KR100490375B1 - Fire protection foam proportioner with constant mixing ratio - Google Patents

Abstract

The present invention relates to a foam proportional mixer for the fire suppression constant mixing ratio, more specifically, the mixing ratio of the foam stock solution is maintained constant according to the change in the flow characteristics of the front and rear end of the proportional mixer is a mixing ratio that can effectively suppress the fire Foam proportional mixer for constant fire suppression.

The present invention provides a low pressure generator that operates by receiving water supplied from the outside, and a proportional mixer of a foam fire extinguishing system including a mixing ratio control metering device for supplying a foam stock solution to the low pressure generator. Venturi 20, the mixing ratio control metering device is characterized in that the metering venturi 10 is connected to the neck portion of the water supply venturi 20 while having a hydrodynamic analogy with the water supply venturi 20. It is done.

Description

FIRE PROTECTION FOAM PROPORTIONER WITH CONSTANT MIXING RATIO

The present invention relates to a foam proportional mixer for the fire suppression constant mixing ratio, more specifically, the mixing ratio of the foam stock solution is maintained constant according to the change in the flow characteristics of the front and rear end of the proportional mixer is a mixing ratio that can effectively suppress the fire Foam proportional mixer for constant fire suppression. Among the changes in the flow characteristics, the change in the flow characteristics at the front of the foam proportional mixer may be a case where the pressure and flow rate of the water supplied to the foam proportional mixer are changed, and the change in the flow characteristics at the rear end of the foam proportional mixer is a foam For example, the pipe resistance of the pipe installed from the proportional mixer to the fire hydrant is changed. It is also conceivable that some of the fire hydrants operate in the case of branching into multiple fire hydrants in one form proportional mixer.

Fire extinguishing foam fire extinguishing equipment is widely used to cut off oxygen in case of fire in and out of flammable tank. It is a line proportioner type, pump proportioner type and pressure side proportional. There are Pressure Side Proportioner Types and Balanced Pressure Proportioner Types, depending on how the water and foam stock are supplied.

FIG. 2 is a schematic configuration diagram of a general foam fire extinguishing system, FIG. 3 is a schematic view of fire suppression in a tank using a general foam fire extinguishing system, and FIG. 4 is a structural diagram of a foam proportional mixer of a general foam fire extinguishing system.

The foam fire extinguishing system is largely composed of a device for supplying water, a device for supplying a foam stock solution, and a proportional mixer.

The proportional mixer 100 is formed of a water inlet 112 for supplying water, a foam stock solution inlet 118 into which the foam stock solution is sucked, and a foam mixture outlet 114 for discharging the mixed foam mixture. The water makes a lower pressure, that is, a lower pressure, than the water inlet in the throat of the low pressure generator 111. Venturi, orifice and nozzle are used as the low pressure generator, and Venturi, which has a low pressure loss, is used the most.

The foam stock solution inlet 118 is connected to a throat in which the lowest pressure of the low pressure generator 111 is generated, and the foam stock solution is mixed with water into which the water inlet 112 flows through the connector. In addition, the flow path of the foam stock solution inlet 118 has a mixing ratio adjustment metering device for adjusting (fixed at the time of installation) of the foam stock solution. The metering device uses a metering orifice 116. The diameter of the metering orifice is different depending on the mixing ratio of the foam stock solution, so that the fire hydrant requiring a large mixing ratio is larger than the small mixing ratio.

The foam (Foam) is mixed in the foam proportional mixer 100 according to the mixing ratio to determine the water and alcohol and the foam stock solution or water-soluble foam stock solution, air is introduced from the foam maker to form a foam for fire suppression, the foam is combustible Release on the liquid.

The mixing ratio of the water through the foam stock solution 120 and the water supply pipe 110 varies depending on the type of the foam and the type of the flammable fluid, and the mixing ratio is very important for the characteristics of the foam which is a fire suppression performance. Therefore, the mixing ratio should always be mixed in a constant mixing ratio in the foam proportional mixer (100).

The following is an example of the mixing ratio of the foam stock solution.

Aqueous Film-Forming Foam (AFFF) 1%, 3%, 6% Alcohol foam: ALC (Alcohol-Resistant Concentrates) 3%, 6% Protein Foam Concentrates 3%, 6% Fluoroprotein Foam Concentrates 3% High Expansion Foam Concentrates 2.75%

The mixing ratio uses the principle of sucking the foam stock solution from the neck of the low pressure generator, and the foam stock solution and water should be mixed in a constant ratio. Water flows into the low pressure generator, creating a pressure lower than the water inlet pressure in the vicinity of the small diameter, by the Berlui principle. At this low pressure, the foam stock is introduced into the foam chamber.

