Optical Study On Spray And Combustion Characteristics Of Diesel/Cyclopentanol Blends

The diesel engine still occupies an important position due to its good power and economy,and is widely used in passenger vehicles,commercial vehicles,construction machinery,agricultural machinery,ships and other transportation vehicles.Faced with increasingly stringent emissions regulations,diesel engines must address the issue of higher NOx and soot emissions.Adding oxygen-containing fuel to diesel is of great significance for exploring new clean energy and achieving efficient and clean combustion of diesel engines.Among the many second-generation biofuels produced from lignocellulose,cyclopentanol has great potential as a promising and environmentally friendly alternative to biofuels for automobiles.In this paper,10% and 20% by volume of cyclopentanol are added to diesel(remembered as D90CP10 and D80CP20).First,the physical and chemical characteristics of the cyclopentanol / diesel fuel were studied.Second,select three injection pressures(100,120,and 140 MPa)and four injection timings(the crank angles are-6,-9,-12,and-15 ° CA ATDC,respectively).The effect of cyclopentanol addition on diesel spray and combustion characteristics was investigated.Using two-color method to process high-speed photography method for the image of the bomb-containing spray and combustion process and the image of the combustion in the cylinder of the optical engine.Comparing the test results,the following conclusions are obtained:(1)As the proportion of cyclopentanol added to diesel increases,the viscosity,density,surface tension,and latent heat of vaporization of the mixed fuel gradually increase,and the cetane number and low heating value gradually decrease.(2)The test results of the bomb-containing spray characteristics show that under all injection pressure conditions,the spray cone angle of the cyclopentanol-diesel mixture is smaller than that of diesel,and D80CP20 can provide the longest spray penetration distance.The spray area indicates that the addition of cyclopentanol at all injection pressure conditions can improve air and fuel mixing.(3)The test results of bomb-combustion characteristics show that for the same fuel,increasing the injection pressure can reduce the luminous intensity INFL and KL factors.In addition,at all injection pressures,the fuel’s INFL and KL decreased as the blending ratio of cyclopentanol increased,and the soot of D90CP10 and D80CP20 decreased by 12.7-58% and 36.9-89.2% compared to D100,respectively.This is due to the physical effects of cyclopentanol on air-fuel mixing and the chemical effects on soot formation and oxidation.The analysis of the results of the luminous intensity and the flame floating length shows that the addition of cyclopentanol can effectively accelerate the combustion process.At the same time,the low injection pressure conditions are conducive to suppressing the adverse effects of low cyclopentanol low calorific value and low combustion speed on the combustion process.Under high pressure injection conditions,the addition of cyclopentanol will increase incomplete combustion losses.(4)Optical engine combustion analysis shows that increasing the injection pressure and the timing of the earlier injection can reduce the adverse effect of cyclopentanol on the thermodynamic combustion results and enhance the positive effect of cyclopentanol in promoting heat release.The addition of cyclopentanol is beneficial for improving the indicated thermal efficiency.For heat release and work,D90CP10 is a better alternative fuel than D80CP20,especially at-12 ° CA ATDC injection time and 140 MPa injection pressure.(5)Optical engine combustion image study found that compared to diesel,cyclopentanol-diesel blend fuels have reduced soot emissions over the entire combustion process.This is the common result of the improved spray and atomization quality,enhanced oxidation,increased combustion temperature and suppressed soot formation after the addition of cyclopentanol.In addition,the increase in injection pressure or the advance of injection timing can promote better mixing of fuel and air,which inhibits the formation of soot,but also weakens the positive effect of adding cyclopentanol on reducing soot.Compared with D80CP20,D90CP10 has more advantages in optimizing injection pressure and injection timing.