Pre-Swirl System Design Including Inlet Duct Shape by Using CFD Analysis

Abstract

Fluid characteristics of two different types of duct shapes were studied and the pre-swirl nozzle was designed for partial annulus duct shape by using computational fluid dynamics. The fully annulus inlet duct shape and partial annulus inlet duct shape which are installed in front of the pre-swirl nozzles were compared from aerodynamic perspective. The new pre-swirl nozzle was designed for partial annulus inlet duct shape to resolve aerodynamic disadvantage of partial annulus duct. Design process of new pre-swirl nozzles included the optimization process to maximize the discharge coefficient. Three different pre-swirl system were compared using the discharge coefficient, swirl ratio and temperature drop. The experiments of base pre-swirl system were conducted to validate the CFD methodology and to predict the real pre-swirl system. The scale of experimental rig was one half of real pre-swirl system. As a results, the partial annulus duct with previous pre-swirl nozzles showed 1.1% lower discharge coefficient compared with the fully annulus duct. The new designed pre-swirl nozzle with partial annulus duct increased the discharge coefficient about 1.43% than the case of partial annulus duct with previous pre-swirl nozzle, and showed 0.4% lower discharge coefficient compared with the fully annulus duct shape. The swirl ratio was same through the three pre-swirl models because the three models had the same throat area. The temperature drop was measured between the inlet duct and the exit of receiver holes. In the cases of partial annulus inlet duct, the temperature drop was lower than the fully annulus inlet duct case. The new pre-swirl nozzles could resolve the aerodynamic loss occurred in the case of partial annulus duct with previous nozzles.