| 摘要 |
PURPOSE:To enable to set the air-fuel ratio at a low value, by setting the pressure of combustion air at a value higher than that of the pressure of fuel gas. CONSTITUTION:Flow restricting sections 1, 2 are provided respectively in a fuel gas passage and a combustion air passage, and they are joined together on the downstream side of the flow restricting sections 1, 2. Further, a gas pressure control valve 3 for controlling the gas pressure and a combustion-air supply means 4 for supplying combustion air are disposed respectively on the upstream side of the flow restricting sections 1, 2. Providing that the pressure in the fuel gas passage at the portion thereof between the gas pressure control valve 3 and the flow restricting section 1 is Pg and the pressure in the combustion air passage at the portion thereof between the combustion-air supply means 4 and the flow restricting section 2 is Pa, the differential pressure of Pg and Pa is detected by a differential-pressure detector 7 and the air-fuel ratio is controlled basically to satisfy the following equation, Pa=Pg+E(S>0). With such an arrangement, the value of E becomes relatively large when Pa, Pg are lowered in a low combustion region, that is, the air-fuel ratio is increased since the air feeding pressure becomes relatively high, so that it is enabled to keep good combustion and to reduce the exhaust loss. |
