Browse Topic: Turbofan engines

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Hydrogen Fueled Aircraft Engines2022-26-115605/26/2022
In the recent years, the climate change has become more devastating, and its continuing use of fossil fuels seems unreasonable as humankind is being pushed into a corner where the need to choose an alternative fuel has become necessary. The two main alternatives currently available are: Electrical propulsion and Hydrogen injected air breathing engines. Electrical propulsion had come far since last 10 years with Li+ ion technology, but the problem with them persists. They provide a low power to weight ratio which reduces the range as well as the load while operating the aircraft. On the other hand, Hydrogen with fuel cells or H2-O2 combustion has a high power to weight ratio but very difficult to handle. So, using hydrogen comes with a lot of difficulties in the present scenario. However. the concept of hydrogen has come a long way since its first use as a Rocket fuel. But this alternate fuel provides many advantages as well as challenges which needs to be overcome to move on its use in
Sri, Ratan, Sivamani, Seralathan
Technical Paper
SAE TOMORROW TODAY: Cleaner, Greener & Quieter: Transforming the Future of Flying1316109/03/2021
The best airplane can only be designed around the best engine - so says Pratt & Whitney, a Raytheon Technologies Company, where they've been transforming powered flight with an explorer's heart and a perfectionist's grit. Lisa Claveloux, Pratt & Whitney's Senior Director, Group Quality, tells the iconic brand's history, what impacts the pandemic has had on the aerospace industry, and the more sustainable footprint that their GTF engines bring to the skies. These revolutionary geared turbofan engines have already saved more than half a billion gallons of fuel and about five million metric tonnes of CO2, while also slashing aircraft noise footprint by 75%. Claveloux's passion for safety drew her to the work of the SAE ITC Aerospace Engine Supplier Quality (AESQ) strategy group. She discusses the challenges in the market, the gap the SAE AS13100 Standard fills, and why compliance is critical for enabling quality and making our skies safe for everyone.
Hineman, Marcie
Podcast
Aircraft Engine Icing Event Avoidance and MitigationTBMG-3473807/01/2019
Innovators at NASA’s Glenn Research Center have developed a new means of avoiding and mitigating icing events for aircraft flying above 14,000 feet, dramatically improving aviation safety and reducing operating costs.
Magazine Article
Novel Turboelectric Aircraft DesignTBMG-2886105/01/2018
NASA Langley Research Center has developed a novel aircraft design that can carry 150+ passengers over a range of 3,500 nautical miles. Key features include a turboelectric propulsion system, twin underwing turbofans, and a rear-fuselage, electrically driven, boundary layer ingesting fan. The design is developed for single-aisle-class aircraft (the largest commercial transport class in the world) to significantly reduce fuel burn compared to current aircraft.
Magazine Article
Variable Bypass Turbofan EngineTBMG-2887705/01/2018
Many aircraft need to operate efficiently at more than one flight regime; for example, certain airframes are expected to perform in relatively high-speed cruise modes, as well as slower loitering scenarios. Unfortunately, an engine operates most efficiently when the exit velocity closely matches the speed of the airframe. As a result, designing an engine that is suitable for multiple roles yields an engine that only performs moderately well in each of those operating conditions.
Magazine Article
Software Helps Optimize World’s Largest All-Composite AircraftTBMG-2800812/01/2017
Collier Research Corp. Newport News, VA
Magazine Article
ASTM-D7684-11 Compliant Computer Aided Interactive Wear Debris Particle Analysis for On-Site Condition Monitoring, Diagnostics and Prognostics2017-01-212409/19/2017
Within the aviation industry analysis of wear debris particles recovered from magnetic plugs and lubricating fluids is an essential condition monitoring tool. However, in large organisations, high staff turnover in remote work environments often leaves dangerous gaps in on-site support and background knowledge. The current work develops interactive software for wear debris particle classification, root cause diagnosis and serviceability prognostics. During the research several hundred wear debris particle images were collected, analysed and classified by a number of experts. At each stage of the analysis the experts were questioned about the knowledge and experience used to make their diagnoses and prognoses. The end result is an extensive knowledge base representing the combined expertise of a number of highly trained engineers, each with decades of hands-on experience. Access to this knowledge base is provided at each stage of interaction with the software, as automatically generated
Leavers, Violet
Technical Paper
Turbofan Engine Acoustic Liner Design and Analysis ToolsTBMG-2686605/01/2017
NASA Langley Research Center has developed two tools for turbofan engine acoustic liner design and analysis. The first is a statistical approach for broadband liner design and assessment; the second is graphical software to design and analyze resonant channels in acoustic liners.
