Fundamental Experiment and Numerical Analysis of a Modular Microcombustor with Silicon Carbide Porous Medium

Abstract

The use of porous media in combustion processes has been widely researched and investigated. In this paper, the effect of employing porous media on microcombustion was studied using numerical simulation. Simulated results demonstrated good agreement with the experimental results, and thus validated the model. Analysis has been carried out with dimensional analysis and basic theorem which incorporates the Biot number in an attempt to fundamentally understand the effects brought about by equivalence ratio, thermal conductivity of the solid matrix and mass flow rate on microthermophotovoltaic (TPV) performance. One of the key results has demonstrated that the higher the equivalence ratio of the fuel/air mixture, the higher will be the mean wall temperature. A peak-shift phenomenon has been observed, where the position of maximum flame temperature shifts downstream away from the inlet at lower equivalence ratio. Results from the Biot number analysis has indicated that the higher the thermal conductivity of the wall is, the more uniform the wall temperature distribution will be. A lower mean wall temperature is obtained when the thermal conductivity of the solid matrix is installed at 50 W/mK, whereas higher mean wall temperatures can be achieved for either small (5 W/mK) or very large (500 W/mK) thermal conductivity. It is clearly evidenced that the performance of microcombustors can be markedly enhanced by incorporating a thermally effective porous medium. The theoretical understanding gained from the present research will facilitate the design of more energy efficient, stable and better controllable portable TPV on-field power systems.

Hydrogen/oxygen premixed combustion characteristics in micro porous media combustor

“…The highest efficiency of emitter with SiC as porous media is 0.182 when / = 0.8 as well, the other emission efficiency is 0.141 and 0.159 for mixture of / = 0.6 and / = 1.0. Similar outcome was also observed by Li et al [24] and Yang [22]. From the simulated results of temperature contours in 3, we can explain this phenomenon.…”

Evaluating the Energy Efficiency Performance of a Micro Combustor with and without Heat Recuperation

“…For a long time, chemical batteries have played a dominant role as the power source for MEMS and mobile electronic devices. However, there exist some major limitations such as negative environmental impacts, low power density and short usage time [1][2][3]. To overcome these limitations, there is an exacting need to develop an alternative and environmental friendly energy source with a higher power density.…”

Fundamental flame characteristics of premixed H2–air combustion in a planar porous micro-combustor

“…Assuming a thermal equilibrium is equivalent to allowing heat transfer to occur instantaneously, which inherently precludes some important features of filtration combustion, for example, excess enthalpy combustion. Despite its deficiency in physics, the one-temperature model which was implemented in modeling micro-/meso-combustors has been found to be able to yield reasonable prediction of combustor wall temperature [23,24]. Under Assumption (7), the gaseous mixture and the solid matrix have one temperature (denoted as T g ), with the porous zone being represented by a lumped parameter, that is, the effective thermal conductivity (defined as k eff ).…”

“…Furthermore, an experimental study on the critical conditions corresponding to flame stability limits (blow-off and flashback) for different combustor configurations was carried out [22]. Chua et al [23] reported their simulation and experimental study on a planar micro-combustor fully filled with SiC foam, focusing on the wall temperature and emitter efficiency. Through CFD simulations, Pan et al [24] investigated H 2 -O 2 combustion in a cylindrical micro-combustor filled with SiC porous medium.…”