Effect of swirl flow on spray and combustion characteristics with heavy fuel oil under two-stroke marine engine relevant conditions

To investigate the influence of the swirl flow and oxygen concentration on spray, combustion and emissions under marine engine relevant conditions with heavy fuel oil (HFO), a three-dimensional simulation systematically is carried out. The physical properties of HFO are implemented to present work. Experimental data from three different constant volume combustion chambers are employed to qualitatively validate the present models based on the spray penetration length, heat release rate and flame configuration. The effects of the swirl flow and oxygen concentration on spray, combustion and emissions are further investigated. For a non-reacting simulation, it is found that the swirl flow has a contrary effect on the liquid penetration and spray configuration at small and large angles. For combustion simulations, very good agreement with the experimental results is obtained for the heat release rate using the present models. The results show that the swirl flow causes a change in the flame configuration. In addition, strong liquid-gas interactions due to the anti-swirl flow leads to less soot and more NOx emissions. By contrast, reducing oxygen the concentration could reduce the combustion temperature and make the flame move towards a premixed combustion regime. Local unburnt gas is observed at a low oxygen concentration with the swirl flow.