CN102767842A - Combustion efficiency control method and device - Google Patents

Abstract

The invention discloses a combustion efficiency control method and device, which belong to the field of combustion equipment and are designed to solve the problem that the combustion efficiency cannot be effectively controlled in the prior art. A method for controlling combustion efficiency, comprising: detecting the concentration of a measured gas at an exhaust port; judging whether the concentration exceeds a set concentration preset value; if the concentration exceeds the set concentration preset value , then increase the speed of the fan, if the concentration does not exceed the set preset value, then keep the fan working normally at the current speed; judge whether the speed exceeds the set maximum speed; if the speed exceeds the set If the maximum speed is set, keep the fan rotating at the current speed, close the main valve, sectional valve and the proportional valve leading to the combustible gas, and give an alarm. If the speed does not exceed the set maximum speed, Then detect the concentration of the measured gas at the exhaust port.

Description

Combustion efficiency control method and device

technical field

The invention relates to the field of combustion equipment, in particular to a method and device for controlling combustion efficiency.

Background technique

Electrical products that burn combustible gas for heating have become indispensable in home life, such as water heaters, etc., but because combustible gas needs to be burned, and the combustible gas may be toxic, it poses a certain threat to personal and property safety. Therefore, how to ensure higher safety performance has always been the focus of manufacturers' research.

In the prior art, taking a water heater as an example, a combustible gas is continuously introduced and burned, so as to heat the water passed into the water heater for use by users. When the user uses it, because the combustible gas is continuously fed into the water heater, the ratio of the combustible gas and the combustion-supporting gas will be out of balance, that is, the combustible gas is excessively supplied and the combustion-supporting gas is insufficiently supplied. At this time, in the process of burning the combustible gas, the combustible gas and the combustion-supporting gas are consumed together, but because of the lack of combustion-supporting gas, the combustion efficiency of the combustible gas will be reduced and the combustible gas cannot be fully combusted, and the remaining combustible gas is directly discharged from the water heater. It is discharged into the user's room, thereby reducing the safety of the water heater and endangering the personal and property safety of the user.

Contents of the invention

Embodiments of the present invention provide a combustion efficiency control method and device.

In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

A method for controlling combustion efficiency, comprising:

Detect the concentration of the measured gas at the exhaust port;

judging whether the concentration exceeds the set concentration preset value;

If the concentration exceeds the set concentration preset value, then increase the speed of the fan,

If the concentration does not exceed the set preset value, then keep the fan working normally at the current speed;

judging whether the rotational speed exceeds the set maximum rotational speed;

If the speed exceeds the set maximum speed, keep the fan rotating at the current speed, close the main valve, section valve and proportional valve that feed the combustible gas, and give an alarm,

If the rotational speed does not exceed the set maximum rotational speed, the concentration of the measured gas at the exhaust port is detected.

A control device for combustion efficiency, comprising

The control unit is respectively connected with the gas detection unit, the fan and the alarm unit; the gas detection unit is arranged at the exhaust port; the fan is arranged at the air inlet;

The gas detection unit is used to detect the concentration of the measured gas at the exhaust port;

The alarm unit is used for alarming;

The control unit also includes:

The fan control module is used to control the working state of the fan;

The first judging module is used to judge whether the concentration exceeds the set concentration preset value, if the concentration exceeds the set concentration preset value, increase the fan speed through the fan control module, if the second A judging module judges that the concentration does not exceed the set concentration preset value, then the fan control module keeps the fan working normally at the current speed;

The second judgment module is used to judge whether the speed exceeds the set maximum speed. If the second judgment module judges that the speed exceeds the set maximum speed, the valve control module closes the main valve and the section valve. And the proportional valve and alarm through the alarm unit, if the second judging module judges that the speed does not exceed the set maximum speed, the gas detection unit detects the concentration of the gas to be measured at the exhaust port;

The valve control module is used to control the on-off of the main valve, the section valve and the proportional valve that feed the combustible gas.

