EP2363642B1 - Gas fuel driven burner with regulating device and method for regulating the fuel-air ratio of the gas fuel driven burner - Google Patents

Description

The invention relates to an apparatus and a method for controlling the fuel gas-air ratio of a gas-powered burner.

Out EP 1082575 . EP 1207347 . EP 1179159 and EP 1084369 are devices and methods for controlling the fuel gas to air ratio of a gas-powered burner known, which has in common that in the combustion air and fuel gas each throttle is arranged, the fuel gas in the combustion air always takes place downstream of the throttle in the combustion air and the combustion air and Brenngasweg each static pressure is removed.

Throttle cause throttle losses and thus reduce the overall efficiency.

The invention has for its object to provide an apparatus and a method for controlling the fuel gas to air ratio of a fuel gas burner, which is characterized by low pressure losses and high control quality.

According to the invention this is achieved according to the features of the independent device claim 1 and the independent method claim 5, characterized in that the flow cross-sections for fuel gas and air are matched to one another, that result in the desired fuel gas to air ratio equal dynamic pressures or a predetermined, fuel gas and load-dependent difference value. By dispensing with diaphragms, pressure losses are reduced.

Advantageous embodiments of the invention will become apparent from the features of the dependent claims.

• Figur 1 eine erfindungsgemäße Vorrichtung,
• Figur 2 eine alternative erfindungsgemäße Vorrichtung,
• Figur 3 den Luftströmungskanal auf der Höhe der Messstelle in der Draufsicht,
• Figur 4 denselben Luftströmungskanal auf der Höhe der Messstelle in der Seitenansicht in der Position des größten Strömungsquerschnitts und
• Figur 5 denselben Luftströmungskanal auf der Höhe der Messstelle in der Seitenansicht in der Position des kleinsten Strömungsquerschnitts.

The invention will now be explained in detail with reference to FIGS. Hereby show:

• FIG. 1 a device according to the invention,
• FIG. 2 an alternative device according to the invention,
• FIG. 3 the air flow channel at the height of the measuring point in plan view,
• FIG. 4 the same air flow channel at the height of the measuring point in the side view in the position of the largest flow cross-section and
• FIG. 5 the same air flow channel at the height of the measuring point in the side view in the position of the smallest flow cross-section.

FIG. 1 shows a control device for a fuel-operated burner 5 with a controllable fan 1, a combustion air line 3, which is connected to the blower 1, a fuel gas line 4, in which a controllable via an actuator 10 fuel gas valve 2 and which opens into the combustion air line 3, and a pressure or flow sensor 6, which is arranged between the combustion air line 3 and the fuel gas line 4. In the combustion air line 3 is a first Pressure receiving points 7; in the fuel gas line 4, a second pressure receiving point 8. The two pressure receiving points each take on the total pressure. Accordingly, their openings are directed against the flow direction. In the combustion air line 3, no further separate aperture is arranged. In the combustion air line 3, a displaceable insert 9 is arranged; this can be moved in the extension direction of the combustion air line 3. A control is connected to the pressure or flow sensor 6, the actuator 10 and the fan 1. If the movable insert 9 is adjustable by motor, it is also connected to the controller 11. In FIG. 1 the fan 1 between the combustion air duct 3 and the burner 5 is arranged. Combustion air line 3 and fuel gas line 4 both open into the fan. 1

By contrast, the blower 1 in a device according to FIG. 2 arranged in the combustion air line 3 upstream of the pressure receiving point 7.

FIG. 3 shows the combustion air duct 3 in plan view. The combustion air duct 3 has a rectangular cross-section. The insert 9 is slidably disposed on the upper wall. FIG. 4 shows the combustion air duct 3 at the height of the measuring point 7 in the side view in the position of the largest flow cross-section, while FIG. 5 the same combustion air duct 3 at the height of the measuring point 7 in the side view in the position of the smallest flow cross-section shows. In both cases, the flow cross section around the pressure receiving point 7 around is constant, which is necessary for the control method.

The process according to the invention is based on the following technical principles.