Water is supplied by using pressurized water or by pumping. In addition, the foam stock solution is supplied to the proportional mixer by a pump, pressurized by pressurized water, and supplied to the proportional mixer, and sucked by the low pressure generated by the Berlui principle in the proportional mixer.

On the other hand, the foam fire extinguishing system is different in size depending on the characteristics of the flammable tank 150, it is called by expressing the diameter of the inlet and outlet of the foam proportional mixer in inches (inch). General foam fire extinguishing system uses a pipe of the same diameter from the proportional mixer 100 to the foam formation. This diameter is usually equal to the nominal inch of the proportional mixer.

The mixing ratio of the foam proportional mixer 100 is usually determined according to the size of the diameter of the metering orifice in the flow path through which the foam stock solution flows. Inlet apertures are usually divided largely into 2, 3, 4, 6, and 8 inches, and mixing ratio adjustments are made with different orifice diameters. This method is used because the metering orifice plate is easily replaceable.

The foam proportional mixer 100 uses a venturi, an orifice, a nozzle, or the like, and the pressure at the throat is lower than the pressure at the inlet so as to suck the foam stock solution. The sucked foam stock should be mixed with the main stream of water at a certain ratio, but in practice the mixing ratio changes as the flow rate and pressure change. And most tanks containing flammable fluids are installed in a specific complex because they are dangerous goods. Therefore, one foam proportional mixer is installed in a combustible fluid tank having several same characteristics and branched into a smaller pipe in the branch header 140.

However, a problem arises by branching into such a small pipe. For example, assuming that a 4 inch proportional controller is installed and connected to a tank with a hydrant with a hydrant that divides a 6 inch branch header into 4 2 inch pipes, it can be said to be connected like a pipe for supplying water. Since the area ratio in the water supply branched from one 4-inch pipe to two 4-inch pipes, the sum of the cross-sectional areas of the flow paths before and after the branching is the same, and thus has been used without any problem.

But not in the foam digestive system. Generally speaking, fire does not occur in four flammable tanks at the same time. In most cases, fire occurs in two, three or four tanks. In some cases, the flow rate is only 1/4, 2/4, 3/4 or 4/4 of the normal flow rate. Although the mixing ratio of the foam stock solution according to the flow rate change does not change, in fact, the mixing ratio may be lowered to less than half, and thus there is a problem in that the fire suppression ability is lowered.

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The present invention is to solve the above problems, an object of the present invention is to provide a foam proportional mixer that can effectively suppress the fire by maintaining a constant mixing ratio of the foam stock solution in accordance with the change in flow characteristics of the front and rear of the foam proportional mixer It is. In other words, the change in flow characteristics at the front of the foam proportional mixer is one of the changes in the flow characteristics of the water supplied to the foam proportional mixer. For example, the pipe resistance of the pipe installed from the foam proportional mixer to the fire hydrant is changed. More specifically, it is conceivable that some of the fire hydrants operate in the case of branching into multiple fire hydrants in one form proportional mixer. In case that it is possible to reduce the cost of installing the foam fire and to use it in the form of diverging from one foam proportional mixer to multiple fire hydrants, the flow rate that passes through the foam proportional mixer even if a fire occurs in one or several places Adjusting the mixing ratio of foam liquid mixture according to the change The flow coefficient ratio of the metering device and the low pressure generator is constant to provide a foam proportional mixer for fire suppression in which the foam liquid mixture mixing ratio does not change.

The present invention provides a low pressure generator that operates by receiving water supplied from the outside, and a proportional mixer of a foam fire extinguishing system including a mixing ratio control metering device for supplying a foam stock solution to the low pressure generator. Venturi 20, the mixing ratio control metering device is characterized in that the metering venturi 10 is connected to the neck portion of the water supply venturi 20 while having a hydrodynamic analogy with the water supply venturi 20. It is done.

Meanwhile, the present invention provides a low pressure generator that operates by receiving water supplied from the outside, and a foam proportional mixer of a foam fire extinguishing system including a mixing ratio control metering device for supplying a foam stock solution to the low pressure generator. It is a supply nozzle, characterized in that the mixing ratio adjustment metering device is a metering nozzle connected to the water supply nozzle while having a hydrodynamic similarity with the water supply nozzle.

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With reference to the accompanying drawings will be described in detail the proportional mixer for fire suppression constant mixing ratio of the present invention.

