Effect of swirl level on particulate emission of a diesel engine

The effect of intake swirl level inside the cylinder on particulate emission of an automotive diesel engine was experimentally studied using an air injection variable swirl intake system designed by ourselves to change swirl strength. The test results showed that it is an effective method to reduce particulate emission of DI diesel engine by means of changing swirl level in the cylinder. The effect of swirl strength on particulate emission at medium speed operating condition was not significant because the squish and expansion swirl generated by piston movement could meet the needs of fuel combustion. However, in the case of lower speed and heavier load operating conditions, because the swirl strength generated by helical intake passage was too weak, particulate emission could be decreased when swirl level was increased to some extent. The decrease of dry soot led to the decrease of particulate emission. As to higher speed operating conditions, particulate emission could be decreased if a too strong swirl level generated by helical intake passage was decreased to some extent. The particulate emission decrease may be induced by the decrease of soluble organic fraction emission.