High Bypass Ratio Turbofan

High Bypass Ratio Turbofan INTRODUCTION Turbofan engines are basically turbojet engines which are provided with a large fan. These were developed to combine some of the best features of both turbojet and turboprop engines. The major advantage of turbofan engines are that it provides a better fuel efficiency. Most of the airliners today use turbofan engines. (Aviation History online museum c. 2008) Bypass ratio: It is defined as the mass flow rate of air bypassing the combustion chamber to the mass flow rate of air passing through the core of the engine. Figure I: Schematic diagram of Low and High Bypass Turbo fan (Yoon J. 2001) Turbo fan engines may be sub-categorized based on the bypass ratio as:- Low-bypass ratio turbofan A small amount of air bypasses the combustion chamber, through the fan ducts and the fan is of very small diameter. These are compact in nature. High-bypass ratio turbofan The fan in a high-bypass turbofan is much larger to force a large volume of air through the ducts. These can generate more thrust, are better in fuel efficiency and are less noisy than the other engines. (Yoon J. 2001) The three major companies to introduce turbofan engines were General Electric, Rolls Royce and Pratt Whitney. All of these companies introduced there version of turbofan engine one after the other. The first high bypass turbofan engine was developed by general electric the GE-T39 in 1964; this was developed in response to the desire of the United States Air Force. (General Electric Co. 2008) Figure III: Pratt Whitney Turbofan engine (Serra 2008) Currently the turbofan engine market is dominated by General Electric, Rolls-Royce plc and Pratt Whitney. GE Aircraft Engines, a part of General Electric, has the largest share of turbofan engine market. (Opentia n.d.) The major disadvantages of these engines is its complexity to manufacture as it contains a multiple shaft system, the large diameter of the engine and a requirement to contain such heavy front fan blades which make it a bulky machine. (WordIQ n.d.) FUNCTIONS OF THE FRONT FAN The front fan or the inlet cowl plays a multi-functional role in the running of a turbofan engine. These are comparatively larger in size than the other parts of the engine. This variation in size facilitates in the creation of a bypass air flow. The bypass air flow is defined as the air entering the engine but not flowing through the compression stages, it flows out of the engine as a bypass to the engine core. This bypass air flow is designed to develop an additional thrust as it passes from the outer surface of the engine core. This bypass air not only generates the additional thrust but helps in lowering the surface temperature of various parts in the engine as it acts as coolant acting on the external surface engine body. It also helps in reducing the noise created by the engine as it suppresses the exhaust noise. Apart from the above functions, the fan blades play a major role in reducing the speed of the air entering the engine. For better fuel efficiency, the air entering the combustion chamber must be highly compressed (Compression ratio around 15). For this the air must pass through the compression stages at sub sonic speeds. The front fan blades act as an obstruction to the incoming air and reduce its speed. Also, the curvature provided on each fan blade direct the air evenly across the inlet of the engine, increasing efficiency. The air is guided in a manner to provide a radial inlet to the compressor. (Benson Jul 29 2008) IN SERVICE CONDITIONS The front fan blades are subjected to various conditions which they should be able to sustain in order for proper functioning of the engine. The may be classified as:- Temperature: The fan blades are subjected to a temperature range of  ± 60oC. The blade material should remain stable in this range of temperature. Figure III: Turbofan engine temperature and pressure distribution by NASA Pressure: The pressure range for fan blades can be classified between 0.192atm (@40,000ft) to 1atm (@sea level). Stresses: The