Robustness Analysis on Aerothermal Performance of the Winglet Squealer Tip—Part II: Heat Transfer Performance

Abstract

This article is the second part of a robustness analysis of the aerothermal performance of the winglet structure. A challenging analytical test function and an engineering test are considered to further investigate the response performance of the efficient uncertainty quantification framework proposed in Part 1. Then, a series of original visualizing uncertainty quantities are proposed in this article and applied to the study of uncertainty quantification of the winglet structure. Finally, this efficient framework is applied to the uncertainty quantification of the effect of the conventional squealer tip and three different winglet squealer tips on the heat transfer performance of the GE-E3 rotor blade. According to the results of the uncertainty quantification calculation, in actual operation, the setting of the winglet structures will diminish rather than increase the heat transfer performance of the blade tip. This conclusion is completely opposite to the prediction of the deterministic calculation. The heat flux increase and standard deviation of squealer tip with pressure-side winglet are the highest among the four tip structures, which means that the robustness of heat transfer performance of squealer tip with pressure-side winglet is the worst. The parameter that has the greatest influence on the uncertainty of the heat transfer performance of the four tip structures is the tip clearance. But the influence of the inlet total temperature fluctuation must also be taken into account. So a satisfactory control system should be designed for the actual operation of the gas turbine so that the fluctuation of inlet total temperature can be attenuated rapidly. A positive correlation between the heat flux of the blade tip mean value and the standard deviation is revealed by the uncertainty quantification, which implies that reducing the heat flux of the blade tip mean value in the robust design of the blade tip tends to reduce the heat flux fluctuation as well. Therefore, the objective of the robust design of the blade tip can be either one of reducing the mean value of heat flux of the blade tip mean value or reducing the heat flux of the blade tip standard deviation without multi-objective optimization. It is worth noting that, like the aerodynamic performance uncertainty, there is an antagonistic relationship between the pressure-side cavity and suction-side cavity on the heat transfer performance uncertainty of the blade tip. Therefore, a reasonable ratio of pressure-side cavity to suction-side cavity in the turbine design can also lead to a blade tip with strong heat transfer performance robustness.