JP4781179B2 - Evacuation Safety Verification Method Using Approximate Equation of Smoke Outflow - Google Patents

Description

  The present invention relates to an evacuation safety verification method using an approximate expression of smoke outflow.

In recent years, the Evacuation Safety Verification Act has been enacted in order to secure an evacuation route in the event of a fire in a building. The law mainly stipulates the following calculation methods.
(a) Room evacuation calculation to confirm that the fire room can be evacuated outside
(b) Floor evacuation calculation to confirm that it is possible to evacuate from the verification floor including the fire room
In (a), for each room on the verification floor, the time to finish evacuation from the room (= evacuation start time + walking time + exit passage time) and the predetermined height (1.8m from the floor) The smoke descent time until it gets down to each is calculated, and if the former is shorter than the latter, the safety of evacuation is verified.

  In (b), for each assumed fire room, the floor evacuation end time until everyone on the verification floor evacuates to the evacuation stairs and the smoke descent time until smoke falls to a predetermined height in the evacuation route are shown. Each is calculated, and if the former is shorter than the latter, the safety of evacuation from the floor is verified.

Here, the smoke fall time in the room is expressed by the following formula 4, and the smoke fall time in the floor is a numerical value calculated by the following formula 5 for all rooms passing when evacuating from any fire room. It is the maximum value of the total. However, A _room is the floor area of the _room , H _room is the average ceiling height, Vs is the amount of smoke generated, Ve is the effective amount of smoke discharged, and H _lim is the limit smoke layer height.
[Formula 4] ts = A _room × (H _room −1.8) / max (Vs−Ve, 0.01)
[Formula 5] ts = A _room × (H _room −H _lim ) / max (Vs−Ve, 0.01)
In the calculation of Equation 4 and Equation 5, Vs in the fire room may be calculated by actually calculating the amount of smoke generated in the room, but Vs in each room connected to the fire room in the floor evacuation calculation is It is necessary to calculate the amount of smoke flowing from the original side to each room. The notification of the former Ministry of Construction regarding this smoke spillage is as follows (Non-Patent Document 1). This method is a kind of approximation. In short, the smoke outflow amount and the opening area are proportional.

これに対して、火元側への煙の逆流を視野に入れた煙流出量の計算方法も提案されている（非特許文献２）。まず、室内で火災が発生すると、膨張された煙が天井側に溜まる。室の上部に溜まった煙層の気体密度をρ_ｓ、煙層以外の空気部分の密度をρ_ａとすると、煙層内には高さｚ方向に、浮力によってδ（ΔＰ）／δｚ＝ｇ（ρ_ｓ−ρ_ａ）という圧力勾配を生ずる。この圧力勾配により火災室の上部から隣室の上部へ煙が流出すると、質量保存の法則により隣室の下部から火災室の下部へ空気が流れ込む。この場合、煙層の高さ方向のどこかに隣室との間で圧力差が零となる場所（中性帯）があるはずである。この中性帯を境として、中性帯上方から煙が隣室へ流出し、中性帯下方から、隣室内の空気が流入する空気モデルを想定する。この中性帯の高さをＨ_ｏとし、更に開口上端高さをＨ_ｔｏｐ、煙下端高さＨ_ｓを、中性帯の高さをＨ_ｏとすると、火災室からの煙の流出量ｍ_ｏｕｔ及び隣室からの空気の流入量ｍ_ｉｎに関して次の２式を得る。ここでｍ_ｏｕｔ及びｍ_ｉｎはともに質量である。またαは開口係数，Ｂは開口幅である。
［数式２］
ｄｍ_ｏｕｔ／ｄｔ＝（２／３）αＢ×（Ｈ_ｔｏｐ−Ｈ_ｏ）^３／２√（２ｇρ_ｓ｜ρ_ｓ−ρ_ａ｜）
［数式３］
ｄｍ_ｉｎ／ｄｔ＝（２／３）αＢ×（Ｈ_ｏ−Ｈ_ｓ）^３／２√（２ｇρ_ａ｜ρ_ｓ−ρ_ａ｜）＋αＢＨ_ｓ×（Ｈ_ｏ−Ｈ_ｓ）^１／２√（２ｇρ_ａ｜ρ_ｓ−ρ_ａ｜）
この２式を解くときには、Ｈ_ｏの適当な初期値を代入して、ｍ_ｏｕｔ及びｍ_ｉｎの一次解を計算し、これら解より中性帯上方からの煙の流出量ｍ_ｏｕｔと中性帯下方からのエアの流入量ｍ_ｉｎとをそれぞれ求め、前者が大であるときには中性帯の高さを所定幅ΔＨだけ上げ、後者が大であるときには、中性帯の高さをΔＨだけを下げる。そして新たな中性帯の高さに基づいて、ｍ_ｏｕｔ＝ｍ_ｉｎとなるまで逐次計算を繰り返す。
平成１２年建設省告示第１４４１号 田中▼たけ▲義著「建築火災安全工学入門」 平成５年７月２０日財団法人日本建築センター

