分会场

高效清洁燃烧

摘要

Large-eddy simulations coupled with a finite-rate chemistry and a partially-stirred reactor model are carried out to investigate the effects of n-heptane injection timing on the n-heptane/methanol dual-fuel (DF) combustion under engine-like conditions. Methanol is gasified and premixed with air to form a homogeneous mixture with an equivalence ratio of 0.3 in a constant volume chamber (T=1000 K, ρ =14.8 kg/m3). Liquid fuel n-heptane is injected into the chamber to mimic the pilot fuel injection in DF engines. The effects of n-heptane injection timing are investigated, by varying the start of injection (SOI) time from 0 to 1.2 ms. The LES results reveal that there are three stage heat releases in the DF combustion. With the increase of SOI time, the mass fraction of hydrogen peroxide in the ambient mixture increases, leading to an early formation of hydroxyl and high-temperature ignition kernel. Therefore, two stage ignition delay times (IDTs) of n-heptane decrease. Meanwhile the ambient methanol IDT increases. Results also show that the cool flame is eliminated after the auto-ignition of the ambient methanol.

关键词

Large eddy simulation;Dual-fuel combustion;Engine Combustion Network;Ignition;Injection timing

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