vision loss. But prolong use of this drug affects the same enzyme in the tissue and may lead to kidney and liver damage The CA also plays an important role in the secretion of acid through the catalyzed hydration of excreted CO2 in the stomach lining which is mainly responsible in digestion of food. It helps to make pancreatic juice alkaline and our saliva neutral. In summary, CA performs different role and functions at their specific locations. (14)

Metamorphosis :: essays research papers

The Metamorphosis   Ã‚  Ã‚  Ã‚  Ã‚  Members of a family are often affected when something suddenly changes. Family relationships and special bonds can be changed and sometimes even broken. The attitudes of family members may be altered around the sudden change. In Franz Kafka’s The Metamorphosis, a family’s bond is broken apart by a sudden change in Gregor Samsa. The author deals with changes in Gregor and within the whole family.   Ã‚  Ã‚  Ã‚  Ã‚  The family’s attitude changes throughout the book. Gregor’s sister, Grete, showed the largest change in attitude. In the beginning she felt sorry for her unfortunate brother and she continued to show that she still cared about him. She took care of him and fed him when no one else seemed to care. After seeing her “changed'; brother for the first time and being frightened by his appearance, “she lost control of herself and slammed the door shut again';. Grete still cared for her brother even though he had changed. Grete feeling sorry for Gregor, brought him an assortment of foods, to find out which ones he liked. She also wanted to help him out by removing the furniture from his bedroom so he could have more room to crawl around. Eventually, Grete began to feel annoyed and disgusted by the presence of her brother. By not caring anymore, she no longer fed nor acknowledged her brother. Grete was the first to announce that the family needed to get rid of Gregor. After his death she was content to go on with the rest of her life, with out the burden of her brother.   Ã‚  Ã‚  Ã‚  Ã‚  Gregor’s mother had a very similar attitude towards the change in Gregor. When she first saw him she had great sorrow. In the beginning, she refused to give up hope that Gregor would someday be normal again. She showed her feelings by disagreeing with Grete when she wanted to remove his furniture. She wanted the room untouched, so that when Gregor came back it would be exactly the same and he could easily forget the whole thing. As her attitudes changed in the end, she too became irritated by Gregor.   Ã‚  Ã‚  Ã‚  Ã‚  Gregor’s father had the hardest time accepting Gregor. His attitude towards him changed the quickest. He wanted to drive Gregor back into his room the minute he saw him. His father harshly chased him back to his room with a cane. His father injured his leg by shoving him through his tight door way. When Mr. Samsa found out that Gregor had left his room while he was out, he attempted to kill him. All in all it was the wound his

Electoral Process Essay -- Politics, Democracy, British Government

In most of the modern societies an electoral process is considered an important symbol of the democracy that represents the concept of freedom of choice and fairness. The UK coalition government is now facing the need to reform the process by choosing between FPTP system and AV. As the final decision can affect the whole society, it is necessary to carefully analyze advantages and disadvantages of both systems. FPTP allows a candidate to win by the majority of the votes. It is a straightforward system that requires comparatively simplified procedures. In addition, it usually provides stable and strong one-party government. Also, elected party usually governs effectively and carries on the manifesto promises. Another advantage is a good-organized constituency link between MPs and their constituents. They can easily contact their MP to have support (Coxall et al. 2003, Jones and Norton 2010). Finally, FPTP tent to limit extremist parties like fascist, racist and other â€Å"hate† parties, for example British National Party. However, there are several disadvantages that should be considered. The most important weakness and the major criticism of FPTP system is ‘wasted votes’ issue (Lowe et al. 2010, p.115). For instance, in 2005 the UK General Election 65% of overall votes was wasted (BBC news 2005). Each vote is significant as it affects final results. Moreover, wasted votes lead to depressed turnout. Less people are willing to vote as they think their votes are not counted or make no change because there is a constantly winning party called ‘Safe seat’. In the last election, for instance, many people wanted to vote for Liberal-Democrats party, ‘safe seats’ and wasted votes dissuaded them to do it (Lowe et al. 2010, Jones and Norton ... ...h, the problem of wasted votes and disproportional allocation become more serious year by year (P. Whiteley 2010). The statistics show that turn out in UK is increasing from 2001 year coming to the level of 65.1%. In addition, elections require huge spending from the government and parties (UK political Info 2010a, 2010b, Jones and Norton 2010). As UK government is currently facing a need to cut the budget up to 40%, AV is not a useful method (Pollwatch 2010, J. Bingham 2010). To sum up, AV system adoption is a quite controversial question. Although AV system is solving some problems of FPTP system and providing fairer conditions for candidates and electors, adoption of this system can be quite difficult for the UK Coalition Government in term of budget and time spent. In my opinion, it is better to remain current election system as careful analysis is required.

Database Integration :: essays research papers

1. System Architektur Folgende Tools werden von uns fà ¼r verwendet, die es uns erlauben unseren Partnern eine sichere E-commerce Là ¶sung anzubieten.  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Apache Web Server  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Mod_SSL – Ein Modul fà ¼r SSL (Secure Socket Layers)  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  OpenSSL – Open Source Toolkit (benà ¶tigt fà ¼r Mod_SSL)  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  MySQL – Ein SQL Datenbank-Server  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  PHP4/Zend – Eine Server Sided Scripting Language Diagramm 1; System Architektur 2. Datenbank Integration Um den Kunden online Preisvergleiche anbieten zu kà ¶nnen, mà ¼ssen wir unsere Partner integrieren. Dazu benà ¶tigen wir eine Datenbank, die uns erlaubt die Politzen zu kalkulieren und es Ihnen ermà ¶glicht durch unser Back End die Daten mit einem Klick zu erneuern. Zur Integration der Datenbank mà ¶chten wir folgende Schritte vorschlagen:  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Festhaltung Ihres Datenbanksystems  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Eruierung der Variablen die fà ¼r die Kalkulation benà ¶tigt werden  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Erstellung der Datenbank die Sie zum uploaden verwenden kà ¶nnen (Praktisch werden in der bereits bestehenden RDBMS (Relational Database Management System) neue Tabellen erstellt, die die Variablen zur Berechnung enthalten. Sollten sich Tarife à ¤ndern kà ¶nnen Sie dann selbstà ¤ndig Ihre Daten erneuern (Back End))  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Entwicklung des Back End (siehe 3. Das Back End) Systems Diagramm 2; Datenbank Integration 3. Das Back End Das Back End ermà ¶glicht es unseren Partnern Ihre Datenbank selbstà ¤ndig up-zuloaden. Dafà ¼r entwickeln wir eine Userplattform, in der Sie mit einem Username/Passwort – Erkennung Ihre Datenbank uploaden kà ¶nnen. Weiters checken wir Ihre IP – Adresse um sicher zu gehen, damit niemand anders Zugriff auf die Daten hat. Das Back End ist eine Webseite, auf die unter der URL http://www.versicherungsmarkt.at, mit einer anderen Portnummer (:2001) auf die mit den Sicherheitsdevicen zugegriffen werden kann. Username/Passwort – Erkennung  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Die Username/Passwort – Erkennung wird mit PHP4/Zend erstellt, und ermà ¶glicht es Ihnen im Gegensatz zu einer Apache – Erkennung „auszu-loggen.â€Å"  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Es ermà ¶glicht uns die Zugriffszeit zu limitieren. Zum Beispiel, wenn jemand fà ¼r im System eingeloggt ist und die Seite fà ¼r 30 Minuten nicht gebrowst hat, wird bei erneuten Zugriff eine Username/Passwort – Erkennung verlangt.  ·Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Die Erkennung erfolgt pro Seite. Sie kà ¶nnen auf Seitenbasis bestimmen, fà ¼r welche Seiten eine Erkennung zu erfolgen hat. Checking IP – Address Durch das Checken der IP – Adresse kà ¶nnen wir sicherstellen, dass nur bestimmte Rechner auf das Back – End Zugriff haben.

