Dual cross-limiting combustion ratio control method

Abstract

The application provides a double-cross limiting amplitude combustion proportion control method. The system obtains an air flow setting value SPoutair=MAX[SPgas, PVgas]*R according to cross limiting amplitude calculation; the system obtains a gas flow setting value SPoutgas=MIN[PVair / R, SPgas] according to cross limiting amplitude calculation; the system also introduces oxygen concentration control analysis, calculates an air-fuel ratio R according to an oxygen concentration setting value SPo2 and an oxygen concentration actual value PVo2, and replaces the initial setting value of the air-fuel ratio R. When the gas demand changes sharply, the gas and air can be ensured to rise / drop proportionally from the current stable flow, and the air amount is always slightly more than the gas amount, so that the combustion is ensured to be sufficient. When the air amount is insufficient, the gas amount can be ensured to be not excessive, so that the insufficient combustion to produce black smoke is avoided. When the gas amount is insufficient, the air amount can be ensured to be not excessive, so that the excessive air is avoided to enter and cause energy waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-nitrogen combustion, and particularly relates to a double-cross limiting-amplitude combustion ratio control method. BACKGROUND

[0002] With the improvement of social life quality, the requirement for environmental protection is higher and higher, and the requirement for industrial burner combustion tail gas emission is also more and more strict.

[0003] The existing industrial burner combustion regulation mode is relatively simple, when the gas demand changes sharply, black smoke is easily generated due to insufficient air, or too much air enters to cause energy waste due to insufficient gas. Therefore, a more optimized combustion control method needs to be proposed. SUMMARY

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present application is to provide a double-cross limiting-amplitude combustion ratio control method.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application to solve its technical problems is: a double-cross limiting-amplitude combustion ratio control method based on a control system, wherein the control system comprises:

[0006] a temperature sensor for detecting the actual temperature value PVtemp in the combustion furnace in real time;

[0007] an oxygen sensor for detecting the actual oxygen concentration value PVo2 in the combustion furnace in real time;

[0008] a gas flow meter for detecting the actual gas flow value PVgas in real time;

[0009] an air flow meter for detecting the actual air flow value PVair in real time;

[0010] a gas control valve for adjusting and controlling the gas flow;

[0011] an air control valve for adjusting and controlling the air flow;

[0012] a controller connected with the temperature sensor, the oxygen sensor, the gas flow meter, the air flow meter, the gas control valve and the air control valve respectively, wherein the gas flow meter and the air flow meter send the detected real-time flow to the controller, the controller compares and analyzes the actual flow and the set flow, and sends a control signal to the gas control valve and the air control valve;

[0013] The control method comprises:

[0014] Before the system starts, the temperature set value SPtemp is equal to the temperature actual value PVtemp, the gas demand SPgas is 0, the gas flow actual value PVgas is 0, the air flow actual value PVair is 0, and the set air-fuel ratio R is set;

[0015] The temperature control step further comprises a temperature rising control step and a temperature falling control step;

[0016] The temperature rising control step comprises:

[0017] Step A1, the system starts, the temperature set value SPtemp is set to a target value greater than the temperature actual value PVtemp, and the gas demand SPgas matched with the temperature set value SPtemp is obtained;

[0018] Step A2, the system obtains the air flow set value SPoutair according to cross-limiting calculation, SPoutair = MAX[SPgas, PVgas]*R;

[0019] Step A3, air control analysis is entered, and the air control valve is opened according to the analysis and calculation of the air flow actual value PVair and the air flow set value SPoutair, and the air flow actual value PVair gradually rises to the air flow set value SPoutair;

[0020] Step A4, the system obtains the gas flow set value SPoutgas according to cross-limiting calculation, SPoutgas = MIN[PVair / R, SPgas];

[0021] Step A5, gas control analysis is entered, and the gas control valve is opened according to the analysis and calculation of the gas flow actual value PVgas and the gas flow set value SPoutgas, and the gas flow actual value PVgas gradually rises to the gas flow set value SPoutgas;

[0022] Step A6, after the system runs for a time t, oxygen concentration control analysis is involved, the air-fuel ratio R is calculated according to the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2, and the initial set value of the air-fuel ratio R is replaced;

[0023] Step A7, it is judged whether the deviation value of the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2 is greater than the allowed set value,

[0024] If yes, the air flow set value SPoutair = MIN[MAX[SPgas, PVgas]*R, PVgas*R+M], wherein M is the maximum air excess value;

