Effect of Two-Stage Fuel Combustion in Diesel Cylinder on Its Indicator Indicators

Abstract

The use of two-stage fuel injection into the diesel cylinder is an effective means of reducing the noise of its operation and reducing emissions of nitrogen oxides with exhaust gases. In this work, a computational-experimental study is based on a method in which part of the experimental indicator is replaced by the results of its numerical synthesis, performed using mathematical modeling of processes in the engine cylinder. The research was carried out on an experimental single-cylinder engine Ch8.8/8.2, equipped with a high-pressure fuel supply system. The mathematical model of working processes in the cylinder of the experimental engine is developed and identified. When studying the effect of two-stage combustion on the indicator process of the engine, the parameters that determine the law of fuel combustion, i.e. the angles of the beginning of the injection of the main and pilot portions of fuel changed.
 It is shown that the value of the indicator efficiency of the cycle is almost independent of the introduction and advancement at the angle of rotation of the crankshaft of the moment of pre-combustion at a constant ignition moment of the main portion of the fuel. However, reducing the starting angle of the pilot fuel injection leads to an increase in the maximum pressure of the cycle pz and the maximum rate of pressure rise, as a consequence of increasing engine noise.
 It is proved that it is possible to start the ignition of the main portion of the fuel without a significant decrease in the average indicator pressure and with a decrease in the values of pz and dr/dφmax when creating pre-combustion of fuel by 20 degrees turning the crankshaft to the main. The rational angle of advance of the injection of the pilot portion of fuel is 10 ... 12 deg. turning the crankshaft to inject the main portion. The obtained results show that the proposed measures - the introduction of pre-combustion 10… 25% of the cycle feed - can reduce the noise level of the engine while maintaining the level of the average indicator pressure and reduce the maximum cycle pressure.