France Essay -- essays research papers

France is a beautiful and captivating country full of art, culture, and an important historical background. It is in the heart of Europe and is sometimes called "The Hexagon", Because of it’s shape. It is the largest country in Western Europe and covers about 211,200 square miles. Four different waters surround the French coastline, this includes; the North Sea, the English Channel, the Mediterranean Sea, and the Atlantic Ocean. The capital of France is Paris, on the banks of the Seine River. Sometimes called the "The City of Lights", Paris has been admired and loved by millions for centuries. It is an industrial center as well. Paris is world renowned as a cultural and intellectual center which holds many masterpieces. The Eiffel Tower was built in 1889, and today is 1,052 ft. high. It welcomes tourists from all over the world. The revolution of 1789 was a very important part of history. The people could be divided into three groups, the Nobles, the Clergy, and the rest. At this time the peasants owned 80 percent of the land, but had no rights at all. To add to their misery, the food was in short supply. It is estimated that on the eve of the French Revolution one-fifth of the population had no resources at all. World War I broke out August 1914, setting France, Russia, Britain, Belgiumand Serbia at war with Germany and the Austro-Hungarian Empire. Everyone assumed the war would be over in a few months. Instead, the war lasted for four years. Germany finally agreed to sign an armistice on November 11, 1948. (A kind of peace agreement). The death toll had been the largest of any previous wars. France had lost over 1.4 million men and in all of Europe over 8.5 million were killed. People said it was the war to end all wars. Only twenty years later France was plunged into another war with Germany. On June 22, 1940 France was forced to sign an agreement with Germany. By 1942 France was totally occupied by the Nazi army. This was a very hard time, Jews were persecuted and thousands were sent off to concentration camps. Eventually, in the summer of 1944 France was freed, and the occupation was over. The President is head of the government and is elected by the ... ...s developed a number of ways of producing energy. Such as dams, Solar energy, hydroelectricity or "white coal", hot springs, and tidal energy. France has had an important nuclear power program since 1967. Two-thirds of the country’s electricity is produced by atomic energy. France’s transportation system centers on Paris which is the heart of a network that stretches to all parts of France. Trains are an important source of transportation throughout France. The latest in a line of new fast trains, which includes the mistral and the Turbo trains, is the high-speed TGV. This train averages 133 miles per hour. The French railway of SNCF has a reputation for being fast, efficient, and reliable. It is also punctual. So much emphasis is placed on punctuality that is an engineer does not keep on time, he is fined. Also roads, air, and water travel is important to France. Communications are expanding widely in France. Mainly in ways such as telephone, television, radios, and newspapers. The national language of France is French. French was once the language used by diplomats all over the world. In this study, I have learned a lot about France and I hope to visit there someday.

Thermodynamic Analysis and Performance Characteristics

AEROSPACE ENGINEERING SCHOOL OF MECHANICAL ENGINEERING AND DESIGN THE THERMODYNAMIC ANALYSIS AND PERFORMANCE CHARACTRISTICS OF A TURBOFAN JET ENGINE By J. E, Ibok 2011 Supervisor: Dr Lionel Ganippa ABSTRACT This work focuses on the performance analysis of a twin spool mixed flow turbofan engine. The main objective was to investigate the effects of using hydrogen, kerosene and natural gas fuel on the performance characteristics such as net thrust, specific fuel consumption and propulsive efficiency of the turbofan.Another aim of this work was to introduce the concept of exergy and thermoeconomics analysis for twin spool mixed flow turbofan engine and show the components that contributes the most to the inefficiency of the engine. A generic simulation was carried out using Gas Turb 11 software to obtain reasonable analysis results that were verified with a real-time JT8D-15A turbofan engine. The parametric analysis was done for constant value of mass flow rate of fuel and constant turb ine inlet temperature for all three fuels.The result were rightfully obtained for these analysis cases and discussed accordingly. Brunel University Mechanical Engineering Academic Session: 2010/2011 Name of Student: Johnson Essien Ibok Supervisor:Dr Lionel Ganippa Title: The Performance Characteristics and Thermodynamics Exergy and Thermoeconomics analysis of a Twin Spool Mixed Flow Turbofan Engine Operating at 30,000ft at M0 0. using Kerosene, natural Gas and Hydrogen Fuel. Abstract: This work focuses on the performance analysis of a twin spool mixed flow turbofan engine. A generic simulation was carried out using Gas Turb 11 software to obtain reasonable analysis results that were verified with a real-time JT8D-15A turbofan engine. The parametric analysis was done for constant value of mass flow rate of fuel and constant turbine inlet temperature for all three fuels.The result were rightfully obtained for these analysis cases and discussed accordingly. Objectives: The main aim of this work is to conduct the parametric cycle simulation of a twin spool mixed flow turbofan engine and investigate the performance characteristics of it. Another aim of this work is to show the effects of using hydrogen, Kerosene and natural gas fuel on the overall performance of the twin spool mixed flow turbofan engine.Also, the purpose of this work is to introduce the use of the second law of thermodynamics analysis known as exergy and thermoeconomics in analysis the twin spool mixed flow turbofan engine Background/Applications: This work is applicable in so many ways when it comes to the overall performance optimization and feasibility analysis of a jet engine. This work relates to the aerospace and aviation industries since the turbofan engine is amongst the vast number of jet engine used in propulsion of aircrafts.There is increasing pressure in the aviation industry to reduce pollution and depletion of energy resources while at the same time maintaining reasonable investment cost and high overall performance. Hence, this research was conducted in hopes of coming up with a new solution to this problem. Conclusions: The main conclusion drawn from the performance analysis is that hydrogen fuel produced the highest thrust level and the lowest specific fuel consumption between the three fuels for a constant mass flow rate of fuel.Kerosene fuel generated thrust level can be increased if it is mixed with a small amount of hydrogen. The Exit jet velocity ratio remained constant despite the increasing bypass ratio for all three fuels at constant mass flow rate of fuel. Using the exergetic analysis showed that the combustion chamber and the mixer contributed the most to the inefficiency of the turbofan engine. The amount of exergy transferred into the turbofan engine by hydrogen was depleted in the smallest ratio compared to natural gas and kerosene for constant mass flow rate of fuel.The thermoeconomics analysis showed that it is preferable to use local based co st evaluation to quantity specific thermoeconomics cost of thrust than the global method since the value was lower. Results: The results obtained from the simulation using Gas Turb 11 produced an error range of 0. 25% – 8. 5% when verified with the actual test data of the JT8D-15A turbofan engine. The results obtained for the analysis defined a reference design point at which the parametric analysis was conducted on. The analysis was done in three cases as shown clearly in the test matrix in table 1 below.Analysis| Parameters being varied| Parameters Kept Constant| Performance Characteristics| case 1| * Bypass ratio * Turbine Inlet temperature| * HPC Pressure Ratio * LPC Pressure Ratio * Fan Pressure Ratio| * Velocity ratio * Fuel-Air-ratio * Turbine inlet temperature * Net thrust * Specific Fuel Consumption * Thermal efficiency * Propulsive efficiency| case 2| * Bypass Ratio * Three different fuelsmH2mCH4mC12H23| * Mass flow rate of fuel * HPC Pressure Ratio * LPC Pressure R atio * Fan Pressure Ratio| | Case 3| * Bypass Ratio * Three different fuelsmH2mCH4mC12H23| * Turbine inlet temperature * HPC Pressure Ratio * LPC Pressure Ratio * Fan Pressure Ratio| | Table 1 The Test matrix of the Parametric Analysis. The exergy analysis was done for the parametric analysis of case 2 and case 3 where the exergy destruction rates, exergetic efficiency, exergy improvement potential rate and fuel depletion ratio were calculated. The distribution of these results throughout each component of the turbofan engine was represented with bar charts and Grassmann diagram. The thermoeconomics analysis was conducted for analysis case 2 using kerosene fuel.The specific thermoeconomics cost of thrust was calculated using global and local based cost evaluation methods. ACKNOWLEDGEMENTS First of all, I would like to thank my parents for their financial support and encouragement because without them I would not be here and be able to do this work. I am deeply thankful to my supervi sor, Dr Lionel Ganippa for believing in me and giving me the opportunity to work with him in this field of study. I am also thankful to him for giving the necessary guidance and advice and his enthusiasm and innovative ideas inspired me. Finally, I would like to thank Mr Joachim Kurzke for providing me with the necessary software needed for my dissertation. Table of ContentsAcknowledgements i Contents ii List of Notations and Subscripts iv List of Tables vi List of Figures vi Chapter 1: Introduction1 1. 