A high-efficiency smoke extraction method for large flat space with low headroom

Abstract

A system of providing a region of perpetual tenability in a built space includes a plurality of draft curtains to define the built space as a plurality of zones. A plurality of smoke sensors disposed in the plurality of zones are configured to enable a detection of a presence of smoke in any one of the plurality of zones. A controller is configured to controllably operate the plurality of draft curtains and to receive a detection signal corresponding to the detection of the presence of smoke. The plurality of extraction openings disposed in the plurality of zones are configured to be activated by the controller to enable an extraction of smoke and / or air at a respective flow rate from any one of the plurality of zones. The controller is configured to activate the plurality of extraction openings sequentially zone-by- zone.

Description

A HIGH-EFFICIENCY SMOKE EXTRACTION METHOD FOR LARGE FLAT SPACE WITH LOW HEADROOMRELATED APPLICATION

[0001] This application claims the benefit of priority to the Singapore patent application no. 10202402108X filed on July 16, 2024, the contents of which are hereby incorporated by reference in their entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to fire safety in built environments and more particularly to smoke management in a large and flat built space with low head room.BACKGROUND

[0003] It is increasing common to find underground spaces in densely populated cities put to a variety of use that can involve human occupancy or human traffic, including but not limited to underground garages and underground subway station halls. Fire safety is always a concern. For example, China patent application no. CN106677823A sought to address smoke management in a subway platform. China patent application no. CN112282823A sought to address smoke management in a road tunnel fire.

[0004] Many underground spaces are built to be large in terms of floor area with low headroom as the building cost for this combination is more cost efficient. Such underground spaces can pose unique fire safety concerns, not the least of which are the technical difficulties faced in the management of smoke in the event of a fire.SUMMARY

[0005] In one aspect, a system of providing a region of perpetual tenability in a built space. The system includes a plurality of draft curtains, a plurality of smoke sensors, a controller, and a plurality of extraction openings. The plurality of draftcurtains define the built space as a plurality of zones. The plurality of smoke sensors being disposed in the plurality of zones and configured to enable a detection of a presence of smoke in any one of the plurality of zones. The controller is configured to controllably operate the plurality of draft curtains and to receive a detection signal corresponding to the detection of the presence of smoke. The plurality of extraction openings may be disposed in the plurality of zones and configured to be activated by the controller to enable an extraction of smoke and / or air at a respective flow rate from any one of the plurality of zones. The controller is configured to activate the plurality of extraction openings sequentially zone-by-zone.

[0006] The system may be configured to be responsive to at least one of the plurality of extraction openings being activated and to provide a total flow rate of extraction from the built space for any number of the plurality of extraction openings being activated, in which the total flow rate is a constant.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] To aid understanding, various embodiments of the present disclosure will be described with reference to the following figures:

[0008] FIG. 1A shows a schematic illustrating a front view of a large flat space with low headroom, according to an embodiment of the present disclosure.

[0009] FIG. 1 B shows images illustrating various examples of large flat spaces with low headroom.

[0010] FIG. 2 shows a schematic illustrating a front view of a large flat space divided by draft curtains into multiple zones, according to another embodiment of the present disclosure.

[0011] FIGS. 3A and 3B show a flow chart illustrating a method of configuring and performing the sequential activation and sharing of the total flow rate, according to an embodiment of the present disclosure.

[0012] FIG. 4 shows a plot of flow rate (in m3 / s) as a function of time, illustrating an extraction flow rate distribution and the Engineered Smoke Control (ESC) system’s triggering procedure.

[0013] FIG. 5A, FIG. 5B, and FIG. 5C are schematic plots of the flow rate over time for different activation schemes listed in Table 1.

[0014] FIG. 6A shows a top view of the building model layout used in the Computational Fluid Dynamics (CFD) simulation studies described in the present disclosure.

[0015] FIG. 6B shows a front view of the building model layout of FIG. 6A.

[0016] FIG. 7 shows the fire curve used in the simulation studies.

[0017] FIG. 8 shows a schematic illustrating a front view of the layout in a first set of simulations as summarized in Table 2.

[0018] FIG. 9 shows an image illustrating a top view of a smoke plot captured at 1800 seconds at a flow rate of 11 m3 / s in the first set of simulations.

[0019] FIG. 10 shows an image illustrating a top view of a smoke plot captured at 1800 seconds at a flow rate of 27 m3 / s in a second set of simulations as summarized in Table 2.

[0020] FIG. 11 shows a schematic isometric view illustrating insufficient extraction in the first and second sets of simulations.

[0021] FIG. 12 shows a schematic illustrating a front view of the layout in the third set of simulations as summarized in Table 2.

[0022] FIG. 13 shows an image illustrating a top view of a smoke plot captured at 1800 seconds at a flow rate of 16 m3 / s in the third set of simulations.

[0023] FIG. 14 shows a schematic isometric view illustrating insufficient extraction in the third set of simulations.

[0024] FIG. 15 shows a schematic illustrating a front view of the layout in the fourth set of simulations as summarized in Table 2.

[0025] FIG. 16 shows an image illustrating a top view of a smoke plot captured at 1800 seconds at a flow rate of 16 m3 / s in the fourth set of simulations.

[0026] FIGS. 17A to 17D show smoke plots or visibility distributions corresponding at a safety height of 2.5 meters.DETAILED DESCRIPTION

[0027] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes of illustration. Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments, even if not explicitly described in these other embodiments. Additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0028] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. As used herein, the singular ‘a’ and ‘an’ may be construed as including the plural “one or more” unless apparent from the context to be otherwise. In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0029] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0030] In the context of various embodiments, the term “about" or “approximately" as applied to a numeric value encompasses the exact value and a reasonable variance as generally understood in the relevant technical field, e.g., within 10% of the specified value.

[0031] Terms such as “first" and “second” are used in the description and claims only for the sake of brevity and clarity, and do not necessarily imply a priority or order, unless required by the context.

