Advanced combustion systems that simultaneously address PM and NOx while retaining the high efficiency of modern diesel engines, are being developed around the globe. One of the most difficult problems in the area of advanced combustion technology development is the control of combustion initiation and retaining power density. During the past several years, significant progress has been accomplished in reducing emissions of NOx and PM through strategies such as LTC/HCCI/PCCI/PPCI and other advanced combustion processes; however control of ignition and improving power density has suffered to some degree - advanced combustion engines tend to be limited to the 10 bar BMEP range and under.
Experimental investigations have been carried out on a light-duty DI multi-cylinder diesel automotive engine. The engine is operated in low temperature combustion (LTC) mode using 93 RON (Research Octane Number) and 74 RON fuel. The presented approach uses multiple injections of low cetane (gasoline-like) fuels in a Multizone, Stratified Compression Ignition (MSCI) approach in an effort to improve control of combustion phasing and increase the engine load such that the practicality of the combustion system is increased compared to other LTC approaches. In the present work, different ignition quality (RON) fuels are examined to determine the effect on the combustion, emissions and performance. Considering the operational complexity of a multi-cylinder engine, an effort was made to reduce the variability of the boost pressure and injection timing, while EGR percentage and injection pressure were used as parameters in this study. At low load operation, the lower RON (i.e. easier to ignite) fuel displayed improved performance while at higher loads, the higher RON fuels displayed improved performance - primarily due to managing the ignition propensity, or ease of auto-ignition, of each operating condition.