JP2014020047A - Structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure capable of restricting a pressure peak generated after breakage of a structurally weak portion by a simple configuration.SOLUTION: A structure 10 includes a structurally weak portion 3. When a combustible gas is mixed into an internal space S of the structure 10 and the combustible gas is burnt, the structurally weak portion 3 is opened, the internal space S and an outer space communicate with each other via the structurally weak portion 3, and a secondary pressure peak is generated in the internal space S after opening of the structurally weak portion 3. An interior material 2 to form the internal space S of the structure 10 is higher in acoustic absorption coefficient than a steel material and the density thereof is higher than 10 kg/m.

Description

  The present invention relates to a structure, for example, a structure in which a pressure peak occurs after opening of a weak structure when combustible gas is burned.

  Conventionally, various safety measures have been taken for structures such as ordinary houses and factory buildings in order to reduce the damage caused by an explosion caused by flammable gas. For example, in general houses and factory buildings, etc., weak parts (structural weak parts) such as windows, doors, and pressure release valves are provided. If the pressure inside the structure rises by igniting flammable gas, the above weak parts As a result of breakage or the like, a rapid pressure increase inside the structure can be suppressed.

  By the way, the magnitude of the damage caused by the above-mentioned gas explosion is closely related to the pressure increase rate, the maximum pressure reached, and the number of pressure peaks. It is necessary to grasp the behavior accurately. For this reason, in this field, the use of constant volume containers of various shapes and sizes having fragile parts simulating structures such as buildings, and burning combustible gas in the containers, the gas in the structure Experiments and research to understand the phenomenon of explosions are being conducted.

FIG. 5 shows a cubic container made of a steel material having an inner volume of 2.55 m ³ and an opening coefficient of fragile part of 9.2, and uniformly mixing a mixture of natural gas and air in the container. It shows the pressure history in the cubic container when it is filled and the air-fuel mixture is combusted with an ignition source arranged at the center of the cubic container (Non-patent Document 1).

  As shown in the figure, the pressure behavior due to gas combustion generated in the constant volume container having the fragile portion is the pressure increase in the sealed state before the fragile portion is broken and the half open state after the fragile portion is broken. It can be classified as a secondary pressure rise.

  In the pressure rise in the sealed state, when there are almost no obstacles that hinder flame propagation in the container, the pressure rise can be estimated with relatively high accuracy by considering the acceleration effect of flame propagation. Also, for the pressure peak that occurs immediately after the fragile part is destroyed, an effective estimation formula for the maximum pressure reached (P1 in the figure) is known, and it is possible to estimate the pressure peak with relatively high accuracy. it can.

  On the other hand, in the pressure increase after the destruction of the fragile part, the pressure increase that occurs when the outflow of the gas to the outside of the container competes with the pressure increase (volume expansion) due to combustion, and the latter wins, or the gas Helmholtz It is known that pressure peaks occur due to various factors such as periodic pressure increase / decrease due to vibration and pressure increase (acoustic effect) due to the pressure wave generated in the combustion process of the gas mixture combined with the acoustic mode of the container. ing. These pressure peaks change greatly depending on slight changes in conditions, and it is considered that the occurrence or non-occurrence of the pressure peaks is also affected. Therefore, it is extremely difficult to accurately predict these pressure peaks.

  Although it is extremely difficult to predict the pressure increase after the destruction of the fragile part as described above, for example, when the container shape has a three-dimensional symmetry such as a cube, or the ignition source is in the center of the container. It has been pointed out that it occurs only under limited circumstances such as when it is placed, and is extremely unlikely to occur in an actual gas explosion accident. Safety measures have been studied to suppress the pressure peak that occurs immediately after the destruction.

  However, as shown in Fig. 5, the pressure peak (P2) that occurs after the destruction of the fragile part may be several times the pressure peak (P1) that occurs immediately after the fragile part is destroyed. Considering that the peak pressure at the time defines the magnitude of the damage, once the gas explosion occurs even under the above limited conditions, the magnitude of the damage is enormous. turn into. Therefore, in this field, it is considered extremely important to design a structure that takes into account the pressure peak that occurs after the destruction of the fragile portion.

  For such a problem, Non-Patent Document 1 considers that the pressure peak generated after the destruction of the fragile portion is the pressure peak generated by the acoustic effect, and affixes glass wool, which is a material that absorbs acoustic waves, to the inner wall of the container Thus, a method for suppressing a pressure peak generated after the destruction of the fragile portion is disclosed.

