| The close coordination between the air flow in the cylinder of the diesel engine and the fuel injection determines the combustion quality in the cylinder.The airflow movement pattern organized by the diesel engine intake directly affects the mixing of fuel and air,and also has a greater impact on the flame propagation rate.In this paper,the YN33 single spiral inlet diesel engine is taken as the research object,and the oil flow method is used to visualize the steady flow test;through the combination of test and simulation,the evolution process of the in-cylinder flow field of the inta ke and compression stroke is analyzed.Based on the analysis of the evolution process of the flow field in the cylinder,the orthogonal design of the DC section of the spiral inlet port is emphasized to achieve the improvement of the swirl ratio and the flow coefficient.On this basis,the gas stratification in the intake zone is also explored.The main work completed is as follows:The analysis of the evolution process of the flow field in the diesel engine cylinder based on the visualized steady flow tes t shows that the tracer oil flow formula of methyl silicone oil,oleic acid and aluminum powder with a mass ratio of 8:8:3 can be displayed more clearly and completely.Information on the flow field near the wall in the cylinder.In the intake process,as the valve opening increases,the in-cylinder swirl ratio gradually increases.Through the analysis of the evolution history of the flow field intensity in the cylinder,it can be seen that the change of the flow field intensity in the intake stroke is main ly dominated by the intake air flow,and the change of the flow field intensity in the compression stroke is mainly dominated by the movement of the piston.In the initial stage of the gas in the cylinder entering the ω combustion chamber,the vortex radius is reduced and the vortex ratio is strengthened.During the compression process,the piston runs to near top dead center,and most of the tumble flow is crushed.A study on the performance of the air passage in the design of the DC section of the spiral airway was carried out,and the results showed that the three structural parameters of the upper declination angle,the lower declination angle and the length of the DC section of the spiral air inlet were changed at the same time,and their values were 82 ° At 85° and 69 mm,the maximum swirl ratio in the cylinder is 4.146,and the intake air volume is 1.593 g.The swirl ratio and the intake air volume are increased by 26.02% and 5.50% respectively compared to the original machine.Carried out a study on the characteristics of combustion and emissions in the cylinder by different airway schemes.The results show that: Scheme 9(in-cylinder pressure,combustion heat release rate)> original machine(in-cylinder pressure,combustion heat release rate).Scheme 9 i mproves the combustion quality,and the peak temperature and cumulative heat release increase by 75 K and 178 J,respectively.Scheme 1 deteriorates the combustion quality,and the peak temperature and cumulative heat release decrease by 73 K and 155 J,respectively.Carried out a study on the stratification of the in-cylinder charge by the key structural parameters of the spiral air passage.The results show that: the air intake from the lower right section of the spiral air passage enters the cylinder is the most,accounting for 27.3%;the air intake of the upper left section At least,accounting for 22.4%.Matching the structural parameters of the spiral air passage,when the intake port is deflected by 15°,the gas entering the cylinder from the upper left s ide of the intake section of the spiral air passage can form the largest difference in intake concentration gradient. |