On the other hand, the calculation method of the smoke outflow amount which considered the reverse flow of the smoke to the fire source side is also proposed (nonpatent literature 2). First, when a fire occurs in a room, the expanded smoke accumulates on the ceiling side. Assuming that the gas density of the smoke layer accumulated in the upper part of the chamber is ρ _s and the density of the air portion other than the smoke layer is ρ _a , δ (ΔP) / δz = g by buoyancy in the height z direction in the smoke layer. A pressure gradient of (ρ _s −ρ _a ) is generated. When smoke flows out from the upper part of the fire room to the upper part of the adjacent room due to this pressure gradient, air flows from the lower part of the adjacent room to the lower part of the fire room according to the law of mass conservation. In this case, there should be a place (neutral zone) where the pressure difference between the adjacent chambers becomes zero somewhere in the height direction of the smoke layer. An air model is assumed in which smoke flows out from above the neutral zone into the adjacent room, and air in the adjacent room flows from below the neutral zone. If the height of this neutral zone is H _o , the top height of the opening is H _top , the smoke lower end height H _s , and the height of the neutral zone is H _o , the amount of smoke flowing out of the fire chamber m we obtain the following two equations with respect to inflow _{m in} of air from _out and the next room. Here _{m out} and _{m in} are both mass. Α is an aperture coefficient, and B is an aperture width.
[Formula 2]
dm _out / dt = (2/3) αB × (H _top −H _o ) ^3/2 √ (2gρ _s | ρ _s −ρ _a |)
[Formula 3]
dm _in / dt = (2/3) αB × (H _o −H _s ) ^3/2 √ (2gρ _a | ρ _s −ρ _a |) + αBH _s × (H _o −H _s ) ^1/2 √ (2 gρ _a | _{ρ s -ρ a} |)
The when solving the two equations, by substituting an appropriate initial value of H _o, to calculate the primary solution of m _out and m _in, runoff m _out and the neutral zone of the smoke from the neutral zone above the these solutions seeking the air inflow m _in from below, respectively, raising by a predetermined width ΔH height neutral zone when the former is larger, when the latter is large, only ΔH height neutral bands Lower. Then, based on the height of the new neutral _zone, repeat the sequential calculation until _m out ₌ m _in.
2000 Ministry of Construction Notification No. 1441 Tanaka ▼ Takeyoshi ”Introduction to Architectural Fire Safety Engineering” July 20, 1993 Japan Architecture Center

  The calculation formula Vs = 2Aop of Non-Patent Document 1 is a rough approximation as an approximation method, and the amount of outflow is estimated more than necessary.

  The calculation formula of Non-Patent Document 2 is a successive approximation method, and it is necessary to perform many calculations in order to determine the smoke outflow amount.

  The speed of each of these calculations can be increased by using a computer. However, since many calculations are repeated, there may be inconveniences such as the numerical value not converging properly depending on the initial value of the neutral zone and the increment ΔH. . In designing a building, it may be necessary to easily obtain an approximate solution by a portable computer or the like separately from obtaining an exact calculation solution. In such a case, the method of Non-Patent Document 2 is complicated. Pass.