Magazine Article
Uncertainty of In-Flight Thrust DeterminationAIR1678B (Current)10/22/2016
This document defines and illustrates the process for determination of uncertainty of turbofan and turbojet engine in-flight thrust and other measured in-flight performance parameters. The reasons for requiring this information, as specified in the E-33 Charter, are: determination of high confidence aircraft drag; problem rectification if performance is low; interpolation of measured thrust and aircraft drag over a range of flight conditions by validation and development of high confidence analytical methods; establishment of a baseline for future engine modifications. This document describes systematic and random measurement uncertainties and methods for propagating the uncertainties to the more complicated parameter, in-flight thrust. Methods for combining the uncertainties to obtain given confidence levels are also addressed. Although the primary focus of the document is in-flight thrust, the statistical methods described are applicable to any measurement process. The E-33 Committee
E-33 In Flight Propulsion Measurement Committee
Information Report
Numerical Investigations on a Tunable Helmholtz Resonator: Integration of a Passive Polymer Membrane in a Helmholtz Resonator2016-01-184206/15/2016
A Helmholtz resonator is a passive acoustic resonator used to control a single frequency resulting from the cavity volume and the resonator neck size. The main purpose of work in progress is to propose to investigate numerically some strategies allowing real-time tunability of the Helmholtz resonator in order to provide a wider bandwidth and hence enhance noise attenuation. Two concepts will be developed, both based on the use of electroactive polymer (EAP) membranes. These materials exhibit a change of shape when stimulated by an electric field. The first concept consists in replacing the resonator rigid back plate by an EAP material membrane, while on the second one, the membrane is located in front of the resonator. Numerical investigations are performed using several kinds of a passive EAPs material membranes in order to determine the practical potential of these concepts. Significant enhancements of the transmission loss and/or the absorption properties could be obtained in the
Abbad, Ahmed
Technical Paper
Cantera Integration with T-MATSTBMG-2409903/01/2016
The Toolbox for the Modeling and Analysis of Thermodynamic Systems (TMATS) software package is a library of building blocks that can be assembled to represent any thermodynamic system in the Simulink® (MathWorks, Inc.) environment. These elements, along with a Newton Raphson solver (also provided as part of the T-MATS package), enable users to create models of a wide variety of systems. The updated version of T-MATS (v1.1.1) includes the integration of Cantera, an open source thermodynamic simulation tool. T-MATS was initially described in detail in LEW-19165-1, "", Software Tech Briefs (September 2014), p. 11.
Magazine Article
Tool for Turbine Engine Closed-loop Transient Analysis (TTECTrA)TBMG-2220506/01/2015
The current steady-state performance-based system studies are not adequate to evaluate certain advanced technologies for the challenges associated with meeting the transient performance requirements without better definition and control of component operating margins. Additional dynamic analyses would require more detailed, physics-based, component-level models and controllers in order to better identify dynamic issues that may arise during operation of the engine. The additional complexity in these models increases the effort necessary throughout the design processes, including the system-analysis step. The solution would be a physics-based engine model with full envelope controller. C-MAPSS and C-MAPSS40k are examples of engine models with full envelope controllers, but because they are designed to model a specific engine, they are not good candidates for systems analysis.
Magazine Article
Passive Destructive Interference Acoustic Liner for a Turbofan Engine Using Additive ManufacturingTBMG-2199905/01/2015
This technology exploits the capabilities of additive manufacturing to attenuate the fan noise within the inlet or aft duct of a turbofan engine. The approach may be expanded to include auxiliary power units, environmental control systems, or other cooling systems requiring noise attenuation.
