Showing papers on "Turbofan published in 1980"

Strut supported inlet

Abstract: A high bypass turbofan engine is coupled to a wing strut by a spaceframe thrust linkage. The linkage transfers the axially oriented thrust-induced loads to the strut along the axial horizontal centerplane of the engine. The inlet to the engine is supported by a combined triangular and tetrahedral linkage system which suspends the inlet and transfers axial, vertical, and side loads directly from the inlet to the strut. The inlet is coupled to the engine fan case via a plurality of fluid-filled piston and cylinder assemblies that transmit only axially oriented loads from the inlet to the fan case. Additionally, the linear actuators for the annular thrust reverser are coupled to the inlet so that the axial thrust reversing loads are first transferred to the inlet, from which the axial loads are effectively transferred to the fan case along the engine centerline and hence to the strut via the spaceframe linkage.

Scale model performance test investigation of exhaust system mixers for an Energy Efficient Engine /E3/ propulsion system

Abstract: A scale model performance test was conducted as part of the NASA Energy Efficient Engine (E3) Program, to investigate the geometric variables that influence the aerodynamic design of exhaust system mixers for high-bypass, mixed-flow engines. Mixer configuration variables included lobe number, penetration and perimeter, as well as several cutback mixer geometries. Mixing effectiveness and mixer pressure loss were determined using measured thrust and nozzle exit total pressure and temperature surveys. Results provide a data base to aid the analysis and design development of the E3 mixed-flow exhaust system.

Experimental evaluation of exhaust mixers for an Energy Efficient Engine

Abstract: Static scale model tests were conducted to evaluate exhaust system mixers for a high bypass ratio engine as part of the NASA sponsored Energy Efficient program. Gross thrust coefficients were measured for a series of mixer configurations which included variations in the number of mixer lobes, tailpipe length, mixer penetration, and length. All of these parameters have a significant impact on exhaust system performance. In addition, flow visualization pictures and pressure/temperature traverses were obtained for selected configurations. Parametric performance trends are discussed and the results considered relative to the Energy Efficient Engine program goals.

Combined pressure and temperature distortion effects on internal flow of a turbofan engine

Abstract: An additional data base for improving and verifying a computer simulation developed by an engine manufacturer was obtained. The multisegment parallel compressor simulation was designed to predict the effects of steady-state circumferential inlet total-pressure and total-temperature distortions on the flows into and through a turbofan compression system. It also predicts the degree of distortion that will result in surge of the compressor. The effect of combined 180 deg square-wave distortion patterns of total pressure and total temperature in various relative positions is reported. The observed effects of the combined distortion on a unitary bypass ratio turbofan engine are presented in terms of total and static pressure profiles and total temperature profiles at stations ahead of the inlet guide vanes as well as through the fan-compressor system. These observed profiles are compared with those predicted by the complex multisegment model. The effects of relative position of the two components comprising the combined distortion on the degree resulting in surge are discussed. Certain relative positions required less combined distortion than either a temperature or pressure distortion by itself.

Core noise measurements from a small, general aviation turbofan engine

Abstract: As part of a program to investigate combustor and other core noises, simultaneous measurements of internal fluctuating pressure and far field noise were made with a JT15D turbofan engine. Acoustic waveguide probes, located in the engine at the combustor, at the turbine exit and in the core nozzle wall, were used to measure internal fluctuating pressures. Low frequency acoustic power determined at the core nozzle exit corresponds in level to the far field acoustic power at engine speeds below 65% of maximum, the approach condition. At engine speeds above 65% of maximum, the jet noise dominates in the far field, greatly exceeding that of the core. From coherence measurements, it is shown that the combustor is the dominant source of the low frequency core noise. The results obtained from the JT15D engine were compared with those obtained previously from a YF102 engine, both engines having reverse flow annular combustors and being in the same size class.