1. Aims and Objectives2 1. 2. Computational Modeling3 Chapter 2: Jet Engines4 2. 1. Performance characteristics4 2. 1. 1. Thrust4 2. 1. 2. Thermal Efficiency5 2. 1. 3. Propulsive efficiency5 2. 1. 4. Overall efficiency6 2. 1. 5. Specific Fuel Consumption6 2. 2. Fuel and Propellants For Jet Engines7 Chapter 3: Turbofan Jet Engines †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ †¦8 3. 1. Introduction 8 3. 2. Classification of Turbofan Engines9 3. 3. Major Components of a Turbofan Engine10 3. 3. 1. Diffuser10 3. 3. 2. Fan and Compressor11 3. 3. 3. Combustion Chamber12 3. 3. 4. Turbine13 3. 3. 5. Exhaust Nozzle14 3. 4.Thermodynamic Process and Cycle of a Twin Spool Mixed Flow Turbofan Engine15 Chapter 4: Mathematical and Gas turb 11 Modeling of the turbofan Engine18 4. 1. Station Numbering and Assumptions18 4. 2. Design Point Cycle Simulation of the Turbofan Engine18 4. 3. Off-design Point Cycle Simulation of the Turbofan Engine21 4. 3. 1. Module/Component Matching 22 4. 3. 2. Off-Design Point Component Modeling22 Chapter 5: Methodology, Results and Discussions26 5. 1. General Relationship equations of the Major Parameters27 5. 2. Results and Discussions of Parametric cycle Analysis of Case 129 5. 3. Results and Discussions of Parametric Cycle Analysis of Case 235 5. 4.Results and Discussions of Parametric Cycle Analysis of Case 343 Chap ter 6: Exergy and Thermoeconomics Analysis of the Turbofan Engine49 6. 1. Exergy Analysis49 6. 1. 1. Exergy Analysis Modeling 50 6. 1. 2. Exergy and Energy Balance Equations of the Components58 6. 1. 3. General Relationships in Exergetic Analysis of the Turbofan Engine60 6. 1. 4. Results and Discussions61 6. 1. 5. Grassmann Diagram72 6. 2. Thermoeconomics Analysis74 6. 2. 1. Thermoeconomics Analysis Modelling74 6. 2. 2. Global Based Cost Evaluation76 6. 2. 3. Local Based Cost Evaluation77 6. 2. 4. Results and Discussion of the Thermoeconomics Analysis78 Chapter 7 Conclusions and Future Work80 Reference Appendix A Exergy Analysis Results Appendix B Thermoeconomics Analysis resultsList of Notations and Units ?| Isentropic efficiency| ?| Total Pressure ratio| m| Mass Flow Rate (kg/s)| f| Fuel/Air Ratio| M| Mach Number| Pt| Total pressure (kPa)| Tt| Total Temperature (K)| NCV| Net Calorific Value (MJ/kg)| Ht| Total Enthalpy (kJ/kg)| V| Velocity (m/s)| ?| Bypass Ratio| T| Static Temperat ure (K)| P| Static Pressure (kPa)| N| Actual Spool Speed (RPM)| Nc| Corrected Spool Speed (RPM)| mc| Corrected Mass Flow Rate (kg/s)| R| Universal Gas Constant (kJ/kmolK)| ?0| Standard Chemical Exergy (kJ/kmol)| Ex| Exergy Rate (MW)| xi| Mole Fraction| cp| Specific Heat at Constant Pressure (kJ/kgK)| ?| Ratio of Chemical Exergy to NCV| ?| Exergetic Efficiency| | Fuel Depletion Ratio| W| Power Rate of Work done (MW)| List of Subscripts| | LPT| Low Pressure Turbine| HPT| High Pressure Turbine| CC| Combustion Chamber| HPC| High Pressure Compressor| LPC| Low Pressure Compressor| d| Diffuser| noz| Nozzle| mix| Mixer| dest| Destruction Rate| 0, ambFAR| Ambient conditionFuel-Air-Ratio| CH| Chemical| PH| Physical| KN| Kinetic| PN| Potential| IP| Exergy Improvement Potential Rate (MW)| CRF| Cost Recovery Factor| c| Specific Thermoeconomic Cost (MJ/kg)| STD| Standard Temperature and Pressure| TIT| Turbine Inlet Temperature| TSFC| Thrust Specific Fuel Consumption (g/kNs)| SFC| Specific Fuel Co nsumption| p| Propulsive| TH| Thermal|O| Overall| T| Thrust| equip| Equipment| PEC| Capital Cost of Equipment| List of Tables Table 1 input parameters for Design Point Cycle Simulation on Gas Turb 1119 Table 2 Comparison table for the Actual Test Data and Simulated Data using gas Turb 1121 Table 3 Comparison Table for Actual Test Data and Simulated Off-Design Point data Using gas Turb 11. 25 Table 4 Equivalence Ratio of the three Fuels Combustion Processes†¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ 62 Table 5 Assumed Capital costs of Each Component of the Turbofan Engine. 75 Table 6 Flow of Specific Thermoeconomics Cost in all the Components 79 List of Figures Figure 1 Classification of Turbofan Engine9Figure 2 Layout of Forward Fan Twin Spool Mixed Flow Turbofan16 Figure 3 T-S Diagram for the Forward Fan Twin Spool Mixed Flow Turbofan17 Figure 4 Design Point Cycle Simulation Algorithm Using Gas Turb 1120 Figure 5 Example of a Compressor Performance Map/Cu rve24 Figure 6 Effects of Varying Bypass Ratio at Constant Values of TIT on Fuel-Air-Ratio30 Figure 7 Effects of Varying Bypass Ratio at Constant Values of TIT on Exit Velocity Ratio30 Figure 8 Effects of Varying Bypass Ratio at Constant Values of TIT on LPT Exit Pressure Ratio31 Figure 9 Effects of Varying Bypass Ratio at Constant Values of TIT on Net Thrust32 Figure 10 Effects of Varying Bypass Ratio at Constant Values of TIT on Specific Fuel Consumption33 Figure 11 Effects of Varying Bypass Ratio at Constant Values of TIT on Propulsive Efficiency34 Figure 12 Effects of Varying Bypass Ratio t Constant Values of TIT on Thermal Efficiency35 Figure 13 T-S diagram of using Hydrogen Fuel when the bypass Ratio is increased36 Figure 14 Variation of Fuel-Air-Ratio with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels37 Figure 15 Variation of TIT with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels37 Figure 16 Variation of Exit Velocity Ratio with Byp ass Ratio at Constant Fuel Flow Rate using three different Fuels38 Figure 17 Variation of LPT Exit Pressure Ratio with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels39 Figure 18 Variation of Net Thrust with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels40 Figure 19 Variation of Specific Fuel Consumption with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels41 Figure 20 Variation of Thermal Efficiency with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels42 Figure 21 Variation of Propulsive Efficiency with Bypass Ratio at Constant Fuel Flow Rate using three different Fuels43 Figure 22 Variation of Fuel-Air-Ratio with Bypass Ratio at Constant TIT using the three Different Fuels44 Figure 23 Variation of Exit Velocity Ratio with Bypass Ratio at Constant TIT using the three Different Fuels44 Figure 24 Variation of LPT Exit Pressure Ratio with Bypass Ratio at Constant TIT using the three Different Fuels45 Figure 25 Variation of Net Thrust with Bypass Ratio at Constant TIT using the three Different Fuels46 Figure 26 Variation of Specific Fuel Consumption with Bypass Ratio at Constant TIT using the three Different Fuels46 Figure 27 Variation of Propulsive Efficiency with Bypass Ratio at Constant TIT using the three Different Fuels47 Figure 28 Variation of Thermal Efficiency with Bypass Ratio at Constant TIT using the three Different Fuels48 Figure 29 Variation of Exergy Destruction Rate Using the three Fuels for Analysis Case 262 Figure 30 Variation of Exergy Destruction Rate Using the three Fuels for Analysis Case 364 Figure 31 Variation of Exergetic Efficiencies Using the three Fuels for Analysis Case 266 Figure 32 Variation of Exergetic Efficiencies Using the three Fuels for Analysis Case 367 Figure 33 Distribution of Exergy Improvement potential Rate Using the three Fuels for Analysis Case 268 Figure 34 Distribution of Exergy Improvement potential Rate Using the three Fuels for Analysis Case 369 Figure 35 variation of Fuel Depletion ratio using the Three Fuels for Analysis Case 270 Figure 36 variation of Fuel Depletion ratio using the Three Fuels for Analysis Case 371 Figure 37 Grassmann Diagram for the Exergetic analysis of Case 2 using kerosene Fuel for the Turbofan engine. 72 Chapter 1 Introduction Jet engines are complex thermodynamic systems that use a series of non-linear equation to define their thermodynamic processes and they operate under the principle of Brayton cycle.Brayton cycle is a cycle that comprises of the compressor, combustor and turbine working as a unit. Additionally, the major parameters that dictate the operational conditions of the engine at any point during the process are the relative altitude and Mach number. Mach number is the ratio of the velocity of the jet engine to the speed of sound. Basically, the main purpose of this type of thermodynamic system in aerospace industry is to accelerate a jet of air and as a result, generate enough thrust needed for flight. In addition, the design of jet engines is dependent of what purpose it will be used for in order to derive its maximum performance.For instance, in military application, jet engines are required to generate maximum thrust in minimum response time which consumes a lot of fuel whereas commercial jet engines are required to less noise generative, less fuel consuming and at the same time have high overall efficiency (El-sayed, 2008). There are certain factors that jet engine manufacturers take into consideration when designing jet engines which are the operating cost, engine noise, environmental emissions, fuel burn and overall efficiency. Accordingly, this has caused a global market competition for engine manufacturers like Rolls Royce, Pratt and Whitney, General Electric and CFM on who can produce the most efficient jet engines.In fact, Pratt and Whitney Company is working on a geared turbofan jet engine that they believe will reduce fuel burn, produce lesse r noise and emit less toxics while General Electric is coming up with simpler â€Å"ecore† jet engines that will be more fuel efficient than the current jet engines with as much as almost two fifths of current jet engines (Cassidy, 2008). Taking all that has been said into consideration, it can easily be asserted that by reducing the fuel consumption of the jet engine, the total temperature at the turbine blades will reduce thereby increasing the operating life and overall efficiency of the engine. Also, the total cost of the engine can be cut down. Indeed, Dr Pallan cited in (Ward, 2007) stated that reducing the fuel consumption by as little as 1% is highly longed after by engine manufacturers and this can result in very significant increase in the overall performance.In a general point of view, it can be said that the maximum point of achievement for jet engine manufacturers would be to design an engine that consumes the minimum amount of work in the compressor unit while g enerating the maximum amount of work in the turbine unit at minimum fuel supply. The main purpose of this work is to analyse the thermodynamic processes and performance of a jet engine using a simulation tool, exergy and thermoeconomics concept. 