Experimental Investigation on the Optimal Frequency for Acoustic Fire Extinguishing in Different Duct Configurations

Fire is essential to humanity in all aspects, but it also poses a risk, especially in duct systems, Fire can spread throughout the building through the duct space, causing the entire building to go up in flames at the same moment. Most current fire extinguishers do not fit well in duct spaces limited areas and numerous obstructions. To counter this problem, an innovative method of fire suppression is needed, such as acoustic fire extinguishing. Therefore, this research aims to investigate the interaction between the acoustic wave and the fire in different duct configurations. The MEP (minimum extinguish power) and Sound Pressure Level (SPL) along with airflow characteristics for fire extinguishing were studied when the channel configurations were changed. The experiment results show The Straight duct uses the highest power for extinguishing. It is followed by the Elbow and Zigzag configurations, which require similar power for extinguishing due to turbulent airflow characteristics and sound pressure levels (SPL). It can be observed that the Straight configuration is not complex, resulting in lower turbulence on the flame. This leads to more difficulty in extinguishing of fire and requires the highest power. This contrasts with the Elbow and Zigzag configurations, which have multiple joints, causing higher turbulence on the flame. In the conducted experiments, it was discovered that the Straight duct is effective in extinguishing until a frequency of 57.2 Hz, beyond which it cannot achieve further extinguishing. Similarly, the Elbow and Zigzag duct configurations reach their extinguishing limits at 65 Hz and 75 Hz, respectively. Moreover, the Sound Pressure Level (SPL) is a contributing factor in the extinguishing process. When measuring the SPL of all three configurations, it was uniformly observed that the Straight configuration reliably demonstrates the lowest SPL values in all instances which require higher power for extinguishing. Additionally, In every duct configuration, the air velocity (AV) required to extinguish the fire was in the range of 0.30 to 0.50 m/s. This enables us to predict the necessary power adjustments required to achieve the desired velocity for extinguishing at frequencies that were not subject to experimentation.