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Accurate representation of fire sprinkler spray enables quantitative engineering analysis of fire suppression performance. Increasingly, fire sprinkler systems are evaluated using computer fire models in which sprinkler spray is simulated with Lagrangian particles. However, limited guidance exists as to how to predict the behavior of complex, spatio-stochastic fire sprinkler spray or how to accurately represent the dispersion of spray in terms of Lagrangian particles. The current work predicts the dispersion of the fire sprinkler spray generated by a canonical axisymmetric sprinkler using a Lagrangian particle tracking model within FireFOAM, an open source computational fluid dynamics fire model. In this work, the initial fire sprinkler spray is described with a new spray injection model characterized by a multivariate probability distribution function related to spatially resolved breakup radius, volume flux, drop size, and drop velocity. This function is stochastically sampled to generate Lagrangian particles representative of the near-field spray and the dispersion of these Lagrangian particles is in turn simulated in FireFOAM to predict the far-field spray. Our new model is compared to a baseline FireFOAM spray injection model which incorporated fewer spray details. Modeled results are compared to highly resolved far-field measurements of axisymmetric sprinkler sprays generated by the Spatially-Resolved Spray Scanning System (4S).

Automatic fire sprinklers use a heat sensitive element such as a glass bulb or fusible link to respond to the heat from a fire. The response of commercial fire sprinkler glass bulbs has been extensively characterised in convection-dominated dry gas flows but in real fires there may be more factors that influence the heat transfer to the bulbs such as radiation from the fire or cooling from adjacent sprinkler sprays. The time of activation is the only indication of the thermal response of typical commercial fire sprinklers using glass bulbs to a fire, but direct temperature measurement using a modified proxy may provide a better understanding of how sprinklers respond in a complex environment. Modified glass bulbs have been created that allow a thermocouple to be inserted in the bulb for direct temperature measurement. In this paper, the thermal response of sprinklers with these modified bulbs has been observed in hot-air wind tunnel plunge experiments and full scale room fire experiments. At the time of activation the measured temperature of the modified sprinklers was found to be higher than the nominal activation temperature specification for the unmodified sprinklers. For the compartment fires, a thermal response model generally predicted longer sprinkler activation times based on ceiling jet temperature and velocity measurements than was observed experimentally.

Fire sprinkler manufacturers have developed a great variety of application specific sprinkler designs. Advances in product development practices, performance based design, risk analysis, and fire suppression research have increased stakeholder interest in quantifying the spray produced by these devices. These sprinkler spray patterns consist of complex spatio-stochastic features originating near the sprinkler head. A Spatially-resolved Spray Scanning System (4S) has been developed to capture the complete spatio-stochastic nature of the spray at its point of origin for documentation and analysis. The 4S synthesizes spray measurements, transport analysis, and statistical representation frameworks providing high-fidelity spray characteristics suitable for evaluation of component-level performance (e.g. sprinkler spray pattern uniformity) or system-level performance (e.g. fire suppression system simulations). Each sprinkler's unique spray pattern is captured through optical and mechanical probing of the spray over a measurement (or initialization) surface close to the sprinkler head (0.4−0.8 m) and analyzing local drop characteristics (e.g. drop size, velocity, and volume flux). These high-fidelity 4S spray measurements consisting of terabyte scale data densities present remarkable challenges with regard to data management, test repeatability, and test timing. These challenges are addressed through integration of automation, flow control, data acquisition, and data analysis systems. Spatially-resolved sprinkler spray measurements are presented providing insight into the sprinkler spray patterns and their connection with deflector geometry. Comparisons between far-field spray dispersion measurements and simulations initialized with 4S measurements demonstrate unprecedented agreement further highlighting the value of spatially-resolved sprinkler measurements for modern suppression analysis.

A Reduced Order Model (ROM) providing a highly detailed description of the sprinkler spray has been developed for engineering applications. The new ROM approach combines an elegantly parameterized analytical description of the dispersed spray with a tightly integrated high-fidelity description of the initial spray capable of producing a complete quantitative map of the entire sprinkler spray field from centerline to edge and ceiling to floor. The complex spray field is mapped using a sparsely sampled phase-space accounting for all drops produced by the sprinkler. The spray is mapped through fast two-dimensional trajectory calculations spanning this discretized phase-space to produce quantitative views of the spray in regions of interest or in its entirety. Spray patterns are easily extracted from this spray field according to attributes of interest. The ROM is demonstrated by comparing predicted and measured spray patterns generated below a commercial sprinkler. These spray patterns are quantified through spatial distributions of volume flux showing good agreement between measurements and ROM predictions (average error of 0.44 mm/min or 5% of peak volume flux). The speed and robustness of the ROM provide an unprecedented quantitative view of fire sprinkler spraying performance with sufficient accuracy for potential use in engineering design applications.

