Research On The Influence Of Injection Strategy On Combustion And Emission Of Heavy-duty Diesel Engine And Oxygenated Fuel In The Highland Environment

With the promotion of China's western development policy,economic in the plateau developed rapidly,the demand for heavy-duty diesel engine is increasing.The working conditions of heavy-duty diesel engines in plateau conditions directly affect the process of the development of the western part of China.Low temperature and oxygen-deprived environments in the plateau lead to a decline in the power performance and a deterioration in emission performance.In order to improve the working performance of a heavy-duty diesel,in this paper,a spray combustion model of a plateau diesel engine based on AVL Fire was developed to study the effects of multiple injection strategies and oxygenated fuel on the combustion and emission performance of a plateau diesel engine.The main tasks and conclusions are as follows:1.Geometric model of the combustion chamber of the diesel engine was established based on the basic parameters.And we determined the mathematical model,initial conditions and boundary conditions used in the calculation.Then the in-cylinder combustion conditions of the diesel engine under plain condition were simulated,and results of the calculations were compared with the test results to verify the accuracy and validity of the established model.2.The in-cylinder combustion conditions were simulated for the diesel engine under 4300 m plateau conditions with different injection timing conditions.The results showed that with the advance of the injection timing,the in-cylinder pressure and temperature of the diesel engine increased significantly,the area of the indicator diagram increased about 8.9%,the dynamics were restored significantly,and the carbon fume emissions were reduced,but accompanied by an increase in NOx emissions.3.The combustion conditions in the cylinder of this diesel engine were simulated under plateau conditions using the pre-main injection strategies.The effects of pre-main injection interval,pre-injection fuel amount on diesel engine combustion and emission performance were investigated.The following conclusions were researched: when using pre-main injection strategy,the diesel engine in-cylinder pressure and temperature curve is fuller and the peak increase and the combustion conditions in the cylinder was better than which using single injection strategy.Smaller pre-main injection interval and fuel amount reduced both NOx and soot emissions,NOx emissions can be reduced by an average of 56% and soot emissions by an average of 67% compared with single injection.4.The combustion conditions in the cylinder of the diesel engine were simulated under plateau conditions using the main-post injection strategies The results show that when using the main-post injection strategy,the in-cylinder pressure and temperature were slightly reduced.The main-post interval has only a little effect on NOx emissions,the soot emissions increased with the increase in the main-post interval.When the post-injection fuel amount increased,NOx emissions decreased firstly then increased and the soot emissions decreased slightly.Compared with single injection,NOx emissions can be reduced up to 15% and soot emissions can be reduced up to 64%.5.When using pre-main-post injection strategy,in-cylinder trends are essentially the same as when pre-main-injection strategy and main-post injection strategy were used separately,pre-injection and post-injection parameters were independent.So it can be seen as a direct overlay of the pre-main injection and main-post injection strategy.6.Simulations were performed to calculate the combustion of the diesel engine under plateau conditions with different blending ratios of oxygenated fuel,the in-cylinder combustion and emission conditions and the distribution of related products were analyzed.As the results showed,when the diesel engine burned oxygenated fuels,the in-cylinder combustion condition was better,the peak of in-cylinder pressure and temperature increased.The in-cylinder oxygen consumed more rapidly when burning oxygenated fuels.As combustion proceeds,diesel has least amount of oxygen remaining in the cylinder when oxygenated fuel has most.The soot emission decreased with the NOx emission increased.As the blending ratio of n-butanol in oxygenated fuels increased,in-cylinder combustion condition improved further and NOx emission decreased.7.B70N30 was selected to study the effect of multiple injection strategy on the combustion and emission performance of oxygenated fuel.For oxygenated fuels,the impact of multiple injection strategy was mainly in terms of emission performance,with a less impact on dynamics.The smaller the pre-main injection and pre-injection fuel amount,the lower the NOx and soot emissions of the diesel engine.When the main-post inject interval increased,the soot emission increased gradually,so we should choose the smallest main-post interval.The more post-injection fuel injected,NOx emission increased,soot emission increased and then decreased.