1. 1. Aims and Objectives The main objective of this work is to carry out the thermodynamic analysis and show the performance characteristics of a turbofan jet engine. In this work, the vivid explanation of the thermodynamics processes and cycle of each component of the turbofan engine starting from the diffuser to the nozzle will be covered. Also, the first and second law of thermodynamics with other laws will be applied extensively throughout this work.However, in the aspect of performance characteristics of the turbofan engine, a generic simulation will be carried out on a twin spool mixed flow turbofan engine. To relate this work to real life application, a JT8D-15A turbofan engine manufactured by Pratt and Whitney Company will be used a s the twin spool mixed flow turbofan for the simulation using the original design data. Indeed, the simulation tool that will be used is GasTurb 11 which was designed by Joachim Kurke and for more details on how it works can be found in (Kurke, 2007). This work will use the reference design point of the twin spool mixed flow turbofan at sea level with maximum take-off thrust to obtain the operating point of 30,000ft at M0 0. using the off-design performance simulation which will serve as the operating design point for the analysis in this work since the engine will spend most of its time in the cruise phase between 30000ft to 38000ft. The purpose of carrying this generic simulation of the turbofan engine is to investigate the effects of varying bypass ratio and turbine inlet temperature (thermal limit parameter) on the performance characteristics of the turbofan engine. In other words, the parametric cycle studies of the turbofan engine. This investigation will be done for three dif ferent cases which case 1 will be studying the effects of varying bypass ratio and turbine inlet temperature on the performance characteristics of the turbofan engine when some of the design choices are kept constant.The second case of study will be the comparison of the performance characteristics of the turbofan engine when three different fuels (kerosene, natural gas and Hydrogen) are used at the same mass flow rate using the same design point in case 1. Finally, the third case of study will be the comparison of the performance characteristics of the turbofan engine when the three fuels are undergoing the same combustion process that is constant turbine inlet temperature for the design point in case 1. This aspect of this analysis is very important owing to the growing problem of greenhouse effect and depletion of energy resources. In fact, statistics by the intergovernmental panel shows that aerospace industry is amongst one of the fast growing sources of greenhouse effect and t hat the emission of carbon dioxide will increase to five times what it is presently which is 3% (Symonds, 2005).Based on this, using alternative fuels like hydrogen and natural gas can tend to reduce pollution and consumption of energy resources risk and this work aims to show how that can be achieved while the overall efficiency of the engine is still high. Another approach of analysis in this work will be the use of the second law of thermodynamics analysis also known as exergy and thermoeconomics. This aspect of analysis of the turbofan engine will be done for the parametric analysis of case 2 and case 3 in efforts to also compare the three fuels that are being considered and show which fuel will cause the turbofan engine components to be most inefficient or have the most irreversibility.This analysis will be done by calculating the exergy relationships such as exergy transfer rates, exergy destruction rates, exergetic efficiencies, exergy improvement potential rates, and fuel de pletion ratios. Furthermore, the exergy analysis will be represented in a Grassmann diagram for parametric analysis case 2 of study. However, as for the thermoeconomics analysis of the turbofan engine, only parametric analysis case 3 studies will be done for only kerosene fuel and this work will aim to show how to use concept of local and global evaluation of thermoeconomic cost. 1. 2. Computational Modelling It will be very expensive and time wasting to design and develop new aircraft engine whenever an optimization or analysis wants to be done.In fact, Caoa Y, Jin, Meng and Fletcher (2005) stated that new ways should be developed to reduce aircraft engine design, maintenance and manufacturing cost in order to have effective worldwide market competition. Surprisingly, computer modelling is one approach of reducing manufacturing cost and time wasting. Computational modelling can simply be defined as the use of computer codes to replicate a typical system using some of its original d ata in order to analyse the system at varying conditions. The other side of the medallion shows simulation. There are many types of simulation tools normally used in simulating gas turbines such as Matlab/simulink, Modelica, Gas Turb 11, NPSS and many more. However, the simulation tool that will be adopted for the purpose of this dissertation is Gas Turb 11 designed by Joachim Kurzke.Gas Turb 11 is a language oriented program with a command prompt that calculates the output data without using block diagrams or graphical interface. It is user friendly in a sense that it is easy to find the tools library and to substitute data in for simulation. The Gas Turb 11 is specifically designed for simulation of all kinds of gas turbines starting from power generators to jet engines. Gas Turb 11 usually carries out two types of analysis which are the on design cycle point simulation and off-design cycle point simulation. Engine design point cycle simulation involves the study of comparing gas turbines of different geometry. This cycle design point must be defined before any other simulation can be done.On the other hand, off-design performance cycle point simulation involves the study of the behaviour of a gas turbine with known geometry. This cycle outlines the performance characteristics of each component such as performance maps, Overall efficiency. The type of simulation that will be done in this dissertation will involve the off-design and design point cycle. Chapter 2 Jet Engines 2. 1. Performance Parameter of Jet Engines 2. 2. 1. Thrust Thrust is the way of quantifying the ability of a jet engine to effectively utilise the energy added to it in order to propel or push itself forward in the opposite direction of the exiting jet in the exhaust nozzle.In other words, it is the reactive force to the force imparted by the exiting jet in the nozzle in accordance to Isaac Newton’s third law of motion. It is the most important parameter that has to be obtained for any jet engine and it depends heavily on the ingested mass of air, exiting velocity and pressure, the area of the nozzle, the flight velocity and ambient conditions. In fact, the mathematical expression for thrust which incorporates these factors is shown below as. Thrust=meVe-m0V0+Pe-P0Ae Where, e=the exit conditions at the exhaust nozzle, 0=ambient conditions at the inlet me=m0+mfuel Momentum Thrust=meVe; This is the thrust obtained from the reaction of the hot exhaust gases high velocity.Momentum Drag= m0V0 ; This the friction or drag force caused by the high velocity ingestion of air mass at the inlet. Pressure Thrust=Pe-P0Ae; This force is generated as a result of the higher exit static pressure compared to the ambient pressure which pushes back at the engine. Gross Thrust=meVe+Pe-P0Ae; It is the maximum obtainable positive thrust a jet engine can have when the drag forces are ignored. Special Cases of Thrust Take-off Thrust It is the thrust a jet engine can generate with its o wn power at static or low power setting which means the momentum drag component of thrust is ignored and the power of the engine at this point is equivalent to zero.This can be used to explain why the thrust of an engine at take-off condition is usually higher than at cruise condition since there is no momentum drag and effects of varying ambient condition. This only applies to turbojet, turbofan, and turboprop jet engines but when it comes to ramjet and scramjet, the air flow has to be accelerated by a booster system before it can start producing a positive take-off thrust. Pressure Thrust Component This is the thrust generated as a result of the static pressures of the exiting jet and ambient environment. In ideal cases where the nozzle has perfectly expanded the jet exit pressure to that of the ambient condition, the pressure thrust component will disappear which this case is not possible in reality.However, if the nozzle is choked which indicates that the ambient pressure is low er than the exit pressure of the jet, the pressure thrust component will have a positive effect on the net thrust. Also, if the nozzle tends to over expand the jet because of low energy addition to the jet and the exit pressure is lower than the ambient pressure, the pressure thrust component will have a negative effect on net thrust. 