Study of Sound Wave as a Flame Extinguisher

The current fire extinguishing comes with various drawbacks. The need for new fire extinguishing techniques is vital as fire accidents cause deaths and injuries. Sound wave could be one of the potential alternative in putting off flames. The acoustic pressure and air velocity produced from a speaker is the main theory used to explain how sound waves put off flames. This research aims study and analyze the effect of different frequency of sound wave on flames. A simulation of sound wave was carried out to study behavior acoustic wave propagation in the collimator and surrounding environment. Experiments were then conducted to study suitable sound wave frequency range to extinguish flame and to analyze the acoustic-flame interaction through observations from camera. Three different sources of flames were used to with three different state of fuel (solid, liquid and gas). From the first part of results, using an ordinary collimator, it was found that sound wave can only extinguish gas fuel type flames at 91 Hz. However, in the second part of the experiment, the sound wave manage to extinguish all flames of different fuel types, with the converged collimator design. This mainly is due to the converged collimator gives a higher air velocity output as compared to an ordinary collimator design, which was verified through simulation result. The combination of varying high and low pressure and coupled with high flow air velocity, which in then causes disturbances in air-fuel ratio at the flame boundary (leading to thinning of flame boundary), is one of the possible explanation leading to flame extinction. In both experiment, the frequency range needed suppress the flames was found to be, between 90 to 94 Hz. However, in both experiments the flame boundary used was relatively small as compared real fire accidents due to safety consideration. Nevertheless, this sound wave based fire suppression technology could be used to combat early stages of fire accidents