Study on the effect of the nozzle diameter and swirl ratio on the combustion process for an opposed-piston two-stroke diesel engine

There are great differences between combustion in the opposed-piston two-stroke diesel engine and conventional diesel engine, because of the different injection position and the relative position between the spary and the in cylinder flow. In this paper, CFD models base on AVL-FIRE were established. Effects of the nozzle diameter and swirl ratio on the engine combustion were calculated and studied, and matching criteria of nozzle diameter and swirl ratio were summarized. The results show that,the smaller nozzle diameters means the smaller droplet diameters after collapse; Moreover, a proper swirl ratio can improve the mixing process, but if it is too large, droplets are likely to diverge and then accumulate in a restricted region, resulting in the form of rich mixture regions. The best nozzle diameter is 0.1mm while the best swirl ratio is 1.0.