SEARCH · Search NASA

Results for “bypass ratio”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

NASA NTRS1982

Nacelle Aerodynamic and Inertial Loads (NAIL) project

Inlet airloads were measured by integration of pressures recorded at 252 locations on the right hand inboard (JT9D-7A) nacelle of the Boeing 747 aircraft. Pressures were recorded at 45 locations on the right hand outboard nacelle for comparison. Inertial loads were measured on both nacelles using accelerometers and rate gyros. Flight conditions included takeoffs at several gross weights, high g turns, and a simulated acceptance flight. Airloads at takeoff rotation were found to be larger than at any other normal service condition because of the combined effects of high angle of attack and high engine airflow. Inertial loads were smaller than previous estimates had indicated. A procedure is given for estimating inlet airloads at low speeds and high angles of attack for any underwing high bypass ratio turbofan installation approximately resembling the one tested. Flight procedure modifications are suggested that may result in better fuel economy retention in service. Pressures were recorded on the core cowls and pylons of both engine installations and on adjacent wing surfaces for use in development of computer codes for analysis of installed propulsion system aerodynamic drag interference effects.

Source record↗

NASA NTRS1984

Investigation of mixing in a turbofan exhaust duct. II Computer code application and verification

A three-dimensional analysis of turbofan forced mixer nozzle aerodynamics demonstrates that the complex flow structure is dominated by geometrically induced secondary flow rather than by turbulence. The test apparatus consisted of a fixed upstream model section and a rotating shroud. The Mach number of the fan and core streams at the mixing plane (lobe exit) was 0.45, the bypass ratio was about 4, and the Reynolds number based on the shroud radius was 1,100,000. The three velocity components near the exit plane of the lobes were measured using flow angularity probes to provide information about the mixer inflow conditions for turbulent computations. The validity of a previous computer code was demonstrated in a comparison of the nozzle exit temperature data with the computed temperature distributions. The mechanism most responsible for the generation of secondary flow within the lobes is due to the turning of the fan and core streams in opposite radial directions.

Povinelli, L. A.↗

NASA NTRS1984

Optimization and mechanisms of mistuning in cascades

In the present inverse design procedure for the optimum mistuning of a high bypass ratio shroudless fan that is modeled as a cascade of blades (each with a single torsional degree-of-freedom), linearized supersonic aerodynamic theory is used to compute the unsteady aerodynamic forces in the 'influence coefficient' form at a typical blade section. The mistuning pattern is then numerically optimized in order to achieve a specified increase in the aeroelastic stability margin with a minimum amount of mistuning. If the blades are self-damped, an optimized mistuning pattern can be found that achieves a given stability margin for a much lower level of mistuning than required for the alternate mistuning pattern, which requires only two blade frequencies and is relatively insensitive to implementation errors.

Crawley, E. F.↗

NASA NTRS1985

Preliminary performance of a vertical-attitude takeoff and landing, supersonic cruise aircraft concept having thrust vectoring integrated into the flight control system

A performance study was made of a vertical attitude takeoff and landing (VATOL), supersonic cruise aircraft concept having thrust vectoring integrated into the flight control system. Those characteristics considered were aerodynamics, weight, balance, and performance. Preliminary results indicate that high levels of supersonic aerodynamic performance can be achieved. Further, with the assumption of an advanced (1985 technology readiness) low bypass ratio turbofan engine and advanced structures, excellent mission performance capability is indicated.

Robins, A. W.↗

NASA NTRS1985

Structural response of a rotating bladed disk to rotor whirl

A set of high speed rotating whirl experiments were performed in the vacuum of the MIT Blowdown Compressor Facility on the MIT Aeroelastic Rotor, which is structurally typical of a modern high bypass ratio turbofan stage. These tests identified the natural frequencies of whirl of the rotor system by forcing its response using an electromagnetic shaker whirl excitation system. The excitation was slowly swept in frequency at constant amplitude for several constant rotor speeds in both a forward and backward whirl direction. The natural frequencies of whirl determined by these experiments were compared to those predicted by an analytical 6 DOF model of a flexible blade-rigid disk-flexible shaft rotor. The model is also presented in terms of nondimensional parameters in order to assess the importance of the interation between the bladed disk dynamics and the shaft-disk dynamics. The correlation between the experimental and predicted natural frequencies is reasonable, given the uncertainty involved in determining the stiffness parameters of the system.

Crawley, E. F.↗

NASA NTRS1986

HYTESS-Hypothetical Turbofan-Engine Simplified Simulation

Simulated characteristics mimic those of advanced turbofan engines. Computer program developed to offer those interested in engine dynamics and controls research efficient, realistic, and easily-used engine simulation. Simulation developed from linearized operating-point models but still retains essential nonlinear engine effects. Representative of hypothetical, low-bypass-ratio, twin-spool, axialflow turbofan engine. Program written in FORTRAN IV.

