JPH09236256A - Controller for pre-mixing type burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable controls of combustion by stably detecting supply pressures of combustion air. SOLUTION: Combustion air is supplied from the upstream side of a duct 1 and a burner element 2 is installed on the downstream side of the duct 1. A mixing section 3 is located in the middle of the duct 1 to mix up a fuel gas supplied through a fuel gas supply pipe 7 and the combustion air together. The mixing section 3 is a part of the duct 1 formed into a venturi-like shape and has fuel gas spouting holes 6 around a throat part 4b and a gas chamber 5 that leads to the fuel gas supply pipe 7 and is formed outside the throat part 4b. A controller controls at least one of the feed rates of combustion air and fuel gas based on detected pressures inside the gas chamber 5 of the mixing section 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a premix gas burner.

[0002]

2. Description of the Related Art As is well known, gas burners are roughly classified into a premixing type and a premixing type depending on the mixing system of fuel gas and combustion air. The former premixing type gas burner is for burning a premixed gas obtained by premixing fuel gas and combustion air at a predetermined ratio, and the latter premixing type and gas burner is
Fuel gas and combustion air are supplied separately and burned while mixing them at the burner tip. This premixing type gas burner has a narrower range of combustible air-fuel ratio (the ratio of the supply amount of combustion air and the supply amount of fuel gas) than that of the premixing type gas burner. There is a problem that the flame will extinguish when it exceeds, for example,
When the flow rate of fuel gas or combustion air supplied to the burner fluctuates and the air-fuel ratio of the premixed gas produced by them exceeds the combustible range, quenching occurs easily. Furthermore, even within this combustible range, the production amount of CO and NOx increases unless the air-fuel ratio is maintained within an appropriate range.

Therefore, in such a premixed gas burner, it is necessary to keep the air-fuel ratio as constant as possible,
Therefore, an air-fuel ratio control device is used. This air-fuel ratio control device, from the supply path of combustion air and fuel gas,
The respective supply pressures are detected, and the supply amount of combustion air, the supply amount of fuel gas, or both supply amounts are adjusted so that the air ratio is kept constant based on the detected pressures. Generally, the supply amount of the combustion air is adjusted by adjusting the opening degree of the damper, the rotation speed of the blower, etc., and the supply amount of the fuel gas is adjusted by the flow rate adjusting valve. Such an air-fuel ratio control device itself is known (for example, DMV-VEF type air-fuel ratio control cutoff valve manufactured by DUNGS, Landis Gear (LANDIS & GYR)).
System 70 type air-fuel ratio control shutoff valve manufactured by the company).

By the way, the premixing gas burner has a mixing portion for mixing the combustion air and the fuel gas in order to obtain the premixed gas, and the air-fuel ratio control device can perform precise control. In order to carry out, the pressure of the combustion air on the upstream side of the mixing section and the pressure of the combustion air on the mixing section or on the downstream side of the mixing section are detected. But,
Generally, in such a premixing gas burner, it is necessary to obtain a premixed gas that is uniformly mixed in order to improve combustion performance, and various devises have been made regarding the configuration of the mixing section. In this case, depending on the shape of the mixing portion, a detection error of the supply pressure of the combustion air becomes large due to the generation of a vortex in the combustion air flow, and thus the operation of such an air-fuel ratio control device becomes unstable. Sometimes became. For example, there is a case where the mixing portion is bent or an orifice-shaped member is arranged in order to improve the mixing property.

[0005]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a premixing system capable of stably detecting the supply pressure of combustion air and thereby performing stable combustion control. It is to provide a control device for a gas burner.

