Abstract
Future diesel engines for passenger car, light duty, heavy duty and off-road applications will have to cope with a very complex and demanding set of customer, regulatory and business requirements. Regulatory requirements, mainly, are concerned with emissions and upcoming fuel efficiency (CO2 emissions). Current diesel engines are efficient but expensive and complicated because they try to reduce NOx and soot simultaneously through expensive aftertreatment devices e.g. SCR and LNT for NOx and DPF for soot emissions. These devices are expensive and also high maintenance cost. Hence, several researchers has done great amount of work carried out by worldwide researcher to improve the NOx-PM trade-off which main concern for diesel engines through HCCI, PCCI, High Injection Pressures, Multiple injections and advanced injection Rate Shaping (RS) concept.
This paper mainly focussed on potential of Combustion Chamber (CC) design parameters to improve in NOx-PM trade-off. It was considered different combustion chamber parameter and geometry to understand and study the possibilities to improve NOx-soot trade-off through combustion chamber design. The main objective of this work is to focus on design changes in combustion chamber which less expensive for change and reduce the load or dependency on expensive aftertreatment devices or reduce the number of regenerative intervals of DPF and reduce use of add blue. In this study four different CCs (CC-A, CC-B, CC-C and CC-D) were considered for analysis with different shapes and geometrical ratios. Two-way approaches followed for selection of final bowl and geometrical ratios. In 1st approach detailed combustion analysis performed using 3D-FIRE CFD software and selected final three best bowls (CC-A, CC-C and CC-D) for testing. In 2nd approach bowls were experimentally tested and results were compared. For experiments, injector spray angle and NTP tuned to the particular combustion chamber to get best results from each designed CC.
All experiments carried out 14-experimental points considered which represents the European Driving Cycle. After exhaustive experimental study, it was concluded that CC-D has shown very significant improvement in NOx-soot trade-off as compared to CC-A and CC-D. CC-C has shown 8% and 13% lower NOx as compared CC-A and CC-D respectively. Soot emissions lower by 28% and 55% respectively as compared to CC-A and CC-D. The smoke is very low at lower speed and at 1000 rpm, about 65% lower smoke was observed, also about 0.55% fuel efficiency improvement also observed.
KEYWORDS: Euro-VI Emissions, Combustion Chamber (CC), Improvement of NOx-PM Trade-off, Combustion Simulation, Cost of Ownership