Research of influence of operational factors on parameters fuel delivery accumulator system CR engines RT-FLEX
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Abstract
The results of a computational study of the influence of operational factors on the fuel supply process by the accumulator system CR of RT-flex engines are presented. In the model used in the study of fuel supply in the accumulator system processes that occur in all its essential elements are described. As an accumulator, a constant pressure source is considered. The most detailed analysis is the operation of the injection control unit that determines the processes in the high-pressure system. Carefully presented nozzles, the elements of which are fully consistent with the real design. A change in the basic characteristics of injection with variable values of the temperature of heating the fuel, its viscosity, pressure in the accumulator and the pressure of the nozzle needle lift is considered. The most significant effect is the viscosity and pressure in the accumulator. An increase in viscosity (lowering the heating temperature) leads to a significant decrease in the cyclic supply of fuel and a decrease in the stroke of the metering piston with constant fuel supply phases. The cycle delivery increases with temperature from 500 C to 90-1100 C from 0,013 to 0,022 kg – 1,69 times. Obviously, the determining factor in this dependence is the movement metering piston injection control unit. This indicator changes in a close way, increasing in the same range from 7.4 to 10.5-10.8 mm. Additional information about the movement of the QP is the speed of its movement. In the direct (working, injection) stroke, it increases with increasing temperature in the above range from 0,135 to 0,244 m / s. As for the fuel pressure in the nozzle, then the influence of temperature is small. It decreases from 610 to 600 bar − less than 2 % (in the ratio of 1,016). This pattern indicates the decisive influence of the hydraulic resistance of the elements of the high pressure path on the pressure in the nozzle. In a similar way, the injection parameters change with decreasing pressure in the accumulator. One of the operational parameters of the fuel supply system is the liftingpressure of the nozzle, which depends on the force from the spring. To assess the influence of the pressure of the nozzle lift, the injection process was simulated at various spring tightening pressures. The range of variation of was 300-450 bar with a nominal value of 375 bar. No noticeable effect was on injection characteristics. The change in the cyclic delivery does not go beyond 3,2 %; the difference in the path of the QP for the boundaries of the range is 2,2 %, and the velocity of the QP remains within 1,8 %. The pressure in the nozzle channel remains unchanged.
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