Magazine Article
Distribution of Power13AERD0603_0206/03/2013
When designing the electrical distribution system for a turboelectric architecture, it is imperative to select technologies that will provide the highest efficiency and stability for the propulsion system. Turboelectric propulsion is a revolutionary system in which the propulsor (fan) is not connected to the turbine through a mechanical connection; thus, both components can be set at their individual optimum speeds. Also, turboelectric propulsion makes use of distributed fans, using several small fans in place of the traditional large propulsors on the wings or sides of the fuselage. Distributed fans are usually placed on the top side of the fuselage of a blended wing body aircraft to take advantage of boundary layer ingestion that increases fan performance. The smaller fans can run at faster speeds than their larger counterpart in a turbofan engine.
Magazine Article
Acoustic Liner for Turbomachinery ApplicationsTBMG-849109/01/2010
The purpose of this innovation is to reduce aircraft noise in the communities surrounding airports by significantly attenuating the noise generated by the turbomachinery, and enhancing safety by providing a containment barrier for a blade failure. Acoustic liners are used in today’s turbofan engines to reduce noise. The amount of noise reduction from an acoustic liner is a function of the treatment area, the liner design, and the material properties, and limited by the constraints of the nacelle or casement design. It is desirable to increase the effective area of the acoustic treatment to increase noise suppression. Modern turbofan engines use “wide-chord” rotor blades, which means there is considerable treatment area available over the rotor tip.
Magazine Article
System Would Detect Foreign-Object Damage in Turbofan EngineTBMG-TB-00106001/29/2007
Vibration-sensor and gas-path-analysis data would be fused. A proposed data-fusion system, to be implemented mostly in software, would further process the digitized and preprocessed outputs of sensors in a turbofan engine to detect foreign-object damage (FOD) [more precisely, damage caused by impingement of such foreign objects as birds, pieces of ice, and runway debris]. The proposed system could help a flight crew to decide what, if any, response is necessary to complete a flight safely, and could aid mechanics in deciding what post-flight maintenance action might be needed.
Magazine Article
Breaking records via fuel managementAEROMAY06_0305/01/2006
Onboard sensors reported lower-than-expected fuel-tank readings not far into the around-the-world flight of the GlobalFlyer, jeopardizing the entire mission. In March 2005, the Virgin Atlantic turbofan-powered GlobalFlyer flew around the world nonstop, unrefueled, in 67 hours and one minute. Aerodynamics was key to GlobalFlyer's success; its configuration was optimized for range and fuel efficiency. At takeoff, the aircraft was approximately 83% fuel by weight. Getting the fuel to where it was needed, while maintaining balance and stability in flight, required constant supervision and monitoring. Scaled Composites, which also designed and launched SpaceShipOne, built the GlobalFlyer. The aircraft consisted of three bodies attached to a 114-ft wing measuring more than half the wingspan of a Boeing 747. Twin “booms” on either side of the central fuselage each carried almost 5500 lb of fuel.
Magazine Article
System Would Detect Foreign-Object Damage in Turbofan EngineTBMG-106001/01/2006
A proposed data-fusion system, to be implemented mostly in software, would further process the digitized and preprocessed outputs of sensors in a turbofan engine to detect foreign-object damage (FOD) [more precisely, damage caused by impingement of such foreign objects as birds, pieces of ice, and runway debris]. The proposed system could help a flight crew to decide what, if any, response is necessary to complete a flight safely, and could aid mechanics in deciding what post-flight maintenance action might be needed.
Magazine Article
Aerospace Engineering 2004-07-01AEROJUL0407/01/2004
More-electric small turbofan engines The aerospace industry demands continuous improvement of propulsion engines as well as timely response to the new and changing requirements for them. Zero-emissions aircraft Researchers explore the potential application of alternative fuels and propulsion systems for aircraft that include a business jet and single-engine propeller aircraft. Integration releases the reins Cessna's new Citation Mustang launches the company into a new market for business jets, helped by the latest PLM solutions from IBM. Military: general A military flight-control system proposed for use in general aviation uses inverse control to decouple the flight controls and to modify the handling qualities of the aircraft, while employing articficial neural networks to compensate for any modeling errors.
