Abstract
Aim: The aim of this work is to determine the ratio of the unit weight of dry chemical extinguishing powder depending on the distance from the nozzle of the DCES for the defined pneumatic and loading characteristics of the system, disperse parameters of dry chemical powder and the fire power.
Introduction: Currently, the pulse-type dry chemical extinguishing system (DCES) is extensively used for extinguishing fires. These units generally consist of a control junction and powder extinguishing modules (PEM) filled with fire extinguishing powder and gas pumped into the module under the high pressure. Giving extinguishing powder from the PEM in the fire source is carried out when exposed to the heated air of the thermal column generating lift. The magnitude of this force depends on the power of fire and intensity of air change in the room. The efficiency of fire extinguishing with the DCES in these conditions will be determined not only by the powder extinguishing ability but also its dynamic characteristics when approaching the fire. In the design of pulse-type fire extinguishing systems using PEMs it should be considered that during testing PEMs the dynamics of the gas powder mixture released from the module is impacted by the air resistance and the lift of the heated gases from the thermal column from the fire source.
Project and methods: To reach the aim of the study, a mathematical model approach was applied for the flow process the extinguishing substance from the DCES and its movement in open-air space towards the fire.
Results: A mathematical model was developed to calculate the movement dynamics of the gas-powder mixture in an open-air space towards the fire source under specific performance parameters of the DCES and the power of the fire. A correlation for estimating the extinguishing powder particle velocity at different distances from the DCES nozzle during their movement towards the fire of a given power was obtained. An experimental study of the dynamics of the front of the powder mixture ejected from the pulse-type PEM was performed. The analysis of the results showed their satisfactory level of compliance with numerical calculations.
Conclusions: The obtained results can be used for analyses of pulse-type PEMs with a goal of assessing the spatial and energy parameters of fires which can be extinguished using this method. The results can be used during the design of such installations in order to specify the pneumatic and load parameters of the module associated with the given technical characteristics of the extinguishing agent, the assumed power level of the fire source and the height of the PEM.
Keywords: dry chemical extinguishing system, dry chemical powder, velocity of the dry chemical powder, power of the fire source, heat wave
Type of article: original scientific article