Showing papers on "Turbofan published in 2002"

Vertical takeoff and landing aircraft

Abstract: A vertical takeoff and landing (VTOL) aircraft is superior in maneuverability, safety, and mobility. The aircraft has turbofan engines with separate core engines having fan engines used commonly for cruising and lifting up. The thrust from the fan engines can be directed to all directions by supporting the fan engines of the turbofan engines with separate core engines with biaxial support so that the fan engines are rotatable in the direction of pitching and rolling. The fan engines are mounted on both sides of each of front and rear sings. With this construction, the VTOL aircraft can cruise and hover by tilting the fan engines about the two axes while using the fan engines commonly for cruising and hovering.

Aerodynamic Performance of Scale-Model Turbofan Outlet Guide Vanes Designed for Low Noise

Abstract: The design of effective new technologies to reduce aircraft propulsion noise is dependent on an understanding of the noise sources and noise generation mechanisms in the modern turbofan engine. In order to more fully understand the physics of noise in a turbofan engine, a comprehensive aeroacoustic wind tunnel test programs was conducted called the 'Source Diagnostic Test.' The text was cooperative effort between NASA and General Electric Aircraft Engines, as part of the NASA Advanced Subsonic Technology Noise Reduction Program. A 1/5-scale model simulator representing the bypass stage of a current technology high bypass ratio turbofan engine was used in the test. The test article consisted of the bypass fan and outlet guide vanes in a flight-type nacelle. The fan used was a medium pressure ratio design with 22 individual, wide chord blades. Three outlet guide vane design configurations were investigated, representing a 54-vane radial Baseline configuration, a 26-vane radial, wide chord Low Count configuration and a 26-vane, wide chord Low Noise configuration with 30 deg of aft sweep. The test was conducted in the NASA Glenn Research Center 9 by 15-Foot Low Speed Wind Tunnel at velocities simulating the takeoff and approach phases of the aircraft flight envelope. The Source Diagnostic Test had several acoustic and aerodynamic technical objectives: (1) establish the performance of a scale model fan selected to represent the current technology turbofan product; (2) assess the performance of the fan stage with each of the three distinct outlet guide vane designs; (3) determine the effect of the outlet guide vane configuration on the fan baseline performance; and (4) conduct detailed flowfield diagnostic surveys, both acoustic and aerodynamic, to characterize and understand the noise generation mechanisms in a turbofan engine. This paper addresses the fan and stage aerodynamic performance results from the Source Diagnostic Test.

Gas Turbine Engine and Sensor Fault Diagnosis Using Optimization Techniques

Abstract: A diagnostic system is described for performance analysis of gas turbine engine components and sensors. The system estimates the performance parameters expressing the fault condition of the engine components in the presence of measurement noise and biases. The measurement uncertainty is supposed to affect even the parameters setting the operating condition of the engine. Estimation is performed through bptimization of an objective function by means of an ad hoc genetic algorithm. The genetic algorithm uses an accurate nonlinear steady-state performance model of the engine. The only statistical assumption required by the technique concerns the measurement noise and the maximum allowed number of faulty sensors and engine components, which is enclosed as a constraint. The technique has been thoroughly tested with the model of a low bypass ratio turbofan, and the results show the high level of accuracy achieved.

Combined cycle pulse detonation turbine engine

Abstract: A turbofan engine includes a pulse detonation system to create a temperature rise and a pressure rise within the engine to generate thrust from the engine. The system includes a pulse detonation augmentor including a shock tube sub-system. The shock tube sub-system includes a plurality of shock tubes which mix air and fuel introduced to the pulse detonation augmentor and detonate the mixture. The detonation creates hot combustion gases which are directed from the engine to produce thrust for the engine. Alternatively, the system includes a pulse detonation augmentation system that replaces a core engine of a turbo-fan engine.