Magazine Issue
Program Predicts Broadband Noise From a Turbofan EngineTBMG-175201/01/2004
Broadband Fan Noise Prediction System (BFaNS) is a computer program that, as its name indicates, predicts the broadband noise generated by the fan stage of a turbofan engine. This noise is the sum of (1) turbulent- inflow noise, which is caused by turbulence impinging on leading edges of the fan and the fan exit guide vane and (2) self noise, which is caused by turbulence convecting past the corresponding trailing edges. The user provides input data on the fan-blade, vane, and flow-path geometries and on the mean and turbulent components of the flow field. BFaNS then calculates the turbulent-inflow noise by use of D. B. Hanson's theory, which relates sound power to the inflow turbulence characteristics and the cascade geometry. Hanson's program, BBCASCADE, is incorporated into BFaNS, wherein it is applied to the rotor and stator in a stripwise manner. The spectra of upstream and downstream sound powers radiated by each strip are summed to obtain the total upstream and downstream sound
Magazine Article
Aerospace Engineering 2001-11-01AERONOV0111/01/2001
Safeguarding aircraft systems How several systems suppliers, airframers, and researchers have approached the need for increased system safeguards and protection against lightning strikes. One last look back A review of the technology news, discussions, and announcements from the first Aerospace Congress & Exhibition held September 10-13 in Seattle, WA. Powering unmanned aircraft Pratt & Whitney Canada is developing and testing a commercial turbofan engine derivative for high-altitude unmanned air vehicle applications. 737-800 winglet integration A joint venture between Boeing and Aviation Partners Inc. is involved in developing a performance improvement for in-service aircraft.
Magazine Issue
Optimal and Near-Optimal Take-off Maneuvers in the Presence of Windshear2000-01-559310/10/2000
This paper is concerned with the development of short-range forward-look guidance strategies for take-off maneuvers in the presence of windshear, with reference to flight in the vertical and horizontal plane. In addition to the horizontal shear, the presence of a downdraft is assumed. First, two open-loop optimal escape strategies are considered, viz. a performance maintaining strategy and a survival strategy, where it is assumed that the windshear is detected in an early stage of the encounter. Next, two closed-loop guidance strategies featuring short-range forward-look detection, which closely approximate the open-loop optimal solutions, are developed. Numerical results show that lateral maneuvering, in which an aircraft is turned away from the microburst, improves the flight performance significantly in both optimal escape strategies. The simulation results demonstrate that the employed closed-loop guidance strategies are able to closely approximate the open-loop optimal
Elferink, K., Visser, H.G.
Technical Paper
Software Predicts Noise From Rotor-Wake/Stator InteractionsTBMG-696310/01/2000
V072 is a computer program that predicts the noise generated by the interaction between the rotor-blade wake (fan wake) and the stator vanes of a turbofan engine. The program is a combination of subroutines from prior NASA programs, with many added features.
Magazine Article
Preliminary Sizing of a Supersonic Commercial Transport Between Mach 2.0 and 2.496558910/01/1996
To review specifications of a next-generation supersonic commercial transport (SCT), conceptual design is performed. The study covers the cruise speed between Mach 2.0 and 2.4, and the range between 4,000 nmi and 6,000 nmi with the number of seats fixed to 300. Engines for Mach 2.0, 2.2 and 2.4 are conceptually designed and the data are applied to Japan Aircraft Development Corporation (JADC)'s SCT sizing and performance prediction tool (“CAD”). The maximum take off weights (MTOW) are surveyed to find the best combination of cruise speed and range.
Takasu, Toru, Maekawa, Shoji, Ugai, Takashi, Mizuno, Hiroshi
Technical Paper
The Development and Application of Aircraft Radar Cross Section Prediction Methodology96553910/01/1996
In the last twenty years, radar cross section (RCS) reduction has emerged as an important and achievable way to improve the survivability of military aircraft. Specifically, the first manned aircraft to achieve a tactically significant reduction in RCS was the Lockheed Have Blue technology demonstrator, which was designed starting in 1975 and first flew in 1977. This was followed by a true military aircraft, the F-117 A, which became operational in 1983. Several very low observable (VLO) aircraft have been designed since then. All of them benefit from significant advances in the ability to predict and improve the RCS of an aircraft in its early design stages. The present paper describes these advances and their impact on aircraft design, using examples of reduced RCS aircraft designed before and after the techniques were evolved.
