Effect of EGR and Fuel Injection Strategies on the Heavy-Duty Diesel Engine Emission Performance under Transient Operation

Fangyuan Zhang,Linlin Li,Kunyi He,Zhongshu Wang,Kaibo Yu,Jing Tian

doi:10.3390/en13030566

Fangyuan Zhang, Linlin Li + Show 4 more

Open Access

https://doi.org/10.3390/en13030566

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Journal: Energies	Publication Date: Jan 24, 2020
Citations: 10	License type: CC BY 4.0

Affiliation: Jilin University, SAIC Motor (China)

Abstract

To reduce the smoke and nitrogen oxide (NOx) emissions; a detailed study concerned with exhaust gas recirculation (EGR) and diesel injection strategy was conducted on a two-stage series turbocharging diesel engine under transient operating condition. One transient process based on the constant speed of 1650 r/min and load increases linearly from 10% to 100% within 5 s was tested in this study. The effect of the EGR valve control strategy on engine transient performance was examined. The results show that better air-fuel mixing quality can be obtained with the optimized the EGR valve open loop control strategy and the smoke opacity peak decreased more than 64%. Under the EGR valve close loop control strategy; the smoke opacity peak was lower than with open loop control strategy; but higher than without EGR. The effect of fuel injection strategy on engine transient performance was examined with the EGR valve close loop control. The results show that sectional-stage rail pressure (SSRP) strategy (increasing injection pressure from a turning point load to 100% load) and optimizing fuel injection timing can improve the engine emission performance. The satisfactory results can be obtained with lower NOx (382 ppm) emissions and the smoke opacity peak (3.8%), when the turning point load is set to 60% with the injection timing delay 6° CA.

Highlights

Diesel vehicles operate in transient conditions in most cases
Studies have shown that due to the air delay in two-stage series turbocharging diesel, the constant opening of the exhaust gas recirculation (EGR) valve leads to overshooting of the EGR rate in the middle and late stages of the transition process [34]
We considered the strategy of opening the EGR valve at the first stage during the transition and closing the EGR valve at the middle stage

Summary

Introduction

The transient feature is the delay of boundary condition response compared to steady state [1,2,3,4], which leads to deterioration of fuel economy and pollutant emission [5,6,7,8]. The reduction of oxygen concentration caused by air intake delay decreases the nitrogen oxide (NOx) emission. The lack of oxygen leads to an increase of the goal equivalence ratio which causes a poor smoke emission [9,10,11,12,13]. Glewen et al [15] found the main reason of deviation between transient performance and steady performance in light-duty diesel engine is the in-cylinder temperature of intake valve close timing and the extra oxygen concentration in exhaust gas recirculation (EGR)

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