Experimental Study And Simulation Analysis Of Biodiesel/Diesel Constant Volume Spray Characteristics

As the petroleum energy reserves on the earth are declining and the air quality is getting worse and worse,it is imperative to develop sustainable and less polluting new energy sources to replace non-renewable petroleum energy.Biodiesel can be extracted from various animal and vegetable oils and waste oils in nature.Compared with petroleum energy,its production cycle is shorter and its pollution to the environment is greatly reduced,so it has received widespread attention.In addition,the spray characteristics of fuel are affected by the type of fuel,injection pressure(Pinj)and environmental back pressure(Pamb).Research on the spray characteristics of biodiesel is a very important part of improving engine combustion and emission characteristics.In this paper,biodiesel and diesel fuels prepared from waste oil are selected as the research objects.Through a combination of constant volume spray characteristics test and simulation analysis,the two fuels are studied at Pinj at 80 MPa and 160 MPa,and Pamb at0.1MPa,1MPa.And spray characteristics under 2MPa conditions.The spray characteristics test results show that the spray penetration distance,spray tip velocity and SMD of biodiesel are larger than diesel,and the spray cone angle is smaller than diesel;as the injection progresses,the spray tip speed decreases,and the spray cone angle first increases and then decreases,and then Tend to be stable;increase Pinj,the spray penetration distance and spray tip speed increase,SMD decreases,and the spray cone angle changes little;increase Pamb,the spray cone angle and SMD increase,spray penetration distance and spray tip speed decrease.The simulation results of the injection hole internal flow show that: the fuel pressure drops rapidly at the nozzle entrance,and as the fuel flows to the nozzle exit,the pressure remains basically stable;in the axial direction of the nozzle,the fuel velocity rapidly increases to the maximum speed,maintaining Slowly decrease after a certain distance.In the direction of the nozzle hole diameter,the fuel velocity at the center axis of the nozzle hole is higher,and the velocity near the wall is lower;the initial generation position of cavitation phenomenon is near the corner of the nozzle hole entrance.As the fuel flows to the nozzle hole exit,the cavitation thickness is first After increasing and decreasing,supercavitation is formed at the outlet;turbulent kinetic energy is concentrated on the wall near the nozzle hole,and the turbulent kinetic energy of the lower wall of the nozzle is greater than that of the upper wall;the outlet velocity and gas volume fraction of biodiesel are smaller than that of diesel,and the outlet mass flow rate Slightly larger than diesel;increasing Pinj,nozzle outlet velocity,outlet mass flow rate and outlet gas volume fraction increase;increasing Pamb,nozzle outlet velocity and outlet gas volume fraction decrease,and the outlet mass flow rate does not change significantly.Based on the simulation results of the outlet velocity and the outlet mass flow rate of the fuel flow inside the nozzle,the external fog field is simulated.The results show that the spray penetration distance and SMD of biodiesel are greater than that of diesel;under the condition of constant Pamb,with Pinj When the increase,the spray penetration distance increases,and the SMD decreases accordingly;under the condition of the same Pinj,as the Pamb rises,the spray penetration distance decreases,and the SMD increases;in the radial direction of the spray,The droplet velocity near the center of the fog field is higher,and the velocity far away from the center is lower;in the axial direction of the spray,the droplet velocity near the nozzle outlet is higher,and the droplet velocity far away from the nozzle outlet is lower.