Numerical investigation on the mixing performance of H2 and air in curved micro-channel combustors

Curved micro-channels are frequently used in micro-Swiss roll combustors and other applications. The secondary flows (i.e., Dean vortices) play an important role in both the mixing performance of fuel and oxidant and the flame propagation characteristics in curved micro-channel combustors. In the present study, the helicity method was adopted and a mixing performance evaluation criterion (MPEC) was proposed to investigate the impacts of inlet velocity, nominal equivalence ratio (4) and curvature radius on the Dean vortices and mixing performance of H2 and air in curved micro-channels. First, it is found that with the increase of inlet velocity, the intensity of Dean vortices increases and their shape grow asymmetrical. When the inlet velocity is high enough, another pair of smaller vortices appear near the outer wall. Meanwhile, the mixing performance of H2 and air becomes worse due to the reduced residence time of gas flow. Second, as the nominal equivalence ratio is decreased, the Dean vortices are intensified and the vortices shape become asymmetrical. Moreover, the mixing process is improved owing to the enhanced secondary flows. Thirdly, the intensity of Dean vortices increases significantly as the curvature radius is decreased. However, the mixing performance becomes worse due to the shortened length of the curved micro-channel. Finally, an empirical correlation between MPEC and the Reynolds number (Re), Dean number (De) and 4 was obtained based on the numerical results, which may provide a guidance for the design and operation of curved micro-channel combustors.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.