1 is a schematic structural diagram of a foam proportional mixer for a fire suppression constant mixing ratio according to an embodiment of the present invention, Figure 4 is a conventional mixing ratio adjustment metering device commonly used metering orifice, low pressure generating device Fig. 5 is a schematic diagram of a mixer for calculating the mixing ratio according to the flow rate in a conventional metering orifice type proportional mixer using a Venturi-type low pressure generating device. It is a graph showing the change of the flow coefficient against the change of Reynolds number.

Foam proportional mixer for the fire suppression constant mixing ratio according to an embodiment of the present invention, as shown in Figure 1, the water supply venturi 20 is connected to the water supply pipe to supply water, and the water supply venturi 20 It consists of a metering venturi (10) connected to the neck of the).

It is the same as the general foam proportional mixer of the water supply venturi 20, and the metering venturi 10 preferably has a hydrodynamic similarity with the water supply venturi 20.

The present invention configured as described above is analyzed using a venturi, a mixing ratio control metering device with a conventional low pressure generator, and a mixing ratio falling in an orifice fire suppression foam proportional mixer, and the present invention allows the mixing ratio to maintain a constant value. Explain.

First, the case of branching from the mixer among the causes of the flow rate variation of the foam proportional mixer will be described as an example. It is assumed that a 4 inch foam proportional mixer is installed, and a secondary foam is installed outside the stationary foam generator and the flammable tank in three flammable tanks with 2 inch pipes in the branch header.

In the event of a fire in one combustible tank, the foam proportional mixer is 4 inches but the outlet piping is 2 inches, reducing the pipe cross section to 1/4. Thus, the flow through the foam proportional mixer is also reduced to 1/4. According to the experiment, in the case of a 495 inch foam proportional mixer with a capacity of 3595 L / min, four 2 inch pipes were branched and connected to a fire hydrant. The mixing ratio of the stock solution was determined to be 1.3%, and the mixing ratio was less than half of the minimum mixing ratio of 3%.

This test result is because the flow rate through the foam proportional mixer is too small compared to the design flow rate of the foam proportional mixer.

More specifically, the inlet aperture has a diameter of 54 mm at the Venturi neck of the 4 inch foam proportional mixer and the diameter of the metering orifice at the inlet of the foam stock solution is 11 mm. At 20 degrees Celsius, the kinematic viscosity of water is 1.0 × 10 ^-6 m ² / sec, and at 20 degrees Celsius, the kinematic viscosity of the alcohol-based aqueous film blister (AFFF / ATC) is 1.8 × 10 ^-3 m ² / sec. The Reynolds number (VD / ν) for the water flow is about 1.2 × 10 ⁶ , and the foam stock is about 114.

The large difference in the Reynolds number as described above is due to the low mixing flow rate of the foam stock solution of about 1-6%, the diameter of the orifice through which the foam stock solution flows is very small, and the viscosity of the foam stock solution is considerably larger than that of water.

On the other hand, referring to Figure 5, Pw is the inlet pressure of the venturi, the inlet of the low pressure generator, Pwt is the pressure at the neck of Venturi, the low pressure generator, Pwe is the pressure of the venturi outlet, the low pressure generator. In addition, Pc is the inlet pressure of the metering orifice, the mixing ratio regulating metering device into which the foam stock enters, Pct is the pressure at the neck of the metering orifice, and Pce is the pressure at the outlet of the metering orifice. Accordingly, the flow rate of water passing through the venturi, which is a low pressure generator, is shown in Equation 1.

Where C _w is the flow coefficient of a low pressure generator such as Venturi, and ρ _w is the density of water.

The flow of the form solution can be expressed as Equation 2.

Where C _c is the flow coefficient of the mixing ratio regulating metering device, such as the metering orifice, and ρ _c is the density of the foam stock solution.

The flow coefficient C _w of the Venturi flowing water is about 0.95 to 0.98, which is relatively small compared to the Reynolds number. However, the flow coefficient of the metering orifice through which the foam stock flows varies greatly depending on the Reynolds number as shown in FIG.

In the graph of FIG. 6, the Reynolds number of the orifice which is generally used as the flowmeter is 10 ⁴ or more, and the flow coefficient C _c at this time is about 0.6 to 0.65. However, for orders with a Reynolds number of less than 10 ² , it can be seen that the flow coefficient of the orifice decreases rapidly as the Reynolds number decreases.