The combustion efficiency control method and device provided by the embodiments of the present invention detect the concentration of the measured gas at the exhaust port, adjust the speed of the fan at the air inlet according to the concentration, and blow in more combustion-supporting gas , so as to improve the combustion efficiency of combustible gas, ensure the safety of electrical products heated by combustible gas, and avoid the loss of personal and property caused by combustible gas that cannot be fully combusted and discharged into the user's room.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only of the present invention. For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the structural representation of the water heater described in the embodiment of the present invention;

Fig. 2 is a flowchart of a method for controlling combustion efficiency according to one embodiment of the present invention;

Fig. 3 is the relationship figure of measured gas concentration and fan speed in the embodiment of the present invention;

Fig. 4 is a flowchart of a method for controlling combustion efficiency according to another embodiment of the present invention;

Fig. 5 is a schematic structural diagram of a combustion efficiency control device according to one embodiment of the present invention;

Fig. 6 is a schematic structural diagram of a combustion efficiency control device according to another embodiment of the present invention.

Detailed ways

A combustion efficiency control method and device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

To make the description clearer, a water heater that heats water by burning combustible gas is taken as an example for description. As shown in Figure 1, when the user uses the water heater 1, the switch of the water heater is turned on (not shown in the figure), and the temperature of the water outlet during use is set; Combustible gas, the main components of combustible gas used in existing water heaters can be gases such as carbon monoxide and methane. Here, carbon monoxide is taken as an example for description. The valve 2 includes a main valve, a segment valve and a proportional valve; it is set at the water heater 1 inlet 4 The blower 5 at the place rotates and blows the combustion-supporting gas into the water heater 1. The combustion-supporting gas is generally air; the air as the combustion-supporting gas and the carbon monoxide as the combustible gas are mixed and burned in the combustion chamber 6, thereby passing through the heat exchanger (in the figure) not shown) to heat the water in the water tank 7; the gas after combustion is discharged from the water heater 1 through the exhaust port 8.

A control method of combustion efficiency, as shown in Figure 2, comprising:

200. Detect the concentration of the measured gas at the exhaust port.

The gas sensor 9 arranged at the exhaust port 8 detects the concentration of the measured gas in the combusted gas at the exhaust port 8, wherein the measured gas can be the concentration of carbon monoxide, methane, oxygen or carbon dioxide in the combusted gas, To make the description clearer, carbon monoxide is used as the gas to be measured. In the national standard, the concentration of carbon monoxide in the gas after combustion should not exceed 600 parts per million (Parts Per Million, hereinafter referred to as ppm), but in actual use, the concentration of carbon monoxide should generally be kept between 300ppm and 500ppm During this time, the concentration of combustible gas can be detected in real time.

201. Determine whether the concentration exceeds a set concentration preset value.

Judgment is made according to the preset concentration value preset in the water heater 1. The preset concentration value is obtained through multiple experiments, and the curve of the preset concentration value is obtained in the following manner:

Specify the opening of the proportional valve, and keep the opening of the proportional valve unchanged, where the maximum control current corresponding to the maximum opening of the proportional valve is 200 mA, and the minimum control current corresponding to the minimum opening is 40 mA; to set The control current is 200mA as an example for description. Under the proportional valve opening corresponding to 200mA, carbon monoxide is introduced; the fan 5 is started to pass the combustion-supporting gas into the water heater 1, and it is mixed with the combustible gas; through the gas sensor 9 Detect the concentration of carbon monoxide at exhaust outlet 8 places, for example the concentration that detects is that 550ppm has exceeded the scope of hope, improves the rotating speed of fan 5 by increasing the power of blower blower 5; Because of having promoted the rotating speed of blower blower 5, the concentration of carbon monoxide descends; When being detected When the concentration of measured gas becomes 500ppm, record the rotating speed of blower fan 5 under the situation of this opening, and as the first rotating speed; Continue to increase the rotating speed of blower blower 5, make the concentration of carbon monoxide drop to 300ppm, record the rotating speed of blower blower 5 as the first rotating speed; Two rotating speeds: Through multiple experiments between the minimum rotating speed of fan 5 and the highest rotating speed, it is determined that the control current of the proportional valve is 200 mA, and the rotating speed of fan 5 is related to the concentration of carbon monoxide at 8 places of the exhaust port.

