Abstract
The assembly consistency of a diesel engine will affect its nitrogen oxides (NOx) emission variation. In order to improve the NOx emissions of diesel engines, a study was carried out based on the assembly tolerance variation of the diesel engine’s combustion system. Firstly, a diesel engine which meets the Euro VI standards together with the experimental data is obtained. The mesh model and combustion model of the engine combustion system are built in the Converge software (version 2.4, Tecplot, Bellevue, DC, USA), and the experimental data is used to calibrate the combustion model obtained in the Converge software. Then, the four-factor and three-level orthogonal simulation experiments are carried out on the dimension parameters that include nozzle extension height, throat diameter, shrinkage diameter and combustion chamber depth. Through mathematical analysis on the experimental data, the results show that the variation of nozzle extension height and combustion chamber depth have a strong influence on NOx emission results, and the variation of combustion chamber diameter also has a weak influence on NOx production. According to the regression model obtained from the analysis, there is a quadratic function relating the nozzle extension height and NOx emissions and the amount of NOx increases with increasing nozzle extension height. The relationship between emission performance and size parameters is complex. In the selected size range, the influence of the variation of the chamber diameter on NOx is linear. The variation of the chamber depth also has an effect on NOx production, and the simulation results vary with the change of assembly tolerance variation. Thus, in the engine assembly process, it is necessary to strictly control the nozzle extension height and combustion chamber depth. The research results are useful to improve the NOx emission of diesel engine and provide a basis for the control strategy of selective catalytic reduction (SCR) devices.
Highlights
Due to the high energy density and their wide range of power output, diesel engines are widely used in various fields such as agriculture, industry, engineering, transportation and so on.the widespread use of diesel engine causes serious environmental pollution
The results indicated that nitrogen oxides (NOx) emissions remained unchanged and the CO and soot emissions were reduced with a reasonable combustion chamber design
The results showed that this method could significantly reduce NOx emissions and improve engine performance
Summary
Due to the high energy density and their wide range of power output, diesel engines are widely used in various fields such as agriculture, industry, engineering, transportation and so on. Jesús Benajes [4] studied the effect of combustion chamber geometry on the reactivity of a high load reactivity-controlled compression ignition engine (RCCI). Liu et al [8], Khan et al [9] and Tay et al [10] used simulation software to optimize the performance of diesel engine under different fuel injection parameters and combustion chamber shape and obtained the optimal parameter combination under different loads. Orthogonal simulation experiments are used to study the influence of parameters, including nozzle extension height, throat diameter, shrinkage diameter and chamber depth, on the performance consistency of NOx emissions. The research results are useful to improve the NOx emission of diesel engine and provide a basis for the control strategy of selective catalytic reduction (SCR) devices
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