| 摘要 |
PURPOSE:To prevent a standing wave resonance from being generated and to reduce a noise level by downwardly inclining a ceiling plate and a partition plate of a supply duct toward the downstream and providing a catalyst purifying filter so that an acoustic focus is set substantially at the center of a heat resisting sound absorption plate stuck to the partition plate. CONSTITUTION:Between a ceiling plate 14 and the top portion of a combustion cylinder, a partion plate 21 stuck on the side of the combustion cylinder 19 with a heat resisting sound absorption plate 25, for dividing a supply passage into two parts, is provided, and the ceiling plate 14 and the partition plate 21 are inclined downward toward the downstream direction. Further, a catalyst purifying filter 22 having an acoustic lens structure provided with an air passage 23 in which the acoustic focus thereof is set substantially at the center of the heat-resisting sound absorption plate 25, is provided on a section 24 formed by cutting the outlet side of the combustion cylinder 19 in a slant section with respect to the central axis of the combustion cylinder 19. By the above construction, a noise generated at a combustion part 18 is radiated from the catalyst purifying filter 22 to the direction of the ceiling plate 14 and the partition plate 21, and the noise is reflected to the upstream side on the ceiling plate 14 and is absorbed by the heat-resisting sound absorbing plate 25 at the pertition plate 21. As a result, it is possible to remove the filling of sound and to prevent the generation of the standing wave to reduce the noise.
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