Combustion And Emission Characteristics Of Hydrogen/Diesel Dual Fuel Engines At Different Altitudes

As the altitude increases,the atmospheric pressure decreases,the air density and oxygen content decrease.As a result,when the diesel engine works under the hypoxia environment at plateau area,the combustion in the cylinder deteriorates and the emission increases.The National Six Light Vehicle Emission Law has improved the emission control requirements of diesel engine under plateau area.The State and the Automotive Engineering Society also have put forward the carbon emission reduction targets successively.Diesel engines burn the neutral carbon fuel or multiple fuel has become an urgent need at different altitude areas especially plateau area.Hydrogen is helpful to improve the combustion efficiency and decrease the emission of CO and soot due to its excellent physical and chemical properties.In order to explore the effects of diesel engines fueled with hydrogen/diesel dual fuel at different altitudes on combustion and emission characteristics,a hydrogen supply system was installed on a high pressure common rail diesel engine.The combustion and emission characteristics were systematically studied on this hydrogen/diesel dual fuel diesel engine with numerical simulation and bench test.The main results are as follows:1.The cylinder pressure and the pressure rise rate decrease first and then increase with the increase of hydrogen replacement rate,and are greater than those of pure diesel mode at medium and high loads under different altitudes.Under 50%and 70%loads,they increase by 26%and 180%at 100 k Pa,increase by 18.6%and 110%at 90 k Pa,and increase by 23.1%and 187%at80 k Pa,respectively.2.The emission of CO and soot decreased with the increase of hydrogen replacement rate at low and medium load.The reduction of CO emission is greater than that of soot emission at different altitudes.Under 30%load situation,The CO maximum reduction was 63.5%at 80 k Pa,the soot maximum reduction was 45.5%at 100 k Pa.Under 70%load situation,the CO maximum reduction was 45%at 100 k Pa,the soot maximum reduction was 32.8%at 80 k Pa.3.The NOx emissions basically increase with the increase of hydrogen replacement rate under different altitudes.The maximum increase for each load can be obtained at 80 k Pa,which was 63.8%,47.6%and 35.2%,respectively.4.The HC emission decreases first and then increases with the increase of hydrogen blending rate under different altitudes,and is higher than that of pure diesel at maximum hydrogen substitution rate.The maximum increase for each load can be obtained at 100 k Pa,which was 39.7%,83.7%and 22.2%,respectively.5.The CO₂ emissions decreased with the increase of hydrogen content under different altitudes.The maximum reduction of each load was 52.3%,38%and 37.2%at 100 k Pa.