| The use of waste cooking oil biodiesel as an alternative fuel for diesel is a renewable energy recycling,which is of great significance for alleviating the energy crisis and improving the ecological environment.However,the high viscosity of waste cooking oil biodiesel limits its application in diesel engines.N-pentanol fuel has low viscosity and high oxygen content.Adding n-pentanol to waste cooking oil biodiesel can reduce its viscosity,improve its atomization performance,and make waste cooking oil biodiesel more suitable for diesel engines.The combustion and emission characteristics of n-pentanol/waste cooking oil biodiesel mixed fuel were studied through a combination of bench test and numerical simulation.The influence of n-pentanol/waste cooking oil blending ratio and injection pressure on the combustion and emissions of the mixed fuel was experimentally studied using an engine bench test system;A simulation model of a n-pentanol/waste cooking oil biodiesel mixed fuel engine has been constructed based on CONVERGE,and the effects of pre-main injection interval,pre-injection ratio,and main injection timing on the combustion and emissions of the mixed fuel were studied.The main research findings are as follows:(1)The effects of changes in the blending ratio of n-pentanol on combustion and emissions were studied.As the blending ratio of n-pentanol is increased,the ignition delay period is prolonged and the combustion duration is shortened,and the heat release center is moved forward.When using BP30 fuel under low load condition,the combustion situation deteriorates.Under medium and high load conditions,when the blending ratio of n-pentanol increase from 0%to 30%,the peak in-cylinder pressure is increased by 1.95%and 5.26%,respectively,and the peak premixed heat release rate is increased.As the blending ratio of n-pentanol is increased,both HC and formaldehyde emissions rise and Soot emission decreases by 25.86%,19.71%,and 31.59%under three different load conditions,respectively.Under high load condition,as the blending ratio of n-pentanol is increased,NO_x emission is rose,while CO emission is decreased.(2)The effects of different injection pressures on combustion and emissions were studied by using BP20 test fuel.As the injection pressure increases,the ignition delay and combustion duration are shortened,and the heat release center is moved forward.Under three loads,when the injection pressure increases from 120 MPa to 160 MPa,the peak pressure in the cylinder is increased by 6.21%,7.23%,and 8.32%,respectively,and the peak heat release rate is increased by 14.79%,4.86%,and 18.12%.With the rise of injection pressure under low load condition,HC and formaldehyde emissions are first decreased,and then increased when the injection pressure increased to 160 MPa.As the injection pressure is increased,CO emission is decreased and NO_x emission is increased.When the injection pressure increases from 120 MPa to 160 MPa,Soot emission is decreased by 50.52%,48.20%,and 52.13%under three different loads,respectively.(3)The effects of pre-main injection interval,pre-injection ratio,and main injection timing on combustion and emission were simulated and studied by using BP20 fuel.As the pre-main injection interval increases from 15°CA to 30°CA,the peak in-cylinder pressure is decreased by 5.80%,and the heat release rate curve shows a two-stage heat release form.With the pre-main injection interval increases,the ignition delay period is extended,the temperature in the cylinder is decreased,the high-temperature areas are decreased,and NO_x and Soot emissions are decreased by 21.30%and 27.46%,respectively.formaldehyde emissions near the cylinder head and in the top gap area are increased.As the pre-injection ratio increased from 0%to 20%,the peak pressure in the cylinder increased by 13.35%.the peak heat release is gradually increased during the pre-injection stage.With the pre-injection ratio increases,the ignition delay period and combustion duration are shortened,the heat release center is moved forward,the temperature in the cylinder is increased,the high-temperature areas are increased,NO_x emission is gradually increased,and Soot emission is decreased by 61.02%.formaldehyde emission first increase and then slightly decrease when the pre-injection ratio is20%.As the main injection timing is delayed from 9°CA before top dead center to 3.5°CA before top dead center,the peak in-cylinder pressure and heat release rate are decreased by17.82%and 19.04%,respectively.As the main injection timing is delayed,the ignition delay period is shortened,the combustion duration is extended,the temperature in the cylinder is decreased,the high-temperature areas are reduced,the heat release center phase is gradually moved away from top dead center,and NO_x and formaldehyde emissions are decreased.Soot emission is first increased and then slightly decreased when the main injection timing is3.5°CA before top dead center. |
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