Theoretical and experimental evaluation of temperature drop and power consumption in a cover-plate pre-swirl system for gas turbine cooling

The pre-swirl system has the ability to decrease the air supply temperature so as to improve the cooling performance and the operating life for turbine rotating blade. In this paper, a test rig was designed to reveal the aero-thermal characteristics in a cover-plate type pre-swirl system of gas turbine engines. Then, the theoretical derivation and experimental evaluation were conducted to reveal the variation of temperature drop and power consumption of a pre-swirl system with the mass flow rate ratio and rotating speed. Especially, the pressure and temperature on the rotating turbine disc were measured by a co-rotating data recorder. The theoretical and experimental analyses indicate that the temperature drop of pre-swirl system increases as the velocity coefficient of the pre-swirl nozzle outlet enhanced, but presenting a decrease with the increment of the rotating Mach number. Then, the ideal dimensionless temperature drop can be formally unified with the actual dimensionless temperature by defining the tangential velocity recovering coefficient, which is verified with the experimental results. Moreover, a linear relationship between the dimensionless temperature drop and the effective swirl ratio at the nozzle outlet can be deduced further. Especially, this relationship shows a good agreement between the predicted values and numerical results. Since the dimensionless temperature drop decreases with the increase of the dimensionless power consumption; an important discovery can be concluded that the algebraic sum of these two physical quantities is always equal to 1. Therefore, the results can offer a reference for the design and optimization of gas turbine cover-plate type pre-swirl system.