Investigation Of Spray Patterns Of Selected Sprinklers With The Fmrc Drop Size Measuring System

Yu, Hong

doi:10.3801/iafss.fss.1-1165

Cited by 50 publications

(45 citation statements)

References 2 publications

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“…However a space generated stream orthogonal to the tine generated sheet was also observed through flow visualization and measured to constitute nearly 50% of the overall flow. These two streams followed We -1/3 sheet breakup and drop size scaling laws determined from previous impinging jet [18] and sprinkler [5,6,[8][9][10] studies, respectively. Measurements also revealed that the drop sizes created from the space stream are much smaller than those created from the tine generated sheet.…”

Section: Discussionmentioning

confidence: 99%

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Quantifying the Initial Spray from Fire Sprinklers

Ren¹,

Blum²,

Zheng³

et al. 2008

Fire Saf. Sci.

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The performance of water-based fire suppression systems is governed largely by the spray discharge characteristics associated with the nozzle geometry and injection conditions. In many nozzle configurations such as sprinklers, this initial spray is produced by injecting a water jet onto an orthogonal deflector, resulting in thin, unstable, radially expanding streams. These streams ultimately disintegrate into a complex population of drops forming the spray. The initial spray is generated in distinct stages, which include sheet formation, sheet breakup, and ligament breakup. A Sprinkler Atomization Model (SAM) has been developed based on these physics to predict the initial drop velocity, location, and size based on the nozzle geometry and injection conditions. The initial spray from a simplified yet realistic sprinkler geometry has been quantified through detailed measurements to provide insight into these atomization processes and to evaluate SAM performance. Flow visualization revealed that the deflector produces a continuous radially expanding stream resulting from the flow directed over the tines and a connected underlying orthogonal stream resulting from the flow through the spaces. The measured and predicted breakup locations and drop sizes follow We -1/3 scaling laws, previously established by other researchers in similar canonical configurations. However, SAM over predicts the volume median drop diameter by as much as 40%, probably due to the absence of models to characterize the orthogonal stream underlying the radially expanding sheet. This orthogonal stream generated by the spaces was measured to consist of nearly 50% of the flow and produces smaller drops than the radially expanding sheet. The detailed breakup mechanisms for this stream are currently being characterized to improve fidelity of the atomization model. INTRODUCTIONAutomatic fire sprinklers are accepted as the fire protection system of choice for a wide variety of applications. To support the development of many types of fire protection systems and the design of fire safe environments, modern engineering practices are currently being established like performance-based design, which requires the prediction of fire behavior using physics-based analytical methods and tools. Despite the simplicity of the basic operating principles for fire sprinklers, the complex physics governing water-based suppression including multi-phase transport processes, flame sheet extinction, and extinction of condensed phase reactions, present profound analytical and modeling challenges. Even the physical mechanisms controlling the sprinkler's simple action to generate a dispersed spray are quite complex and do not yield readily to analysis. Yet, as advanced fire protection engineering practices continue to gain popularity, the need to model fire sprinklers for suppression system and even component analysis is inevitable. In this study, the challenge to characterize the initial spray from sprinklers is addressed to advance understanding of the atomization...

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Section: Discussionmentioning

confidence: 99%

“…Detailed sprinkler spray measurements have been reported by Dundas [5] , Yu [6] and Wendt and Prahl [7]. More recent studies have been conducted by Widmann et al [8,9], Sheppard [10] and Putorti [11].…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Initial Spray from Fire Sprinklers

Ren¹,

Blum²,

Zheng³

et al. 2008

Fire Saf. Sci.

