The Research of Diesel Engine Assembly Consistency Influence NOx Emission Based on Uniform Design Method

Diesel engines need to meet the higher emission requirement according to the Euro VI emission standards, and changes in the assembly tolerance of diesel engines will affect the consistency of nitrogen oxides(NOx) emissions. To study the influence of assembly tolerance on NOx emission, a heavy diesel engine was used as the research prototype. The combustion model of the diesel engine was simulated by the Converge software and calibrated with the bench test data. Because the combustion system parameters have a significant impact on emissions, a three-factor eleven-level uniform design is arranged with three parameters, including compression ratio, fuel injection nozzle extension height and injection advance angle. The regression analysis method is used to obtain the relationship between the parameters and NOx emissions. The R2 test value of the regression equation is 0.916 and the F test value is 43.5, which shows that the results of the analysis are very effective. Then the single factor test method is applied to analyze the varying laws of compression ratio, nozzle extension height and fuel injection advance angle on NOx emissions, and the results reveal the inherent law similar to the regression equation. According to the Euro VI emission standards and the law of diesel engine emission performance consistency, the tolerance variation range of the key dimensions of the assembly parameters is obtained.