[0006]

SUMMARY OF THE INVENTION According to the present invention, combustion air is supplied from an upstream side, a burner element is attached to a downstream side, and a fuel gas is supplied from a fuel gas supply pipe. A mixing section for mixing with the combustion air is provided on the way, and the mixing section forms a substantially venturi shape in the duct, forms a fuel gas ejection hole in the throat section, and forms an outer side of the throat section. Is provided with a gas chamber communicating with the fuel gas supply pipe, based on the pressure detected in the gas chamber of the mixing unit,
It is an object of the present invention to solve the above-mentioned problems by a control device for a premixed gas burner including a control device that controls the supply amount of at least one of combustion air and fuel gas.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The premixing type gas burner according to the present invention is provided with a mixing portion for mixing combustion air and fuel gas in the middle of a duct to which combustion air is supplied, and this mixing portion is substantially a venturi. By forming a gas injection hole in the venturi-shaped throat part that has a reduced diameter, the combustion air contracts in the throat part and is converted into a high-speed flow. The air is mixed, and a gas chamber communicating with the fuel gas supply pipe is provided outside the throat portion. In this premixed gas burner, the control device controls the supply amount of at least one of the combustion air and the fuel gas based on the detected value of the pressure in the gas chamber.

That is, in the control device for the premixed gas burner according to the present invention, the pressure (static pressure) on the combustion air side in the throat section is measured as the pressure in the gas chamber. The pressure measuring hole is not provided in the portion where the combustion air flows, but is provided in the gas chamber outside the throat portion. That is, since the mixing section has a Venturi shape, the flow rate of the combustion air can be obtained by measuring the pressures on the upstream side and the throat section. It is used as static pressure.

By measuring the pressure in the gas chamber in this way, the influence of the contraction flow of the combustion air in the throat and the vortex flow generated therewith, and further, the injection of the fuel gas into this combustion air It is possible to stably detect the supply pressure of the combustion air without being affected by the pressure fluctuation due to the influence of. Therefore, the combustion air by the control device,
It is possible to stably control the supply amount of the fuel gas.

The control device controls the supply amount of at least one of combustion air and fuel gas.
An air-fuel ratio controller that controls the supply amount of fuel gas to the combustion air (or vice versa) as described above, or the supply amount of combustion air and fuel gas while keeping the air-fuel ratio at a predetermined value. This is a concept that includes a combustion amount control device that increases / decreases. Further, the duct functions as a flow path for supplying combustion air to the burner element, and the burner element is a portion that ejects the premixed gas to perform actual combustion.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a premixing type gas burner control device according to the present invention will be specifically described below with reference to the drawings. 1 is a drawing for explaining a schematic configuration of an embodiment of the present invention, and FIG. 2 is a drawing for explaining a structure of a mixing portion of an embodiment according to the present invention, which is II-II of FIG. It is sectional drawing which follows the line.

In the drawings, a premixed gas burner according to the present invention is a tubular duct that forms a flow path for combustion air.
A burner element (2) for injecting and burning the premixed gas is provided on the downstream side of (1). On the other hand, combustion air is supplied to the upstream side of the duct (1) by a blower or the like (not shown). In the middle of the duct (1), a mixing section (3) having a substantially Venturi shape is provided. That is, the duct (1)
A pair of similar shaped diaphragm members (4) are arranged so as to face each other at a predetermined position, and a substantially Venturi-shaped mixing portion (3) is formed in the central portion. In this embodiment, the width of the throttle member (4) is approximately equal to the inner width of the duct (1), and the facing throttle member (4) allows the duct (1) to store the combustion air. From the upstream side in the flow direction, the nozzle portion (4a) whose flow passage cross-sectional area gradually decreases, the throat portion (4b) whose flow passage cross-sectional area gradually becomes the same, the diffuser portion (4
Configure c).

Outside the throttle member (4), that is, the duct (1)
A gas chamber (5) is formed in the space between the inside and the inside. A large number of small holes are formed as gas ejection holes (6) in the throat portion (4b) corresponding to the mixing portion (3). The gas chamber
A fuel gas supply pipe (7) for supplying a fuel gas is connected to (5) from the outside of the duct (1). When connecting the fuel gas supply pipe (7), the duct (1) may be connected from any direction such as the left-right direction and the front-back direction. In this embodiment, as shown in FIG. ) On one side wall surface, a through hole (8) communicating with the gas chamber (5) is formed, and a branch pipe (9) is connected to cover the through hole (8),
The fuel gas supply pipe (7) is connected to the branch pipe (9). Further, on the upstream side of the mixing section (3), there is provided a damper (13) for adjusting the supply amount of combustion air, and the opening degree of the damper (13) depends on a driving device such as a motor ( 14)
Will be adjusted by

