Experimental and Numerical Studies on Lobed Ejector Exhaust System for Micro Turbojet Engine

Abstract

:For the purpose of improving thrust and cooling the wall of the nozzle on a micro turbojet engine, the aerodynamic characteristics micro lobed ejector, which consists of a lobed nozzle and mixing, is studied using numerical calculations and experiments. Firstly, the aerodynamic performances of several lobed nozzle jectors with different geometries were calculated based on the Reynolds-averaged Navier-Stokes equations with k -ε turbulence model. The numerical results show that the pumping ratio is enhanced with the increase of lobe expansion angle in the range of 5 to 17 degrees. Firstly, the thrust gain increases and then decreases with the increase of lobe expansion angle. Secondly, taking into account of the aerodynamic performances and weight penalty, the thrust and the wall temperature of the nozzle of a micro turbojet engine with a lobed ejector of 5-degree expansion angle was measured. Experimental data demonstrate that the lobed ejector increases the thrust of the engine by 2.99% relative to the convergent nozzle. Moreover, the peak temperature of nozzle wall is decreased by 30%. At the same time, the pumping air mixed with the exhaust plume decreases the temperature of the plume. It is believed that the lobed ejector has another advantage of reducing the infrared radiation of the micro turbojet engine.