JP-7856896-B2 - Premixing device and combustion apparatus equipped therewith

JP7856896B2JP 7856896 B2JP7856896 B2JP 7856896B2JP-7856896-B2

Inventors

小川恭平

Assignees

株式会社ノーリツ

Dates

Publication Date: 20260512
Application Date: 20220902

Claims (7)

A premixing channel is provided for supplying air from the outside and mixing this air with fuel gas to generate a fuel-air mixture. This premixing channel is divided into first and second channels arranged in a direction intersecting the airflow direction by a partition wall, First and second fuel gas outlets capable of discharging fuel gas into the first and second passages by utilizing the negative pressure generated by the airflow in the first and second passages, A premixing device equipped with, A first blade portion is provided within the first flow path, and the first fuel gas outlet is provided facing downstream in the direction of the airflow, A flapper is provided, which is located downstream of the first blade portion in the airflow direction of the first flow path, is pivotable to open and close both the first flow path and the first fuel gas outlet, and whose opening degree changes according to the airflow rate such that the opening degree is smaller when the airflow rate of the premixing flow path is low than when it is high. A pair of fin portions are provided on the flapper so as to sandwich the first fuel gas outlet and the first blade portion in a direction intersecting the airflow direction, and the fin portions form a gap between them that allows air to pass through. A premixing apparatus characterized by further comprising the following features.
A premixing apparatus according to claim 1, A premixing device in which, when viewed in the direction of the pivot center of the flapper, at least the region of each fin portion closer to the flapper has a tip that is arc-shaped with respect to the pivot center, and the radius thereof is greater than or equal to the distance from the pivot center to the first fuel gas outlet.
A premixing apparatus according to claim 1, A premixing device in which, when the flapper is fully open, each fin portion is located downstream of the first blade portion in the direction of airflow and is not present on either side of the first blade portion.
A premixing apparatus according to claim 1, A protruding step portion is provided on the inner surface of the peripheral wall of the first flow path and partially protrudes closer to the center of the first flow path than other general parts of the inner surface of the peripheral wall, A support member is attached to this protruding step and positioned within the first flow path, and supports the flapper so that it can swing; A premixing device that is further equipped with this feature.
A premixing apparatus according to claim 1, A premixing channel forming member that forms the premixing channel, A second blade is provided in the second flow path such that one end is connected to the peripheral wall of the premixing flow path forming member and the other end is connected to the first blade via the partition wall, and the second fuel gas outlet is provided facing downstream in the direction of airflow, A fuel gas receiving portion is provided on the peripheral wall portion of the premixing channel forming member and receives fuel gas from the outside, A second fuel gas passage is provided within the second blade portion so that a portion of the fuel gas supplied to this fuel gas receiving portion can be guided to the second fuel gas outlet, A first fuel gas passage is provided extending from within the second blade portion into the first blade portion so that it can guide another portion of the fuel gas supplied to the fuel gas receiving portion to the first fuel gas outlet, A premixing device that is further equipped with this feature.
A premixing apparatus according to claim 5, A premixing device wherein the second blade portion has a greater thickness in the airflow direction than the first blade portion, and within the second blade portion, the first and second fuel gas passages are arranged to overlap in the airflow direction.
Fans, A premixing device is provided on the intake side of this fan and generates a mixture of air and fuel gas, which is then sent to the fan. A burner that receives the air-fuel mixture from the fan and burns the fuel gas, A combustion device equipped with, A combustion apparatus characterized in that the premixing device described in any one of claims 1 to 6 is used as the premixing device.

Description

The present invention relates to a premixing device and a combustion device equipped therewith. Here, "premixing" refers to the process of mixing air and fuel gas in advance to produce a combustible mixture, with the aim of performing premixed combustion. A specific example of a premixing apparatus is described in Patent Document 1. The premixing apparatus described in the document has a venturi-shaped premixing passage that has one end open to the outside and the other end connected to the intake side of a fan, and when the fan is driven, allows outside air to flow in from the opening at the one end and flow in a predetermined direction. This premixing passage is divided into a first passage and a second passage by a partition wall, and first and second fuel gas outlets are provided on the inner circumferential walls of these first and second passages, respectively. The first passage is also provided with a flapper that can swing to open and close this first passage. The opening of this flapper is changed in accordance with the airflow rate, such that when the airflow rate in the first passage is low, the opening is smaller than when the airflow rate is high. In such a premixing device, air flows through the premixing channel, and negative pressure acts on the first and second fuel gas outlets, causing fuel gas to flow out of these outlets into the premixing channel. This fuel gas mixes with the air to form a fuel-air mixture. On the other hand, when the airflow rate is low, the flapper closes the first channel of the premixing channel. This increases the airflow velocity in the second channel, strengthening the negative pressure acting on the second fuel gas outlet. As a result, even when the airflow rate is low, an appropriate amount of fuel gas can be released from the second fuel gas outlet due to the negative pressure. This effect is effective in increasing the turndown ratio. However, the aforementioned prior art still had room for improvement, as described below. In other words, when the flapper changes from a closed state to an open state, the effective flow area of the premixing channel changes abruptly. Therefore, as a result, the flow velocity of the airflow already present in the second channel may decrease sharply. This can lead to a sudden change in the mixture ratio, potentially resulting in an inappropriate fuel-lean mixture ratio. Furthermore, the flapper only opens and closes the first passage, and the first fuel gas outlet remains open. For this reason, even if the flapper switches the first passage from an open state to a closed state, there is a risk that fuel gas may leak out of the first fuel gas outlet for a period of time afterward. Moreover, the pressure fluctuations in the first passage due to the influence of the airflow in the second passage may cause air in the first passage to flow into (backflow) the first fuel gas outlet, or fuel gas may leak unnecessarily from the first fuel gas outlet. In this case, it is difficult to maintain the mixture at the desired appropriate mixing ratio. One way to resolve this is to provide an additional flapper for opening and closing the first fuel gas outlet (see Patent Document 2). However, this method requires the use of two flappers, one for the first flow path and one for the first fuel gas outlet, which increases the total number of parts and thus the manufacturing cost. Furthermore, in the aforementioned prior art (both Patent Documents 1 and 2), for example, if the flapper opening is not very large and the airflow rate in the first passage is relatively low, the airflow in the first passage is slow, making it difficult to apply a strong negative pressure to the first fuel gas outlet. Therefore, in such cases, the amount of fuel gas flowing out from the first fuel gas outlet may be insufficient, potentially resulting in an inappropriate mixture ratio. Japanese Patent Publication No. 2021-99204U.S. Publication No. 9,677,759 This is a schematic diagram illustrating an example of a combustion apparatus equipped with a premixing device according to the present invention.Figure 1 is a perspective view of the premixing apparatus.Figure 2 is an exploded perspective view.(a) is a front cross-sectional view of the premixing apparatus shown in Figure 1, (b) is a cross-sectional view of the premixing apparatus at a different location than (a), and (c) is a cross-sectional view of the IVc-IVc main section (right side cross-sectional view) of (b).(a) is a front cross-sectional view showing the flapper of the premixing apparatus shown in Figure 4(a) in a half-open state, and (b) is a cross-sectional view of the main right side of (a).(a) is a front cross-sectional view showing the flapper of the premixing apparatus shown in Figure 4(a) in the fully open state, and (b) is a cross-sectional view of the main right side of (a).(a) is a plan view of the premixing channel forming member of the premixing apparatus shown in Figures 2 and 3, and (b) is a plan