Improving the performance of tractor diesel engines by optimizing the fuel supply characteristics

Diesel engines to the greatest extent satisfy the tendencies that take place in the engine building: increased power indicators, reduced specific fuel consumption and toxicity of exhaust gases. It is possible to realize the indicated advantages of diesel engines only if the parameters that characterize the fuel supply are ensured and maintained. The nature of the fuel supply predetermines the indicators that characterize the quality of the workflow in a diesel engine. As you know, during the operation of a diesel engine, there are significant differences between the real characteristics of the fuel supply to the optimum. These differences arise due to the fact that the technical condition of the elements of the high pressure fuel system (HPF) changes. Establishing the optimal parameters that characterize the fuel supply during the operation of the fuel equipment (FE) is a rather difficult task, which is caused by the interconnectedness and interdependence of these parameters. It is especially necessary to take into account that while optimizing some fuel supply parameters, others often deteriorate. In order to ensure a high-quality fuel combustion process, the fuel system of a diesel engine is faced with the task of ensuring guaranteed injection of a metered cyclic fuel supply (CFS), taking into account the specified phases and injection characteristics, which will have a beneficial effect on the fuel combustion process in any operating modes of the diesel engine. Thus, with a change in the technical characteristics of the HPF during operation, the characteristics of the injection also change. When studying the influence of the HPF parameters on the fuel supply characteristics, the change in the injection characteristics is often not taken into account, which is explained by the complexity and laboriousness of these studies. Considering the above, the optimization of the characteristics of diesel engines fuel supply is an urgent problem.


Introduction
The process of optimizing the parameters of fuel supply and indicators of the working process of diesel engines is carried out by multifactorial mathematical modelling [1][2][3][4].
During optimization, the technique of multifactor mathematical modelling based on the method of nodal points was used. Polynomial models allow, in a variant calculation, to set the CFS at a given level, that is, to simulate the process of operation of the HPF. A multivariate mathematical model taking into account the nodal point method can be written as follows: where Y is the fuel supply parameter; 0 Y is parameter of fuel supply at the nodal point; n is the number of factors; ( ) i X f is one-factor dependence.

Research results
The hydrodynamic calculation of the fuel supply made it possible to single out the factors that determine the characteristics of the injection process and the quality indicators that characterize the course of the working process in a diesel engine: cycle feed ( It is known that the injection characteristic ( XB ) and the quality of fuel atomization are determined by the cycle supply, pressure and duration of fuel injection [5][6][7][8][9][10][11]. Figure 1 shows a diagram of a directed graph that characterizes the developed multivariate mathematical models that take into account the influence of the selected factors. Based on expression (1) and the adopted directed graph, we get: functions of factors influencing the value of the CFS, duration, pressure and lag angle of fuel injection.
The approximation of one-factor dependences of the parameters of the fuel supply on the indicators that determine the technical condition of the HPF was made using the following equations: By jointly solving equations (6-9) and (2-5), the following mathematical models were obtained (for UTN-5): An increase in the clearance along the unloading shoulder of the discharge valve from 4.0 to 10 microns leads to an increase in the CFS by 3.0 mm 3 / cycle (by 4%). However, an increase in CFS from an increase k is not equivalent to an increase in CFS from an increase P P f  due to an increase in injection pressure by 11.1% (in the first case) and a decrease by 8.18% (in the second case). Accordingly, there is a decrease in the injection duration P  by 1.8... 0 (by 20%) and by 1... 0 (by 9%).
When selecting injectors and fuel lines according to such a criterion as throughput, these circumstances are usually not taken into account, as a result of which there is unevenness in P  and B P with the identity of the values of the CFS for the HPF sections and the FE kits. Ultimately, the workflow is not identical in different cylinders of a diesel engine.
Using the obtained multifactorial mathematical models of the fuel supply parameters (10 ... 13), it is possible to substantiate the parameters of bench injectors and the fuel-conducting system, to establish the values of the HPF elements, which will provide a uniform CFS taking into account As a result of optimization, the objective functions are obtained in the form of a regression equation: where Y is the indicator under study;  For various performance indicators of a diesel engine, equations (14) will be written as: The indicator coefficient of performance of a diesel engine i  is an integral criterion of the efficiency of heat release, which depends on the parameters of fuel supply. Taking this into account, this indicator is adopted as an optimization criterion. Using

Conclusion
Using the obtained multifactor mathematical models of fuel supply parameters, it is possible to substantiate the parameters of bench injectors and fuel lines, to establish the values of the HPF elements, which will provide a uniform CFS taking into account The research results show that fuel delivery parameters are mainly determined by the technical condition of the injector nozzle and delivery valve, as well as injection pressure and cyclic fuel supply.