Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Image-based sizing techniques for fire water droplets
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 ...
Image-based sizing techniques for fire water droplets
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 ...
Image-based sizing techniques for fire water droplets
Lundberg, Joachim (Autor:in)
12.11.2015
Hochschulschrift
Elektronische Ressource
Englisch
fire water spray , deluge , droplets , image processing , 553 , 581
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