Seiji Okinaga

Experimental Study on Fire Behavior in a Compartment Under Mechanical Ventilated Conditions: The Effects of Air Inlet Position

The purpose of this research is to understand the fire behavior expected in a mechanically ventilated compartment. To date, some experimental studies have been conducted for investigation of fire behavior under mechanical forced ventilation; however, it might be not enough to understand everything. We therefore carried out a series of experiments on fire behavior focused on the effect of air inlet position in a compartment with same size as an ISO 9705 room (width 2.4 m × length 3.6 m × height 2.4 m) under conditions of mechanical ventilation using a pool fire. In this paper, the effects of ventilation conditions such as air inlet position and flow rate were studied. We found that differences in the air inlet position and flow rate were one of the principal factors for determining the burning behavior.

Active imaging with incoherent sub-terahertz radiation from a photomixer array in a severe smoke

The imaging capability of active imaging with incoherent sub-terahertz (THz) radiation from a photomixer array in a smoky environment was investigated. The photomixer array consisted of nine uni-traveling-carrier photodiode modules, each with an integrated antenna. Incoherent sub-THz waves were generated by a photomixing scheme employing single-mode laser light and optical noise. Imaging tests on a target at a distance of 1.4 m showed that imaging with incoherent sub-THz illumination provides a clear view in heavy smoke for which the visibility was 0.22 m for visible light and 0.44 m for near-infrared light. These results indicate that active imaging with incoherent sub-THz radiation is an effective way to see through smoke.

Interaction of a Pool Fire in a Compartment with Negative Pressure Generated by Mechanical Ventilation

We have experimentally investigated a medium-size pool fire in a compartment, the dimensions of which corresponded to the ISO 9705 room. Airflow rates in ducts, pressure, mole fraction, and temperature of air in the compartment and a mass loss rate of the fuel were measured. The liquid fuel and pool diameter were ethanol and 600 mm, respectively, which rapidly increased the compartment pressure just after ignition. The compartment was ventilated at inlet and outlet ducts with natural and mechanical ventilation systems, which initially gave negative compartment pressures in the range of −2 to −85 Pa. The negative pressure was much weaker than the pressure increase, which restrained the air supply with natural ventilation and resulted in extinction due to lack of oxygen. On the other hand, the negative pressure with the stronger mechanical ventilation sustained the air supply and yielded the transition to a ventilation-controlled fire without extinction. The ventilation-controlled fire led to two kinds of oscillating flame: one was caused by poor oxygen supply, which is similar to that reported by previous studies, and the other was caused by repetition of ignition and extinction, which was attributed to the change in the flow rate and direction of fresh air at the inlet duct. This oscillation generated large pressure fluctuations but did not yield thermal energy with combustion.

Experimental Study on Influence of Air Supply System Difference on Smoke Shielding Performance in Air Pressure Smoke Control

In this research, a full-scale fire experiment was conducted for the purpose of estimating the influence of differences in air supply systems on smoke shielding performance in air pressure smoke control. As a result, the following items were indicated by the experiment: 1. As smoke invades from the doorway surface even prior to the smoke shield limit time in cases where smoke shield opening door is intermediately open as generally considered in the field of air pressure smoke control, smoke shields require thrust from two orthogonal surfaces with each other. 2. In static pressure systems, smoke shielding performance is fixed in spite of the smoke shield opening door angle, and previous theoretical formulae often coincide with actual values. 3. In dynamic pressure systems, smoke shielding performance differs depending on the air supply system and the angles of the door of the smoke shield opening. There are systems where smoke shielding performance is better than in static pressure systems, and there are also systems where it is worse.