Effect of Exhaust Gas Recirculation Combined with Selective Catalytic Reduction on NO x Emission Characteristics and Their Matching Optimization of a Heavy-Duty Diesel Engine

Diming Lou; Lulu Kang; Yunhua Zhang; Liang Fang; Chagen Luo

doi:10.1021/acsomega.2c01123

Effect of Exhaust Gas Recirculation Combined with Selective Catalytic Reduction on NO _x Emission Characteristics and Their Matching Optimization of a Heavy-Duty Diesel Engine

ACS Omega. 2022 Jun 22;7(26):22291-22302. doi: 10.1021/acsomega.2c01123. eCollection 2022 Jul 5.

Authors

Diming Lou¹, Lulu Kang¹, Yunhua Zhang¹, Liang Fang¹, Chagen Luo²

Affiliations

¹ School of Automotive Studies, Tongji University, Shanghai 201804, China.
² Nanchang Automotive Institute of Intelligence and New Energy, Tongji University, Nanchang 330052, China.

Abstract

Exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) have become important technologies to reduce the NO _x emission of heavy-duty diesel engines and meet the increasingly stringent emission regulations. This paper studied the effect of EGR combined with SCR on the NO _x emission characteristics of a heavy-duty diesel engine based on the engine bench test. The results showed that the NO reduction rate of EGR-coupled SCR increased with the increase of engine load, and the effect was no longer significant when the NO reduction rate exceeded a certain limit under the same working conditions. EGR combined with SCR has little effect on NO₂ emission reduction, and the increase of engine speed can significantly improve the efficiency of the NO₂ reduction rate at 75 and 100% load. 25% opening of the EGR valve (OEV) and 50% OEV have very similar effects on the NO _x reduction rate when the engine speed is at a low level. Compared with low engine speeds, increased OEV or ammonia NO _x molar ratio (ANR) had a more obvious effect on the NO _x reduction rate at high engine speeds. SCR combined with low valve-opening EGR had a more significant effect on the NO _x reduction rate. The increase of OEV led to the increase of fuel consumption rate, but the effect on the fuel consumption rate decreased gradually with the increase of diesel engine speed. Meanwhile, this study optimized the matching relationship between OEV and ANR based on the data of the genetic algorithm, which provides a theoretical research method and application basis for diesel engine-matching of EGR and SCR.