maximum stress concentration can be observed at the root of the blade. Maximum tensile stresses and laminar shear stress occur at the root of the blade. Maximum tensile stress concentrations, under steady state conditions, are concentrated about the undercut radius on either side of the shear slot key. This is due to the centrifugal loads incurred while the blades are rotating. Icing: Ice may accumulate on the fan blades and on the fan rotor when flying under high humidity and temperature around freezing point. The ice on the surface of the fan blades disturbs the airflow and generates vortices. These vortices can lead to an unstable compressor operation. They facilitate stall and surge. This ice also induces an imbalance which leads to vibrations. Detached ice pieces from this can even create a risk for foreign object damage when they hit the fan rotor and components behind the fan. (Diesinger 2008: 179) OPERATIONAL REQUIREMENTS The various operational requirements of the material for the front fan blades of a turbofan engines can be summarized as a material with:- Fatigue Resistance Front fan blades undergo cyclic fatigue loads. It has been observed that the fatigue failure has often been a reason for initiation of fatigue crack on the blade surface. Fatigue failure (No. of cycles) à ¢Ãƒâ€¹Ã¢â‚¬  Ã‚  1/ Level of Stress Corrosion Resistant In rainy or overcast conditions, the fan blades must be corrosion resistant to avoid rusting on the blades. The rusting can cause abrasions on its surface which may result as an obstruction in the motion of flowing air. Light in Weight As discussed earlier, the turbofans are one of the heaviest turbine engines and the front fan blades add quite a lot to the weight of the engine due to its size. Hence, it is desirable to have a material which is effectively light in weight. Vibrations The material should be able to withstand vibrations produced in the engine due to the high speed incoming air. High frequency vibrations can cause de-stabilization to the aircraft. Blades The front fan blades must undergo super plastic forming at the tip to retain a blade angle. The blades are provided with a double circular arc blade profile for subsonic compression of the incoming air. After casting the blades should undergo annealing at recrystallization temperature for the removal of residual stresses that may have induced during the forming process. (Babu 2009:110-111) Blades should have sharp edges to be able to crush any particle that comes in way of its operation. This is to avoid any foreign body from entering the turbine and damaging the engine. High stiffness The blade material should have a high stiffness so as to avoid any deformation on its surface in case an object strikes it while in operation. Resistance to cracks The materials of the blades should be resistant to cracks as even on crack initiation the material should resist the developing of the crack. In case if the material is not crack resistant then it might result in quick developing of crack resulting into failure of the fan blades, which can lead to further engine trouble. MATERIAL CHARACTERISTICS Various material characteristics that need to be considered while selecting the material for the front fan blades of a turbofan engine are:- High tensile strength and fatigue strength. Low density. Resistance to corrosion. Sustain temperature range  ±60 oC. High fracture toughness. Damping capability. Hardness: 327-339 HV. (ATSB 2001:15) Avoid any residual stresses as they can lead to cracks. Avoid ice formation by providing sleek surface to the fan blades. (centrifugal action) SUMMARY From the above information we can summarize that the front fan blade plays a very crucial role in turbofan engines. These help in achieving better fuel consumption and hence are of great importance to the turbofan engine. Material selection for the blades should be done carefully considering the requirements such as High endurance Limit, Low density, removal of residual stresses, High fracture toughness, High damping Capability and resistance to corrosion.

