Showing papers on "Turbofan published in 2005"

More electric aircraft starter-generator multi-speed transmission system

Abstract: A turbofan gas turbine propulsion engine includes a multi-speed transmission between the high pressure and low pressure turbines and associated high pressure and low pressure starter-generators. The multi-speed transmission reduces the operating speed range from the low pressure turbine to its associated starter-generator, and is configurable to allow the starter-generator associated with the low pressure turbine to supply starting torque to the engine.

Intercooled Recuperated Gas Turbine Engine Concept

Abstract: *Economical and environmental concerns have world-wide initiated research programs towards a “cleaner engine”, with the objective of a substantial reduction in polluting emissions and fuel consumption. In the context of different programs and international collaborations, MTU has conducted studies to integrate heat exchangers into a novel concept aero engine cycle, a technological innovation that can be extremely beneficial in terms of fuel consumption. NOx emissions and noise levels can also be reduced, thanks to different combustion chamber conditions and to a high bypass ratio configuration. The paper focuses on the thermodynamic cycle and on the necessary technological innovations. An intercooler and a MTU-designed exhaust gas recuperator are applied to a 3-shaft, geared turbofan configuration. The engine is optimized for long range applications, with regard to fuel consumption. Status results for the chosen configurations are presented, together with parametric and optimization studies. Estimations of heat exchanger weight and of engine emissions are finally made.

More electric aircraft power transfer systems and methods

Abstract: A turbofan gas turbine propulsion engine includes a system to transfer power from the low pressure turbine to the high pressure turbine and/or extract additional load from the low pressure turbine during certain turbofan engine operational conditions. The systems include a hydrostatic power transfer system that includes a hydraulic pump and a hydraulic motor coupled to the low pressure and high pressure turbine, respectively. The systems additionally include a mechanical and electrical load shifting/loading sharing systems that use clutches and gear assemblies to share and/or shift load between the turbines.

Systems and methods for starting aircraft engines

Abstract: Methods and systems for starting aircraft turbofan engines are disclosed. A system in accordance with one embodiment includes an electrically-powered starter motor coupled to a turbofan engine to provide power to the turbofan engine during an engine start procedure. The system can further include an on-board, deployable, ram air driven turbine coupled to an electrical generator, which is in turn coupled to the starter motor to provide electrical power to the starter motor. In other embodiments, the ram air driven turbine can be replaced with a fuel cell or a battery. In still further embodiments, a single controller can control operation of both the engine starter and other motors of the aircraft.

Engine And Installation Configurations For A Silent Aircraft

Abstract: The Silent Aircraft Initiative is a research projec t funded by the Cambridge-MIT Institute aimed at reducing aircraft noise to the point where it is imperceptible in the urban environments around airp orts. The aircraft that fulfils this objective must also be economically competitive with conventional aircraft of the future and therefore fuel consumption is a key consideration for the design. This paper identifies some key features of a propulsion system that can achiev e the Silent Aircraft noise target and explores the relat ionships between the factors that affect fuel consumption. I t also considers the different demands made of an engine a t different operating conditions in the flight envelo pe. These studies are used to propose viable engine and installation configurations that could meet the Sil ent Aircraft noise requirements. The findings point tow ards a multiple turbofan system with a variable geometry exhaust and a novel, embedded installation.

Compact booster bleed turbofan

Abstract: A turbofan engine (10) includes a fan (14) mounted to a fan frame (32) inside a fan nacelle (30). A booster compressor (16) is joined to the fan (14) inboard a flow splitter (34). A booster bleed system (54) is disposed inside the splitter (34), and includes an inlet (58) at the compressor outlet (52), and an outlet (60) joined to the bypass duct (36) following the fan (14).

