Study On The Matching Of Common Rail Fuel System For Type 378 Diesel Engine

Diesel engine has many advantages such as stronger power,better economy,high reliability and so on.It has been widely applied in non highway area.With the increasing use of non highway diesel engines,emissions of pollutants such as NOx and PM are also increasing,which has become one of the main factors of environmental pollution.A good match between diesel fuel system and combustion system can improve the effect of combustion and reduce the emissions.Taking the 378 type non highway high pressure common rail diesel engine as the research object,the structure parameters of the fuel injector and combustor,the adjustment parameters of the fuel system,as well as the matching method are studied by the combination of simulation and test analysis.A high pressure common rail fuel injector flow test equipment was used to study the effects of different gasket thickness and flow control valves of the fuel injector on the injection characteristics.The effects of different nozzle structures on the spray characteristics were studied with spray test rig.The concept of spray difference was proposed and the consistency of the shape of the sprayed jets from different nozzles of the same injector was analyzed.The results show that when the flow ratio and the thickness of air gap gasket in the control valve of the injector are increased,the injection quantity in each cycle was decreased and the injection delay was increased;While the armature lifter gasket thickness was increased or the nozzle spring pressure regulating gasket is decreased,the injection quantity in each cycle was increased,but changes of the two have little effect on the injection delay.When the k coefficient of the orifice and extruding increment were increased,the penetration distance of the oil beam increases and the spray cone angle were decreased.For injectors with different nozzle angles,the increment of sizing is increased when the nozzle is processed,and the degree of difference in spray is increased.The model of fuel atomization and combustion in cylinder of type 378 diesel engine was built by using AVL software.The fuel distribution,turbulent kinetic energy,NOx and Soot generated in 3 different combustion chambers were simulated,and the influence of the position of oil beam dropping point on the fuel distribution and flow field in the combustion chamber was analyzed.The results show that the angle of the lip at the inlet of the combustion chamber and the increase of the height of the central convex platform can increase the strength and uniformity of the tumble flow in the combustion chamber and promote the full mixing of fuel and air.When the position of the oil beam is close to the inlet of the combustion chamber,the air flow in the combustion chamber is close to the wall movement,which leads to the obvious oil beam impingement.When the position of the oil beam is close to the bottom of the combustion chamber pit,the air flow in the combustion chamber is weakened.If the position of the falling point is too high or too low,it will lead to the uneven distribution of the combustible mixture in the combustion chamber.According to the analysis of the flow field in the combustion chamber,the distribution of combustible mixture and the formation of pollutants,the Omega combustor with a deep crater and a large protruding platform with a lip round angle was selected with the structure parameters of the combustor determined.The location of the oil bunches is 50%of the depth of the combustion chamber.The matching test of fuel system and combustion chamber was carried out,and a test bench for 378 diesel engine emission performance was set up.Fuel injector structural parameters,fuel system adjustment parameters,and nozzle extension heights were studied for the power performance,economy,and emissions of the diesel engine.Combination calculation with AVL-Fire and Boost were used to analyze the influences of different fuel injection adjustment parameters and level combinations on the emissions and economy of diesel engines.The regression equation is fitted by taking the fuel system rail pressure,main injection advance angle,main pre-spray interval angle and pre-injection amount as independent variables,and NOx,Soot,specific fuel consumption and other parameters as dependent variables.It is determined that the fuel system rail pressure range of the 378 diesel engine is in the range of 80-100MPa,the main injection advance angle is in the range of 5°CA-6°CA,the main pre-spray interval angle is in the range of 15°CA-16°CA and pre-injection quantities range from0.9mm³ to 1.0mm^3.The change rule of the diesel engine's pollutant and economy is studied.Parameters of nozzle diameter of injector,the injection adjustment parameters of the main injection advance angle,the rail pressure,the different nozzle protruding height and the emission of NOx,HC and smoke are measured.The diameter of the injection hole of the injector is 0.149mm and the height of the nozzle is1.6mm.The MAP diagram of the parameters such as the rail pressure of the fuel system,the main injection timing and the main pre injection interval angle of the378 type diesel engine is determined,which provides a reference for the matching of the fuel system and the combustion chamber of the non Highway diesel engine.A 378-type diesel engine test bench of emission performance was set up,and the research work on the emission and economy of the diesel engine was carried out.The influences of different nozzle diameters,nozzle extension height,fuel system rail pressure,main injection advance angle,main pre-spray interval,and pre-injection quantity on the NOx,HC,smoke,and fuel consumption of the diesel engine were analyzed.The fuel injector nozzle diameter is 0.149mm and the nozzle extension height is 1.1mm.The fuel injection system adjustment parameters such as the rail pressure,the main injection timing and the main pre-spray interval angle of the fuel system of the 378 diesel engine are determined.It provides reference for the matching work of non-road diesel fuel system and combustion chamber.