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“…This method had a problem with the largest droplets scattering and the smallest droplets agglomerating. Still-photography was also used to analyze the spray, but this was highly time consuming and not accurate (Yu, 1986). Knollenberg (1970) published an article on an electro-optical technique for measuring size distributions of droplets in clouds and precipitate particles.…”

Section: Early Studies Of Droplet Distributionsmentioning

confidence: 99%

“…Droplet sizes in sprays from sprinklers and deluge nozzles have been measured by several papers (Yu 1986;Jackman 1992;Sheppard 2002). The droplet sizes are important to know when calculating the suppression efficiency of fire water spray.…”

Section: Related Previous Researchmentioning

confidence: 99%

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Image-Based Characterization of a Medium Velocity Fire Water Nozzle – Preliminary Results

Lundberg¹,

Lysaker²,

Vaagsaether³

et al. 2013

Proceedings of the Seventh International Seminar Fire and Explosion Hazards

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The Norwegian petroleum industry has developed a standard for the technical safety of offshore installations (NORSOK S-001, 2008). When dimensioning accidental load with this standard, the deluge or fire water spray may be considered as a risk reducing measure for equipment and pipes, but not for the structural elements or fire partition (NORSOK S-001, 2008). Proper documentation of the suppression effect and reliability has to be provided when water is used as a fire risk reduction measure in risk evaluation. The standard states that the deluge system shall be automatically activated upon confirmed gas detection when used for explosion mitigation.Full-scale fire experiments with fire on offshore platforms are limited by practical and economic considerations. Instead, numerical simulations are used for risk analyses. To get a good representation of the effect of the fire water deluge system, the properties of the water spray need to be known.In the literature, the availability of data on fire water spray is limited. Often the spray is described only by the orifice diameter of the fire water nozzles and spray angle. However, the flow properties of the spray (i.e., size and velocity distribution of the droplets) are known to influence the suppression efficiency. Small droplets will follow the convective forces in the gas flow, evaporate quickly, cool the fire gases and screen for heat radiation. In contrast, large droplets have high momentum and are more likely to reach the source of the fire and to cool objects such as process equipment and pipes.Presently the most used technique for measuring droplet size and velocity in fire water spray is the Phase Doppler Anemometry (PDA). This technique will provide online measurements of both size and velocity at the same time, but the technique has some limitations and practical problems.In this doctoral thesis, a laser-based shadow-imaging technique by a high-speed camera and a laser is used. To analyze the shadow-images, an in-house image-processing tool in Matlab has been developed to find droplet size-and velocity distribution.The results from the experiments in this thesis show the location in the spray to have a large effect on the water flux( 3 ( 2 • ) ⁄ ), i.e. the water flux is not uniform and varies with water supply pressure. The geometry of the nozzle and the frame arms affects the applied water flux extensively at low pressures. This effect is taken into account when the applied water flux is measured. 4The results show the water pressure to have the following effects:  The radial coverage will decrease with increasing water supply pressure  The applied water flux will be less uniform for different azimuthal angles at low water pressures than at high water pressures. The number of large droplets will decrease with increasing pressure  The velocity of the droplets will in general increase with increasing pressure.The research provides unique experimental data of droplet size-and velocity distribution for the fire water nozzle and an image processing ...

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Simplified Calculation Method for Determining Smoke Downdrag Due to a Sprinkler Spray

Spearpoint

2010

Fire Technol

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A simplified method has been developed to predict smoke behavior subject to a sprinkler spray. The method considers whether downdrag is likely to occur and the distance that smoke is then pulled down should downdrag be present. The method is validated using third party experimental data. Empirical equations are applied in the calculations to determine the heat loss from a smoke layer due to the sprinkler spray and therefore the smoke layer temperature. Comparative results show that the simplified method might expect the onset of smoke downdrag regardless the difference in temperature predictions. The empirical equation to predict the penetration depth of downdrag smoke is based on previous research and compared with third party experimental data. The predicted depths are acceptable for engineering use. For a 15 mm nominal sprinkler the water flow rate that leads to the onset of downdrag for typical smoke layers up to 2 m in depth is less than 100 L/min which leads to an operating pressure being less than 0.16 MPa. Experimentally data for sprinklers other than the 15 mm nominal sprinklers are unavailable and therefore the method should be used with care for any other sprinkler.

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Investigation Of Spray Patterns Of Selected Sprinklers With The Fmrc Drop Size Measuring System

Cited by 50 publications

References 2 publications

Quantifying the Initial Spray from Fire Sprinklers

Quantifying the Initial Spray from Fire Sprinklers

Image-Based Characterization of a Medium Velocity Fire Water Nozzle – Preliminary Results

Simplified Calculation Method for Determining Smoke Downdrag Due to a Sprinkler Spray

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