[0025] If no, step A2 is re-entered;

[0026] The temperature control step comprises:

[0027] Step B1, setting the temperature set value SPtemp to a target value less than the temperature actual value PV-temp, and obtaining the gas demand SPgas matching the temperature set value SPtemp;

[0028] Step B2, the system obtains the gas flow set value SPoutgas according to the cross-limiting calculation, SPoutgas=MIN[PVair / R, SPgas];

[0029] Step B3, entering the gas control analysis, and adjusting the gas control valve according to the analysis calculation of the gas flow actual value PVgas and the gas flow set value SPoutgas, so that the gas flow actual value PVgas gradually decreases to the gas flow set value SPoutgas;

[0030] Step B4, the system obtains the air flow set value SPoutair according to the cross-limiting calculation, SPoutair=MAX[SPgas, PVgas]*R;

[0031] Step B5, entering the air control analysis, and adjusting the air control valve according to the analysis calculation of the air flow actual value PVair and the air flow set value SPoutair, so that the air flow actual value PVair gradually decreases to the air flow set value SPoutair;

[0032] Step B6, judging whether the deviation value of the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2 is greater than the allowed set value,

[0033] If yes, the gas flow set value SPoutgas=MAX{MIN[PV air / R, SP gas ],SP gas -N},wherein N is the maximum gas loss value;

[0034] If no, re-entering step B2.

[0035] By adopting the technical scheme of the present application, when the gas demand changes sharply, the gas and air can be ensured to rise / drop proportionally from the current stable flow, and the air amount is always slightly more than the gas amount, so that the combustion is ensured to be sufficient. When the air amount is insufficient, the gas amount can be ensured not to be excessive, so that the incomplete combustion and black smoke are avoided. When the gas amount is insufficient, the air amount can be ensured not to be excessive, so that the energy waste caused by excessive air is avoided.

[0036] Further, the system defaults the maximum gas loss value N=1 / 10 of the gas flow corresponding to the maximum power of the gas appliance, and the system defaults the maximum air excess value M=N*R.

[0037] By adopting the preferred scheme, the ascending and descending steps are optimized, which helps to maximize the saving of gas consumption.

[0038] Further, in the temperature rising control step, the maximum air excess value M is increased to increase the ascending range and speed of the gas and air flow;

[0039] In the temperature falling control step, the maximum gas deficiency value N is increased to increase the descending range and speed of the gas and air flow.

[0040] By adopting the preferred scheme, the adjustment is simple and convenient, and the user can adjust the ascending and descending steps according to the requirements to meet different use requirements of the user.

[0041] Further, in step A6, the air-fuel ratio R is adjustable between 9 and 15, the initial value of the air-fuel ratio R is 11, and the oxygen concentration setting value SPo2 is 3%.

[0042] When the actual value of the oxygen concentration PVo2 is greater than 3%, the air-fuel ratio R is less than 11;

[0043] When the actual value of the oxygen concentration PVo2 is less than 3%, the air-fuel ratio R is greater than 11.

[0044] By adopting the preferred scheme, the air-fuel ratio is finely adjusted to achieve a more ideal combustion effect, reduce energy consumption, and reduce product cost.

[0045] Further, in step A6, the oxygen concentration control analysis intervention is after the system runs for 60 seconds.

[0046] By adopting the preferred scheme, the oxygen concentration control analysis intervention timing is provided, which helps to establish a more stable oxygen concentration environment in the combustion furnace.

[0047] Further, the control system further comprises an alarm device, which alarms when the controller detects that the gas or air exceeds the allowable deviation value.

[0048] Further, the controller is provided with a timing device.

[0049] Further, the control system is provided with a gas high and low limit alarm function, including: a high-high limit alarm GASHH, a high limit alarm GASH, a low limit alarm GASL, and a low-low limit alarm GASLL alarm mode.

