Research On Combustion Performance Of Ammonia/Diesel Dual Fuel Engine Under Low And Medium Load

Ammonia,as a green carrier without hydrocarbon energy,can be produced through renewable energy sources and has bright prospects in clean energy applications in internal combustion engines.However,ammonia has the characteristics of high self ignition temperature,narrow flammability limit,and slow flame propagation speed.Therefore,ammonia requires traditional fuel for ignition in internal combustion engines.Diesel fuel as the ignition fuel can provide excellent performance for engines,but the combustion in the cylinder of ammonia/diesel engines is poor,There is a large amount of unburned ammonia in the combustion products,which has the problem of low ammonia utilization rate and poor engine power output.To optimize the combustion in the cylinder of ammonia/diesel engines with high ammonia substitution rate and improve combustion efficiency.This article reserach the key parameters of engine operation(ammonia substitution rate,compression ratio),as well as the impact of pilot fuel injection strategy(injection timing,injection angle,multiple injections)on the combustion process and efficiency of the engine.This study takes improving the combustion efficiency of ammonia/diesel engines as the starting point,selects small and medium-sized load conditions with poor combustion in the engine cylinder,and uses three-dimensional numerical simulation method for research.The study reserach the impact of ammonia substitution rate on combustion changes,combustion efficiency,and carbon reduction ability in the cylinder under medium and small loads.The impact of compression ratio on combustion efficiency and combustion process were analyzed.The injection timing and injection angle of pilot oil under small and medium-sized loads to improve combustion performance,and explored the impact of multiple injection of pilot oil and multiple injection under different compression ratios on combustion performance were analyzed.The main work and conclusions are as follows:Firstly,a three-dimensional engine model is established using numerical simulation software to verify the mesh sensitivity and effectiveness of the model.The combustion process and combustion efficiency in the cylinder were analyzed under different ammonia substitution rates and compression ratios under medium and low load conditions.When the ammonia substitution rate increases,the ignition delay increases,the combustion efficiency deteriorates,and the engine IMEP decreases.By increasing the compression ratio,the combustion efficiency in the cylinder reaches 82% at a medium load 50% ammonia substitution rate,while the combustion efficiency in the cylinder reaches 78% at a 60% ammonia substitution rate.Compared to a small compression ratio,it increases by 10%,and the engine IMEP is closer to pure diesel operation.Secondly,analyze the impact of a single injection of pilot oil on the combustion performance of the engine.The advance of fuel injection timing causes a change in the combustion mode in the cylinder,and diesel plays a role in both ignition and combustion support,accelerating the flame propagation speed in the cylinder.Under medium load,early injection of diesel fuel results in a combustion efficiency of 98% at a 50% ammonia substitution rate,and a combustion efficiency of 78% at low load.The improvement in combustion is limited at a 70% ammonia substitution rate.The optimization study focuses on the 50% ammonia substitution rate of the injection angle.Reducing the injection angle can improve the combustion in the cylinder.When the injection angle is 60 °,the combustion efficiency increases by 6% for medium load and 5% for small load.Finally,analyze the impact of multiple injections of pilot oil and different compression ratios on engine combustion performance.Multiple injection of diesel combines early and late injection,achieving a combustion efficiency of 98% at medium load and 74% at low load with a 50% ammonia replacement rate.The engine IMEP is close to pure diesel mode.Multiple injections under high compression ratio result in good combustion efficiency of the engine at a high ammonia substitution rate,which is equivalent to IMEP operating with pure diesel.At medium load,the engine has good combustion performance at a 60% ammonia substitution rate;At low loads,the engine has good combustion performance at a 50% ammonia substitution rate...