[0032] Some methods may be described in terms of steps, stages, phases, or the like, merely to aid understanding and / or for convenient reference. The delineation between one step and another step may be merely for convenient reference in the present disclosure. It will be understood that in actual implementation there may not be a clear division or transition from one step to another subsequent step. There may be a certain amount of overlap among thesteps and / or more than one step may occur or be performed concurrently in time, etc., unless the context dictates otherwise.

[0033] Although the terms “large” and “low” may appear to be relative terms, a person skilled in the art of fire safety would appreciate it to refer to a well-known type of built environment. To further aid understanding, a schematic diagram illustrating a “large flat space with low headroom” is shown in FIG 1 A. In the present disclosure, the terms “space”, "built space", and “enclosed space” may be interchangeably used in referring to a room or an interior of a building. In the present disclosure, the term “flat” refers to the ceiling of the built space being relatively planar or having a similar volume of headroom space throughout the floor area of the built space (as opposed to having a domed shape or other shapes). In the present disclosure, the term “large flat spaces with low headroom” refers to an interior of a built structure or a built space with a floor area that is large (e g., a size comparable to a football field) relative to the height of the ceiling, and in which the distance between the finished surface of the floor and the ceiling is about one storey high.

[0034] To further illustrate, FIG. 1 B shows images of examples of large flat spaces with low headroom, e g., underground garages or carparks, halls of subway stations, libraries, and workshops. Other examples of large flat spaces with low headroom include but are not limited to underground shopping malls, basement levels of shopping malls, and some underground train stations. Not all large flat spaces with low headroom are underground. Other examples of large flat spaces with low headroom include some libraries or archives, some factories, etc. Embodiments of the present disclosure may be applicable to both underground and aboveground large flat spaces with low headroom.

[0035] In the case of underground structures, there are no windows or openings at the walls of the structures. In the case of aboveground structures, the floor area is so large that there is a substantial area that is so far away from any window that any air movement in the area is not affected by an exchange of air via the window.

[0036] Large flat spaces with low headroom have the characteristics of large open spaces but with a low headroom and a flat ceiling. Large flat space with lowheadroom presents unique challenges to smoke management for several reasons. This can be understood by comparing a high ceiling structure with the same total floor area which has been subdivided into many smaller rooms with fireproof doors. In the event of a fire, the smoke from the fire can displace air (and oxygen) and cause suffocation, amongst other problems. If the ceiling is high (large headroom), the smoke can gather under the ceiling while leaving a layer of air near the floor. If there are many smaller rooms, the doors can be shut to contain the spread of the smoke. In the large space, the smoke can spillover or spread across the entire area of the floor with little or no hindrance. The large, enclosed space acts like a large open space when it comes to the spread of spillover smoke.

[0037] In the flat space with low headroom, the available space for a “smoke reservoir” is characterized by a shallow depth. In the flat space, there are no hollowed regions in the ceiling to serve as a holding area for the smoke. In the space with a low headroom, the smoke that collects under the ceiling can quickly fill up the entire space between the ceiling and floor. It can thus be understood that a large flat space with a low headroom can become quickly untenable in the event of a fire.

[0038] In the present disclosure, the terms “tenable”, “untenable”, “tenancy”, "tenability" and the like are used in the context of fire safety engineering and relates to whether a built space can be safely occupied by a person.

[0039] Various jurisdictions may impose different criteria for tenability. In the present disclosure, a built space may be deemed tenable if all of the following conditions are satisfied:(a) Smoke Temperature - The average upper layer smoke temperature shall not exceed 200 °C (degrees Celsius) measured at a height of 2.5 m (meters) from the finished floor level and the average lower layer smoke temperature shall not exceed 60 °C.(b) Radiation - Where occupants are expected to egress past a fire, the radiative heat flux shall not exceed 2.5 kW / m2(kilowatts per square meter).(c) Visibility - Visibility at 2.5 m above the floor level shall be greater than 10 m.

[0040] Based on this set of criteria, some jurisdictions impose regulations requiring performance-based fire safety system designs (combination of fire detection, fire suppression and smoke management) to achieve ASET (Available Safety Egress Time) > 2 x RSET (Required Safety Egress Time). In other words, the fire safety system designs should be able to maintain at least a region of the built space as tenable for a period at least twice as long as that required by all occupants to egress the space in the event of a fire.

[0041] The challenge is that the tenability acceptance criteria essentially require the smoke to be kept above 2.5 m from the finished floor level, i.e., the depth of the smoke reservoir is limited by the depth between 2.5 m and the structural ceiling of the built space. In large flat spaces with low headroom, the available smoke reservoir is so shallow that the strength of the fire plume from an intense fire source can quickly overwhelm the smoke reservoir and spillover, resulting in a failure to meet the tenability acceptance criteria and thereby compromising the safety of the egressing occupants.

[0042] Some jurisdictions go one step further and impose additional safety requirements for specific situations. For example, for buildings or facilities of national or cultural importance (such as the airport, large-scale indoor gardens, art galleries, museums, etc.), some fire safety authorities impose heightened safety requirements of perpetual tenability (i.e., the fire safety system should be able to maintain tenability perpetually in the space).

[0043] In practice, as described above, the “ASET > 2 x RSET” tenability criteria are difficult to meet in the case of large flat spaces with low headroom. It can be appreciated that additional technical challenges abound in trying to meet the perpetual tenability criteria in the case of large flat spaces with low headroom.

[0044] To achieve perpetual tenability, i.e., to maintain a perpetually tenable space, one approach has been to provide a zone of tenability outside a boundary away from a perimeter of the fire. For example, some fire safety codes require a zone of perpetual tenability to be provided as far as 30 m away from the perimeter of the fire. To achieve this, it has been found that a very high exhaust rate would be required. In some examples (not involving large flat spaces), more space had to beallocated for exhaust and supply ducts, as well as for high-powered electromechanical systems to drive the exhaust system. In the case of large spaces with low headroom, achieving perpetual tenability is not a matter of simply installing more high-powered exhaust systems, owing to the challenging characteristics described above.

