Novel multi-stage vortex cooling with bypass for turbine blade leading edge design considering rotational effect

Abstract

This work aims to comprehensively improve vortex cooling performance by suggesting a novel design in the blade leading edges of gas turbines. Under considering the effect of blade rotation, different multi-stage configurations with bypass are proposed. A series of validated calculations are performed based on solving steady-state Reynolds Averaged Navier-Stokes equations and the SST k-ω turbulence model. Heat transfer and flow characteristics of the different vortex cooling structures are analyzed at different rotational speeds. From the results, it can be concluded that: (1) under stationary conditions, compared to the single-stage model, the multi-stage design of vortex cooling can greatly enhance the heat transfer rate, and its average Nusselt number can be 87.6% higher, but the cost is the high total pressure loss. Nevertheless, the comprehensive thermal performance in the multi-stage configuration is still 7.2% higher at least. (2) When blade rotates, the heat transfer rates in all configurations generally decrease by the effect of the Coriolis force (at least 8.8% when rotational number is 0.072). With the increase of rotational speed, the unfavorable high friction loss in multi-stage design is also decreased. For example, the total pressure loss coefficient in multi-stage vortex cooling without bypass is decreased by 68.4% when Rotational number increases to 0.072. (3) The bypass design in the multi-stage model provides an effective way to control the heat transfer enhancement and total pressure loss. At a high rotational number of 0.072, using a bypass with a thickness of 0.25 mm, although the averaged Nusselt number drops by 9.9%, the decrease of total pressure loss reaches to 117%. This phenomenon implies that a proper multi-stage vortex cooling model with bypass design can significantly decrease the friction loss, at a negligible price of heat transfer reduction.