Fire Source

The Fire Source tool allows you to place a scenario fire source necessary for modeling fire dynamics.

Placing a Fire Source element

A fire source is placed on the horizontal surface of any object for which a combustible Material is specified.

To activate the tool, you can either: click the button in the drawing toolbar; select Tools | Fire | Fire Source from the main menu; or use the keyboard shortcut Alt + G.

There are two instrument types which differ in the way you place a fire source:

• Automatically. The fire source will be automatically placed on the body and will occupy the largest possible rectangular area within the object’s boundaries. Select the option in the tool settings, then click on the object in the scene with the left mouse button.
• Manually. To set the fire source with this option, draw a rectangular area within the object boundaries. Select the option, move the mouse pointer to the object area, and left-click to define the corners of the shape. Right-click to exit drawing mode.

The fire source is considered to be located in the room if it is on the same floor and their horizontal projections (top view) intersect. This is one of the conditions that is taken into account when calculating the start time of evacuation.

Parameters

• Name — the name of an element located on the stage;
• Start time — time the fire source starts burning during fire modeling;
• End time— time the fire source stops burning;
• Display object name — toggle the display of the object name in the topology editor;
• Visibility — toggle the display of the object in the topology editor;
• Maximum power and Power density of the fire source are determined automatically based on the parameters of the object material (Fire load) on which the fire source is located, and the Burning Area. To change these parameters, go to Material Editor.
• Area (of combustion) — determined automatically when placing the fire source in the scenario, or set manually in the Additional Fire Source Settings for each fire source element.

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The Flame Spreading property is available in the fire simulation parameters. When this property is activated, fire spread will be simulated for the top and side faces of the object. This property does not apply to faces that are in close contact with other objects or with the floor level. When this property is activated, the law of increasing the combustion power of the fire source (in total for all faces) will work according to the selected fire development method.

Additional Fire Source Settings Window

The Additional settings window is available for setting the fire spread properties and ignition method for each placed Fire Source element. To open the window, select the fire source element in the scenario and click Additional in the object properties section.

The page contains the subsections “Properties of the fire source”, “The law of increasing the area of distribution”, a table of measured values relative to each time stamp, and graphs, visualising the data from the table for each measured value.

The window elements common for every setting are:

• Tables of measured values contain:

  • $t$ — time in seconds during the ignition process. When selecting a quadratic or linear law, the time intervals between rows are determined automatically, showing time stamps more frequently closer to the beginning of ignition and less frequently closer to the end of ignition in the table. The end of the total ignition time is determined when the maximum stable value of the measured values is reached, with several additional time stamps displayed after that. On the graph, this dynamic will be displayed as a straight line.
  • $\psi(t)$ — burn rate at a given moment in time, in kg/s. It is determined according to the selected fire spread law.
  • $S(t)$ — burning area at a given moment in time, in $m^2$. It is determined by the value of the Burning Area parameter in this additional properties window.
  • $Q(t)$ — power at a given moment in time, in $kW$. Determined by the parameters of specific combustion power, actual combustion area, and maximum combustion area. For more details, see Technical Reference Guide, on the HRRPUA value.

  The values in the table will be recalculated when switching the propagation law to linear or quadratic.

  When editing the values of interdependent parameters, the values in the table will be changed according to the set fire spread law.

• Graphs show the ratio of each measured value to time. The graphs are schematic representations.

• Marked - if there is enough oxygen. The dynamics of power reduction when the fire has depleted the oxygen resources in the room can be observed after performing fire simulation on the Results | Fire | Power tab.

• The Apply button saves all changes made in the window, and the Cancel button cancels the actions.

Properties of the fire source

The following parameters are displayed in the “Fire source characteristics” subsection:

• Power density, Maximum power, Fire spread speed are determined automatically based on the object material.
• Ignition mode. Two options are available:
  • Whole service. The fire occurs immediately across the entire area of the fire source. Its development dynamics correspond to the selected propagation law.
  • From center (forming a circle). The dynamics of its development correspond exclusively to the quadratic law of propagation. The fire begins to spread from the cell Calculation area closest to the center of the fire source, then spreads to adjacent cells.
• Maximum combustion area parameter. Determined automatically when placing the fire source on the object. You can edit the value while the ignition mode Whole service is selected. The button allows you to return to the actual fire source area determined when it was placed.

The law of fire propagation

In this subsection, you can select the fire spread law and its corresponding parameters. Available laws and their settings:

• Quadratic law. The measured values will increase according to a quadratic law until the combustion power reaches the value specified in the Maximum power field. Some of the parameters that make up the quadratic law formula, like Specific Max Burning Rate and linear flame spread rate, are defined in material properties.
• Linear law with a specified band width, in meters. Available only when selecting the Whole service fire spread type. Some of the parameters that make up the linear law formula, like Specific Max Burning Rate and linear flame spread rate, are defined in material properties.
• Custom. Available only when selecting the Whole service fire spread type. The sequence of values for each timestamp in the table is determined manually:
  • To add a new timestamp, click the button and enter the required values. Press Enter to save the changes without closing the settings window. Click Apply to save the changes and close the settings window.
  • To delete a timestamp, click on any value cell in a single timestamp row, then click the button.
  • To edit a row, click on each of the measured values, enter the desired value. Then press Enter to save the changes without closing the settings window. Press Apply to save the changes and close the settings window.