This paper presents a one-dimensional model to calculate the cooling flow of fully impingement cooled blades. The coolant is assumed to be ejected through a jet array running along the whole blade chord, with crossflow in the blade-to-blade plane from the leading edge toward the trailing edge. The simplicity of this cooling scheme translates to analytic formulations highlighting the peculiarities of impingement and the influence of geometric and fluid-dynamic parameters.
Results show that the coolant flow required to maintain the blade surface under a given maximum temperature varies strongly with the jet-to-jet spacing, while the jet-to-wall gap mainly affects pressure losses. Compared to other types of convection, impingement does not afford reductions of cooling flow nor pressure losses: the basic benefits are the capability to achieve high local heat transfer coefficients and more uniform temperature distributions.
Since the cooling schemes of actual gas turbine blades are substantially more complex — an elaborate combination of convection, impingement and film cooling — the present model cannot be used to predict the cooling flow required by actual engines. Nonetheless, it can give quantitative indications on the potential of impingement and help the selection of impingement array geometry.
Cooling Flow Prediction for Fully Impingement Cooled Gas Turbine Blades
