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

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.

Study on the Effect of Exhaust Gas Recirculation Coupled Variable Geometry Turbocharger and Fuel Quantity Control on Transient Performance of Turbocharged Diesel Engine

“…The results show that the best compromise emission can be obtained by closing the EGR valve at 1.5 s and opening it at 4 s through open-loop control. When the exhaust oxygen concentration is controlled as a closed-loop target, although the EGR opening curve similar to the open-loop control obtained, the emission will deteriorate due to the delay of closed-loop control [23].…”

Study on the Effects of Exhaust Gas Recirculation and Fuel Injection Strategy on Transient Process Performance of Diesel Engines

“…The EGR rate in the study is calculated by measuring the volumetric fraction of CO 2 in the intake and exhaust gases using the Cambustion NDIR500. The calculation method is presented in Equation (5) [22]:…”

“…Pennington et al [21] studied the torque increase transient process lasting from 2 to 10 s. By reducing the variable geometry turbocharger (VGT) opening and EGR valve opening, they minimized turbocharger lag, resulting in reduced fuel consumption and particulate matter emissions. Zhang et al [22] studied a 5 s transient process on a two-stage turbocharged diesel engine. They found that closing the EGR valve at 1.5 s and reopening it at 4 s through open-loop control achieved optimal compromise emissions.…”