In step 201, when judging whether the concentration exceeds the set concentration preset value, if the concentration exceeds the set concentration preset value, then

202. Increase the speed of the fan.

The water heater 1 obtains the rotational speed of the fan 5, and the acquisition of the rotational speed of the fan 5 may be specifically: obtaining the order of the fan corresponding to the rotational speed of the fan 5, wherein the order of the fan is equal to the maximum power and the minimum power of the fan 5 set at equal intervals.

The order of the fan can be set in the following manner, for example, the maximum power of the fan 5 is 35 watts and the corresponding fan 5 has a speed of 4000 revolutions per minute (revolutions per minute, hereinafter referred to as rpm), the minimum power is 15 watts and the corresponding fan 5 The rotation speed of 5 is 2000rpm, and the number of fan stages between the maximum power and the minimum power is 254, then the interval can be obtained as 0.08 watts; the adjustment of the power can be realized by adjusting the current or voltage; for example, in a water heater 1 In the case of normal operation, the order number of the obtained fan 5 is 127.

When using the water heater 1, the user sets the operating power of the water heater 1, that is, sets the opening degree of the corresponding proportional valve. For example, corresponding to the opening degree of the proportional valve, the control current of the proportional valve is 100 mA. The relationship between the speed of fan 5 and the concentration of carbon monoxide is shown in Figure 3, wherein A line and B line are the preset values of the concentration of carbon monoxide, and line C is the relationship between the concentration of carbon monoxide and the fan speed. During use, when the detected concentration of carbon monoxide is the concentration corresponding to point D, it can be seen that the concentration of carbon monoxide exceeds the concentration preset value. At this time, the combustion power of the combustible gas in the water heater 1 is reduced and cannot be fully burned. The reason why the combustion cannot be fully burned is that the concentration of the combustion-supporting gas in the water heater 1 is low; wherein the detection of the carbon monoxide concentration and the determination of whether the concentration exceeds the concentration preset value can be carried out in real time.

When it is known that the concentration of carbon monoxide at the air outlet 8 exceeds the concentration preset value, the speed of the blower fan is increased to increase the amount of air blown into the water heater 1, and the air contains combustion-supporting gas, so the concentration of the combustion-supporting gas in the water heater 1 is increased. Thereby improving the combustion efficiency of carbon monoxide.

Said improving the rotating speed of said blower fan can be specifically:

Through the pre-set interval fan order, such as 10, the fan order of fan 5 is improved; at this time, the amount of air blown by fan 5 is improved, and the concentration of combustion-supporting gas in the gas in water heater 1 is improved, so that the gas is in the air. The water heater 1 is mixed in a better ratio to improve the combustion efficiency of the combustible gas.

In the above case, when the concentration of carbon monoxide exceeds the preset concentration value, the opening of the proportional valve remains unchanged, and the speed of the combustible gas passed into the water heater 1 remains unchanged. At this time, only the fan 5 is used to increase the air There will be a situation that the adjustment speed of the combustion efficiency is low, thereby increasing the unsafe factor when the water heater 1 is used; in order to further improve the speed of adjusting the combustion efficiency, it also includes:

Get the opening degree of the proportional valve.

In said increasing the rotating speed of said blower fan, it also includes:

205. Decrease the opening degree of the proportional valve.

The water heater 1 obtains the opening degree of the proportional valve in the valve 2, and the valve 2 also includes a section valve and a main valve.

After the concentration of carbon monoxide exceeds the concentration preset value, increase the rotating speed of fan 5 to blow in more combustion-supporting gas. The problem of low combustion efficiency; at this time, reduce the opening of the proportional valve, reduce the amount of carbon monoxide introduced in the water heater 1, and reduce the concentration of carbon monoxide in the water heater 1, so as to blow in more combustion-supporting gas together The function improves the speed of the water heater 1 to adjust the combustion efficiency.

