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.

Incorporating Risk into Control Design for Emergency Operation of Turbo-Fan Engines

Abstract: The paper describes a risk function based approach to constrained turbo-fan engine control to facilitate aircraft emergency maneuvering during take-off or landing. With this approach, the pontwise-in-time state and control constraints limiting the engine thrust response can be intelligently relaxed depending on the individual engine condition monitoring. The proposed control functionality uses the barrier Lyapunov functions, the predictive reference governor and functional limiters. The approach is illustrated using simulations on a linearized and on a fully nonlinear NASA C-MAPSS40k turbo-fan engine model. The capability and flexibility of the design approach to provide fast thrust response while handling multiple constraints, that may be time-varying and dynamically changing, by coordinating multiple engine actuators is demonstrated.

Towards replacement of turbofan engines afterburners with pulse detonation devices. I

Abstract: The feasibility of placing pulse detonation devices in the rear of a turbofan engine as a new pulse detonation afterburner concept (PDAC) has been assessed in the present study for a given sea level static power condition and an engine size. A turbofan engine with a pulse detonation afterburner was studied and its performance was obtained. The thrust, SFC and specific thrust of a turbofan engine with a conventional afterburner and with the new pulse detonation afterburner concept were calculated and compared. The turbofan engine performance with the new pulse detonation afterburner concept was obtained using multidimensional CFD and cycle analysis as a function of the engine core flow fraction passing through the pulse detonation device. The results showed that the engine performance, in terms of total thrust, SFC and specific thrust, is improved as the engine core flow fraction allowed in the pulse detonation chamber is increased. However, the predicted total thrust, SFC and specific thrust of the turbofan engine with a pulse detonation afterburner fall short than those of a turbofan engine with a conventional deflagration combustion afterburner. The reduction in the turbofan engine performance with a pulse detonation afterburner was attributed to the reduction in initial mixture fuel-air ratio as the core flow products fraction inside the detonation chamber is increased and the neglect of the pulse detonation exhaust stream momentum in the thrust analysis. An analysis, which would address the pulse detonation exhaust stream momentum and the engine nozzle performance, is therefore warranted. 1 Member AIAA Copyright © 2001 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. NOMENCLATURE A = constant cross-sectional area A/B = afterburner Favg = average thrust FPR = fan pressure ratio F = cycle frequency Mmass = mass averaged Mach number OPR = overall pressure ratio P(t) = unsteady pressure at the tube wall Pdrag = pressure acting on left side of thrust wall Pmass = niass averaged initial mixture pressure PPH = Ibm/hr SFC = specific fuel consumption Tcycie = cycle time Tdetonation= detonation time Tfin = filling time = initiation time = mass averaged initial mixture temperature = purging time t = time yi = mixture mass fraction = mixture equivalence ratio

Continuous-Scan Phased Array Measurement Methods for Turbofan Engine Acoustic Testing

Abstract: Imaging of aeroacoustic noise sources is routinely accomplished with geometrically fixed phased arrays of microphones. Several decades of research have gone into improvement and optimization of sensor layouts, selection of basis models, and deconvolution algorithms to produce sharper and more localized images of sound-producing regions in space. This paper explores an extension to conventional phased array measurements that uses slowly, continuously moving microphone arrays with and without coupling to rigid fixed arrays to improve image quality and better describe noise mechanisms on turbofan engine sources such as jet exhausts and turbomachinery components. Three approaches are compared in the paper: fixed receiver beamforming (FRBF), continuous-scan beamforming (CSBF), and multireference CSBF (MRCSBF). The third takes advantage of transfer function matrices formed between fixed and moving sensors to achieve effective virtual arrays with spatial density one to two orders of magnitude higher, with practical sensor budgets and scan speeds. The MRCSBF technique produces array sidelobe rejection that approaches the theoretical array pattern of a continuous 2-D aperture. The implications of this finding are that better source localization may be achieved with conventional delay and sum (DAS) beamforming (BF) with practical sensor budgets, and that an improved starting image of the sound source can be provided to deconvolution algorithms. These findings are demonstrated on analytical and experimental examples from a low-cost rotating phased array using point sound sources, as well as linear scanning array experiments of an impinging jets point source and a near-sonic jet nozzle exhaust.

Turbofan in air conditioner

Abstract: An object of the present invention is to provide a turbofan in an air conditioner, which facilitates unitary formation of a turbofan, and easy formation of a turbofan mold, and has a longer lifetime of the mold. Another object of the present invention is to provide a turbofan in an air conditioner, which can minimize noise produced during operation of the turbofan. To achieve these and other objects of the present invention, there is provided a turbofan in an air conditioner including a base plate having a hub at a center thereof for coupling to a shaft of a driving motor, a plurality of blades disposed at a periphery of the base plate at fixed intervals along a circumferential direction, and a shroud including an inlet side end part formed in parallel to the shaft, and fitted to ends of the blades 40 to connect the ends, having an inside diameter equal to, or greater than an outside diameter of the base plate, a shoulder part extended outward in a radial direction from an inside circumference of the inlet side end part, and a sloped part extended outward in a radial direction, and sloped downward, from an end of the shoulder part.

Steady Performance Measurements of a Turbofan Engine With Inlet Distortions Containing Co- and Counter-Rotating Swirl From an Intake Diffuser for Hypersonic Flight

Abstract: The influence of distorted inlet flow on the steady and unsteady performance of a turbofan engine, which is a component of an air-breathing combined propulsion system for a hypersonic transport aircraft, is reported in this paper. The performance and stability of this propulsion system depend on the behavior of the turbofan engine. The complex shape of the intake duct causes inhomogeneous flow at the engine inlet plane, where total pressure and swirl distortions are present. The S-bend intakes are installed axisymmetrically left and right into the hypersonic aircraft, generating axisymmetric mirror-inverted flow patterns. Since all turbo engines of the propulsion system have the same direction of rotation, one distortion corresponds to a corotating swirl at the low pressure compressor (LPC) inlet while the mirror-inverted image counterpart represents a counterrotating swirl. Therefore the influence of the distortions on the performance and stability of the CO' and COUNTER' rotating turbo engine are different. The distortions were generated separately by an appropriate simulator at the inlet plane of a LARZAC 04 engine. The results of low-frequency measurements at different engine planes yield the relative variations of thrust and specific fuel consumption and hence the steady engine performance. High-frequency measurements were used to investigate the different influence of CO and COUNTER inlet distortions on the development of LPC instabilities.