Influence of high rates of supplemental cooled EGR on NOx and PM emissions of an automotive HSDI diesel engine using an LP EGR loop

• Published in: International journal of energy research Vol. 32; no. 15; pp. 1383 - 1398
• Main Authors: Maiboom, A., Tauzia, X., Hétet, J.-F.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.12.2008; Wiley
• Subjects: Air pollution caused by fuel industries; Applied sciences; diesel engine; Energy; Energy. Thermal use of fuels; Engineering Sciences; Engines and turbines; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; exhaust gas recirculation (EGR); Fluid mechanics; Fluids mechanics; in-cylinder emissions reduction; low-pressure EGR loop; Mechanics; NOx-PM trade-off improvement; Physics; pollutant emissions; Pollution reduction; Diesel fuel; Turbine; low-pressure EGR loop; Fuel consumption; Flue gas recirculation; Combustion; High temperature; Pollutant emission; in-cylinder emissions reduction; Trade; pollutant emissions; Gas flow; Particle emission; High speed; Control method; Nitrogen oxide; Air pollution control; NOx-PM trade-off improvement; Diesel engine; Injection; Experimental study; Standards; High pressure; Geometry; Cylinder; exhaust gas recirculation (EGR)
• ISSN: 0363-907X; 1099-114X
• DOI: 10.1002/er.1455

Previous experimental studies on diesel engine have demonstrated the potential of exhaust gas recirculation (EGR) as an in‐cylinder NOx control method. Although an increase in EGR at constant boost pressure (substitution EGR) is accompanied with an increase in particulate matter (PM) emissions in the conventional diesel high‐temperature combustion (HTC), the recirculation of exhaust gases supplementary to air inlet gas (supplemental EGR) by increasing the boost pressure has been suggested as a way to reduce NOx emissions while limiting the negative impact of EGR on PM emissions. In the present work, a low‐pressure (LP) EGR loop is implemented on a standard 2.0 l automotive high‐speed direct injection (HSDI) turbocharged diesel engine to study the influence of high rates of supplemental cooled EGR on NOx and PM emissions. Contrary to initial high‐pressure (HP) EGR loop, the gas flow through the turbine is unchanged while varying the EGR rate. Thus, by closing the variable geometry turbine (VGT) vanes, higher boost pressure can be reached, allowing the use of high rates of supplemental EGR. Furthermore, recirculated exhaust gases are cooled under 50°C and water vapour is condensed and taken off from the recirculated gases. An increase in the boost pressure at a given inlet temperature and dilution ratio (DR) results in most cases an increase in NOx emissions and a decrease in PM emissions. The result of NOx–PM trade‐off, while varying the EGR rate at fixed inlet temperature and boost pressure depends on the operating point: it deteriorates at low load conditions, but improves at higher loads. Further improvement can be obtained by increasing the injection pressure. A decrease by approximately 50% of NOx emissions while maintaining PM emission level, and brake specific fuel consumption can be obtained with supplemental cooled EGR owing to an LP EGR loop, compared with the initial engine configuration (HP moderately cooled EGR). Copyright © 2008 John Wiley & Sons, Ltd.