Wherein, the opening degree of the said obtaining proportional valve can be specifically:

Water heater 1 obtains the proportional valve order of the proportional valve; the proportional valve order can be set in the following way, for example, the maximum control current of the proportional valve is 200 mA and corresponds to the maximum opening of the proportional valve, and the minimum control current is 40 mA And corresponding to the minimum opening of the proportional valve, the order of the proportional valve between the maximum control current and the minimum control current is 254, then it can be obtained that the current interval is 0.63 mA; for example, when the water heater 1 is working normally, get The proportional valve order of the proportional valve is 127, and the proportional valve order is used as the original proportional valve order.

The user indirectly sets the power of the water heater 1 by setting the required outlet water temperature, and then also adjusts the steps of the proportional valve to adjust the temperature rise rate of the water in the water heater 1 .

The reduction of the opening of the proportional valve can be specifically:

Because it has been known that the concentration of carbon monoxide has exceeded the concentration preset value, on the one hand, the rotating speed of the blower fan 5 is increased, and on the other hand, the steps of the proportional valve are reduced according to a preset interval, such as 10, because reducing the steps of the proportional valve can Adjusting the control current of the proportional valve will further reduce the opening of the proportional valve; at this time, the amount of combustible gas passing into the water heater 1 will decrease, and the amount of combustible gas in the mixed gas in the water heater 1 will also decrease. The combustion-supporting gas in the water heater 1 improves the combustion efficiency of the combustible gas more rapidly, thereby further optimizing the speed of adjusting the combustion efficiency of the combustible gas in the water heater 1 .

203. Determine whether the rotational speed exceeds a set maximum rotational speed.

The water heater 1 detects the concentration of carbon monoxide in real time through the gas sensor 9. At this time, once the concentration of carbon monoxide exceeds the concentration preset value, the speed of the primary fan 5 is increased, and the adjusted speed of the fan 5 and carbon monoxide are continuously obtained. concentration. When increasing the speed of fan 5 for many times, the concentration of carbon monoxide cannot be restored to the preset concentration value, and the speed of fan 5 will exceed the preset maximum fan speed. Restore the density default value.

In step 203, when judging whether the rotational speed exceeds the set maximum rotational speed, if the rotational speed exceeds the set maximum rotational speed, then

204. The fan rotates at the current speed, closes the main valve, the section valve and the proportional valve that feed the combustible gas, and sends out an alarm.

At this moment, the water heater 1 closes the main valve, the sectional valve and the proportional valve that feed carbon monoxide, and gives an alarm, and the blower fan 5 keeps the current rotating speed and continues to rotate, blows a large amount of air into the water heater 1, reduces the concentration of carbon monoxide, and Ensure that the concentration of carbon monoxide in the gas discharged from the water heater 1 meets the standard; wherein the alarm can be set on the water heater 1 through the buzzer and light to alarm the user, thereby notifying the user that the staff needs to overhaul the water heater 1.

In step 203, when judging whether the rotating speed exceeds the set maximum rotating speed, if the rotating speed does not exceed the set maximum rotating speed, then repeat step 202 to gradually increase the rotating speed of the fan 5 until the rotating speed of the fan 5 Exceeding the maximum speed of fan 5 or the concentration of carbon monoxide returns to the concentration preset value.

When judging whether the concentration exceeds the set concentration preset value, if the concentration does not exceed the set concentration preset value, then

206. Keep the fan working normally at the current speed.

Because the detected concentration of carbon monoxide returns to the concentration preset value, it can be determined that the concentration of carbon monoxide in the water heater 1 and the concentration of the combustion-supporting gas have reached a better balance, thereby maintaining a higher combustion efficiency. At this time, keep the fan Rotate at the current speed, continue to blow combustion-supporting gas into the water heater 1, and maintain the normal operation of the water heater 1.

