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ABSTRACT
The requirement for efficient power sources for portable electronics and miniature mechanical devices, such as laptops, micro robots, or micro aerial vehicles, has led to research on the ultra micro gas turbine (UMGT). The ultra micro gas turbine is one of the most promising power sources for small-scale applications due to its higher power and energy densities compared to currently used batteries. In order to realize UMGT as a viable power source, its individual components have to be developed, since downscaling introduces new problems for each component. Since the micro combustor is one of the key components of UMGT, it has to be improved. Until now, it has been very difficult for micro combustors to achieve wide flame stability, high combustion efficiency, and clean combustion with low pressure loss, due to the associated downscaling problems, such as high heat loss and small residence time. In order to achieve wide flame stability, the effect of preheating the reactants on flat flame stabilization was investigated experimentally on a 46-mm inner diameter quartz-walled flat flame combustor. The experimental results showed that preheating improves flat flame stabilization. Since preheating increases the burning velocity, flat flame can stabilize at higher incoming flow velocities as long as they are lower than the burning velocities. From the relationship between the incoming flow velocities and burning velocities, a correlation was obtained for flat flame micro combustors for micro power generation applications. With this correlation, it is possible to determine the minimum combustor diameter required for stable flat flame combustion. Also, in order to have a stable flat flame at higher mass flow rates, the correlation enables the calculation of the required reactants temperature, and is a major contribution to the design of micro combustors.
Acknowledgments
The authors would like to thank Alan Eaton and Martin Ryder for their help with the experimental setup and the measurements. The principal author gratefully acknowledges Prof. Toshio Nagashima, Mr. Yamaguchi Kazuo, and A. Prof. Okamoto Koji of the University of Tokyo and Prof. Saburo Yuasa and Assis. Prof. Takashi Sakurai of the Tokyo Metropolitan University for all their contributions and guidance throughout the prototyping and testing of the HEX-Combustor.