Accurate representation of the fire sprinkler spray enables quantitative engineering analysis of fire suppression performance. Increasingly, fire sprinkler systems are analyzed with computational fluid dynamics (CFD) fire models where the sprinkler spray is simulated with Lagrangian particles dispersed throughout the fire induced flow. However, there is limited guidance for representing the complex, spatio-stochastic characteristics of the initial sprinkler sprays in terms of these Lagrangian particles. The present work establishes a descriptive analytical framework for the initial sprinkler spray that is rigorously grounded in statistical theory, related to local spray properties, and capable of translating high-fidelity measurements into CFD inputs. This framework describes the initial sprinkler spray as a unified probability distribution function, varying over an initialization surface, and statistically representing measurements of near field local spray properties (volume flux, drop size distribution, and drop size–velocity correlation). Lagrangian particles accurately representing the sprinkler spray may be initialized by a stochastic sampling of this probability distribution function. This novel representation enables high-fidelity initialization of the sprinkler spray in CFD fire models, improving their utility in quantitative engineering analysis.

Modelling the atomization process in fire sprinklers has remained a challenge mainly due to the complexity of sprinkler geometry. A review of existing fire sprinkler spray modelling approaches, including film flow and sheet tracking models, showed that they mainly assumed a constant sheet velocity and linear attenuation of the sheet thickness before its disintegration. In the present study, a liquid sheet trajectory sub-model based on the solution of stream-wise conservation equations has been used to predict both sheet thickness and velocity as it radially expands. This will also help to investigate the extent to which a change in the release angle can affect the sheet characteristics. The analysis carried out shows that the proposed approach improves the predictions of mean droplet diameter and initial droplet speed. A semi-empirical approach is further introduced in the study by using experimental volume fraction measurements to characterize sprinkler sprays in the near field. For a given direction predictions have been conducted for droplet volume median diameter, water volume flux and droplet average velocity at different elevation and azimuthal locations. A reasonably good agreement is found for the near field measurements.

An experimental study is conducted to evaluate the performance of automatic water cannon systems for protecting fire hazards in large-open spaces. As part of this study, typical fire hazards encountered in large-open spaces are simulated to allow for a comparison of water cannon and automatic fire sprinkler protection. Tests are performed to characterize response time, water distribution and effectiveness of protection of the selected water cannon system. Results show that, in general, water cannon can respond to fire events in large-open spaces much faster than sprinklers. Under certain conditions, water cannon can also control and/or suppress the fire. However, further improvement of automatic water cannon technology is needed to optimize system performance for various commodity fires that may occur in large-open spaces.

Measurements were conducted to characterize the spray patterns of an upright fire sprinkler in the near and far field of the sprinkler. The spatial distribution of droplet size, velocity and number density in the spray was measured using a laser-based shadow-imaging system. The water volume flux distribution was measured by an array of pressure-transducer-equipped water collection tubes and containers. A large-scale traverse was constructed to move the laser optics and water collection tubes and containers to the designated measurement locations. An upright fire sprinkler with a K-factor of 162 lpm/bar1/2, installed with its deflector 0.17 m below a flat horizontal ceiling, was characterized at two discharge pressures, i.e., 0.76 bar and 1.31 bar. In the near field at 0.76 m from the sprinkler, measurements were performed in a spherical coordinate at different azimuthal and elevation angles with respect to the sprinkler deflector. In the far field, the sprays were mapped out in a 110° circular sector at 3.05 m and 4.57 m below the ceiling. The shadow-imaging based water flux measurements were verified by the measurements obtained from water collection containers. Except for the pipe effect, the azimuthal distributions of the flow rate showed that the spray pattern was more influenced by the frame arms than by the deflector tines and slots. The gross droplet size distribution was expressed as a combination of a log-normal function and Rosin–Rammler function. The median droplet diameter was correlated as an empirical function of the sprinkler orifice diameter and operating pressure. The near-field distributions of the droplet size, velocity and flux can be used to prescribe the starting spray conditions for numerical simulations of spray transport. The far-field measurements are useful in evaluating the spray transport calculations.