Military Jet Engine Acquisition: Technology Basics and Cost-Estimating Methodology

Abstract: : Good cost estimates contribute significantly to an effective acquisition policy. RAND has a long history of producing cost-estimating methodologies for military jet engines. Two of RAND's more recent studies of turbine engine costs are Nelson (1977) and Birkler, Garfinkle, and Marks (1982). This report updates those earlier studies by incorporating cost and technical data on recent engine development and production efforts. We analyzed this information and produced a set of parametric relationships to estimate turbofan engine development costs, development schedules, and unit production costs. In this analysis, we have extended and improved upon earlier RAND analyses in two key ways: The previous RAND studies grouped turbojet and turbofan engines into the same population. To provide a more homogeneous population, we focused exclusively on parametric relationships for turbofan engines in this study (because pure turbo-jet engines are largely no longer used in modern aircraft). In the previous studies, it was often not clear how the data from a particular engine family was treated. In our analysis, we treat each model (or "dash number") as a separate observation. We explicitly consider how derivative engines relate to first-of-a-kind engines.

Turbofan Performance Deterioration Tracking Using Nonlinear Models and Optimization Techniques

Abstract: A method of identifying the gradual deterioration in the components of jet engines is presented. It is based on the use of an engine model which has the capability to adapt component condition parameters, so that measured quantities are matched. The main feature of the method is that it gives the possibility to identify performance deviations in a number of parameters larger than the number of measured quantities. This is achieved by optimizing a cost function which incorporates not only measurement matching terms but also terms expressing various constraints resulting from the physical knowledge of the deterioration process. Time series of data representing deterioration scenarios are used to demonstrate the method’s capabilities. The test case considered is a twin spool partially mixed turbofan, representative of present day large civil aero engines. Implementation aspects, related to both the measurement set and the identification algorithms are discussed. An interpretation of the output of the method in function of different parameters entering the diagnostic problem is presented.Copyright © 2002 by ASME

Turbofan engine internal anti-ice device

Abstract: A system and method are provided for preventing the formation of ice on or removing ice from an internal surface of a turbofan engine. A splitter region, associated with a booster compressor of the turbofan engine, is identified. The splitter region has surfaces internal to the turbofan engine subject to inlet icing conditions. A resin is molded along a leading edge of the splitter region, and electric coils are installed within the resin to prevent ice build-up on the splitter region or to remove ice from the splitter region during icing conditions.

Novel Approach for Reducing Rotor Tip-Clearance-Induced Noise in Turbofan Engines

Abstract: Rotor tip-clearance induced noise, in the form of both rotor self-noise and rotor-stator interaction noise, constitutes an important component of total fan noise. Innovative yet cost-effective techniques to suppress rotor-generated noise are, therefore, of foremost importance for improving the noise signature of turbofan engines. To that end, the feasibility of a passive porous treatment strategy to modify positively the tip-clearance flowfield is addressed. Accurate viscous flow calculations of the baseline and the treated rotor flowfields are studied. Detailed comparison between the computed baseline solution and experimental measurements shows excellent agreement. Tip-vortex structure, trajectory, strength, and other relevant aerodynamic quantities are extracted from the computed database. Extensive comparison between the untreated and treated tip-clearance flowfields is performed. The effectiveness of the porous treatment for altering the rotor-tip vortex flowfield, in general, and reducing the intensity of the tip vortex, in particular, is demonstrated. In addition, the simulated flowfield for the treated tip clearly shows that substantial reduction in the intensity of both the shear layer rollup and boundary-layer separation on the wall is achieved.

