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Showing papers on "Turbofan published in 1986"


Journal ArticleDOI
TL;DR: In this paper, a single microphone output is de-Dopplerized, and results from a Lockheed TriStar graphically illustrate the capability of the de-dopplerization for the analysis of noise from counterrotating propeller driven aircraft.

87 citations


Journal ArticleDOI
TL;DR: In this article, a linear-quadratic Gaussian with loop-transfer recovery (LQG/LTR) design methodology for multivariable feedback control for the F-100 turbofan jet engine is presented.
Abstract: The design of a multivariable feedback control system for the F-100 turbofan jet engine is a challenging task for control engineers. This paper employs a linearized model of the F-100 engine to demonstrate the use of the newly developed linear-quadratic Gaussian with loop-transfer recovery design methodology that adopts an in- tegrated frequency and time-domain approach to multivariable feedback control synthesis so as to meet stability robustness, command following, and disturbance rejection specifications. ODERN turbofan jet engines represent an important multiple-input/multiple-output (MIMO) control ap- plication area since the dynamic coordination of fuel flow and several engine geometry variables can lead to improved performance and efficiency, while maintaining safe fan and compression stall margins. Indeed, the MIMO feedback con- trol of turbofan and turboshaft engine has received a great deal of attention in the past few years.1"8 The F-100 turbofan engine was used as a main design exam- ple for which different MIMO control methodologies were employed. The so-called linear-quadratic-regulator (LQR) ap- proach9'10 was the basis of engineering designs and evaluations1"4 that required the feedback of several F-100 state variables. In the past five years significant advances have been made in integrating time-domain optimization-based approaches (such as LQR and linear-quadratic Gaussian (LQG)) with fre- quency domain approaches. Such an integrated frequency- domain and state-space approach to MIMO control systems design was pioneered by Stein and his colleagues11"14 and has culminated to the so-called linear-quadratic Gaussian with loop-transfer recovery (LQG/LTR) methodology for MIMO feedback control synthesis. The primary objective of this paper is to illustrate the LQG/LTR design methodology using a four-input/fou r- output linear model of the F-100 engine. Specifically, we stress how MIMO command following and disturbance rejection performance specifications, as well as stability robustness specifications are naturally posed in the frequency domain us- ing the singular values of suitably defined loop-transfer matrices. Then, we demonstrate how the LQG/LTR design procedure is used to meet the posed specifications. Further-

85 citations


Journal ArticleDOI
TL;DR: An overview of the evolution of propfan aircraft design concepts and system studies can be found in this article, where a review of the NASA Aircraft Energy Efficiency (ACEE) program propfan projects with industry is reviewed with respect to system studies of propFan aircraft and recommended flight development programs.

19 citations


01 Mar 1986
TL;DR: In this paper, small advanced (450 to 850 pounds thrust, 2002 to 3781 N) gas turbine engines were studied for a subsonic strategic cruise missile application, using projected year 2000 technology.
Abstract: Small advanced (450 to 850 pounds thrust, 2002 to 3781 N) gas turbine engines were studied for a subsonic strategic cruise missile application, using projected year 2000 technology. An aircraft, mission characteristics, and baseline (state-of-the-art) engine were defined to evaluate technology benefits. Engine performance and configuration analyses were performed for two and three spool turbofan and propfan engine concepts. Mission and Life Cycle Cost (LCC) analyses were performed in which the candidate engines were compared to the baseline engines over a prescribed mission. The advanced technology engines reduced system LCC up to 41 percent relative to the baseline engine. Critical aerodynamic, materials, and mechanical systems turbine engine technologies were identified and program plans were defined for each identified critical technology.