Parametric Cycle Analysis of a Turbofan Engine with an Interstage Turbine Burner

Abstract: This study focuses on the parametric cycle analysis of a dual-spool, separate-flow turbofan engine with an interstage turbine burner (ITB). The ITB considered in this paper is a relatively new concept in modern jet engine propulsion. It serves as a secondary combustor and is located between the high-pressure and the low-pressure turbines, that is, the transition duct. The objective of this study is to use engine design parameters, such as highpressure and low-pressure turbine inlet temperatures to obtain engine performance parameters, for example, specific thrust and thrust specific fuel consumption. A turbine cooling model is also included. Results confirm the advantages of ITB, that is, higher specific thrust, less cooling air, and possibly less NOx production, provided that the main-burner exit temperature and ITB exit temperature are properly specified.

Design and Control of a Morphing Chevron for Takeoff and Cruise Noise Reduction

Abstract: ‡Commercial high-bypass ratio turbofan engines generate high levels of noise as the jet exhaust mixes with the ambient air. Serrated aerodynamic devices, known as chevrons, positioned along the trailing edges of a jet engine’s primary and secondary exhaust nozzle have been shown to reduce jet noise at take off as well as shock-cell noise at cruise. Their optimum shape is a finely tuned compromise between noise-benefit and thrust-loss. We report here the development of a powered variable geometry chevron (PVGC) capable of transitioning between take off and cruise shapes. Actuators composed of thermally active nickel-titanium (NiTinol) shape memory alloy drive the shape change. A full scale PVGC was tested under representative flow conditions in Boeing’s Nozzle Test Facility (NTF). In this test a simple proportional-integral control system provided continuous control of the VGC tip immersion between take off and cruise conditions. The collected data supports the aerodynamic, thermal, and mechanical design of the PVGC as well as the control system approach.

Nonlinearly stacked low noise turbofan stator

Abstract: The present invention provides a nonlinearly stacked low noise turbofan stator vane (11). The stator is in an axial fan or compressor turbomachinery stage that is comprised of a collection of vanes whose highly three-dimensional shape is selected to reduce rotor-stator and rotor­strut interaction noise while maintaining the aerodynamic and mechanical performance of the vane. The nonlinearly stacked low noise turbofan stator vane reduces noise associated with the fan stage of turbomachinery to improve environmental compatibility. The stator vane (11) has a characteristic curve that is characterized by a nonlinear sweep and a nonlinear lean.

Fixed nozzle thrust augmentation system

Abstract: A thrust augmentation system for a mixed exhaust turbofan engine comprises an augmentation duct, a combustion system and a fixed area exhaust nozzle. The augmentation duct receives primary and secondary air of the turbofan engine and is positioned co-axially with an exhaust case of the turbofan engine. The combustion system increases the thrust produced by the mixed exhaust of the turbofan. The fixed area exhaust nozzle has a throat area larger than that which would maximize the non-augmented thrust.

High by-pass ratio turbofan

Abstract: The turbofan has a fan mounted on upstream of a compressor and driven in rotation by a turbine A rigid cylindrical envelop (10) has upstream and downstream ends (19, 26) fixed on intermediate and exhaust cases, respectively. The envelope assures transmission of force between the intermediate and exhaust cases. The end (26) has foil flaps (27) which hinder air flow towards the downstream and break the thrust provided by the fan.

Chevron-type primary exhaust nozzle for aircraft turbofan engine, and aircraft comprising such a nozzle

Abstract: A primary exhaust nozzle for a turbofan engine of the double, separated air-flow type for aircraft comprises: an inner coat, within which there circulates a primary air flow (FP), comprising chevrons at an external end and an outer coat at least partially surrounding the inner coat and along which there flows a secondary air flow (FS), the outer coat being mobile along the inner coat Also disclosed is an aircraft comprising such an exhaust nozzle

Air dryer system and method employing a jet engine

Abstract: An air dryer and process employs a jet engine for producing high quality dried products. A turbofan jet engine in an air-drying system uses both thermal and non-thermal air-drying. The turbofan jet engine is housed within an air distribution chamber for directing exhaust air and bypass air from the jet engine into a product drying tube, where it is dried through a combination of thermal drying from heat content in an engine exhaust, and by the kinetic energy of air flowing past the product traveling through the drying tube, that may include a physical impediment for retarding retard the speed of the product solids flowing in the air stream through the tube.