Merrill, W.↗

NASA NTRS1986

Effect of emerging technology on a convertible, business/interceptor, supersonic-cruise jet

This study was initiated to assess the feasibility of an eight-passenger, supersonic-cruise long range business jet aircraft that could be converted into a military missile carrying interceptor. The baseline passenger version has a flight crew of two with cabin space for four rows of two passenger seats plus baggage and lavatory room in the aft cabin. The ramp weight is 61,600 pounds with an internal fuel capacity of 30,904 pounds. Utilizing an improved version of a current technology low-bypass ratio turbofan engine, range is 3,622 nautical miles at Mach 2.0 cruise and standard day operating conditions. Balanced field takeoff distance is 6,600 feet and landing distance is 5,170 feet at 44,737 pounds. The passenger section from aft of the flight crew station to the aft pressure bulkhead in the cabin was modified for the interceptor version. Bomb bay type doors were added and volume is sufficient for four advanced air-to-air missiles mounted on a rotary launcher. Missile volume was based on a Phoenix type missile with a weight of 910 pounds per missile for a total payload weight of 3,640 pounds. Structural and equipment weights were adjusted and result in a ramp weight of 63,246 pounds with a fuel load of 30,938 pounds. Based on a typical intercept mission flight profile, the resulting radius is 1,609 nautical miles at a cruise Mach number of 2.0.

Beissner, F. L., Jr.↗

NASA NTRS1986

HYTESS 2: A Hypothetical Turbofan Engine Simplified Simulation with multivariable control and sensor analytical redundancy

A hypothetical turbofan engine simplified simulation with a multivariable control and sensor failure detection, isolation, and accommodation logic (HYTESS II) is presented. The digital program, written in FORTRAN, is self-contained, efficient, realistic and easily used. Simulated engine dynamics were developed from linearized operating point models. However, essential nonlinear effects are retained. The simulation is representative of the hypothetical, low bypass ratio turbofan engine with an advanced control and failure detection logic. Included is a description of the engine dynamics, the control algorithm, and the sensor failure detection logic. Details of the simulation including block diagrams, variable descriptions, common block definitions, subroutine descriptions, and input requirements are given. Example simulation results are also presented.

Merrill, W. C.↗

NASA NTRS1986

Transient engine performance with water ingestion

The immediate effects on the transient performance of a generic, high bypass ratio jet engine on account of water ingestion are discussed. The air compression subsystem has been analyzed with respect to four aerothermodynamic and mechanical processes associated with two-phase fluid flow and the engine simulation has been carried out under three limiting cases of interest in practice, one pertaining to draining of water at the end of compression and the other two, to partial evaporation at two different locations in the burner. General observations are made on engine operability as a function of engine and control design under various engine and (control input) sensor operating conditions, with various mass fractions of water in the air-water mixture entering the engine, during various pilot-initiated power demand changes.

Haykin, T.↗

NASA NTRS1986

Analytical and experimental investigation of the coupled bladed disk/shaft whirl of a cantilevered turbofan

A simple analytical model for the structural dynamics of a rotating flexible blade/rigid disk/flexible cantilevered shaft system yields the equations of motion expressed in the rotating frame, showing that the blade's one-nodal diameter modes dynamically couple to the rigid body whirling motion of the shaft-disk system. This analytical model is correlated with the results of a structural dynamic experiment performed on an aeroelastic rotor fan that is similar to a high bypass ratio shroudless turbofan. The agreement between the predicted and experimental natural frequencies is good, and suggests significant interaction of the one-nodal diameter blade modes with the shaft-disk modes.

Crawley, E. F.↗

NASA NTRS1986

Numerical study of combustion processes in afterburners

Mathematical models and numerical methods are presented for computer modeling of aeroengine afterburners. A computer code GEMCHIP is described briefly. The algorithms SIMPLER, for gas flow predictions, and DROPLET, for droplet flow calculations, are incorporated in this code. The block correction technique is adopted to facilitate convergence. The method of handling irregular shapes of combustors and flameholders is described. The predicted results for a low-bypass-ratio turbofan afterburner in the cases of gaseous combustion and multiphase spray combustion are provided and analyzed, and engineering guides for afterburner optimization are presented.

Zhou, Xiaoqing↗

NASA NTRS1985

Advanced Propfan Engine Technology (APET) and Single-rotation Gearbox/Pitch Change Mechanism

The projected performance, in the 1990's time period, of the equivalent technology level high bypass ratio turbofan powered aircraft (at the 150 passenger size) is compared with advanced turboprop propulsion systems. Fuel burn analysis, economic analysis, and pollution (noise, emissions) estimates were made. Three different cruise Mach numbers were investigated for both the turbofan and the turboprop systems. Aerodynamic design and performance estimates were made for nacelles, inlets, and exhaust systems. Air to oil heat exchangers were investigated for oil cooling advanced gearboxes at the 12,500 SHP level. The results and conclusions are positive in that high speed turboprop aircraft will exhibit superior fuel burn characteristics and lower operating costs when compared with equivalent technology turbofan aircraft.

