Simulation Of Combustion And Emission Characteristics Of Marine Four-Stroke Ammonia Engine Ignited By Hydrogen In Prechamber

To continuously promote the green and low-carbon development of the shipping industry is an important measure for China to implement the"carbon peaking and carbon neutrality"strategy and participate in the action to control global warming.In order to effectively control the greenhouse gas emissions of shipping industry and achieve the goal of decarbonization of the international community,the use of zero-carbon ammonia fuel is undoubtedly the best choice under the current technological conditions.In this paper,Marine large-diameter precombustion chamber natural gas engine as the research object,through the establishment of simulation model,simulation calculation.Based on the energy conservation in the input cylinder,the effects of three hydrogen mixing ratios on combustion and emission characteristics of the engine under different loads were studied.On this basis,the excess air coefficient and ignition timing are optimized to achieve the best performance of the engine.The main research contents and conclusions of this paper are as follows:（1）One-dimensional and three-dimensional simulation models of marine large-bore four-stroke active pre-chamber natural gas engine were constructed,and the four load conditions（100%,75%,50%and 25%）of the model were verified based on relevant experimental data.Based on the energy conservation in the input cylinder,the performance of the ammonia-hydrogen hybrid fuel engine under different loads was calculated.The effects of hydrogen blending ratio（0%,10%and 15%）in three main combustion chambers on the performance of ammonia fuel engines were studied.The results indicate that the emission of unburned ammonia and N₂O are correlated;The thermal denitration in the cylinder can effectively reduce the emission of NO_X,and the NO_X emission are in a trade-off relationship with N₂O and NH₃;（2）On the basis of 100%load,The engine performance is optimized from ignition timing and excess air ratio,and an optimization approach using high ammonia for substitution is proposed.The results indicate that,compared to natural gas,the use of ammonia fuel reduces the GWI of emissions,also have good thermal efficiency proving the feasibility of using ammonia fuel in four-stroke internal combustion engines with prechamber.（3）The reaction parameters of the combustion reaction mechanism of Li-Konnov were optimized.The results show that the optimized mechanism fits the ignition delay time experimental data better.Compared with before optimization,the optimized mechanism has a high analog value for NOx emissions,while the analog values of unburned NH₃ and N₂O emissions are slightly lower,but the error is within 15%,which provides a reference for future mechanism optimization.This paper mainly analyzes the technical approach and optimization scheme of using ammonia fuel in large cylinder diameter precombustion chamber engine.The research results can provide theoretical basis for the design and optimization of enhanced combustion system of medium and high speed Marine ammonia engine.