Aronstein, David C.
Technical Paper
High Bypass Separate Flow Exhaust System Improved Thrust Efficiency By Modifying the Aft Centerbody93262209/01/1993
Scale model data indicated a performance dip in nozzle thrust efficiency at the cruise design conditions for a high bypass separate flow derivative exhaust system. A performance improvement program was implemented to determine the cause of the reduction in thrust efficiency and to identify viable redesigns. Data analysis indicated the performance loss to be a result of high Mach number fan and core exhaust interactions adversely affecting the pressure force on the exhaust system centerbody. Scale model testing confirmed the cause of performance loss and demonstrated that modifying the aft centerbody to reduce the plume Mach number recovers the loss in exhaust system thrust efficiency.
Babbitt, Bob
Technical Paper
Prediction of Engine Casing Temperature of Fighter Aircraft for Infrared Signature Studies92096104/01/1992
Prediction of Engine Casing Temperature of Combat Aircraft for various operating conditions needs modeling of convective and radiative heat flow from the jet pipe to the casing. Radiation modeling which implies modeling of multiple reflections and scattering is done here by the radiance-irradiance approach. The engine layout is approximated by three co-axial cylinders and axially discretized. The shape factors (which account for the directional dependence of radiation heat flow) for various configurations needed in radiation modeling are analytically obtained by a sequence of shape factor algebra from standard configurations. The resulting non-linear algebraic equations of combined convection and radiation heat flow are solved by an iterative technique to give the engine casing temperatures which may be used for infrared signature studies.
Mahulikar, Shripad Prabhakar
Technical Paper
Initial Service Experience With the Fokker 10089223809/01/1989
The paper outlines the behaviour of the Fokker 100 during its first year of commercial service with Swissair, the launch customer. Main design features are briefly discussed, together with selection criteria which prompted Swissair to become launch customer. Some aspects of crew training in relation to the introduction of glass cockpits are highlighted.
Ammann, H., van der Schraaf, A.
Technical Paper
Application of KTRAN Transonic Small Disturbance Code to the Challenger Business Jet Configuration with Winglets88148310/01/1988
A Transonic Small Disturbance code originally developed at Canadair for the analysis of 3D wing/body/pylon/store configurations (AGARD CP-412-8) has been extended to calculate flows around complete aircraft such as the Challenger Executive Jet. The program uses a modified Transonic Small Disturbance equation discretized in cartesian and cylindrical coordinates and a grid embedding technique to capture flow details around specific components. The equation is solved using a successive line over-relaxation technique applied in two phases. In the first phase, the flow field is relaxed in the overall crude grid and in the winglet cylindrical grid. In the second phase, the crude grid and the various embedded fine grids are relaxed in alternating steps. The interaction between the various grids is through simple linear interpolation. The program is capable of representing Challenger-type wide body fuselages, large aspect ratio supercritical wings, high by-pass turbofan engines and canted
Kafyeke, F., Piperni, P., Robin, S.
Technical Paper
Series Flow Tandem Fan: A High-Speed V/STOL Propulsion Concept84149610/01/1984
A promising high speed V/STOL propulsion concept, the series flow tandem fan (SFTF), was analyzed by Vought for a single engine airplane configuration. The SFTF propulsion system was evaluated for size, performance and technology issues by engine companies under contract. Under contract to the Naval Air Propulsion Center (NAPC), Vought assessed engine contractor definition of baseline and alternate SFTF propulsion systems when installed in a representative aircraft concept. This paper will summarize the results of these studies and show the impact on VTO thrust requirements, exhaust temperature and airplane performance. Further, the effect of STOVL criteria on vehicle sizing and engine design is being studied under a follow-on contract.
Clingingsmith, T. W.
