| Methanol as a "carbon neutral" fuel is one of the most promising alternative petroleum energy for internal combustion engine.Because its physical and chemical properties are obviously different from those of gasoline and diesel fuel,its spray impinging behavior is also different from that of conventional fuel.Therefore,understanding the spray impinging characteristics and its influence on the formation process of spray mixture can provide a theoretical basis for optimizing the organization combustion of methanol engine.Based on the observation of the development of the internal spray of the constant volume combustion vessel and the impingement test,the conclusions are as follows: the greater the environmental pressure,the slower the development of the radial size of the wall impact spray;In a certain range of fuel temperature,the higher the fuel temperature,the stronger the evaporation effect of the liquid film on the wall surface,and the slower the development of the spray on the radial direction.The farther the distance from the wall to the nozzle,the slower the radial development of the wall-bump spray.The larger the wall incline Angle,the faster the spray development along the incline direction.In a certain range of wall temperature,the radial expansion velocity of the spray increases with the increase of wall temperature,but the radial development of the spray will be limited when the wall temperature reaches or exceeds the Leiden Frost effect temperature of the fuel.The existence of oil film on the wall will restrain the radial expansion of the spray.In order to explore the factors affecting the evaporation of the liquid film on the wall,the evaporation process of different liquid films in the constant volume projectile was simulated and analyzed.The results showed that: for the liquid film with the same thickness,the larger the liquid film area,the faster the evaporation rate of methanol.The larger the thickness of the liquid film,the rate of methanol evaporation is slower.For the same liquid film area and liquid film thickness,the longer the boundary circumference,the rate of methanol evaporation is slower.For the same liquid film area,liquid film thickness and liquid film boundary circumference,the faster the air flow is,the faster the methanol evaporation will be.In this paper,the methanol spray process in the engine cylinder is simulated.The simulation result shows that the spray expansion angle,the number of nozzle holes and the injection vein width all affect the rate of atomization evaporation in the methanol spray space and the liquid film evaporation on the wall.On the premise of ensuring a higher methanol evaporation rate and a smaller mean diameter of the sort,to change the matching relationship among the three factors can effectively reduce the quality of the liquid film in the cylinder.Simulated and analyzed the spray mixing process in the cylinder under the condition of compound injection.We can conclude that the reasonable compound injection strategy can further reduce the mass of the liquid film in the cylinder at the ignition time. |