Engine System Performance of Pulse Detonation Concepts Using the NPSS Program

Abstract: The Numerical Propulsion Systems S imulation (NPSS) tool has been used to analyze several Pulse Detonation Engine (PDE) concepts that have been of interest lately The PDE cycle approximates a constant volume combustion process which results in both a temperature and pressure rise across t he device In this study, the PDE was modeled using standard shock tube relationships and flow into and out of the device was assumed to be steady state The capabilities of NPSS in modeling this concept will be discussed An analysis was completed comp aring a PDE to a conventional ramjet For the purposes of the study, the PDE was modeled as a ramjet with a detonation chamber instead of the conventional combustor (basic PDE) Comparisons were made on thrust, specific fuel consumption (SFC), and engine pressure ratio over a range of peak temperatures The unsteady flow characteristic of the PDE has the potential to degrade inlet and nozzle performance relative to steady flow A short parametric study was completed to gauge the overall performance impa ct of changes to inlet and nozzle performance The incorporation of a detonation tube into the core of a high bypass turbofan engine (~100,000 lb thrust class) was also investigated Thrust and SFC comparisons are made along with comments on changes req uired to the system in order to incorporate such a device into a high bypass turbofan engine Finally, a brief discussion is included on the usefulness of this level of analysis of PDE concepts Areas of concern will be noted with possible workarounds id entified NPSS Analysis Tool

High bypass multi-fan engine

Abstract: A turbofan jet engine having a housing and an engine core disposed in the housing. The engine core includes at least a compressor, turbine, and a drive shaft. The drive shaft defines a drive shaft axis. A plurality of fans are disposed in the housing and each is rotatable about a separate fan axis. Each of the fan axes are axially offset from the drive shaft axis. The turbofan jet engine further includes a drive system operably interconnecting the engine core and fans so as to rotatably drive the fans and selectively disengage select fans from the engine core.

Fan Noise Source Diagnostic Test - Rotor Alone Aerodynamic Performance Results

Abstract: The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.

Measurements of Turbulent Flow Field in Separate Flow Nozzles with Enhanced Mixing Devices - Test Report

Abstract: As part of the Advanced Subsonic Technology Program, a series of experiments was conducted at NASA Glenn Research Center on the effect of mixing enhancement devices on the aeroacoustic performance of separate flow nozzles. Initial acoustic evaluations of the devices showed that they reduced jet noise significantly, while creating very little thrust loss. The explanation for the improvement required that turbulence measurements, namely single point mean and RMS statistics and two-point spatial correlations, be made to determine the change in the turbulence caused by the mixing enhancement devices that lead to the noise reduction. These measurements were made in the summer of 2000 in a test program called Separate Nozzle Flow Test 2000 (SFNT2K) supported by the Aeropropulsion Research Program at NASA Glenn Research Center. Given the hot high-speed flows representative of a contemporary bypass ratio 5 turbofan engine, unsteady flow field measurements required the use of an optical measurement method. To achieve the spatial correlations, the Particle Image Velocimetry technique was employed, acquiring high-density velocity maps of the flows from which the required statistics could be derived. This was the first successful use of this technique for such flows, and shows the utility of this technique for future experimental programs. The extensive statistics obtained were likewise unique and give great insight into the turbulence which produces noise and how the turbulence can be modified to reduce jet noise.

Ultra Efficient Engine Technology Systems Integration and Environmental Assessment

Abstract: This study documents the design and analysis of four types of advanced technology commercial transport airplane configurations (small, medium large and very large) with an assumed technology readiness date of 2010. These airplane configurations were used as a platform to evaluate the design concept and installed performance of advanced technology engines being developed under the NASA Ultra Efficient Engine Technology (UEET) program. Upon installation of the UEET engines onto the UEET advanced technology airframes, the small and medium airplanes both achieved an additional 16% increase in fuel efficiency when using GE advanced turbofan engines. The large airplane achieved an 18% increase in fuel efficiency when using the P&W geared fan engine. The very large airplane (i.e. BWB), also using P&W geared fan engines, only achieved an additional 16% that was attributed to a non-optimized airplane/engine combination.

