The influence of a radial turbine volute on back-disk impingement cooling performance

Due to the restricted size of micro-gas turbines, the difficulty of cooling their radial turbines and raising their inlet temperature has been an ongoing focus in their research. In this paper, a back-disk impingement cooling technology for radial turbines is proposed. The study focuses on the influence of the non-uniform circumferential flow field generated by radial turbine volutes on the back-disk’s cooling characteristics. The study was carried out by using a conjugated heat transfer numerical simulation method. The results showed that the circumferential non-uniform distribution of the flow field caused by the volute can significantly impact the relative distribution of cooling efficiency across the surface of the back-disk and can decrease the average cooling efficiency of the back-disk surface by 1.8–6.0% in comparison with when the flow field is uniform. Back-disk jet cooling reduces the efficiency of a turbine and, if the volute is generating a non-uniform flow field, this further decreases the turbine’s efficiency. It was found, however, that the influence of back-disk jet cooling on the expansion ratio of the turbine can be ignored.