The spray patterns of a pendent fire sprinkler were characterized through experimental measurements in the near and far field of the sprinkler. A laser-based shadow-imaging system was used to measure the droplet size, velocity and number density in the spray. An array of pressure-transducer-equipped water collection tubes and containers provided a separate set of water volume flux measurements. A large-scale traverse was constructed to move the laser optics and water collection tubes and containers to the designated measurement locations. A pendent fire sprinkler with K-factor of 205 lpm/bar1/2 (14.2 gpm/psi1/2) was characterized at two discharge pressures 3.5 bar and 5.2 bar (50 and 75 psi). In the near field at 0.76 m from the sprinkler, measurements were performed in a spherical coordinate at different azimuthal and elevation angles with respect to the sprinkler deflector. In the far field, the sprays were mapped out in a 110° circular sector at 3.05 m and 4.57 m below the ceiling. The shadow-imaging based water flux measurements were verified by the measurements obtained from water collection containers. The measurements show that the spatial distributions of water volume flux, droplet size and velocity of sprinkler sprays are strongly influenced by the sprinkler frame arms and the configuration of sprinkler deflector’s tines and slots. For the purpose of fire protection analysis, empirical correlations were developed from the near-field measurements to prescribe the spray starting conditions for the numerical modeling of spray transport through fire plumes. The far-field measurements can be used to evaluate the spray transport calculations.

The current state of fire sprinkler effectiveness information has been found to be a limiting factor when comparing the fire risk for alternative building designs in New Zealand (Determination 2005/109: single means of escape from a high-rise apartment building. Department of Building and Housing, Wellington, 7). Data on the past performance of systems in real fires is one of the best sources of information to estimate future performance, but there has not been a detailed study on sprinkler effectiveness data from fire incidents in New Zealand published since Marryatt’s work (Fire: a century of automatic sprinkler protection-revised. Australian Fire Protection Association, Melbourne, 13), which was last updated in 1986 and included data from Australia. The current research looks at the quality and quantity of data available on sprinkler effectiveness from New Zealand Fire Service (NZFS) incident reports over the period of 2001 to 2010 to evaluate the data’s usefulness for risk-informed building fire safety design. A comparison is made between the number of sprinklers reported activated in the NZFS dataset, Marryatt’s study, guidance from PD 7974-7:2003 (PD 7974-7:2003: the application of fire safety engineering principles to fire safety design of buildings. Probabilistic Risk Assessment, London, 3), and NFPA data (U.S. experience with sprinklers and other automatic fire extinguishing equipment. National Fire Protection Association, Quincy, 12). Proposals to improve the collection and reporting process to increase the informative value of future NZFS data for risk-informed fire safety design are presented.

A preliminary study at low water discharge pressures was conducted to investigate the fire sprinkler spray formation as affected by sprinkler geometry using a laser-based shadow imaging system. A sprinkler typically consists of the following components: a deflector with tines and slots, a boss above the deflector and sprinkler frame arms. Prototypes of these components were fabricated to evaluate their effects on the spray formation process. The water sheet thickness formed on non-slotted deflectors, slot spray discharge angle, sheet breakup distance from the deflector perimeter, water flux and drop size distributions were measured. It was found that deflector diameter and boss structure have little impact on drop size and sheet breakup distance. However, wider slots form larger drops. At constant operating pressure, the slot spray discharge angle is insensitive to the slot width, but sensitive to the boss that helps directing the slot spray toward the sprinkler centerline. The frame arm tends to produce a vertical spray sheet downstream of the frame arm, which increases the complexity of overall spray formation. An integral model was developed to calculate the development of water sheet thickness and speed on the deflector for different degrees of viscous effect exerted by the deflector. An empirical correlation was also established to estimate the spray flux fraction discharging from a deflector slot. The above measurements and observations are useful for the development of a spray formation model for fire sprinklers.

A recent study on the environmental impact of automatic fire sprinklers is documented in a two part series. The present paper examines the relationship of automatic fire sprinkler technology to environmental sustainability. Large-scale fire tests were conducted using identically constructed and furnished living rooms. In one test, fire extinguishment was achieved solely by fire service intervention, and in the other, a single residential automatic fire sprinkler was used to control the fire until final extinguishment was achieved by the fire service. Comparisons of the total greenhouse gas production, quantity of water required to extinguish the fire, quality of water runoff, potential impact of wastewater runoff on groundwater and surface water, and mass of materials requiring disposal between the two tests were made. The results show that in addition to providing life safety and limiting property damage, the use of automatic fire sprinklers is a key factor in achieving sustainability.

