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The Combustion under Microgravity

Isolated fuel droplet combustion under microgravity

Atomizing combustion is used in internal-combustion engines such as gas turbines and diesel engines. Understanding the mechanism of atomizing combustion is of very importance for the improvement of internal-combustion engines. However, fluid flow and interference of cloud of droplets, and the difference of the diameter of the droplets makes the combustion phenomenon complex. Thus, an isolated fuel droplet, which is a minimum element of a fuel spray, have been widely used to conduct an experiment for the understanding of fundamental element of atomizing combustion. The diameter of the droplets in fuel spray of internal-combustion engines is about 30μm to 80μm, where the effect of buoyancy is ignorable. Due to the limitation of resolution capability, the diameter of the droplets used in the experiment is about 1mm. We imitate the droplets of fuel spray by conducting the experiment in microgravity. In microgravity, the effect of natural convection is excluded, and spherical flame as shown in the figure is formed which enables one-dimensional simple analysis.

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Droptower and experimental setup

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The combustion of isolated droplet under microgravity

The Reseach on Solid Combustion under Microgravity

The fire prevention criteria used in International Space Station has been established based on the past experiences and these criteria should be upgrades based on the scientific knowledge. The effect of the gravity on the combustion phenomena should be revealed with the experiments under microgravity condition and new standard experiment methods for the safety criteria should be established. The experimental researches under microgravity condition in the droptower and parabolic flights will be conducted and the result of those experiments will be compared with the past standards of NASA. This research is not only application oriented but also has scientific aspects such as the solid combustion without gravity or the effect of ignition limit under microgravity condition. This research will contribute the safety in ISS and other future space stations.

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ISS on orbit