Study On Spray And Combustion Characteristics Of New Type Diesel Nozzle

With the implementation of the China emission standard,diesel emission regulations have been increasingly stringent,therefore,further improvements of the performance and reduction of emissions for diesel engines is very important.The quality of the diesel fuel injection system is related to the atomization quality of the spray mixture,the structure of the injector nozzle directly determines the macro and micro characteristics of the spray,and improving the structure of the nozzle to improve the quality of the atomization mixture is the most direct and effective way to improve the diesel engine injection system.Compared with ordinary nozzles,the intersecting hole nozzles have the characteristics of small penetration and large spray cone angle.Researches showed that intersecting-hole nozzles have excellent performance in improving engine performance and emission.It is necessary to study and optimize the structure of intersecting-hole nozzles to understand the flow characteristics and spray formation mechanism of intersecting-hole nozzles.In this paper,the influences of the internal structure of nozzle on the internal flow and spray characteristics of the cross-hole nozzle was studied by numerical simulation.The results show that with the increase of the intersection angle,the projection number and distribution range of the forward flow line at the nozzle outlet section increased,the spray penetration distance and SMD decreased.With the increase of the angle β between the axis of the cross hole and the vertical direction,the mass flow rate of the cross hole nozzle continuously increased,the spray penetration distance increased,and SMD first increased and then decreased.With the increase of the radius of the sac chamber,the mass flow rate of the cross-hole nozzle increased continuously,the spray penetration and SMD increased.When the profile of the sac chamber changes,with the decrease of the volume of the sac chamber,the mass flow rate first increased and then decreased,the spray penetration first increased and then decreased,and SMD first decreased and then increased.When the length of the cross-hole confluence area increased from 0.5mm to 0.7mm,the spray penetration distance first increased and then decreased,and SMD first decreased and then increased.Compared with the discharge coefficient of the cross-hole nozzle in the no-confluence area,the spray penetration distance decreased and SMD increased;When the K factor of the upper sub-hole increased from 0 to 3,the spray penetration decreased first and then increased,and SMD increases first and then decreased.Based on a single-cylinder 135 diesel engine and a double-layer split combustion chamber,the combustion and emission characteristics of different cross-hole nozzles were numerically studied.The results show that the mass fraction of NO formed in the cylinder was the smallest at the sac chamber radius of 0.7mm,which is 1.23×10-6.Under different sac chamber types,the maximum mass fraction of NO generated in the type-I sac chamber was the smallest,which is 5.20×10-6.Under different confluence area length,the maximum mass fraction of NO formed in the 0.5mm confluence area was the smallest,which was 6.90×10-6.Under different k-factor of upper sub-hole,the mass fraction of NO generated was the smallest when k=2,which was 8.92×10-6.