| 摘要 |
PURPOSE:To muffle the exhaust noise and to cool the surroundings of an exhaust tube reliably, by forming a water jacket surrounding the entire circumference of the exhaust tube between a propulsion casing and the exhaust tube and forming an exhaust gas expansion chamber in front of the exhaust tube arranging position in the propulsion casing. CONSTITUTION:A water jacket 43 and an exhaust gas expansion chamber 46 can be formed without providing a conventional tubular body in a propulsion casing 18. Since the water jacket 43 is formed around an exhaust tube 37 while contacting directly therewith, cooling effect for the exhaust tube 37 is improved thereby the temperature of the exhaust tube 37 and the exhaust gas flowing out through the exhaust tube 37 can be lowered sufficiently. Consequently, overheating of the propulsion casing due to the heat of exhaust gas can be prevented sufficiently. In other word, exhaust gas noise can be muffled through simple structure and the surroundings of the exhaust tube 37 can be cooled reliably. |