Cooper M.G., et. Al., “On the Mechanisms of Pressure Generation in Vented Explosions,” Combustion and Flame, Vol.65, 1986

  As shown in FIG. 6, according to the method disclosed in Non-Patent Document 1, natural gas and air are mixed in the container by adhering glass wool to the inner wall of the cubic container and absorbing acoustic waves. Even when the air-fuel mixture is uniformly filled and the air-fuel mixture is burned with an ignition source arranged at the center of the cubic container, the pressure increase and pressure peak after the destruction of the fragile portion shown in FIG. Can be suppressed.

  However, in the method disclosed in Non-Patent Document 1, cotton-like glass wool having an extremely high sound absorption coefficient is attached to the inner wall of the container, and in a structure such as an actual general house or factory building, glass wool is used as such. It is difficult to think of the situation where it is applied directly to the inner wall. In actual structures such as buildings, flat or curved interior materials (such as gypsum board, flame-retardant plywood, and lauan materials) that are harder than glass wool and have a low sound absorption coefficient are usually pasted. The present situation is that no mention is made as to whether or not the pressure increase after the destruction of the fragile portion is suppressed when such an interior material is used.

  This invention is made | formed in view of said situation, and makes it a subject to provide the structure which can suppress the pressure peak generate | occur | produced after destruction of a weak part with a simple structure.

  In order to solve the above-mentioned problems, the present inventors have conducted a lot of experiments and research to obtain a structural body having a structural weak part (fragile part). Even when an interior material having a sound absorption coefficient of a level applicable to a structure such as a general house or a factory building is used as an interior material for a structure where a pressure peak occurs, the interior after the destruction of the weak structure It has been found that the pressure peak generated in the internal space can be suppressed. The present invention is based on the above findings obtained by the present inventors.

That is, the present invention is a structure having a structural weak part, and when the combustible gas is mixed in the internal space and combusted, at least a part of the structural weak part is opened. In the structure in which the internal space and the external space outside the internal space communicate with each other through at least a part of the structural weak part, and a pressure peak is generated in the internal space after the opening of the structural weak part. The interior material forming the internal space of the structure is characterized in that the sound absorption coefficient is higher than that of steel and the density is higher than 10 kg / m ³ .

  Here, the sound absorption coefficient is the efficiency of absorbing sound energy with respect to a certain frequency sound.

  In addition, a structure in which a pressure peak occurs in the internal space after the opening of the weak structure has an internal space having a three-dimensional symmetry such as a spherical shape or a regular polyhedron shape. It is a structure in which an ignition source is arranged at the center.

  Further, the interior material can be formed of a material including at least one selected from the group consisting of wood, stone, fiber, and synthetic resin, for example, a lauan material as the wood. The stone material can include a gypsum board, and the fiber material can include polypropylene. The surface of the interior material can be covered with a synthetic resin material made of vinyl chloride.

In the experiments by the present inventors, a weak structural portion having a lower strength than other portions is formed in a part of the structure, and the combustible gas is mixed in the internal space to burn the combustible gas. When the structural weak part is opened, the internal space and the external space communicate with each other via the structural weak part, thereby suppressing the pressure peak in the sealed state before the structural weak part is destroyed. In addition, the interior material that forms the interior space has a higher sound absorption coefficient than steel and a density higher than 10 kg / m ³ , while increasing the density of the interior material and maintaining the hardness, Since the acoustic wave generated in the space can be effectively absorbed, the pressure peak generated after the destruction of the weak structural portion can be effectively suppressed.

  According to the present invention, for example, an interior material having a sound absorption coefficient of a level applicable to a general structure can be used, and a pressure peak generated after destruction of a weak structure can be suppressed with a simple configuration. For this reason, it is possible to effectively reduce the damage of the explosion accident caused by the combustible gas such as city gas while maintaining the hardness of the interior material.

The front view which shows one Embodiment of the structure by this invention. The figure which shows the constant volume container used in experiment. The figure which shows the result of the pressure measurement in the constant volume container of an Example and a comparative example. The figure which shows the result of having image | photographed the combustion state in each time in the constant volume container of an Example and a comparative example. The figure which shows the pressure history in a container when combustible gas is burned with the cubic container comprised with steel materials. The figure which shows the pressure log | history in a container when glass wool is affixed on the inner wall of the cube container comprised with steel materials, and combustible gas is burned.

  The present invention will be described below with reference to the drawings.

  FIG. 1 is a front view showing an embodiment of a structure according to the present invention. In the illustrated example, the case where the internal space of the structure has a substantially cubic shape will be described. However, the internal space only needs to have a three-dimensionally symmetric shape, for example, a spherical shape or a regular octave. It may be a regular polyhedron shape such as a polyhedron shape.

  The illustrated structure 10 has an internal space S having a cubic shape, and an electric lamp 1 that can serve as an ignition source is disposed at the center of the internal space S. The central portion of the internal space S in which the electric lamp 1 is disposed is a position where a pressure peak due to an acoustic effect may occur during a gas explosion described later, and is strictly at the center of the internal space S. It is not limited to being.