16 citations


Patent
30 Apr 1986
TL;DR: A turbofan gas turbine engine comprises a forward fan 50 and a rear fan 80 arranged to rotate in opposite directions within a bypass duct as mentioned in this paper, and a combustor 16 is positioned axially between the forward and rearward fans, and may be stationary or with the first turbine drum rotor.
Abstract: A turbofan gas turbine engine comprises a forward fan 50 and a rearward fan 80 arranged to rotate in opposite directions within a bypass duct 22 The forward fan 50 is driven by a first drum rotor 42 of a compressor 14, the first drum rotor rotating in the same direction but at a relatively slower speed than a second drum rotor 52 of the compressor The rearward fan 80 is driven by a first turbine drum rotor 72 of a turbine 18, the first turbine drum rotor rotating in the opposite direction but at a relatively slower speed than a second turbine drum rotor 82 of the turbine The second turbine drum rotor is arranged to drive the second drum rotor of the compressor A combustor 16 is positioned axially between the forward and rearward fans, and may be stationary or arranged to rotate independently or with the first turbine drum rotor Contra-rotating propellers may be driven in a similar way

14 citations


Journal ArticleDOI
TL;DR: In this paper, a small disturbance formulation for the analysis of the inviscid flow over a turbofan forced mixer configuration in which the governing equations are reduced by means of a flux volume formulation along a Cartesian grid is presently extended to include the effects of power addition within the potential formulation.
Abstract: A small disturbance formulation for the three-dimensional potential analysis of the inviscid flow over a turbofan forced mixer configuration in which the governing equations are reduced by means of a flux volume formulation along a Cartesian grid is presently extended to include the effects of power addition within the potential formulation. Calculations are presented for practical turbofan mixer designs, and comparison calculations are also given with measured surface pressure distributions and measured axial velocity profiles.

13 citations


Patent
20 Aug 1986
TL;DR: In this paper, a core engine, a fan assembly and a booster compressor are positioned upstream of the core engine and the booster compressor 42 is positioned downstream of the fan assembly, and a planet carrier 62 of the gear assembly 54 is connected, at its downstream end to a core casing 22 and a stator casing 45 of the booster compressors.
Abstract: A geared turbofan gas turbine engine comprises a core engine (12 Figure 1), a fan assembly 24 and a booster compressor 42. The fan assembly 24 is positioned upstream of the core engine and the booster compressor 42 is positioned upstream of the fan assembly 24. The fan assembly is driven by the turbines of the core engine via a gear assembly 54 and a rotor 44 of the booster compressor is driven by the turbines of the core engine. A planet carrier 62 of the gear assembly 54 is connected, at its downstream end to a core casing 22 of the core engine, at its upstream end to a stator casing 45 of the booster compressor 42.

12 citations



Patent
19 Nov 1986
TL;DR: In this paper, a portion of the bypass air is extracted from the bypass flow through apertures and disposed in the inner wall of a bypass duct in the vicinity of the turbine housing.
Abstract: A portion of the bypass air is extracted from the bypass flow through apertures 11 disposed in the inner wall 12 of the bypass duct in the vicinity of the turbine housing. The arrangement may include valve means (39 and see Figs. 8 and 9, not shown) for controlling cooling flow under certain conditions.

11 citations


Proceedings ArticleDOI
18 Jun 1986
TL;DR: Improvements made to the ADIA algorithm and implementation are discussed, and the results of an evaluation are presented that used a real-time, hybrid computer simulation of an F100 turbofan engine.
Abstract: An Advanced sensor failure Detection, Isolation, and Accommodation (ADIA) algorithm has been developed for use with an aircraft turbofan engine control system. In a previous paper the authors described the ADIA algorithm and its real-time implementation. This paper discusses subsequent improvements made to the algorithm and implementation, and presents the results of an evaluation. The evaluation used a real-time, hybrid computer simulation of an F100 turbofan engine.

10 citations


Proceedings ArticleDOI
01 Jan 1986
TL;DR: In this article, an experimental study of the flow field of heated and unheated single and dual jet configurations was performed. But this study of two parallel jets is unique since most previous aerodynamic structure experiments were limited to single round and two-dimensional jets.
Abstract: An experimental study of the flowfield of heated and unheated single and dual jet configurations was performed. This study of two parallel jets is unique since most previous aerodynamic structure experiments were limited to single round and two-dimensional jets. The present closely spaced dual jet geometry was motivated by the potential jet noise reduction available from this configuration. This geometry has shown promise as a method for redirecting jet noise away from ground based observers in side by side or over/under turbofan engine mountings on aircraft (Simonich et al., 1984). Since the effectiveness of this noise reduction technique is based on the existence of two independent jets, an understanding of the aerodynamics of the merging process is essential to establishing the acoustic benefits. The experimental program was structured so that Mach number, jet exit temperature, and spacing to diameter ratios could be independently varied to isolate each effect.

