Study On The Key Parameters And Generic Rules Of Original Emission For Premixed Gasoline Engines

Since emissions are an important part of the research on engine performance, studying on the generic rules of engine emissions is of great significance for the conceptual design and calibration of engine forward development and engine bench calibration,which can provide the target for positive development of similar engine and for the backward development of evaluation system.This paper investigates the key parameters and generic rules of original emission for premixed gasoline engines, trying to establish the internal relation between the premixed gasoline engine emissions and model design an d operation parameters. Based on a single cylinder gasoline engine combustion test data, the emission test data and operation parameters, and compared with test data of three sets of advanced straight engine, generic rules of original emission for premixed gasoline engines was studied.First of all, theoretically, on one hand, the formation process of mixture premixed combustion engine and engine emission of CO, HC and NO X formation mechanism was explored; on the other hand, the main emission inspection met hods of deficiencies were researched.Second, the relevant tests were conducted. The first step was to study systematically on the basis of a single cylinder premixed combustion machine. In order to understand the impact of single control parameters on emi ssions, only a control parameter was changed for each test so as to achieve the objective. The second step, universal characteristic test was conducted on the three advanced turbo jet of multi-cylinder machine, during the process several different control parameters were changed every time, and the data was recorded.Finally, the experiment data was processed. Based on the single-cylinder engine test data, and combined with the change of multi-cylinder machine parameters, three engine emissions were summarized to analyze multi-cylinder machine emissions rules. single cylinder gasoline engine results showed that when EGR rate is low, tumble ratio has a greater influence on the NO_X emission and the largerest decreased can attain 20%; as the EGR rate is increasing, tumble ratio on the NO_X emission is decreasing gradually. When the ignition advance angle change, HC emissions and the exhaust temperature are into inverse proportion; Tumble ratio has a greater influence on HC as the ignition advance angle is small and on NO_X as the ignition advance angle is bigger; However, When the excess air coefficient is between 1.0~1.6, tumble ratio has less influence on HC and CO, but at the low range of the excess air coefficient, the influence of tumble ratio on the NO_X emission is larger, which can reach 40%. The multi-cylinder machine results showed that the oxygen concentration in cylinder change can be caused to influence parameters on the CO emissions, for example, excess air coefficient, RGF, however, excess air coeffici ent has the greatest influence on CO emissions. Excess air coefficient, pressure in cylinder and exhaust temperature, inlet temperature, rotating speed and so on can influence the HC emissions, but compared to other factors, excess air coefficient has the obvious impact on CO emissions. According to the degree of influence, the main factors influencing the NO_X emission are EGR, BMEP, excess air coefficient.