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The Jet Age, Continued

2005; ASM International; Volume: 127; Issue: 1 Linguagem: Inglês

10.1115/1.1791278

1528-8900

William H. Heiser,

Advanced Aircraft Design and Technologies

Contributed by the Turbomachinery. Division of THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS for publication in the JOURNAL OF TURBOMACHINERY. Manucript received January 17, 2004; final revision February 8, 2004. Associate Editor: D. Wisler.I was pleased and honored to be invited to make the opening presentation of the International Gas Turbine Institute Budugur “Bud” Lakshminarayana Memorial Session. It has been a privilege to know and work with Bud for over 30 years, and the sole purpose of my talk is to celebrate his accomplishments and contributions, and a life well lived. I have always thought of Bud primarily as a teacher, a title I hold in the highest regard. He taught through his lectures, writings, research, and, most of all, by example. My first professional contact with Bud occurred when I was working in the turbine technology group at Pratt & Whitney in the late 1960’s, and we were striving to improve the cascade loss models in our performance procedures. We discovered that the end loss models published by Bud were perfect for our situation. They were fundamentally sound, intuitively appealing, broadly applicable, and easily incorporated. From that time on, we always paid attention to his publications. During 1976–82 I had the opportunity to visit Bud periodically at the Pennsylvania State University as a member of the College of Engineering Industrial and Professional Advisory Council. This allowed me to witness first hand the deservedly famous turbomachinery laboratory he had created with his talent and dedication, as well as some of the outstanding students he nurtured (although it was not clear that they felt nurtured). As the years passed, I also discovered that he cared deeply about the professional societies, working tirelessly to improve their services, and felt passionately about providing the best possible educations for his own children. My foremost intention is that this presentation would have interested and pleased Bud. It seeks to answer the implied question about what the Jet Age has in store for the turbine engine. We are all inhabitants of the Jet Age, many of us having known nothing else. Jet-propelled aircraft are so pervasive, and have such a strong hold on civilization, that it is impossible to envision a world not heavily influenced by their presence. But what will the future mean to jet propulsion, and the people who work in the field? The best way I can answer that question is to examine what has motivated change in the past, and what is likely to motivate change in the future. In order to do that, I have divided the motivations I understand into three categories, and explore them in turn, as follows. There are many turbine engine technologies that are pursued because the laws of nature guarantee that they will improve specific thrust, specific fuel consumption, weight, reliability, and/or cost. The list below, which is neither exhaustive nor prioritized, illustrates this type of work, which might be called evolutionary because it produces continuous progress. It is worth noting that many of the papers in many of the sessions of this IJGPC Conference are dedicated to these, or closely related, subjects. This suggests that contemporary experts have many promising concepts that will continue the evolutionary process. Evolutionary Technologies It is easy to demonstrate that evolutionary improvements in the vehicle and engine plus fuel weight alone can significantly reduce the gross takeoff weight of aircraft of fixed mission and payload. Reductions of gross takeoff weight for conventional aircraft (e.g., commercial subsonic transports) of 35%–40%, and for advanced aircraft (e.g., supersonic bombers or transports) of 55%–60% are easily achievable within the next 20 years. Since life cycle cost (i.e., acquisition, operation, and maintenance) depends strongly on gross takeoff weight, these potential gains are irresistibly tempting to the industry and society. The gross takeoff weight reductions can, of course, be traded for other improvements, such as greater payload and/or range. This leads us to the confident conclusion that the evolutionary path will continue to be followed for the foreseeable future. The Robert J. Collier Trophy, awarded annually by the National Aeronautic Association, is the best indicator available of the forces that have motivated innovative changes of the whole engine. The Collier Trophy sets high standards for demonstrated achievement, as witnessed by its criterion: “For the greatest achievement in aeronautics or astronautics in America, with respect to improving the performance, efficiency, and safety of air or space vehicles, the value of which has been thoroughly demonstrated by actual use during the preceding year.” It often surprises people to learn that aircraft engines have been the recipients of the Collier Trophy. The compilation below, which contains the entire citation for the selected awards, clearly demonstrates the importance of jet propulsion to modern aviation. Collier Award Citations1940: Dr. Sanford A. Moss and the Army Air Corps For development of the turbo-supercharger. 1952: Leonard S. Hobbs of United Aircraft Corporation For design, development, and production of the J-57 jet engine. 1958: The United States Air Force and Industry Team Responsible for the F-104 Interceptor. Clarence L. Johnson of Lockheed Aircraft Corporation for the design of the airframe; Neil Burgess and Gerhard Neumann of the Flight Propulsion Division; General Electric Company, for development of its J-79 turbo jet engines; Major Howard C. Johnson, USAF for establishing a world land plane altitude record of 91,243 Feet; and Captain Walter W. Irwin, USAF, for establishing a world straightaway speed record of 1,404.09 miles per hour. 1970: The Boeing Company As leader of the industry-airline-government team which successfully introduced the 747 into commercial service with particular recognition to Pratt and Whitney Division of United Aircraft Corporation and to Pan American World Airways. 1978: Sam B. Williams, Chairman and President, Williams Research Corporation For conceiving and developing the world’s smallest, high efficiency turbofan engine which was selected to power U.S. cruise missiles. 1987: NASA Lewis Research Center and the NASA/industry Advanced Turboprop Team For the development of advanced turboprop propulsion concepts for single rotation, gearless counter rotation, and geared counter rotation inducted fan systems. 