Book
01 Jan 1986
TL;DR: In this article, numerical methods for engine-airframe integration are presented, including numerical solutions of the compressible Navier-Stokes equations, elements of computational engine/airframe integrations, computational requirements for efficient engine installation, application of CAE and CFD techniques to complete tactical missile design, and application of a second-generation low-order panel methods to powerplant installation studies.
Abstract: Various papers on numerical methods for engine-airframe integration are presented. The individual topics considered include: scientific computing environment for the 1980s, overview of prediction of complex turbulent flows, numerical solutions of the compressible Navier-Stokes equations, elements of computational engine/airframe integrations, computational requirements for efficient engine installation, application of CAE and CFD techniques to complete tactical missile design, CFD applications to engine/airframe integration, and application of a second-generation low-order panel methods to powerplant installation studies. Also addressed are: three-dimensional flow analysis of turboprop inlet and nacelle configurations, application of computational methods to the design of large turbofan engine nacelles, comparison of full potential and Euler solution algorithms for aeropropulsive flow field computations, subsonic/transonic, supersonic nozzle flows and nozzle integration, subsonic/transonic prediction capabilities for nozzle/afterbody configurations, three-dimensional viscous design methodology of supersonic inlet systems for advanced technology aircraft, and a user's technology assessment.

01 Jan 1986
TL;DR: In this paper, the measurement error or uncertainty of in-flight thrust determination in aircraft employing conventional turbofan/turbojet engines is reviewed, and the present text is divided into the following categories: measurement uncertainty methodoogy and inflight thrust measurent processes.
Abstract: Methods for estimating the measurement error or uncertainty of in-flight thrust determination in aircraft employing conventional turbofan/turbojet engines are reviewed. While the term 'in-flight thrust determination' is used synonymously with 'in-flight thrust measurement', in-flight thrust is not directly measured but is determined or calculated using mathematical modeling relationships between in-flight thrust and various direct measurements of physical quantities. The in-flight thrust determination process incorporates both ground testing and flight testing. The present text is divided into the following categories: measurement uncertainty methodoogy and in-flight thrust measurent processes.

01 Jun 1986
TL;DR: In this paper, a comparative study was conducted to investigate the performance and cost benefits of future engine concepts for subsonic strategic cruise missile propulsion, and the results showed that the two engines require virtually the same size missile to fly the designated mission.
Abstract: A comparative study was conducted to investigate the performance and cost benefits of future engine concepts for subsonic strategic cruise missile propulsion. Technology advancements were projected for component efficiencies, materials and bearing lubrication. Engine configurations studied were an advanced simple cycle (conventional) turbofan and a recuperated turbofan. Results showed the two engines require virtually the same size missile to fly the designated mission. However, there was lower life cycle cost for the advanced simple cycle turbofan engine.