  In the present invention, a more accurate approximate solution than the calculation formula of the Ministry of Construction notification shown in Non-Patent Document 1 can be easily obtained by a single calculation, and the calculation formula of the amount of smoke spillage that can ensure safety. Provide evacuation safety verification method using

The first means is
Using the fire room on any floor in the building or the smoke propagation room connected to it as the object of calculation, calculate the amount of smoke that flows out from this room to the next area through the opening within the unit time,
Based on this amount of smoke spill, calculate the smoke fall time until smoke falls from the ceiling to the height that becomes an obstacle to safe evacuation in the adjacent area,
In the evacuation safety verification method for judging whether or not safe evacuation is possible by comparing this smoke fall time with the evacuation time required to evacuate to the outside of the adjacent area or to the evacuation exit
The inside of the calculation room R is divided into an upper smoke layer and a lower clean air layer, and there is no difference in air density between the clean air layer and the air in the adjacent area N Assuming
The content is to approximate the mass dm _out / dt of smoke flowing out from the calculation room R to the adjacent area N per unit time by the following equation.
[Formula 1]
dm _out / dt = (2/3) αB × (H _top −H _s ) ^3/2 √ (2gρ _s | ρ _s −ρ _a |)
α: Opening coefficient, B: Opening width, H _top : Opening top height, H _s : Smoke bottom height, ρ _s : Smoke density, ρ _a : Air density This means is the formula Vs = compared to 2Aop we propose an approximate expression of the smoke outflow reflecting the height H _s of the smoke layer bottom. In deriving this formula, it is assumed in FIG. 1 that the density of the air layer below the smoke layer of the fire chamber and the air layer of the corresponding height in the adjacent area are the same. Then, the pressure difference between the two air layers becomes zero, so that the air enters and exits zero. In the smoke layer, there is a pressure gradient of δ (ΔP) / δz = g (ρ _s −ρ _a ), so that the pressure directly increases from the lower end of the smoke layer toward the upper end of the opening. . Therefore, the above formula 1 is obtained by replacing H _o in the above formula 2 with H _s .

If only the form of Equation 1 is viewed, only one variable is replaced as compared to Equation 2, but this replacement is not natural from a physical point of view. This is because, as can be seen from FIG. 1, smoke is unilaterally emitted from the fire room to the adjacent area, there is no return airflow, and the law of conservation of mass is not established. However, if the left side of Equation 1 is dm _out / dt (H _s ) and the left side of Equation 2 is dm _out / dt (H _o ), then H _s <H _o , so dm _out / dt (H _o ) < It can be said that dm _out / dt (H _s ) is guaranteed. In the calculation of problems directly related to human life like the evacuation safety verification method, even if the approximation method is highly accurate as a whole, it is useless if there is a possibility that the approximate solution may shift to a more dangerous area side than the exact solution. Therefore, in this means, even if the air model deviates to some extent from the actual decrease, a minimum guide amount that does not exceed the actual smoke outflow amount is proposed.

  FIG. 3 shows a thin line that represents the exact solution according to the mathematical expression of Non-Patent Document 2 regarding the amount of smoke outflow with respect to the magnitude of Vs with respect to the change in specific gravity of a certain smoke layer by changing the height Hs at the lower end of each smoke layer. The simple approximate solution according to the notification from the Ministry of Construction in Table 1 is indicated by a dotted line, and the approximate solution according to the present invention is indicated in bold. Although the approximate solution of the present invention is larger than the exact solution in all specific gravity ranges, it can be seen that the accuracy is significantly improved as compared with the simple approximate solution notified by the Ministry of Construction.

