CFD simulations on the compressor of a mini-jet engine- II

Abstract

With the fast paced development of Unmanned Aerial Vehicles (UAV) in recent years, there is a great demand for propulsion systems that can enhance endurance and range capabilities of UAVs. Efforts have thus been made to miniaturise turbojet engines for UAV applications. This project aims to establish a Computational Fluid Dynamics (CFD) simulation framework for the SR-30 mini jet engine compressor to better understand the flow within a miniaturised centrifugal compressor. Unsteady flow simulation with the sliding mesh model will be conducted in FLUENT. Initial boundary conditions were set according to data gathered from steady stimulations conducted in AxCent Pushbutton CFD. In order to save computational time, the mesh size was kept below 500,000 cells and the Spalart-Allmaras turbulence model was used with first order transient solution. Results showed flow separation for simulations at 80000rpm and lower pressure ratio values compared to steady simulation. Choked flow may be occurring as there are regions in the compressor where flow speeds are faster than sonic conditions. The pressure ratio increases with lower mass flow rates due to lower pressure losses. Flow interaction between the impeller and diffuser blades will also be analysed. Next, simulations were conducted with a constant mass flow rate of 0.16kg/s and varying speeds of 60000rpm, 70000rpm and 80000rpm. Results show that an increase in the compressor speed will improve the performance of the compressor. Lastly, further simulations were conducted at the speed of 50000 rpm and results showed that at a lower speed, the compressor is more efficient at lower mass flow rates.