Abstract
This paper reports an analysis on leading edge impingement cooling of a turbine blade under real operation conditions of gas turbine. In the experiments, both mainstream and cooling air are heated to real high temperatures, and overall cooling effectiveness on the external blade mid-span surface is measured. Numerical strategy including RNG k-epsilon turbulence model is validated by the experimental data. Impingement cooling models with and without separators (Model A and Model B) are used as specimens, and the effects of high temperature conditions, separators and temperature ratios are discussed. The results indicate that: 1) When jet Reynolds number, mass flow ratio and temperature ratio are matched to the real conditions, the Nusselt numbers predicted by low temperature conditions can be generally matched, exclude the forepart of the internal surface at the blade leading edge. But the error of overall cooling effectiveness on the blade external surface is not neglected. 2) The application of separators can prevent the heat transfer deterioration caused by cross flow with extending the heat exchange area, thus the leading edge with separators can be further cooled over 30 K compared to the traditional design. 3) Under the real operating conditions of gas turbine, two new correlations between the surface averaged Nusselt number with jet Reynolds number and temperature ratio are suggested.
NSTL
Elsevier