Technical Paper
Development of a Compact Real-Time Turbofan Engine Dynamic Simulation82140102/01/1982
Recent developments in the area of digital propulsion controls have precipitated requirements for compact real-time dynamic engine simulations. This paper describes the analytical development and experimental validation of a full range, non-linear model of the F404-GE-400 afterburning turbofan engine. Unique approaches were used to obtain a highly compact model which is capable of being operated in an engine mounted airborne digital computer. The model served as a signal source in a failure protection scheme, providing an unusual basis for model validation. Highlights of the very successful broad ranging validation and use of this model* are provided.
French, Michael W.
Technical Paper
JT8D Performance Improvement to Offset Rising Fuel Costs80111709/01/1980
This paper describes Pratt & Whitney Aircraft's performance improvement program for its JT8D turbofan engines. Retrofit kit programs for existing in-service engines and major new engine programs have evolved from this effort which has been underway since 1978. Changes are being made to the fan, compressor, and turbine sections of the various engine models to improve component efficiency levels and significantly decrease engine thrust specific fuel consumption. Retrofit packages will provide thrust specific fuel consumption reduction of 2.1 percent for JT8D-1 and -7 engines, 3.0 percent for JT8D-9 engines, and 5.5 percent for JT8D-15, -17 and -17R engines at cruise conditions. Fuel savings at other conditions are comparable.
Fahle, Robert K.
Technical Paper
Feasibility of Forward - Swept Wing Technology For V/STOL Aircraft80117609/01/1980
The application of forward-swept wing technology to V/STOL aircraft was found to be feasible. In addition to the previously known benefits to the conventional-flight performance, the leading edge sweep forward-swept wing offers unique benefits to certain classes of V/STOL aircraft. For these classes of aircraft, it is possible to obtain synergism between advances in airframe and engine technology.
Kalemaris, Stanley G.
Technical Paper
Integrated Engine Inlet Thermal Anti-Icing and Environmental Control System (TAI/ECS)76051702/01/1976
The integrated engine inlet thermal anti-icing and environmental control system (TAI/ECS) for subsonic transport airplanes was conceived primarily for the efficient use of available energy and minimum engine bleed air extraction. The concept employs the engine inlet leading edge as the heat exchanger to provide ice protection for the engine inlet surfaces and to cool bleed air for the environmental control system. The results of a study conducted for a typical wide-body airplane using high bypass ratio engines show that the system concept will result in potential improvements in airplane operation and engine maintenance.
Shah, A. D.
Technical Paper
The HiMAT RPRV Propulsion Control System76088702/01/1976
A multimode propulsion control system concept has been developed for the remotely piloted research vehicle of the NASA Highly Maneuverable Aircraft Technology program. The concept is based on the retention of most of the bill-of-materials control hardware, and will allow the implementation of flight/propulsion control coupling, high and normal flow stability margin operating modes, and rapid and normal thrust response modes. Description of the control system, the airborne control components, and the ground generated and displayed signals is given in this paper.
Bayati, Jamal E.
Technical Paper
Turbine Engine Parts Life Improvement Through Thrust Management75058902/01/1975
The general subject of turbine engine thrust management includes the selection and setting of engine thrust. Flight manual information available to the operator of turbine powered aircraft defines the methods for selecting thrust levels with relation to a predetermined minimum airplane performance standard. The logical selection of thrust level to be used requires an understanding of the resultant effect on engine parts life as well as the effect on operating economics.
Spear, Calvin O.
Technical Paper
LARZAC: A Small Turbofan Engine for Military and General Aviation Aircraft74080702/01/1974
The Larzac turbofan engine, rated at 1318 deca Newtons (2965 pounds) thrust at sea level static, is now in final qualification as a powerplant for a new generation of military trainers, light strike fighters, and small business jets. The Larzac engine is being developed by two French companies through a joint controlling group known as Groupement TURBOMECA/SNECMA(GRTS). Teledyne CAE has an exclusive agreement with GRTS to market, sell and service the Larzac in the United States and Canada, and also has an option to manufacture the engine. This paper discusses the Larzac engine design, development, flight test, preliminary qualification test and manufacture.
Chuslo, Lawrence A., Greenburg, Harley D.