Sprinkler heads are a mature product that can fail to function via a variety of different mechanisms. Mechanical damage and corrosion can occur year round. Additionally, there can be seasonal failures due to creep of fusible alloys in summer. Serious problems also have occurred due to sticking of sliding O-ring seals. These problems have lead to product recalls, and subsequent revisions in design standards.

Performance based methodologies are becoming increasingly common in fire safety due to the inability of prescriptive codes to account for every architectural feature. Fire Sprinkler suppression systems have long been used to provide property protection and enhance life safety. However, very few methodologies exist to account for the impact of sprinkler sprays on fire scenarios. Current methods are extremely complicated and difficult to use as an engineering tool for performance based design. Twenty-four full scale fire tests were conducted at Tyco Fire Suppression & Building Products Global Technology Center to determine a simple method for accounting for the impact of a single residential sprinkler on fire induced doorway flows. It was found that a spraying sprinkler reduced the mass flows at the doorway while maintaining two stratified layers away from the sprinkler spray. The mass flow reduction was consistent and could be predicted through the use of a simple buoyancy based equation. The current study suggests that the buoyancy equation can be altered through the use of a constant cooling coefficient (equal to 0.84 for a Tyco LFII (TY2234) sprinkler) based on the test results reported in this paper. This study is a proof of concept and the results suggest the methodology can be applicable to similar situations.

A benefit–cost analysis is performed to measure the expected present value net benefits (PVNB) resulting from the installation of a residential fire sprinkler system in a newly constructed, single-family house. The benefits and costs associated with installation and use of a fire sprinkler system are compared across three prototypical single-family house types: colonial, townhouse, and ranch. Each of the house types varies by design, size, and fire sprinkler affordability. Six fire sprinkler system designs are evaluated: a multipurpose network system, three stand-alone systems, and two stand-alone systems equipped with a backflow preventer. The sprinkler designs vary by installation cost (materials and labor cost) and required annual maintenance, but all were designed to meet the NFPA 13D standard. The estimated benefits of fire sprinklers include reductions in the following: the risk of civilian fatalities and injuries, homeowner insurance premiums, uninsured direct property losses, and uninsured indirect costs. Results show that residential sprinkler systems not requiring expensive annual upkeep or maintenance are economical. The expected PVNB in 2005 dollars is estimated as $2,967 for the colonial-style house, $3,099 for the townhouse, and $4,166 for the ranch-style house, given installation of the lowest life-cycle cost sprinkler system in each of the house types. A sensitivity analysis that measures the variability of the results to changes in the modeling assumptions confirms the robustness of the baseline analysis.

A comprehensive analytical model is developed for a pressurized fire sprinkler piping system of a hospital building. A suite of ninety-six artificial triaxial floor acceleration histories is used to generate seismic fragility parameters of the sprinkler piping system. The analytical model accounts for the inelastic behavior of braces, hangers, and wire restrainers. It incorporates an experimentally validated hysteresis model developed, as part of this study, for the moment-rotation relationship of grooved fitted joints. Component fragility parameters were obtained for lateral restrainers, hangers, and pipe joints. Three system-level damage states were defined based on the level of functionality of fire sprinkler systems and severity of leakage after a seismic event and a joint probabilistic model were utilized to obtain system-level fragility parameters. Finally, the seismic fragility of fire sprinkler systems with grooved fit joints is compared to that of a piping system with threaded joints.

The reaction of a fire plume to an applied water spray is crucial to fire suppression. While considerable research has been devoted toward fire plumes without suppression, and some computer simulations of fire suppression have provided insight, little experimental data exist detailing how the structure of a fire plume changes during suppression. Experiments were performed in which 5, 15 and 50 kW gas burner fires were exposed to a spray from one of three spray sources. Flow rates from the nozzles or fire sprinkler ranged from 6 to 106 L/min. Contours of infrared (IR) intensity of the fire plume show that the plume decreases in height and increases in width with the increasing strength of the applied spray. Based on the height of the maximum fluctuations of IR intensity, the thermal plume height decreases with increasing spray strength, but the overall projected area of the plume changes very little. The plume height depends on the ratio of the drag of the droplets on the air to the momentum of the plume, allowing the results to be generalized to typical fire suppression applications.

Equations describing the fluid motion in buoyant plumes have been applied to fire plumes by researchers and engineers since Morton et al. developed them in the 1950s. However, in the application of active fire suppression by water droplets, the equations are no longer valid. The equations have been modified to include the effect of a homogeneous, uniform velocity droplet field on the momentum of the fluid. Solving the resulting ordinary differential equations shows that the plume widens and the upward velocity of the plume slows significantly due to the presence of droplets. Results from this simple model appear to match the results of more sophisticated numerical simulations. The model further demonstrates that the interaction between the upward momentum of the plume and the downward momentum of the droplet spray can be critical for fire suppression.

