| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lightweight muffler having a simple structure at low cost by introducing exhaust gas generated in a combustion chamber before being discharged from an exhaust top and passing it through a spiral muffling passage in the muffler thereby elongating the muffling passage of the muffler sufficiently in compact shape. SOLUTION: Exhaust gas generated in a combustion chamber 12 passes through a heat exchanger 13 and enters a muffler 20 before being discharged from an exhaust top 17 to the outside. The muffler 20 has circular horizontal cross-section and an outer case 21 is constructed of a case top plate 21a, a case bottom plate 21b and a case outer tube 21c. On the inside thereof, an inner space for forming a muffling passage is defined by a passage top plate 23, a passage bottom plate 24 and a passage outer tube 25 through an acoustic material 22. A muffling passage is formed by placing a spirally wound baffle plate 26 in the inner space while bonding to the passage top plate 23 and the passage bottom plate 24.
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