[0050] GASDEV = SPgas - PVgas, E = allowable deviation value of the gas,

[0051] When GASDEV > 2E, the timer counts for 60 seconds to trigger the GASLL alarm;

[0052] When GASDEV > E, the timer triggers the GASL alarm after 60S;

[0053] When GASDEV > E, the timer triggers the GASL alarm after 60S;

[0054] When GASDEV > E, the timer triggers the GASL alarm after 60S;

[0055] Further, the control system is provided with air high-low limit alarm function, including: high-high limit alarm AIRHH, high limit alarm AIRH, low limit alarm AIRL, low-low limit alarm AIRLL alarm mode,

[0056] AIRDEV = R*SPgas-PVair, F = air allowed deviation value,

[0057] When AIRDEV > 2F, the timer triggers the AIRLL alarm after 60S;

[0058] When AIRDEV > 2F, the timer triggers the AIRLL alarm after 60S;

[0059] When AIRDEV > 2F, the timer triggers the AIRLL alarm after 60S;

[0060] When AIRDEV > 2F, the timer triggers the AIRLL alarm after 60S.

[0061] Further, the alarm device is a buzzer and / or an indicator light, the buzzer has different sounds for different dangerous levels, and the indicator light has different flashing frequencies or colors for different dangerous levels.

[0062] With the above preferred scheme, a relatively rich alarm mode is provided, which helps the operating personnel to understand the running state of the combustion furnace in time. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0064] Figure 1 is a structural block diagram of the control system of the present application.

[0065] Figure 2 is a general control flowchart of the present application.

[0066] Figure 3 This is the control logic diagram of the present invention.

[0067] Figure 4 This is one of the actual operation data curves of this invention.

[0068] Figure 5 This is the second graph showing the actual operating data of this invention.

[0069] The numbers and letters in the diagram represent the names of the corresponding components: Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] One embodiment of the present invention is as follows: Figure 1 As shown, the control system of the combustion furnace includes:

[0072] A temperature sensor is used to detect the actual temperature value PVtemp inside the combustion furnace in real time;

[0073] An oxygen sensor is used to detect the actual oxygen concentration (PVo2) in the combustion furnace in real time.

[0074] Gas flow meter, used to detect the actual gas flow rate PVgas in real time;

[0075] An air flow meter is used to detect the actual air flow rate PVair in real time.

[0076] Gas control valve, used to regulate and control gas flow;

[0077] An air control valve is used to regulate and control the airflow.

[0078] like Figure 2 , 3 As shown, a dual-cross-limited combustion ratio control method, based on the above control system, includes the following: before system startup, the temperature setpoint SPtemp is equal to the actual temperature PVtemp, the gas demand SPgas is 0, the actual gas flow rate PVgas is 0, the actual air flow rate PVair is 0, and the air-fuel ratio R is set.

[0079] It also includes heating control steps and cooling control steps;

[0080] The temperature control steps include:

[0081] Step A1, the system starts to start, the temperature set value SPtemp is set to a target value greater than the temperature actual value PVtemp, and the gas demand amount SPgas matched with the temperature set value SPtemp is obtained;

[0082] Step A2, the system obtains the air flow set value SPoutair according to cross-limiting calculation, SPoutair = MAX[SPgas, PVgas] * R;

[0083] Step A3, air control analysis is entered, PID operation is performed, and the air control valve is slowly opened according to the analysis and calculation of the air flow actual value PVair and the air flow set value SPoutair, and the air flow actual value PVair gradually rises to the air flow set value SPoutair;

[0084] Step A4, the system obtains the gas flow set value SPoutgas according to cross-limiting calculation, SPoutgas = MIN[PVair / R, SPgas];

[0085] Step A5, gas control analysis is entered, PID operation is performed, and the gas control valve is slowly opened according to the analysis and calculation of the gas flow actual value PVgas and the gas flow set value SPoutgas, and the gas flow actual value PVgas gradually rises to the gas flow set value SPoutgas;

[0086] Step A6, after the system runs for a length of time t, oxygen concentration control analysis is involved, the air-fuel ratio R is calculated according to the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2, and the initial set value of the air-fuel ratio R is replaced;

[0087] Step A7, it is judged whether the deviation value of the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2 is greater than the allowed set value,

[0088] If yes, the air flow set value SPoutair = MIN[MAX[SPgas, PVgas] * R, PVgas * R + M], wherein M is the maximum air excess value;

[0089] If no, step A2 is re-entered;

[0090] The cooling control step comprises:

[0091] Step B1, the temperature set value SPtemp is set to a target value less than the temperature actual value PVtemp, and the gas demand amount SPgas matched with the temperature set value SPtemp is obtained;

[0092] Step B2, the system calculates the gas flow set value SPoutgas according to the cross-limiting amplitude, SPoutgas = MIN[PVair / R, SPgas];

[0093] Step B3, the gas control analysis is entered, the PID operation is carried out, the gas control valve is adjusted according to the analysis and calculation of the gas flow actual value PVgas and the gas flow set value SPoutgas, and the gas flow actual value PVgas gradually decreases to the gas flow set value SPoutgas.