  The interior material 2 forming the internal space S is composed of six interior component materials 2a of the front and rear surfaces, the left and right surfaces, and the upper and lower surfaces (in the figure, the interior component materials on the front surface are omitted so that the inside can be seen. The window 3 (also referred to as a structural weak part or a weak part) having a lower strength than the other part is provided at the substantially central part of one of the interior components 2a (right side in the figure). Is formed. Note that the position of the window 3 that can be a weak structural portion can be set to the position of the central portion of the interior material 2.

  The interior material 2 has a sound absorption coefficient higher than that of a steel material mainly composed of iron, and its density is higher than that of general glass wool, which is a cotton-like material made of glass fibers. Here, since the interior material 2 has a higher density than glass wool, it is generally considered that the interior material 2 has higher hardness than glass wool.

Here, glass wool, when used as a sound absorbing material of the general house is the density of 10~32kg / m ³ approximately, if generally density of 10 kg / m ³ is the density is 32 kg / m ³ The sound absorption rate is relatively higher than in the case, and in the illustrated example, the density of the interior material 2 is higher than 10 kg / m ³ .

  Examples of the forming material of the interior material 2 include wood made of lauan material and flame retardant plywood, gypsum board and concrete, stone material made of granite, andesite, marble, etc., fiber material made of polypropylene and nylon, and chloride. Examples include synthetic resin materials made of vinyl, synthetic rubber, and the like.

  When the internal space S of the structure 10 is filled with a combustible gas (for example, city gas), a spark is generated from the electric light 1 for some reason, and the combustible gas in the internal space S is ignited and burned (gas As long as the internal space S is sealed, the pressure in the internal space S increases with the combustion of the combustible gas, and the window 3 is damaged when the predetermined pressure is reached. The internal space S and the external space outside the interior material 2 communicate with each other through the window 3, and the pressure increase in the internal space S is suppressed.

  Further, as described above, when the internal space S has a three-dimensionally symmetric shape, or when the lamp 1 that can serve as an ignition source is disposed at the center of the internal space S, the window Although the pressure peak due to the acoustic effect may occur again after the 3 is damaged, the interior material 2 is made of a material having a higher sound absorption rate than the steel material, and is generated when the combustible gas is burned. Since the acoustic wave is absorbed by the interior material 2, the pressure peak generated after the window 3 is damaged due to the acoustic effect or the like is suppressed. The acoustic effect is an effect in which an acoustic wave that repeats reflection while propagating through the internal space S interacts (resonates) with a pressure wave flame generated by combustion.

  Here, since the interior material 2 is made of a material having a hardness higher than that of glass wool as described above, the structure 10 can be used as a general house or a factory building.

[Experiment and result on pressure peak in city gas combustion by test vessel]
The present inventors made two types of test containers (examples and comparative examples) with different types of interior materials, and measured the pressure inside the container when city gas was burned in the container for each container. The combustion state was observed.

The method for measuring the pressure inside the container is to form a pressure sensor mounting port at the center of a predetermined side of the cubic shaped container, and place the pressure sensor M102B06 (PCB) on the mounting port. The pressure of was measured. Here, the measurement data of the pressure sensor M102B06 were collected at a sampling rate of 10 ⁴ times / sec using a data logger GR-7500 (Keyence Corporation).

  As a method for observing the combustion state inside the container, a high-speed camera FASTCAM SA3 (manufactured by Photron) was placed outside the container, and the inside of the container was photographed through a transparent acrylic plate provided on the side of the container. Here, the shooting speed of the high-speed camera FASTCAM SA3 was 2000 FPS.

[Example]
As shown in Fig. 2, a fixed volume container made of rolled steel (SS400) with an internal size of 600 x 600 x 600 mm and an internal volume of 216 L is used, and a fiber material (carpet) made of polypropylene on the bottom of the inner wall surface. A lauan material was affixed to the side and upper surface of the material, and a vinyl chloride wallpaper was affixed to the inner surface of the lauan material. In addition, the surface of the front side among the container side surfaces was a transparent acrylic plate in order to observe the combustion state from the outside. In addition, an opening with a diameter of 200 mm is provided at the center of one of the side surfaces of the container to which the lauan material is attached (opening coefficient K = A / V ^2/3 = 11.5, A is the opening area, V is the container volume) And an aluminum foil was applied to cover the opening to form a weak structure (fragile part).

  A flammable mixture (methane 9.3 vol%) consisting of methane and air was filled in a constant volume container, and the mixture was ignited by a spark plug disposed in the center of the constant volume container to burn the mixture. .

