CN115645802A - Integrated compressed air foam fire extinguishing system and control method thereof - Google Patents

Abstract

The invention discloses an integrated compressed air foam fire extinguishing system and a control method thereof, comprising a control center, a foam generator, a three-way input unit and a power supply module; It also includes a spare air input unit as a backup of the air input unit; the control center controls the flow of the three input units to make compressed air, foam stock solution and water mixed in the foam generator to produce compressed air foam , and then output compressed air foam. The present invention makes the compressed air fire extinguishing system operate more stably and reliably by proposing a control method of the system, which has certain practical significance.

Description

An integrated compressed air foam fire extinguishing system and its control method

technical field

The invention belongs to the technical field of industrial automation fire protection, and in particular relates to an integrated compressed air foam fire extinguishing system, and also relates to a control method of the system.

Background technique

Compressed Air Foam System (CAFS, Compressed Air Foam System) is a new type of fire extinguishing system that has developed rapidly abroad in recent years. Because of its high fire extinguishing efficiency, it can realize fire extinguishing of various types of fires and is widely used. However, the traditional CAFS is composed of multiple modules, and the integration level is not high, resulting in a large footprint and high cost; in addition, the foaming principle inside the compressed air foam fire extinguishing system and the dynamic control of the equipment are the core of the entire system. How to quickly and stably produce foam that meets the requirements of fire extinguishing has become a difficult point in system development, but there is little research on the design of CAFS equipment controllers. At present, some basic PID controllers for CAFS equipment have been proposed, but they cannot be flexible. For problems in various working conditions, and basically only adjust the foam circuit and air circuit, but not the water circuit. However, the size of the water flow will also affect the dynamic stability of the entire system. Therefore, the PID controller of the water circuit Design is equally important.

Contents of the invention

The purpose of the present invention is to provide an integrated compressed air foam fire extinguishing system and its control method, which solves the problem that the flexible adaptability of current CAFS equipment to various working conditions and the adjustment of waterways need to be further optimized.

A technical scheme adopted in the present invention is;

An integrated compressed air foam fire extinguishing system, including a control center for controlling the entire system, a power supply, an air circuit, a water pipeline, a foam circuit and an external backup air compressor;

The air compressor in the air circuit is connected to the foam generator through the air pipeline, and the air pipeline is equipped with a one-way valve and a pressure regulating valve; the foam circuit is equipped with a foam pump, and the foam circuit is connected to the first valve of the three-way ball valve through the foam pipeline. The water channel is connected to the second channel of the three-way ball valve through the water pipeline, and the water pipeline is equipped with a frequency conversion centrifugal pump and a water flow meter; the third channel of the three-way ball valve is connected to the foam generator through the mixing pipe; the water and the foam liquid are mixed The mixed liquid is mixed in the tube; a pressure sensor is arranged at the front end of the foam generator, the mixed liquid and air are mixed in the foam generator to form a compressed air foam solution, and the compressed air foam solution is output through an electric butterfly valve; the spare air compressor is used as a backup, It is connected to the air line through a one-way valve.

Another technical solution of the present invention is;

The control method of the system specifically includes the following steps:

Step 1. First determine the size of the water flow. There is a first-order inertia link relationship between the water flow and the foam flow. After the water flow is determined, the foam solution flow can be determined; after the water flow is determined, the frequency conversion centrifugal pump starts to work, and the water flow The meter starts to detect the size of the water flow, and there is a PID controller in the waterway. By comparing the measured output water flow through the pump transfer function K1 with the given water flow, the error signal obtained is used as the input of the PID controller, and then Use the PID controller of the waterway to adjust the frequency conversion centrifugal pump in the waterway to change the size of the water flow, and then realize the constant water flow and pressure under the condition of fixed gas-liquid ratio;

Step 2. After the water flow meter detects the change of water flow, the foam pump starts to work, and the foam solution is delivered to the foam road according to the preset flow index, and the flow of the foam solution is controlled by the PID controller of the foam road , this process is to compare the actual output flow rate of the foam circuit with the given foam liquid flow rate after passing through the foam pump transfer function K2, and use the difference between the two as the input of the PID controller, and the output of the PID controller has an effect on the foam pump Carry out control, and then automatically adjust the size of the foam solution flow, so as to maintain the output of the foam circuit unchanged;

Step 3. While performing steps 1 and 2, the foam solution and water are mixed through the pipeline before entering the mixing chamber. According to the characteristics of the infusion pipeline, the pressure of the mixed solution can be obtained through the pressure sensor. The liquid ratio can calculate the given air flow, and the calculated air flow can be converted into air pressure through the characteristics of the check valve. There is also a first-order inertia link relationship between the air pressure and the mixed liquid pressure, so through the The relationship between the foam solution, water and air can be determined by the characteristics of the road, the characteristics of the one-way valve and the gas-liquid ratio;

Step 4. After the air flow is determined, the given air pressure is obtained through conversion, and there is also a PID controller in the air circuit to adjust the constant air pressure of the air circuit. This process is to compare the actual output air pressure with the given input air pressure. After the error signal is generated by the comparison link, the error signal is used as the input of the PID controller, and the output of the PID controller controls the one-way valve. The system input is compared and the gas phase pressure is automatically adjusted to maintain a constant pressure.

