Turbofan

About: Turbofan is a research topic. Over the lifetime, 4114 publications have been published within this topic receiving 39490 citations. The topic is also known as: fanjet & turbofan engine.

Full-Scale Turbofan-Engine Turbine-Transfer Function Determination Using Three Internal Sensors

Abstract: Existing NASA/Honeywell EVNERT full-scale static engine test data is analyzed by using source-separation techniques in order to determine the turbine transfer of the currently sub-dominant combustor noise. The results are used to assess the combustor-noise prediction capability of the Aircraft Noise Prediction Program (ANOPP). Time-series data from three sensors internal to the Honeywell TECH977 research engine is used in the analysis. The true combustor-noise turbine-transfer function is educed by utilizing a new three-signal approach. The resulting narrowband gain factors are compared with the corresponding constant values obtained from two empirical acoustic-turbine-loss formulas. It is found that a simplified Pratt & Whitney formula agrees better with the experimental results for frequencies of practical importance. The 130 deg downstream-direction far-field 1/3-octave sound-pressure levels (SPL) results of Hultgren & Miles are reexamined using a post-correction of their ANOPP predictions for both the total noise signature and the combustion-noise component. It is found that replacing the standard ANOPP turbine-attenuation function for combustion noise with the simplified Pratt & Whitney formula clearly improves the predictions. It is recommended that the GECOR combustion-noise module in ANOPP be updated to allow for a user-selectable switch between the current transmission-loss model and the simplified Pratt & Whitney formula. The NASA Fundamental Aeronautics Program has the principal objective of overcoming today's national challenges in air transportation. The Subsonic Fixed Wing Project's Reduce-Perceived-Noise Technical Challenge aims to develop concepts and technologies to dramatically reduce the perceived aircraft noise outside of airport boundaries. The reduction of aircraft noise is critical to enabling the anticipated large increase in future air traffic.

The methodology of stochastic optimization of parameters and control laws for the aircraft gas-turbine engines flow passage components

Abstract: This paper presents the main theses of stochastic approach to the multimeasure parameters and control laws optimization for the aircraft gas-turbine engines. The methodology allows us to optimize the engines taking into account the technological deflections which inevitably take place in the process of manufacturing of the engine's components as well as engine's control deflections. The stochastic optimization is able to find highly robust solutions, stable to inaccuracies in technological processes. The effectiveness of the methodology is shown by example of optimization problem solution to find the control laws for the flow passage controllable elements of the fourth generation aircraft mixed-flow turbofan engine. The use of information about the existing and advanced production technology levels during the optimization process, including some components manufacturing accuracy, allows us to considerably increase the probability of optimum solution implementation in practice. In real engine there are some components manufacturing deflections as well as control accuracy deflections. This results in a certain engine's performance deviation. An engine optimization classic deterministic approach cannot take into account this circumstance, so the probability of an optimum design implementation is too low.

Counter Rotating Fans—An Aircraft Propulsion for the Future？

Abstract: In the mid seventies a new propulsor for aircraft was designed and investigated-the so-called PROPFANWith regard to the total pressure increase,it ranges between a conventional propeller and a turbofan with very high bypass ratioThis new propulsion system promised a reduction in fuel consumption of 15 to 25% compared to engines at that timeA lot of propfans (Hamilton Standard,USA) with different numbers of blades and blade shapes have been designed and tested in wind tunnels in order to find an opimum in efficiency,Fig1Parallel to this development GE,USA,made a design of a counter rotating unducted propfan,the so-called UDF,Fig2A prototype engine was manufactured and investigated on an in-flight test bed mounted at the MD82 and the B727Since that time there has not been any further development of propfans (except AN 70 with NK 90-engine Ukraine,which is more or less a propeller design)due to relatively low fuel prices and technical obstaclesOnly technical programs in diferent countries are still going on in order to prepare a data base for designing counter rotating fans in terms of aeroacoustics,aerodynamics and aeroelasticitiesIn DLRGermany,a lot of experimental and numerical work has been undertaken to understand the physical behaviour of the unsteady flow in a counter rotating fan

Effects of installation caused flow distortion on noise from a fan designed for turbofan engines

Abstract: Far-field noise measurements were taken for three different installations of essentially the same fan. The installation with the most uniform inlet flow resulted in fan-blade-passage tone sound pressure levels more than 10 dB lower than the installation with more nonuniform inflow. Perceived noise levels were computed for the various installations and compared. Some measurements of inlet flow distortion were made and used in a blade-passage noise generation theory to predict the effects of distortion on noise. Good agreement was obtained between the prediction and the measured effect. Possible origins of the distortion were identified by observation of tuft action in the vicinity of the inlet.