Experimental Testing and Numerical Analysis on the Nozzle Effects in Preswirl System

Abstract

The efficiency of a preswirled cooling air delivery system depends critically on the performance of the preswirl nozzle. To achieve the expected temperature drop, accurate prediction of the nozzle discharge behavior is quite essential. In the current study, the discharge coefficients of a cascade vane nozzle and a vane-shaped hole nozzle are tested in a simplified plate setup without a rotor. The influences of the pressure ratio and Reynolds number on the discharge behavior are investigated experimentally. The overall pressure ratio across the preswirl rig is varied from 1.1 to 1.9, and the Reynolds number is in the range of to . Numerical simulations are also performed to compare the flow characteristics and temperature drop between these two nozzles. Results indicate that the experimental and numerical data show good agreement for different conditions. Increasing the pressure ratio causes the deviation angle and discharge coefficient to increase. The discharge coefficient and preswirl effectiveness both increase first and then remain constant with the Reynolds number. In addition, the cascade vane nozzle and vane-shaped hole nozzle have similar discharge coefficients: both around 0.95. However, the vane-shaped hole nozzle benefits from its smaller deviation angle, resulting in a higher preswirl effectiveness and higher swirl ratio at the nozzle exit. Consequently, the vane-shaped hole nozzle gives an 8.7% improvement in temperature drop as compared with the cascade vane nozzle.