Abstract
A high pressure EGR system was adopted to a turbocharged inter-cooled diesel engine, to analyze its combustion and emission characteristics under the condition of different loads and constant speed. Under the same steady operating mode, with the increase of EGR rate, the temperature of compressed gas ascended, the ignition delay was shortened, the pressure and temperature of the burned gas descended, and the combustion process was prolonged. According to the experimental data, it was found that, at the same EGR rate, lower the load of engine was, lower the temperature in cylinder, and higher the increase rate of CO was. However, the increase rate of HC present a falling trend. The decrease rate of the specific emission of NOxlinearly varied with EGR rate with a slope of 1.651. The increase rate of smoke opacity behaved a second-order polynomial uprising trend, and the higher the load was, the sharpener the smoke opacity deteriorated, with the increase of EGR rate. From the point of emission view, the engine with EGR system can achieve the lesser exhaust emissions in some operations by adjusting the engine parameters.
Highlights
Saving oil resources and reducing the emissions of greenhouse gases have become the worldwide consensus when the earth is faced with the environment and energy sources challenges [1,2,3]
Among technical routes to implement the emission control, the exhaust gas recirculation (EGR) system is an external device used to control NOx emissions [7, 8], which has been regarded as an in-engine purification measure for reorganizing the intake and adjusting the in-cylinder combustion process [9]
Considering the cooling system of engine, the high pressure EGR method that the exhaust gas is recirculated into the intake air before reaching the turbocharger is appropriate for the turbocharged intercooled diesel engine [13]
Summary
Saving oil resources and reducing the emissions of greenhouse gases have become the worldwide consensus when the earth is faced with the environment and energy sources challenges [1,2,3]. Turbocharging, high-pressure fuel injection, exhaust gas recirculation (EGR), electronic-control fuel supply system, and exhaust after-treatments successfully used in combination successively have become technical measures [6] to comply with emission legislations of various stages. Considering the cooling system of engine, the high pressure EGR method that the exhaust gas is recirculated into the intake air before reaching the turbocharger is appropriate for the turbocharged intercooled diesel engine [13]. The turbocharged direct injection diesel engines applied to vehicles usually work under variable operating conditions, and the standard. The other EGR pattern that introduces exhaust gases into the intake air after reaching the turbocharger would delay the engine responses under the transient operating conditions, which would have an unfavorable effect on controlling the NOx emission
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