Energy Conversion And Emission Analysis Of Gas Fuel Components In Internal Combustion Engine

With the rapid consumption of oil resources and the increasingly serious environmental pollution,more and more people take attention to the application of clean and renewable gas alternative fuels in the traditional vehicle internal combustion engine.In some areas of China,biogas and coke oven gas?COG?are very promising alternative fuels because of the huge production and low utilization.This thesis studied the combustion process,emission characteristics and availability of compression-ignition?CI?engine and spark-ignition?SI?engine fueled with different gaseous fuels.Based on a zero-dimensional single-zone combustion model,the combustion characteristics of methane,biogas and COG,such as temperature,pressure and species mole fractions were obtained by CHEMKIN software which is combined with the GRI-Mech3.0detailed chemical reaction mechanism.This thesis developed an availability analysis model for the combustion process of a CI engine fueled with gaseous fuels and and compiled program.Meanwhile,the effects of intake temperature,intake pressure,compression ratio,equivalence ratio and engine speed on emissions and availability were also studied.The results showed that,under the conditions conducted in this paper,CI engine fueled with COG has the highest NO_x emission,the lowest CO emission and the highest work availability proportion.And CI engine fueled with biogas has the medium NO_x emission and the lowest irreversible loss.Combined with the turbulent flame propagation model in a quasi-dimensional model,the1D mathematical model of working process of SI engine was developed by GT-Power software and the combustion characteristics of methane,COG and syngas?80%H₂ and20%CH₄?were obtained.This thesis developed an availability analysis model for the combustion process of a SI engine fueled with gaseous fuels and and compiled program.Meanwhile,the effects of compression ratio,throttle angle and ignition timing on emissions and availability of COG engine were also studied.The results showed that,the combustion rate of methane,COG and syngas was accelerated,the combustion duration was shortened,and the irreversible loss of combustion process was reduced.Under the conditions conducted in this paper,the second-law efficiencies?exergy efficiencies?of methane,COG and syngas increased.COG has the highest first-law efficiency?thermal efficiencies?and the lowest brake specific fuel consumption.The results showed that the irreversible loss of SI engine fueled with COG can be reduced by properly increasing the compression ratio,increasing throttle angle and delaying ignition timing.