[0094] Step B4, the system calculates the air flow set value SPoutair according to the cross-limiting amplitude, SPoutair = MAX[SPgas, PVgas]*R.

[0095] Step B5, the air control analysis is entered, the PID operation is carried out, the air control valve is adjusted according to the analysis and calculation of the air flow actual value PVair and the air flow set value SPoutair, and the air flow actual value PVair gradually decreases to the air flow set value SPoutair.

[0096] Step B6, whether the deviation value of the oxygen concentration set value SPo2 and the oxygen concentration actual value PVo2 is greater than the allowed set value is judged.

[0097] If yes, the gas flow set value SPoutgas = MAX{MIN[PV air / R, SP gas ], SP gas -N}, wherein N is the maximum gas loss value.

[0098] If no, step B2 is re-entered.

[0099] The beneficial effects of the above technical scheme are as follows: when the gas demand changes sharply, the gas and air can be ensured to rise / drop proportionally from the current stable flow, and the air amount is always slightly more than the gas amount, so that sufficient combustion is ensured. When the air amount is insufficient, the gas amount can be ensured not to be excessive, so that black smoke caused by insufficient combustion is avoided. When the gas amount is insufficient, the air amount can be ensured not to be excessive, so that energy waste caused by excessive air is avoided.

[0100] In other embodiments of the present application, the system default maximum gas loss value N = 1 / 10 of the gas flow corresponding to the maximum power of the gas appliance, and the system default maximum air excess value M = N*R. The beneficial effects of the above technical scheme are as follows: a relatively optimal rising / dropping step is provided, which is helpful to maximize the saving of gas consumption.

[0101] In other embodiments of the present application,

[0102] In the temperature increasing control step, the maximum air surplus value M is increased to increase the amplitude and speed of the air and gas flow increase;

[0103] In the temperature decreasing control step, the maximum gas deficiency value N is increased to increase the amplitude and speed of the air and gas flow decrease.

[0104] The beneficial effects of the above technical solution are: simple and convenient adjustment, which facilitates users to adjust the step amplitude according to the needs and meet different use requirements of users.

[0105] As shown in the actual operation data curve diagram of the present application, Figure 4 the corresponding parameters are:

[0106] The maximum air surplus value M is 110.

[0107] The maximum gas deficiency value N is 5.

[0108] The air-fuel ratio R set value is 11.

[0109] As shown in the actual operation data curve diagram of the present application, Figure 5 the corresponding parameters are:

[0110] The maximum air surplus value M is 200.

[0111] The maximum gas deficiency value N is 20.

[0112] The air-fuel ratio R set value is 11.

[0113] Figure 4 、 Figure 5 Midline type:

[0114] AIR ACT: air flow actual value;

[0115] AIR SP OUT: air flow set value;

[0116] GAS ACT: gas flow actual value;

[0117] GAS SP IN: gas demand;

[0118] GAS SP OUT: gas flow set value.

[0119] In some other embodiments of the present application, the opening control of the air control valve in steps A3 and B5 and the opening control of the gas control valve in steps A5 and B3 are based on the PID control method for operation, so that the control is faster and more stable.

[0120] In some other embodiments of the present application,

[0121] In step A6, the air-fuel ratio R is adjustable between 9-15, the initial setting value of the air-fuel ratio R is 11, and the oxygen concentration setting value SPo2 is 3%;

[0122] When the oxygen concentration actual value PVo2 exceeds 3%, the air-fuel ratio R is less than 11;

[0123] When the oxygen concentration actual value PVo2 is less than 3%, the air-fuel ratio R is greater than 11.

[0124] The beneficial effects of the above technical solution are: through fine adjustment of the air-fuel ratio, a more ideal combustion effect is achieved, energy consumption is reduced, and product cost is reduced.

[0125] In other embodiments of the present application, in step A6, the oxygen concentration control analysis intervention is after the system runs for 60 seconds. The beneficial effects of the above technical solution are: providing a better oxygen concentration control analysis intervention opportunity, which helps to establish a more stable oxygen concentration environment in the combustion furnace.

[0126] In other embodiments of the present application, the control system further comprises an alarm device, which alarms when the controller detects that the gas or air exceeds the allowable deviation value.