2. 2. 2. Thermal efficiency It is simply the measure at which energy in the engine system is converted. In other words, it is the measure at which total energy supplied to the engine system as heat transfer is converted to kinetic energy.In another way, it can easily be said to be the ratio of the power generated in the engine airflow to the rate at which energy is supplied in the fuel. ?TH=Power Generated in the Engine AirflowRate of Energy Supplied in the Fuel =12? meVe2-12? m0V02mfuel? NCV 2. 2. 3. Propulsive efficiency It is a measure at which kinetic energy possessed by air as it passes through the engine is converted into power of the propulsion of the engine. In mathematical terms, it is simply known as the ratio of thrust power to the power generated in the engine airflow. ?p=Thrust PowerPower Generated in the Engine Airflow = T? V012? meVe2-12? m0V02 2. 2. 4. Overall EfficiencyAs the name overall depicts, it is the resultant efficiency of a jet engine can have which is simply the product of the thermal and propulsive efficiencies. In mathematical terms, it is represented as shown below. ?O=? TH p =12? meVe2-12? m0V02mfuel? NCV? T? V012? meVe2-12? m0V02 =T? V0mfuel? NCV 2. 2. 5. Specific Fuel Consumption Specific fuel consumption as any other performance characteristics is a ratio and surprisingly it has a major effect on the economics of the aircraft as it is used to determine the aircrafts flight ticket costs. Specific fuel consumption has different expressions depending on what type of jet engine it is. For instance, in ramjet, turbojet and turbofan jet engines, it is the measure of the fuel mass flow rate to the thrus t force generated.Also, it is sometimes called the thrust specific fuel consumption (TSFC). TSFC=mfT However, in turbopropeller jet engines, it is the ratio of the fuel mass flow rate to the power generated in the engine shaft by the turbomachinery. It is sometimes referred to as the brake-specific fuel consumption (BSFC). TFSC=mfSP 2. 2. Fuel and Propellants for Jet Engines Fuels can implicitly be defined as substances used to add heat energy to a system through combustion or other processes. Fuels are mostly hydrocarbons like kerosene, diesel, petrol, alcohol, paraffin and butane and can also be in the form of individually free reactive molecular substances like hydrogen or chemical composites like natural gas, coal, wood.The gaseous state substances used as fuels such as hydrogen, and natural gas (94% methane and 6% ethane) are usually made into a cryogenic state as in liquefied at very low temperature because of their low boiling point. It can easily be asserted by anyone that t he only purpose that fuels have in jet engines is to add energy but little do they know that the purposes grows as the speed of the aircraft increases. For instance, Kerrebrock (2002) stated that supersonic aircrafts which attains very high stagnation temperature that can create destabilization to the airframe structure, engine component and organic substances like lubricants, uses its fuel as a coolant to this parts or components.The energy added by the fuel burned per unit mass of air flow is called the heating value of the fuel and it is a very crucial parameter to be defined before any combustion process analysis is done on a jet engine since it shows how complete the combustion process is through efficiency. The heating value can either be said to be higher or lower depending on if the water product of combustion is a vapour or a liquid. Since the combustion process in jet engine produces vaporised water, the lower heating value of the fuel is used. The most frequently used fue ls for jet engines are kerosene jet A1, A2, JP10 and many more but diesel can also be used. The disadvantages of these fuels are their inevitable emission of toxic substances that contribute to greenhouse effect and their risk of depletion.Accordingly, this has been the driving force for the use of alternative fuels such as cryogenic hydrogen and natural gas which is believed will reduce toxic emissions. Besides, hydrogen is a carbon-free energy carrier and possesses almost no risk of toxic emission since most of its combustion product will be water Chiesa and Laozza (2005). Chapter 3 Turbofan Jet Engine 3. 1. Introduction Between 1936 and the next decade when turbofan engines were invented, people showed little or no interest in them as they described them to be a complicated version of a turbojet engine. However, in 1956, the benefits of turbofan engines started to be noticed as major companies like Rolls-Royce and General Electric began manufacturing them.Since then, it is been o ne of the most used jet engine for commercial purposes because of its low fuel consumption and less noise production. In fact, it has been concluded to be the most reliable jet engine ever manufactured El –Sayed (2008). The turbofan jet engine gas generator unit comprises of a fan unit, compressor section, combustion chamber and turbine unit. Fundamentally, a turbofan jet engine operates as a result of the compressors pressuring air and supplying it afterwards for further processing. The majority of the pressurised air is bypassed around the core of the engine through a duct to be mixed or exhausted whereas the rest of it flows into the main engine core where it combusts with the fuel in the combustion chamber.The hot expanded gas products from the combustion process passes through the turbine thereby rotating the turbine as it leaves the engine. Consequently, the rotating turbine spins the engine spool which in turn rotates the other turbo machinery in the engine. This cause s the front fan to pressurise more and more air into the engine for the process to start all over again in continuous state. The turbofan engine is believed to be the perfect combination of the turboprop and turbojet engine and as a result, its advantages are usually compared to that of the turboprop and turbojet. In fact, Kerrebrock (1992) said that turbofan engine provides a better way of improving the propulsive efficiency of a basic turbojet.It is asserted that at low power setting, low altitude condition and low speed, the turbofan engine is more fuel efficient and has better performance than a turbojet engine. Unlike turboprop engine where vibration occurs in the propeller blades at relative low velocities, the fan in the turbofan engine can attain high relative velocities of Mach 0. 9 before vibration occurs. Also, since the fan in turbofan engines has many blades, it is more stable than the single propeller so even if the vibration velocity is reached, the vibration will not destabilize the airflow because the vibrations are almost negligible. Since the flow into the diffuser of the turbofan is usually subsonic, there very slim chances of shock waves being developed at the entrance. 3. 2. Classification of Turbofan EnginesThere are various types of turbofan engine ranging from high and low bypass ratio, afterburning and non-afterburning, mixed and unmixed flow with multi-spool, after fan and geared or ungeared. The classification of the various types of turbofan engines is shown below in figure 1. Nonetheless, the type of turbofan engine that would be used for the purpose of this dissertation is a forward fan two spool mixed flow turbofan engine. This type of turbofan engine was chosen because it is the compromise of a simple and complex turbofan engine. This is said because it comprises of almost all the classes of a turbofan which are low bypass ratio, forward fan with mixed flow, twin spool with ungeared fan.Moreover, because of the mixed flow intro duced, it produces additional thrust in the hot nozzle compared to the high bypass and it can also permit the addition of afterburner which produces a lot of thrust while consuming a lot of fuel which makes it suitable for military application which shows little worry on fuel consumption. In essence, carrying out a study on this type of turbofan engine will be of great relevance to the military air force sector especially if new research is discovered. TURBOFAN ENGINES Low Bypass Ratio Aft Fan Forward Fan Nonafterburning Afterburning High Bypass Ratio Geared Fan Single Spool Short Duct Ungeared Fan Two Spool Mixed Fan and Core Flow Unmixed Flow Long Duct Three SpoolFigure 1 Classification of Turbofan Jet Engines (El-sayed, 2008) 3. 3. Major Components of Turbofan Engine 3. 4. 