| 摘要 |
<p>PURPOSE:To reduce discomfortable and offensive sound of combustion and to lower the noise level by emitting the combustion sound from the rearward of the top portion of a combustion cylinder and reflecting the combustion sounds to the upstream side by the ceiling plate of a blast duct. CONSTITUTION:Air is blasted within a blast duct 18 by means of a blower 7, and hot air heat-exchanged in a combustion cylinder 6 is exhausted from a blow-off port 8. The ceiling plate 15 of the blast duct is inclined downwardly from the upstream side in the direction of the upper side of a radiation window 11 and the rear part of the top portion of the combustion cylinder 6 is constituted of a porous plate 17. When the top portion of the combustion cylinder is observed from the combustion portion 5 from the acoustic point of view, the acoustic impedance at a rear porous plate 17 is smaller than that of the passage of the inclined catalyst purifying filter 10. The noise generated at the combustion part 5 is emitted mostly from the porous late. The sound emitted from the porous plate is reflected to the upstream side of the blast duct by means of an inclined plate 15. Thus, the sound is not reflected for several times within the blast duct 18, and it is possible to suppress the filling of the sound and the occurrence of a standing wave resonance. As a result, discomfortable and offensive sound to the ear can be removed and the noise can be lowered.</p> |