Technical Paper
Low-Speed Aerodynamics of the Upper-Surface Blown Jet Flap74047002/01/1974
This paper summarizes the results of recent wind-tunnel investigations conducted to provide fundamental aerodynamic information on the upper-surface blown jet-flap concept incorporating high-bypass-ratio turbofan engines. The results of the investigations have shown the concept to have aerodynamic performance generally comparable to that of other externally blown high-lift systems. This paper will cover some of the more critical problem areas associated with this concept and will discuss solutions which have been found for these problems.
Johnson, Joseph L., Phelps, Arthur E.
Technical Paper
PROPULSION TECHNOLOGY ADVANCES NEEDED FOR A QUIET SUPERSONIC TRANSPORT73089802/01/1973
Operation of a U.S. developed supersonic transport must and will meet community noise standards. This paper examines the airport noise problems of large transport aircraft, highlights critical considerations, and then studies possible solutions available from advanced propulsion technology. Engine sizing requirements to meet SST payload-range and airport performance criteria are reviewed first, and the impact of noise on the engine size and aircraft performance is then identified. Relief offered by noise suppressor development and technology advances that can be foreseen in the next decade for turbojet and turbofan engines are described. The advantages offered by a duct heating turbofan engine cycle are discussed. The potential offered by variable cycle engines to provide low noise characteristics with minimum penalty on performance are shown, and the practical restraints imposed on this potential by airframe aerodynamic noise is illustrated. The importance of supporting engine
FOSS, RICHARD L., BRAGDON, ELLWOOD L.
Technical Paper
A Second Generation High Power Marine Gas Turbine71020402/01/1971
This paper discusses the components and systems incorporated in the design of the LM2500 marine gas turbine. The discussion describes the novel and high performance features of this second generation marine gas turbine which include a high pressure ratio compressor, high temperature gas generator turbine, gas generator turbine cooling system, and high performance power turbine. The paper describes the materials used and the features incorporated which enable the LM2500 to operate successfully in a marine environment. The LM2500 marine gas turbine derived from the General Electric TF39/CF6 turbofan engine family incorporates many engineering advances which are not available in the first generation marine gas turbines. These advanced features enable the LM2500 marine gas turbine to achieve performance levels unmatched by any first generation marine gas turbines now in service. Because of its lower air flow, smaller size, and integrated components and systems, the LM2500 marine gas
Hardgrove, G. A.
Technical Paper
The PT6 After 5 Million Hours71038502/01/1971
The first PT6A-6 turboprop engine, rated at 500 shp, was delivered in December 1963 with an initial life of 600 hr between overhauls. By early 1971, over 4000 engines had been delivered, the output had grown to 900 shp, and times between overhaul in excess of 5000 hr had been reached. The technology spawned by the PT6 has resulted in the development, by UACL, of a host of turboprop, turboshaft, and turbofan engines, along with industrial derivatives. In over 5 million hr of operation, the PT6 has clearly demonstrated how sound technology and persistent development can meet the exciting challenges of the 1970s.
Cowley, F. R.
Technical Paper
Turbine Engine Technology and Cost70027002/01/1970
An analysis was conducted on a total of 106,000 turbojet and turbofan engines procured by the United States Air Force to ascertain if an aircraft turbine engine's cost can be effectively correlated to its technical performance. Results indicate that such technical parameters are not valid and other factors such as military situation, economic conditions, and procurement situation should be investigated.
Seely, George H., Stibich, Marvin A.
Technical Paper
Inlet and Fan Aerodynamics68071102/01/1968
Current trends in military combat aircraft are clearly toward increased emphasis on multimission capability. This requires an engine that is considerably oversized when compared with the subsonic cruise or dash requirements of the aircraft. With oversized engines, engine performance is no longer an isolated element. A new approach is needed. This paper analyzes the inlet portion of the installed propulsion system. An assessment is made of the magnitude of the inlet drag associated with oversized engines for typical multimission aircraft. Some thoughts are presented on inclusion of inlet drag considerations into the engine cycle optimization process.
Taylor, Richard P.
