Experimental Study On The Effects Of Diesel-Ethanol-Tetrahydrofuran Blended Fuels On Performance Of Heavy-Duty Diesel Engine

In recent years,ethanol,as an oxygen-containing clean fuel,has gradually become a hot area of research.Numerous studies have shown that the application of ethanol can reduce the consumption of fossil fuels and carbon emissions.Solving the problem of the solubility between ethanol and diesel is the key to realize the application of ethanol in diesel engines.As a new oxygen-containing fuel and an excellent co-solvent,tetrahydrofuran(THF)has been widely concerned and studied.Based on the results of the titration experiments,suitable proportions of diesel-THF-ethanol and diesel-THF blends was selected to conduct experimental studies on combustion and emissions.The test fuels were diesel-THF-ethanol blends in different ethanol proportions(The proportions of THF were 5%.The proportions of ethanol were 10%,20%,and 30%,respectively),diesel-THF blends in different THF proportions(The proportions of THF were 5% and 15%,respectively)and pure diesel.The experiments were carried out under different loads and WHSC test cycles to analyze the effects of the blends on combustion and emissions.Two blended fuels,D85T15(The volume ratio of diesel was 85% and that of THF was 15%)and D75T5E20(The volume ratio of diesel was75%,that of THF was 5% and that of ethanol was 20%),and pure diesel(D100)were selected to carry out the experiments of adjusting injection strategies under different loads.At different temperatures,THF was used as a cosolvent for diesel-ethanol blended fuel,and the results showed that THF was completely soluble with diesel and ethanol.THF as a cosolvent could greatly improve the dissolubility between diesel and ethanol.Bench test showed that with the addition of THF and ethanol,the ignition delay period of the blended fuel was gradually prolonged,and the combustion duration was gradually shortened under the low load.When the proportion of ethanol reached 30%,the combustion was insufficient.With the addition of THF and ethanol,the ignition delay period of the blended fuel had little change,and the combustion duration was gradually shortened under the high load.With the increase of the proportion of THF,the brake thermal efficiency(BTE)of the blended fuel decreased gradually.With the increase of the proportion of ethanol,the BTE of the blended fuel increased gradually or even higher than that of pure diesel,with the maximum increase of 2.15%.With the addition of THF,the NOx emissions of the blended fuel increased.The NOx emissions of the blended fuel decreased first and then increased with the increase of the proportion of ethanol,which was even 1.97% lower than that of pure diesel under the low load.Soot emissions gradually decreased with the increase of the proportion of THF and ethanol,and the maximum decrease was 79.91%.The CO and HC emissions increased gradually with the increase of the proportion of THF and ethanol under the low load.The CO and HC emissions of the test fuels were basically the same under the high load.Under the WHSC test cycle,the weighted brake specific fuel consumption of the blended fuel increased gradually with the increase of the ratio of THF and ethanol.The NOx,CO and HC emissions increased gradually with the highest ratios of 23.0%,53.0%and 41.6%,respectively.The soot emissions decreased by 77.3% at the highest.When the proportion of ethanol reached 30%,the NOx,CO and HC emissions were significantly increased compared with pure diesel,and the soot emissions were significantly reduced.It can be seen that a too high proportion of ethanol in the blended fuel had a negative impact on fuel economy and emissions.Under different injection strategies,the BTE was reduced by the addition of THF,while the BTE of D75T5E20 was improved by the addition of ethanol,which was comparable to or even higher than that of pure diesel under the high load,with an increase of 0.01-0.47%.The addition of THF and ethanol increased NOx,CO,and HC emissions,and decreased soot emissions at 25% load.NOx and HC emissions increased,and soot and CO emissions decreased at 70% load.With the advance of the injection timing or the increase of the injection pressure,the effects of THF and ethanol on emissions decreased gradually.The above studies showed that THF can significantly improve the mutual solubility between diesel and ethanol,and the fuel economy and emissions were significantly improved by the diesel-ethanol-THF blended fuel.With the application of D75T5E20,the BTE of that was slightly higher than pure diesel.It can be achieved that the soot emissions of D75T5E20 was comparable to the optimized soot emissions of pure diesel,and the NOx emissions of D75T5E20 was lower at the same time with the delay of the injection timing or the decline of the injection pressure.