WO2017116148A1 - Method for predicting two-dimensional flame spreading velocity - Google Patents

Abstract

The present invention relates to a method for predicting a two-dimensional flame spreading velocity, and provides the method for predicting a two-dimensional flame spreading velocity, the method calculating a radiant heat flux, which is transferred by flames, for a non-combustion point of a fuel layer so as to enable the spreading velocity of flames spreading in a two-dimensional manner on a surface of the fuel layer to be predicted by using the radiant heat flux, thereby predicting the spreading velocity of flames in every direction on the surface of the fuel layer when a fire such as a forest fire breaks out, and thus, since an actual flame spreading state can be more accurately implemented and predicted, a fire can be more quickly and effectively suppressed.

Description

2D flame spread rate prediction method

The present invention relates to a two-dimensional flame spread rate prediction method. More specifically, by calculating the radiant heat flux transmitted from the flame at the unburned point of the fuel layer, it is possible to predict the diffusion rate for the flame spreading in two dimensions on the surface of the fuel layer, such as a forest fire. In the event of a fire, it is possible to predict the spread rate of the flame in all directions on the surface of the fuel layer, and thus to more accurately realize the actual spread state of the flame, thereby making the fire suppression more rapid and effective. The present invention relates to a spreading rate prediction method.

Forest fires in Korea are natural disasters that cause human and property losses as well as loss of forest resources created by reforestation after the Korean War. In Korea, 64% of the country's land is covered by forests and easy access to forests. Since the 1990s, most forest fires have been caused by artificial factors such as loss of residents and incineration of paddy fields.

In order to prevent forest fires, the government is conducting intensive surveillance activities such as setting fire protection periods, preventing entry areas, and prohibiting incineration of paddy fields in dry spring, but risks of forest fires with the increase of population seeking forests through leisure activities, etc. Is not shrinking. In particular, when a strong wind is accompanied by dry winds around the coast, it leads to large forest fires through sparking, and the damage is enormous. Therefore, the necessity of a means for predicting wildfire spread is increasing.

As a method for predicting such a fire spread, the present inventors have applied for a patent for wildfire flame spread rate prediction method (Application No. 10-2012-0018447) registered on February 23, 2012. It is assumed that the linear spreading method is used to predict the spreading rate of the flame. In view of the fact that the fire spreads in two dimensions on the surface of the fuel layer, it is difficult to accurately represent the spreading pattern.

The present invention is invented to solve the problems of the prior art, an object of the present invention is to calculate the radiant heat flux transmitted from the flame for the unburned point of the fuel layer, and use it to two-dimensionally on the fuel layer surface By making it possible to predict the spreading rate of the spreading flame, it is possible to predict the spreading rate of the flame in all directions on the surface of the fuel layer in the event of a fire such as a wildfire. It is to provide a two-dimensional flame spread rate prediction method that can more quickly and effectively suppress suppression.

The present invention relates to a two-dimensional flame spreading speed predicting method for predicting a spreading rate of a flame spreading in all directions on the fuel layer surface with respect to a flame generated in a fuel layer composed of a plurality of segments having a continuous surface. Calculating a base flame height using a heat release rate generated during combustion of the fuel layer in a fuel layer composed of a plurality of segments to have a continuous surface; (b) calculating the angle of the flame by using the basic flame height, and calculating a complex flame height in consideration of the calculated angle of the flame and the flame inclination according to the wind and the slope; (c) setting a flame center coordinate with respect to the center point of the flame in consideration of the combined flame height, and calculating a distance between the flame center coordinate and the unburned segment; (d) calculating the radiant heat flux of the flame delivered to the unburned segment using the distance between the flame center coordinate and the unburned segment; And (e) calculating the rate of diffusion of the flame on the surface of the fuel layer using the radiant heat flux of the flame, wherein in (d) the link between the flame center coordinates and the unburned segment is performed. The radiant heat flux of the flame is calculated in consideration of the angle (θ) between the straight line and the unburned segment surface, and the radiant heat flux is calculated for each of the plurality of unburned segments in all directions on the surface of the fuel layer. It provides a two-dimensional flame spread rate prediction method characterized in predicting the spread rate of the flame.