The minimum air requirement I _min is a measure of how much combustion air per fuel gas is required for stoichiometric combustion. The air ratio λ is a measure of how much air in the air Comparison to the stoichiometric air quantity is present. For the ratio of combustion air volume flow V̇ _L to fuel gas volume flow V̇ _{G the} following applies: $${\dot{V}}_{\mathrm{L}}=I_{\min }\cdot \lambda \cdot {\dot{V}}_{\mathrm{G}}$$

Furthermore: $$\dot{V}=c\cdot A$$

wobei p _dyn den dynamischen Druck des strömenden Mediums und ρ seine Dichte bezeichnet.Here, c is the flow velocity and A is the area. With respect to the total pressure p _ges for a flowing gas applies $$p_{\mathrm{ges}}=p_{\mathrm{stat}}+p_{\mathrm{dyn}}=p_{\mathrm{stat}}+\frac{\rho }{2}{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="imgf0001.png"\; state="\{\{state\}\}">c</figure-callout>}}^2.$$

where p _dyn denotes the dynamic pressure of the flowing medium and ρ its density.

$$c_{\mathrm{L}}=\sqrt{\frac{{\rho }_{\mathrm{G}}}{{\rho }_L}}{c}_{\mathrm{G}}$$

In a device according to the invention, the two gas streams flow unthrottled into one another. Their static pressures are thus the same. In a zero pressure control by means of a device according to the invention, therefore, the dynamic pressures must be equal. Hereinafter, the index L for the combustion air and the index G for the fuel gas. $$\frac{{\rho }_{\mathrm{L}}}{2}{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_{L^{}}=\frac{{\rho }_{\mathrm{G}}}{2}{c}_{G^2}$$

$$c_{\mathrm{L}}=\sqrt{\frac{{\rho }_{\mathrm{G}}}{{\rho }_L}}{c}_{\mathrm{G}}$$

$$\sqrt{\frac{{\rho }_G}{{\rho }_L}}{c}_{\mathrm{G}}\cdot A_{\mathrm{L}}=I_{\min }\cdot \lambda \cdot c_{\mathrm{G}}\cdot A_{\mathrm{G}}$$

$$A_{\mathrm{L}}=I_{\min }\cdot \mathit{\lambda }\cdot \sqrt{\frac{{\rho }_L}{{\rho }_G}}\cdot A_{\mathrm{G}}$$

Regarding the flow cross sections thus applies $${\dot{V}}_{\mathrm{L}}=c_{\mathrm{L}}\cdot A_{\mathrm{L}}=I_{\min }\cdot \lambda \cdot c_{\mathrm{G}}\cdot A_{\mathrm{G}}$$

$$\sqrt{\frac{{\rho }_G}{{\rho }_L}}{c}_{\mathrm{G}}\cdot A_{\mathrm{L}}=I_{\min }\cdot \lambda \cdot c_{\mathrm{G}}\cdot A_{\mathrm{G}}$$

$$A_{\mathrm{L}}=I_{\min }\cdot \mathit{\lambda }\cdot \sqrt{\frac{{\rho }_L}{{\rho }_G}}\cdot A_{\mathrm{G}}$$

For methane ( I _min = 9.52, density p = 0.7175 kg / m ³ ) thus applies $$A_{\mathrm{L}}=\mathit{\lambda }\cdot 12.87\cdot A_{\mathrm{G}}$$

$$d_{\mathrm{L}}\approx 4\cdot d_{\mathrm{G}}$$

For an air ratio of 1.25, this means for the cross-sectional areas A and d: $$A_{\mathrm{L}}\approx 16\cdot A_{\mathrm{G}}$$

$$d_{\mathrm{L}}\approx 4\cdot d_{\mathrm{G}}$$

In the case of liquid gas (standard gas G31), the ratio A _L / A _{G is} 24 for the same air ratio and 12.3 for low calorific fuel gas (standard gas G27).

In order to adjust these conditions, the adjustable insert 9 is arranged in the combustion air line 3. Alternatively, this insert could also be arranged in the fuel gas line 4. The arrangement in the combustion air line 3 has the advantage that the adjustment mechanism does not have to be completely sealed from the environment.