When the gas sensor 9 detects carbon monoxide, when the concentration is maintained at the concentration preset value by increasing the speed of the blower fan 5, the speed of the blower fan 5 has exceeded the blower speed measured through many tests, and continues under the blower speed. If the fan 5 blows a large amount of combustion-supporting gas, the concentration of the combustion-supporting gas in the water heater 1 will be too high, so that the carbon monoxide and the combustion-supporting gas will be out of balance again, reducing the combustion efficiency of the water heater 1; and the carbon monoxide that cannot be fully burned increases. , making the carbon monoxide at the exhaust port 8 exceed the concentration preset value again, causing the danger of using the water heater 1, so further, before the fan is kept working normally at the current speed, as shown in Figure 4, it also includes:

207. Reduce the speed of the fan.

Detect that the concentration of combustible gas returns to preset concentration value by gas sensor 9, as shown in point E shown in Figure 3, then reduce the rotating speed of blower fan 5; The number of fan stages is reduced step by step, thereby reducing the speed of the fan 5 .

208. Determine whether the rotation speed is lower than a set minimum rotation speed.

Judging the speed of the fan 5, if the speed of the fan 5 is less than the set minimum speed, then keep the fan rotating at the current speed, close the main valve, the section valve and the proportional valve that feed the combustible gas, and An alarm is issued, thereby reducing the risk of using the water heater 1 and avoiding continuous discharge of high-concentration carbon monoxide into the user's room. Wherein, the minimum rotation speed can be set by relevant staff, and the rotation speed of the fan 5 when the concentration of carbon monoxide reaches the preset value for the first time can also be recorded by the water heater 1 .

In step 208, when judging whether the rotational speed is less than the set minimum rotational speed, if the rotational speed is not less than the set minimum rotational speed, then

209. Determine whether the concentration exceeds the preset concentration value again.

If the concentration does not exceed the concentration preset value again, then keep the blower fan to work normally with the current speed, when the speed of the blower blower 5 does not reach the minimum speed, then repeat the detection of the concentration of carbon monoxide at the exhaust port 8 again; During the continuous reduction of the speed of the fan, if the concentration of carbon monoxide returns to the preset concentration value again, it can be known that the fan 5 has reached a reasonable working speed, and at this time, the current speed is maintained to make the water heater 1 work normally.

In step 209, when judging whether the concentration exceeds the preset concentration value again, if the concentration exceeds the preset concentration value again, then

207. Reduce the speed of the fan.

When it is determined that the concentration of carbon monoxide still exceeds the concentration preset value, then execute step 207-step 209 in a loop, so that the concentration of carbon monoxide in the water heater 1 returns to the concentration preset value or the speed of the fan 5 is less than the minimum speed.

In step 209, when judging whether the concentration exceeds the concentration preset value again, if the concentration does not exceed the concentration preset value again, then

206. Keep the fan working normally at the current speed.

When the rotation speed of the fan 5 is lower than the minimum rotation speed, the user is reminded that the water heater 1 requires staff to perform relevant maintenance.

In step 208, when judging whether the rotational speed is less than the set minimum rotational speed, if the said rotational speed is less than the set minimum rotational speed, then

204. Keep the blower rotating at the current speed, close the main valve, section valve, and proportional valve that feed the combustible gas, and issue an alarm.

In order to further optimize the adjustment of the proportional valve and the synchronization of the adjustment of the fan, preferably, the order of the fan corresponds to the order of the proportional valve one by one, and the order of the interval fan corresponds to the order of the interval proportional valve .

During the adjustment process of fan order and proportional valve order, if the set fan order and proportional valve order and interval fan order and interval proportional valve order do not correspond, the combustion efficiency may change too much , so that the change of the water temperature is too obvious, reducing the comfort of the user to use the water heater.

Through the correspondence between the order of the proportional valve and the order of the fan, when the order of the fan is increased, the order of the proportional valve can be correspondingly reduced, thereby ensuring a more stable adjustment of the combustion efficiency in the water heater 1 .