Fan rotor design for coincidence avoidance

Abstract: A fan rotor capable of avoiding coincidence will include a fan hub comprising one or more slots each designed to receive a fan blade; and one or more fan blades disposed within the slots. One or more slots will comprise an Rz′ baseline and have one or more second fan blades disposed therein while another set of slots will have an Rz baseline having one or more first fan blades disposed therein. The tips of the second fan blades will be positioned at a distance farther from the fan hub than the tips of the first fan blades disposed, which when implemented in a turbofan engine will avoid coincidence occurrences.

Universal carnot propulsion systems for turbo rocketry

Abstract: Turbofan jet engines utilizing the Carnot cycle for improved performance with isothermal compression of combustion air and, in part, isothermal expansion of thermally heated air, the engines having a turbofan compressor rotor with hollow fan blades in a core bypass passage through the engine and an annular, peripheral thermal chamber with staged turbine blades in an expansion chamber where heated gases are supplied to multiple stages to maintain peak temperatures.

Distributed propulsion and turbofan scale effects

Abstract: A coupled aircraft and engine model is used to evaluate the fuel consumption and mission weight of distributed propulsion aircraft. The engine cycle is optimized for the installation to show the ultimate performance of each propulsion alternative. The effect of higher specific fuel consumption for smaller engines is weighed against the potentially lower installation weight and higher integration efficiency of distributed propulsion.

Fan Flow Control for Noise Reduction Part 1: Advanced Trailing Edge Blowing Concepts

Abstract: *† ‡ § This paper documents trailing edge blowing research performed to reduce rotor / stator interaction noise in turbofan engines, under the Ultra-Efficient Engine Technology and Quiet Aircraft Technology programs at the NASA Glenn research center. Velocity deficits are introduced into an engine's working fluid by viscous losses on fan blade surfaces. These propagate downstream where they are cut by stator vanes and produce interaction noise. The unsteady surface pressure on the vanes is coupled to acoustic duct modes that are excited to produce tonal noise at the blade passing frequency and its harmonics. The wake deficits responsible for the noise can be reduced by injecting air into the working fluid via internal passageways in the fan blades. The current technique requires an excessive amount of air to be drawn from the engine compressor for use in reducing wake deficits, resulting in a large loss of performance. The purpose of this research is to investigate new blowing configurations in order to achieve noise reduction with lesser amounts of air. Using the new configurations, air is not injected into every fan blade. Instead the application of injected air is varied circumferentially. For example, blowing air may be applied to alternating fan blades. This type of blowing configuration both reduces the amount of air used and changes the spectral shape of the tonal interaction noise. The original tones at the blade passing frequency and its harmonics are reduced and new tones are introduced between them. This change in the tonal spectral shape increases the performance of acoustic liners used in conjunction with the trailing edge blowing approach. The total noise reduction is therefore a combination of source-level reduction from wake-filling, absorption from acoustic liners, and increased performance of the liners. This paper presents numerical predictions made to estimate the sound power reductions due to these concepts, as well as experimental results taken on the ANCF rig at NASA Glenn for validation purposes. The results show that the new concepts are successful in increasing the efficiency of trailing edge blowing.

