Numerical Study On The Influence Of Oil And Gas Parameters On The Performance Of Marine Low-speed Diesel Engines

Due to the increasing depletion of fossil energy and the increasingly stringent emission regulations,"energy saving and emission reduction" is an important topic for today’s diesel engine research scholars.The combustion process of a diesel engine has an important impact on its economy,emissions,and stability.It specifically involves complex processes such as in-cylinder airflow organization,fuel injection,complex chemical reactions,flame propagation,and heat exchange.These processes are mainly affected by the conditions of intake and exhaust and fuel injection.Based on the key data obtained from the experimental platform,this paper uses numerical simulation methods to deeply understand the influence of fuel injection and intake conditions on combustion and emissions,so as to improve the quality of oil and gas mixture,and then optimize the diesel engine combustion system.This paper takes a marine low-speed two-stroke diesel engine as the research object,and uses CFD simulation software Fluent to numerically simulate the cycle process of fuel injection,combustion,exhaust,and scavenging in the cylinder of the diesel engine.The average pressure in the cylinder,the temperature curve,and the indicated power obtained by the simulation calculation are compared with the experimental data,and the results are found to be more consistent.Based on the validity of the physical model,a single-parameter and multi-parameter matching scheme was designed,and the influence of the scavenging parameters and injection parameters of the diesel engine on the gas flow and subsequent combustion and emissions in the cylinder was studied.Among them,the scavenging parameters include the scavenging radial inclination,and the injection parameters include the injection direction and the number of injection holes.It is found that too small scavenging angle will increase the gas collision loss in the cylinder,but the scavenging performance and the cooling effect in the cylinder will be correspondingly improved.At the same time,the turbulent gas flow in the cylinder will also cause intense combustion in the next cycle of the cylinder.Partial wall temperature is too high;excessive scavenging inclination will cause more residual exhaust gas in the center of the cylinder,poor scavenging performance,which is not conducive to combustion.Under the premise that the flow area of the nozzle holes is constant,the number of nozzle holes is small,the spray penetration distance is longer,and the wall collision phenomenon is prone to occur;the increase in the number of nozzle holes can promote the improvement of the quality of oil and gas mixing to a certain extent,but The overlap effect of the increased,but will reduce the quality of combustion.The study of the radial injection angle of the single-hole injector found that the reverse swirl injection and the radial injection angle are too small,which will cause the fuel to be resisted by the swirl field in the cylinder,and then accumulate in the center of the cylinder,resulting in insufficient combustion;In swirl injection,the radial injection angle is too large,which will cause fuel to accumulate near the cylinder wall,which is also not conducive to combustion.Finally,on the basis of the research of scavenging parameters and fuel injection parameters,parameter matching was carried out to improve the overall performance of the diesel engine.It is found that when the scavenging angle is 11.5° and the radial injection angle is 20.1°,the power performance of the original model is improved by 16.1%,the economy is improved by 14.8%,and the NO emission is increased by 1.4%.