Abstract
The flame characteristics of pool fires such as their height vary depending on gravity. To improve our understanding of the effects of gravity on flame characteristics, we experimentally investigated small-scale pool fires under conditions of normal to partial gravity; using the drop tower at Hirosaki University in Japan to obtain arbitrary partial gravity condition, which varied from 1 G to 0.55 G. We performed the measurement of the temperature distribution with a thermocouple and that of the flame shape with a digital camera. Based on these data, we estimated radiative heat feedback using our new model “The radiative absorption model”. It becomes easy to estimate radiative heat transfer using this model if flames have complicated shapes and time variability. From these analyses, we made clear that the radiative heat feedback of small-scale pool fires decreases under partial gravity environment.
Highlights
In recent years, the range of human activity is expanding to various gravity environments, for example, the exploration of Mars and the utilization of the International Space Station (ISS)
4.1 Temperature Distribution around Pool Fires Figure 6 shows the distribution of the temperature around pool fires T [K] in the direction of r. (a) is the distribution of the ethanol pool fire at z = 2.3 mm, and (b) is that of the acetone pool fire at z = 2.1 mm
While the temperature difference between G = 1 and G = 0.55 around the centers of the pool fires is small, the difference increases as r becomes larger
Summary
The range of human activity is expanding to various gravity environments, for example, the exploration of Mars and the utilization of the International Space Station (ISS). It is clear that the flame height of small-scale pool fires decreases as gravity levels decline. To clarify the mechanism of flame height decrease, flow field research of pool fires was performed by Yoshihara et al. the mechanism is not sufficiently clear. The direct measurement of radiative heat feedback is difficult, so we have to estimate it based on the flame shape of pool fires. The view factor model is originally applied to the radiative heat transfer between solid surfaces, so it assumes flame as solid or solid surface. It is hard to use these existing models to estimate the radiative heat feedback to the fuel surface of pool fires
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