Simulation Research On A Fuel Supply System Of LNG Engine

With the development of the economy and society, the vehicle population is also increasing rapidly. Automobiles aggravate the global environmental pollution and energy crisis while they bring convenience. Finding some clean and abundant alternative fuels for car has become an urgent problem needed to be addressed for institutions and researchers at all levels. On the promise of a great deal of coal and oil are consumed, the natural gas is favored by more and more people. The liquefied natural gas (LNG) vehicles possess high thermal efficiency and excellent emission performance, which natural gas also has. Additionally, the energy density of storage and the miles of the LNG vehicles are higher than CNG vehicles, but the size is smaller and the weight is lower when LNG is in the state of storage and transportation. Many LNG projects constructed around our country vigorously play a positive role in the promotion of LNG vehicle.The prospect of LNG vehicle is great. Most of natural gas engines are developed into a sort of oil-gas dual fuel engine though installing a natural gas supply system on the original engine. This will lead the compression ratio and the charging efficiency to decrease, the power of engine reduced at the same time. The Paper determined to adopt the Carburetor plus the Megajector and Mixer electronic to control LNG single fuel supply system as the researching project though comparison and analysis, which can control the intake accuracy effectively and ensure the uniformity of combustible mixture. It makes some modeling and simulation analysis on the LNG engine fuel supply system and cooling system by using AMESim software. It puts forward some improvements and optimization matching schemes to the fuel supply system and cooling system.The Paper imports the LNG properties data file which needed in simulation into model by using the characteristics of the software. According to the principle and the structure of the various components in fuel supply system, the carburetor was modeled firstly for it's an important component in the system, then the fuel supply system model was build based on it. According to the principle and construct of the original engine cooling system, The Paper builds a model of the cooling system separately, then forms a uniting simulation model by adding the carburetor model after the debug and verify of cooling system model was completed. Firstly, calculate the influence of coolant flow and ambient temperature on vaporization effect and intake temperature and pressure when the LNG engine in the cold start; Secondly, simulate the influence of coolant flow and ambient temperature when the engine at maximum power point. Finally, analyze the influence of fuel supply system on the original engine cooling system.The coolant flow should be higher than 6L/min when the LNG engine in cold start (ambient temperature is minus 35 degree centigrade). The car should be warmed-up in the cold start to prevent frost phenomena on Carburetor and ensure idle is stable. The suitable coolant flow LNG Carburetor should between 15L/min and 25L/min when the engine at maximum power point and the export coolant temperature degree centigrade. There may cause the intake temperature is too high when the temperature is higher than 100 degree centigrade. At this point, we should reduce the temperature of engine bonnet outlet to below 100 degree centigrade through matching the cooling system and carburetor as soon as possible. Although the original cooling system of has a good cooling performance, there will Lead to over-cooling problem, we should re-match the cooling parameters of radiator, while the coolant flow through the carburetor is too large and the natural is Over-heating, so it should be adjusted properly.