LES/TPDF investigation of the effects of ambient methanol concentration on pilot fuel ignition characteristics and reaction front structures

Large-eddy simulations with a transported probability density function model coupled finite-rate chemistry is applied to study the ignition process of an n-heptane spray in constant volume chamber premixed methanol-air atmosphere under conditions relevant reactivity controlled compression (RCCI) engines. Three reacting cases initial equivalence ratio (?m) ranging from 0 0.3 are investigated at temperature 900 K. The case setup based on Engine Combustion Network Spray-H configuration, where fuel used. effects ambient characteristics and reaction front structures n-heptane/methanol RCCI combustion studied detail. It found that methanol affects low n-heptane, which results change spatial distribution key species such as heptyl-peroxide, therefore cool flame structure. With presence mixture entire fuel-rich region jet, while when absent mixture, established only around stoichiometric close injector nozzle. In general, both low- high-temperature stages retarded by chemistry. An increase ?m leads decrease peak heat release rate first-stage ignition. inhibits decreasing overall hydroxyl radicals (OH) formation reducing OH concentration during transition period second-stage As result, time between two prolonged. Under present lean methanol/air conditions, impact has tendency high-temperature, region, favor soot reduction.