This article is a guide for sprinkler contractors, facilities managers, and their technical advisors who sometimes have to deal with the consequences of iron-water corrosion inside pressurized, low-carbon steel fire protection systems that contain water. The consequences include: (1) pinhole leaks and (2) build-up of insoluble corrosion residues on the interior pipe wall that increases pipe friction losses. A reference is made to sections of the National Fire Codes/NFPA 13 that address pipe materials, protection of steel piping against corrosion, and pipe friction losses. Electrochemical metal-water corrosion processes that can occur inside pressurized, low-carbon steel fire protection systems that contain water are discussed, as is microbiologically influenced corrosion. Corrosion control measures arising from the electrochemical science underlying both metal-water corrosion and microbiologically influenced corrosion are suggested.

The results of phase Doppler interferometry (PDI) and particle image velocimetry (PIV) measurements to characterize the water sprays produced by fire sprinklers are presented. The large size of the water drops produced by fire sprinklers, and the relatively large coverage area of the spray, present significant challenges when attempting to characterize these sprays. These difficulties are especially relevant when using PDI because large drops and large coverage areas may result in attenuation of the transmitting laser beams. For the fire sprinkler investigated, it was determined that attenuation of the laser beam resulted in over-counting of drops due to burst splitting, a situation in which the Doppler signals from single drops are misinterpreted as being due to multiple drops. This effect was minimized by carefully choosing the operating conditions of the PDI processing electronics. PIV measurements provide velocity profiles that can be used as input for fire dynamics simulations to predict the effect of sprinkler sprays on fires. The results from the PIV measurements show good agreement with the velocity measurements obtained from PDI in the core of the spray, but poorer agreement along the sprinkler axis. The discrepancy was attributed to recirculation zones present in the experimental facility and possible biasing of the PIV measurements towards the larger drops.

A full-scale test program 1 was conducted at the Factory Mutual Research Corporation test facility to determine if existing or new technology fire sprinkler systems are capable of providing acceptable protection for high-piled storage found in warehouses and warehouse-type retail stores. Nine large-scale fire tests were conducted with double-row rack storage arrangements containing a cartoned Group A Unexpanded Plastic commodity. Protection was provided by Extra Large Orifice, 0.64 in. (16 mm), sprinklers installed at the ceiling only. Test variables included: building heights of 22 to 27 ft (6.7 to 8.2 m); storage heights of 14 to 20 ft (4.2 to 6.1 m), in conjunction with ignition location; sprinkler temperature rating; sprinkler discharge density; type of shelving (slatted wood, solid wood or wire mesh); flue spacing; and the presence of draft curtains. Test results show that a 0.60 gpm/ft2 (24 mm/min) discharge density supplied over a 2000 ft2 (186 m2) design area will protect such storage; and reduced...

This paper considers the extension of fire field modelling to include fire-sprinkler interac tion. Both Lagrangian and Eulerian techniques used to model a second particulate phase are briefly outlined. The latter modelling approach is extended to develop a model to simu late fire-sprinkler interaction. Two initial scenarios are briefly highlighted. Computer hard ware requirements for this technique are also discussed. It is suggested that parallel com puting techniques offer an affordable and viable means of meeting these needs.

This report is reprinted in part from Sprinkler Quarterly, Vol. 77, with permission of the National Fire Sprinkler Association, Inc.

The discharge flow pattern from fire sprinkler heads in modeled in a nondimensional description which emphasizes a sprinkler's ability to evenly distribute spray over a maximum possible floor area. An axisymmetric model sprinkler, consisting of a jet impinging normal to and at the center of a flat disk, employs the disintegration of the resulting film to produce the droplet sprays. Measurements of the sheet breakup radius show that it is proportional to the negative one-third power of the Weber number based on jet diameter. The discharge distribution is varied by controlled axial vibrations of the disk. Nondimensional sheet breakup radii and radial flow distributions correlate with the ratio of the disk driving frequency to the frequency of maximum growth of sinuous waves. Flow patterns from the model apparatus are compared with those from a commercial fire sprinkler. An analytical model to predict droplet trajectories and consequent discharge distributions shows qualitative agreement with the measured flow patterns for an assumed Rosin-Rammler droplet size distribution about a volume mean droplet diameter in the accepted range of previous investigators.