CFD Analysis of S-Duct with Varying Area Distributions

Abstract

The ideal design of an intake S-duct (serpentine duct) of the jet engine should be able to supply adequate air regardless of the operating conditions of the aircraft, efficiently decrease the speed of incoming compressible flow and turn it to the desired location. Total pressure losses should be as low as possible and pressure recovery should be as high as possible. To maximize the efficiency, the vortex generated due to the two curvatures must be suppressed. This can be achieved by varying the area distribution of the duct which helps in isolating the effects of diffusion and curvature as much as possible. In this numerical analysis, six different serpentine intake ducts are designed with varying area distributions, but a constant centerline. The inlet area and the exit area are kept constant along with the centerline. Total pressure contours and transverse velocity contours are observed for flow in each duct to find the duct configuration with least losses. The geometry of a duct with least total pressure loss is considered as the duct with optimum area distribution. The inlet boundary condition is set as the velocity inlet condition with velocity 204.1m/s while, the outlet boundary condition is set as the pressure outlet condition, with outlet pressure of 1 atm. The losses are found to be minimal in the ‘duct 5’ with least transverse flow. This is due to the efficient area distribution which result in initial acceleration and completion of diffusion much before the exit plane causing suppression of vortex at the bend. This in turn helps the ‘duct 5’ to retain its flow energy along the centerline direction resulting in better pressure recovery.