Abstract
A three-dimensional CFD model of a novel configuration of catalytic micro-combustor inspired by the nasal geometry of reindeer was developed using the commercial code ANSYS Fluent 19.0. The thermal behavior of this nature-inspired (NI) configuration was investigated through simulations of lean propane/air combustion performed at different values of residence time (i.e., inlet gas velocity) and (external convective) heat transfer coefficient. Simulations at the same conditions were also run for a standard parallel-channel (PC) configuration of equivalent dimensions. Numerical results show that the operating window of stable combustion is wider in the case of the NI configuration. In particular, the blow-out behavior is substantially the same for the two configurations. Conversely, the extinction behavior, which is dominated by competition between the heat losses towards the external environment and the heat produced by combustion, differs. The NI configuration exhibits a greater ability than the PC configuration to keep the heat generated by combustion trapped inside the micro-reactor. As a consequence, extinction occurs at higher values of residence time and heat transfer coefficient for this novel configuration.
Highlights
Hydrocarbon-fueled micro-combustors have been proposed to replace batteries in portable electronic devices [1,2], their main advantage being related to the high gravimetric energy density of hydrocarbons
The extinction behavior, which is dominated by competition between the heat losses towards the external environment and the heat produced by combustion, differs
On the basis of the results obtained from simulations run by varying the inlet gas velocity, we have supposed that the differences between the PC configuration and the NI configuration stem mainly from their different ability to keep the heat produced by combustion trapped inside the micro-reactor
Summary
Hydrocarbon-fueled micro-combustors have been proposed to replace batteries in portable electronic devices [1,2], their main advantage being related to the high gravimetric energy density of hydrocarbons. When reducing the reactor scale from macro to micro, the surface area-to-volume ratio increases This may lead to an increase of heat losses towards the external environment with respect to the heat generated by combustion, reducing the operating window of stable combustion. This configuration was obtained by curling up a straight channel into a spiral, providing large ratios of internal heat exchange area to external heat loss area. The spiral is characterized by a higher temperature and a higher contribution from homogeneous chemistry [21] In this context, nature can play a significant role in inspiring more energy-efficient equipment. Inspired by the efficient heat management of the reindeer nasal geometry, we here propose a novel spiral catalytic micro-combustor. For the sake of comparison, simulations at the same conditions were run for a standard parallel-channel (PC) configuration of equivalent dimensions
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