Performance Investigation Into Supersonic Diffuser for a High Pressure Centrifugal Compressor

Abstract

In high pressure centrifugal compressors, the overall stage performance is greatly influenced by its diffuser performance. Extremely complicated non-uniform and unsteady flow exists in the region between the impeller exit and the diffuser inlet. Furthermore, in the case of supersonic diffuser, shock waves can be observed near the diffuser inlet. These can cause aerodynamic losses. Therefore, it is essential to recognize such complicated flow to realize an appropriate diffuser design. An investigation into the performance of supersonic diffuser was carried out using a high pressure compressor test rig for a small industrial gas turbine with a high back swept impeller and a quasi pipe-shaped channel diffuser. In addition, 3D quasi-unsteady flow analyses of the entire compressor by a RANS code with Non Linear Harmonic method at several operating conditions between surge and choke were conducted to investigate the details of unsteady flow between the impeller exit and the diffuser exit. The results of the performance test and that of the 3D unsteady flow analyses have shown good agreement in the pressure rise and the isentropic efficiency at several operating conditions. These support high accuracy of the flow analyses and the performance measurements.

Transient Analysis of Flow Unsteadiness and Noise Characteristics in a Centrifugal Compressor with a Novel Vaned Diffuser

“…Industrial compression systems are increasingly demanded in various applications, which include petrochemical, automotive engines, power plants, and aircraft gas turbine. Single or multistage centrifugal compressors play an important role in such applications to compress the working fluid [1][2][3]. The growth of global air traffic and increasing number of constraints in relation to fuel consumption require the stage loading to be increased, and the centrifugal compressor size to be reduced.…”

Investigation of two pipe diffuser configurations for a compact centrifugal compressor

“…A comparison of predicted and measured flow fields was conducted in detail and strong agreement was found. The unsteady impeller-diffuser interaction and the transit phenomena in pipe diffuser passages were investigated by Grates et al, 5 Sugimoto et al, 6 and Wilkosz et al 7 by means of both experimental and numerical methods. Strong agreement was shown between the time-averaged predicted results and the test data.…”