[0127] In other embodiments of the present application, a timing device is provided in the controller.

[0128] In other embodiments of the present application, the control system is provided with a gas high-low limit alarm function, including: a high-high limit alarm GASHH, a high limit alarm GASH, a low limit alarm GASL, and a low-low limit alarm GASLL alarm mode,

[0129] GASDEV = SPgas - PVgas, E = allowable deviation value of the gas,

[0130] When GASDEV > 2E, the timer counts 60S and triggers the GASLL alarm;

[0131] When GASDEV > E, the timer counts 60S and triggers the GASL alarm;

[0132] When GASDEV <-E, the timer counts 60S and triggers the GASH alarm;

[0133] When GASDEV <-2E, the timer counts 60S and triggers the GASHH alarm.

[0134] In other embodiments of the present application, the control system is provided with an air high-low limit alarm function, including: a high-high limit alarm AIRHH, a high limit alarm AIRH, a low limit alarm AIRL, and a low-low limit alarm AIRLL alarm mode,

[0135] AIRDEV = R*SPgas - PVair, F = the allowed deviation value for air,

[0136] When AIRDEV > 2F, the timer counts 60S to trigger AIRLL alarm;

[0137] When AIRDEV > F, the timer counts 60S to trigger AIRL alarm;

[0138] When AIRDEV < -F, the timer counts 60S to trigger AIRH alarm;

[0139] When AIRDEV < -2F, the timer counts 60S to trigger AIRHH alarm.

[0140] In some other embodiments of the present application, the alarm device is a buzzer and / or an indicator light, the buzzer has different sounds for different dangerous levels, the indicator light has different flashing frequencies or colors for different dangerous levels. The above technical solution has the beneficial effects of providing more abundant alarm modes, which helps the operators to understand the running state of the combustion furnace in time.

[0141] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A dual-cross-limited combustion ratio control method, characterized in that, Based on the control system, the control system includes: A temperature sensor is used to detect the actual temperature value PVtemp inside the combustion furnace in real time; An oxygen sensor is used to detect the actual oxygen concentration (PVo2) in the combustion furnace in real time. Gas flow meter, used to detect the actual gas flow rate PVgas in real time; An air flow meter is used to detect the actual air flow rate PVair in real time. Gas control valve, used to regulate and control gas flow; An air control valve is used to regulate and control the airflow. The controller is connected to a temperature sensor, an oxygen sensor, a gas flow meter, an air flow meter, a gas control valve, and an air control valve. The gas flow meter and air flow meter send the detected real-time flow to the controller. The controller compares and analyzes the actual flow and the set flow, and sends the control signal to the gas control valve and the air control valve. The control method includes: Before system startup, the temperature setpoint SPtemp is equal to the actual temperature PVtemp, the gas demand SPgas is 0, the actual gas flow rate PVgas is 0, the actual air flow rate PVair is 0, and the air-fuel ratio R is set. It also includes heating control steps and cooling control steps; The temperature control steps include: Step A1: The system starts up and sets the temperature setpoint SPtemp to a target value that is greater than the actual temperature value PVtemp. Based on the temperature setpoint SPtemp, the corresponding gas demand SPgas is obtained. Step A2: The system calculates the airflow setpoint SPoutair based on the cross-limit calculation, SPoutair = MAX[SPgas, PVgas]*R; Step A3: Enter air control analysis. Based on the actual air flow value PVair and the air flow setpoint SPoutair, the air control valve opens, and the actual air flow value PVair gradually increases towards the air flow setpoint SPoutair. Step A4: The system calculates the gas flow setpoint SPoutgas based on the cross-limit calculation, SPoutgas = MIN[PVair / R, SPgas]; Step A5: Enter gas control analysis. Based on the actual gas flow value PVgas and the gas flow setpoint SPoutgas, the gas control valve opens and the actual gas flow value PVgas gradually increases towards the gas flow setpoint SPoutgas. Step A6: After the system has been running for a duration of t, the oxygen concentration control analysis is initiated. Based on the oxygen concentration setpoint SPo2 and the actual oxygen concentration value PVo2, the air-fuel ratio R is calculated and the initial setpoint of the air-fuel ratio R is replaced. Step A7: Determine whether the deviation between the oxygen concentration setpoint SPo2 and the actual oxygen concentration PVo2 is greater than the allowable setpoint. If so, the air flow setpoint SPoutair = MIN[MAX[SPgas, PVgas]*R, PVgas*R+M], where M is the maximum excess air value; If not, proceed to step A2 again; The cooling control steps include: Step B1: Set the temperature setpoint SPtemp to a target value that is less than the actual temperature value PV-temp, and obtain the matching gas demand SPgas based on the temperature setpoint SPtemp. Step B2: The system calculates the gas flow setpoint SPoutgas based on the cross-limit calculation, SPoutgas = MIN[PVair / R, SPgas]; Step B3: Enter gas control analysis. Based on the actual gas flow rate PVgas and the set gas flow rate SPoutgas, the gas control valve is adjusted, and the actual gas flow rate PVgas gradually decreases towards the set gas flow rate SPoutgas. Step B4: The system calculates the airflow setpoint SPoutair based on the cross-limit calculation, SPoutair = MAX[SPgas, PVgas]*R; Step B5: Enter air control analysis. Based on the actual air flow value PVair and the air flow setpoint SPoutair, the air control valve is adjusted, and the actual air flow value PVair gradually decreases towards the air flow setpoint SPoutair. Step B6: Determine whether the deviation between the oxygen concentration setpoint SPo2 and the actual oxygen concentration PVo2 is greater than the allowable setpoint. If so, the gas flow setpoint SPoutgas = MAX{ MIN[PVair / R, SPgas], SPgas-N}, where N is the maximum gas shortage value; If not, proceed to step B2; In the heating control step, the magnitude and speed of the increase in gas and air flow are increased by increasing the maximum excess air value M; In the cooling control step, the magnitude and speed of the decrease in gas and air flow are increased by increasing the maximum gas shortage value N.