According to the gas burner having the above structure, the duct
(1) The combustion air supplied from the upstream end has a flow passage cross-sectional area in the range of about 1/5 to 1/7 in the mixing section (3) formed by arranging two throttle members (4). It will be narrowed down. Therefore, the flow velocity of the combustion air is increased, and a vortex region is generated at the boundary surface of this high-speed air flow due to the flow velocity difference. That is, a high-speed air flow is generated in the throat section (4b) of the mixing section (3),
Since a vortex region is generated in the center, the fuel gas supply pipe
The fuel gas supplied from (7) through the gas chamber (5) and the gas ejection hole (6) is effectively separated from the throat portion (4b) and efficiently premixed with the combustion air. Then, in the diffuser part (4c), the dynamic pressure is smoothly converted to the static pressure, and the burner element at the downstream end of the duct (1) is
Supply premixed air to (2). In the throat portion (4b) formed with the gas ejection holes (6), the flow velocity of the combustion air is increased, so that the suction force is increased and the gas pressure in the fuel gas supply pipe (7) can be lowered. . That is, in the premixed gas burner of this configuration, a substantially venturi-shaped mixing section (3) is provided at a predetermined position of the duct (1), and the mixing section (3)
Since the gas ejection hole (6) of the fuel gas supply pipe (7) was opened in the above, by injecting the fuel gas into the swirl region generated in the mixing section (3), the combustion air is entrained by the effect of the swirl flow. It is possible to promote the mixing of the fuel gas with the fuel gas and generate a uniform premixed gas. Further, since the flow velocity of the combustion air in the mixing section (3) is increased, the suction force of the fuel gas is increased, and the gas supply pressure in the fuel gas supply pipe (7) can be lowered, thus reducing the piping cost. can do.

Now, in such a premixing type gas burner, the control device (10) is connected as follows. That is, as shown in FIGS. 1 and 2, the control device (10) is connected to the fuel gas supply pipe (7), and the orifice (15) is connected to the downstream side of the control device (10). I am doing it. Here, in this embodiment, the air-fuel ratio control device described above is used as the control device (10). This control device (10) consists of a flow control valve (11) connected to the fuel gas supply pipe (7) and a duct (1).
The first pressure detection point (16) located upstream of the mixing section (3) in the second and the second pressure detection point located in the gas chamber (5) of the mixing section (3).
Pressure detection point (17) and third pressure detection point connected downstream of the flow control valve (11) in the fuel gas supply pipe (7)
And a control unit (12) for controlling the flow control valve (11) based on the pressure of (18). The first pressure detection point (16)
Is the pressure of the combustion air on the upstream side of the mixing section (3) and is the first pressure detection pipe (16) connected to the side surface of the duct (1).
The detection pressure is input by connecting a) to the control unit (12). The second pressure detection point (17) is the pressure in the gas chamber (5), and the second pressure detection pipe (17a) connected to the gas chamber (5) is connected to the control unit (12). Thus, the detected pressure is input. The third pressure detection point (18) is the supply pressure of the fuel gas, and is located downstream of the flow control valve (11) of the control device (10) at the orifice (1
The detection pressure is input by connecting the third pressure detection pipe (18a) connected to the fuel gas supply pipe (7) on the upstream side of 5) to the control unit (12).

In this premixing type gas burner, since the mixing part (3) has a venturi shape, the pressure (static pressure) of the combustion air between the upstream side of the mixing part (3) and the throat part (4b) is measured. By doing so, the flow rate of the combustion air can be obtained, but in the present invention, the pressure in the gas chamber (5) is detected as the static pressure of the combustion air in the throat portion (4b). That is, in the control device for the premixed gas burner according to the present invention, the pressure (static pressure) of the combustion air in the throat section (4b) is measured as the pressure in the gas chamber (5). The second pressure detection point (17) is provided as a pressure detection point in the gas chamber (5) outside the throat section (4b). Here, instead of the pressure of the combustion air in the mixing section (3), the pressure in the gas chamber (5) is detected, and the detected value of this pressure is input to the control device (10) to mix. It is possible to stably detect the differential pressure of air before and after the part (3). That is, in the mixing part (3), the air flow path in the duct (1) is narrowed, and the combustion air flowing in this part becomes a contracted flow and has a high speed. Causes pressure to become unstable. Moreover, at the throat portion (4b), the pressure is unstable because the fuel gas is ejected. Therefore, in the present invention, instead of the pressure of the combustion air in the mixing section (3), the pressure in the gas chamber (5) of the mixing section (3) is detected. That is, the pressure of the gas chamber (5) is higher than the pressure of the combustion air by a certain pressure because the fuel gas is ejected to the mixing section (3), and the gas chamber (5)
This is because the fuel gas only flows and is stable.

