Numerical investigation of flow and heat transfer characteristics in radial pre-swirl system with different pre-swirl nozzle angles

The effect of pre-swirl nozzle angle (theta) on the flow and heat transfer characteristics of a radial pre-swirl system is numerically investigated using the CFD software ANSYS-CFX. In this paper, six pre-swirl nozzle angles are selected to study the flow dynamics of the radial pre-swirl system in terms of the flow structure, the nozzle exit flow angle, the air swirl ratio at nozzles outlet and receiver holes inlet, the total pressure loss coefficient in the nozzle and the cavity, the discharge coefficient of the nozzles and receiver holes and the adiabatic effectiveness. It is shown that the case of theta = 20 degrees exhibits the best performance in adiabatic effectiveness and total pressure loss in this system, while the case of theta = 60 degrees provides a maximum in discharge coefficient of receiver holes that is slightly higher than that of theta = 20 degrees. Comparatively, the case of theta = 20 degrees provides the best performance of the radial pre-swirl system. In addition, the effect of pre-swirl nozzle angle on the heat transfer characteristics is also presented. Results show that the heat transfer on the rotor disk is dominated by the flow structure and tangential velocity differential, and the peak in heat transfer coefficient can be observed near the receiver hole. (C) 2016 Elsevier Ltd. All rights reserved.