METHOD OF ORGANIZING TWO-STAGE FUEL INJECTION INTO A DIESEL CYLINDER USING A HYDROMECHANICAL FUEL EQUIPMENT

Abstract

The use of multiphase injection allows reducing the emission levels with exhaust gases and the noise of diesel engines. This paper proposes to improve the hydromechanical fuel supply system of diesel vehicles by providing the possibility of two-stage fuel supply. This task is solved by high-pressure fuel pump equipment, additionally by high-pressure sections that work to inject fuel for pilot injection. The drive shaft cams of these sections are ahead of the shaft cams of the main sections by 2-10 degrees rotation of the camshaft. In order to check the performance of the proposed two-stage fuel supply system and to confirm the possibility of achieving its stated parameters, calculation studies were performed based on mathematical modeling of hydromechanical processes in this system. Calculation studies were carried out using a mathematical model of the high-pressure fuel system of the Ch12/14 research single-cylinder diesel engine. The mathematical model is implemented in the MATLAB programming environment. Test results of calculations according to this mathematical model for the operating mode of the system at a camshaft rotation frequency of 650 min-1 and full fuel supply, the high-pressure system provides two-stage injection with the following indicators: total cyclic fuel supply 64 mm3/cycle, pilot dose - 9 mm3/cycle (which is 16% of the total cyclical supply); the maximum injection pressure is 49 MPa with a maximum pressure of 58 MPa in the over-plunger cavity; the maximum injection pressure of the pilot dose is 14.7 MPa, while the pressure reached in the over-plunger cavity is 26.5 MPa; the duration of the injection of the pilot dose is about 2 degrees rotation of the camshaft, the main one - 4.7 degrees rotation of the camshaft. The system also provides two-stage injection in modes according to the load (and speed) characteristics. When the load is reduced from the maximum by 35-40%, it does not affect the maximum injection pressure of the main part of the fuel at all speed modes of the system, after which there is a sharp drop of this parameter to the value of the maximum injection pressure of the pilot. The maximum injection pressure of the pilot dose practically does not depend on the speed mode and lies within 13.5-15 MPa. Since the amount of the pilot dose is not adjustable, it does not depend on the movement of the high-pressure fuel pump rail and is 2 mm3/cycle at a rotation frequency of 450 min-1, 6 mm3/cycle at a rotation frequency of 550 min-1 and 9 mm3/cycle at a rotation frequency of 650 min-1.