Proceedings ArticleDOI
16 Jun 1986
TL;DR: A joint development efnique (ATEST) is a digital computer simulation sysfort between AEDC and AFWAL has produced the tem for the prediction and correlation of both Advanced Turbine Engine Simulation Technique steady-state and transient engine performance.
Abstract: the high levels of accuracy provided by previous methods so that meaningful evaluations of engine performance can be made. A joint development efnique (ATEST) is a digital computer simulation sysfort between AEDC and AFWAL has produced the tem for the prediction and correlation of both Advanced Turbine Engine Simulation Technique steady-state and transient engine performance. (ATEST), a program that provides the required capaATEST has been developed using both a modular conbilities and reduces both computer execution time cept which provides the flexibility to simulate and memory requirements (as compared to other profied Newton-Raphson numerical method (matrix solver) to achieve convergence at both design and offDigital computer simulations of turbine endesign operating points. In addition, ATEST has gine systems have steadily progressed over the past the capability to treat the specialized charactertwo decades. In the mid-1960's the Simulation Of istics of a particular engine (turbine coaling air Turbofan Engine (SM0TE)l automated the calculation paths, Reynolds number effects, etc.) to the degree of steady-state off-design performance of singleof detail required by the user. The technique has and dual-spool turbofan engines. Later the Genbeen developed around a collection of the best eralized Engine Programs (GENENG I and GENENG features of current advanced engine simulations extended the capabilities of SMOTE to includethreeused in government and industry. ATEST is intended spool turbofans and both singleand dual-spool for aircraft gas turbine engine cycles (e.g., turbojets. The Dynamic Generalized Engine Program single-spool turbojet, high-bypass turbofan, vari(DYNGEN)4 then provided the capability to calculate able-cycle engine, etc.) but could also be used to both steady-state and transient turbine engine persimulate other physical systems, taking advantage formance for the same engine configurations that of the modular structure. The ATEST has been sucare available in GENENG 11. In the early 1970's cessfully applied to a number of different turbine the Navy Engine Performance Program (NEPCOMP)5'6 engine cycles. These cycles represent a wide specprovided the capability to calculate the steadytrum of the different types of aircraft gas turbine state off-design performance of arbitrary turbine engines and include a single-spool turbojet (579), engine cycles. A few years later the Navy-NASA a dual-spool turbojet (J57), dual-spool mixed-flow turbofans (F100, F110, F109, F404), a dual-spool NEPCOMP to include an optimization technique and a separate-flow turbofan (CFM56), a turboshaft engine technique to represent performance of variable(T64), and an unconventional cycle engine. The geometry components. In the early 1980's a program ATEST has been written in FORTRAN 77 and has been executed on a variety of digital computers, includbility of calculating transient performance for ing the AMDAHL 5860, CRAY-XMP, and CYBER 7600. arbitrary turbine engine cycles. TmBOTRANS also has a capability allowing the user to include a Introduction limited amount of engine control logic in a simulation. ATEST encompasses the capabilities of The Advanced Turbine Engine Simulation Techarbitrary engine cycle configurations and a modigrams). Engine Program (NNEP)7 extended the capabilities of called TURBOTRANS8 provided the additional capaBoth the Arnold Engineering Development NEPCOMP, NNEP, and TURBOTRANS and expands these Center (AEDC) and the Air Force Wright Aeronautical capabilities to simulate the intricacies of adLaborarories ( A N A L ) at Wright-Patterson Air Force vanced turbine engines. These i n t r i c a c i e s inc lude , Base (WAFB) require an advanced turbine engine but are not limited to, engine specific operational simulation that can be effectively configured to effects on component performance (e.g., low simulate bath steady-state and transient performReynolds number, active clearance control), multiance of any turbine engine cycle. This advanced ple bleed paths from individual components and method must be capable of simulating all of the ininter-component interactions (e.g., pressure losses tricacies of modern turbine engines (e.g., multiple and/or heat rejection between components). cooling bleed paths, active clearance control, and effects of low Reynolds number) i n order to Support both engine testing at AEDC and exploratory cycle analysis at AFWAL. This means that previous simuA generalized program capable of simulating lation techniques must be expanded to include these both steady-state and transient performance of arintricacies and improved to reduce both execution bitrary turbine engine cycles is required. The time requirements and computer memory requirements. capability to simulate the complexities of a speThe advanced simulation method must also maintain cific cycle (such as radial variations of fan *The research reported herein was performed by the Arnold Engineering Development Center (AEDC), Air Work and analysis for this research were done by personnel of Svrrdrup Technology, General ATEST Development Force Systems Command. Inc./AEDC Group, operating contractor fox the AEDC propulsion test facilities and of the Air Force Wright Aeronautical Laboratories. Government. Further reproduction is authorized to satisfy needs of the United States