Experimental evaluation of a spinning-mode acoustic-treatment design concept for aircraft inlets. [suppression of YF-102 engine fan noise

Abstract: An aircraft-inlet noise suppressor method based on mode cutoff ratio was qualitatively checked by testing a series of liners on a YF-102 turbofan engine. Far-field directivity of the blade passing frequency was used extensively to evaluate the results. The trends and observations of the test data lend much qualitative support to the design method. The best of the BPF liners attained a suppression at design frequency of 19 dB per unit length-diameter ratio. The best multiple-pure-tone linear attained a remarkable suppression of 65.6 bB per unit length-diameter ratio.

Core noise investigation of the CF6-50 turbofan engine

Abstract: The contribution of the standard production annular combustor to the far-field noise signature of the CF6-50 engine was investigated. Internal source locations were studied. Transfer functions were determined for selected pairs of combustor sensors and from two internal sensors to the air field. The coherent output power was determined in the far-field measurements, and comparisons of measured overall power level were made with component and engine correlating parameters.

Comparison of several inflow control devices for flight simulation of fan tone noise using a JT15D-1 engine

Abstract: The paper describes the tests of four devices intended to reduce inflow disturbances and turbulences using a JT15D-1 turbofan engine. The tests were made to simulate the in-flight fan tone noise; the inflow control devices (ICD's) consisted of honeycomb/screen structures mounted over the engine inlet. The ICD's ranged from 1.6 to 4 fan diameters in size, and were made with several fabrication methods. All the ICD's significantly reduced the BPF tone in the far-field directivity patterns, but the smallest ICD's introduced propagating modes which could be recognized by additional lobes in the patterns. The JT15D-1 engine had a tone source which generated a strong propagating mode at fan speeds corresponding to 'approach' power and higher. Data from a typical transducer showed that the unsteady inflow distortion modes were eliminated or reduced when either of the ICD's was installed.

Control system for an augmented turbofan engine

Abstract: The engine includes a main engine fuel flow, an augmentation fuel flow, and a variable area exhaust nozzle. Primary speed control means is powered by first electrical power supply means. Fan speed is controlled by modulation of main engine fuel flow. Loss of electrical power to the primary speed control means during augmented operation results in a reversion from fan speed control to core engine speed control while simultaneously reducing the augmentation fuel flow toward a minimum level and closing the variable area exhaust nozzle. Backup speed control means is coupled to the primary speed control means for limiting fan overspeed in augmented operation during loss of electrical power to the primary speed control means. The backup speed control means is powered by second electrical power supply means which is independent of the first power supply means. For example, in one embodiment involving aircraft application, the first electrical power supply means comprises an engine-driven alternator and the second electrical power supply means comprises an aircraft positioned power supply. The primary and backup speed control means may be coupled to separate windings of a single torque motor.

Energy efficient engine: Fan test hardware detailed design report

Abstract: A single stage fan and quarter stage booster were designed for the energy efficient engine. The fan has an inlet radius ratio of 0.342 and a specific flow rate of 208.9 Kg/S sq m (42.8 lbm/sec sq ft). The fan rotor has 32 medium aspect ratio (2.597) titanium blades with a partspan shroud at 55% blade height. The design corrected fan tip speed is 411.5 M/S (1350 ft/sec). The quarter stage island splits the total fan flow with approximately 22% of the flow being supercharged by the quarter stage rotor. The fan bypass ratio is 6.8. The core flow total pressure ratio is 1.67 and the fan bypass pressure ratio is 1.65. The design details of the fan and booster blading, and the fan frame and static structure for the fan configuration are presented.

Status of NASA full-scale engine aeroelasticity research

Abstract: Data relevant to several types of aeroelastic instabilities were obtained using several types of turbojet and turbofan engines In particular, data relative to separated flow (stall) flutter, choke flutter, and system mode instabilities are presented The unique characteristics of these instabilities are discussed, and a number of correlations are presented that help identify the nature of the phenomena

Compression relief retarders for supercharged internal combustion engines

Abstract: An engine braking system is provided for an internal combustion engine of the Otto or Diesel type fitted with an exhaust gas supercharger and an air-to-air intercooler driven by a turbofan and having a gas compression relief type of engine brake. A control valve is provided in the gas flow passage communicating with the turbofan which drives the air-to-air intercooler using air compressed by the supercharger. The control valve is actuated automatically to inhibit flow of air through the turbofan whenever the gas compression relief engine brake is operated.

