| 摘要 |
PURPOSE:To lower a noise level when burning is weak, by expanding a secondary-air passage in the middle thereof, and by providing a partition plate having a plurality of small holes also in the middle of said passage. CONSTITUTION:A secondary-air passage 12 is expanded in the middle thereof, and a partition plate 13 having a number of small holes 13a is provided also in the middle of said passage. By this constitution, the quantity of air flowing through the secondary-air passage 12 is turned to be larger in weak burning than in strong burning, while the speed of airflow is decreased since the secondary-air passage 12 is expanded in the middle thereof. Moreover, the partition plate 13 has a noise insulation effect, and in addition, the flow of air is turned from a turbulent into a regulated one by the small holes 13a of the partition plate 13. Thus, the noise due to the turbulent flow is eliminated. |