1. Diffuser or Inlet Diffuser is the first component that air encounters as it flows into the engine. Basically, the purpose of a diffuser is to suck in air smoothly into the engine, reduce the velocity of the air, increase the static pressure of the air and finally, supply the air in a uniform flow to the compressor. Given the fact that overall performance of an engine is highly dependent on the pressure supplied to the burner, it is necessary to design a diffuser that incurs the minimum amount of pressure loss.To demonstrate this, Flack (2005) stated that if the diffuser incurs a large total pressure loss, the total pressure in the burner will be reduced by the compressor total pressure ratio time this loss. In other words, a small pressure drop in the diffuser can translate into a significant drop in the total pressure supplied to the burner. Another point taken into consideration when designing a diffuser is the angle because if the angle is too big, there will be tendency of eddy flow generation due to early separation. The major causes of pressure losses in the diffuser are as follows. First, losses due to generation of shock waves outside the diffuser and it majorly occur in super sonic diffusers.Secondly, the loss due to the unfavourable or adverse pressure gradient of the diffuser geometry which makes the flow separate a lot earlier and generates eddies. This separation causes a convergent area which makes the velocity not to be reduced by much. Due to the separation, the wall shear deteriorates the static pressure even further. Further analysis done by El-Sayed (2008), describes ways of accounting for this losses like using Fanno line flow and combined area and friction. Thermodynamic Process Equation In this analysis, the loss due to heat transfer is negligible so the process can be adiabatic. The initial kinetic energy is used to raise the static pressure p0 to the total pressure ? =pt2pt0 (inlet pressure recovery) efficiency ? d=IdealReal=ht2s-h0ht2-h0 assuming the gas is ideal and the specific heat at constant pressure is constant efficiency ? d=Tt2s-T0Tt2-T0 simplifying the equation given that ht0=ht2=ht2s and Tt2=Tt0and pt2s=pt2 TtT0=1+? -12M02 and T tT0=ptp0? -1? pt2p0=1+ ? d? -12M02 -1 3. 4. 2. Fan And Compressors Compressor is a very crucial component for the operation of an engine in the sense that it prepares the air for the combustion process in the burner. The main purpose of a compressor as the first rotating component is to use its rotating blades to add kinetic energy to the air and later translate it into total pressure increase.There are basically two types of compressors which are the centrifugal and the axial compressor. Firstly, centrifugal compressor as the name implies changes the direction of an axial airflow to a radial outflow of the air. It was the early compressors adapted in jet engines. It comprises of three main parts which are the impellers, the diffusers and the compressor manifold. The purpose of the impeller is to change the direction of the flow from axial to radial and at the same time increases its static pressure. The diffuser slows down the airflow and further increase the static pressure as it is supplied axially by the compressor manifold to the combustion chamber.The centrifugal compressor is advantageous because the cost of manufacturing it is low compared to axial compressor and as a result is suitable for small engines like turboshafts and turboprops. It is also advantageous because the pressure ratios at single stage are higher than that of the axial compressor. The centrifugal compressor has the tendency of attaining low flow rates and as a result is ideally suitable for helicopters and small aircrafts which require low flow rates. On the other hand, the centrifugal compressor cannot attain high pressure ratio and so it is not suitable when high peak efficiency is required. It incurs a lot of losses due to the change in direction. Secondly, an axial compressor is the most reliable type of compressor and is usually applied when higher pressure ratios of up to 40:1 are required.An axial compressor does not change the axial flow direction of the air but increases the total pressure. Indeed, an axial compressor comprises of three major components which are the rotor with blades, stator can and the inlet guide vane. A stage is a combination of a stator and a rotor. The assembly of the full rotor blade and stator can form the number of stages in a compressor and the greater the number of stages, the higher the total pressure ratio. In this arrangement, the air flows into the inlet guide vane and then into the rotor and stator assembly where compression starts. Also, the length of the rotor and stator reduces along the whole unit which signifies a reduction in volume which induces the increase in pressure.A fan or low pressure compressor is a type of axial compressor but the only differences are that the blades are longer, the total pressure ratio is lower than the typical compressor and the number of stages is usually 1 or 2. The main purpose of creating a fan is to compress more air and to create a bypass air which can be used to generate addition thrust or used for mixing process. Fan Equation Process Given that, isentropic efficiency ? fan= Ideal CycleActual cycle=ht3s-ht2ht3-ht2 Since the specific heat is constant, the equation deduces to ? fan=Tt3s-Tt2Tt3-Tt2 Simplifying the equation whenpt3s=pt3, Tt3sTt2=pt3pt2? -1? , ? fan=pt3pt2 and ? fan=Tt3Tt2 ? fan=? fan? -1? -1? fan-1 Bypass Ratio=msma where ms is the bypass flow rate and ma is the engine core flow rate.For the high pressure compressor, the equations remain the same as that of the fan except the changes in station numbering and the bypass ratio. 3. 4. 3. Combustion Chamber/ Burner The combustion chamber as the Brayton cycle implies is the only source of heat energy addition to the system. Accordingly, the combustion chamber causes very significant increase in the temperature of the air which results in the air gaining enormous internal energy. This energy gained is extracted to be used to power the turbine while the rest is used to create highly accelerated gases from the nozzle. There are three types of combustor namely; the can combustor, the annular combustor and the cannular combustor.The main considerations when designing a combustion chamber is to ensure that the combustion process is complete with no fuel waste, the combustor should have long life materials because any failure can lead to engine explosion. The other consideration is that the air must be heated enough above the ignition fuel temperature in order to ensure stoichiometric combustion. Equations of the Combustion Chamber In the real process of the combustor, total and static pressure drops and the temperature also drop. The major causes of pressure losses are the high level of irreversibility or non-isentropic process and viscous effects in the burner. The burner pressure ratio ? =pt5pt4Burner temperature ratio ? b=Tt5Tt4 Since no work is done only heat transfer, the efficiency of the burner is analysed using the heating value NCV of the fuel used. Thus, efficiency ? b=hea t addedHeating value of fuel=ma+mfht5-maht4NCVmf Given that f=mfma, ? b= 1+fht5- ht4NCVf Equivalence Ratio of combustion It is the ratio of the actual fuel to air ratio of the combustion process to the stoichiometric fuel to air ratio. This ratio produces a means of classifying the combustion process to show whether it is a lean, rich or stoichiometric combustion. The mathematical expression for this is as shown below ? =Actual FARStiochiometric FAR 1 Rich combustion process 3. 4. 4. Turbine Turbine can simply be said to be the antonym of a compressor. In response, a turbine extracts molecular kinetic energy from the air and uses it to drive the turbo machineries which results in the pressure and temperature of the air to drop. If truth be told, Flack (2005) asserted that the turbine uses 70% to 80% of the total energy gained by the air in the combustion chamber to drive the turbo machineries while the remaining 20% to 30% is used to generate thrust in the nozzle.Since the geometry of a turbine have favourable pressure gradient unlike the compressor which is adverse, the efficiency of the turbine is usually very high. Since the turbine is the opposite of the compressor, it has exactly the same configuration of rotor and stator but the volume increase across it which induces the pressure drop. One major problem faced when design a turbine is the deterioration of the blades due to high inlet temperature from the combustion chamber. Based on this, (Song et al. 2002) demonstrated that General Electric uses about 16. 8% of the compressor air to cool the turbine blades of GE 7f engine. Turbine Equation Analysis Given that, Turbine efficiency ? T=ActualIdeal=ht6-ht5ht6s-ht5 T=Tt6-Tt5Tt6s-Tt5 Simplifying the equation given that pt6s=pt6 Tt6sTt5=pt6pt5? -1? ?T=pt6pt5 ? T=Tt6Tt5 ?T=? T-1? T? -1? -1 3. 4. 5. Exhaust Nozzle The nozzle is the final component of the jet engine that the air passes through. The main purposes of the nozzle is to add extra acceleration to the h igh velocity exiting air, reduces its total pressure to that of ambient condition and finally generate sufficient thrust. There are two conditions that occur in the exit of the nozzle depending on the ambient pressure. The first condition is termed under-expansion which occurs when the ambient pressure is less than the exit pressure of the gases.The result of this is that the exit velocity will be lower than it normally is and this makes the momentum component of thrust to be lower than ideal. On the other hand, it will create a positive thrust component for the pressure terms. The second case termed as overexpansion which occurs when the ambient pressure is greater than the exit pressure of the gases. Consequentially, the opposite of what happens in the under-expansion condition occurs where the pressure term is lower and the momentum is higher. Nozzle efficiency ? n=ActualIdeal=ht8-h9ht8-h9s=Tt8-T9Tt8-T9s for constant specific heat Using the steady state energy equation and balanc ing it out, U9=2ht8-h9 . When specific heat is constant U9=2cpTt8-T9 p9pt8=T9sTt8? -1? T9Tt8=11+? -12M92 p9pt8=11+? -12M92-1+ ? n ? n 3. 