Analysis of various fuels in DISI and PFI engines : separating mixing effects from crevice and quench layer effects

Abstract

The United States consumes billions of gallons of gasoline per year, threatening national security and causing environmental problems. Research in automotive research aims to resolve such problems. Solutions include turbocharged direct injection, spark ignition (DISI) engines for higher output and efficiency. But this comes at the cost of greater concentrations of unburned hydrocarbons (UBHC) in the exhaust during cold start, when the catalytic converter is further away from the engine. The time the catalytic converter takes to heat to an optimum efficiency is longer. UBHC can also accumulate in the cylinder chambers and can be caused by quenching effects or poor mixing. A system was set up to determine the significance of mixing in producing high concentrations of UBHC. A GM 2009 LNF Ecotec was modified to run PFI and DISI under operating conditions representative of cold start for isopentane, and gasoline with varying concentrations of ethanol. Results were inconclusive, indicating no relationship between neither the UBHC count in the exhaust of increasing ethanol concentration, nor differences between PFI and DISI. To make test results more reliable, more ethanol containing fuel types should be tested, and a sweep of spark times should be assessed. The set up does provide a good foundation for further studies in mixing research.