Homosexuality Is Not a Psychological Disorder

In the past, homosexuality was considered to be a psychological disorder, up until the APA removed it from its list of mental illnesses. This was due to the fact that homosexuality causes no form of impairment on the individual’s judgment, stability, reliability, or general social and or vocational abilities. This decision made over 30 years ago, has caused a lot of criticism, many believe that the APA’s decision was made due to the amount of influence that the homosexual activism and not according to the scientific data that was collected. There are two possible sides to this assumption about whether or not homosexuality is and should be considered a psychological disorder. According to an article published in the Scientific Controversies: Case Studies in the Resolution and Closure of Disputes in Science and Technology, edited by H. Tristam Engelhardt Jr. , and Arthur Caplan, Cambridge U. Press, 1987. Dr. Irving Bieber, described the attempts for psychiatry to adopt a new perspective regarding sexual normality. During this time the psychiatric professions were moving from the established psychoanalytic theories based on unconscious motivations, in which they claimed that if you cannot visible see distress, dysfunction, and or disability among psychological conditions then it isn’t seen as being disordered. Dr. Bieber while attempting to describe the difficulty of classifying homosexuality concluded that homosexuality was not a normal sexual adaptation. When the APA adapted a new set of criteria for defining psychological disorders, Bieber argued that psychopathology, which could possible show signs of distress, social functioning, and the ability to work effectively could be present in psychopathology. Many others agree that homosexuality is indeed a psychological disorder, and argue that it actually stems from unhappiness in the family that leads to more unhappiness throughout their lives. Many individuals refer to it not being God’s will thus it is constituted as abnormal, thus it is a mental disorder. On the other hand, homosexuality is defined as being attracted to or aroused by individuals of the same sex. Homosexuality is considered not to be a mental disorder due to the fact that their actions don’t impair their ability to function either at work or in their personal lives. Homosexuality doesn’t have an effect on their ability to function or hinder their ability to handle their responsibilities at work, nor does it prevent them from being able to create and maintain long lasting and healthy personal relationships. Homosexuals are just as psychologically healthy as any heterosexual is. The infamous Sigmund Freud and Havelock Ellis adopted a more accepting stance regarding homosexuality. Ellis in 1901, argued that homosexuality was inborn thus it wasn’t immoral, that it wasn’t truly a disease, and many homosexuals had contributed outstandingly in society. Sigmund Freud had another stance about homosexuality, and that was that he felt that all human beings were innately bisexual, and those they actually become either homosexual or heterosexual as the result of their past experiences with their parents and others. Either way Freud agreed with Ellis that homosexuality shouldn’t be viewed as a form of pathology. In a very famous letter that Freud wrote to a mother back in 1935, he stated that homosexuality cannot be considered as an illness, and that he considered it to be a variation of sexual function produced by certain area of sexual development. He then went on to note that many highly respectable figures throughout both ancient and modern times have been homosexual including Plato and Leonardo Da Vinci. In 1957, psychologist Evelyn Hooker conducted a study in which she asked if homosexuals and heterosexuals differed in their psychological adjustments. She then recruited a group of homosexuals who were considered to be functioning normally in society. Then she employed a procedure asking experts to rate the adjustment among the men without previously knowing their sexual orientation. Her study concluded that homosexuality was in no way a clinical entity nor was it associated with psychopathology. In conclusion, Homosexuality is not a psychological disorder. The APA’s board of directors chose to remove it from the DSM- IV- TR, due to the great deal of data collected, along with the changing among social norms and the development of homosexual and gay activist organizations. We have to also take into consideration that by labeling homosexuality we quickly are exhibiting discrimination against those individuals. There is nothing in regards to homosexuality that would cause a great deal of distress and or cause them impairment in their ability to function normally. Their sexual preference shouldn’t be considered as a being a psychological disorder. The fact that an individual prefers the same gender doesn’t mean at all that they have a mental illness, it doesn’t affect their ability to be outstanding members in society, nor does it directly hinder their ability to unction. Psychological disorders are defined as the individuals behavior or thoughts that impacts their life altogether and as causing a significant amount of distress for the individual. Homosexuality does not mean distress for these individuals, it is merely preference. If homosexuality was considered to be a psychological disorder, we take away the right to privacy after a ll sexuality is private; we would also be taking away the right to happiness, the right for them to make their own choices, the right for them to be them. How can the choice that they choose to make in their private life that doesn’t have any effect on their ability to function nor does it cause distress to them be considered a psychological disorder? They are not seen as being harmful to themselves or others by living their life the way that they choose to. Their sexual preference has no effect on how their psychological functioning, thus homosexuality is not a psychological disorder. It doesn’t affect their ability to think, feel, act, and the ability for them to become functioning members of society. Reference www.lifesitenews.com/ldn/2006/jun/06062008.html

