Axial compressor

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

Experimental and Computational Investigation of the NASA Low-Speed Centrifugal Compressor Flow Field

Abstract: An experimental and computational investigation of the NASA Low-Speed Centrifugal Compressor (LSCC) flow field has been conducted using laser anemometry and Dawes' 3D viscous code. The experimental configuration consists of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational analysis, and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the rotor as well as surface flow visualization along the impeller blade surfaces provide independent confirmation of the laser measurement technique.

The instability of the boundary layer over a disk rotating in an enforced axial flow

Abstract: We consider the convective instability of stationary and traveling modes within the boundary layer over a disk rotating in a uniform axial flow. Complementary numerical and high Reynolds number asymptotic analyses are presented. Stationary and traveling modes of type I (crossflow) and type II (streamline curvature) are found to exist within the boundary layer at all axial flow rates considered. For low to moderate axial flows, slowly traveling type I modes are found to be the most amplified, and quickly traveling type II modes are found to have the lower critical Reynolds numbers. However, near-stationary type I modes are expected to be selected due to a balance being struck between onset and amplification. Axial flow is seen to stabilize the boundary layer by increasing the critical Reynolds numbers and reducing amplification rates of both modes. However, the relative importance of type II modes increases with axial flow and they are, therefore, expected to dominate for sufficiently high rates. The application to chemical vapour deposition(CVD) reactors is considered.

Tri-passage diffuser for a gas turbine

Abstract: In a gas turbine having a transition region between a combustor and turbine stage including a transition piece duct extending between a combustor liner and the turbine stage; an impingement sleeve surrounding the transition piece, the impingement sleeve having a plurality of apertures therein; and a compressor diffuser directing compressor discharge air into the transition region, an improvement wherein the diffuser includes a pair of outer walls flaring outwardly in a direction of compressor discharge air flow; and a pair of baffles within a flow area defined by the pair of outer diffuser walls which divide the flow area into three discrete flow passages. One passage has a substantially radial flow component; a second passage has both radial and axial flow components; and a third passage has a substantially axial flow component.

Self-Regulating Casing Treatment for Axial Compressor Stability Enhancement

Abstract: The operating range of an axial compressor is often restricted by a safety imposed stall margin. One possible way of regaining operating range is with the application of casing treatment. Of particular interest here is the type of casing treatment which extracts air from a high pressure location in the compressor and re-injects it through discrete loops into the rotor tip region. Existing re-circulation systems have the disadvantage of reducing compressor efficiency at design conditions because worked flow is unnecessarily re-circulated at these operating conditions. Re-circulation is really only needed near stall. This paper proposes a self-regulating casing treatment in which the re-circulated flow is minimized at compressor design conditions and maximized near stall. The self-regulating capability is achieved by taking advantage of changes which occur in the tip clearance velocity and pressure fields as the compressor is throttled toward stall. In the proof-of-concept work reported here, flow is extracted from the high pressure region over the rotor tips and re-injected just upstream of the same blade row. Parametric studies are reported in which the flow extraction and re-injection ports are optimized for location, shape and orientation. The optimized design is shown to compare favorably with a circumferential groove tested in the same compressor. The relationship between stall inception type and casing treatment effectiveness is also investigated. The self-regulating aspect of the new design works well: stall margin improvements from 2.2 to 6.0% are achieved for just 0.25% total air re-circulated near stall and half that near design conditions. The self-regulating capability is achieved by the selective location and orientation of the extraction hole; a simple model is discussed which predicts the optimum axial location. Copyright © 2011 by ASME.