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ABSTRACT
Multi-injection is an effective strategy to control the NOx emission while maintaining the performance of combustion engines, however, it is difficult to balance emission and performance in practical operations. In this study, the Response Surface Methodology (RSM) was proposed to optimize them simultaneously. The combustion and performance of engine were firstly characterized by varying the multi-injection parameters, including fuel quantity distribution, injection dwell time and injection pressure. Experiments were conducted on a 3.856 L diesel engine, through which the cylinder pressure, torque output, and main emissions were measured, with brake specific fuel consumption (BSFC) and effective thermal efficiency (ηet) being analyzed. The experimental results showed that the fuel injection properties had a significant impact on in-cylinder combustion and emissions. Based on the RSM analysis, the coupling effects between engine performance and NOx emission were then optimized, which were then verified and tested by experimental measurements. The optimal results were obtained when the fuel share ratio, dwell time, and injection pressure were 5, 10.56 °CA and 95 MPa, respectively. Through the verification tests, NOx emission could substantially reduce as much as 31.8% with torque slightly reduced by 3.3%.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (No. 51976135, No. 21961122007, and No. 51806148). The authors also thank the support of high-tech Ship Research Program of MIIT (MC-201501-D01-01).