Corresponding to the above-mentioned combustion efficiency control method, the present invention also provides a combustion efficiency control device, as shown in Figure 1 and Figure 5, including:

The control unit is respectively connected with the gas detection unit, the fan 5 and the alarm unit; the gas detection unit is arranged at the exhaust port 8; the fan is arranged at the air inlet;

The gas detection unit is used to detect the concentration of the measured gas at the exhaust port, and the gas detection unit may be the above-mentioned gas sensor 9 arranged at the exhaust port 8;

The alarm unit is used for alarming, and the alarm unit can be an alarm lamp or a buzzer, etc.;

The control unit, as shown in Figure 6, also includes:

The fan control module is used to control the working state of the fan;

The first judging module is used to judge whether the concentration exceeds the set concentration preset value, and if the concentration exceeds the set concentration preset value, increase the fan speed through the fan control module;

The second judgment module is used to judge whether the speed exceeds the set maximum speed. If the second judgment module judges that the speed exceeds the set maximum speed, the valve control module closes the main valve and the section valve. And the proportional valve and alarm through the alarm unit, if the second judging module judges that the speed does not exceed the set maximum speed, the gas detection unit detects the concentration of the gas to be measured at the exhaust port;

The valve control module is used to control the on-off of the main valve, the section valve and the proportional valve that feed the combustible gas.

The valve control module is also used to control the opening of the proportional valve.

The first judging module is also used for:

If the first judging module judges that the concentration does not exceed the set preset value, the fan control module will keep the fan working normally at the current speed.

The control unit also includes:

The third judging module is used to judge whether the rotational speed is less than the set minimum rotational speed, if the said rotational speed is less than the set minimum rotational speed, an alarm will be issued through the alarm unit, if the said rotational speed is not less than the set minimum rotational speed Then judge whether the concentration exceeds the preset value of the concentration again through the fourth judging module;

If the fourth judging module judges that the concentration exceeds the concentration preset value again, the fan control module keeps the fan working normally at the current speed; if the fourth judging module judges that the concentration does not exceed the concentration preset value again The set value then reduces the speed of the fan through the fan control module.

The measured gas is combustible gas, combustion-supporting gas or generated gas.

Wherein, the acquisition of the rotational speed of the fan 5 by the first acquisition unit may specifically be: acquiring the order of the fan corresponding to the rotational speed of the fan 5, wherein the order of the fan is between the maximum power and the minimum power of the fan 5 Equally spaced settings.

The order of the fan can be set in the following manner, for example, the maximum power of the fan 5 is 35 watts and the corresponding fan 5 has a speed of 4000 revolutions per minute (revolutions per minute, hereinafter referred to as rpm), the minimum power is 15 watts and the corresponding fan 5 The rotating speed of 5 is 2000rpm, and the number of fan stages between the maximum voltage and the minimum power is 254, so the interval can be obtained as 0.08 watts; the adjustment of the power can be realized by adjusting the current or voltage of the fan 5 .

The second acquiring unit acquires the opening degree of the proportional valve, which may be specifically:

Water heater 1 obtains the proportional valve order of the proportional valve; the proportional valve order can be set in the following way, for example, the maximum control current of the proportional valve is 200 mA and corresponds to the maximum opening of the proportional valve, and the minimum control current is 40 mA And corresponding to the minimum opening of the proportional valve, the number of steps of the proportional valve between the maximum control current and the minimum control current is 254, so it can be obtained that the current interval is 0.63 mA.

In order to further optimize the adjustment of the proportional valve and the synchronization of the adjustment of the fan, preferably, the order of the fan corresponds to the order of the proportional valve one by one, and the order of the interval fan corresponds to the order of the interval proportional valve .

During the adjustment process of fan order and proportional valve order, if the set fan order and proportional valve order and interval fan order and interval proportional valve order do not correspond, the combustion efficiency may change too much , so that the change of the water temperature is too obvious, reducing the comfort of the user to use the water heater.

Through the correspondence between the order of the proportional valve and the order of the fan, when the order of the fan is increased, the order of the proportional valve can be correspondingly reduced, thereby ensuring a more stable adjustment of the combustion efficiency in the water heater 1 .

