Yoichi Uehara

Thermal ignition of calcium hypochlorite

Abstract Thermal Ignition of “high strength” calcium hypochlorite has been studied. From small-scale experiments, the apparent activation energy (E) and the frequency factor (A) for the ignition reaction have been obtained as follows: E = 29.5 kcal/mol; A = 8.74 × 1013/min. The critical ignition temperatures are 77°C and 75°C for commercial containers of 35.4 cm and 38.2 cm diameters, respectively. These temperatures agree closely with the extrapolated ones and the results of computer simulation based on the thermal ignition theory.

Experimental study on oscillating behaviour in a small-scale compartment fire

Abstract To investigate fire behaviour in a compartment, the effect of ventillation factor and fuel surface area was studied experimentally by using methanol as a fuel. A limit of stable combustion appeared at a small ventillation factor. As the fuel surface became larger, the stable combustion limit increased. Oscillating combustion was observed in both an unstable combustion region and a stable combustion region near the boundary of these regions. In the unstable combustion region, extinction followed the oscillating combustion. On the other hand, in the stable region the oscillating combustion lasted until the fuel was exhausted. The period of the oscillating combustion was 1·–1·5 s in the stable combustion region.

Experimental study on flammability limit of a chlorine trifuloride/dichlorosilane/nitrogen mixture

Abstract The flammability limit of a chlorine trifluoride (CIF3)/dichlorosilane (SiH2Cl2)/nitrogen (N2) mixture was investigated experimentally. In this study, a SiH2Cl2/N2 mixture was first introduced into an explosion vessel and a CIF3/N2 mixture was then injected into the vessel. Spontaneous ignition was observed during the injection when the final CIF3/SiH2Cl2/N2 mxiture was in a flammable range. Various compositions were tested to determine the flammability diagram of a CIF3/SiH2Cl2/N2 mixture. From the flammability diagram, the lower flammability limits for spontaneous ignition were found to be 0.3 vol% for both CIF3 and SiH2Cl2. Below this limit ignition did not occur even when an electronic spark was applied.

Experimental study on the intensity and probability of vapour explosions

Abstract The intensity and probability of vapour explosions caused by the contact of molten LiCl with water were studied experimentally. The temperatures of water were 10, 30, 50, 70 and 90°C, and those of LiCl were 650, 700, 750, 800, 850 and 90°C, with a mass of LiCl of 20 g. The intensity and probability were studied based on the thermal exergy of molten LiCl against water. It was found that the probability of explosion had a negative correlation with the thermal exergy, and three types of vapour explosion were identified in terms of the thermal exergy.

In-situ Heat Release Measurement Of Smoldering Combustion Of Wood Sawdust

To evaluate in-situ heat release rate of the smoldering combustion, temperature histories in a wood sawdust layer were measured. There were three distinct region in a measured temperature history. They were attributed to the preheat region, the charring region, and the decaying region. Boundaries between those regions were identified on the temperature history as points of inflection. The smoldering front was considered to be the boundary between the preheat and the charring regions. The fact that the temperature history has a point of inflection at the smoldering front means heat release at the front. The heat release rate at the front if incoming and outgoing heat fluxes at the front were evaluated. To evaluate these fluxes, temperature profile in the layer was derived from the temperature histories at several heights and spread rate of the smoldering front, which was constant during a test run. Heat release rate at the smoldering front was estimated from the difference between the incoming and outgoing heat fluxes at the smoldering front. The evaluated heat release rate showed no dependence on the atmospheric oxygen concentration. From the result, the reaction occurred at the smoldering front was considered to be a pyrolysis reaction. However, the activation energy evaluated from the heat release rate was 13.7 kJ/mol whicH is much smaller than usually referred activation energy for wood pyrolysis. Oxygen in atmosphere is considered to work, at least, as a catalyst of the reaction.