To adjust the type of gas, the adjustable insert 9 is displaced, whereby the flow cross-section is set at the height of the pressure receiving point 7. The insert 9 is designed such that both a certain distance before the pressure receiving point 7, as well as behind the air flow cross section is constant. Above mentioned numerical examples show that the air flow cross-section must be approximately halved by means of the displaceable insert.

If the cross sections are not adjusted to zero pressure control, then $$\mathrm{\Delta }\mathit{p}=p_{\mathrm{G}}-p_{\mathrm{L}}=p_{\mathrm{stat}.\mathrm{G}}+\frac{{\rho }_{\mathrm{G}}}{2}{c}_{{\mathrm{G}}^2}-p_{\mathrm{stat}.\mathrm{L}}+\frac{p_L}{2}{{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_L}^2\mathrm{,}$$

gilt $$\mathrm{\Delta }\mathit{p}=\frac{{\dot{V}}_G^2}{2}\left(\frac{{\rho }_{\mathrm{G}}}{A_{\mathrm{G}}^2}-\frac{{\rho }_{\mathrm{L}}\cdot {I_{\min }}^2\cdot {\lambda }^2}{A_{\mathrm{L}}^2}\right),$$

beziehungsweise $$\mathrm{\Delta }\mathit{p}=\frac{{\dot{V}}_{\mathrm{L}}^2}{2}\left(\frac{{\rho }_{\mathrm{G}}}{{I_{\min }}^2\cdot {\mathit{\lambda n}}^2\cdot A_{\mathrm{G}}^2}-\frac{{\rho }_{\mathrm{L}}}{A_{\mathrm{L}}^2}\right)$$

$$\mathrm{\Delta }\mathit{p}=\frac{c_{\mathrm{L}}^2}{2}\left(\frac{{\rho }_{\mathrm{G}}\cdot A_{\mathrm{L}}^2}{{I_{\min }}^2\cdot {\lambda }^2\cdot A_{\mathrm{G}}^2}-{\rho }_{\mathrm{L}}\right)\mathrm{.}$$

Assuming that the static pressures are the same again, and with $\mathrm{c}=\frac{\dot{V}}{A}$

applies $$\mathrm{\Delta }\mathit{p}=\frac{{\dot{V}}_{\mathrm{<figure-callout\; id="2"\; label="G"\; filenames="imgf0001.png"\; state="\{\{state\}\}">G</figure-callout>}}^2}{2}\left(\frac{{\rho }_{\mathrm{G}}}{A_{\mathrm{G}}^2}-\frac{{\rho }_{\mathrm{L}}\cdot {I_{\mathrm{<figure-callout\; id="2"\; label="min"\; filenames="imgf0001.png"\; state="\{\{state\}\}">min</figure-callout>}}}^2\cdot {\lambda }^2}{{\mathrm{<figure-callout\; id="2"\; label="A\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">A\; </figure-callout>}}_{\mathrm{L}}^{\mathrm{}}}\right).$$

respectively $$\mathrm{\Delta }\mathit{p}=\frac{{\dot{\mathrm{<figure-callout\; id="2"\; label="V\; ̇\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">V\; </figure-callout>}}}_{\mathrm{L}}^{\mathrm{}}}{2}\left(\frac{{\rho }_{\mathrm{<figure-callout\; id="2"\; label="G\; I\; min"\; filenames="imgf0001.png"\; state="\{\{state\}\}">G\; </figure-callout>}}}{{I_{\min }}^{}}-\frac{{\rho }_{\mathrm{<figure-callout\; id="2"\; label="L\; A\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">L\; </figure-callout>}}}{A_{\mathrm{L}}^{}}\right)$$

$$\mathrm{\Delta }\mathit{p}=\frac{{\mathrm{<figure-callout\; id="2"\; label="c\; L"\; filenames="imgf0001.png"\; state="\{\{state\}\}">c\; </figure-callout>}}_{\mathrm{L}}^{\mathrm{}}}{2}\left(\frac{{\rho }_{\mathrm{G}}\cdot A_{\mathrm{L}}^2}{{I_{\mathrm{<figure-callout\; id="2"\; label="min"\; filenames="imgf0001.png"\; state="\{\{state\}\}">min</figure-callout>}}}^2\cdot {\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}^2\cdot A_{\mathrm{G}}^2}-{\rho }_{\mathrm{L}}\right)\mathrm{,}$$

Thus can be regulated at a known air velocity in the air supply line to a desired differential pressure. For a certain load of the burner, a certain amount of air is needed; this in turn has a certain air velocity result. This can either be measured or determined, for example, from the blower speed and known device-specific characteristic curve. With power modulation, the differential pressure changes with this method.