Duct Mode Measurements on the TFE731-60 Full Scale Engine

Abstract: A continuously rotating rake with radial microphones was developed to measure the inlet and exhaust duct modes on a TFE731-60 turbofan engine. This was the first time the rotating rake technology was used on a production engine. The modal signature for the first three fan harmonics was obtained in the inlet and exhaust. Rotor-stator and rotor-strut interaction modes were measured. Total harmonic power was calculated over a range of fan speeds. Above sonic tip speed, the rotor locked mode was not strong enough to be identified, but the “buzz-saw” noise at fan sub-harmonics was identified. Introduction The Advanced Subsonic Technology (AST) program sponsored the Engine Validation of Noise Reduction Concepts (EVNRC). A full-scale turbofan engine, the TFE731-60 was used as a test bed for part of this program. A continuously rotating rake with radially distributed microphones was developed for use on the Honeywell TFE731-60 as an acoustic diagnostic tool. Rotating rake technology had been developed and used successfully on model scale

Combined cycle pulse detonation turbine engine operating method

Abstract: A turbofan engine includes a pulse detonation system to create a temperature rise and a pressure rise within the engine to generate thrust from the engine. The system includes a pulse detonation augmentor including a shock tube sub-system. The shock tube sub-system includes a plurality of shock tubes which mix air and fuel introduced to the pulse detonation augmentor and detonate the mixture. The detonation creates hot combustion gases which are directed from the engine to produce thrust for the engine. Alternatively, the system includes a pulse detonation augmentation system that replaces a core engine of a turbo-fan engine.

Closed-loop control of a shape memory alloy actuation system for variable area fan nozzle

Abstract: Shape Memory Alloys have been used in a wide variety of actuation applications. A bundled shape memory alloy cable actuator, capable of providing large force and displacement has been developed by United Technologies Corporation (patents pending) for actuating a Variable Area fan Nozzle (VAN). The ability to control fan nozzle exit area is an enabling technology for the next generation turbofan engines. Performance benefits for VAN engines are estimated to be up to 9% in Thrust Specific Fuel Consumption (TSFC) compared to traditional fixed geometry designs. The advantage of SMA actuated VAN design is light weight and low complexity compared to conventionally actuated designs. To achieve the maximum efficiency from a VAN engine, the nozzle exit area has to be continuously varied for a certain period of time during climb, since the optimum nozzle exit area is a function of several flight variables (flight Mach number, altitude etc). Hence, the actuator had to be controlled to provide the time varying desired nozzle area. A new control algorithm was developed for this purpose, which produced the desired flap area by metering the resistive heating of the SMA actuator. Since no active cooling was used, reducing overshoot was a significant challenge of the controller. A full scale, 2 flap model of the VAN system was built, which was capable of simulating a 20% nozzle area variation, and tested under full scale aerodynamic load in NASA Langley Jet Exit Test facility. The controller met all the requirements of the actuation system and was able to drive the flap position to the desired position with less than 2% overshoot in step input tests. The controller is based on a adaptive algorithm formulation with logical switches that reduces its overshoot error. Although the effectiveness of the controller was demonstrated in full scale model tests, no theoretical results as to its stability and robustness has been derived. Stability of the controller will have to be investigated for the next stage of technology readiness.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Analytical Modeling of Herschel-Quincke Concept Applied to Inlet Turbofan Engines

Abstract: This report summarizes the key results obtained by the Vibration and Acoustics Laboratories at Virginia Tech over the period from January 1999 to December 2000 on the project 'Investigation of an Adaptive Herschel-Quincke Tube Concept for the Reduction of Tonal and Broadband Noise from Turbofan Engines', funded by NASA Langley Research Center. The Herschel-Quincke (HQ) tube concept is a developing technique the consists of circumferential arrays of tubes around the duct. The analytical model is developed to provide prediction and design guidelines for application of the HQ concept to turbofan engine inlets. An infinite duct model is developed and used to provide insight into attenuation mechanisms and design strategies. Based on this early model, the NASA-developed TBIEM3D code is modified for the HQ system. This model allows for investigation of the HQ system combined with a passive liner.

