Experimential Investigation On The Characteristics Of Macroscopic Spray And Combuetion Of Pine Oil/PODE_3-4/diesel Blends

With ever-growing energy consumption and environment deterioration,the exploration of potential promising substitutes for diesel is of importance.As a renewable alternative fuel,pine oil has drawn extensive interest at home and abroad.However,due to the lower cetane number and oxygen content of pine oil,adding pine oil to diesel results in knocking and low efficiency.Polyoxymethylen dimethyl ethers（PODE）have obtained extensive attention due to its significant advantages such as high cetane number,volatilization,oxygen content and soot-reduction potential.Considering the quality of fuel atomization plays a key role in engine performance and emissions,an investigation based on visual constant volume combustion bomb is carried out to investigate the characteristic of macroscopic spray under different injection pressures,ambient pressures and nozzle diameters with conventional diesel（D100）,mixing pine oil with diesel at blending ratio of 20/80（PD20）and mixing PD20 with blending 10%,20%PODE3-4 by volume（PDP10、PDP20）.Furthermore,the characteristics of engine performance,combustion and emissions under different BMEPs in a 4-cylinder diesel engine with four tested fuels are also studied.The results demonstrate that the enhanced injection pressure can improve the fuel atomization and evaporation.An increasing trend was observed in spray penetration,spray volume,and mass of entrainment quantity of four tested fuels with increased injection pressure,while the spray front speed first tempestuously fluctuated then steady developed.Under an equal injection pressure,upon adding pine oil to D100,the spray penetration increased;after adding PODE3-4 to PD20,the spray penetration further lengthened whereas no consistent trend was observed in spray volume,and mass of entrainment quantity.With the enhanced ambient pressure,macroscopic spray characteristic such as spray penetration,spray volume,and mass of entrainment quantity decreased while spray cone angle increased.The spray front speed first shaply decreased then slowly decreased and finally leveled off.The spray characteristics,including spray penetration,spray volume,mass of entrainment quantity and spray cone angle,increased with increasing nozzle diameters.When compared with D100,the addition of pine oil results in a higher peak in-cylinder pressure,heat release rate and a higher BTE.Upon adding PODE3-4 to PD20,the peak in-cylinder pressure and heat release rate and BTE further increases.Under the low and medium load condition,the ignition delay period of PD20,PDP10 and PDP20 shortened,while MPRR increased.The BSFC of PD20,PDP10 and PDP20 decreased with increased BMEPs.At 0.4 MPa BMEP,adding pine oil to D100 accelerated the formation of CO,HC and NO.,while decreased the soot formation;upon adding PODE3-4 to PD20 led to an improvement in CO and HC production.As BMEP increased,a decline in peak concentration of nucleation mode particle and accumulate mode particle were obtained.MWhen BMEP<1.6 MPa,the addition of PODE3₄ to PD20 can improve the production of nucleation mode particle and sub-50 nm particle.At 1.6 MPa BMEP,adding PODE3-4 to PD20 can improve the formation of accumulate mode particle.Under any BMEP,the proportion of the mass concentration of sub-50 nm particles to the total particle mass concentration was all small.