Advanced Calculation Method for the Surface Temperature Distribution of Turbine Blades

Abstract

A method of solution of the thermal boundary layer equation for a gas, together with the heat conduction equation for the turbine blade, using the boundary condition of the fourth kind (conjugate problem), is presented. The effect of the surface temperature distribution on the heat transfer coefficient (the effect of thermal history) is considered. This effect is important for gas turbine blades because the difference in temperatures between the blade’s surface and gas usually varies considerably along the blade’s surface; hence, the effect of thermal history can be significant. It is shown that the results, obtained accounting for thermal history, can differ substantially from results calculated with the assumption that the blade’s surface is isothermal. This might be one of the reasons why there is a marked difference between the actual temperature distribution of the turbine blade and the calculated one. It is important to consider the effect of thermal history since it is a fact that the major unknown in the design of turbine blade cooling systems is in the estimation of external heat transfer coefficient (Hannis and Smith, 1989).

Effects of an unsteady thermal boundary condition on forced convection heat transfer

“…Mathematically the forced convection heat transfer problem is an initial and boundary value problem. Thus, if the flow field is given, the heat transfer characteristics are determined by the thermal boundary conditions; in fact, the effects of the thermal boundary condition for a flat plate or a blade can generally be evaluated by employing the boundary layer approximation [1][2][3]. However, the thermal boundary conditions employed in most previous studies, except for the simple cases mentioned above, were limited to an isothermal or a uniform heat flux condition.…”