Potential benefits for propfan technology on derivatives of future short- to medium-range transport aircraft

Abstract: It is noted that several NASA-sponsored studies have identified a substantial potential fuel savings for high subsonic speed aircraft utilizing the propfan concept compared to the equivalent technology turbofan aircraft. Attention is given to a feasibility study for propfan-powered short- to medium-haul commercial transport aircraft conducted to evaluate potential fuel savings and identify critical technology requirements using the latest propfan performance data. An analysis is made of the design and performance characteristics of a wing-mounted and two-aft-mounted derivative propfan aircraft configurations, based on a DC-9 Super 80 airframe, which are compared to the baseline turbofan design. Finally, recommendations for further research efforts are also made.

Experimental evaluation of a spinning-mode acoustic-treatment design concept for aircraft inlets

Abstract: An aircraft-inlet noise suppressor method based on mode cutoff ratio was qualitatively checked by testing a series of liners on a YF-102 turbofan engine. Far-field directivity of the blade passing frequency was used extensively to evaluate the results. The trends and observations of the test data lend much qualitative support to the design method. The best of the BPF liners attained a suppression at design frequency of 19 dB per unit length-diameter ratio. The best multiple-pure-tone linear attained a remarkable suppression of 65.6 bB per unit length-diameter ratio.

Analytical study of the effects of wind tunnel turbulence on turbofan rotor noise

Abstract: An analytical study of the effects of wind tunnel turbulence on turbofan rotor noise was carried out to evaluate the effectiveness of the NASA Ames 40 by 80-foot wind tunnel in simulating flight levels of fan noise. A previously developed theory for predicting rotor/turbulence interaction noise, refined and extended to include first-order effects of inlet turbulence anisotropy, was employed to carry out a parametric study of the effects of fan size, blade number, and operating line for outdoor test stand, NASA Ames wind tunnel, and flight inlet turbulence conditions. A major result of this study is that although wind tunnel rotor/turbulence noise levels are not as low as flight levels, they are substantially lower than the outdoor test stand levels and do not mask other sources of fan noise.

Results From Tests on a High Work Transonic Turbine for an Energy Efficient Engine

Abstract: The experimental results of the evaluation of two high work, transonic, single-stage turbines investigated under the Energy Efficient Engine (E3) Program are presented. The objective of the E3 program is to provide an advanced technology base for a new generation of fuel-conservative turbofan engines. A single-stage turbine required fewer cooled airfoils, a reduced number of leakage paths and no interstage seals. These advanced energy efficient engines require high engine pressure ratios resulting in high expansion ratio, transonic, turbine designs which must have high aerodynamic efficiency. The goal of the turbine program is to develop a high pressure turbine that is compatible with the overall engine design and has an uncooled efficiency of 90.8 percent.

Acoustic characteristics of two hybrid inlets at forward speed

Abstract: A wind tunnel investigation of the acoustic and aerodynamic characteristics of two hybrid inlets installed on a JT15D-1 turbofan engine was performed. The hybrid inlets combined moderate throat Mach number and wall acoustic treatment to suppress the fan inlet noise. Acoustic and aerodynamic data were recorded over a range of flight and engine operating conditions. In a simulated flight environment, the hybrid inlets provided significant levels of suppression at both design and off-design throat Mach numbers with good aerodynamic performance. A comparison of inlet noise at quasi-static and forward-speed conditions in the wind tunnel showed a reduction in the fan tones, demonstrating the flight cleanup effect. High angles of attack produced slight increases in fan noise at the high acoustic directivity angles.

