Computational and Experimental Investigation of Different Bowl Geometries on a CRDi Engine to Improve NO _x -PM Trade-Off and Fuel Efficiency

One of the major challenges for automotive industry today is to reduce tailpipe emission without compromising on fuel economy especially with the EURO 6, RDE, LEV III emissions and CO₂ norms coming up. In case of diesel engines, with the emission norms becoming stringent more and more, it's difficult to improve tradeoff between NO_x and PM emissions. After treatment systems give some edge in terms of tail pipe emission reduction but not on the cost, fuel economy and system simplicity front. For diesel engines the compression ratio and design of the bowl geometry plays a crucial role in controlling emission and CO₂. The target was to achieve EURO 6 tailpipe emissions with minimum dependency on after treatment. With the target after treatment conversion efficiency the engine out targets were framed.

A study of different bowl geometries were made that would help achieve this target of improving reduced engine out emissions. Four bowl geometries were designed for a compression ratio of 15.5:1 and based on their simulation results the best were taken up for experimentation. With a combination of reduction in compression ratio and optimized bowl geometry it was possible to reduce NO_x and soot emissions with slight increase in HC and CO and no penalty on fuel economy.