The present invention is also characterized in that;

In step 1, the flow index of the output compressed air foam is formulated according to the foam mixing ratio R _FW by dividing the foam flow and water flow into 1%, 3%, and 6% equal proportions according to the properties of the foam stock solution, so it can be determined The PID control algorithm of the water flow in the waterway is shown in the following formula (1):

In step 2, the details of the foam road PID algorithm are as follows:

According to the foam mixing ratio R _FW , the foam flow rate and the water flow rate are divided into 1%, 3%, 6% and mixed in equal proportions according to the properties of the foam stock solution as shown in the following formulas (2) and (3):

Among them, Q _F is the foam flow rate, and Q _W is the water flow rate.

In step 4, the air path PID algorithm is specifically as follows:

According to the gas-liquid ratio R _AH , the air with a gas-liquid ratio of 4:1 or 3:1 or 6:1 is mixed with the foam mixture to produce the foam quality required for fire extinguishing, and the PID algorithm for the air path can be obtained for the fire extinguishing requirements details as follows:

Among them, the gas-liquid ratio R _AH is the ratio of the gas flow to the liquid flow, Q _A is the air flow, Q _H is the superimposed flow of the foam stock solution and water, and the gas-liquid ratio R _AH is the ratio of the air flow Q _A to the mixed liquid flow Q _H ;

The ratio of the pressure detected by the air pressure sensor and the mixing chamber pressure sensor:

P _A = KP _H (5);

Wherein, _PA is air pressure, and _PH is the pressure after mixing of water and foam solution;

From the above, the gas-liquid ratio can be adjusted by adjusting the K value, wherein:

1.0≤K≤1.15(6);

Using this relationship can ensure that the air and foam mixture are fully mixed, so that compressed air foam suitable for various fire scenarios can be produced by changing the K value.

The beneficial effects of the present invention are that the integrated compressed air foam fire extinguishing system and its control method of the present invention, compared with the prior art, not only integrate the air compressor, foam pump, water pump, and control and power supply modules together , to a certain extent, the size is reduced and the cost is saved, and the reliability of the system operation is greatly improved. At the same time, a spare port is reserved outside the equipment for the connection of an external air compressor to improve the input capacity of the system; in addition, the adopted control The method is a new type of PQ control in the multi-PI adjustment mode. On the basis of some existing control algorithms that only adjust the foam circuit and the air circuit, the control of the water circuit is added, so that the three-way PID controller jointly adjusts Under certain circumstances, the output of the system is more accurate, which fully meets the requirements of fire extinguishing.

Description of drawings

Fig. 1 is a system block diagram of a kind of integrated compressed air foam fire extinguishing system of the present invention;

Fig. 2 is the principle block diagram of waterway PID in a kind of integrated compressed air foam fire extinguishing system of the present invention;

Fig. 3 is the functional block diagram of foam road PID in a kind of integrated compressed air foam fire extinguishing system of the present invention;

Fig. 4 is a functional block diagram of the air circuit PID in an integrated compressed air foam fire extinguishing system of the present invention

Fig. 5 is a control logic block diagram of PID in an integrated compressed air foam fire extinguishing system of the present invention.

In the figure, 1. Water inlet, 2. Foam liquid injection port, 3. Compressed air foam liquid output port, 4. Frequency conversion centrifugal pump, 5. Foam pump, 6. Three-way ball valve, 7. Pressure sensor, 8. Electric motor Butterfly valve, 9. Pressure regulating valve, 10. One-way valve, 11. Air compressor, 12. Control center, 13. Power supply, 14. Foam generator, 15. Water flow meter, 16. Spare air compressor.

Detailed ways

An integrated compressed air foam fire extinguishing system and its control method of the present invention will be described in detail below in conjunction with the drawings and specific embodiments.

An integrated compressed air foam fire extinguishing system of the present invention, as shown in Figure 1, includes a foam generator, a power supply, an air compressor, a foam pump, a variable frequency centrifugal pump, a control center, a pressure sensor, and various valves and pipelines; The air compressor 11 of the air circuit is connected to the foam generator 14 through the pressure regulating valve 9 and the one-way valve 10, and the water pipe is connected to one end of the three-way ball valve 6 through the frequency conversion centrifugal pump 4, and the other end is connected to the foam pump 5. After mixing in the pipeline, it is also connected to the foam generator 14 through the pipeline, wherein a water flow meter 15 is connected to the water circuit to detect the water flow rate, and there is a pressure sensor 7 at the front end of the foam generator to detect the pressure of the mixed liquid , the three are finally mixed in the foam generator 14 to form a compressed air foam solution that is output through the electric butterfly valve 8, and the external backup air compressor 16 is connected to the foam generator through the one-way valve 10 for backup.