As described above, the flow coefficient of the orifice is smaller than that of the Venturi, and the change in the Reynolds number is large. First, the overall pressure loss in the orifice is large. Second, the fluid in the orifice neck caused by the beta contractor (Vena Contracta) It can be seen that the phenomenon occurs because the flow area is reduced. In other words, the area in the neck is A _t, but in real flow, the area in the neck is smaller. Therefore, if the area at the point where the area is minimum is A _VC , the area ratio is A _VC / A _t <1. However, Venturi has an area ratio (A _VC / A _t ) approaching 1 because its cross-sectional area does not change rapidly, but the area ratio (A _VC / A _t ) is much smaller than 1 because the orifice changes rapidly. In particular, if the flow rate is slow in the orifice, the viscosity of the flowing fluid is large, and the ratio of the orifice neck to the inlet diameter is very small, this vena contractor effect is increased and the flow coefficient is further reduced (when the Reynolds number is very small).

However, as can be seen in the above example, the flow coefficient C _C of the metering orifice through which the form stock solution flows is a Reynolds number of about 10 ² orders, so the flow coefficient changes rapidly.

Meanwhile, the mixing ratio mixed in the form proportional mixer is shown in Equation 3.

In addition, the pressure P _W at the inlet of the low pressure generator and the foam feed liquid supply pressure P _C at the inlet of the mixing ratio of the foam stock solution are related to each other according to the form proportional mixer. In the pressure foam mixer format, these two values are the same.

P _C ≒ P _W

In addition, the pressure P _Wt at the venturi neck, the neck of the low pressure generator, is the same because the pressure P _Ce at the outlet of the metering orifice, which is a foam stock mixing ratio regulator, is directly connected.

P _Ce ≒ P _Wt

And the pressure P _Ce , P _Ct at the metering orifice neck and the outlet through which the foam stock solution has a similar pressure distribution according to the flow rate change as shown in Figure 5 can be written as follows.

P _C -P _ct ≒ k _c (P _C -P _ce )

Where proportional constant k _C for the pressure difference between the metering orifice inlet and outlet versus the pressure difference between the metering orifice inlet and the neck.

Therefore, the mixing ratio r in the form proportional mixer is as shown in equation (4).

When used at the design flow rate, the mixing ratio is normally mixed, but as the flow rate decreases, the number of Reynolds changes in the metering orifice, which is the mixing ratio control metering device in which the low pressure generator flows through the venturi of the low-pressure generator and the foaming solution flows. By the way, the flow coefficient C _W through Venturi is 0.95 ~ 0.98 with little change in Reynolds number, but the flow coefficient C _c of the metering orifice through which the foam stock passes is Reynolds number at 10 ² order. If it decreases, the value decreases rapidly. In other words, the existing proportional mixer has no change in area ratio A _C / A _W and the density ratio ρ _C / ρ _W is the same, so if the flow rate decreases at the normal flow rate through the foam proportional mixer as in the above experiment, The mixing ratio is reduced.

The following Table 1 shows the flow coefficient ratio (C _C / C _w ) decreasing from 0.74 to 0.42 when the flow rate is reduced to 1/4 in a 4 inch gun proportional mixer at 20 degrees Celsius. Will decrease.

4-inch Po proportional mixer (20 ° C) division Water (venturi) Alcohol-based aqueous film cloth (orifice) Water (venturi) Alcohol-based aqueous film cloth (orifice) Flow rate (lpm) 3595 107.9 (3%) 899 27.0 Density (kg / m ³ ) 998.2 1040.3 998.2 1040.3 Kinematic viscosity (m ² / sec) 1.0E-6 1.8 E-3 1.0 E-6 1.8 E-3 Inlet diameter (mm) 101.6 45.9 101.6 45.9 Diameter of neck (mm) 62.5 11 62.5 21.5 Velocity at Inlet (m / sec) 7.34 1.08 1.85 0.27 Velocity at the neck (m / sec) 19.5 18.9 4.88 4.73 Reynolds number at the entrance 7.48 E5 273.6 1.87 E5 6.83 Reynolds number at the neck 1.22 E6 114 3.05 E5 28.5 Flow coefficient 0.97 0.72 0.97 0.41 Flow coefficient ratio (C _c / C _w ) 0.74 0.42

In order to prevent the reduction of the mixing ratio as described above, the flow characteristics of the inlet and outlet of the foam proportional mixer should be kept constant, but the pressure and flow rate of the water supplied to the foam proportional mixer are changed, or it is necessary to branch at the rear of the foam proportional mixer. In other words, if each fire hydrant installed proportional mixer of the outlet diameter suitable for the size can be eliminated, but the installation cost is increased by increasing the proportional mixer and the number of valves to be installed. In addition, there is a problem in that several valves must be operated when the foam proportional mixer is operated due to a fire. On the other hand, there is a problem in that the entire existing pipe needs to be replaced. Therefore, if a fire occurs in two or three tanks, it will not be possible to effectively extinguish the fire.