Fan for a turbofan gas turbine engine

Abstract: A fan (22) for a turbofan gas turbine engine (10) comprises a fan rotor (24) carrying a first set of circumferentially spaced radially extending fan blades (28) and a second set of circumferentially spaced radially extending fan blades (30). The second set of fan blades (30) is arranged downstream of the first set of fan blades (28). The hub to tip ratio (R1/R2) of the first set of fan blades (28) is substantially the same as the hub to tip ratio (R3/R4) of the second set of fan blades (30) and the radius (R2) of the radially outer ends of the first set of fan blades (28) is less than the radius (R4) of the radially outer ends of the second set of fan blades (30). This increases the flow area of the fan (22) by about 7% compared to a conventional fan of the same radius and thus increases the mass flow by about 7% and/or increases the pressure ratio.

Evaluation of an Aircraft Concept With Over-Wing, Hydrogen-Fueled Engines for Reduced Noise and Emissions

Abstract: This report describes the analytical modeling and evaluation of an unconventional commercial transport aircraft concept designed to address aircraft noise and emission issues. A strut-braced wing configuration with overwing, ultra-high bypass ratio, hydrogen fueled turbofan engines is considered. Estimated noise and emission characteristics are compared to a conventional configuration designed for the same mission and significant benefits are identified. The design challenges and technology issues which would have to be addressed to make the concept a viable alternative to current aircraft designs are discussed. This concept is one of the "Quiet Green Transport" aircraft concepts studied as part of NASA's Revolutionary Aerospace Systems Concepts (RASC) Program. The RASC Program seeks to develop revolutionary concepts that address strategic objectives of the NASA Enterprises, such as reducing aircraft noise and emissions, and to identify enabling advanced technology requirements for the concepts.

AIAA-2002-0374 Aerodynamic Performance of Scale-Model Turbofan Outlet Guide Vanes Designed for Low Noise

Abstract: The design of effective new technologies to reduce aircraft propulsion noise is dependent on an understanding of the noise sources and noise generation mechanisms in the modern turbofan engine. In order to more fully understand the physics of noise in a turbofan engine, a comprehensive aeroacoustic wind tunnel test program was conducted called the “Source Diagnostic Test.” The test was cooperative effort between NASA and General Electric Aircraft Engines, as part of the NASA Advanced Subsonic Technology Noise Reduction Program. A 1/5-scale model simulator representing the bypass stage of a current technology high bypass ratio turbofan engine was used in the test. The test article consisted of the bypass fan and outlet guide vanes in a flight-type nacelle. The fan used was a medium pressure ratio design with 22 individual, wide chord blades. Three outlet guide vane design configurations were investigated, representing a 54-vane radial Baseline configuration, a 26-vane radial, wide chord Low Count configuration and a 26-vane, wide chord Low Noise configuration with 30° of aft sweep. The test was conducted in the NASA Glenn Research Center 9- by 15-Foot Low Speed Wind Tunnel at velocities simulating the takeoff and approach phases of the aircraft flight envelope. The Source Diagnostic Test had several acoustic and aerodynamic technical objectives: first, establish the performance of a scale model fan selected to represent the current technology turbofan product; second, assess the performance of the fan stage with each of the three distinct outlet guide vane designs; third, determine the effect of the outlet guide vane configuration on the fan baseline performance; and finally, conduct detailed flowfield diagnostic surveys, both acoustic and aerodynamic, to characterize and

