Matching Improvement Of Combustion Chamber And Spray Cone Angle And Exploring Of PCCI For Diesel Engine With Miller Cycle

In recent years,due to global energy crisis and environment pollutant,as energy consumption products which are widely used,the improvement of the economy and emissions for diesel engines is still a topic to be studied.To achieve this goal,the most fundamental way is to improve the combustion process and realize clean combustion.Intake parameters,combustion chamber shape and spray parameters are the three main factors during combustion process,which could affect mixture formation of diesel engines.The effective compression ratio could be changed by Miller cycle,so that the combustion temperature and pressure would be decreased,with the thermal efficiency improved simultaneously.In part load conditions,early injection and EGR could be used to realize premixed charge compression ignition,with emissions of NO_x and Soot reduced.In this paper,a 3D model is built within AVL-FIRE environment to calculate in-cylinder working process of a single cylinder diesel engine.After model validating,the Miller cycle,matching improvement of combustion chamber and spray cone angle,and Miller-PCCI combustion in part load conditions are calculated.Based on the validated model,the LIVC Miller cycle is realized with the constant intake mass flow and temperature through the turbocharged inter-cooled technology in rated load condition.It is found that Miller cycle could reduce fuel consumption by 4.73%in calculation period.And at the same time,the combustion temperature and pressure in cylinder are lower,so that emissions of NO_x and Soot could be reduced by 23.6%and 39.9%.Then based on the Miller cycle,six combustion chamber shapes and three spray cone angles are matched and optimized.For this diesel engine,the results show that large diameter straight combustion chamber with the spray cone angle of 130°,could reduce NO_x and Soot emissions by58.1%and 39.4%.Based on the improvement of combustion chamber and spray cone angle,influences of injection angle and cooled EGR on Miller-PCCI combustion mode in part load conditions are studied.The results show that the fuel injection advanced angle of 30°(CA)with 20%EGR rate could realize 0.95MPa IMEP,which is improved by 3.7%,for PCCI operating range.Meanwhile,fuel consumption is reduced by 3.6%,so the thermal efficiency is improved.The current results show about 17.6%NO_x reduction and 61.5%Soot reduction are achieved.The effect of PCCI has already been realized.