An Investigation Of Transpiration Cooling Performance In Curve Boundary Layer

Through a combined approach of experimental investigation with numerical simulation, two aspects of transpiration cooling have been investigated. The 1st aspect contains the performances of the fluid flow and heat transfer within the boundary layers on a curve structure surface with transpiration cooling function; the 2nd aspect includes the simulation of the injected coolant flow to cool two different structures, a rectangular nose and a hemispherical nose, under the condition of free flow heating at high Mach numbers.Transpiration cooling via porous media is a very effective way. The first part of this thesis is focused on the experiment and simulation of transpiration cooling performances. The specimen used in this experiment is made of sintered refractory steel, which has a porosity of 0.37 +0.01 and a character length of 30μm. In the experiment, the temperature and velocity of the free flow are controlled by two digital control systems in a hot gas wind tunnel, a velocity controller and a temperature controller. The Reynolds number of gaseous coolant is given by a digital mass flow rate controller. The surface temperature on the specimens is captured by an infrared thermal imaging system, NEC TH5104.Using a two-dimensional, steady, and local thermal equilibrium model in the commercial software FLUENT 6.3, transpiration cooling performance of the specimen is numerically simulated under the same conditions with the experiment. Through comparison of the numerical results with the experimental data, the numerical program is validated. With the help of the validated program, the performances of the fluid flow and heat transfer within the boundary layers on the curve structure surface are discussed.At a supersonic free flow, the shock wave leads to a gas heating on the blunt nose, which will be more serious when increasing the Mach number of the free flow. Concerning this problem, the second part of this thesis is focused on the simulation of the shock wave and transpiration cooling performances of the rectangular nose and hemispherical nose structures. With the comparison of the two structures, the differences of the flow field and the temperature field are also illustrated by the simulation with the FLUENT program. The results indicate that the cooling film covered on the structure surfaces can prevent the penetrating of the gas heating into the blunt noses, which protects effectively the nose bodies.