The Influence of Cooling Air Ejection on Flow Development and Heat Transfer in a Rotating Leading Edge Coolant Duct of a Film-Cooled Turbine Blade

Kurzfassung

With increasing turbine inlet temperature, the cooling of gas turbine components exposed to the hot gas flow will be of great importance. The improvement of the efficiency demands higher performance from the blade cooling systems with minimized coolant flow rates to cope with the increase in heat load as well as to meet the obligatory safety requirements. This calls for very accurate knowledge of the gas and coolant side flow and heat transfer, which both affect the blade temperature field, in order to obtain an efficient cooling design. This paper provides information about rotational effects on fluid motion and heat transfer within a rotating coolant duct of circular cross section with bleeding of cooling air through a row of film cooling holes for the purpose of film cooling of the hot gas side of the blade. Experimental data were obtained from a model mounted to the rotating duct facility at DLR. Flow development were measured by a non-intrusive optical Laser velocimeter. Wall temperature distributions around the duct wall and the generated heat were measured to provide data for local heat transfer analysis. The direction of bleeding is varied against the direction of rotation to study its effect on the development of secondary vortex structures which are generally caused within the flow by the rotational forces. Depending on the direction of bleeding, secondary vortex motion as well as heat transfer variation around the duct circumference are enhanced with pressure side ejection or weakened with suction side ejection.