Visualization study on the flame propagation and distribution characteristics and exploration of optimal injection strategy in ammonia/diesel dual direct injection mode

With the increasing shortage of fossil fuels and the worsening carbon emission problems, ammonia has been attracted widely to alleviate the current challenges faced by internal combustion engines. Igniting direct injection of liquid ammonia by diesel may be a measure to achieve effective ammonia application, while the research on the characteristics of combustion and the unburned ammonia emission is little. Therefore, this paper studies the effects of ambient parameters and injection parameters on the characteristics of diesel ignition and flame propagation and distribution based on a constant volume combustion chamber, through the shadow method. The results indicate that the premise to ensure that ammonia can fully participate in combustion is that the flame can backpropagate to the junction of the two sprays. The current optimal injection strategy is the simultaneous injection of diesel and ammonia combined with a complete ammonia injection before the maintained flame. At a low temperature and high diesel injection pressure, ammonia will participate in combustion after a delay, which may result in a relatively low heat release rate and high unburned ammonia emissions. Overall, the paper can provide important references for professional researchers which is of great significance for the development of diesel/ammonia engines.