Design and numerical simulation of ejector nozzles for very small turbojet engines

Abstract

The examination of small turbojet engines for unmanned aviation systems is a main research activity at the Institute of Aeronautical Engineering at the Universität der Bundeswehr München. The special requirements for the design of these propulsion systems include compact installation size, high reliability and low acquisition costs. But the low overall efficiency, the high exhaust gas temperature and excessive noise emission limit the options for integration and mission profiles. The concept of the ejector nozzles offers a solution for further improving the propulsion system following the requirements. The secondary mass flow delivered from the ejector nozzle can not only reduce the exhaust gas temperature but also enhance the thrust. Ejector nozzles have been developed in combination with special mixer nozzles with the design goal of increasing the pumping performance and thrust augmentation. Both numerical and experimental investigations are conducted to study the mixing ability of the primary nozzle, the key to optimising the ejector performance.

Experimental Investigation of a Micro Turbojet Engine Chevrons Nozzle by Means of the Schlieren Technique

“…The specialized literature is quite poor in articles with experimental data that study the influence of the number, inclination to the nozzle axis and configuration of chevrons mounted on the exit edges of convergent nozzles for micro turbojets [9,14,39]. Although a large amount of literature has been written on subsonic and supersonic jets, there is still a visible lack of articles highlighting the structure and the dynamics of the hot subsonic jet using the Schlieren technique.…”

An Experimental Comparative Performance Study of Variable Area Ejectors in Different Operating Conditions

“…The bene ts of ejectors include their simple design, low cost, and ability to handle uids with high viscosity, high solids content, and high temperatures [9]. However, ejectors also have limitations, such as low and high noise levels [10].…”

Changes in Primary Nozzle Contours and Ejector Performance- A Numerical Study

“…Fatong et al, [17], demonstrated the dependence of ejector performance on the structural parameters of the mixing chamber. Schmidt and Hupfer [18] showed that the pumping capacity and jet pump thrust were a function of the nozzle design. An experiment by Khaled and Zine [19] investigated the effect of divergence and throat diameter on performance.…”