| Natural gas is proven to have large reservation, cheap price, low carbon hydrogen ratio and good emission performance. All what it would be helping it becoming an ideal alternative fuel engine at present;the injection of natural gas in the field of engine is by gas. And there are problems for the low inflation, the complicated structure and the high possibility of detonation. LNG liquefied injection not only can solve the problem very well, but also is conducive to lean burn, and release a large number of cold energy in combustion process, It can significantly improve the emission performance of the engine, but it is still in the stage of theoretical research. The corresponding LNG fuel supply system is a difficult point in process of theory realization. In the existing cylinder liquid direct injection fuel supply method, high pressure common rail system has its incomparable advantages of high injection pressure and flexible control strategy, which would enhance the performance of the engine. High pressure common rail system appears have large rail pressure fluctuations, in the application of multi-cylinder engine. How to reduce the pressure fluctuation is one of the most important developments of the high pressure common rail system at present.This topic is treat reduce rail pressure fluctuations as the goal for optimize a LNG electric control common rail fuel supply system.Modify the existing LNG fuel supply system, which contains high pressure pump, common rail pipe and injector in the fuel supply system,according to the characteristics of AMESim software. Analysis the influence of the key parameters of the high pressure pump on the fuel supply characteristics and the influence of the pressure in the common rail under the rated condition. Analysis common rail pipe pressure variation and corresponding key parameters by contract. Optimize high pressure pump according to these parameters and the interaction of the key components of pump. And try to provide a theoretical basis for the real LNG liquefied direct injection fuel supply system design. Design the electronic control unit(ECU) for the diesel /LNG dual fuel engine.Determine the LNG diesel dual fuel engine fuel injection system ECU control strategy, and do the simulation for control strategy and analysis different control parameters influence on the rail pressure, improve the high pressure common rail system control precision.This paper showed the following conclusions:First of all, the influence of oil phase fluctuation of rail pressure is more obvious on the rail pressure's phase movement. It turn out to be that when the starting position of cam phase is set as 5,65 degrees, the rail pressure fluctuation variation is smaller than other degree, but the starting position of cam phase has little influence to the fuel supply characteristics;Second, piston lift and diameter do a lot for rail pressure fluctuation and the fuel supply characteristics: When the piston lift and diameter is set to be a bigger one, the rail pressure fluctuation and fuel supply characteristics would be enhanced rapidly.Third, the outlet valve should be calculated to be appropriate one or the rail pressure variation would be amplified. Rail pressure establishment time is longer, when the outlet valve structure is not a appropriate one. Outlet hole size should be selected at an appropriate size.If it is too large or too small, the rail pressure fluctuation variation will be increased greatly. The outlet valve structure would also affect pumping ability. The outlet valve body structure parameters for the fuel supply characteristics influence is more obvious than the oil phase, the plunger is less than lift and plunger diameter.Fourth, the larger duty ratio, the rail pressure completion time is shorter, and the rail pressure fluctuations will become more evident;Fifth, when the control of the pulse frequency is too low, the rail pressure fluctuation will be established quite large, but the impact of rail pressure on the establishment time would be little. |
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