[0045] It can be appreciated that tenability is an important objective. Some of these sites of historical or cultural significance can see hundreds of visitors and tourists on a daily basis. Providing perpetual tenability can better assure the safety of the visitors and tourists. Providing perpetual tenability can also better preserve key historical or cultural artifacts. Yet, for sites of historical or cultural significance, it would defeat the purpose if part of the historical or culturally significant structure has to be destroyed in order to install a smoke management system of sufficient power.

[0046] In one aspect, embodiments of the present disclosure relate to a system and method of limiting the untenable area to no more than three zones, one of which is the zone in which the fire occurs, in a large flat space with low headroom, and creating a region of perpetual tenability outside of the untenable area. The three zones which are allowed to be untenable are defined such that the length of the three zones is preferably the length of the fire source's long side plus 2 times the required distance, the required distance being measured from the perimeter of the fire to a region of perpetual tenability. In other words, four of the plurality of draft curtains may be spaced apart to define the first zone, the second zone, and the third zone as three sequentially adjacent zones, with the first zone defined between the second zone and the third zone. The region of perpetual tenability may be defined outside the three sequentially adjacent zones.

[0047] In another aspect, embodiments of the present disclosure relate to a system and method of providing one or more zones of perpetual tenability in a large flat space with low headroom.

[0048] Referring again to FIG. 1A, various embodiments of the present disclosure relate to a system and a method of providing one or more zones of perpetual tenability in a built space 100, including but not limited to a large flat spacewith low headroom. The built space 100 may be defined as or divided into multiple zones 300 using draft curtains 200. The large flat space with low headroom is configured with an Engineered Smoke Control (ESC) system, also known as a smoke and heat exhaust ventilation (SHEV) system. The ESC system may include fire / smoke sensors (also referred to herein as "smoke sensors" 500 for the sake of brevity), a controller configured to activate extraction openings, exhaust fan speed controllers to control extraction flow rates at the extraction openings 400, actuators to operate draft curtains 200, etc. In some examples, draft curtains 200 may be used to divide the built space 100 into multiple zones 300, in which the zones 200 are in fluid communication with one another even when the draft curtains 200 are fully extended or fully dropped down from the ceiling. In some examples, the ESC includes a single controller configured to control the extraction openings in all of the zones 300, in which the extraction openings 400 in any one zone may be operated independently of other zones. In other examples, the ESC includes at least one smoke sensor 500 in each of the zones 300, the at least one smoke sensor 500 being configured to operate (e.g. , activate) only the one or more extraction openings 400 disposed in the same zone 300 as the at least one smoke sensor 500. There being a wide variety of fire / smoke sensors in the market, the present system and method may be implemented using any of the various types of hardware. For the sake of brevity, in the present disclosure, it would be understood that reference to a controller may include a controller that is provided external to a smoke sensor or a controller that is integrated as part of the smoke sensor. In some examples, the controller may be a computing device and / or an external controller provided outside the built space 100. For the sake of brevity, the term "controller" as used herein will be understood to include such and other various possible processor, controller, module, computing device, etc., that are programmable and configurable to receive a detection signal from the smoke sensors, and in response thereto operate the draft curtains and / or activate selected extraction openings.

[0049] FIG. 2 schematically illustrates a front view (or a side view) of an example in which multiple draft curtains 200 are provided to divide a large flat built space 100 into multiple zones 300. In some examples, the drop-down depth of each of thedraft curtains 200 is the depth between structural ceiling to a safety height (2.5 m from the finished floor) or the maximum allowable depth of the smoke reservoir (also referred to as the smoke reservoir depth).

[0050] The draft curtains 200 may be commercially available draft curtains used in constraining a lateral spread of smoke, e.g., draft curtains suitable for constraining a spread of smoke across the floor area of the space.

[0051] According to various embodiments of the present disclosure, a method of providing one or more zones 300 of perpetual tenability in a large flat built space 100 with low headroom includes identifying or defining three zones 300 for extraction, e.g., a fire zone 310 (where fire is detected) and two adjacent zones 320. Each of the two adjacent zones 320 is a zone immediately adjacent to the fire zone 310 in which fire has not been detected at the time instant.

[0052] For example, in response to detecting a fire occurring in one of the multiple zones, the draft curtains 200 are lowered, diving the built space 101 (originally a large space) into multiple zones 300. The ESC system is configured to be activated in the fire zone 310 (the zone in which the fire occurs) and two adjacent zones 320. If the smoke can be constrained within these three zones, the criterion of having a 30 m zone of tenability (as mentioned above) would be satisfied.

[0053] According to various embodiments of the present disclosure, a method of configuring and providing perpetual tenability in a large flat built space with a low headroom includes a sequential activation (e.g., sequential activation of zones of extraction openings) and sharing of the total flow rate, as shown in FIG. 3A and FIG. 3B

[0054] For the sake of brevity, in the present disclosure, the terms “flow rate” and “exhaust flow rate” may be used interchangeably to refer to the rate of extraction of smoke. The term “total flow rate" refers to the total rate of extraction of smoke from the built space as a whole.

[0055] All extraction openings within each zone remain closed by default unless activated. The one or more extraction openings within each zone will open or be activated only if triggered by a detection signal and if specified conditions aresatisfied, as will be elaborated below. Each zone may be associated with a flow rate, regardless of the number of extraction openings provided in the zone.

[0056] A configuration process for the proposed method may be described in four steps merely to aid understanding and not to be limiting.

[0057] Step 1 : Identifying at least one worst-case scenario.

[0058] In this step, a compartment space model is built using a computational fluid dynamics (CFD) software. The input parameters may include but are not limited to a fire size, a fire growth rate, a fire location, and an extraction flow rate. Reference may be made to published fire safety codes of the applicable jurisdictions or to other published fire safety guidelines such as, but not limited to, the Singapore Fire Safety Engineering Guidelines (2015) (published by the Singapore Civil Defence Force), the BR 368 guidelines (1999) by H.P. Morgan et al. (available from HIS BRE Press, United Kingdom), or the NFPA 92 Standard (available from the National Fire Protection Association, Massachusetts, United States of America) to determine a set of parameters that describe one or more possible scenarios where a fire breaks out in the large flat space with low headroom .

