Performance improvement of a high pressure ratio centrifugal compressor by integrated cooling

Abstract

Centrifugal compressors with high pressure ratio have been widely used in small gas turbines, industrial compressors and turbochargers. High mechanical stress and high temperature of the impeller and large compression power required are the key factors that limit the pressure ratio achieved by centrifugal compressors. Cooling is an effective way to reduce the required compression power and the impeller temperature and it is widely used in gas turbines and industrial compressors. In this work, a cooling method named integrated cooling was employed in a high pressure ratio centrifugal compressor. The effects of the integrated cooling on the compressor performance were studied by three-dimensional steady simulation with conjugate heat transfer method using ANSYS CFX commercial solver. It is found that integrated cooling is capable of improving the compressor performance with respect to pressure ratio, efficiency, compression power as well as the impeller maximum temperature. With a cooling temperature of 300 K, the pressure ratio increased by 11.0% and efficiency by about 2.44% at the design condition. Besides, the maximum impeller temperature decreased by about 67 K. This considerable improvement of the compressor performance justifies the integrated cooling, which helps to advance the design of high pressure ratio centrifugal compressors.

Comparison of Cooling Different Parts in a High Pressure Ratio Centrifugal Compressor

“…It has been set to be adiabatic in the numerical model, while in the experiment, it is very hard to control the heat transfer to surroundings, especially in a high pressure ratio. Moosania et al [14] reported that in a compressor, heat transfer to the surroundings considerably increases the compressor performances, especially in a high pressure ratio. Figure 6 illustrates the compressor total pressure ratio by cooling on different parts with varied cooling powers.…”

“…A secondary flow can flow inside some jackets attached to the walls to cool them down. Moosania et al [14] used shell cooling for all of the external walls in a centrifugal compressor. A huge improvement in the compressor performance, as well as a noticeable reduction in impeller temperature have been obtained by shell cooling.…”

A numerical investigation of the effect of vaned diffuser water cooling on the internal flow field of a centrifugal compressor

“…Heuer et al 3 successfully performed steady state CHT calculations combined with thermal stress analysis for a turbine housing and presented an optimization method in terms of stress reduction. Mostafa et al [4][5][6] analysed in detail the cooling of the external wall surfaces of different parts of a centrifugal compressor, including the casing, the vaneless diffuser and the backdisc, and found that integrated cooling could significantly improve the performance of the compressor in terms of pressure ratio, efficiency, compression power and maximum impeller temperature, and that the effect of the casing cooling was the most pronounced of the three. As turbine inlet temperature and compressor pressure ratio increase, there is a growing interest in cooling turbocharger more efficiently.…”