Investigation into Transpiration Cooling of Blades in High-Temperature Gas Turbines

Among the methods for improving the performance of high-temperature gas turbines in gas-turbine engines (GTE) and gas-turbine units (GTU) is the implementation of transpiration cooling of the blades, since the maximum allowable temperature of blades with convective- or film-cooling ranges from 1800 to 1900 K. The basic advantage of this cooling method is in decreasing the required coolant flow due to extended-contact heat-transfer surface. Transpiration cooling systems employ porous metal materials. However, the effect of geometry of porous materials on air flow and heat transfer in them is still not clearly understood. The paper presents the results into investigation of models with a transpiration cooling system made of sintered stainless-steel fibers. The geometric characteristics of the investigated models depended on the material porosity. The thermal tests of the models were performed by the calorimetric method in a liquid-metal thermostat, while the hydraulic tests were carried out by the hot blow method under isothermal conditions. The experimental results can be entered into the database used by heat transfer software packages, thereby decreasing the labor intensity and time for designing a cooling system for gas turbine blades. The implementation of transpiration cooling offers the prospects for increasing the maximum allowable gas turbine temperature up to 2200 K.