The combustion efficiency control method and device provided by the embodiments of the present invention detect the concentration of the measured gas at the exhaust port, adjust the speed of the fan at the air inlet according to the concentration, and blow in more combustion-supporting gas , so as to improve the combustion efficiency of combustible gas, ensure the safety of electrical products heated by combustible gas, and avoid the loss of personal and property caused by combustible gas that cannot be fully combusted and discharged into the user's room.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (9)

1. A method for controlling combustion efficiency, comprising: Detect the concentration of the measured gas at the exhaust port; judging whether the concentration exceeds the set concentration preset value; If the concentration exceeds the set concentration preset value, then increase the speed of the fan, If the concentration does not exceed the set preset value, then keep the fan working normally at the current speed; judging whether the rotational speed exceeds the set maximum rotational speed; If the speed exceeds the set maximum speed, keep the fan rotating at the current speed, close the main valve, section valve and proportional valve that feed the combustible gas, and give an alarm, If the rotational speed does not exceed the set maximum rotational speed, the concentration of the measured gas at the exhaust port is detected. 2. The method according to claim 1, characterized in that, if the concentration exceeds the set concentration preset value, further comprising reducing the opening of the proportional valve. 3. The method according to claim 2, characterized in that before maintaining the fan to work normally at the current speed, further comprising: reduce the speed of the fan; judging whether the rotational speed is less than the set minimum rotational speed; If the rotation speed is lower than the set minimum rotation speed, keep the fan rotating at the current rotation speed, close the main valve, section valve and the proportional valve leading to the combustible gas, and give an alarm, If the rotational speed is not less than the set minimum rotational speed, it is judged whether the concentration exceeds the preset value of the concentration again; If the concentration does not exceed the concentration preset value again, the fan is kept working normally at the current speed. 4. The method according to claim 3, wherein the maintaining the normal operation of the fan at the current speed further comprises: If the concentration exceeds the concentration preset value again, the speed of the blower is reduced. 5. The method according to any one of claims 1-4, characterized in that the measured gas is a combustible gas, a combustion-supporting gas or a generated gas. 6. A control device for combustion efficiency, comprising: The control unit is respectively connected with the gas detection unit, the fan and the alarm unit; the gas detection unit is arranged at the exhaust port; the fan is arranged at the air inlet; The gas detection unit is used to detect the concentration of the measured gas at the exhaust port; The alarm unit is used for alarming; The control unit also includes: The fan control module is used to control the working state of the fan; The first judging module is used to judge whether the concentration exceeds the set concentration preset value, if the concentration exceeds the set concentration preset value, increase the fan speed through the fan control module, if the second A judging module judges that the concentration does not exceed the set concentration preset value, then the fan control module keeps the fan working normally at the current speed; The second judgment module is used to judge whether the speed exceeds the set maximum speed. If the second judgment module judges that the speed exceeds the set maximum speed, the valve control module closes the main valve and the section valve. And the proportional valve and alarm through the alarm unit, if the second judging module judges that the speed does not exceed the set maximum speed, the gas detection unit detects the concentration of the gas to be measured at the exhaust port; The valve control module is used to control the on-off of the main valve, the section valve and the proportional valve that feed the combustible gas. 7. The device according to claim 6, wherein the valve control module is also used to control the opening of the proportional valve. 8. The device according to claim 6, wherein the control unit further comprises: The third judging module is used to judge whether the rotational speed is less than the set minimum rotational speed, if the said rotational speed is less than the set minimum rotational speed, an alarm will be issued through the alarm unit, if the said rotational speed is not less than the set minimum rotational speed Then judge whether the concentration exceeds the preset value of the concentration again through the fourth judging module; If the fourth judging module judges that the concentration exceeds the concentration preset value again, the fan control module keeps the fan working normally at the current speed; if the fourth judging module judges that the concentration does not exceed the concentration preset value again The set value then reduces the speed of the fan through the fan control module. 9. The device according to any one of claims 6-8, characterized in that the measured gas is combustible gas, combustion-supporting gas or generated gas.

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