4.Thermodynamic Process and Cycle of Twin Spool Mixed Flow Turbofan Engine Before any explanation is done from Figure 2, the blue arrows represent the incoming air into the diffuser and the red represent the air flow into the core of the engine while the black arrow represent the bypass air flow through the fan. Finally, the brown arrow represents the air flow after the bypass air and the core air flow have mixed. Based on the arrangement of the turbofan engine in figure 2, it can be seen that air at ambient condition is sucked into the diffuser where the air velocity is reduced and some of its kinetic energy is used to increase the static pressure to the total pressure. The air exiting the diffuser enters the fan or low pressure compressor where it is compressed. Indeed, the molecules of the air gains kinetic and internal energy by colliding rapid ly with one another and as a result increase the enthalpy and static pressure.Also, in the fan, some of the compressed air is bypassed through a duct to be used for the mixing process later while the rest of the air enters into the high pressure compressor of the engine core. In the high pressure compressor, the air is further compressed where the enthalpy and pressure increases as it is released into the combustion chamber. Also, in the high pressure compressor, some of the air mass flow rate is bled out to be used to cool the turbine blades and for air conditioning in the aircraft. In the combustion chamber, the incoming fuel reacts with the air in an oxidation process at constant pressure where the by-product gases gain molecular kinetic energy thereby increasing the enthalpy.This high temperature gases escapes into the high pressure turbine where it is expanded and the gases lose some of their kinetic molecular energy as it enthalpy and static pressure reduces. In other words, i t can be said that the molecular kinetic energy of the gases is being converted to mechanical work which is used to power the high pressure spool. Consequently, the gases enters into the low pressure turbine where it is further expanded to a lower pressure and enthalpy as their molecular kinetic energy is converted to mechanical work to power the low pressure spool. These gases escaping from the low pressure turbine enters the mixing zone or mixer after it has lost most of its total enthalpy and mixes with the bypassed cold air from the duct to further reduce its enthalpy as that of the cold air increases.In other words, the cold air absorbs some of the heat energy from the hot gases until they both attain equilibrium enthalpy. The mixture of the cold air and hot gases both escape at the same equilibrium enthalpy and pressure through the nozzle where their velocity is increased and the pressure is reduced considerably to that of the ambient condition. Furthermore, the exhausted high velocity gases is used to produced thrust for propulsion according to Newton’s third law of motion (In every action, there is equal and opposite reaction). 2 4. 5 6 4 13 0 HPC DIFFUSER FAN/LPC HPT LPT NOZZLE COMBUSTION CHAMBER 2. 5 3 5 8 16 BYPASS DUCT HP Spool LP Spool MIXING ZONEFigure 2 Layout of a Forward Fan Twin Spool Mixed Flow Turbofan Engine P0 P3 P4. 5 P5 P8 P6 P2. 5 P2 P13 P4 ENTROPY (S)(kJ/kg) TEMPERATURE (K) Figure 3 T-S Diagrams for the Forward Fan Twin Spool Mixed Flow Turbofan Engine Chapter 4 Mathematical and Gas Turb 11 Modelling of the Engine 4. 1. Station Numbering and Assumptions Station numbering is a very crucial step that has to be taken when analysis of any thermodynamic system involving many processes is to be done. Moreover, station numbering contributes immensely to showing how the properties of one process relate to another and how the interaction between these processes derives the functional relationship of the thermodynamic system.Returning to the work in hand, the station numbering system that has been adopted for this work on a JT8D-15A turbofan engine is in accordance with the Aerospace Recommended Practice (ARP) and it is shown in figure 2. Assumptions The following assumption were made based on Mattingly (2002) and Kurzke (2007) in order to perform the modelling as listed below * The air flow through the engine is assumed to be steady and one dimensional * The fan and the low pressure Compressor are driven by the low pressure turbine * The overall engine is assumed to have no bleeds in mass flow or power off-take in turbine. * The nozzle of the engine is choked which means the exit pressure will be greater than the ambient pressure. The air is assumed to act as a half ideal gas where the specific heat and ratio is dependent on temperature only. * The areas of each station of the engine is assumed to be constant 4. 2. Design Point Cycle Analysis of the Turbofan Engine The off-design or performance cycle analysis cann ot be done without the design point cycle being defined. The design point cycle in this analysis is obtained using exactly the same data used in the actual test analysis for a JT8D-15A turbofan engine operating at sea level with maximum take-off thrust as shown in (â€Å"JT8D Typical Temperature and Pressure†) and (â€Å"ICAO†). Some of the input parameters such as the isentropic efficiencies and pressure ratios from the actual test data had to be calculated.Since not all the input parameters were given from the actual test data, some of the parameters like inlet corrected mass flow rate, diffuser pressure ratio and efficiency; mechanical spool efficiency had to be guessed in order to complete the analysis and the data are represented below in Table 1. With all the Input Parameter being specified as shown in table 1, the design point cycle simulation of the JT8D-15A turbofan Engine using the Gas Turb 11 software can then be performed. All the steps taken to model the m ixed flow turbofan engine on Gas Turb 11 is clearly represented in the algorithm shown in figure 3 below. COMPONENT| INPUT PARAMETER| | DIFFUSER| Pressure Ratio (? d)| 1| | Inlet Corrected Mass Flow Rate (mc2)| 138. 618 kg/s| FAN| Pressure Ratio (? fan)| 2. 054| | Isentropic Efficiency (? fan)| 0. 78| | Bypass Ratio (? )| 1. 08| Low Pressure Compressor (LPC)| Pressure Ratio (? LPC)| 4. 7| | Isentropic Efficiency (? LPC)| 0. 88| | Nominal Low Pressure Shaft Speed (NLP)| 8160RPM| High Pressure Compressor (HPC)| Pressure Ratio (? HPC)| 3. 77| | Isentropic Efficiency (? HPC)| 0. 864| | Nominal Low Pressure Shaft Speed (NHP)| 11420RPM| Combustion Chamber (cc)| Pressure Ratio (? CC)| 0. 934| | Isentropic Efficiency (? CC)| 0. 99| | Burner Exit Temperature (TIT)| 1277. 15K| High Pressure Turbine (HPT)| Isentropic Efficiency (? HPT)| 0. 9| | HP Spool Mechanical efficiency (? m)| 1| Low Pressure Turbine (LPT)| Isentropic Efficiency (? LPT)| 0. 91| | LP Spool Mechanical efficiency (? m)| 1| T able 1 Input Parameters for the Design Point Cycle Simulation STARTSpecify all the input data gotten from the actual test data as shown in Table 1 Run the Gasturb 11 software and select mixed flow turbofan from the drag down Tab list. Set the scope to ‘More’, set the Calculation Mode as Design and click ‘Run’ Choose the Units to either Imperial or SI and Select the type of fuel from to drop down list to Kerosene, Natural Gas or Hydrogen Estimate the inlet Corrected mc2 Mass Flow rate to the FAN/LPC Choose ‘Single Cycle’ for ‘Select a Task ‘Option and click ‘Run’ Check if the Thrust, SFC, ? HPT, ? LPT and EPR are within (0-10) % of the actual test Experiment END YES NO Figure 4 Design Point Cycle Simulation Algorithm Using Gas Turb 11 Verification of the Design Point simulation ResultsSince not all the input parameters were specified in the actual test data and some of them had to be guessed, it is without any doubt that errors are bound to generate in the simulation results using the Gas Turb 11 software. In order to ensure that the errors accumulated in the simulation were within range, the major output parameters obtained such as net thrust, fuel flow rate, Engine exit pressure ratio, etc were compared to the actual test data as shown in Table 2 and the error range was calculated to be between 0. 25% to 8. 5% which is within an acceptable range. PARAMETERS| ACTUAL TEST DATA| SIMULATED DATA USING GASTURB 11| Net Thrust| 69307. 74| 69320| Engine Exit Pressure Ratio P8P0| 2. 09| 2. 167|Burner Fuel Flow| 1. 100843| 1. 09781| HPT pressure Ratio (? HPT)| 0. 415| 0. 449| LPT Pressure Ratio (? LPT)| 0. 3294| 0. 3514| HPT temperature Ratio (? HPT)| 0. 8097| 0. 8435| LPT temperature Ratio (? LPT)| 0. 7718| 0. 793| Table 2 Comparison Table for the Actual Test Data and Simulated Data Using GasTurb 11 4. 3. Off-Design Point Cycle Simulation of the Turbofan Engine The off-design or performance cycle simulatio n takes into account the concept of module matching of each component through performance maps. This cycle analysis enables the determination of different operating point of the engine at a given design point of the engine.Considering the work in hand, the design point have been defined and verified for the JT8D-15A turbofan engine operating at sea level with maximum take-off thrust which means that different operating points of the engine can be defined with the concept of off-design module matching of the engine. Indeed, the off-design operating point that was considered for the parametric analysis in this work was 30,000ft at M0 0. 8 for the turbofan engine. The off-design modelling of the JT8D-15A engine for the operating point of 30,000ft at M0 0. 8 based on the reference design point defined earlier is clearly demonstrated as follows. The off-design performance cycle simulation may contain some errors because of the component performance maps that were used for the simulation. 4. 3. 1. Module/Component Matching This process only applies to the off-design performance cycle point of the engine.It can simply be defined as the act of synchronising each component of a jet engine to coexist as a unit in order to derive the overall performance characteristics of the jet engine. Component matching involves the process closely studying the ramifications of the actual jet engine overall performance behaviour on the components major characteristics such as pressure ratio, temperature ratio, efficiency and spool speed. This process introduces the concept of empirically determined component performance maps that establishes the relationship between the thermodynamic properties and the geometry of the jet engine itself. 