2. The dual-cross-limited combustion ratio control method according to claim 1, characterized in that, The system's default maximum gas shortage value N = 1 / 10 of the gas flow rate corresponding to the gas appliance's maximum power, and the system's default maximum excess air value M = N*R.

3. The dual-cross-limited combustion ratio control method according to claim 1, characterized in that, In step A6, the air-fuel ratio R is adjustable between 9 and 15, with an initial setting of 11 for the air-fuel ratio R and an oxygen concentration setting of 3% for SPo2. When the actual oxygen concentration PVo2 exceeds 3%, the air-fuel ratio R is less than 11. When the actual oxygen concentration PVo2 is less than 3%, the air-fuel ratio R is greater than 11.

4. The dual-cross-limited combustion ratio control method according to claim 3, characterized in that, In step A6, the oxygen concentration control analysis is initiated 60 seconds after the system has been running.

5. The dual-cross-limited combustion ratio control method according to claim 1, characterized in that, The control system also includes an alarm device that triggers an alarm when the controller detects that the gas or air exceeds the allowable deviation value.

6. The dual-cross-limited combustion ratio control method according to claim 5, characterized in that, The controller is equipped with a timing device; The control system is equipped with gas high and low limit alarm functions, including: high-high limit alarm GASHH, high limit alarm GASH, low limit alarm GASL, and low-low limit alarm GASLL alarm modes. Let GASDEV = SPgas - PVgas, and E = permissible deviation value of gas. When GASDEV > 2E, the timer will trigger the GASLL alarm after 60 seconds. When GASDEV > E, the GASL alarm is triggered after the timer counts for 60 seconds. When GASDEV <-E, the timer will trigger a GASH alarm after 60 seconds. When GASDEV < -2E, the timer triggers a GASHH alarm after 60 seconds.

7. The dual-cross-limited combustion ratio control method according to claim 6, characterized in that, The control system is equipped with high and low air level alarm functions, including: High-High Alarm AIRHH, High Alarm AIRH, Low Alarm AIRL, and Low-Low Alarm AIRL. Let AIRDEV = R * SPgas - PVair, where F = permissible deviation of air pressure. When AIRDEV > 2F, the timer will trigger the AIRLL alarm after 60 seconds. When AIRDEV > F, the timer will trigger the AIRL alarm after 60 seconds. When AIRDEV <-F, the timer will trigger the AIRH alarm after 60 seconds. When AIRDEV < -2F, the timer will trigger the AIRHH alarm after 60 seconds.

8. The dual-cross-limited combustion ratio control method according to claim 7, characterized in that, The alarm device is a buzzer and / or an indicator light. The buzzer sounds differently for different hazard levels, and the indicator lights flash at different frequencies or have different colors for different hazard levels.

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