The Influence of Low Solidity Vaned Diffusers on the Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute

Abstract

The paper is a sequel to an earlier work by Sorokes et al. 1998, “Investigation of the Circumferential Static Pressure Non-Uniformity Caused by a Centrifugal Compressor Discharge Volute.” The earlier work described experimental and computational fluid dynamics analyses of the non-uniform static pressure distortion caused by the discharge volute in a high pressure, centrifugal compressor with vaneless diffusers. This paper describes additional testing and analytical work done using low solidity vaned diffusers (LSD’s) in place of select vaneless diffusers to determine the alternate diffuser’s effectiveness in eliminating or reducing the magnitude of the non-uniform pressure field. As in the earlier studies, the experiments described in this paper were done using a heavily instrumented gas re-injection compressor operating at over 6000 psia discharge pressure. Instrumentation was installed to measure static, total, and dynamic pressure as well as impeller strain and mechanical vibrations. A brief description of the compressor and instrumentation are provided. Concurrent with the experimental work, CFD runs were completed to study the effect of the alternate vaned diffusers. The CFD pressure profile trends agreed well with the experimental results and provided analytical corroboration for the conclusions drawn from the test data. Conclusions are drawn regarding: a) the effectiveness of the LSD’s on the pressure non-uniformity; b) the associated effects on the measured dynamic strains in the impellers; and c) the usefulness of computational fluid dynamics (CFD) in assessing the aerodynamic forces associated with the non-uniformity.

Influence of the volute on the flow in a centrifugal compressor of a high-pressure ratio turbocharger

“…Installing low solidity vanes in the diffuser as a method to reduce the impact of the static pressure distribution on the impeller flow field was introduced by Sorokes and Koch [14]. Steglich et al [15] developed an asymmetric diffuser with an internal volute.…”

“…Based on the gained insights about the volute and its influence, different approaches were investigated to decouple the compressor from the volute influence or to diminish its impact, respectively. Installing low solidity vanes in the diffuser as a method to reduce the impact of the static pressure distribution on the impeller flow field was introduced by Sorokes and Koch [14]. Steglich et al [15] developed an asymmetric diffuser with an internal volute.…”

A new 1D method for assessing volute induced circumferential pressure distortion at the exit of a centrifugal impeller

“…Furthermore, pressure distortion causes additional radial forces, increasing the bearings' load and even being suspected to induce vibrations (Sorokes et al, 1998). While often negligible at atmospheric inlet conditions, in high-pressure applications the circumferential distribution of static pressure may be crucial for mechanical operation (Sorokes and Koch, 2000). However, there are only few publications addressing impeller-volute interaction.…”