The Experiment Investigation On Characteristics Of Ignition And Combustion For Diesel Spray Wall Impingement

The phenomenon of diesel spray impingement always causes the deposition of fuel on the chamber.This phenomenon causes the mixture near to the wall too thick,which not only decreases the fuel economy of diesel engines,but also aggravates the emission of CO and HC.So it is significative to study the ignition and combustion characteristics of diesel spray impingement for improving the performance of diesel engines.The experiment was performed in the system of constant volume combustion chamber,a high speed camera was used to capture the images of ignition and combustion of diesel spray impingement in this paper.Firstly,the effects of injection pressure on the characteristics of ignition and combustion for diesel spray impingement were investigated in constant injection mass condition.The variation laws of the delay time of ignition,the position of ignition,the flame area and the spatial integrated natural luminosity(SINL)were obtained for different injection pressures.The results were showed as following.With the injection pressure increasing,the delay time of ignition increased,the distance of the ignition increased in the horizontal and vertical direction,the period of combustion shorted,the mean increase rate of the flame area and the SINL increased in the quickly increase stage and the slowly increase stage,the mean decline rate increased in the quickly decline stage and slowly decline stage,the time reaching the maximum of the flame area and the SINL shorted,and the maximum of the flame area and the SINL was invariant for different injection pressures.Then,the effects of nozzle hole diameter on the characteristics of ignition and combustion for diesel spray impingement were investigated in constant injection mass condition.The variation laws of the delay time of ignition,the position of ignition,the flame area and the spatial integrated natural luminosity(SINL)were obtained for different nozzle hole diameters.The results were showed as following.With the nozzle hole diameter increasing,the delay time of ignition increased,the distance of the ignition increased in the vertical and horizontal direction,the duration of combustion shorted,the mean increase rate of the flame area increased in the quickly increase stage and the slowly increase stage,the mean decline rate decreased in the quickly decline stage,the time reaching the maximum shorted,and the maximum was invariant for different nozzle hole diameters.Finally,the ignition boundary was studied for different injection pressures and different injection masses under the condition of constant nozzle hole diameter.The results were showed as following.There were a minimal ignition injection mass for white flame and blue flame respectively for every injection pressure.With the injection pressure increasing,the two minimal injection masses all increased,the delay time of ignition increased on the white flame ignition boundary.When the injection mass was higher than the corresponding minimal ignition injection mass of white flame,the delay time of ignition was invariant for different injection masses..