Technical Paper
Reengining Large Jet Transports in 1972? - Economics and Technology66032102/01/1966
The purpose of this paper is to explore one part of the 1972 commercial air transport picture. New jet engine and aircraft technology will be available which offers substantial advantages in operating economics. A major portion of the improvement will come by way of the engine redesigns. Higher bypass ratios, higher turbine inlet temperatures, and substantially advanced structural concepts point in the direction of lower direct operating costs. An analysis is made using these “new technology” engines on older fleets of large jet transports. Results show that the domestic operators have little to gain. Longer range, intercontinental operators may find the engine conversion attractive for some route segments where range is critical. Engine maintenance costs, among other costs, associated with reengining are considered. Finally, using these results, an estimate is made of an airplane size which will maximize the cost-reduction potential of the engines.
Searls, F., Joe, C. Y.
Technical Paper
Lubrication of the SST Engine66071102/01/1966
The effect of the flight environment on the severity of the lubrication requirements of the Pratt & Whitney candidate SST engine is reviewed and compared with current commercial turbofan engines. The characteristics of currently available lubricants are examined. The deisgn features of the SST engine aimed at reducing lubricant system stress are discussed. The conclusion is drawn that several type II oils currently available will meet the requirements established by the P & WA SST engine.
Daley, J. A.
Technical Paper
C-5A Cargo Transport Aircraft65024802/01/1965
The C-5A cargo transport aircraft is being developed by the Air Force to provide the means to deploy Army and Air Force tactical units rapidly to trouble spots world wide. The size of the C-5A will allow transport of almost all Army fighting and support equipment directly from the United States to support areas close to the point of employment.
Martin, R. S.
Technical Paper
Operating Procedures Associated with Noise Generated by the Supersonic Transport65021402/01/1965
The noise characteristics of The Boeing Company variable sweep supersonic transport are described. It is predicted that the noise levels of this airplane will be lower than those of current intercontinental subsonic jets. However, the noise generated by the supersonic transport could be substantially modified by the way the aircraft will be operated. The flexibility in operation afforded by the Boeing supersonic transport for achieving low noise levels, both airport and in the community, is reviewed. No major noise problems are anticipated because of SST operations at present airfields.
Gebhardt, George T., Sawhill, Robert H., Marhefka, Robert J.
Technical Paper
REQUIREMENTS FOR LONG RANGE -LONG ENDURANCE AIRCRAFT64049001/01/1964
Propulsion system requirements of long range, long endurance aircraft are described with emphasis on turbofan engines. The factors influencing the optimum design bypass ratio of a turbofan engine are discussed, and some effects of laminar flow control and cargo space requirements upon optimum turbofan engine design are shown. A parametric study of airplane performance is used to compare a series of industry study engines as a means of showing the relationship between airplane design and engine design. Clean airplane designs require significantly higher bypass ratios for maximum range and endurance.
Wheaton, R.J., Bogdanovic, J.A., Feder, A.
Technical Paper
The Assessment of Supersonic Transport Operating Costs64083101/01/1964
The fixed plus variable cost concept is frequently employed in the analysis of productive industrial processes. This paper discusses application of this concept to the assessment of the direct operating costs of a proposed supersonic transport aircraft. It is shown that the unit variable cost is approximately the same for the proposed supersonic transport airplane as it is for current subsonic long range jet transports. The unit fixed cost, however, is four times as great for the supersonic transport as it is for subsonic transports. The factors which cause the increased fixed costs in the supersonic transport are identified.
Nowlan, F. S., Comstock, K. W.
Technical Paper
An Application of Brazed Stainless Steel Honeycomb for Moderately High Temperature Structures63039101/01/1963
The C-141 airplane is powered by four Pratt & Whitney turbofan engines with the fan mounted on the compressor end. High velocity, high pressure air from the fan is ducted to the aft end of the nacelle through kidney shaped ducts. In the tailpipe area, the ducts and tailpipe utilize a common skin. During rapid engine deceleration a condition can occur that subjects the tailpipe to a collapsing pressure. A single skin tailpipe subjected to this pressure at an operating temperature of 1000 F would have been excessively heavy. Brazed stainless steel honeycomb with thin face gages and lightweight core was selected for this application with a substantial saving in weight and no loss in performance.
Gray, W. P., Linderman, D. L
Technical Paper
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