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Outer wall temperature and exergy efficiency of micro-combustor are very essential in determining micro-thermophotovoltaic energy conversion effectiveness. In this study, a swirl rib was designed to improve the thermal efficiency of micro-combustor since a swirl flow can be formed when the hydrogen/air mixture passes through the swirl rib, which increases the residence time and turbulence intensity of the mixture. Effects of position, height, spacing, and shape of the swirl rib on the thermal performance of a cylindrical micro-combustor were investigated numerically. The thermal performance shows different trends with the variation of these geometric parameters, and an optimum mean outer wall temperature of 1260 K is obtained at the distance between the inlet and the rib of 7 mm, the rib height of 1.2 mm and the rib spacing of 0.5 mm, but this optimum setting triggers the large pressure drop that impedes further improvement of the micro-combustor performance. To minimize this effect, three rip shapes including rectangle, trapezoid and inversed trapezoid was designed. The results show that the micro-combustor with trapezoidal rib presents better thermal performance. This study provides theoretical guidance for the optimal design of the hydrogen-fueled micro-combustor. |
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