[0059] Various fire scenarios may be simulated. At least one worst-case scenario may be identified based on the criteria of smoke temperature, radiation, and visibility.

[0060] Step 2: Compartmentalizing the space.

[0061] The large flat space with low headroom is divided into multiple zones (also referred to as smoke zone) using draft curtains. In actual implementation, the draft curtains may be installed at various locations on the ceiling. By default, the draft curtains are retracted out of the way. In response to a detection of a fire or smoke in the large flat space with low headroom, all the draft curtains will be extended from the ceiling. In this manner, the draft curtains would divide the large flat space into multiple zones.

[0062] Preferably, each draft curtain drops down or extends to a safety height. For example, if the applicable fire code requires the minimum ceiling height for habitable spaces, as measured from the finished floor surface to the lowest point of the ceiling, to be 2.5 m, each draft curtain should extend from the ceiling to leave aclearance of at least 2.5 m (the safety height) from the finished floor surface. In other words, the draft curtains do not extend all the way from the ceiling to the finished floor surface. The draft curtains may be described as dividing the headroom space into zones (or smoke holding zones), leaving a large contiguous space of at least the safety height (as measured from the finished floor surface).

[0063] Step 3: Determining the criteria for perpetual tenability and the criteria for untenable area.

[0064] In some examples, the criteria of perpetual tenability and the criteria for untenable area may take reference from the applicable fire safety code or guidelines. To aid understanding and not to be limiting, the following examples and experiments made reference to the Singapore Fire Safety Engineering Guidelines (2015) (published by the Singapore Civil Defence Force) or the NFPA 130 Standard for fixed guideway transit and passenger rail systems (available from the National Fire Protection Association, Massachusetts, United States of America).

[0065] Step 4: Determining the sequential activation and total flow rate.

[0066] The total flow rate may be determined based on the BR 368 guidelines. The extraction openings in the fire zone and in two zones immediately adjacent the fire zone are configured to activate in a sequential manner, e g., one after another at different time instants. All the zones with activated extraction openings are configured to share a total flow rate, e.g., contribute equally to a total flow rate. In other words, all the zones with activated extraction openings are configured to have the same flow rate.

[0067] A fire dynamics simulator (FDS) can be executed based on the parameters determined above. Based on the results, the total flow rate to be used can be determined. To further aid understanding, examples are described below.

[0068] Example

[0069] As any time instant, all the zones with at least one activated extraction opening are configured to contribute equally to the total flow rate, with all other nonactivated extraction openings closed by default. Concurrent with the sharing of the total flow rate, the extraction openings are opened in a sequential manner (also referred to as “sequential activation”).

[0070] For example, in an initial stage, in response to a fire or smoke detected in a zone (also referred to as the “fire zone”), only the extraction openings in the fire zone are activated. The one or more extraction openings in the fire zone are activated to provide a total flow rate. The total flow rate may be predetermined by the configuration process described above.

[0071] Subsequently, in a first spillover stage, one or more of the extraction openings in a first adjacent zone (adjacent zone 1 ) may be activated in response to smoke from the fire zone spreading to the first adjacent zone. The first adjacent zone is a zone immediately adjacent to the fire zone. In the first spillover stage, the flow rate for the first adjacent zone is set to be the same as the flow rate for the fire zone, with the total flow rate of the space in the first spillover stage remaining the same as the total flow rate of the space in the initial stage.

[0072] Subsequently, in a second spillover stage, one or more of the extraction openings in a second adjacent zone (adjacent zone 2) may be activated in response to smoke from the fire zone spreading to the second adjacent zone. The second adjacent zone is another zone immediately adjacent to the fire zone and distinct from the first adjacent zone. In the second spillover stage, the flow rate for the second adjacent zone is set to be the same as the flow rate for the first adjacent zone, which is also set to be the same as the flow rate for the initial zone. In the second spillover stage, the total flow rate of the space in the second spillover stage remaining the same as the total flow rate of the space in the first spillover stage or in the initial stage.

[0073] FIG. 4 illustrates one aspect of the proposed method in terms of a triggering procedure and extraction flow rate distribution controlled by the controller of the ESC system. More specifically, FIG. 4 is a plot of flow rate (in m3 / s) as a function of time. To aid understanding, the proposed method may be described in three stages:

[0074] (a) Initial stage.

[0075] In the initial stage, all the extraction openings within the fire zone are activated, sharing the total flow rate, i.e., Vtotal fiow rate.

[0076] (b) First spillover stage.

[0077] In the first spillover stage, if the fire zone cannot accommodate the smoke (e.g., due to the low headroom providing a limited space to serve as a smoke reservoir) and if the smoke spills over the to the first adjacent zone (adjacent zone 1 ), the extraction openings within the first adjacent zone will be triggered and activated. To keep the total flow rate constant, the extraction openings within the fire zone and first adjacent zone are configured so that both of these two zones share the total flow rate. For example, the respective flow rates of each of the fire zone and the first adjacent zone are set to Vtotalflow rate.

[0078] (c) Second spillover stage.

[0079] In the second spillover stage, if the smoke spills over a second adjacent zone (adjacent zone 2), the exhaustion openings within the second adjacent zone are triggered and activated. The exhaustion openings within the fire zone, the first adjacent zone, and the second adjacent zone are configured so that all of these three zones share the total flow rate. For example, the respective flow rates of each of the fire zone, the first adjacent zone, and the second adjacent zone are set to3vtotal flow rate-

[0080] Comparison

[0081] FIG. 5A to FIG. 5C further compare the sequential activation of the exhaustion openings with various conventional methods.

[0082] FIG. 5A shows an incremental or sequential activation scheme in accordance with embodiments of the proposed method described above. At time = 0, only the fire zone is activated (i.e., only the extraction openings within the fire zone are activated) to operate at a total flow rate. At time = T 1 second, the extraction openings in the fire zone remain activated, and the extraction openings in the first adjacent zone are activated. All the activated zones are configured to each operate at a flow rate ofVtotaifiow rate- At time = T2 second, the extraction openings in the fire zone and the extraction openings in the first adjacent zone remain activated, and the extraction opening sin the second extraction zone are activated. All the activated zones are configured to each operate at a flow rate of ^ Vtotal flow rate.The flow rate at any time instant would be mainly used to exhaust the smoke and not to exhaust fresh air. This enhances the efficiency of the ESC system.