A Fully Integrated Approach to Component Zooming Using Computational Fluid Dynamics

Abstract: This study focuses on a simulation strategy that will allow the performance characteristics of an isolated gas turbine engine component, resolved from a detailed, high-fidelity analysis, to be transferred to an engine system analysis carried out at a lower level of resolution. This work will enable component-level, complex physical processes to be captured and analyzed in the context of the whole engine performance, at an affordable computing resource and time. The technique described in this paper utilizes an object-oriented, zero-dimensional (0-D) gas turbine modeling and performance simulation system and a high-fidelity, three-dimensional (3-D) computational fluid dynamics (CFD) component model. The work investigates relative changes in the simulated engine performance after coupling the 3-D CFD component to the 0-D engine analysis system. For the purposes of this preliminary investigation, the high-fidelity component communicates with the lower fidelity cycle via an iterative, semi-manual process for the determination of the correct operating point. This technique has the potential to become fully automated, can be applied to all engine components and does not involve the generation of a component characteristic map. This paper demonstrates the potentials of the ‘fully integrated’ approach to component zooming by using a 3-D CFD intake model of a high by-pass ratio (HBR) turbofan as a case study. The CFD model is based on the geometry of the intake of the CFM56-5B2 engine. The high-fidelity model can fully define the characteristic of the intake at several operating condition and is subsequently used in the 0-D cycle analysis to provide a more accurate, physics-based estimate of intake performance (i.e. pressure recovery) and hence, engine performance, replacing the default, empirical values. A detailed comparison between the baseline engine performance (empirical pressure recovery) and the engine performance obtained after using the coupled, high-fidelity component is presented in this paper. The analysis carried out by this study, demonstrates relative changes in the simulated engine performance larger than 1%.Copyright © 2005 by ASME

A Performance Study of a Super-cruise Engine with Isothermal Combustion inside the Turbine

Abstract: Current thinking on the best propulsion system for a next-generation supersonic cruising (Mach 2 to Mach 4) aircraft is a mixed-flow turbofan engine with afterburner. This study investigates the performance increase of a turbofan engine through the use of isothermal combustion inside the high-pressure turbine (High-Pressure Turburner, HPTB) as an alternative form of thrust augmentation. A cycle analysis computer program is developed for accurate prediction of the engine performance and a supersonic transport cruising at Mach 2 at 60,000 ft is used to demonstrate the merit of using a turburner. When assuming no increase in turbine cooling flow is needed, the engine with HPTB could provide either 7.7% increase in cruise range or a 41% reduction in engine mass flow when compared to a traditional turbofan engine providing the sane thrust. If the required cooling flow in the turbine is almost doubled, the new engine with HPTB could still provide a 4.6% increase in range or 33% reduction in engine mass flow. In fact, the results also show that the degradation of engine performance because of increased cooling flow in a turburner is less than half of the degradation of engine performance because of increased cooling flow in a regular turbine. Therefore, a turbofan engine with HPTB will still easily out-perform a traditional turbofan when even more cooling than currently assumed is introduced. Closer examination of the simulation results in off-design regimes also shows that the new engine not only satisfies the thrust and efficiency requirement at the design cruise point, but also provides enough thrust and comparable or better efficiency in all other flight regimes such as transonic acceleration and take-off. Another finding is that the off-design bypass ratio of the new engine increases slower than a regular turbofan as the aircraft flies higher and faster. This behavior enables the new engine to maintain higher thrust over a larger flight envelope, crucial in developing faster air-breathing aircraft for the future. As a result, an engine with HPTB provides significant benefit both at the design point and in the off-design regimes, allowing smaller and more efficient engines for supersonic aircraft to be realized.

Turbofan or turbojet arrangement for vehicles, craft, aircraft and the like

Abstract: The present invention is turbofan or turbojet assembly for vehicles, craft, aircraft and the like. The assembly includes a plurality of gas turbines, mini-turbines, micro-turbines or nanoturbines disposed in parallel. The turbines form a gondola that is a large, single turbine.