  In this means, the “calculated room” refers to a room for which the smoke outflow amount is calculated, and includes an evacuation passage (for example, a corridor) leading to the evacuation exit. In particular, it includes fire rooms and smoke propagation rooms in the Evacuation Safety Verification Act. In other words, in the case of the above-mentioned floor evacuation safety verification, in addition to the amount of smoke spilled from the fire room to the next room, it is necessary to sequentially calculate the amount of smoke spilled from the next room (smoke propagation room) to the next room. The approximate expression (Formula 1) of the present invention can be applied to each of the series of chambers. However, it is not necessary to apply the calculation method of the present invention to the entire series of rooms (or areas). For example, a more precise calculation method may be applied to a room close to the fire source, and a coarser approximation method may be applied to a room far from the fire source. Specifically, the exact calculation method of Non-Patent Document 2 may be applied to a room close to the fire source, and the approximation method of Formula 1 of the present invention may be applied to a room far from the fire source, or close to the fire source. The approximation method of Formula 1 may be applied to the room, and the simple approximation formula of the Ministry of Construction notice may be applied to the room far from the fire source. This will be described later.

  In the present specification, “outflow mass” refers to the mass of smoke flowing out per unit time with respect to Equation 1 of the present invention or the simultaneous calculation formula of Non-Patent Document 2. In addition, when referring to the “outflow amount” of smoke, the concept includes the volume of smoke flowing out per unit time (outflow capacity) in addition to the outflow mass.

The second means includes the first means, and when there are a plurality of openings in the calculation room, among these openings,
For a plurality of openings that are contiguous to the same adjacent area, calculate as one opening having an opening area equivalent to the series of openings,
In calculating the amount of smoke outflow from each independent opening for independent openings that are continuous in different adjacent areas, it is assumed that there are no other independent openings and that the calculation is performed.

  This means proposes a calculation method when there are a plurality of openings in the calculation target room. When a plurality of openings are contiguous with one adjacent area, it is not necessary to distinguish from the case of having a single opening equivalent to these openings. On the other hand, when multiple openings are connected to different adjacent areas, it is difficult to uniquely determine which adjacent area the smoke flows into, so when calculating the amount of outflow from one opening, Handle as if there was no opening. This treatment has the same idea as the first means in that it considers that the amount of smoke outflow is in excess of reality in order to establish safety. When branching into several evacuation routes from the fire room to the evacuation exit, the amount of smoke spillage is expected to be quite large. In this case, when the approximate expression of the present invention is used, the error is reduced to half or less, so that the accuracy of calculation is greatly improved as a whole.

“A plurality of openings that are continuous in the same adjacent area” means that the room A → the opening d ₁ → the area C, the room A → d ₂ → the area C, and the like when they are directly connected to the same area from one room It shall be an opening. It does not include the case where it is indirectly connected to the same area, such as room A → room B → area C.

The third means has the first means or the second means, and calculates the amount of smoke flow from the fire chamber to the smoke propagation chamber, and then the smoke flow from the smoke propagation chamber to the adjacent area. When calculating the quantity, the mass of smoke flowing out from the fire chamber is calculated by the above-mentioned equation 1, and the amount of smoke flowing out from the smoke propagation chamber is calculated by the following equations 2 and 3.
[Formula 2]
dm _out / dt = (2/3) αB × (H _top −H _o ) ^3/2 √ (2gρ _s | ρ _s −ρ _a |)
[Formula 3]
dm _in / dt = (2/3) αB × (H _o −H _s ) ^3/2 √ (2gρ _a | ρ _s −ρ _a |) + αBH _s × (H _o −H _s ) ^1/2 √ (2 gρ _a | _{ρ s -ρ a} |)
However the H _top open top height, H _s smoke lower height, H _o smoke propagation chamber and neutral zone difference in pressure of the air is zero the adjacent area height, m _out from the fire chamber runoff smoke, m _in the inflow of air from the adjacent room, alpha opening coefficient, B is the aperture width.

  In this means, a combination of an accurate calculation method and a simple calculation method is proposed. In the above-mentioned floor evacuation safety verification, smoke fall time is calculated for each room / area where smoke propagates from the fire side, so if there is a large error in the amount of smoke flowing out of the room near the fire, each subsequent propagation Errors in the calculation in the room overlap, and the reliability of the calculation as a whole may be impaired. On the other hand, when the number of propagation chambers is large, it is not always reasonable to perform accurate calculations for all of them. Therefore, the accuracy of calculation can be sharpened according to the distance from the fire source.