As shown in Figure 2, the relevant process of the control algorithm of the control center of the system; the first step: get the water flow according to the CAFS flow standard, and there is a quantitative relationship between the water flow and the foam solution flow, thus the foam solution flow can be obtained, At the same time, the air flow rate can be obtained according to the gas-liquid ratio; the second step: while adjusting the air path foam path, the water flow in the water path is also in a dynamic change due to the air flow rate and the foam flow rate, so the water flow rate measured by the water flow meter The flow rate is compared with the set value, and the resulting difference is also sent to the waterway PID controller, and then the frequency conversion centrifugal pump in the waterway is adjusted to achieve the adjustable water flow rate to achieve the set goal.

As shown in Figure 3, after the water flow is calculated according to the flow index, the actual foam liquid flow output by the foam path is compared with the expected foam liquid flow according to the quantitative relationship between the water flow and the foam solution flow, and the difference is sent to the foam In the PID controller of the liquid circuit, the foam pump is adjusted through the output of the PID controller to reduce the output error of the foam liquid and make it reach the expected target.

As shown in Figure 4, there is a conversion relationship between the air flow and air pressure through the characteristics of the check valve, and there is also a certain algorithm relationship between the air pressure and the pressure of the mixed liquid, so the actual air pressure and the preset value For comparison, the difference is used as the input of the PID controller of the air circuit, and then the proportional valve and the check valve are controlled through the output of the PID controller, and the air pressure is adjusted to achieve the expected setting goal.

As shown in Figure 5, the normal operation mode of the control process, the first step: first start the air circuit, water circuit and output channel, that is, start the air compressor, centrifugal pump, and outlet valve, and follow the three-stage operation mode for the opening of the foam circuit , that is, firstly, the tuning fork sensor is used to detect whether there is residual foam liquid, and then the foam pump is turned on, the three-way ball valve is set, and the foam circuit is connected; the second step is to calculate the foam liquid on the one hand after measuring the water flow rate through the water flow meter. Flow rate, convert the calculated foam liquid flow into an analog quantity and send it to the servo motor. The servo motor executes the operation instruction of the foam stock solution, and then the foam flow detector in the foam road detects whether the target foam volume is reached. If it does not reach the set The value is returned to recalculate the foam solution flow; the third step: while the foam circuit unit is executing, the water flow detected by the water flow meter is converted into an analog quantity and sent to the variable frequency centrifugal pump, and the adjustment is realized by adjusting the speed of the pump The size of the water flow is checked by the water flow meter to see if the water flow is up to the standard. If it is not up to the standard, return to recalculate the water flow; the fourth step: After the water path and the foam path are mixed, the pressure of the aqueous solution is measured by the pressure sensor, and the corresponding value is calculated. The required air pressure is converted into an analog quantity and sent to the electric proportional valve to adjust the pressure reducing valve to control the air pressure of the entire circuit. Finally, the pressure transmitter is used to detect whether the air pressure reaches the target value. If not, return to continue calculation Required air pressure; Step 5: If the three unit algorithms of air, water, and foam are executed correctly and all meet the target setting, then judge the fire alarm situation. If the alarm situation is cleared, set the three-way ball valve again to Close the foam circuit and water circuit, then close the foam pump, air compressor and centrifugal pump, and finally close the outlet valve to end the operation of the equipment. If the fire alarm is not cleared, return to the second step to continue.

The present invention is an integrated compressed air foam fire extinguishing system and its control method. According to the mutual influence relationship between the air flow and pressure of the foam fire extinguishing system; the flow and pressure of foam raw liquid; the flow and pressure of water, a new control method is proposed, It has certain practical significance to make the compressed air fire extinguishing system run more stably and reliably.

