Numerical analysis on multiple parameters for overall cooling effectiveness of impingement effusion cooling with low Reynolds number.

Research on gas turbine cooling features is extensive, yet studies focused on conventional Reynolds numbers (Re) cannot effectively address the impact of low Re on blade cooling performance, especially relevant for high-altitude unmanned aerial vehicles operating under extremely low Re. In the current study, conjugate heat transfer simulations with Computational Fluid Dynamics (CFD) are used for the cooling performance analysis of an impingement effusion cooling structure with five Re ranging from 2e4 to 4e5, and three blowing ratios as 0.5, 1.0, and 1.5. Initially, a one-dimensional conjugate heat transfer model incorporating four dimensionless parameters is established, analyzing the impact of Re on these parameters. Innovatively, the study explores the mechanism of changes in overall cooling effectiveness through the variation of these dimensionless parameters. Finally, sensitivity analysis with partial derivations is conducted to find each parameter's contribution to the variation in overall cooling performance with Re differences. The CFD simulations of the impingement effusion cooling structure indicate a significant decrease in overall cooling effectiveness with the decrease of Re. The heat transfer ratio and warming factor differed a lot with varied Re. However, the variation in film cooling effectiveness is relatively small due to the mutual influence of coolant coverage and boundary layer distribution characteristics. According to partial derivative values, overall cooling effectiveness is highly sensitive to adiabatic film cooling effectiveness and Biot numbers. However, the heat transfer coefficient ratio and warming factor undergo substantial changes with varied Re , significantly impacting the overall cooling effectiveness. Thus, as Re decreases, the deterioration in internal cooling becomes the primary factor in the decline of overall cooling performance, suggesting targeted efforts to enhance internal cooling performance are recommended. • Overall cooling performance is lower with small Re than that with conventional Re. • Lateral coverage offsets streamwise deficiencies at low Re for adiabatic film cooling. • Heat transfer coefficient ratio is critical role in lower overall cooling performance with low Re. [ABSTRACT FROM AUTHOR]