The reduction rate in soot size due to orifice size was suppressed by the decrease in ignition delay due to reduction of orifice size.
(2) The number of soot particles increases almost with the amount of fuel injected as the primary factor, and it decreases almost linearly with an increase in the excess air ratio of the burned zone, the secondary and important factor with respect to the orifice size effect. The number of soot particles decreased when the orifice size was decreased because of the increase in the excess air ratio of the burned zone.
(3) The exhaust smoke density is calculated by the product of the size and the number of soot particles. The decrease in smoke due to orifice size reduction was based on both decreases in size and number of soot particles.
(4) The excessive reduction of orifice size resulted in the increase in smoke. This is due to increase in the number of soot particles based on the increase in fuel consumption resulting from the marked increase in injection duration if the fuel injection pressure is not increased in proportion to the total orifice area.
ACKNOWLEDGMENTS
The authors express their gratitude to Yazaki Memorial Foundation For Science and Technology for the financial support, also to Mitsubishi Motor Corp., and ZEXEL Corp. for their supports on the experimental apparatus. And the authors wish to thank to Mr. Ishibashi, K., Hino Motors Corp., and Mr. Imaji, H,. Daihatsu Diesel Co. Ltd., who were formerly students at the graduate school of Nagasaki University, and the undergraduate students in Energy System Laboratory, Nagasaki University for securing and analyzing the experimental data.
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