CN1754589A - A method of mixing a gas with a liquid to provide an extinguishing liquid for fire-fighting installations - Google Patents

Abstract

The invention aims to provide a novel method, which can generate fine liquid mist for a fire service installation with the aid of a small and cheap pump. In the method, with the aid of a gas source (4), a pressure intensity of 50-300 Pa is provided in an eduction tube (2) of a fire service installation, then, the pressure intensity is reduced; a high-pressure pump generates a liquid pressure intensity which is corresponding to the pressure intensity; and then the pump generates a liquid pressure intensity in the eduction tube, and the liquid pressure intensity is adjusted to the pressure intensity which is provided by the gas source and gradually decreases later.

Description

A method of mixing a gas with a liquid to provide an extinguishing liquid for fire-fighting installations

This application is a divisional application of Chinese Patent Application No. 95192516.4.

The present invention relates to a method for mixing a gas with a liquid to provide a fire extinguishing liquid for a fire fighting installation comprising an outlet line connected to a sprinkler head, the method comprising dispensing in a certain outlet line in said outlet line The gases are mixed under pressure and the extinguishing liquid is sent to the outlet line at approximately equal pressure.

For example, as proposed in International Patent Application No. WO 92/20453, certain types of gasoline flames, such as kerosene flames in aircraft jet engines subjected to engine tests in a hangar designed for engine tests It is also nearly impossible to extinguish a fire with a jet of liquid like smoke. A jet engine flame like this can only be extinguished when the entire hangar, which may typically have a volume of about 3000cm3, is "completely flooded", ie is actually completely filled with liquid smoke with very small particles.

Liquid aerosols can in principle be produced with a device as described in International Patent Application WO 93/10859. In this application, a number of wall apertures (Wall apertures) are opened on the outgoing ascension tube of a hydraulic accumulator, so that the propulsive gas of the accumulator drives out only liquid at first, while After the liquid level drops to the same height as the uppermost tube wall hole, when more and more tube wall holes are exposed to the liquid level as the liquid level drops, the propellant gas gradually begins to mix into the ejected liquid. In the final stage of emptying the accumulator, it is possible to obtain useful liquid mist with sufficiently small droplets, but the liquid in the hydraulic accumulator is too large to be wasted as drained as useless fraction.

It is an object of the present invention to provide a novel method capable of producing a finely divided mist for fire fighting installations by means of small and inexpensive pumps. The method is characterized in that a finely divided liquid mist is generated, the liquid mist comprises a mixture of gas and liquid, and the generation of the liquid mist comprises the steps of:

- In the outlet line, a pressure of 50-300 bar is generated by means of a gas source and the pressure is subsequently reduced; and

- using a high pressure pump that provides a liquid pressure in said outlet line corresponding to said pressure of the gas source, and the pump then provides a liquid pressure in the outlet line - the liquid pressure adjusted to the gas The pressure provided by the source, which is then gradually reduced, and the pump is used to provide the extinguishing liquid in the outlet line at a small flow rate.

The function of the gas is to cause the liquid droplets to be divided into very small pieces, thus producing a liquid mist that is dispersed into fine particles. As the pressure in the line leading to the nozzle increases, the particles in the liquid mist are divided into finer particles. In the method, the gas source is configured to mix gas into an outlet line of the pump at at least substantially the same high pressure as the pump.

Preferably, compressed gas cylinders are used as the gas source. The gas source is advantageously composed of a plurality of compressed gas cylinders connected in parallel. The gas may be nitrogen, argon, air, or the like. In principle any suitable gas can be used. Depending on the type of gas used, the contents of compressed gas cylinders may be partially in liquid form. The initial inflation pressure of the air source is 50-300 bar. The inflation pressure of the gas cylinder is the same as the working pressure of the pump, which can be around 50-200 bar, although lower or higher is possible.

A relatively small pump flow in this sense means that the flow at maximum operating pressure is less than the flow of the associated sprinkler or nozzle. The pump flow may be 10-80%, preferably 20-50%, of the total extinguishing fluid flow at maximum working pressure.

Therefore, people can choose small water pumps with low price and low power.

In the case of so-called pure oil fires, it is advantageous to mix the concentrated foam with the extinguishing liquid to produce a smothering foam which prevents re-ignition. The hitherto known devices for this purpose are generally very inefficient, since pyrotechnics destroy the foam, that is to say, prevent the condensed foam from forming foam.

The device according to the invention enables efficient foam formation because the simultaneous injection of a relatively large amount of pure gas, such as nitrogen, protects the pyrotechnics from direct contact with the injected concentrated foam.

In the event of a fire eg on the deck of a car on a car ferry, other substances other than oil such as wood, cardboard will also burn. In order to also be able to combat such fires, in a preferred embodiment of the invention, the gas source, preferably a plurality of gas cylinders, is configured to evacuate one or more liquid tanks in a first stage so as to at least suppress the fire, while the gas pressure at The liquid tank is evacuated at least approximately as high as the operating pressure of the pump.

The invention will now be described with reference to the accompanying drawings, which show two preferred embodiments of the device proposed by the invention.

Figure 1 shows an embodiment in which a finely divided liquid aerosol is generated immediately.