Twin-Jet Noise Shielding for a Supersonic Cruise Vehicle

Abstract: An engine arrangement for a supersonic cruise vehicle (SCV) has been developed that shows promise for jet noise reduction without the performance penalties associated with mechanical suppressors and engine oversizing. This arrangement, wherein two engines are placed on top of the wing directly above two similarly-mounted engines below the wing, can produce 3 to 5 dB less noise below the aircraft flight path than when four engines are installed under the wing. This noise reduction is due to acoustic shielding of the upper jets by the lower jets. Test data are reviewed to verify this acoustical shielding phenomenon, and detailed takeoff trajectories are calculated to show the effects of sideline and flyover noise levels on constraining maximum range SCV configurations. Engine placement variation and differential throttling, wherein thrust is unloaded from the lower engine and added to the upper engine, are to be explored as means for maximizing the shielding effect.

Type A V/STOL Propulsion System Development

Abstract: Design and performance considerations associated with the development of a unique Type A V/STOL fourturbofan propulsion system concept are described. This propulsion system uses fixed horizontal nacelles with thrust vectoring nozzles installed for achieving lift, a coaxial fan flow reaction control system for pitch control and trim, and a reaction control system for roll and yaw control and engine-out roll trim. The turbofan engine is specially designed to provide continuous compressor bleed flow for the reaction control system during vertical flight while achieving low specific fuel consumption during conventional flight modes. Critical propulsion system sizing conditions are identified, and the sensitivity of aircraft takeoff gross weight to changes in control criteria requirements, engine cycle parameters, and engine rating schemes are discussed. In addition to having competitive performance characteristics, the propulsion system concept described herein has zero single-point failures, low development cost and risk, and good reliability /maintainability.

Future Trends in Subsonic Transport Energy Efficient Turbofan Engines

Abstract: Details of the NASA sponsored General Electric Energy Efficient Engine (E3) technology program are presented along with a description of the engine, cycle and aircraft system benefits. Opportunities for further performance improvement beyond E3 are examined. Studies leading to the selection of the E3 cycle and configuration are summarized. The advanced technology features, cycle and component performance levels are also presented. An evaluation of the benefits of the fully developed Flight Propulsion System (FPS) is made relative to the NASA program goals by comparing the FPS with the CF6-50C where both are installed in advanced subsonic transport aircraft. Results indicate that a mission fuel saving from 15 to 23 percent is possible depending on mission length.Copyright © 1980 by ASME

Multiple Application Core Engine: Sizing and Usage Criteria

Abstract: Significant aircraft and propulsion system life-cycle cost savings may be realized by designing, developing, and maturing an advanced technology engine core (high-pressure rotor) for multiple application in a number of different aircraft types. Should the concept of a multiple application core engine (MACE) be proven feasible, common core development can be started separately from the aircraft system in a low-risk program free from flight test milestone pressure. Such a program would enable early durability testing of high temperature components with attendant earlier engine maturity and improved operational readiness. Each successive engine derived from this common core could be developed at significant cost savings compared to a completely new engine. This paper documents a study conducted at Pratt & Whitney Aircraft during 1978-1979 in which several turbojet and turbofan engines were configured around a common core design by adapting appropriate fans and/or low-pressure compressors. Core sizing and usage criteria are discussed along with preliminary but encouraging airframe contractor application analyses which indicate that a more detailed investigation of the MACE concept is warranted.

Core noise measurements on a small, general aviation class turbofan engine

Abstract: As part of a program to investigate core and combustor noise, simultaneous measurements were made of internal fluctuating pressure and farfield noise on a JT‐15D turbofan engine. Acoustic waveguide probes, located in the engine at the combustor, in the turbine exit and in the core nozzle, were used to measure internal fluctuating pressures. Low‐frequency acoustic power determined at the core nozzle exit corresponds in level to the farfield acoustic power at engine speeds below 70% of maximum, the approach condition. At engine speeds above 70% of maximum, the jet noise dominates in the farfield, greatly exceeding that of the core. From coherence measurements, it is shown that the combustor is the dominant source of the low‐frequency core noise. The results obtained from the JT‐15D engine compare favorably with those obtained previously from a YF‐102 engine, both engines having reverse flow annular combustors and being in the same size class.