Joint strike fighter dual-cycle propulsion system

Abstract: The Joint Strike Fighter (JSF) is a family of aircraft that will be built in conventional, naval, and short-takeoffand-vertical-landing (STOVL) variants. The key to the development of this family of aircraft is a new dual-cycle propulsion system, which is used to convert some of the jet thrust to shaft horsepower in order to power a lift fan in the STOVL variant. The theoretical basis for the dual-cycle operation of this engine will be presented. Some results of the engine test and development program conducted by Pratt and Whitney and Rolls Royce and the JSF STOVL flight-test program will also be discussed. Potential future applications of this dual-cycle propulsion concept to STOVL transport aircraft, compound rotorcraft, and for takeoff noise reduction will be described. I. Introduction T HE F-35 Joint Strike Fighter will combine the supersonic performance of the F-16C Falcon with the short-takeoff-andvertical-landing (STOVL) capabilities of the AV-8B Harrier, while providing greater range and increased survivability. There will be three variants: a conventional takeoff-and-landing variant for the U.S. Air Force, a short-takeoff-and-vertical-landing variant for the U.S. Marine Corps and United Kingdom, and a carrier-based variant for the U.S. Navy. These three variants are shown in Fig. 1. The naval variant has a somewhat larger wing, in order to reduce landing speeds for carrier operations. This also gives it somewhat greater range, both by reducing the induced drag and by providing additional volume for fuel. The STOVL variant has a shorter canopy and a slight bulge behind the cockpit. These accommodate a lift fan installed in a bay between the inlet ducts. As shown in Fig. 2, the lift fan is driven by a drive shaft extending from the front of the cruise engine. This lift fan provides 18,000 lbs of thrust, almost half of the total lift in hover. A thrust-vectoring nozzle at the rear of the aircraft deflects the core thrust of the cruise engine, which provides another 17,000 lbs of thrust. A roll control nozzle in each of the wings is fed by fan air diverted from the cruise engine. These provide approximately 2500 lbs of thrust apiece. The two main lift nozzles and the two auxiliary roll control nozzles constitute a two plus two hover lift and control system. The cruise engine is a conventional mixed-flow turbofan, providing more than 25,000 lbs of dry thrust. The lift fan is not connected to the engine during cruise. For STOVL operations, the engine operating point is changed so that its turbine section extracts additional energy from the exhaust jet and converts it to shaft horsepower. This power is delivered to the lift fan by engaging a clutch at the end of the drive shaft extending from the front of the engine. The airplane is controlled in pitch by shifting power between the lift fan and the cruise engine nozzle. The cruise engine nozzle rotates from side to side in order to control the aircraft in yaw. To control the aircraft in roll, the area of the auxiliary nozzle on one side is opened, and the nozzle on the other side is closed. The total thrust remains constant while the thrust of the nozzle pairs are varied to provide control forces.

A Correct Thrust Determination Method for Turbine Powered Simulators in Wind Tunnel Testing

Abstract: The trend to install turbofan engines (TF) with a much larger bypass ratio (BPR) than today engines on a conventional civil transport aircraft (A/C) leads to a very close coupling of the engine and the wing. Drag penalties may result which have to be determined carefully and correctly. Even though CFD is a strong analytical tool, testing of such configurations in the Wind Tunnel (WT) is indispensable. However, results obtained at transonic speeds show unexpected drag behavior in terms of the BPR and power setting. Analysis of the used Standard-Bookkeeping-Method (SBM), which is based on static TPS calibration, identifies shortcomings of the TPS-calibration procedure to be responsible for the observed WTresults. From this analysis a correction method is derived, which allows the correction of the obtained WT-results to correctly account for the effects of the interaction between jet and outer flow. The application of this method and the comparison with CFD-results underlines the necessity for correct thrust-drag-bookkeeping.