In this case, when the flame is spread to a plurality of segments of the fuel layer, in the step (c), the flame center coordinates for the flames of the plurality of segments where the flame is generated are respectively set, and each of the plurality of flame center coordinates and corresponding The distance between the unburned segments is respectively calculated, and in step (d), the radiant heat fluxes for the unburned segments can be configured to sum up all radiant heat fluxes delivered from the flames generated in the plurality of combustion segments. have.

Further, in the step (e), using the radiant heat flux for the unburned segment of the fuel layer, the ignition time at which the unburned segment is heated from the current temperature to the ignition temperature is calculated, and the ignition time is the distance from the flame. The rate of spread of the flame can be calculated by converting it to a ratio of.

According to the present invention, by calculating the radiant heat flux transmitted from the flame for the unburned point of the fuel layer, it is possible to predict the diffusion rate for the flame spreading in two dimensions on the surface of the fuel layer, In the event of the same fire, it is possible to predict the spread rate of flame in all directions on the surface of the fuel layer, which makes it possible to more accurately predict the actual spread state of the flame, which makes the fire suppression more rapid and effective. have.

1 is a conceptual diagram for calculating a radiant heat flux of a flame using a point heat source model method of a flame according to an embodiment of the present invention;

2 is a conceptual diagram for setting flame center coordinates according to an embodiment of the present invention;

3 and 4 are views for explaining the change in the viewing angle of the flame center and the ground surface on the inclined surface,

5 is a flowchart illustrating a process of a method for predicting a two-dimensional flame spreading speed according to an embodiment of the present invention;

6 to 9 are flowcharts showing the detailed process of performing the main steps shown in FIG.

10 is a diagram exemplarily illustrating test conditions for performing a 2D flame spread velocity prediction method according to an embodiment of the present invention;

11 to 13 are graphs illustrating test results of a method of predicting a two-dimensional flame spreading rate according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a conceptual diagram for calculating a radiant heat flux of a flame using a point heat source model method of a flame according to an embodiment of the present invention, FIG. 2 is a conceptual diagram for setting flame center coordinates according to an embodiment of the present invention; 3 and 4 are views for explaining the change in the viewing angle of the flame center and the ground surface on the inclined surface.

In the present invention, as a method for predicting the two-dimensional diffusion rate of the flame, a point heat source model for the flame is used.

The point heat source model is the simplest form of constituent model for the radiation source, while the more realistic radiant form generates very complex shape factor equations, while the point heat source model provides a simple relationship that changes with the inverse square of the distance R. In the case of point or spherical radiation sources, the distance R corresponds to the distance from the point heat source or the sphere center to the target.

In order to use the point heat source model, the fuel layer in which the flame is generated may be applied to a plurality of segments formed in a lattice form, and the plurality of segments are formed to have a continuous surface.

중 복사열로서 잃어버리는 비율

를 이용하여 화염으로부터 떨어진 거리의 목표점에 대한 화염으로의 복사 열선속을 간단하게 계산할 수 있다. 다시 말해, 화염으로의 복사가 지향성 없게 4π 입체각에 대하여 일정하게 방출되고 있다면 도 1에 도시된 바와 같이 화염의 중심과 수열점(수열 세그먼트)과의 거리 R을 반경으로 구면을 생각하는 것에 의해 반경 방향에 수직한 면으로의 복사 열선속(입사 열유속)

은 수학식 1과 같다.Point heat source model is the total heat generated by combustion

Ratio lost as radiant heat

We can simply calculate the radiant heat flux to the flame for the target point of distance away from the flame. In other words, if the radiation to the flame is emitted steadily with respect to the 4π solid angle without directivity, the radius is determined by considering the spherical radius as the distance R between the center of the flame and the hydrothermal point (the hydrothermal segment) as shown in FIG. Radiant heat flux (incident heat flux) on a plane perpendicular to the direction

Is the same as Equation 1.

는 열방출율(heat release rate, kW),

는 복사분율(radiation fraction), R은 화염중심점과 수열부와의 반경(radius between the center of flame and target point, m), θ는 화염중심부와 수열부와의 시야각(angle between R and Zf vector, °)이다.here,

Is the heat release rate (kW),

Is the radiation fraction, R is the radius between the center of flame and target point (m), and θ is the angle between R and Zf vector, °).

In this case, in the case of the point heat source model, the angle of view θ between the flame center point and the heat receiving portion, that is, the angle θ between the flame center coordinate and the unburned segment surface between the unburned segment of the fuel layer is taken into consideration. It is desirable to calculate the radiant heat flux of the flame for the segment.