Figure 2 shows an embodiment in which a liquid spray is initiated followed by a finely divided liquid aerosol and foam.

The embodiment shown in FIG. 1 has a pump 1 with an outlet line 2 leading to a plurality of spray heads 3 . Pump 1 may be a high pressure pump with a typical working pressure of 50-200 bar. A plurality of compressed gas cylinders 4 connected in parallel are connected to the outlet line 2 of the pump 1 through a non-return valve 5 ensuring that no liquid will flow into the compressed gas cylinders 4 . A non-return valve 6 installed on the pump 1 outlet line 2 also ensures that the gas will be delivered correctly. Compressed gas cylinder 4 can be filled with nitrogen. The air pressure in the compressed gas cylinder is suitable for 100-300 bar.

A throttle valve 31 is connected on the line 30 between the compression bottle and the outlet line 2 of the pump. The purpose of the throttle valve 31 is to adjust the mixing ratio of liquid and gas in the fire extinguishing liquid flowing into the outlet pipeline 2 . The throttle valve 31 is not indispensable. It is also conceivable to adjust this mixing ratio by selecting various dimensions of line 30.

In FIG. 2, reference numeral 11 designates a pump set which may for example consist of two 11 kW pumps each having a flow rate of about 50 liters/minute and a pressure of about 120 bar. An outlet line 12 leads to fire zones A-E with corresponding sprinklers or sprinklers 13A-13E. Each pump is equipped with a plurality of compressed gas cylinders 14 and a plurality of liquid tanks 15 , for example totaling 400 liters. Compressed gas at an initial pressure of, for example, 200 bar, at a flow rate of, for example, 1000 liters/minute, first forcefully drives the liquid from the liquid tank 15 to the respective activated fire protection zone. Thereafter, the working situation is generally similar to that in Figure 1. After the liquid in these bottles has been evacuated, the pressure in the compressed gas bottle 14 drops to 120 bar, that is to say to the pressure of the pump 11 . Thereafter, the pressure of the pump 11 itself will be adjusted according to the pressure of the compressed gas cylinder 14, so that the pump flow is 20-100% of the total flow of the extinguishing liquid which gradually decreases. When there is no gas in the compressed gas cylinder 14 and thus the gas pressure has dropped to zero, the pump flow is 100% of the total flow of extinguishing liquid.

A container for concentrated foam is indicated at 16 and a foam mixing device is indicated at 17 . A fresh water tank, for example of 3000 liters, is indicated by 18 and a sea or lake connection is indicated by 19 .

During the first phase, when pumping liquid from the liquid tank 15, the role of the pump unit 11 is negligible. During said first phase the valve 20 must be open so that water cannot enter the froth mixing device 17, ensuring that the device 17 cannot function. Because it is necessary to avoid foam mixing into the fire extinguishing liquid in the initial stage of fire extinguishing. This is because the foam has the undesirable effect of making the droplets ejected from the nozzle larger, thereby hindering the formation of a finely divided liquid mist. In the initial stages of fire fighting, finely divided liquid aerosols are especially needed. Foam will therefore not work well in the initial stages of extinguishing a fire.

After the liquid tank 15 has been evacuated, the typical values given above can be used to ensure effective generation of a finely divided liquid aerosol for about half an hour by using the fresh water tank 18, after which sea or lake water can be used if necessary.

After the fire has been brought under control with water mist, the valve 20 can be closed to allow foam to be added to the extinguishing liquid, thereby creating a thick "foam matting" which prevents the fire from re-igniting. It is worth noting that the apparatus of Figure 2 does not necessarily have to have a foam mixing device. In practice, the valve 20 is closed in such a way that the pressure switch 140 connected to the line 130 generates a pressure signal after the pressure has decreased to a predetermined value (eg 30 bar). Thus, this pressure signal controls the valve 20 .

Of course, the gas cylinder 14 can also be connected to the outlet pipeline 12 without passing through the liquid tank 15 .

The invention has been described above by way of example, so it should be noted that the invention can be modified in many details within the scope of the appended claims. For example, modifications may be made in implementing a compressed gas source. The gas source does not necessarily have to be composed of compressed gas bottles.

Claims (2)

1. A method for mixing a gas with a liquid to provide a fire extinguishing liquid to a fire extinguishing device comprising a lead-off line (2; 12) to a sprinkler head (3; 13A, 13E), said method comprising mixing gas at a pressure in the outlet line and delivering fire extinguishing liquid in the outlet line at approximately equal pressure, characterized in that a fine mist of liquid comprising a mixture of gas and liquid is generated by : providing a high pressure of 50-300 bar in the outlet line (2; 12) by means of a gas source (4; 14), and subsequently reducing the pressure; and By means of a high pressure pump (1; 11) which provides a liquid pressure in the outlet line (2; 12) corresponding to said high pressure of the gas source, which then provides a The liquid pressure, which is adjusted to the pressure supplied by the gas source (4; 14), is then gradually reduced, and the extinguishing liquid is supplied in the lead-off line at a small flow rate by means of the pump. 2. A method according to claim 1, characterized in that compressed gas cylinders are used as gas source (4; 14).