Cooling in a centrifugal compressor can improve the performance and reduce the impeller temperature. In a centrifugal compressor, external walls can be cool down, which is known as the shell cooling. This method avoids undesirable effects induced by other cooling methods. Cooling can be applied on different external walls, such as the shroud, diffuser or the back plate. This paper focuses on seeking the most effective cooling place to increase the performance and reduce the impeller temperature. It is found that shroud cooling improves the compressor performance the most. Shroud cooling with 2400 W of cooling power increases the pressure ratio by 4.6% and efficiency by 1.49%. Each 500 W increase in the shroud cooling power, increases the efficiency by 0.3%. Diffuser cooling and back plate cooling have an identical effect on the polytropic efficiency. However, back plate cooling increases the pressure ratio more than diffuser cooling. Furthermore, only back plate cooling reduces the impeller temperature, and with 2400 W of cooling power, the impeller temperature reduces by 45 K.
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.
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