Review on Advanced Low Temperature Combustion Approach for BS VI 2017-26-0042

With the announcement, as per draft notification GSR 187 (E) dated 19^th Feb 2016 issued by MoRTH (Ministry of Road Transport and Highways), on vehicle emission standards to leapfrog from BS IV to BS VI by 2020, diesel engines would be greatly facing challenges to meet the stringent emission requirements of 90% reduction in PM and 50% reduction in NOx emissions simultaneously. Up to BS IV, in-cylinder strategies utilizing higher fuel injection pressure, higher intake boost, lower to moderate EGR, optimized combustion chamber design and lower intake manifold temperature would be sufficient. But meeting emission levels at BS VI levels would require a combination of both in-cylinder combustion control and after treatment system [1]. However, unlike Europe and US markets where wide spread adoption of after treatment solution is viable, for Indian market it would be impeded by infrastructure availability, system cost and cost of ownership. However use of advanced combustion concepts like low temperature combustion (LTC) in such scenario would not only reduce the PM and NOx levels to very low levels but also reduce cost and complexity of aftertreatment systems.

Low temperature combustion (LTC) concept is a promising technology to reduce both NOx and PM emissions simultaneously to meet future emissions. However, some challenges such as high CO and HC emissions during low load operation, achieving homogenous charge, limited operating zone and lack of combustion phase control are limiting the commercialization of such advanced combustion technique. Extensive research work is going on worldwide to overcome these limitations through various advanced engine technologies e.g. high EGR levels, boosting technologies, high pressure injection system, multiple injection strategies and variable valve timing (VVT). This paper reviews LTC strategies and methodologies to address challenges for heavy duty diesel engines for low and medium load conditions and further reflects a cost assessment for such advanced engine technology compared with conventional diesel engine technology.