Proceedings ArticleDOI
01 Jun 1986
TL;DR: In this paper, a study has been conducted for advanced small (450-850 pounds thrust) gas turbine engines for a subsonic strategic cruise missile application, using projected year-2000 technology.
Abstract: A study has been conducted for advanced small (450-850 pounds thrust) gas turbine engines for a subsonic strategic cruise missile application, using projected year-2000 technology. Engine performance and configuration analyses were performed for two and three spool turbofan and propfan engine concepts. Mission and Life Cycle Cost (LCC) analyses were performed in which the candidate engines were compared to the baseline engine over a prescribed mission. The advanced technology engines reduced system LCC up to 41 percent relative to the baseline engine. The critical aerodynamic materials and mechanical systems necessary for turbine engine technology were identified.

01 Dec 1986
TL;DR: An exhaust gas pressure and temperature survey of the General Electric F404-GE-400 turbofan engine was conducted in the altitude test facility of the NASA Lewis Propulsion System Laboratory as discussed by the authors.
Abstract: An exhaust-gas pressure and temperature survey of the General Electric F404-GE-400 turbofan engine was conducted in the altitude test facility of the NASA Lewis Propulsion System Laboratory. Traversals by a survey rake were made across the exhaust-nozzle exit to measure the pitot pressure and total temperature. Tests were performed at Mach 0.87 and a 24,000-ft altitude and at Mach 0.30 and a 30,000-ft altitude with various power settings from intermediate to maximum afterburning. Data yielded smooth pressure and temperature profiles with maximum jet temperatures approximately 1.4 in. inside the nozzle edge and maximum jet temperatures from 1 to 3 in. inside the edge. A low-pressure region located exactly at engine center was noted. The maximum temperature encountered was 3800 R.

01 Dec 1986
TL;DR: In this paper, a variable inlet guide van (VIGV) type convertible engine was tested on an outdoor stand to power future X-wing rotorcraft capable of 400-knot cruise speed.
Abstract: A variable inlet guide van (VIGV) type convertible engine that could be used to power future high-speed rotorcraft was tested on an outdoor stand. The engine ran stably and smoothly in the turbofan, turboshaft, and dual (combined fan and shaft) power modes. In the turbofan mode with the VIGV open fuel consumption was comparable to that of a conventional turbofan engine. In the turboshaft mode with the VIGV closed fuel consumption was higher than that of present turboshaft engines because power was wasted in churning fan-tip airflow. In dynamic performance tests with a specially built digital engine control and using a waterbrake dynamometer for shaft load, the engine responded effectively to large steps in thrust command and shaft torque. Previous mission analyses of a conceptual X-wing rotorcraft capable of 400-knot cruise speed were revised to account for more fan-tip churning power loss than was originally estimated. The new calculations confirm that using convertible engines rather than separate lift and cruise engines would result in a smaller, lighter craft with lower fuel use and direct operating cost.

Proceedings ArticleDOI
08 Jun 1986
TL;DR: In this article, the authors summarized current and projected heat management techniques within aircraft gas turbines, including the thermodynamic cycle sources of fuel combustion and air compression, and the parasitic sources of friction, oil churning and rotor windage.
Abstract: This paper summarizes current and projected heat management techniques within aircraft gas turbines. Each of the primary heat sources is individually considered, including the thermodynamic cycle sources of fuel combustion and air compression, and the parasitic sources of friction, oil churning and rotor windage. For each source, the problem is presented, and solutions — both present and future — are offered. Heat management within low spool reduction gearing is also discussed because of the high probability of an advanced high speed turboprop and geared high bypass ratio turbofan propulsion system in the future.Copyright © 1986 by ASME


Proceedings ArticleDOI
01 Jan 1986
TL;DR: In this paper, a parametric study was conducted to define candidate engine thermodynamic cycles for advanced long range aircraft, based on uninstalled cruise specific fuel consumption (SFC) for the year 2000 turbofan engine.
Abstract: To define the optimum turbofan engine cycle for the year 2000, a parametric study was undertaken to define candidate engine thermodynamic cycles for advanced long range aircraft. Performance comparisons are based on uninstalled cruise specific fuel consumption (SFC). A base cycle design with current state-of-the-art technology was established as a reference. A parametric study was then conducted where component technologies projected for the year 2000 were included in the cycle design process. As bypass ratio increased, the transition from direct drive to geared fans was accounted for. Separate versus mixed flow exhaust systems were also studied. An uninstalled SFC improvement of approximately 18 percent was found for the year 2000 turbofan relative to the baseline engine.

