Abstract
In order to study influence of swirl intensity on particulate emissions from a diesel engine, a variable swirl intake system by means of injecting compressed air into the helical intake passage (AIVSIS) was developed. Steady flow rig test showed that AIVSIS can change the swirl level in the cylinder effectively, and the relationship between swirl ratio and air jet pressure was determined by calibration test at several engine speeds. Effect of swirl intensity on air charge and particulate and their soluble organic fraction and dry soot fraction from an automotive D.I. diesel engine were studied experimentally. Test results showed that AIVSIS only changes swirl intensity without any effect on air charge into cylinder, and influence of swirl intensity on particulate emission is significant. For lower engine speed and heavier load operating conditions, the particulate emissions can be decreased significantly by enhancing air swirl generated by helical intake passage, and the swirl variation only decreases the dry soot fraction of particulate. For rated engine speed operating conditions, air swirl generated by helical intake passage seems too strong, particulate emissions can be decreased significantly by decreasing swirl intensity in the cylinder. The decrease of soluble organic fraction of particulate was more significant than that of dry soot. The variation of swirl intensity hardly affects particulate emissions from diesel engine at medium speed operating conditions.