Sargisson, D. F.↗

NASA NTRS1987

Civil propulsion technology for the next twenty-five years

The next twenty-five years will see major advances in civil propulsion technology that will result in completely new aircraft systems for domestic, international, commuter and high-speed transports. These aircraft will include advanced aerodynamic, structural, and avionic technologies resulting in major new system capabilities and economic improvements. Propulsion technologies will include high-speed turboprops in the near term, very high bypass ratio turbofans, high efficiency small engines and advanced cycles utilizing high temperature materials for high-speed propulsion. Key fundamental enabling technologies include increased temperature capability and advanced design methods. Increased temperature capability will be based on improved composite materials such as metal matrix, intermetallics, ceramics, and carbon/carbon as well as advanced heat transfer techniques. Advanced design methods will make use of advances in internal computational fluid mechanics, reacting flow computation, computational structural mechanics and computational chemistry. The combination of advanced enabling technologies, new propulsion concepts and advanced control approaches will provide major improvements in civil aircraft.

Rosen, Robert↗

NASA NTRS1988

Euler analysis of a swirl recovery vane design for use with an advanced single-rotation propfan

Recent work has demonstrated the propulsive efficiency improvement available from single- and counter-rotation propfans as compared with current technology high bypass ratio turbofans. The concept known as swirl recovery vanes (SRV) is examined through the use of a 3-D Euler code. At high speed cruise conditions, the SRV can improve the efficiency level of a single-rotation propfan, but a concern is to have adequate hub choke margin. The SRV was designed with 2-D methods and was predicted to have hub choking at Mach 0.8 cruise. The 3-D Euler analysis properly accounts for sweep effects and 3-D relief, and predicts that at cruise the SRV will recover roughly 5 percent of the 10 percent efficiency loss due to swirl and have a good hub choke margin.

Miller, Christopher J.↗

NASA NTRS1988

Euler analysis of a swirl recovery vane design for use with an advanced single-rotation propfan

Miller, Christopher J.↗

NASA NTRS1989

Effect of heavy rain on aviation engines

High bypass ratio gas turbine engines may ingest water and hail during flight in an environment of thunderstorms, and the performance and the operation-handling characteristics of the engine and its control become affected often substantially and critically. It is, therefore, of interest to establish predictive schemes for determining changes in performance of components and the total system. The current status of development of such predictive schemes is discussed along with illustrative examples. The needs for additional research are discussed, that are essential for improving: (1) the predictive schemes and (2) the methods of simulating in-rain flight conditions on ground.

Murthy, S. N. B.↗

NASA NTRS1985

Energy Efficient Engine Program Advanced Turbofan Nacelle Definition Study

Advanced, low drag, nacelle configurations were defined for some of the more promising propulsion systems identified in the earlier Benefit/Cost Study, to assess the benefits associated with these advanced technology nacelles and formulate programs for developing these nacelles and low volume thrust reversers/spoilers to a state of technology readiness in the early 1990's. The study results established the design feasibility of advanced technology, slim line nacelles applicable to advanced technology, high bypass ratio turbofan engines. Design feasibility was also established for two low volume thrust reverse/spoiler concepts that meet or exceed the required effectiveness for these engines. These nacelle and thrust reverse/spoiler designs were shown to be applicable in engines with takeoff thrust sizes ranging from 24,000 to 60,000 pounds. The reduced weight, drag, and cost of the advanced technology nacelle installations relative to current technology nacelles offer a mission fuel burn savings ranging from 3.0 to 4.5 percent and direct operating cost plus interest improvements from 1.6 to 2.2 percent.

Howe, David C.↗

NASA NTRS1990

NASA's HITEMP program for UHBR engines

NASA's High Temperature Engine Materials Program (HITEMP) is concerned with the laboratory-scale technology development and feasibility demonstration of high-temperature composite materials, in conjunction with the requisite structural analysis models and test methods for their validation. HITEMP encompasses research on metallic/intermetallic, ceramic, and polymer matrix composites, and is giving attention to high-temperature component composites applicable to future widebody commercial aircraft ultrahigh bypass ratio (UHBR) engines. The UHBR components for which advanced composites are envisioned are fan, compressor, and turbine rotor blades, stator vanes, disks, and shafts, thrust bearings, gearbox bearings and linings, combustor cases and linings, nacelles, and thrust-reversers.

Stephens, Joseph R.↗