[Comparative example]
A constant volume container made of rolled steel (SS400) with an inner dimension of 600 × 600 × 600 mm and an inner volume of 216 L was used, and no interior material was attached to the inner wall surface. In addition, the surface of the front side among the container side surfaces was a transparent acrylic plate in order to observe the combustion state from the outside. In addition, an opening having a diameter of 200 mm was formed at the center of one of the side surfaces of the container, and an aluminum foil was attached to cover the opening to form a weak structure (fragile part).

  A flammable mixture (methane 9.3 vol%) consisting of methane and air was filled in a constant volume container, and the mixture was ignited by a spark plug disposed in the center of the constant volume container to burn the mixture. .

[Results of pressure measurement and combustion state observation during city gas combustion in a test vessel]
FIG. 3 is a diagram showing the results of pressure measurement in the constant volume containers of the example and the comparative example, and FIG. 4 shows the results of photographing the combustion state at each time in the constant volume containers of the example and the comparative example. FIG.

  As shown in FIG. 3, in the test container of the comparative example, when the air-fuel mixture burns in the container, the pressure in the container starts to increase in about 20 msec, and the pressure in the container reaches about 15 kPa in about 70 msec ( Primary pressure peak). Here, the aluminum foil affixed to the opening on the side of the container was damaged, and the pressure in the container decreased rapidly, and the pressure in the container became 5 kPa or less at about 80 msec. Thereafter, the pressure in the container started to increase again from about 150 msec, the pressure in the container reached about 170 kPa at about 170 msec (secondary pressure peak), and the pressure in the container rapidly decreased after about 170 msec.

  That is, in the test container of the comparative example (the opening coefficient of the weak structure portion is 11.5), a strong pressure peak (secondary pressure peak) including a vibration component was confirmed between about 150 msec and 220 msec, and this secondary pressure peak However, it was inferred that this was a pressure peak due to the acoustic effect of the cubic container described with reference to FIG. 5 (the opening coefficient of the weak structure portion was 9.2).

  Moreover, in the test container of the comparative example, as shown in FIG. 4, it was confirmed that the flame grew rapidly in the vicinity of about 170 msec.

  On the other hand, in the test container of the example, as shown in FIG. 3, when the air-fuel mixture burns in the container, the pressure in the container starts to increase in about 20 msec, and the pressure in the container reaches about 15 kPa in about 70 msec. It reached (primary pressure peak), and the aluminum foil attached to the opening on the side of the container was damaged, and the pressure in the container decreased rapidly, but no pressure peak was measured after about 80 msec. That is, in the test container of the example (the opening coefficient of the weak structure portion is 11.5), the pressure peak (secondary pressure peak) generated after the failure of the weak structure portion confirmed at about 170 msec in the comparative example was confirmed. There wasn't.

  Further, in the test container of the example, as shown in FIG. 4, it was confirmed that the flame ball continued to grow gradually after about 140 msec, and the interior material was ignited from the place where the flame reached the inner wall surface. The rapid growth of the flame around 170 msec confirmed in the example was not confirmed.

  In addition, the present inventors have confirmed that the above results in the test containers of Examples and Comparative Examples are reproducible.

  From the results of this experiment, a simple structure of placing a Lauan or Polypropylene carpet, which has a higher sound absorption rate than steel and lower than glass wool, on the inner wall of a cubic container made of steel makes it possible to prevent structural weak parts during gas explosions. It has been demonstrated that pressure peaks that can occur after failure can be reliably suppressed.

1 ... Electric light (ignition source)
2 ... Interior material 2a ... Interior component 3 ... Window (structure weak part)
10 ... Structure S ... Internal space

Claims (6)

A structure having a weak structure portion, and when the combustible gas is mixed in the internal space and the combustible gas is burned, at least a part of the weak structure portion is opened to form the internal space and the internal space. In the structure in which an external space outside the space communicates through at least a part of the structural weak part, and a pressure peak occurs in the internal space after the opening of the structural weak part,
The interior material forming the internal space of the structure has a sound absorption coefficient higher than that of a steel material and a density higher than 10 kg / m ³ .   2. The structure according to claim 1, wherein the internal space has a cubic shape, and the structural weak portion is formed in any one of six interior components constituting the interior material. body.   The structure according to claim 1 or 2, wherein an opening coefficient of the structural weak part is 9.2 or more and 11.5 or less.   The said interior material is formed with the raw material containing at least any one selected from the group which consists of a timber, a stone material, a fiber material, and a synthetic resin material, The any one of Claim 1 to 3 characterized by the above-mentioned. Structure.   The structure according to claim 4, wherein the wood is made of Lauan, the stone is made of gypsum board, and the fiber is made of polypropylene.   The structure according to claim 4, wherein a surface of the interior material is covered with a synthetic resin material made of vinyl chloride.

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