는 수학식 2와 같다.Considering this angle θ, the radiant heat flux in the segment of the fuel layer

Is the same as Equation 2.

로 나타낼 수 있으며, R은

에 의해 구해질 수 있다. 시야각에 따른 반경의 산정은 각 개별 화염마다 각 수열부의 위치 좌표마다 개별적인 계산 과정을 거쳐야 한다.Where cosθ is

Where R is

Can be obtained by The calculation of the radius according to the viewing angle has to go through a separate calculation process for the position coordinates of each sequence for each individual flame.

As a result, Equation 2 is for the individual coordinate points of the heat receiving units for the individual flames, and the heat receiving unit heat flux may be expressed as the sum of the radiant thermal energy emitted from the individual flames as in Equation 3.

는 화염에서의 연기 발생량이 적은 것으로부터 많은 것까지 0.15~0.6의 폭을 가진다. 하지만, 연기 발생이 많은 화염의 경우에는 연기가 화염으로부터 복사를 가로막기 때문에 화염 규모가 어느 정도 커지면 반대로

는 작아진다.The calculation method shown in Equation 2 shows a good prediction result at R / r> 4 when r is a flower radius. However, when 1/2 <R / r <4, more careful calculation considering the height and shape of the flame is required. However, in the case of surface fires such as wildfires, the radiant radii of the heat source energy are relatively small compared to the open space, and the radius of the single flame of the flame is relatively short. Have Rate of Radiation

Has a width of 0.15 to 0.6 from low to high smoke generation in flames. However, in the case of highly smoked flames, since the smoke blocks the radiation from the flame, if the flame size increases to some extent,

Becomes smaller.

In order to create a two-dimensional heat transfer model, first, the grid size (segment size) of individual flames for numerical analysis must be determined. For example, 0.3m × 0.3m can be set. It can be expressed as shown in FIG. 2 for interpretation. Here, the x and y axes are position coordinates of each flame grating.

As described above, in the point heat source model method, the center position coordinates for the flame should be calculated, and the center position coordinates for the flame on the flat surface may be calculated as shown in Equation 4 based on the coordinates shown in FIG. 2.

은 화염 중심 좌표의 3차원 벡터값을 나타낸 것으로,

은

로 계산될 수 있다. 이는 수학식 5,6,7과 같이 나타낼 수 있다.On the other hand, the position coordinates of the individual flame and the heat receiving portion with respect to the inclined surface rather than flat can be expressed as shown in FIG.

Is the three-dimensional vector of the flame center coordinates.

silver

It can be calculated as This can be expressed as Equation 5, 6, 7.

Then, in the case of the flame of the cylindrical model, it can be represented as shown in Figure 4, the two-dimensional heat flux relationship for the position coordinate value changed by the slope can be expressed through the application to the cosθ expressed in Equation 8.

은 수학식 9와 같이 나타낼 수 있고,

은 수학식 10과 같이 나타낼 수 있다.here,

Can be expressed as in Equation 9,

May be expressed as in Equation 10.

These equations are reflected in the numerical calculation flow and calculated for each grid with flames.

In conclusion, the coordinate values of individual flames due to the slope can be expressed by the following equation.

First, the position of the flame center coordinate with respect to the flame on the inclined surface is as shown in Equation 11, which is summarized as in Equation 12.

In addition, the radius of the flame center and the heat receiving portion is expressed by Equation (13).

In addition, the position coordinates of the heat receiving portion on the inclined surface are expressed by Equation (14).

In addition, the position coordinates of the sequence cell are as shown in equation (15).

Through this process, the flame center coordinates can be set, and the radiant heat flux of the flame delivered to the specific segment can be calculated using the distance between the flame center coordinates and the unburned segment. At this time, the radiant heat flux of the flame is calculated in consideration of the angle θ formed between the straight line connecting the flame center coordinates and the segment and the segment surface.

In addition, the radiant heat flux of a flame for a particular unburned segment is calculated as the sum of the radiant heat fluxes of the flames delivered by each of the flames generated in the multiple segments. That is, when the flames are generated in a plurality of segments, the flame center coordinates of the flames of the plurality of segments where the flames are generated are respectively set, and the distances between the set plurality of flame center coordinates and the corresponding unburned segments are respectively calculated. Calculate the radiant heat flux from each of the multiple flames to the corresponding unburned segment. Thereafter, the total radiant heat fluxes transmitted from the respective flames can be summed to calculate a comprehensive radiant heat flux for the corresponding unburned segment.