Further, in the control device (10), the air-fuel ratio is controlled based on the pressure detected from the first to third pressure detection points (16) to (18). And the second pressure detection point
The flow rate is adjusted so that the ratio of the pressure difference between (17) and the pressure difference between the first pressure detection point (16) and the second pressure detection point (17) becomes a value corresponding to the air-fuel ratio. The control valve (12) is controlled to adjust the supply amount of combustion gas with respect to the supply amount of combustion air.
That is, assuming that the pressures detected at the first to third pressure detection points (16) to (18) are P _{1 to} P ₃ , respectively, the formula: (P ₃ −
Value obtained by _{P 2) / (P 1 -P} 2) has adjusted the supply amount of the combustion gas to the feed amount of combustion air to a predetermined value corresponding to the air-fuel ratio. Here, the pressure of the combustion air supplied to the duct (1) is usually higher than the pressure of the fuel gas, and the pressure of the combustion air in the mixing section (3) is supplied to the duct (1). It is lower than the pressure of the combustion air and close to the pressure of the fuel gas. In the premixed gas burner of the present invention in which the supply pressure of the fuel gas is set low, unless the pressure fluctuation at the second pressure detection point (17) is kept low, the fluctuation amount of the supply amount of the fuel gas is Although it becomes large, the stable control of the air-fuel ratio becomes possible by providing the second pressure detection point (17) in the gas chamber (5) like the control device of the present invention. Further, by setting the third pressure detection point (18) at a position upstream of the orifice (15) in the fuel gas supply pipe (7), pressure loss occurring before and after this orifice (15) The pressure difference between the second pressure detection point (17) and the third pressure detection point (18) is enlarged, the value obtained by the above equation is enlarged, and the air-fuel ratio control is made more stable.

[0018]

As described above, according to the present invention, a venturi-shaped mixing section is provided in the middle of a duct to which combustion air is supplied, and a gas for supplying a fuel gas to a gas ejection hole provided in the throat section. Since it controls the supply of at least one of combustion air and fuel gas based on the pressure detected in the room, the influence of the contraction flow of combustion air in the throat and the accompanying vortex flow Further, the supply pressure of the combustion air can be detected stably without being affected by the pressure fluctuation due to the effect of the injection of the fuel gas onto the combustion air, and the combustion air and the fuel gas by the control device can be detected. It is possible to stably control the supply amount of.

[Brief description of drawings]

FIG. 1 is a drawing for explaining a schematic configuration of an embodiment according to the present invention.

FIG. 2 is a drawing for explaining the structure of the mixing portion of the embodiment according to the present invention and is a cross-sectional view taken along line II-II of FIG.

[Explanation of symbols]

 (1) Duct (burner duct) (2) Burner element (3) Mixing part (4b) Throat part (5) Gas chamber (6) Gas ejection hole (7) Fuel gas supply pipe (10) Control device

Claims (1)

[Claims] 1. A duct (1) receiving a supply of combustion air from an upstream side and having a burner element (2) attached to a downstream side.
And fuel gas supply from the fuel gas supply pipe (7),
A mixing section (3) for mixing with the combustion air in the middle of the duct (1), wherein the mixing section (3) is the duct
(1) The inside is formed into a substantially Venturi shape, the fuel gas ejection hole (6) is formed in the throat portion (4b), and the fuel gas supply pipe (7) communicates with the outside of the throat portion (4b). A gas chamber (5) is provided, and a control device for controlling the supply amount of at least one of combustion air and fuel gas based on the pressure detected in the gas chamber (5) of the mixing section (3) ( Ten)
A control device for a premixed gas burner, which is characterized in that: