Numerical and experimental investigation of a cooling technique of a turbocharger radial turbine

Microgas turbines are still limited in performance due to the difficulty of applying cooling systems to the radial turbines (RT). This paper proposes and investigates a cooling solution, which is a new scheme of circulating cooling air inside the RT disc. This solution can be easily manufactured or applied to existing RTs. Therefore, this solution is tested on an existing RT, starting by analyzing the temperature distribution inside the turbine blades without the cooling solution, which reveals the zones of the highest temperature where the cooling air circulation must be applied. The cooling air is supplied from the compressor through the turbine shaft. This study was carried out using both numerical heat transfer simulation and experimental tools. An experimental microgas turbine test bench using a turbocharger was built to estimate the boundary conditions and validate CFD simulations. The latter, which are based on the conjugate heat transfer (CFD_CHT), were applied to provide the temperature distributions and the flow behavior. The results show that the proposed solution can significantly reduce the disc temperature (about 60 °K) near the inlet, which is detected as the hottest zone, in contrast to the temperature of the blade tip. The analyses of the turbine performance show that the proposed solution reduces slightly the isentropic efficiency (lower than 2