Axial compressor

About: Axial compressor is a research topic. Over the lifetime, 12035 publications have been published within this topic receiving 127766 citations.

Interaction of rim seal and annulus flows in an axial flow turbine

Abstract: A combined computational fluid dynamics (CFD) and experimental study of interaction of main gas path and rim sealing flow is reported. The experiments were conducted on a two stage axial turbine and included pressure measurements for the cavity formed between the stage 2 rotor disc and the upstream diaphragm for two values of the diaphragm-to-rotor axial clearance. The pressure measurements indicate that ingestion of the highly swirling annulus flow leads to increased vortex strength within the cavity. This effect is particularly strong for the larger axial clearance. Results from a number of steady and unsteady CFD models have been compared to the measured results. Good agreement between measurement and calculation for time-averaged pressures was obtained using unsteady CFD models, which predicted previously unknown unsteady flow features. This led to fest response pressure transducer measurements being made on the rig, and these confirmed the CED prediction.

Backward Traveling Rotating Stall Waves in Centrifugal Compressors

Abstract: Rotating stall waves that travel against the direction of rotor rotation are reported for the first time and a new, low-order analytical approach to model centrifugal compressor stability is introduced. The model is capable of dealing with unsteady radially swirling flows and the dynamic effects of impeller-diffuser component interaction as it occurs in centrifugal compression systems. A simple coupling criterion is developed from first principles to explain the interaction mechanism important for system stability. The model findings together with experimental data explain the mechanism for first-ever observed backward traveling rotating stall in centrifugal compressors with vaned diffusers. Based on the low-order model predictions, an air injection scheme between the impeller and the vaned diffuser is designed for the NASA Glenn CC3 high-speed centrifugal compressor. The steady air injection experiments show an increase of 25% in surge-margin with an injection mass flow of 0.5% of the compressor mass flow. In addition, it is experimentally demonstrated that this injection scheme is robust to impeller tip-clearance effects and that a reduced number of injectors can be applied for similar gains in surge-margin. The results presented in this paper firmly establish the connection between the experimentally observed dynamic phenomena in the NASA CC3 centrifugal compressor and a first principles based coupling criterion. In addition, guidelines are given for the design of centrifugal compressors with enhanced stability.Copyright © 2002 by ASME

Active Suppression of Rotating Stall and Surge in Axial Compressors

Abstract: This paper reports on an experimental program in which active control was successfully applied to both rotating stall and surge in a multi-stage compressor. Two distinctly different methods were used to delay the onset of rotating stall in a four stage compressor using fast acting air injection valves. The amount of air injected was small compared to the machine mass flow, the maximum being less than 1.0%. In some compressor configurations modal perturbations were observed prior to stall. By using the air injection valves to damp out these perturbations an improvement of about 4.0% in stall margin was achieved. The second method of stall suppression was to remove emerging stall cells by injecting air in their immediate vicinity. Doing this repeatedly delayed the onset of stall, giving a stall margin improvement of about 6.0%. Further studies were conducted using a large plenum downstream of the compressor to induce the system to surge rather than stall. The resulting surge cycles were all found to be initiated by rotating stall and therefore the stall suppression systems mentioned above could also be used to suppress surge. In addition, it was possible to arrest the cyclical pulsing of a compressor already in surge.Copyright © 1991 by ASME

Sources of Noise in Axial Flow Fans

Abstract: Experiments and theory relating to fan noise sources are reviewed with emphasis on axial flow machines At supersonic rotor speeds, the steady shock pattern attached to a rotor is an efficient radiator of sound In most practical cases of subsonic rotor operation, however, direct radiation from the rotor‐locked pressure field is negligible compared with the indirect radiation, or scattering, caused by circumferential distortions in the steady flow field surrounding the rotor Random timewise modulation of the distortion changes the scattered spectrum from discrete to continuous, with a gradual progression from narrow‐band tones to broad‐band noise as the modulation bandwidth is increased Similar scattering occurs when a non‐uniform unsteady flow impinges on stator vanes, but here the radiated frequency is that of the impinging flow Finally, for blades operating in flows free from circumferential distortions, self‐generated turbulence becomes an important source of noise The paper describes the physical mechanisms involved in each of these processes, including the generating of unsteady lift by turbulence Order‐of‐magnitude sound power estimates are compared, where possible, with experiment