Comparative Study On Combustion And Emissions Of P50/Methanol Dual Fuel And Diesel/Methanol Dual Fuel Engine

This paper is based on a four-cylinder high-pressure common rail diesel engine,equipped with a methanol control system,converted to a dual-fuel engine,and operated under small,medium and large loads at a speed of 1800 r / min.Taking P50/methanol dual fuel and diesel / methanol dual fuel as the research objects,when the methanol blending ratio is 20% and 40%,the combustion and emission laws of the two are compared,and the cylinder pressure sensor and combustion analyzer are used to monitor the cylinder.The internal pressure changes,realtime recording pressure data,and based on this calculation of combustion heat release rate and combustion temperature.The exhaust gas analyzer and particulate matter particle size spectrometer are used to measure the NO_x and particulate matter produced by the dual fuel engine.According to the above indexes,the combustion and emission characteristics of the two dual-fuel engines are analyzed.Second,the introduction of Exhaust Gas Recirculation(EGR).Under the conditions of small,medium and large loads,the changes of combustion and emissions of dual fuel engines under different EGR valve openings are studied.Research indicates:(1)The combustion duration of P50/methanol dual fuel is shorter than that of diesel / methanol dual fuel and pure diesel under the three loads of small,medium and large;under the three loads of small,medium and large,P50/methanol dual fuel The maximum combustion pressure of fuel is higher than that of diesel / methanol and pure diesel;the maximum value of instantaneous heat release rate of P50 /methanol dual fuel is higher than that of diesel / methanol dual fuel and pure diesel;during the lag period,P50 The average temperature in the cylinder of methanol / methanol dual fuel is close to that of diesel / methanol dual fuel,which is significantly lower than that of pure diesel.The average temperature in the P50/methanol dual fuel cylinder is higher than that of the diesel / methanol dual fuel and pure diesel during the rapid combustion period and the slow combustion period.Entering the stage of supplementary combustion,the average temperature in the cylinder of P50/methanol dual fuel is gradually lower than that of diesel / methanol dual fuel and pure diesel;under the same load,the peak pressure of P50 / methanol dual fuel changes cyclically when the methanol blending ratio is the same The rate is lower than that of diesel / methanol dual fuel,but higher than that of pure diesel;when the EGR valve opening is increased,the maximum value of in-cylinder pressure,the maximum value of instantaneous heat release rate,and the average temperature in the cylinder of both dual-fuel engines decrease.(2)Under light load conditions,the NO_x produced by P50/methanol dual fuel combustion is slightly higher than diesel / methanol dual fuel,but lower than pure diesel;under medium load conditions,P50/methanol dual fuel and diesel / methanol dual fuel The NO_x produced by combustion is similar and lower than that of pure diesel;under heavy load,the NO_x emissions produced by P50 / methanol dual fuel combustion are both lower than that of diesel / methanol dual fuel and pure diesel.When the EGR valve opening is increased,the NO_x emissions from both dual fuel and pure diesel combustion are reduced.(3)Under light load conditions,the quantity and volume concentration of nuclear particulate matter and Aegean mode particulate matter emitted by P50/methanol dual-fuel engine are slightly higher than that of diesel / methanol dual-fuel engine and lower than pure diesel;condensed particulate matter Lower than diesel / methanol dual fuel and pure diesel.Under medium and heavy load conditions,the quantity concentration and volume concentration of nuclear particulate matter,Aigen mode particulate matter and condensed particulate matter emitted by P50/methanol dual fuel engines are lower than those of diesel / methanol dual fuel and pure diesel.Under the small,medium and large load conditions,the geometric mean particle size of the particulate matter emitted by the P50/methanol dual fuel engine is smaller than that of the diesel / methanol dual fuel and pure diesel combustion modes.When the EGR valve is opened and increased,the changes of the particulate concentration and volume concentration of the two dual-fuel and diesel combustion emissions show an upward trend,and the peak values of the volume concentration and volume concentration shift toward the direction of large particle size.