Effect of primary water injection angle on thermal propulsion performance of a water ramjet engine

Using high-performance hydroreactive metals as fuels, water ramjet engines (WREs) are regarded as the most competitive underwater power systems to meet high-speed and long voyage propulsion. However, its performances are strongly influenced by the water injection mode. Therefore, in this paper, the flow and thermal propulsion characteristics of WREs with different primary water injections were numerically investigated based on validated model. Firstly, the internal flow characteristics illustrated by streamlines, kinetic rate of the reaction and distribution of the components are discussed. It is found that there is a longitudinal vortex caused by sudden-expansion formed by annular inlet that can intensify mixing. Then, the effect of water injection angles on propulsion performance is investigated by considering six axial angles and two tangential angles. Results indicate that proper inclination of the primary water nozzles to the upstream makes the mixing occur earlier. Correspondingly, the specific impulse can be enhanced by approximately 8%. With the increase of tangential angle, more water congregates near wall, leading to incomplete reaction and the reduction of specific impulse. This paper is beneficial for the design of WRE water injection.