4. 3. 2. Off-Design Component Modelling Diffuser The diffuser was assumed to be adiabatic and the pressure ratio ? d=1 The Isentropic Efficiency was assumed to be 1 For Sea Level,Pamb=101325pa , Tamb=288. 15K For 30,000ft and M0 0. 8, Tamb=288. 15-0. 0 065? 9144 =288. 15-59. 436 =228. 71K Pamb=101325? Tamb288. 155. 2561 =30. 09kpa Tt1=228. 71? 1+? -12M02 =228. 71? 1+1. 4-12? 0. 82 =258K pt1p0=1+ ? d? -12M02 -1 pt1=30. 09? 1+ 1? 1. 4-120. 821. 41. 4-1 pt1=45. 8674kPa pt1=pt2 Tt1=Tt2 Fan and Low Pressure Compressor The inlet corrected mass flow rate is estimated as 138. 618kg/s , As for the off design simulation using the component performance maps for the altitude of 30000ft and Mach no. 0. 8, the actual spool speeds and inlet mass flow rate are calculated based on the estimated inlet corrected mass flow rate as shown below.Low and High pressure spool mechanical efficiency is assumed to be=1 HP spool Speed=11420RPM, LP spool Speed=8160RPM m2=Pt2PSTD? mc2Tt2TSTD =45. 878101. 325? 138. 618258288. 15 Actual Mass flow rate m2=66. 3323kg/s N=Tt2TSTD? NcLP=228. 71288. 15? 8160=7722 RPM The calculated actual mass flow rate and spool speed were used to evaluation the isentropic efficiency and the pressure ratio of the LPC for that operatin g condition from the compressor performance map. Figure 5 Example of a Compressor Performance Map/Curve The diagram above in figure 4 depicts a typical compressor performance map that was used for the off-design point analysis in this work.It can be seen that the x-axis represents the inlet corrected mass flow rate mc2 into the compressor, the y-axis represents the compressor pressure, the red contour lines represents the isentropic efficiencies and the black curved lines represent the relative corrected spool speed. To add to that, the red dash line that ends the speed lines and efficiency lines represent the surge margin which is also known as the stall line that must be avoided since the flow will become unstable in that region. In this work, the inlet corrected mass flow rate and spool speed were calculated which were interpolated on the performance map to obtain the pressure ratio and the isentropic efficiency.For instance, the yellow dot on the map represents a design point tr aced for a given pressure ratio, High Pressure Compressor The inlet corrected mass flow rate into the HPC mc2. 5=mc21+? mc2. 5=138. 6182. 08=66. 64kgs m2. 5=Pt2. 5PSTD? mc2. 5Tt2. 5TSTD N=Tt2. 5TSTD? NcHP The same equation used for the LPC is used to calculate the actual mass flow rate and spool speed which is used to evaluate the isentropic efficiency and pressure ratio when it is operating at an altitude of 30000ft at M0 =0. 8. Verification of the off-design modelling for 30000ft at Mo 0. 8 In order to verify the simulation result gotten for the operational design point of 30000ft at M0 0. , the actual test data results gotten from Mattingly, Heiser and Pratt (2002) for the same operating condition was compared. Due to the difficulties in obtaining a lot of output parameters for this operating point, the result will be verified with only the net thrust generated and the specific fuel consumption. Indeed, the error accumulated was 1. 71% for the net thrust and 0. 83% for the specif ic fuel consumption. PARAMETERS| ACTUAL TEST DATA| SIMULATED DATA USING GASTURB 11| Net Thrust (lb)| 4920| 4836| Specific Fuel Consumption(lb/lbh)| 0. 779| 0. 7855| Table 3 Comparison Table for the Actual Test Data and Simulated Off-design Data Using GasTurb 11 Chapter 5Methodology, Results and Discussions Given that the design point of the JT8D-15A turbofan engine at sea level has been obtained and verified with the actual test data, the operating point of 30000ft at M0 0. 8 was simulated and obtained which now served as the design point for the analysis in this work. Moreover, the procedure taken to define this design point of 30000ft at M0 0. 8 of the JT8D-15A turbofan engine has been clearly stated earlier which gives the permission to conduct the parametric cycle study of the turbofan engine. The parametric cycle studies were done for three different cases for the operational design point of 30000ft at M0 0. of the JT8D-15A turbofan engine as explained as follows. 1. The first parametric analysis case 1 aim to create an understanding of the effects of varying major design parameters on the performance parameters of the turbofan engine when some of the design choices are kept constant. In other words, the bypass ratio and thermal limit parameter (turbine inlet temperature) were varied when the design choices such as the compressor pressure ratio, fan pressure ratio and isentropic efficiencies were kept constant in order to investigate their effects on the performance parameters such as the net thrust, specific fuel consumption, propulsive efficiency, thermal efficiency, and fuel-air-ratio.Much interest is shown nowadays in using alternative fuels like hydrogen and Natural gas in efforts to reduce the cancer known as pollution and the risk of depletion of energy resources. Based on this, conducting a research that focuses of comparing different fuels consumption rate, their risk of pollution and their contribution to the performance of the engine will be re ally valuable. Based on this, a parametric analysis had to be done on the JT8D-15A turbofan engine using three different fuels which are the design point fuel kerosene, hydrogen and natural gas. Since the original design point of the JT8D-15A turbofan was obtained using kerosene fuel, the design points of using hydrogen and natural gas was obtained using the same design choices as that of kerosene.Now that the design points of the JT8D-15A turbofan engine had been defined when using the three different fuels, it had given a go ahead to perform whatever parametric cycle studies of the turbofan engine using the three fuels. In order to compare the performance characteristics of the turbofan engine when it is using the three different fuels, different approaches had to be devised to compare them effectively on a rational basis which defines the last two parametric analysis cases as follows. 2. The second case of parametric analysis was that the fuel flow rate would be kept constant for the three fuels that would be used as the bypass ratio is varied with design choices remaining the same. 3.The third case of study was to make the energy supply into the combustion chamber of the turbofan engine the sa

Lands’ End Case Study Essay

1. A) Lands’ End’s buying center most likely consists of Assurance Personnel and upper management because Lands’ End selects long term suppliers that will likely ha a significant effect on the future of the business and that decision can’t be left to inexperience members or members without authority or power in the company. B) Users would most likely be the package handling department since the products are simply bought and resold by Lands’ End and not actually used to produce. Influencers would most likely be the agents that search for the fabrics and materials to buy. Buyers would likely be management teams as they need to form long term contracts that would require someone of authority in the company. Deciders would most likely be the upper management that has the actual authority in the company to sign long term contracts. Gatekeeprs would most likely be the assurance personnel mentioned in the reading that they go to suppliers to gather the information. 2. A) Lands’ End does not need to go to problem recognition because they are constantly searching for new and better suppliers. Thus they would skip to Information search in which they scout the best possible suppliers around the world that are likely to produce high quality items or materials. Next they would use Alternative evaluation to see if there is a company that gives the same product at either a higher quality or better price. The purchasing decision would be made by the managers that handle new contracts. Then finally they would use Postpurchase behavior to consider the contracts they have made and consider their value and change them if need be. B) Price may not be necessary as the purchasers are customers of Lands’ End and they would decide if the item is a fair price. Ability to meet quality specifications would be very important as Lands’ End claims that they seek the highest quality items to sell. Ability to meet required delivery schedules is also very important as they need a guarantee that the items they will be selling will get to their customers in a timely matter. Technical capability is also important as Lands’ End is attempting to keep up with the technological advances in the future so they are not left behind. Warranties are necessary as Lands’ End claims they will return any item no matter what. Past performance on previous contracts is necessary as they buy by contracts and have long term suppliers. 3. New Buy- Lands’ End does not face new buy regularly as they generally focus and reselling, however a new buy for Lands’ End may be buying new delivery trucks from a truck building company. Or they may need storage thus they buy land and construct storage facilities on it. Straight Rebuy- This is the most common case in Lands’ End as they rebuy as they may just be buying more of an item from an existing supplier for items that are sold regularly such as materials and fabrics or duffle bags and such that they need to have in stock to continue selling. Modified rebuy- in this case, Lands’ End upper management would be involved in buying new contracts with suppliers.