Transient experimental study on cooling performance of a radial turbine with impingement cooling in rotating state.

• A jet impingement cooling technology for radial turbines was proposed. • The temperature distribution on the surface of a rotating turbine was measured using an IR camera. • The wall temperature of the turbo wheel could be significantly reduced by consuming acceptable mass flow rates of the coolant. • The temperature distribution periodically fluctuates under the combined effects of cooling, rotation, and thermal inertia. Increasing the inflow temperature of a turbine is an effective approach for enhancing the thermal efficiency of devices operating in the Brayton cycle, such as micro-gas-turbines and waste heat recovery systems. However, elevated temperatures also pose a significant risk of thermal fatigue failure. This paper presents an experimental investigation of impingement cooling for radial turbines, aiming to achieve high cooling performance with a simple structure. High-frequency infrared thermal imaging technology was employed to measure temperature distribution in the turbine rotor under various operational conditions. The results indicate that jet-impingement cooling can substantially reduce the solid temperature of the radial turbine, with a maximum temperature reduction of approximately 44 K achieved by consuming the coolant with ṁ re = 5%. Increasing the mass flow rate of the coolant consistently lowers the rotor temperature; however, an increase in rotational speed results in higher thermal inertia, thereby diminishing the cooling enhancement effect. The temperature distribution on the turbine surface exhibits significant periodic characteristics over time, leading to temperature fluctuations of 5 K to 30 K at the hub position. Furthermore, the cooling performance is further enhanced near the jet hole on the back-disc side of the inducer region, while the tip side closer to the exducer obtains better cooling effects. [ABSTRACT FROM AUTHOR]