In this way, the radiant heat flux of the flame can be calculated for a number of unburned segments, respectively, to predict the rate of spread of the flame in all directions on the surface of the fuel layer.

At this time, the method of predicting the diffusion rate of the flame by using the radiant heat flux of the flame, first, to set the ignition temperature data for the fuel layer, to obtain the thermal energy for heating the fuel layer from the current temperature to the ignition temperature, which is flame Calculate the ignition time when the unburned segment of the fuel bed is heated from the current temperature to the ignition temperature in comparison with the radiant heat flux of. The rate of diffusion of the flame can be calculated by converting this ignition time as a ratio to the distance to the flame.

FIG. 5 is a flowchart illustrating a process of a method for predicting a two-dimensional flame spreading speed according to an embodiment of the present invention, and FIGS. 6 to 9 illustrate a detailed process for performing the main steps shown in FIG. One flowchart.

The two-dimensional flame spreading rate prediction method according to the present invention is a method for predicting the spreading rate of flames spreading in all directions on the fuel layer surface with respect to the flames generated in the fuel layer. Consists of a plurality of segments.

In the two-dimensional flame spreading velocity prediction method, first, a necessary preliminary preprocessing operation is performed by performing step S1 of reading required data from defined constant data and measured data, and initial setting step S2. .

Thereafter, in step S3 of calculating a basic flame height using a heat release rate generated when combustion of the fuel layer in a fuel layer composed of a plurality of segments, and calculating a flame angle using the basic flame height, Calculating the compound flame height in consideration of the angle and the flame inclination according to the wind and the slope (S4), setting the flame center coordinates for the center point of the flame in consideration of the compound flame height, and between the flame center coordinates and the unburned segment Calculating a distance of (S5), calculating a radiant heat flux of the flame transmitted to the unburned segment by using the distance between the flame center coordinate and the unburned segment (S6), and radiating heat ray of the flame Step S7 is performed to calculate the rate of diffusion of the flame on the surface of the fuel layer using the genus. Thereafter, determining whether the flame reaches the last segment at the number of segments defined at the beginning of diffusion (S8), storing the calculation result and viewing the result (S9), and determining the time taken for the flame to reach the last segment. Perform (S10).

At this time, in the step (S6) of calculating the radiant heat flux of the flame, the radiant heat flux of the flame is considered in consideration of the angle θ formed by the straight line connecting the flame center coordinate and the unburned segment and the surface of the unburned segment. If a flame occurs on a plurality of segments, the radiant heat flux in the corresponding unburned segment is calculated by summing all radiant heat fluxes transmitted from the plurality of flames.

The radiant heat flux is then calculated for each of the plurality of unburned segments to predict the rate of spread of the flame in all directions on the fuel bed surface.

6 to 9 illustrate the detailed process of performing the main steps shown in FIG. That is, FIG. 6 reads the necessary data from the defined constant data and the measured data, FIG. 7 performs initial setting, FIG. 8 calculates the flame length, and FIG. 9 shows the flame angle according to wind and inclination. A calculation step is illustrated, and a flame spreading rate prediction method according to an embodiment of the present invention will be described with reference to FIGS. 6 to 9 as follows.

First, as shown in FIG. 6, necessary data is read from defined constant data and measured data (S11). In this case, as defined constant data, as shown in Figure 6, there is a thermal conductivity constant, Stefan-Boltzmann constant, specific heat and emissivity, etc. The measured data are the thickness of the segment of the fuel layer, the effective heat of combustion, mass reduction rate, flame Temperature, initial temperature, ignition temperature, combustion time, flame depth.

Next, as shown in Fig. 7, after setting the data for adjusting the fire range, the initial flame position is set, and the time increase value is set (S21 to S23). In this case, the data for adjusting the fire range includes the number of fuel layer segments, the size of the fuel layer segments, the initial flame depth, the inclination angle, and the wind speed.