Design and Analysis of a High Stage Loading Five-Stage LP Turbine Rig Employing Improved Transition Modeling

Abstract: Modern aircraft engine designs have to realize high performance while managing important weight and cost issues. For high bypass ratio engines this results in high demands for the low pressure turbine component. The combination of a low speed parameter due to large fan diameters with reduced number of turbine stages due to weight and cost considerations leads to high stage loading requirements. Realizing high turbine efficiencies at low Reynolds Number operation at high altitudes for these high stage loadings is a key for state-of-the-art turbofan engines. For the aerodynamic design, high stage loading factors directly translate into increased airfoil flow turning. These increased turning levels have to be realized in combination with elevated airfoil load in order to keep low airfoil counts. This is particularly challenging in combination and requires minimization of negative effects on the airfoil losses and secondary losses. In this paper the development of a five-stage turbine with high stage loading is discussed with focus on the aerodynamic design. A specially designed cascade test has been part of the turbine design, which showed the need for improvement of the transition modeling within the CFD code used for design and analysis. The derived modeling enhancement is then employed for the analysis of the five-stage rig, which was tested at the altitude test facility at Stuttgart University. The modeling achieved significant improvements in the quality of the numerical results. The analysis includes sensitivities to Reynolds number and a detailed view of the suction side flow.© 2005 ASME

Impact of Engine Cycle Selection on Propulsion System Integration and Vehicle Performance for a Quiet Supersonic Aircraft

Abstract: The overall propulsion system design and airframe integration process for an air- breathing gas turbine powerplant is strongly influenced by the selected engine cycle. This is especially true for supersonic cruise vehicles for which even subtle changes to cycle design characteristics can have a significant impact on propulsion system size as well as installed performance and operability. This sensitivity to the selected engine cycle requires particular care in trading among the primary cycle design objectives to produce a viable vehicle configuration. Gulfstream Aerospace Corporation and Rolls-Royce/Allison Advanced Development Company have performed an analytical assessment comparing the installed high-speed flight characteristics of two turbofan-based propulsion systems, one configuration employing an advanced highly variable cycle and the other a more conventional high bypass cycle. The system study aircraft selected for this effort is a 100,000 lb takeoff weight, multi-use platform employing twin over-wing podded engine nacelles and designed for extended cruise at Mach 1.8 with low supersonic cruise noise signature. Metrics compared between the two vehicle configurations include mission range, fuel burn, time-to- climb, engine airflow, and nacelle geometry. Opportunities for improved airframe integration enabled by the unique features of the highly variable cycle are discussed.

Unique challenges for bolted joint design in high-bypass turbofan engines

Abstract: Bolted joints are used at numerous locations in the rotors and carcass structure of modern aircraft turbine engines. This application makes the design criteria and process substantially different from that used for other types of machinery. Specifically, in addition to providing engine alignment and high-pressure gas sealing, aircraft engine structural joints can operate at high temperatures and may be required to survive very large applied loads which can result from structural failures within the engine, such as the loss of a fan blade. As engine bypass ratios have increased in order to improve specific fuel consumption, these so-called Ultimate loads increasingly dominate the design of bolted joints in aircraft engines. This paper deals with the sizing and design of both bolts and lever flanges to meet these demanding requirements. Novel empirical methods, derived from both component test results and correlated analysis have been developed to perform strength evaluation of both flanges and bolts. Discussion of analytical techniques in use includes application of the LS-DYNA code for modeling of high-speed blade impact events as related to bolted joint behavior.

The Design, Development and Commissioning of a Test Capability for Studying Cruise Noise

Abstract: During cruise, the jet mixing noise sources of commercial airliners are relatively weak. However, the jet exhausts of turbofan engines become supercritcal in cruise and quite strong shock noise can be generated. Under these conditions shocks form in a regular pattern in the exhaust plume and their interaction with the jet turbulence generates shock-associated noise, the presence of which is well known on military aircraft. To satisfy the cruise noise requirements of airlines and aircraft manufacturers, methods of reducing or alleviating the shock noise, which is broadband in character and of relatively high frequency, are being pursued. As little is known of shock noise specific to modern high-bypass ratio turbofan engines, an experimental research programme has been carried out at model-scale in the enhanced Noise Test Facility at QinetiQ, Farnborough. This paper describes the design concepts and constraints together with commissioning tests, including noise cancellation using hot-films, source location measurements, and measurements of shock noise spectra at cruise conditions.