The invention according to the first means has the following effects.
○ An approximate solution with higher accuracy can be obtained compared to the calculation formula Vs = 2Aop of the Ministry of Construction notification.
○ Compared to the successive approximation method of Non-Patent Document 2, it is simple because the solution can be obtained by one calculation.
○ In principle, it is guaranteed that the approximate solution of smoke spillage is lower than the actual spillage, so rational design can be performed while thoroughly implementing the principle of human life priority.

  According to the invention relating to the second means, when there are a plurality of continuous openings to different adjacent areas in the calculation room, it is assumed that no other openings exist when calculating the smoke outflow amount from each of the openings. In other words, in the method of estimating the number of openings to be small for safety, the conventional calculation formula Vs = 2Aop and the like can more accurately approximate the outflow amount from each opening. Can improve.

  According to the invention relating to the third means, the amount of smoke flowing out from the fire chamber to the smoke propagation chamber is calculated using the more approximate expression of Equation 1, and the smoke outflow from the smoke propagation chamber to the adjacent area. Since the quantity is calculated using an approximate expression of simpler formula ○, the important part that is the center of a series of calculation operations is accurately calculated, and the leafy part is simply calculated with sharpness. Can do.

  1 to 3 are explanatory diagrams of an evacuation safety verification method according to the present invention. FIG. 1 is a diagram showing the principle of the method of the present invention, and FIG. 2 is a plan view of a verification floor to which this method is applied. In FIG. 1, R is a calculation room and N is an adjacent area.

  First, heretofore known portions of the method of the present invention will be briefly described with reference to the drawings.

  The verification method includes the steps of room evacuation safety verification and floor evacuation safety verification as described above. In addition to this, there is a process of evacuation safety verification for the entire building, but the description is omitted because it is not related to the gist of the present invention. In the room evacuation safety verification, assuming that each room on the verification floor shown in FIG. 2 is a fire room, the evacuation end time and smoke descent time are calculated for each fire room. In all verification rooms, if the former is shorter than the latter, the safety of evacuation is confirmed. The calculation method of the evacuation end time and smoke descent time is stipulated in detail in the evacuation safety verification method, and thus the description thereof is omitted. Next, in the floor evacuation safety verification, each room on the verification floor is a fire room, and the floor evacuation time required for evacuation from each fire room to the evacuation exit and the floor smoke fall time are calculated. If the floor evacuation time from any fire room is long compared to the shortest of these, the safety of evacuation from that floor is not secured.

In the present invention, when calculating the above-mentioned smoke fall time, the amount of smoke flowing out from the side closer to the fire source is calculated. The calculation method is as follows. For each room to be calculated, the above equation 1 is applied to the opening coefficient α, the opening width B, the opening upper end height H _top , the smoke layer lower end height H _s , the smoke density ρ _s , and the air. it is sufficient to assign the density ρ _a.

  Here, the opening coefficient is generally appropriately determined in the range of 0.6 to 0.7. Moreover, what is necessary is just to obtain | require smoke lower end height and smoke density by a well-known method. Specifically, the smoke lower end height is calculated by calculating the amount of smoke generated from the calorific value of the fire source, the area of the fire source and the smoke lower end height at that time, and subtracting the amount of smoke discharged from the fire room from that. It can be obtained by determining the amount of smoke present in the room and dividing this by the floor area. The smoke density can be determined by the Pascal principle at 353 / smoke temperature (K). The smoke temperature is obtained by subtracting the amount of heat that is taken out of the fire source from the calorific value of the fire source and the amount of heat that escapes from the ceiling and walls, and dividing it by the amount of smoke present in the fire room and the specific heat of the air (1.0 kJ / kg) I can do it. Of course, values obtained by other methods may be used.

