Control of combustion phasing and operating range extension of natural gas PCCI engines using ozone species

摘要

There are two major issues that restrain premixed charge compression ignition (PCCI) engines from being widely employed for industrial applications: difficulties in combustion controllability and limited operating range. These restrictions become even more severe when the engine runs with a very low reactivity fuel, such as natural gas (NG). Ozone gas, which is a species with a very high level of chemical reactivity, can be utilized to control and enhance the combustion process in the PCCI combustion strategy. In the present study, coupled multi-dimensional computational fluid dynamics (CFD) with proper detailed chemical kinetic mechanisms is employed to investigate the effects of ozone addition to the intake air and fuel mixture in a PCCI engine with different intake temperatures and equivalence ratios. It can be inferred from the results that combustion phasing advancement is in a direct proportion to the amount of ozone addition. It is seen that even low amounts of ozone (10 ppm) have considerable influences on the engine performance and emissions. The results show that adding 1000 ppm ozone makes it possible to decrease the needed initial temperature for PCCI combustion by 80 K. The results also reveal that ozone addition makes it possible to run engine with ultra lean fuel mixtures. It can be concluded that adding controlled amounts of ozone can assist in controlling PCCI engines and also extend operating range of the engine to lower intake air temperatures and also leaner fuel mixtures.