[0083] FIG. 5B shows a one-step activation scheme in accordance with a conventional method. Assuming that the space is divided into three zones, the exhaust openings in all three zones are activated at the same time from the beginning, regardless of whether there is smoke or fire in the respective zones. This means that if smoke is present in only one of the three zones, the extraction openings in two smoke-free zones will be extracting fresh air out of the space.

[0084] FIG. 5C shows another one-step activation scheme in accordance with another conventional method. Assuming the space is divided into multiple zones of more than three zones (n > 3), the exhaust openings in all of the multiple zones are activated at the same time. In this case, the exhaust openings in all of the multiple zones are activated at the same time from the beginning, regardless of whether there is smoke or fire in the respective zones. This means that if smoke is present in only one of the multiple zones, the extraction openings in all other zones will be extracting fresh air out of the space. That is, only a very small portion of the flow rate works on the extraction of the smoke. A large portion of the flow rate (e.g., in zones relatively far away from the fire) extracts fresh air from the space.

[0085] It can also be seen from FIG. 5A to FIG. 5C that the proposed method (FIG. 5A) has the largest extraction volume, i.e.,

[0086] It can further be seen from FIG. 5A to FIG. 5C that the proposed method (FIG. 5A) has the largest average extraction flow rate per unit area, i.e.,

[0087] The proposed method of sequential activation and sharing of the total flow rate not only improves the efficiency of exhaustion but also more effectively constrains smoke within a smaller area.

[0088] Simulations and Experiments

[0089] A building model may include various aspects, include computational fluid dynamics modelling, fire size, growth rate, and soot yield, etc.

[0090] (a) CFD modelling

[0091] The proposed method of sequential extraction and sharing of the total flow rate was numerically validated in a large flat compartment space with a low headroom. FIG. 6A and FIG. 6B respectively show a top view and a front view of a layout of a building model of the built space.

[0092] The dimensions of the space are 58 m (length) x 20 m (width) x 4 m (height). Each side of the space has two doors, and the size of each door is 1 .75 m (width) x 2.0 m (height).

[0093] The space was configured with an ESC system that includes an exhaust and supply system.

[0094] Various scenarios were simulated for different locations of the fire in the space. It was determined that the worst-case scenario would be the scenario in which the fire started in the center of the space.

[0095] A computational fluid dynamics software, e.g., Fire Dynamic Simulator (FDS) 6.8.0 version, available from the National Institute of Standards and Technology (https: / / pages.nist.gov / fds-smv / index.html), was used to perform the simulations. According to the FDS user’s guide available from the same source, the characteristic diameter of fire source D” may be closely related to the grid precision:where Q is the total heat release rate,is the air density, kg / m3Cpis the specific heat of air, kj • (kg ■ / f)-1; Tmis the ambient temperature, K ; g is the gravitational acceleration, m2 / s.

[0096] The quantity D* / 8Xcan be thought of as the number of computational cells spanning the characteristic diameter of the fire. The value of D* / 8Xmay be in the range of 4 to 16. In the simulation conducted, the value of D* / 8Xwas 10.

[0097] The more cells spanning the fire, the better the resolution of the calculation, and the longer the calculation time. Considering the independence of the mesh cell and the computing costs, the mesh cell was set at 0.1 m. To makethe calculation faster, a multi-mesh was used in the simulation. A total of 10 meshes were used and the total number of the cells in model was 6240000. The property of the mesh boundaries was set as open.

[0098] (b) Fire size / growth rate and soot yield

[0099] The fire heat output was taken to be 1 MW with a 14 m perimeter of the fire, based on the Singapore fire code (Code of Practice for Fire Precautions in Buildings, 2023). The fire growth rate was assumed to be a fast fire (a=0.047) based on the Singapore Fire Safety Engineering Guidelines. The design fire curve used in the simulation studies is shown in FIG. 7. In the fire curve, the heat release rate (HRR), measured in kilowatts (kW), is plotted as a function of time in seconds (s). The soot yield is 0.1 g / g (grams of soot generated for every gram of fuel burned).

[0100] (c) ESC system configuration

[0101] In the simulation conducted, as shown in FIG. 6A and FIG. 6B, the space or the building model included ten (10) ESC extraction openings of the same size of 1.25 m (length) x 1.0 m (width) installed under the ceiling and four (4) supply openings of the same size of 1.5 m (length) x l.O rn (width) placed at the ends of the space. In the present context, supply openings refer to the air ducts for a supply of fresh air to the space.

[0102] Each side has two (2) doors with dimensions of 1.75 m (width) x 2.0 m (height), which were opened in the simulation.

[0103] To control 1 MW fire smoke, the required total flow rate V may be estimated based on the NFPA 92 Standard (5.4 m3 / s) and the BR 368 guidelines (11 m3 / s). To be more onerous, 11 m3 / s was selected as a starting point of a total flow rate in the simulation.

[0104] The required inlet supply air was 80% of the exhaust rate: Vsuppiy= O.SP’e / njusj.

[0105] Table 1 shows the flow rates and distribution for three conventional smoke extraction or activation schemes.Table 1

[0106] FIG. 8 is a front view of the layout in a first set of simulations and a second set of simulations. FIG. 9 is a top view showing a smoke plot at 1800 seconds (from the start of the fire) in the first set of simulations. FIG. 10 shows a smoke plot at 1800 seconds in the first set of simulations.

[0107] In the first set of simulations of Table 1, a constant flow rate 11 m3 / s was applied. This value was calculated based conventional methodologies of the BR 368 guidelines (which do not specifically cater for the large flat space with low headroom). The specified flow rate of 11 m3 / s achieved an Available Safe Egress Time (ASET) of 360 seconds but failed to achieve perpetual tenability. This result was graphically illustrated in smoke plots such as that of FIG. 9. At 1800 seconds, the entire space was filled with smoke. Perpetual tenability in the large flat space with low headroom was not achievable in the conventional ESC system, even if the conventional ESC system was code compliant.

