Study on analogy principle of overall cooling effectiveness for composite cooling structures with impingement and effusion

Abstract

The overall cooling effectiveness, which represents the distribution of dimensionless temperature on gas turbines surface, is an important parameter for conjugate heat transfer analysis of gas turbines. Generally, it is difficult to measure the overall cooling effectiveness in engine condition. However, the overall cooling effectiveness can be measured in the laboratory by matching the appropriate parameters to those in engine condition. Thus, it is important to evaluate the key parameters of matching methods. In this paper, the effects of adiabatic film effectiveness and Biot number on the overall cooling effectiveness were investigated with an impingement/effusion model by numerical simulation, in which 3-D steady RANS approached with the k–ω SST turbulence model was used. The tested plate had 8 cylinder hole rows with 30 degree inclined angle, and the internal cooling employed staggered array jet impingements. The matching performance was evaluated by comparing the results in typical engine condition and laboratory condition. The analogy principles were discussed in detail. The results show that the overall cooling effectiveness can be matched by using suitable matching principle in different lab conditions. The theoretical analysis was verified by numerical results. The distributions and values of overall cooling effectiveness can be matched well between engine condition and lab condition by matching temperature ratio, mainstream side Biot number and blowing ratio. If the temperature ratio is mismatched, the momentum flux ratio will be an important parameter for overall cooling effectiveness, because matching momentum flux ratio can reduce the difference of the adiabatic cooling effectiveness and the heat transfer coefficient ratio between engine condition and laboratory condition.