Small gas turbofan engine with regenerating diffuser

Abstract: A mixed flow, high bypass, gas turbofan engine that is small and compact, and that develops a thrust in the range of approximately 200-300 pounds. The engine has an axial length of approximately 18 inches, an air inlet of approximately 10 inches in diameter, and an exhaust nozzle of approximately 6 inches in diameter. To reduce engine length high pressure compressor diameter, a high pressure compressor is positioned in a location that is displaced from and is preferably parallel to the engine axis (i.e., centerline), a burner (i.e., combustion chamber) is similarly positioned on the other side of the engine axis, only one turbine is used, and a unique flow path also is used. In addition, a heat exchanger of the regenerative type which includes a plurality of pipe diffusers is used, and it is positioned in the hot exhaust flow of the single turbine to pre-heat the compressor air prior to entry into the burner. Further, a gear shift may be used with the compressor to give better part-power performance. The small size, the thrust capability, and the good fuel consumption during part-power operation, make this engine ideal for use in air-launched cruise missiles.

Performance deterioration of commercial high-bypass ratio turbofan engines

Abstract: The results of engine performance deterioration investigations based on historical data, special engine tests, and specific tests to define the influence of flight loads and component clearances on performance are presented. The results of analyses of several damage mechanisms that contribute to performance deterioration such as blade tip rubs, airfoil surface roughness and erosion, and thermal distortion are also included. The significance of these damage mechanisms on component and overall engine performance is discussed.

Reverse thrust performance of the QCSEE variable pitch turbofan engine

Abstract: Results of steady state reverse and forward to reverse thrust transient performance tests are presented. The original quiet, clean, short haul, experimental engine four segment variable fan nozzle was retested in reverse and compared with a continuous, 30 deg half angle conical exlet. Data indicated that the significantly more stable, higher pressure recovery flow with the fixed 30 deg exlet resulted in lower engine vibrations, lower fan blade stress, and approximately a 20 percent improvement in reverse thrust. Objective reverse thrust of 35 percent of takeoff thrust was reached. Thrust response of less than 1.5 sec was achieved for the approach and the takeoff to reverse thrust transients.

Preparing aircraft propulsion for a new era in energy and the environment

Abstract: Improving fuel efficiency, new sources of jet fuel, and noise and emission control are subjects of NASA's aeronautics program. Projects aimed at attaining a 5% fuel savings for existing engines and a 13-22% savings for the next generation of turbofan engines using advanced components, and establishing a basis for turboprop-powered commercial air transports with 30-40% savings over conventional turbofan aircraft at comparable speeds and altitudes, are discussed. Fuel sources are considered in terms of reduced hydrogen and higher aromatic contents and resultant higher liner temperatures, and attention is given to lean burning, improved fuel atomization, higher freezing-point fuel, and deriving jet fuel from shale oil or coal. Noise sources including the fan, turbine, combustion process, and flow over internal struts, and attenuation using acoustic treatment, are discussed, while near-term reduction of polluting gaseous emissions at both low and high power, and far-term defining of the minimum gaseous-pollutant levels possible from turbine engines are also under study.

The Energy Efficient Engine (E3): Advancing the State of the Art

Abstract: The NASA-sponsored Energy Efficient Engine (E3) Program, intended to develop and demonstrate the technology for reducing fuel consumption in future environmentally acceptable turbofan engines, is presented. The development of the flight propulsion system design is outlined and the resulting preliminary design is presented. Component design and subcomponent supporting technology verification work in progress is discussed, with attention given to fabrication development, the transition duct, mixer design, the fan, the high-pressure compressor, the combustor, and the high-pressure turbine. It is noted that the detailed design of the core components is essentially complete and fabrication of the hardware has begun, with the program on schedule toward testing in 1982.

Design and evaluation of an integrated Quiet, Clean General Aviation Turbofan (QCGAT) engine and aircraft propulsion system

Abstract: The design was based on the LTS-101 engine family for the core engine. A high bypass fan design (BPR=9.4) was incorporated to provide reduced fuel consumption for the design mission. All acoustic and pollutant emissions goals were achieved. A discussion of the preliminary design of a business jet suitable for the developed propulsion system is included. It is concluded that large engine technology can be successfully applied to small turbofans, and noise or pollutant levels need not be constraints for the design of future small general aviation turbofan engines.