[0108] The same layout used in the first set of simulations was used in the second set of simulations of Table 1. In the second set of simulations of Table 1 , the flow rates were set at different constant values from 11 m3 / s to 27 m3 / s, to investigate whether perpetual tenability could be achieved merely by using a high enough flow rate. It was found that the minimum flow rate at which perpetual tenability could be achieved for a large flat space with low headroom was 27 m3 / s. FIG. 10 shows the smoke plot at 1800 seconds in the form of a top view of the space. FIG. 10 shows a slight improvement over the case of FIG. 9.

[0109] In the first set of simulations and the second set of simulations of Table 1 , all the extraction openings were activated from the time the fire started, i.e., the ESC system was fully activated as a whole, from the beginning of the fire. The extraction openings far away from the fire source would extract fresh air from the space instead of extracting smoke since the smoke had not yet spilled over to areas far away from the fire source. As a result, both configurations in the first set ofsimulations and the second set of simulations demonstrated inefficient extraction (and eventually insufficient extraction) of smoke from the large flat space with low headroom. FIG. 11 shows the insufficient extraction efficiency in both the first set of simulations and the second set of simulations under Table 1.

[0110] FIG. 12 is a front view of the layout in the third set of simulations.

[0111] In the third set of simulations of Table 1, the built space is divided into several zones by draft curtains (also known as smoke curtains). Each zone was about 10.8 m wide (e.g., draft curtains were about 10.8 m apart from one another). When a fire happened at a fire zone, the extraction openings within the fire zone and two zones (adjacent zones) on either side of the fire zone (middle fire) were immediately activated along with fire confirmation. The results show that the minimum flow rate required to achieve smoke extraction within the zones is 16 m3 / s. A top view of the corresponding smoke plot at 1800 seconds is shown in FIG. 13.

[0112] In the third set of simulations of Table 1 , the ESC system was configured with simultaneous activation of the extraction openings in the fire zone and in two zones on either side of the fire zone. Before smoke spilled over to the two zones on either side of the fire zone, the extraction openings in the two zones extract fresh air out from the space rather than smoke.

[0113] FIG. 14 shows the low extraction efficiency in the third set of simulations of Table 1. The flow rate distributed in the two adjacent zones is exhausting the fresh air.

[0114] A fourth set of simulations was carried for a large flat space with low headroom, based on the configuration as shown in FIG. 5A, according to embodiments of the present disclosure. Draft curtains were extended to divide the space into zones. In the fourth set of simulations, extraction openings were activated in a sequential manner, in accordance with embodiments of the present disclosure. FIG. 15 shows a front view of the layout simulated.

[0115] In the fourth set of simulations, at time = T1 , a fire was detected within a first zone (fire zone) by a first detector disposed in the first zone, the first detector was configured to trigger the activation of one or more first extraction openings within the first zone. The one or more first extraction openings were activated toprovide a first flow rate at which smoke and / or air was extracted from the first zone. As no other zones had activated extraction openings at this time, the first flow rate was also the total flow rate.

[0116] In the fourth set of simulations, at time = T2 and subsequent to T1 , smoke from the fire entered a second zone (first adjacent zone) and was detected by a second detector which was disposed in the second zone. The second detector was configured to activate one or more second extraction openings within the second zone. The one or more second extraction openings were activated to provide a second flow rate at which smoke and / or air was extracted from within the second zone. The one or more first extraction openings and the one or more second extraction openings were controllably operated to provide the total flow rate, in which a first flow rate at the first zone was configured to provide half of the total flow rate, and in which the second flow rate was configured to provide half of the total flow rate.

[0117] In the fourth set of simulations, at time = T3 and subsequent to T2, smoke from the fire entered a third zone (second adjacent zone) and was detected by a third detector which was disposed in the third zone. The third detector was configured to activate one or more third extraction openings within the third zone. The one or more third extraction openings were activated to provide a third flow rate at which smoke and / or air was extracted from within the third zone. At this time, the first flow rate, the second flow rate, and the third flow rates were set to be the same as one another, with the total flow rate being kept constant relative to the total flow rate before time = T3. The total flow rate at this time was the sum of the first flow rate, the second flow rate, and the third flow rate.

[0118] For the sake of comparison, the total flow rate used in the fourth set of simulations may be set to be the same as the total flow rate used in the third set of simulations, e.g., 16 m3 / s. It could be seen in the fourth set of simulations that, contrary to expectations, a staggered or sequential activation did not result in significant wastage. Smoke spilled out of the first zone (fire zone) within a relatively short period of time (e.g., 150 seconds), such that not much of the power spent on extraction was wasted on extracting fresh air. FIG. 16 shows a top view of a smokeplot at 1800 seconds in the fourth set of simulations. As evident in FIG. 16, the minimum flow rate required to keep smoke within the zones with activated extraction openings (extraction zones) can be still around 16 m3 / s.

[0119] Table 2 shows the results of the four sets of simulations in terms of the available safe egress time (ASET) and tenability.Table 2

[0120] FIG. 17A to FIG. 17D also serve as an indication of the visibility. Visibility is often the first parameter to be breached among the various acceptance criteria. FIG. 17A to FIG. 17D correspond to the four sets of simulations (described above) at 1800 seconds, i.e. , as an indication of the visibility distribution at the safety height of 2.5 m. The darker shaded areas denote visibility of 10 m (corresponding to untenable areas) or poor visibility, and the lighter shaded areas denote visibility at more than 10 m (corresponding to tenable areas) or good visibility.

[0121] The conventional configuration tested in the first set of simulations would appear to be inadequate in view of the results. As can be seen from FIG. 7A, smoke had reached the entirety of the space and perpetual tenability could not be achieved. In other words, both visibility and tenability were lost.

