The Study And Design Of The Vaporizer Heated By Exhaust For The Gas Supply Systerm Of LNG Vehicle

With the rapid development of economy and society in our country, the automobile industry is also rapidly forward, when the total of car continue to increase in China, the problems of environment and energy are also prominent at the same time. Developing the new energy and finding the replaceable fuel which is abundant and clean for cars have become the urgently problems to solve in today’s automobile industry, in China, the main fuel is coal, as the problems of weather increased in recent years, the development of natural gas plays an important role in automobile industry, government has paid much attention to the LNG(liquefied natural gas) vehicle which has so many advantages, for example, the high thermal efficiency of burning, the clean emission, easy storage and transportation, the long range and so on.For LNG vehicle, the LNG heated by engine cooling water and becomes into natural gas which is used by engine, the quantity of heat of engine cooling water will be not enough when the vehicle is started in the low temperature environment, and the vehicle will be hard to start, the supply pipe of natural gas will freeze; In order to solve the problems above, this passage puts forward a way of vaporizer design by using the heat of exhaust, it is that the LNG is heated by the high quantity of heat of exhaust and is used by the engine then.For the innovative design of the vaporizer, firstly, the control range of natural gas temperature which is out of the vaporizer is studied, the paper points out that the volume of natural gas in the mixed gas can’t be ignored in the natural gas engine, when the temperature of natural gas is too high or too low, the natural gas will exchange the heat with the air which will mix with the natural gas and the temperature of mixed gas will be changed, and the temperature of mixed gas directly affects the combustion in the cylinder, through controlling the temperature of natural gas which is out of the vaporizer in the range of the temperature which is small fluctuations around the temperature of the air that will mix with the natural gas to control the temperature of mixed gas. Secondly, when choosing the temperature and position of the exhaust, the temperature of exhaust can be calculated by the equation of the heat balance, because of the changing of the exhaust temperature which is from the manifold to the tail pipe, and the position of exhaust that will be used can be gained by numerical simulation. Thirdly, after the determining of the temperature of the natural gas which is out of the vaporizer and knowing the temperature and position of the exhaust which will be used, the vaporizer will be designed, in the process of the design, the difference of temperature, the coefficient of heat transfer and the area of heat transfer and other parameters will be determined by the equation of heat transfer.Through this research, the paper provides a new idea for the determination of the temperature of the natural gas which is out of the vaporizer for the LNG vehicle, the numerical simulation of the exhaust system and the calculation of parameters in the process of the design.