Experimental Study Of Diesel/Furan And Diesel/Methyl Heptanoate In Blending And Dual Injection Modes For Engine Energy-exergy Balance

With the energy crisis and environmental pollution becoming increasingly serious,the internal combustion engine industry is facing serious challenges in the context of the double carbon target,and clean and efficient combustion has become the goal pursued by the power industry.The application of oxygenated fuels is an effective means of achieving clean power,with furan and methyl ester fuels becoming a hot topic of interest in recent years.However,the low calorific value of oxygenated fuels is relatively low and to some extent does not allow for efficient power requirements.Therefore,this project aims to investigate ways to improve engine efficiency and reduce pollutant emissions by using furan and methyl heptanoate with the same carbon to oxygen ratio in a diesel engine and conducting energy balance and exergy balance tests.In this study,energy balance and exergy balance tests were carried out on an inline fourcylinder high-pressure intercooled diesel engine(WP4G154E330)in dual-fuel and blending modes.The energy balance and exergy balance under dual-fuel and blending modes were firstly modelled,and then the effects of different loads,combustion boundary conditions(EGR rate,main pre-injection interval,main injection time),combustion modes,energy replacement rate and fuel characteristics on the energy balance and exergy balance of the engine were investigated.The main findings are as follows:(1)When the load was increased from 0.14 MPa to 0.84 MPa,the effective function percentage and the exergy efficiency of D100,F10-D and MH10-D increased by 17.46%,15.69%,15.64% and 16.18%,15.27% and 14.98%,respectively;when the load was increased from 0.14 MPa to 0.84 MPa,the exhaust gas temperature and flow rate,this led to an increase in the values and percentages of both exhaust gas loss and exhaust gas exergy transfer loss,of which the proportion of exhaust gas physical exergy transfer to total exhaust gas exergy increased by 14.14%,23.63% and 16.56% for D100,F10-D and MH10-D fuels,which was mainly due to the increase in exhaust gas temperature;when the load increased from 0.14 MPa to 0.84 MPa,the percentage of cooling loss and heat transfer exergy loss decreased,and the percentage of irreversible exergy loss for D100,F10-D and MH10-D decreased by 19.26%,16.17% and 18.93%.(2)In the combustion boundary conditions,the introduction of the EGR caused the effective function percentage and the exergy efficiency to decrease.Adjusting the main preinjection interval angle and the main injection moment increased the effective function percentage of F10-D and MH10-D by 0.59%,0.9% and 0.39%,0.43% respectively,and appropriately adjusting the main pre-injection interval angle and the main injection moment also increased the exergy efficiency of the fuel.As the EGR rate increases,the effective function percentage and the exergy efficiency show a decreasing trend,which is because the introduction of EGR reduces the in-cylinder temperature and pressure.When the main pre-injection interval angle is 10°CA,the effective function percentage and the exergy efficiency are the largest and the percentage of irreversible exergy loss is the smallest.The cooling loss and exhaust loss of the engine are not sensitive to the change of the main pre-injection interval angle.With the advancement of the main injection moment,CA50 decreases,and the effective function percentage and the exergy efficiency increases.(3)More energy and exergy enters the system in dual-fuel mode than in blending mode,due to the deterioration of fuel consumption in dual-fuel mode;the effective function percentage in the blending mode is better than that in the dual-fuel mode,with the effective function ratio of F10-B and MH10-B being 1.16% and 1.23% higher than that of F10-D and MH10-D respectively at 0.7 MPa,and the same trend is observed for the exergy efficiency,this is due to the higher in-cylinder temperature and pressure in the blending mode,which optimizes the combustion conditions;the value and proportion of irreversible exergy loss in the blending mode are smaller because more intermediate products are produced in the dual-fuel mode,which increases the irreversibility of the combustion process,and in the dual-fuel mode,furan and methyl heptanoate macromolecules pass through the low temperature environment of the inlet tract before fragmentation to reduce their molecular activity,and the two together make the irreversible exergy loss in the dual-fuel mode smaller,the combined effect of these two factors increases the irreversibility in the dual-fuel mode.(4)When the energy substitution rate of furan and methyl heptanoate fuels increases from10% to 20%,the effective function percentage and the exergy efficiency increases.The F10-D is less efficient than the MH10-D in terms of effective function percentage and exergy efficiency due to the higher intake tract air resistance at lower furan injection volumes.The energy substitution rate increases and the percentage of irreversible exergy loss increases because when the inlet tract macromolecular fuel increases,it makes the overall fuel exergy destruction higher and increases the irreversibility of the whole reaction process.The four fuels F10-D,F20-D,MH10-D and MH20-D were compared in terms of their economy of exergy,and their overall percentage of exergy showed a decreasing trend with increasing load,with the lowest percentage of exergy being achieved at 0.84 MPa for F10-D,F20-D,MH10-D and MH20-D,with 61.08%,60.11%,60.94% and 60.26%.In summary,the effect of adjusting the combustion pattern to achieve the goal of efficient combustion is better than that of changing the boundary parameters.At 0.7 MPa,the effective function percentage of F10-B and MH10-B is 1.16% and 1.23% higher than that of F10-D and MH10-D respectively,but adjusting the main pre-injection interval only increases it by 0.59%and 0.9%,and the advancement of the main spray moment only increases it by 0.39% and0.43%.The energy replacement rate is increased from 10% to 20%,increasing the percentage of irreversible exergy loss,but also increasing the effective function percentage and the exergy efficiency of the machine.The F20-D has the best power and economy at medium to high loads,and at medium to low loads the F20-D has the best power and the F10-D has the best economy.