Experimental Study On Oil Dilution Of TGDI Engine Based On Different Gasoline

Oil dilution is a common problem in TGDI engines.Crankcase ventilation,fuel injection strategies and fuel types have huge impact on it.Oil dilution can cause oil viscosity downgrade,so the friction pair can be seriously damaged by this.The HC mixture out from crankcase can be beyond the calibration range,when it comes to the combustor again,it will result in an air-fuel ratio thicker and make the particle emissions increase.At the same time,oil dilution is also likely to increase the frequency of low speed pre-ignition.Therefore,effectively controls of oil dilution have great significance for the further development of TGDI engine.In this paper,a TGDI engine which has a large degree of oil dilution in durability test is selected to carry out the verification test.It is found that different fuel conditions,operating conditions and engine oil temperatures have great influence on engine oil dilution.Different operating conditions have different degrees of contribution to oil dilution,at the same speed or the same load,the greater the fuel consumption,the more obvious the oil dilution will be,not only in the course of starting engine or warming engine.The experiment also verified the influence of different oil temperature on oil dilution in the same operating condition,that is,low oil temperature and low oil dilution rate,low temperature and high oil dilution rate.This can also explain why the TGDI vehicle oil volume gradually increases under the condition of low speed or low ambient temperature.It is found that the special fuel with low T90 temperature can play a good role in inhibiting oil dilution,meanwhile the engine fuel consumption decrease and dynamic performance improve significantly.By comparing characteristics of 92# and 95# gasoline,it is found that other distillation temperatures can also affect oil dilution.In general,the greater the fuel density,the more obvious the oil dilution will be.The test shows that under the condition of certain operating conditions and oil temperature,the change rule of oil dilution is rising rapidly,slowing down and then becoming stable.Through the oil collection test of the crankcase ventilation system,it is proved that oil dilution is reversible.In this paper,Roasting and weighing oil sample to compute dilution rate is introduced.The test data shows that the method can effectively detect the oil dilution rate,and the reproducibility is good,and it can meet the requirements of the engineering application.During the test,the shortage of warming operating condition and the oil flashing process were discovered,which needs further improvement in the future experiments.In the follow-up study,author hope to use the neural network algorithm to make fuzzy correspondence between the oil temperature and the key parameters,such as the fuel injection,air fuel ratio,and the temperature of the fuel oil,to simulate the algorithm to guide the oil monitoring and maintenance in the related experiments.