Premixing apparatus

a technology of pre-mixing apparatus and pre-mixing liquid, which is applied in the direction of burners, fuel supply regulation, combustion types, etc., can solve problems such as failure of combustion, and achieve the effects of reducing the rotational speed of the fan, ensuring wind resistance performance, and reducing the minimum amount of combustion

Inactive Publication Date: 2021-02-11
RINNAI CORP
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  • Summary
  • Abstract
  • Description
  • Claims
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AI Technical Summary

Benefits of technology

[0006]According to this invention, even if the calorific value of the fuel gas may fluctuate, the excess air ratio of the air-fuel mixture can be kept constant by the control of the flow control valve, thereby preventing the combustion failure from taking place.
[0007]By the way, in order not to cause exhausting failure to take place due to entry of wind into an exhaust tube, i.e., in order to secure wind resistance performance, the lower-limit rotational speed of the fan will have to be set relatively high. However, this arrangement brings about also a relatively higher minimum combustion amount that is the combustion amount obtainable at the time when the rotational speed of the fan is reduced to the lower-limit rotational speed. As a result, a turndown ratio will become small.
[0008]As a solution, the premixing apparatus according to this invention preferably further comprises a swing valve provided in an air-fuel mixture supply passage between the burner and the fan. The swing valve is capable of swinging from a closed posture of being hung down with an upper end shaft serving as a fulcrum to a bottom-up open side against a self-weight thereof. According to this arrangement, when the rotational speed of the fan is made to exceed a predetermined rotational speed, the swing valve may be swung to the bottom-up open side, into a fully-opened state against the self-weight of the swing valve due to a wind pressure from the fan. On the other hand, if the rotational speed of the fan is below the predetermined rotational speed, the swing valve will gradually be swung downward from the fully-opened state. As a result, accompanied by the lowering of the rotational speed of the fan, the passage area of the air-fuel mixture supply passage will gradually be reduced. Accordingly, even if the lower-limit rotational speed is relatively high, the supply amount of the air-fuel mixture becomes rel...

Problems solved by technology

Therefore, accompanied by the fluctuation of the calorific value of the fuel gas, the exces...

Method used

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first embodiment

[0025]Even in case the kind of gas of the fuel gas is changed, the excess air ratio of the air-fuel mixture can be made to the appropriate value by the control of the flow control valve 74. It is to be noted however that, in order to cope with the change to a gas with a largely different calorific value, it becomes necessary to largely change the flow resistance in a portion, on a downstream side of the zero governor 73, of the gas supply passage 7. In the arrangement of the first embodiment, it becomes necessary to make relatively wider the range of opening degree change of the flow control valve 74. For that purpose, the amount of change in opening degree per unit operation amount of the flow control valve 74 will be obliged to be made larger. As a consequence, the allowable error in the operation amount becomes slight, thereby deteriorating the controllability of the flow control valve 74.

second embodiment

[0026]On the other hand, even if the change width of opening degree of the flow control valve 74 is not so large, the flow resistance in a portion, on the downstream side of the zero governor 73, of the gas supply passage 7 can be varied over a wide range: by the opening degree change in the state in which the fuel gas does not flow through the bypass passage 75 as a result of closing the on-off valve 76; and by the opening degree change of the flow control valve 74 in a state in which the fuel gas flows through the bypass passage 75 as a result of opening the on-off valve 76. Therefore, the deterioration in the controllability of the flow control valve 74 due to enlargement of the range in opening degree change can be avoided.

[0027]Descriptions have so far been made of the embodiments of this invention with reference to the figures, but this invention shall not be limited to the above. For example, in the above-mentioned embodiments, in order to switch the capacity, the flow resis...

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Abstract

A premixing apparatus for mixing air with a fuel gas in order to supply a burner with an air-fuel mixture through a fan, wherein a downstream end of a gas supply passage is connected to a gas suction part disposed in a portion, on an upstream side of the fan, of an air supply passage. The gas supply passage has interposed therein a zero governor for adjusting a secondary gas pressure to an atmospheric pressure. Even if the calorific value of the fuel gas may fluctuate, excess air ratio of the air-fuel mixture is arranged to be maintained at a constant value. The premixing apparatus is provided with: an excess air ratio detection device for detecting an excess air ratio of the air-fuel mixture; and a flow control valve interposed in a portion, on a downstream side of the zero governor, of the gas supply passage. The flow control valve is controlled such that the excess air ratio of the air-fuel mixture detected by the excess air ratio detection device becomes constant.

Description

TECHNICAL FIELD[0001]The present invention relates to a premixing apparatus for mixing air with a fuel gas in order to supply a burner with an air-fuel mixture through a fan.BACKGROUND ART[0002]Conventionally, as this kind of premixing apparatus, there is known one, e.g. in JP-A-2018-179447, in which a downstream end of a gas supply passage is connected to a gas suction part disposed in a portion, on an upstream side of the fan, of an air supply passage. The gas supply passage has interposed therein a zero governor for adjusting a secondary gas pressure to an atmospheric pressure. It is to be noted here that the supply amount of the fuel gas varies with a differential pressure between the atmospheric pressure which is the secondary gas pressure and a negative pressure inside the air supply passage. Since the negative pressure inside the air supply passage varies with the rotational speed of the fan, the supply amount of the fuel gas varies with the rotational speed of the fan, i.e.,...

Claims

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Application Information

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IPC IPC(8): F23D14/02F23D14/62F23D14/60
CPCF23D14/02F23D2200/00F23D14/60F23D14/62F23N1/022F23N5/123
Inventor NORITAKE, KATSUYATAKEUCHI, MASARUYOSHIMURA, KIMIHIRO
Owner RINNAI CORP
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