01 Jan 1986
TL;DR: In this article, the authors considered the modification of existing aircraft to the folding tilt rotor (FTR) design configuration, and then addressed the vehicle design requirements necessary to demonstrate the FTR concept throughout the hover/transition high-speed envelope.
Abstract: This study considers the modification of existing aircraft to the folding tilt rotor (FTR) design configuration, and then addresses the vehicle design requirements necessary to demonstrate the FTR concept throughout the hover/transition high-speed envelope Three potential candidates are considered: (1) the Bell/Boeing V-22 Osprey combined with either the existing TF-34 convertible engine or a conceptual convertible engine utilizing the torque-converter-coupled fan configuration; (2) a combination of the same powerplants with a modified Lockheed S-3A Viking; and (3) the NASA/Army/BELL XV-15 airframe mated with a conceptual generic turbofan engine with a fixed-pitch fan coupled to the engine by means of a torque converter Required aircraft modifications are identified and recommended R&D efforts for engine/rotor/airframe integration are presented

Proceedings ArticleDOI
01 Jun 1986
TL;DR: In this article, the inlet plane location, the contouring of lip and cowl, and the estimation of propeller cyclic loads due to a nonuniform flowfield were investigated.
Abstract: Advanced highly-loaded propellers are proposed to power transport aircraft that cruise at high subsonic speeds giving significant fuel savings over the equivalent turbofan engine. In order to realize these savings, the propeller must be installed so that the aerodynamics of the propeller/nacelle combination do not lead to excessive cyclic blade stresses or installation losses. The on-going, NASA sponsored, Propfan Test Assessment Program (PTA) has provided the first high-speed wind-tunnel data on an installed propfan complete with an inlet. This paper presents computational techniques that allow: (1) optimization of inlet plane location, (2) contouring of lip and cowl, and (3) estimation of propeller cyclic loads due to a nonuniform flowfield. These computational methods, in spite of the complexity of the configuration and the slipstream effects, provide predictions of aerodynamic performance which are in excellent agreement with wind-tunnel data.

Patent
09 Jul 1986
TL;DR: The turbofan engine is located at the rear part of the land or sea vehicle and has an air intake at the front which is ducted under the passengers cabin back to the engine as discussed by the authors.
Abstract: The turbofan engine is located at the rear part of the land or sea vehicle. It has an air intake at the front which is ducted under the passengers cabin back to the engine. The engine has two convergent propelling nozzles each incorporating a thrust reverser and noise suppressor. Locating these nozzles at the rear corners of the vehicle improves its steerability at curves. This design will enable the vehicle to climb uphill grades with full power and speed and descend downhills with full control. The independence on adhesion force will enable it to run without slipping on snowy roads or digging in sandy areas. The latter advantage is at premium in military tanks.

26 Jun 1986
TL;DR: A comprehensive, in-depth review of the serious efforts made in the development of VTOL and V/STOL concepts and aircraft other than the helicopter is presented in this article.
Abstract: : The purpose of this document is to present a comprehensive, in-depth review of the serious efforts made in the development of VTOL and V/STOL concepts and aircraft other than the helicopter. The time period covered is from the beginning of organized government-sponsored activity in the late 1940's through the present, during which a very large study and development activity has taken place. Conventional helicopters are not included because their development history is a sizeable subject in itself and one which is already well-documented. Included are V/STOL aircraft which do use rotors but are aimed at providing cruise speeds and aerodynamic efficiencies similar to those of conventional airplanes. Although not aircraft in the conventional sense, wingless VTOL vehicles which use direct thrust (rocket or turbojet/turbofan) for lift in all flight modes also are included since such machines do have a close relationship to some of the more commonly accepted forms of VTOL aircraft. This volume contains an introductory review of V/STOL aircraft concepts and the rationale behind them. The concepts are categorized by propulsion system. This volume contains definitive information and technical reviews of the rocket belt, turbojet/turbofan platform type (wingless) vehicles, and turbojet/turbofan vertical attitude takeoff and landing aircraft.