LIST OF REFERENCE NUMBERS

• Blower 1
• Fuel gas valve 2
• Combustion air line 3
• Fuel gas line 4
• Burner 5
• Pressure or flow sensor 6
• first pressure receiving points 7
• second pressure receiving point 8
• sliding insert 9
• Actuator 10
• Regulation 11

Claims (6)

1. A gas fuel driven burner (5) with a regulating device for the gas fuel driven burner (5), comprising a controllable blower (1), a combustion air pipe (3) connected with the blower (1), a fuel gas pipe (4) containing a controllable fuel gas valve (2) and leading into the combustion air pipe (3), and a pressure and flow sensor (6) arranged between the combustion air pipe (3) and the fuel gas pipe (4), characterized in that pressure receiving positions (7, 8) in the combustion air pipe (3) and the fuel gas pipe (4) each receive a total pressure, and the pressure receiving positions are arranged with their openings against the flow direction and no separate aperture is provided in the combustion air pipe (3).
2. The gas fuel driven burner (5) with a regulating device for the gas fuel driven burner according to claim 1, characterized in that the combustion air pipe (3) has a cross section which is 12 to 24 times the size, preferably 16 times the size, at the level of the pressure receiving position (7), and/or with a circular cross section preferably has a diameter which is four times the size of the diameter ,of that of the fuel gas pipe (4) at the pressure receiving position (8).
3. The gas fuel driven burner (5) with a regulating device for the gas fuel driven burner according to claim 1 or 2, characterized in that the cross section of the combustion air pipe (3) and/or the fuel gas pipe (4) is adjustable at least at the level of the corresponding pressure receiving positions (7, 8).
4. The gas fuel driven burner (5) with a regulating device for the gas fuel driven burner according to claim 3, characterized in that the cross section of the combustion air pipe (3) and/or the fuel gas pipe (4) tapers at least at the level of the corresponding pressure receiving position (7, 8) and a movable insert (9) is arranged in this area, wherein the insert (9) tapers to the same extent as the corresponding pipe (3, 4), such that for each position of the insert (9) a section of the same cross section around the corresponding pressure receiving position (7, 8) is present.
5. A method for regulating a gas fuel driven burner with a regulating device for the gas fuel driven burner (5) with a controllable blower (1), a combustion air pipe (3) connected with the blower (1), a fuel gas pipe (4) containing a controllable fuel gas valve (2) and leading into the combustion air pipe (3), and a pressure and flow sensor (6) arranged between the combustion air pipe (3) and the fuel gas pipe (4), characterized in that the pressure receiving positions (7, 8) in the combustion air pipe (3) and the fuel gas pipe (4) are arranged with their openings against the flow direction and each receive a total pressure, and no separate aperture is provided in the combustion air pipe (3), wherein the opening cross section of the fuel gas valve (2) is adjusted such that the pressure and flow sensor (6) measures the same pressure, or no flow, on both sides, or the differential pressure or the flow speed, respectively, correspond to a predetermined load-dependent and gas-type-dependent set value.
6. The method for regulating a gas fuel driven burner with a regulating device according to claim 5, characterized in that the cross section of the combustion air pipe (3) and/or the fuel gas pipe (4) tapers at least at the level of the corresponding pressure receiving position (7, 8) and a movable insert (9) is arranged in this area, wherein the insert (9) tapers to the same extent as the corresponding pipe (3, 4), such that for each position of the insert (9) a section of the same cross section around the corresponding pressure receiving position (7, 8) is present, wherein the insert (9) is moved to a position set for a particular fuel gas.

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