[0122] As the results of the second set of simulations, FIG. 17B shows the least amount of smoke in the space and the best visibility among all the four sets of simulations. Nonetheless, some smoke had spread beyond the fire zone as well as beyond the two zones immediately adjacent the fire zone. In this case, perpetual tenability was achieved at the price of a relatively high flow rate of 27 m3 / s.

[0123] In the third set of simulations, with the minimum flow rate required to achieve perpetual tenability being set at 16 m3 / s (which was lower than that required in the second set of simulations), it could be seen from FIG. 17C that the area of losing tenability could be constrained within three zones. The area of losing tenability can also be referred to as the area that lost tenability of the area that could not maintain tenability. Based on the area of the dark regions, it can be appreciated that the visibility in the case of FIG. 17C was relatively poor.

[0124] The proposed method, as demonstrated by the fourth set of simulations, was shown to be capable of providing perpetual tenability. FIG. 17D shows the smoke plot with a larger tenability as compared to the case in any of the other sets of simulations. The proposed method is clearly an improvement over the conventional methods. Having a smaller area that lost tenability or having a larger area that maintained perpetual tenability can result in more lives being saved or less damage to invaluable historical or cultural heritage.

[0125] In terms of visibility, FIG. 17D clearly had the better visibility compared to FIG. 17C.

[0126] The results as observed in the case of FIG. 17D established the superiority of the proposed method (corresponding to the fourth set of simulations), in which the proposed system and method was capable of providing perpetual tenability with a smaller untenable area, while retaining better visibility in even in the areas of lost tenability.

[0127] Other Benefits

[0128] The proposed method enables the smoke to be constrained within a smaller space compared to conventional methods, and facilities the provision of perpetual tenability in a large flat space with low headroom. To provide perpetual tenability in the case of a 1 -megawatt (MW) fire, it has been demonstrated that the proposed method enables a reduction of the required mechanical extraction flow rate by as much as 40.7 % compared to conventional methods. The proposed method therefore offers significant benefits in terms of cost savings and energy conservation.

[0129] The lower extraction rate requirements mean that the proposed method can be implemented in existing structures with some modifications. That is, it may not be necessary to acquire and install many high-powered smoke extraction fans and ducts. The proposed method therefore offers significant benefits in terms of cost savings and energy conservation. This further advantageously means that existing structures of historical and cultural importance can be better protected without having to destroy part of the existing structures merely to accommodate more smoke management equipment. Even more importantly, the safety of visitors and tourists at historical sites and sites of cultural heritage significance can be better assured by the provision of zones of perpetual tenability.

[0130] Compared to conventional methods, the proposed method results in a smaller area losing tenability. This could mean that a higher proportion of the historical or culturally important site can be preserved.

[0131] In one aspect, various embodiments of the present disclosure include a system operable by a controller configured to perform a method of smoke extraction from a built space. Initially, after fire ignition occurs, smoke may begin to spread within the fire zone. When smoke reaches and is detected by the smoke sensors in the fire zone, the smoke sensors may send a signal to an external controller. The controller is configured to then activate the ESC (Environmental Smoke Control) and open the smoke vents in the fire zone. Subsequently, when smoke spreads to a zone adjacent to the fire zone, smoke sensors in this adjacent zone will similarly send a signal (detection signal) to the controller, which will then open the smoke vents (extraction openings) in this adjacent zone. The same procedure may be repeated for the other adjacent zones as smoke continues to spread.

[0132] In another aspect, according to various embodiments of the present disclosure, there is provided a system of providing a region of perpetual tenability in a built space. The system includes a plurality of draft curtains, a plurality of smoke sensors, a controller, and a plurality of extraction openings. The plurality of draft curtains defines the built space as a plurality of zones. The plurality of smoke sensors being disposed in the plurality of zones and configured to enable a detection of a presence of smoke in any one of the plurality of zones. The controlleris configured to controllably operate the plurality of draft curtains and to receive a detection signal corresponding to the detection of the presence of smoke. The plurality of extraction openings may be disposed in the plurality of zones and configured to be activated by the controller to enable an extraction of smoke and / or air at a respective flow rate from any one of the plurality of zones. The controller is configured to activate the plurality of extraction openings sequentially zone-by- zone.

[0133] The system may be configured to be responsive to at least one of the plurality of extraction openings being activated and to provide a total flow rate of extraction from the built space for any number of the plurality of extraction openings being activated, in which the total flow rate is a constant.

[0134] The plurality of extraction openings may be configured to provide a total flow rate of extraction from the built space, in which the total flow rate is contributed equally by the respective flow rates from all of the plurality of zones with at least one activated extraction opening, and in which the total flow rate is a constant.

[0135] The plurality of smoke sensors may include one or more first smoke sensors disposed in a first zone of the plurality of zones, in which the plurality of extraction openings includes one or more first extraction openings in the first zone, the one or more first extraction openings being configured to be activated to enable a first flow rate from the first zone in response to the one or more first smoke sensors detecting the presence of smoke in the first zone.

[0136] The plurality of smoke sensors may include one or more second smoke sensors disposed in a second zone of the plurality of zones, in which the plurality of extraction openings includes one or more second extraction openings in the second zone. The one or more second extraction openings may be configured to be activated to enable a second flow rate from the second zone in response to the one or more second smoke sensors detect the presence of smoke in the second zone. The one or more second extraction openings may be configured to be activated subsequent to the one or more first extraction openings being activated.

[0137] The one or more first extraction openings may be configured to extract the smoke and / or air from the first zone at a first flow rate, in which the one or moresecond extraction openings are configured to extract the smoke and / or air from the second zone at a second flow rate. The first flow rate and the second flow rate may be configured to be equal to one another, with the total flow rate being unchanged by the one or more second extraction openings being activated.

[0138] The plurality of smoke sensors may include one or more third smoke sensors disposed in a third zone of the plurality of zones. The plurality of extraction openings may include one or more third extraction openings in the third zone. The one or more third extraction openings may be configured to be activated to enable a third flow rate from the third zone in response to the one or more third smoke sensors detect the presence of smoke in the third zone. The one or more third extraction openings may be configured to be activated subsequent to the one or more second extraction openings being activated.

