分层引燃高稀释低温燃烧汽油机多缸平衡控制研究

发布时间：2018-12-12 15:42

【摘要】：以SI-CAI混合燃烧为代表的汽油机高稀释低温燃烧其着火、燃烧过程对边界条件极其敏感,其在多缸机上的应用极易产生显著的缸间差异,进而限制了其工程应用。本文通过系统研究主要发动机运行控制参数对分层火焰引燃(SFI)燃烧多缸平衡控制的调控能力,并提出相应的控制策略,为低温燃烧多缸汽油机缸间不平衡问题的解决探索可工程实施的手段。本文首先搭建了基于Autobox控制和基于Labview数据采集的装有双VVT、外部EGR和PFI/GDI双喷射系统的高稀释低温燃烧四缸汽油机研究平台。在此基础上,系统研究了PFI/DI喷射控制策略结合点火策略对SFI燃烧的过程控制规律,探究直喷时刻、直喷比例和点火时刻等参数调控SFI燃烧的能力,确定上述参数用于调控缸间差异的潜力。结果表明:直喷时刻虽具备分缸控制能力,但其对燃烧的影响过于复杂,并不是分缸CA50控制的最佳选择。直喷比例的增大能够显著降低燃烧的最大压力升高率,但会对IMEP产生恶化,而对燃烧相位影响较小。相比均质混合燃烧,SFI燃烧拓宽了CA50控制窗口,提高了点火时刻对燃烧的可控性,有利于点火时刻对CA50的分缸控制。同时在保证经济性的提前下,SFI燃烧可以实现较好的燃烧稳定性和较低压力升高率水平。最后,基于PFI/GDI喷射控制和点火控制调控SFI燃烧过程的结果,提出了多缸IMEP和CA50平衡的控制策略。为了抑制多缸间IMEP差异,提出了PFI/GDI喷油比例和分缸Lambda的协同控制策略。发动机台架实验表明,在1500r/min3bar工况下,该策略将IMEP缸间循环变动从6.3%降低到了2.4%。为改善CA50的缸间差异,提出了分缸点火配合IVC、eEGR控制的CA50中位值平衡策略。发动机台架实验表明,在1500r/min-3.5bar工况下该策略可以在快速有效的实现CA50平衡的同时,防止点火控制作用的饱和。在1500r/min-4.7bar工况下,通过分缸CA50、IMEP联合平衡验证表明其可提高各缸燃烧稳定性,将缸间IMEP循环变动从6%减小到了4%。综上所述,对于采用PFI/GDI双喷射系统实现的SFI燃烧多缸发动机,通过喷油量、喷油比例、点火时刻,并配合双VVT、EGR,可以有效抑制由于对边界条件敏感所带来的多缸之间的IMEP和CA50差异,同时有利于改善发动机连续运转的稳定性。
[Abstract]:The ignition of gasoline engine with high dilution and low temperature, represented by SI-CAI hybrid combustion, is very sensitive to boundary conditions, and its application on multi-cylinder machine is easy to produce significant differences between cylinders, which limits its engineering application. This paper systematically studies the control ability of main engine operation control parameters on multi-cylinder balance control of stratified flame ignition (SFI) combustion, and puts forward the corresponding control strategy. In order to solve the problem of imbalance between cylinders of low temperature combustion multi-cylinder gasoline engine, an engineering method is explored. In this paper, the research platform of high dilution and low temperature combustion four-cylinder gasoline engine with double VVT, external EGR and PFI/GDI dual injection system based on Autobox control and Labview data acquisition is first built. On this basis, the PFI/DI injection control strategy combined with ignition strategy is studied systematically to control the process of SFI combustion, and the ability of direct injection time, direct injection ratio and ignition time to control SFI combustion is explored. Determine the potential of the above parameters to regulate the differences between cylinders. The results show that the effect of direct injection on combustion is too complicated and is not the best choice for CA50 control. The increase of direct injection ratio can significantly reduce the maximum pressure rise rate of combustion, but it will worsen the IMEP, but have little effect on the combustion phase. Compared with homogeneous mixed combustion, SFI combustion broadens the CA50 control window, improves the controllability of ignition time to the combustion, and is beneficial to the split cylinder control of CA50 at ignition time. At the same time, SFI combustion can achieve better combustion stability and lower pressure rise rate under the condition of economic advance. Finally, based on the results of PFI/GDI injection control and ignition control to control the SFI combustion process, a multi-cylinder IMEP and CA50 balance control strategy is proposed. In order to reduce the difference of IMEP between multiple cylinders, a cooperative control strategy of PFI/GDI injection ratio and cylinder separation Lambda is proposed. The engine bench test shows that the IMEP inter-cylinder cycle variation is reduced from 6.3% to 2.4% under 1500r/min3bar conditions. In order to improve the difference between cylinders of CA50, a neutral balance strategy of CA50 based on cylinder ignition and IVC,eEGR control is proposed. The engine bench test shows that the strategy can realize the CA50 balance quickly and effectively under the 1500r/min-3.5bar condition and prevent the ignition control from saturation at the same time. Under the condition of 1500r/min-4.7bar, the combined CA50,IMEP balance verification shows that it can improve the combustion stability of each cylinder and reduce the IMEP cycle variation between cylinders from 6% to 4%. To sum up, for the SFI combustion multi-cylinder engine realized by PFI/GDI dual injection system, the fuel injection rate, fuel injection ratio, ignition time, and double VVT,EGR, are used in the combustion of the multi-cylinder engine by means of fuel injection rate, fuel injection ratio, ignition time. The difference between IMEP and CA50 caused by sensitivity to boundary conditions can be effectively suppressed, and the stability of engine continuous operation can be improved at the same time.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK411

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