Claims (5)

1. An integrated compressed air foam fire extinguishing system is characterized in that it comprises a control center (12) for controlling the whole system, a power supply (13), air way, water way, foam way and an external backup air compressor machine (16); The air compressor (11) of the air circuit is connected to the foam generator (14) through the air pipeline, and the air pipeline is equipped with a check valve (10) and a pressure regulating valve (9); There is a foam pump (5), and the foam circuit is connected to the first pass of the three-way ball valve (6) through the foam pipeline; the water circuit is connected to the second pass of the three-way ball valve (6) through the water pipeline, and the water pipe The road is equipped with a frequency centrifugal pump (4) and a water flow meter (15); the third pass of the three-way ball valve (6) is connected to the foam generator (14) through a mixing pipe; water and foam liquid are mixed in the mixing pipe Form a mixed solution; a pressure sensor (7) is arranged at the front end of the foam generator (14), and the mixed solution and air are mixed in the foam generator (14) to form a compressed air foam solution, and the compressed air foam solution is electrodynamically The butterfly valve (8) outputs; the spare air compressor (16) is used as a spare, and it is connected to the air pipeline through the one-way valve (10). 2. A kind of integrated compressed air foam fire extinguishing system according to claim 1, is characterized in that, the control method of described system specifically comprises the following steps: Step 1. First determine the size of the water flow. There is a first-order inertia link relationship between the water flow and the foam flow. After the water flow is determined, the foam solution flow can be determined; after the water flow is determined, the frequency conversion centrifugal pump starts to work, and the water flow The meter starts to detect the size of the water flow, and there is a PID controller in the waterway. By comparing the measured output water flow through the pump transfer function K1 with the given water flow, the error signal obtained is used as the input of the PID controller, and then Use the PID controller of the waterway to adjust the frequency conversion centrifugal pump in the waterway to change the size of the water flow, and then realize the constant water flow and pressure under the condition of fixed gas-liquid ratio; Step 2. After the water flow meter detects the change of water flow, the foam pump starts to work, and the foam solution is delivered to the foam road according to the set compressed air foam output flow index, and the foam solution flow rate is realized through the PID controller of the foam road. Size control, this process is to compare the actual output flow of the foam circuit with the given foam liquid flow after passing through the foam pump transfer function K2, and use the difference between the two as the input of the PID controller, and the output of the PID controller Control the foam pump, and then automatically adjust the flow rate of the foam solution, so as to maintain the output of the foam circuit unchanged; Step 3. While performing steps 1 and 2, the foam solution and water are mixed through the pipeline before entering the mixing chamber. According to the characteristics of the infusion pipeline, the pressure of the mixed solution can be obtained through the pressure sensor. The liquid ratio can calculate the given air flow, and the calculated air flow can be converted into air pressure through the characteristics of the check valve. There is also a first-order inertia link relationship between the air pressure and the mixed liquid pressure, so through the The relationship between the foam solution, water and air can be determined by the characteristics of the circuit, the characteristics of the one-way valve and the gas-liquid ratio; Step 4. After the air flow is determined, the given air pressure is obtained through conversion, and there is also a PID controller in the air circuit to adjust the constant air pressure of the air circuit. This process is to compare the actual output air pressure with the given input air pressure. After the error signal is generated by the comparison link, the error signal is used as the input of the PID controller, and the output of the PID controller controls the one-way valve. The system input is compared and the gas phase pressure is automatically adjusted to maintain a constant pressure. 3. A kind of integrated compressed air foam fire extinguishing system according to claim 1, it is characterized in that, in step 1, the flow index of output compressed air foam is according to foam flow rate and water flow rate according to foam stock solution according to foam mixing ratio R _FW The nature of the water flow is divided into 1%, 3%, and 6% to be formulated, so that the PID control algorithm of the water flow in the waterway can be determined as shown in the following formula (1):

4. A kind of integrated compressed air foam fire extinguishing system according to claim 1, is characterized in that, in step 2, foam road PID algorithm is specifically as follows: According to the foam mixing ratio R _FW , the foam flow rate and the water flow rate are divided into 1%, 3%, and 6% according to the properties of the foam stock solution and mixed as shown in the following formulas (2) and (3):

Among them, Q _F is the foam flow rate, and Q _W is the water flow rate. 5. A kind of integrated compressed air foam fire extinguishing system according to claim 1, is characterized in that, in step 4, the air path PID algorithm is specifically as follows: According to the gas-liquid ratio R _AH , the air with a gas-liquid ratio of 4:1 or 3:1 or 6:1 is mixed with the foam mixture to produce the foam quality required for fire extinguishing, and the PID algorithm for the air path can be obtained for the fire extinguishing requirements details as follows:

Among them, the gas-liquid ratio R _AH is the ratio of the gas flow to the liquid flow, Q _A is the air flow, Q _H is the superimposed flow of the foam stock solution and water, and the gas-liquid ratio R _AH is the ratio of the air flow Q _A to the mixed liquid flow Q _H ; The ratio of the pressure detected by the air pressure sensor and the mixing chamber pressure sensor: P _A = KP _H (5); Wherein, _PA is air pressure, and _PH is the pressure after mixing of water and foam solution; Adjust the gas-liquid ratio by adjusting the K value, wherein: 1.0≤K≤1.15(6); Using this relationship can ensure that the air and foam mixture are fully mixed, so that compressed air foam suitable for various fire scenarios can be produced by changing the K value.

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