[0139] The one or more third extraction openings may be configured to extract the smoke and / or air from the third zone at a third flow rate. The first flow rate, the second flow rate, and the third flow rate may be configured to be equal to one another, with the total flow rate being unchanged by the one or more third extraction openings being activated.

[0140] Each of the plurality of extraction openings in a default state is nonactivated.

[0141] Each of the plurality of zones is fluid communication with at least one other of the plurality of zones.

[0142] An edge of each of the plurality of draft curtains in a fully extended state is preferably spaced apart from a finished floor level of the built space by a safety height of 2.5 meters or more.

[0143] The system may be configured to have no more than three of the plurality of zones with lost tenability.

[0144] The system may be configured to enable perpetual tenability in all but three of the plurality of zones.

[0145] The system may be configured to enable perpetual tenability in all but two of the plurality of zones.

[0146] The system may be configured to enable perpetual tenability in all but one of the plurality of zones.

[0017] In the system, four of the plurality of draft curtains may be spaced apart to define the first zone, the second zone, and the third zone as three sequentially adjacent zones, with the first zone being defined between the second zone and the third zone.

[0148] The region of perpetual tenability may be defined outside the three sequentially adjacent zones.

[0149] All examples described herein, whether of apparatus, methods, materials, or products, are presented for the purpose of illustration and to aid understanding and are not intended to be limiting or exhaustive. Modifications may be made by one of ordinary skill in the art without departing from the scope of the claimed invention.

Claims

CLAIMS1. A system of providing a region of perpetual tenability in a built space, the system comprising: a plurality of draft curtains, the plurality of draft curtains defining the built space as a plurality of zones; a plurality of smoke sensors, the plurality of smoke sensors being disposed in the plurality of zones and configured to enable a detection of a presence of smoke in any one of the plurality of zones; a controller, the controller being configured to controllably operate the plurality of draft curtains and to receive a detection signal corresponding to the detection of the presence of smoke; and a plurality of extraction openings, wherein the plurality of extraction openings are disposed in the plurality of zones and configured to be activated by the controller to enable an extraction of smoke and / or air at a respective flow rate from any one of the plurality of zones, and wherein the controller is configured to activate the plurality of extraction openings sequentially zone-by-zone.

2. The system as recited in claim 1 , wherein responsive at least one of the plurality of extraction openings being activated, the system is configured to provide a total flow rate of extraction from the built space for any number of the plurality of extraction openings being activated, and wherein the total flow rate is a constant.

3. The system as recited in claim 1 , wherein the plurality of extraction openings is configured to provide a total flow rate of extraction from the built space, and wherein the total flow rate is contributed equally by the respective flow rates from all of the plurality of zones with at least one activated extraction opening, and wherein the total flow rate is a constant.

4. The system as recited in claim 2 or claim 3, wherein the plurality of smoke sensors comprises one or more first smoke sensors disposed in a first zone of the plurality of zones, and wherein the plurality of extraction openings comprises one or more first extraction openings in the first zone, the one or more first extraction openings being configured to be activated to enable a first flow rate from the first zone in response to the one or more first smoke sensors detecting the presence of smoke in the first zone.

5. The system as recited in claim 4, wherein the plurality of smoke sensors comprises one or more second smoke sensors disposed in a second zone of the plurality of zones, and wherein the plurality of extraction openings comprises one or more second extraction openings in the second zone, the one or more second extraction openings being configured to be activated to enable a second flow rate from the second zone in response to the one or more second smoke sensors detect the presence of smoke in the second zone, and wherein the one or more second extraction openings are configured to be activated subsequent to the one or more first extraction openings being activated.

6. The system as recited in claim 5, wherein the one or more first extraction openings are configured to extract the smoke and / or air from the first zone at a first flow rate, and wherein the one or more second extraction openings are configured to extract the smoke and / or air from the second zone at a second flow rate, the first flow rate and the second flow rate are configured to be equal to one another, with the total flow rate being unchanged by the one or more second extraction openings being activated.

7. The system as recited in claim 5 or claim 6, wherein the plurality of smoke sensors comprises one or more third smoke sensors disposed in a third zone of the plurality of zones, and wherein the plurality of extraction openings comprises one or more third extraction openings in the third zone, the one or more third extraction openings being configured to be activated to enable a third flow rate from the third zone in response to the one or more third smoke sensors detect the presence of smoke in the third zone, and wherein the one or more third extraction openings are configured to be activated subsequent to the one or more second extraction openings being activated.

8. The system as recited in claim 7, wherein the one or more third extraction openings are configured to extract the smoke and / or air from the third zone at a third flow rate, and wherein the first flow rate, the second flow rate, and the third flow rate are configured to be equal to one another, with the total flow rate being unchanged by the one or more third extraction openings being activated.

9. The system as recited in any one of claims 1 to 8, wherein each of the plurality of extraction openings in a default state is non-activated.

10. The system as recited in any one of claims 1 to 9, wherein each of the plurality of zones is fluid communication with at least one other of the plurality of zones.11 . The system as recited in any one of claims 1 to 10, wherein an edge of each of the plurality of draft curtains in a fully extended state is spaced apart from a finished floor level of the built space by a safety height of 2.5 meters or more.

12. The system as recited in any one of claims 1 to 11 further configured to have no more than three of the plurality of zones with lost tenability.

13. The system as recited in any one of claims 1 to 12, further configured to enable perpetual tenability in all but three of the plurality of zones.1 . The system as recited in any one of claims 1 to 12, further configured to enable perpetual tenability in all but two of the plurality of zones.

15. The system as recited in any one of claims 1 to 12, further configured to enable perpetual tenability in all but one of the plurality of zones.

16. The system as recited in claim 7 or claim 8, wherein four of the plurality of draft curtains are spaced apart to define the first zone, the second zone, and the third zone as three sequentially adjacent zones, and wherein the first zone is defined between the second zone and the third zone.

17. The system as recited in claim 16, wherein the region of perpetual tenability is defined outside the three sequentially adjacent zones.

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