Abstract
Research and Engineering Objective
The reduction of both NOx and PM exhaust emission is very important to protect clean atmospheric air and also the reduction of fuel consumption (BSFC) is needed urgently. This means to reduce CO2 and it can be prevent the global warming. But it is very difficult to reduce both the exhaust emissions and BSFC simultaneously and also it is difficult to use EGR in high boosted turbo-intercooled engine. The authors propose the high EGR rate combustion by using high pressure loop EGR and Low pressure loop EGR under the high boost pressure condition in a six-cylinder heavy duty diesel engine.
Experimental Equipment as Methodology
The tested engine has 10.5L displacement with turbocharger and intercooler. The target performance has a rated power of 300 kW (BMEP=1.7 MPa) and peak torque of 1842 Nm (BMEP=2.2 MPa). The engine is equipped with high pressure fuel injection of 200 MPa level by a common rail system and a variable geometry turbocharger (VGT), which is newly developed. The maximum pressure ratio of the compressor has 5.0 capability and this means twice of the ordinary turbocharger (about 2.5). Finally, the wide range and high rate EGR will be achieved by the high and low pressure loop EGR system with VGT.
Experimental Result
The high and low pressure loop EGR system with VGT can increase twice EGR rate compared with the high pressure loop EGR only and reduce BSNOx to around a half without Smoke deterioration in a medium engine speed 1200 rpm and 40% load. The reduction of BSNOx is 1/8 in comparison with the case of without EGR and BSFC is same level between with EGR and without EGR. This EGR system was tested practically to improve exhaust emissions in both steady state and transient test conditions. Finally, the tested engine with after treatment such as oxidation catalyst, lean NOx catalyst and DPF was evaluated and was checked experimentally by the JE05 transient test mode to meet the target performance.
Limitation of this study
The test engine is not production specification but is prototype and has not evaluated cold start test cycle.
What does the paper offer that is new in the field Recently, the diesel engine with the high and low pressure loop EGR launched a few in passenger cars only but there is no experimental data about the effect of each EGR system. The authors tested each EGR system such as the high, the low and the combined EGR system and evaluated the effect of each EGR system to reduce diesel emissions.
Conclusion
The high and low pressure loop EGR system with VGT has a good performance and increases EGR rate to reduce BSNOx while maintaining BSFC and PM simultaneously, not only in the steady state condition but also in the transient condition. This system is effective to improve diesel emissions furthermore.
Key Words : Diesel, Emissions, NOx, PM, EGR, BSFC, CO2, Injection, Turbocharger