| The development of clean and renewable energy has important long-term significance and practical needs for reducing China’s dependence on foreign oil,realizing the diversification of energy structure,ensuring national energy security and realizing the"double carbon"goal,and promoting the sustainable development of China’s economy and society.The n-pentanol is a clean and renewable fuel,which can be prepared from wood fiber or sugar crops.It is rich in raw materials in sugarcane producing areas such as Guangxi.However,the sugar containing lignocellulosic waste has not been fully utilized in the development of China’s sugarcane industry.According to the relevant research trends at home and abroad,it is hoped to make good use of these wastes to produce n-pentanol on a large scale,so as to make comprehensive use of these resources.In recent years,with the technological progress in the field of biological enzyme engineering,the bioconversion rate of long-chain alcohols such as pentanol has gradually increased,and the economic advantages of n-pentanol fuel are gradually emerging,which shows a good prospect for its large-scale application.The n-pentanol can be miscible with diesel in any proportion,so it can be mixed with diesel to form mixed fuel,which is used in diesel engine.In this paper,simulation calculation and experimental research methods are used to make a comparative study on No.0 diesel(recorded as D100),blend fuel mixed with 25%n-pentanol in diesel(recorded as P25)and blend fuel mixed with 50%n-pentanol in diesel(recorded as P50).The research contents and results are as follows:.(1)Based on the self-made constant volume bomb and the self-made controller,the spray characteristics of pure diesel and amyl alcohol blended fuel(hereinafter referred to as blended fuel)were studied by means of high-speed photography.The spray test of blend fuel shows that the mist at the front of the pure diesel fuel bundle is more than that of the blend fuel.Compared with pure diesel,the penetration distance of fuel mixture was greatly reduced,the spray cone angle increased slightly,and the spray projection area greatly reduced.The spray projection area of P50 was only 42%of that of pure diesel.(2)Based on the detailed mechanism of n-pentanol combustion,DRGEP(Directed Relation Graph with Error Propagation),SA(Sensitivity Analysis),RPA(Reaction Path Analysis)and ROP(Rate Of Production)methods are integrated and applied,and the simplified kinetic mechanism of n-pentanol combustion is established.CFD program coupled with simplified mechanism was used to simulate the in cylinder direct injection combustion and pollutant generation of diesel and n-pentanol blend fuel.The combustion simulation results show that within a certain range after TDC,with the increase of crankshaft angle,the mixture concentration decreases gradually,the cylinder temperature increases gradually,and the NO_xemission increases gradually;Under the same crankshaft angle,the in cylinder high temperature area,mixture concentration,NO_x and soot of pure diesel,P25 and P50 decrease in turn.Compared with diesel fuel,n-pentanol fuel has lower combustion temperature,and there are obvious differences in cylinder temperature distribution and equivalence ratio distribution.NO_x distribution and soot distribution show some fragments of pollutants in the cylinder,which can provide a certain analysis basis.(3)Using a 2-liter turbocharged direct injection diesel engine,the combustion and emission of diesel engine fueled with blend fuel were studied.The results show that without EGR(exhaust gas recirculation),with the increase of n-pentanol mixing ratio,the maximum pressure in the cylinder and the specific emission of HC decrease,and the specific emissions of NO_x and CO increase.With the increase of EGR rate,the in cylinder pressure and NO_xspecific emission of blend fuel decreased,the CO specific emission fluctuated first and then increased significantly,and the HC specific emission decreased first and then increased,the soot emission is greatly reduced and has strong tolerance to large EGR rate.Under the same load,the specific emissions of CO and HC increase with the increase of the mixing proportion of n-pentanol.Under high load,the mixed fuel has a weaker"trade-off"relationship between NO_x and soot emissions than diesel.At low speed,the higher the mixing ratio of n-pentanol,the greater the heat release rate of the blend fuel.With the increase of engine rotating speed,the specific emissions of CO decreased first and then increased,and the specific emissions of HC and NO_x decreased continuously.With the increase of n-pentanol mixing ratio,the specific emissions of HC and NO_X decreased more.With the increase of injection pressure,the CO specific emission of pure diesel first decreases and then increases slightly,while the CO specific emission of blend fuel continues to decrease,the HC specific emission of pure diesel decreases,and the HC specific emission of blend fuel first decreases and then increases;With the increase of injection pressure,NO_x specific emission first increases rapidly and then slows down.Under the same injection pressure,the greater the proportion of n-pentanol in the blend fuel,the more NO_x emissions.Diesel engine burning blend fuel can improve the combustion process and reduce particulate emissions,but NO_x emissions increase.It is found that the soot emission of blend fuel is less sensitive to EGR,that is,when the EGR rate increases,the soot emission of blend fuel does not increase much,and the soot emission is less sensitive to EGR with the increase of n-pentanol mixing ratio.Combining EGR Technology with the use of n-pentanol fuel can reduce NO_x and particulate emissions at the same time.(4)The cetane number of n-pentanol is about 20.There is a large gap in ignition performance compared with diesel.Based on the above research and the concept of fuel design,2-ethylhexyl nitrate is used as cetane number improver to improve the blend fuel.0.5%.1%and2%2-ethylhexyl nitrate are added to P50 fuel to improve the cetane number(P50-E0.5%.P50-E1.0%and P50-E2%respectively).The effects of cetane number improvers on the combustion process,thermal efficiency and emission of n-pentanol blend fuel at different EGR rates were studied.The results show that adding cetane number improver to n-pentanol blend fuel has little effect on the cylinder pressure and heat release rate at low EGR rate.At high EGR rate,the cylinder pressure can be increased,and the crankshaft angle corresponding to the pressure peak can be advanced;When cetane number improver is added to the blend fuel,the ignition delay period is shortened,but it has little effect on the combustion duration;The ignition delay period of P50-E2%is equivalent to that of pure diesel.The maximum combustion temperature of the engine is higher than that of P50 fuel,but lower than that of pure diesel.P50 has lower thermal efficiency than pure diesel,while P50-E0.5%and P50-E1.0%fuels have higher thermal efficiency than pure diesel under low EGR rate conditions.Compared with pure diesel,the CO specific emission of P50-E1.0%and P50-E2%fuel is reduced,and the HC specific emission of P50-E2%fuel is reduced under the condition of high EGR rate;When EGR rate is less than 20%,the NOx specific emission of P50-E 0.5%,P50-E1%and P50-E2%fuel is reduced,when the EGR rate is 30%,the higher the proportion of cetane number improver is,the higher the NOx specific emission is;With the increase of additives,the soot emission of the improved P50 fuel is slightly higher than that of P50 fuel,but the soot emission is still significantly lower than that of diesel under all working conditions.Especially under high EGR rate,the improved P50 fuel basically maintains the characteristics of high EGR tolerance of P50 fuel.Based on the above test results,a better comprehensive optimization index of fuel economy and emission can be obtained by adding 1%cetane number improver of 2-ethylhexyl nitrate to n-pentanol mixed fuel.The research shows that the application of n-pentanol blend fuel in diesel engine has better practical prospect and potential.After optimizing the mixing ratio,optimizing various application parameters and improving the cetane number,n-pentanol fuel can basically meet the practical conditions in terms of power,economy and emission characteristics.The research data and analysis results can also provide a certain research basis for further studying the application of n-pentanol.The application of n-pentanol mixed fuel provides a good way for the comprehensive utilization of biomass such as sugarcane residue into renewable oxygenated fuel.The research data and analysis also have great theoretical significance and practical value for such follow-up in-depth exploration. |
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