While meeting room 8 of FIG. 2 is continuous to the corridor 10 through the opening d ₉ and the opening d _10, in this case, has a single opening is equivalent to these two openings. When the heights of both openings are the same, an opening having the same height and an opening width equal to the sum of the widths of both openings may be considered. Furthermore, office 1 is continuous to the front chamber 3 and the front chamber 4 through the opening d ₁ and the opening d _2, these front chamber 3 and the front chamber 4 is a separate chamber to each other. In such a case, in the smoke outflow calculated from d _1, that there is no opening d _2, also in the smoke outflow calculated from d _1, respectively calculated as there is no opening d ₂ do it.

  FIG. 3 shows the smoke outflow calculated by each method. According to the figure, an approximate solution that is larger than the exact solution and along the exact solution was obtained by the above method. In order to make this approximate solution closer to the strict solution, it seems that correction should be made by adding an appropriate parameter to the above-mentioned equation 1, but in that case, a solution that is always larger than the strict solution is obtained. The most important effect of the present invention is lost. Therefore, it is better to apply as shown in Equation 1.

It is a figure explaining the principle of this invention method. It is a top view of the verification floor which applies the method of FIG. It is the figure which compared the smoke outflow amount calculated with the method of FIG. 1 with the outflow amount calculated with the conventional method. It is explanatory drawing of the principle of the conventional method. It is another explanatory drawing of the principle of the conventional method.

Explanation of symbols

  R ... Calculated room N ... Neighboring area

Claims (3)

Using the fire room on any floor in the building or the smoke propagation room connected to it as the object of calculation, calculate the amount of smoke that flows out from this room to the next area through the opening within the unit time,
Based on this amount of smoke spill, calculate the smoke fall time until smoke falls from the ceiling to the height that becomes an obstacle to safe evacuation in the adjacent area,
In the evacuation safety verification method for judging whether or not safe evacuation is possible by comparing this smoke fall time with the evacuation time required to evacuate to the outside of the adjacent area or to the evacuation exit
The inside of the calculation room R is divided into an upper smoke layer and a lower clean air layer, and there is no difference in air density between the clean air layer and the air in the adjacent area N Assuming
An evacuation safety verification method using an approximate expression of smoke outflow, which includes approximating the mass dm _out / dt of smoke flowing out from the calculation room R to the adjacent area N per unit time by the following expression.
[Formula 1]
dm _out / dt = (2/3) αB × (H _top −H _s ) ^3/2 √ (2gρ _s | ρ _s −ρ _a |)
α: aperture coefficient, B: aperture width, H _top : aperture top height, H _s : smoke bottom height, ρ _s : smoke density, ρ _a : air density If there are multiple openings in the calculation room, of these multiple openings,
For a plurality of openings that are contiguous to the same adjacent area, calculate as one opening having an opening area equivalent to the series of openings,
The content of performing calculation on the assumption that there are no other independent openings in calculating the amount of smoke outflow from each independent opening for independent openings continuous in different adjacent areas. The evacuation safety verification method using the approximate expression of smoke outflow. When calculating the amount of smoke outflow from the fire chamber to the smoke propagation chamber and then calculating the amount of smoke outflow from the smoke propagation chamber to the adjacent area, The evacuation safety verification method according to claim 1 or 2, wherein the calculation is performed and the amount of smoke outflow from the smoke propagation chamber is calculated by the following formulas 2 and 3.
[Formula 2]
dm _out / dt = (2/3) αB × (H _top −H _o ) ^3/2 √ (2gρ _s | ρ _s −ρ _a |)
[Formula 3]
dm _in / dt = (2/3) αB × (H _o −H _s ) ^3/2 √ (2gρ _a | ρ _s −ρ _a |) + αBH _s × (H _o −H _s ) ^1/2 √ (2 gρ _a | _{ρ s -ρ a} |)
However the H _top open top height, H _s smoke lower height, H _o smoke propagation chamber and neutral zone difference in pressure of the air is zero the adjacent area height, m _out from the fire chamber runoff smoke, m _in the inflow of air from the adjacent room, alpha opening coefficient, B is the aperture width.

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