Education in Our lives Essay

What do you think education means to society? What does education mean? An education is commonly defined as a process of learning and obtaining knowledge. Many problems can occur that can prevent an education to people such as religion, culture, tradition, income and where you live or come from. Those can create different assumptions of someone’s educational background. The education for society can be different, due to the fact that various types of education plus learning methods and assumptions affect me and others in many different ways. An important key role in my life by far is education, because so far it has given me a different perspective of life. A well-known Greek Philosopher named Plato once said that the direction in which education starts a man will determine his future in life. He literally means the type of education we chose to follow or have leads to us becoming that. So far in my journey of life it has opened and shown my eyes to a lot to see in this world. Education has given me the chance to learn and discover new things around me; in addition it has taught me to believe about life. Education has made me who I am today, and will have a huge impact in my future to come, because it will determine how I will live. It has given me a picture or sense on what I can achieve and do in life. My education started at a very young age, just like most people start theirs. My first mentors and teachers were not from elementary school, but they were my own people that raised me from home. The education I received to this day has made me a better decision maker about life’s big questions. Nelson Mandela best said that education is the most powerful weapon which can be used to change the world. What Nelson Mandela is trying to mean is that education is the answer to move forward in life. I totally agree with Mandela on that. In some places, people don’t see education has being important or don’t care about obtaining a great educational knowledge. An example could be a high school graduate not wanting to extend his education to get a degree from college or a university, which can bring good things in his life. According to former Secretary of Education of the U.S William Bennett he states American 12th graders rank 19th out of 21 industrialized countries in mathematics achievement and 16th out of 21 nations in science. Our advanced physics students rank last. There are various types of  education and learning, and each affects me and other people differently. Location plays a big role in the type of education we are getting or will get. For example, a person living in a 3rd world country isn’t likely going to receive the same education as let’s say someone in the United States. Another example could be if a student goes to school at an urban city like New York and other student was to go at a small town with few people living there, their education plus learning would be different. The school teachers also affect many students differently. Many people don’t realize that all teachers do not teach or explain something the same way, they teach differently. Let’s say a student goes to their local school for about five years, then moves across the country and attends a school there, his educational learning would be affected. According to Jenifer Steele a researcher for Rand Education she mentions in an article titled â€Å"Teacher Matter: Understanding Teachers’ Impact on Student Achievement† that when it comes to student performance on reading and mathematical tests, a school teacher is estimated to have two to three times the impact of any other school resource. She also states that effective teachers are best identified by their performance, not by their background or experience. A student’s own will to learn, will also deeply affect his or hers education. If a student has the opportunity to go to school or even college, but doesn’t have the will to learn won’t have a good educational background. On the other hand, a student also has the opportunity to go to school/college, plus has the will to learn will have a better education than the student who does not. There are many factors of this, but a major one takes place in the classroom. Many students dislike school, and some may even drop out of it. Everyone’s educational background is different. Everyone has different assumptions that tell us or inform about our educational or learning experiences. Some assumptions tell us good about education some tell us bad things. For example, an assumption from the University of North Carolina in Charlotte about educational learning is that people at all different ages have the potential to learn, with some learning quicker than others. Age may or may not affect a person’s reaction of learning, and individuals vary in way they like to learn. This could be true, but at the same time it could have potentially to be false as well.  