On the other hand, when a new foam fire extinguishing system is installed, the proportional mixer is relatively expensive, and other valves and piping are less required, so most foam fire extinguishing designers and builders take the form of branching in one proportional mixer.

Therefore, the present invention changes the flow characteristics at the front and rear ends of the foam proportional mixer to change the flow rate passing through the foam proportional mixer, the pressure and flow rate of the water supplied to the foam proportional mixer, or branched from one proportional mixer to several This provides a foam proportional mixer that does not reduce the mixing ratio even when branching into small diameter pipes.

That is, the reason why the mixing ratio (r) is changed in Equation (4) is the flow coefficient ratio C _C / C _W of the venturi, which is a low pressure generating device, through which the metering orifice, which is a proportional mixing ratio control metering device, through which the form liquid passes, and the water passes. It can be seen that the mixing ratio of the foam stock solution is changed. At this time, k _C ρ _W / ρ _C has almost the same value under operating conditions at design time.

Therefore, the change of C _C / C _W which is the ratio of the flow coefficient to the flow fluctuation can be reduced.

Foam stock mixing ratio control The metering device and the low pressure generator have hydrodynamic similarity so that the flow coefficient ratio C _C / C _W maintains a constant value for the change in flow rate. As an example of such hydrodynamic similarity, if a venturi meter is used as the mixing ratio control metering device, a venturi is also used as the low pressure generator, and the two venturis have the same hydrodynamic similarity, the flow coefficient ratio C _C / Since C _W has a constant value, the foam stock solution mixing ratio is also constant with respect to the flow rate change. In addition, the nozzles may be used as the foam stock solution mixing metering device and the low pressure generator, respectively, in the same hydrodynamic similarity.

An embodiment of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

As described above, according to the present invention, the supply pressure or flow rate of the low-pressure generator, which is a case where the flow characteristics of the front and rear of the form proportional mixer is changed to change the flow rate through the form proportional mixer, or diverges from one foam proportional mixer to many Even when the fire hydrant is installed, the mixing ratio of the raw material of the foam does not change so that the fire can be effectively suppressed. Therefore, it is possible to solve the problem that the mixing ratio is reduced even at a low price by connecting branched one foam proportional mixer to several fire hydrants, and effectively extinguish a fire even in the extreme case where a fire occurs in all tanks connected to the foam proportional mixer. You can do it.

1 is a schematic structural diagram of a foam proportional mixer for fire suppression constant mixing ratio according to an embodiment of the present invention,

2 is a schematic configuration diagram of a general foam fire extinguishing system,

3 is a schematic diagram of the fire suppression in the tank using a general foam fire extinguishing system

4 is a structural diagram of a foam proportional mixer of a typical foam fire extinguishing system,

5 is a schematic diagram of a mixer for calculating the mixing ratio according to the flow rate in the foam proportional mixer of a typical foam fire extinguishing system,

6 is a graph showing the change in Reynolds number with respect to the flow coefficient in a typical metering orifice.

<Description of Symbols for Main Parts of Drawings>

10: metering venturi 20: water supply venturi

100: proportional mixer 110: water supply pipe

111: low pressure generator 112: water inlet

114: foam mixture outlet 116: metering orifice

118: foam stock solution inlet 120: foam stock solution

140: dispenser 150: flammable liquid tank

151: fuel 152: fire

153: Form 154: barrier

Claims (3)

delete In the foam proportional mixer of the foam fire extinguishing system including a low pressure generator for receiving water supplied from the outside and a mixing ratio control metering device for supplying the foam stock solution to the low pressure generator, The low pressure generator is a water supply venturi 20, the mixing ratio control metering device is a metering venturi connected to the neck portion of the water supply venturi 20 while having a hydrodynamic analogy with the water supply venturi 20 Foam proportional mixer for fire suppression, characterized in that the mixing ratio is (10). In the foam proportional mixer of the foam fire extinguishing system including a low pressure generator for receiving water supplied from the outside and a mixing ratio control metering device for supplying the foam stock solution to the low pressure generator, The low pressure generator is a water supply nozzle, and the mixing ratio control metering device is a fire mixing foam, characterized in that the mixing ratio is a metering nozzle connected to the water supply nozzle while having a hydrodynamic similarity with the water supply nozzle. Proportional mixer.