Some Unconventional Aero Gas Turbines Using Hydrogen Fuel

Abstract: The use of hydrogen as an aviation fuel can be beneficial for the reduction of CO2 emissions, if renewable energy sources are used for hydrogen production. Pure hydrogen fuel produces no CO2 in flight. NOx emissions can be significantly lower for hydrogen fuelled combustors than for current kerosene fuelled combustors. Other advantages derive from the high energy content, which reduces the necessary fuel mass, and from the availability of a valuable heat sink, useful to improve cycle performance. The present paper (based on the EU Cryoplane Project) focuses on the use of hydrogen in aero gas turbine engines. It studies the differences in performance produced by of its cryogenic properties in unconventional cycles. Three novel concepts are applied to a turbofan aero engine; for each cycle the improvement in performance at take-off and cruise is presented. An estimation of the weight and size of the engine is then made.Copyright © 2002 by ASME

Optimum Mixing of Core and Bypass Streams in High-Bypass Civil Turbofan

Abstract: In a mixed-stream turbofan, except for fan pressure ratio, the mission matched optimum selection of other basic cycle variables like bypass ratio, overall pressure ratio, throttle ratio, and turbine entry temperature depends upon engine-airframe interactions over the prescribed mission and the available technology level. The fan pressure ratio is decided by the mixing conditions that are internal to the engine. This paper, by utilizing a multidisciplinary cycle optimization software, performs a number of numerical experiments to determine a criteria for mixing of bypass and core streams, which results in an optimum fan pressure ratio. The use of optimum fan pressure ratio will aid the other basic cycle parameters in enhancing performance gains caused by mixing, thereby improving the engine-airframe-mission compatibility. The penalty ofnon- or suboptimal mixing, and savings in mission fuel consumption for a mixed-stream turbofan with respect to a separate exhaust turbofan, both at optimum fan pressure ratio are also quantified.

Overview of High-Fidelity Modeling Activities in the Numerical Propulsion System Simulations (NPSS) Project

Abstract: A high-fidelity simulation of a commercial turbofan engine has been created as part of the Numerical Propulsion System Simulation Project. The high-fidelity computer simulation utilizes computer models that were developed at NASA Glenn Research Center in cooperation with turbofan engine manufacturers. The average-passage (APNASA) Navier-Stokes based viscous flow computer code is used to simulate the 3D flow in the compressors and turbines of the advanced commercial turbofan engine. The 3D National Combustion Code (NCC) is used to simulate the flow and chemistry in the advanced aircraft combustor. The APNASA turbomachinery code and the NCC combustor code exchange boundary conditions at the interface planes at the combustor inlet and exit. This computer simulation technique can evaluate engine performance at steady operating conditions. The 3D flow models provide detailed knowledge of the airflow within the fan and compressor, the high and low pressure turbines, and the flow and chemistry within the combustor. The models simulate the performance of the engine at operating conditions that include sea level takeoff and the altitude cruise condition.

Multivariant set point using N1 and N2 for engine control

Abstract: A turbofan engine throttle control system (10) and method for eliminating dead bands in the throttle control by decreasing and increasing the fuel flow to the engine during transition from the scheduled core speed to scheduled fan speed of the engine to effect a smooth and continuous transition from the core speed to the fan speed and vice-versa. A signal is generated to open and close a valve system to augment and decrease the fuel flow in response to sensing different throttle lever (22) angles.

Experimental Investigation of the Herschel-Quincke Tube Concept on the Honeywell TFE731-60

Abstract: This report summarizes the key results obtained by the Vibration and Acoustics Laboratories at Virginia Tech over the period from January 1999 to December 2000 on the project 'Investigation of an Adaptive Herschel-Quincke Tube Concept for the Reduction of Tonal and Broadband Noise from Turbofan Engines', funded by NASA Langley Research Center. The Herschel-Quincke (HQ) tube concept is a developing technique that consists of circumferential arrays of tubes around the duct. A fixed array of tubes is installed on the inlet duct of the Honeywell TFE731-60 engine. Two array designs are incorporated into the inlet treatment, each designed for a different circumferential mode order which is expected to be cut on in the duct. Far field and in-duct noise measurement data are presented which demonstrate the effectiveness of the HQ concept for array 1, array 2, and both operating simultaneously.