Experimental Study on Pressure Losses in Porous Materials

Recent technological advances in the field of additive manufacturing have made possible to manufacture turbine engine components characterized by controlled permeability in desired areas. These have shown great potential in cooling application such as convective cooling and transpiration cooling and may in the future contribute to an increase of the turbine inlet temperature. This study investigates the effects of the pressure ratio, the thickness of the porous material, and the hatch distance used during manufacturing on the discharge coefficient. Moreover, two different porous structures were tested, and in total, 70 test objects were investigated. Using a scanning electron microscope, it is shown that the porosity and pore radius distribution, which are a result from the used laser power, laser speed, and hatch distance during manufacturing, will characterize the pressure losses in the porous sample. Furthermore, the discharge coefficient increases with increasing pressure ratio, while it decreases with increasing thickness to diameter ratio. The obtained experimental data were used to develop a correlation for the discharge coefficient as a function of the geometrical properties and the pressure ratio.