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.

An investigation of engine influence on inlet performance

Abstract: The performance of a conventional engine/inlet installation, in which inlet and engine flow field interaction occurs, was compared to the performance of the same inlet remote coupled to the engine. The remote coupled inlet configuration decouples the influence of the engine on the inlet flow field and simulates current small scale inlet test techniques in which inlet airflow is provided by a vacuum source or coupled engine. The investigation was conducted in the NASA-Ames 40- by 80-foot wind tunnel using a General Electric TF-34 turbofan engine and a subsonic inlet having an average inlet contraction ratio of 1.26. Test results indicated that engine interaction allows the inlet to operate with lower distortion levels at and beyond the separation angle-of-attack experienced without engine interaction.

Experimental operating range extension of a twin-spool turbofan engine by active stability control measures

Abstract: Modern engine operation is guided by the aim to broaden the operating range and to increase the stage loading allowing the stage count to be reduced. This is possible by active stability control measures to extend the available stable operating range. Different strategies of an active control system, such as air injection and air recirculation have been applied. While in the past results have been published mainly regarding the stability enhancement of compressor rigs or single-spool engines, this experimental study focuses on both the stability as well as the operating range extension of a twin-spool turbofan engine as an example of a real engine application on an aircraft. The objective of this investigation is the analysis of the engine behavior with active stabilization compared to unsupported operation. For this purpose, high-frequency pressure signals are used and analyzed to investigate the effects of air injection with respect to the instability onset progress and the development of any instabilities, such as rotating stall and surge in the low-pressure compression (LPC) system. These Kulite signals are fed to a control system. Its amplified output signals control fast acting direct-drive valves circumferentially distributed ahead of the LPC. For the application of air injection described in the paper, the air is delivered by an external source. The control system responsible for air injection is a real-time system which directly reacts on marked instabilities and their precursors. It allows the LPC System to recover from fully developed rotating stall by asymmetric air injection based on the pressure signals. Additionally, a delayed appearance of instabilities can be provoked by the system. Air injection guided by this control system resulted in a reduction of the required amount of air compared to constant air injection. Also, disturbances travelling at rotor speed can be detected, damped, and eliminated by this control system with a modulation of the injected air in such a way that the injection maximum travels around the ten injection positions.

Parametric fault modeling and diagnostics of a turbofan engine

Abstract: A parametric fault modeling and diagnostics approach of a turbofan engine is presented. The healthy engine model is obtained as a steady state map between input parameters representing engine operating conditions and output parameters governing engine performance characteristics. The fault modeling is conceptualized as either degraded engine performance levels or as sensor failures and both incipient and abrupt fault scenarios are considered. The fault parameters are successfully estimated using generalized least squares (GLS) techniques with the data obtained from several recorded flight data. Further, a nonlinear estimation method is introduced to improve the diagnostic performance in certain cases of large and abrupt failures.

Characteristics of the advanced supersonic technology AST-105-1 configured for transpacific range with Pratt and Whitney aircraft variable stream control engines

Abstract: Credence to systems weights and assurance that the noise study AST concept can be balanced were studied. Current titanium structural technology is assumed. A duct-burning turbofan variable stream control engine (VSCE), with noise reduction potential through use of a coannular nozzle was used. With 273 passengers, range of the AST-105-1 for a cruise Mach number of 2.62 is essentially transpacific. Lift-to-drag ratio is slightly higher than for previous AST configurations. It is trimmable over a center-of-gravity range of 4.7m (15.5 ft). Inherent high positive effective dihedral, typical of arrow-wing configurations in high-lift approach, would limit AST-105-1 to operating in crosswinds of 11.6 m/sec (22.4 kt), or less, with 75 percent of available lateral control. Normal power takeoff with cutback results in noise in excess of Federal Aviation Regulation Part 36 but less than for conventional procedure takeoff. Results of advanced (noncertificated) programmed throttle takeoff and approach procedures, not yet optimized, indicate that such can be an important additional method noise reduction.