Next, as shown in FIG. 8, after reading data for calculating the basic flame height from among the data read or set in the previous steps, the basic flame height is calculated using the data (S31 and S32). At this time, the calculation of the basic flame height may be calculated using the formula shown in FIG. 8, and may refer to the previously registered Korean Patent No. 10-1360230. Subsequently, after reading the basic flame height which is the result calculated in the previous step as shown in FIG. 9 (S41), the flame angle by the wind is calculated (S42), the flame angle by the slope is calculated (S43), Calculate the combined flame height by the wind and slope (S44). The formula used for the calculation may be calculated using the formula shown in FIG. 9, and may refer to the previously registered Korean Patent No. 10-1360230.

Next, as described with reference to FIGS. 1 to 4, the flame center coordinates are set, the distance is calculated, the radiant heat flux in the unburned segment is calculated, and the spreading speed of the flame is calculated. Subsequently, it is determined whether the last fuel layer segment is burned (S8), and if it is determined that it is burned, the result is viewed and stored (S9), and when it is time to calculate, the flame diffusion speed is calculated (S10), and it is not time to calculate If not, after the Δt time, the above-described basic flame height is sequentially performed again from the step S3 of calculating the above-described basic flame height, while if it is determined that no burning occurs, the above-described basic flame height is sequentially performed from the step of calculating the above-described basic flame height.

10 to 13 show the results of actually implementing the 2D flame spreading velocity prediction method performed in this manner.

10 is a view showing test conditions for performing a two-dimensional flame spread rate prediction method according to an embodiment of the present invention, Figures 11 to 13 is a two-dimensional flame according to an embodiment of the present invention It is a graph which shows the test result which performed the diffusion rate prediction method.

The application conditions for the flame are 12 conditions including 6 conditions at 1m / s intervals in the wind speed of 0-5m / s and 6 conditions at 10 ° intervals in the slope range of 0 ~ 5 ° / s. Was carried out. The characteristics of the pine deciduous fuel is a factor for estimating heat emission and flame height.

As shown in FIG. 10, the size of each grating was set to 0.3 m, the Y axis corresponding to the length of the flame was set to 2.7 m, and the influence distance of the heat flux of the flame was set to 5.1 m. . The total number of grids calculated is 153 grids in total. In this case, the initial fired flame grating was applied to all nine gratings of the Y axis.

According to the application conditions, the radiant heat flux distribution in the unwinded and flat conditions is reduced as the heat flux decreases with distance from the flame as shown in FIG. 11, and the heat flux of the center line of the flame distribution grid is the highest.

12 and 13, the larger the wind speed and the inclination, the larger the radiant heat flux.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims (3)

A two-dimensional flame spreading speed prediction method for predicting the spreading rate of flames spreading in all directions on the fuel layer surface for a flame generated in a fuel layer composed of a plurality of segments to have a continuous surface, (a) calculating a base flame height using a heat release rate generated upon combustion of the fuel layer in a fuel layer composed of a plurality of segments to have a continuous surface; (b) calculating the angle of the flame by using the basic flame height, and calculating a complex flame height in consideration of the calculated angle of the flame and the flame inclination according to the wind and the slope; (c) setting a flame center coordinate with respect to the center point of the flame in consideration of the combined flame height, and calculating a distance between the flame center coordinate and the unburned segment; (d) calculating the radiant heat flux of the flame delivered to the unburned segment using the distance between the flame center coordinate and the unburned segment; And (e) calculating the rate of diffusion of the flame on the surface of the fuel layer using the radiant heat flux of the flame In the step (d), the radiant heat flux of the flame is calculated in consideration of an angle θ formed between a straight line connecting the flame center coordinates and the unburned segment and the unburned segment surface. And calculating the radiant heat flux for each of the plurality of unburned segments to predict the rate of spread of the flame in all directions on the surface of the fuel layer. The method of claim 1, If the flame spreads to multiple segments of the fuel layer, In step (c) Sets the flame center coordinates for the flames of the plurality of segments where the flames have occurred, and calculates the distance between each set of flame center coordinates and the corresponding unburned segments, respectively, In step (d) The radiant heat flux for unburned segments is calculated by summing up all the radiant heat fluxes transmitted from the flames generated in the plurality of combustion segments. The method of claim 2, In the step (e) Using the radiant heat flux for the unburned segment of the fuel bed, the ignition time for which the unburned segment is heated from the current temperature to the ignition temperature is calculated, and the ignition time is converted into a ratio with respect to the distance to the flame. A two-dimensional flame spreading rate prediction method, comprising calculating the spreading rate of the.

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