Another example, in the classroom the teacher facilitates learning by incorporating students’ experience, observation of others, and personal ideal and feelings. Exposure to many different behavior models and attitudes help students to make actions and ideas that will help in meeting their own educational goals. This is labeled an assumption because some believe in this way of teaching students, while some teachers do not. We all have different kinds of assumption about school education; my assumption of education is if students put more effort in addition focus more on academics, and less time on other things then they will succeed in getting an education. My assumptions about education and learning do in fact compare and contrast to what I am currently experiencing in college. An example of an assumption is that students do not need much guidance from the instructor, which was mentioned in the Seven Deadly Assumptions about Students article from Point Loma Nazarene University. My assumption that contrasts their assumption is that I truly believe in that some students may need lots help or assistance from the instructor. My assumption compares to what I’m experiencing in college, due to the fact that I get a lot of help from my instructors and tutors. A second assumption from the article is that students will put together the content that they are expected to learn, by themselves after class. I do not agree with this because some students may not know how to start applying it. When I need to learn something in class I make sure I am able to apply the material by myself after class. If for some reason I cannot apply the material alone I ask the instructors or tutors for help. A third one from the same article is that students should do their work during the class session. I totally agree with this one due to the fact that students learn better around their classmates. In college I do my own work during the class because I can ask the instructor or my fellow classmates’ questions about the work. In conclusion, an education is mostly defined as a process of learning and obtaining knowledge. As we know many problems can occur that can prevent an education to people such as culture, religion, tradition, income, and where you live or come from. Those problems can create different thoughts or assumptions of someone’s educational background. Each person’s education can be different, due to the fact that many types of education plus learning methods and assumptions affect me and others in many other different ways. Works Cited â€Å"Assumptions about Learning.† Center for Teaching & Learning. The University of North Carolina at Charlotte, Internet. . Bennett, William J. â€Å"20 Troubling Facts about American Education.† Empower America. Reprinted by permission of William J. Bennett and Empower America. Internet, http://catholiceducation.org/articles/education/ed0033.html Hamilton, Laura. â€Å"Teachers Matter: Understanding Teachers’ Impact on Student Achievement.† RAND Education. RAND Corporation. Internet. . â€Å"Seven Deadly Assumptions about Students.† Point Loma Nazarene University. PLNU Forward, Internet. 05 Oct. 2013. .

Love Actually Quotes

The 2003 movie Love Actually emphasizes the funny side of love through an interesting series of plots and subplots. The movie follows eight couples—each telling a tale of love and adding a fresh perspective. Their tales are loosely interconnected, and all are set during a month before Christmas in London. If you are in love  or have been in love, you will empathize with the characters in Love Actually. Hugh Grant, Billy Bob Thornton, Laura Linney, and others put in terrific performances. Check out the quotes to reminisce about the movie. Judy All I want for Christmas is you. Aurelia  [in Portuguese] I will miss you. And your very slow typing... and your very bad driving.Thank you. That will be nice. Yes is being my answer. Easy question. Juliet All I want is just one shot of me in a wedding dress that isnt bright turquoise. Sam But you know the thing about romance is people only get together right at the very end.Lets go get the shit kicked out of us by love. Karen True love lasts a lifetime.Weve never got friendly. I just wanted to say I hope that can change. Im nice, I really am, apart from my terrible taste in pie. And it would be great if we could be friends.Get a grip; people hate sissies. No ones ever going to shag you if you cry all the time.The trouble with being the Prime Ministers sister is it does put your life into a rather harsh perspective. What did my brother do today? He stood up and fought for his country. And what did I do? I made a paper-mache lobster head. Karl Life is full of interruptions and complications. Mia Ill just be hanging around the mistletoe, hoping to be kissed. Billy Mack When I was young and successful, I was greedy and foolish, and now Im left with no one ... wrinkled and alone. Jamie [in Portuguese] Beautiful Aurelia, Ive come here with a view of asking you to marriage me. I know I  seems  an insane person—because I hardly  knows  you—but sometimes things are so transparency, they dont need evidential proof. And I will inhabit here, or you can inhabit with me in England.Christmas is a time for people with someone they love in their lives. Daniel Youve seen the films, kiddo. It aint over til its over.Jo and I had, uh, a lot of time to prepare for this moment. Some of her, uh, requests—for instance, that I should bring Claudia Schiffer as my date to the funeral—I was confident she expected me to ignore.Tell her that you love her. Youve got nothing to lose, and youll always regret it if you dont. Colin American girls would seriously dig me with my cute British accent.I am Colin. God of sex. Im just on the wrong continent, thats all.Im on Shag Highway heading west. Sarah Hello, darling. No, no, Im not busy. No ... fire away. Prime Minister I had an uncle called Terence once. Hated him. I think he was a pervert. But I very much like the look of you.Who do you have to screw around here to get a cup of tea and a chocolate biscuit?