1999: The Boeing Company, GE Aircraft Engines, Northrop Grumman Corporation, Raytheon Company, and the United States Navy For designing, manufacturing, testing and introducing into service the F/A-18E/F multi-mission strike fighter aircraft, the most capable and survivable carrier-based combat aircraft. 2001: Pratt & Whitney, Rolls-Royce, Lockheed Martin Corporation, Northrop Grumman Corporation, BAE SYSTEMS and the Joint Strike Fighter Program Office For designing, developing, and demonstrating the Integrated LiftFan Propulsion System, the next generation in aviation propulsion performance, efficiency and safety.The initial message inherent in this progression of awards seems to be that the turbine engine configuration has slowly changed in predictable directions through the years. The passage of time has witnessed the enhancement of the basic turbojet cycle with afterburning (to increase thrust), increasingly larger bypass ratios (to reduce fuel consumption), and combinations of these to provide flexibility. Interesting variants, such as very small engines and innovative turboprops have also appeared. Recently, however, the Joint Strike Fighter introduced a radical departure by combining the afterburning turbofan with a shaft-driven lift fan and a thrust-deflecting nozzle to enable short takeoff and vertical landing. One may conclude that a period of innovation and experimentation has begun that will supplement the gradual alteration of engine cycles. The future is likely to bring many new forms of turbine engines that enable entirely new applications. This could well be a period of great challenge and accomplishment for propulsion engineers. The undeniable truth is that unpredictable, external forces have driven much good technical work in the past. The partial list below illustrates the enormous range of technical demands that already have been encountered and satisfied. It is an interesting fact that solving these problems required improved analytical and experimental methods that were often capitalized upon for other purposes. Take, for instance, the case of smoke and chemical emissions, all of which are generated in the main combustor. No one could possibly have foreseen the explosion of the public interest in environmental protection that followed from the original complaints in Newark, New Jersey. The sophisticated main combustor modeling techniques and instrumentation necessary for understanding and controlling chemical composition that resulted have allowed designers to meet increasingly stringent regulations, and have simultaneously made the combustion process virtually 100 percent efficient. Today, these methods are being used to further extend the operating range of main combustors and to advance the design of military afterburners. Wild Cards Past The partial list below illustrates the equally enormous range of technical challenges that have just begun to make themselves known, and are realistic candidates to be the focus of intense future efforts. No one knows for certain which of these will mature into celebrity, or what other topics are about to emerge. It is certain, nevertheless, that things will happen, and that they will change their associated technologies for the better. Take, for instance, the relatively recent recognition that CO2 and H2O, which have been the desired products of traditional hydrocarbon fuel combustion, contribute to the greenhouse effect and therefore to unwanted atmospheric heating. What could be done to reduce these newly undesirable turbine engine emissions? What could be done to eliminate them? How could the solution of this problem lead to the solutions of others? Wild Cards Yet To Come The steadily increasing application of jet propulsion and the public awareness of its impact on the environment guarantee that the wild cards will continue to motivate dramatic change. The past has taught us, fortunately, that effective solutions will not only be found, but that they will be used to foster other advancements.Bud Lakshminarayana continually adjusted to the motivations described above. We can easily see that through the many legacies he left for our benefit. For example, the listing below of the chapter titles from his textbook, Fluid Dynamics and Heat Transfer of Turbomachinery, published by John Wiley and Sons, Inc., in 1996, follows the development of his technical interests. In the first four chapters he develops classical, foundational concepts, applies them to turbomachinery, and extends them to increasingly more complex and realistic situations. Chapter 5 reveals the enormous interest and expertise he developed in computational methods. One significant by-product of this work was that Bud spearheaded the development and directed the work of a computational fluid dynamics institute at Penn State. Chapter 6 collects the excellent experimental evidence of his career, including the end loss research that originally brought him to my attention. Finally, in Chapter 7, he provides a unique, comprehensive exploration of the profoundly bewildering and essential field of turbine cooling, proving that he kept up with the times, no matter how hard the problem. Chapter 1: Classification and Basic Concepts of Fluid Mechanics Chapter 2: Fundamental Principles, Analysis, and Performance of Turbomachinery Chapter 3: Cascade Inviscid Flows Chapter 4: Three-Dimensional Inviscid and Quasi-Viscid Flow Field Chapter 5: Computation of Turbomachinery Flows Chapter 6: Two- and Three-Dimensional Viscous Effects and Losses Chapter 7: Turbine Cooling and Heat Transfer Further, his many graduate students can be found in positions of influence throughout the turbomachinery community. His colleagues throughout academia, government, and industry remember the positive influence he had on them. His research endures to teach others in the changing world of the future. His many honors, awards, and visiting positions certify that he was recognized around the world, and that his curiosity was also boundless. In closing, it is important to record that Bud had many tantalizing offers of positions that would have been commensurate withhis ability and embellished his resume. As one might expect, Bud studied them carefully and considered them seriously. Nevertheless, in the end he decided every time to stick with the things that interested him the most, and in which he had invested his personal energy. These are admirable and increasingly rare human traits that emphasize his special character. We are indeed fortunate to have known him.