01 Jun 1986
TL;DR: A hypothetical turbofan engine simplified simulation with a multivariable control and sensor failure detection, isolation, and accommodation logic (HYTESS II) is presented and the digital program is self-contained, efficient, realistic and easily used.
Abstract: 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.

Journal ArticleDOI
TL;DR: In this paper, a theoretical model of the acoustic pressure generated in the combustor due to the turbulence/flame front interaction did not account for acoustic waves reflected from the turbine, and it was concluded that the simplified combustion noise theory, when modified by a simple turbine reflecting plane, adequately accounts for the changes in measured combustor pressure spectra.
Abstract: Pressure fluctuations measured in turbine engine combustors at low engine speed show good agreement with theory. Above idle speed, the turbine chokes and a significant change in the shape of the measured combustor pressure spectrum is observed. A theoretical model of the acoustic pressure generated in the combustor due to the turbulence/flame front interaction did not account for acoustic waves reflected from the turbine. By retaining this combustion noise source model and adding a reflecting plane at the turbine and combustor inlet, a theoretical model has been developed that reproduces the undulations in the combustor fluctuating pressure spectra. Plots of the theoretical combustor fluctuating pressure spectra are compared to the measured pressure spectra obtained from the CF6-50 turbofan engine over a range of engine operating speeds. Reasonable agreement exists. It is thus concluded that the simplified combustion noise theory, when modified by a simple turbine reflecting plane, adequately accounts for the changes in measured combustor pressure spectra. The shape of the pressure spectra downstream of the turbine, neglecting noise generated by the turbine itself, will be the combustion noise spectra essentially unchanged, except for the level reduction due to the energy blocked by the turbine.

Patent
08 Oct 1986

ReportDOI
01 Aug 1986
TL;DR: In this paper, an experimental and analytical program was conducted to determine the nature of the flow field around a subscale model of a high bypass turbofan engine installed in a representatively scaled altitude test cell.
Abstract: : An experimental and analytical program was conducted to determine the nature of the flow field around a subscale model of a high bypass turbofan engine installed in a representatively scaled altitude test cell The engine model employed variable geometry and flow conditions in order to determine their effects on test cell recirculating flows, which can affect engine performance during altitude testing Flow field data were obtained from both two axis laser Doppler velocimeters, as well as from pressure and temperature instrumentation installed on the model and test cell Review of full and 1/10 scale test data and the results of the subscale tests indicate that test cell recirculation effects are a function of cell geometry Measurement of test cell effects is dependent on a baseline test configuration, such as an outdoor test, where the effects are not present

Proceedings ArticleDOI
01 Feb 1986
TL;DR: A full-scale tilt-nacelle V/STOL aircraft model was tested in hover at the National Full Scale Aerodynamics Complex (NFAC), NASA Ames Research Center as discussed by the authors.
Abstract: A full-scale, tilt-nacelle V/STOL aircraft model was tested in hover at the National Full Scale Aerodynamics Complex (NFAC), NASA Ames Research Center The model was powered by two TF-34 turbofan engines It was tested at several ground heights and control deflections Test technique and test setup were documented Limited results show that: (1) a small change in control power with ground height was measured, and control power was found to be good over + or - 20 deg of horizontal vane deflection; (2) integrated fuselage undersurface pressures, when compared with the total model loads and measured thrust, defined the effect of the fountain and its related flow field on model forces and moments; and (3) there was no indication of hot gas ingestion during simulated takeoff in calm winds from wheels on deck ground height