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A unique feature of reciprocating combustion in porous media is the systems capability to sustain combustion of extremely dilute fuel gases and to maintain steep temperature gradients in the inlet and outlet area of the porous media. However, for porous media with a high thermal conductivity, which are considered for application in thermoelectric conversion, the temperature gradients decrease; without a steep temperature gradient, reaction occurs in a wide region of the porous medium and it becomes difficult to establish a stable flame position. To counter this problem, a new arrangement of the porous media with a center space is proposed that stabilizes flame position for a wide operating range. Additionally, the new system largely extends the flammable range and reduces the specific energy input needed to sustain combustion. Overall, the effectiveness to generate a temperature difference in porous media with high thermal conductivity could be improved by the new system. Besides flame stabilization, an additional interesting feature of introducing a center space is the possibility of fuel injection into it, which leads to increased maximum temperatures (i.e., to a heat release at a higher energy level). This presents a great advantage over conventional reciprocating combustion in porous media where the maximum temperature is limited by the temperature of self-ignition for the premixed combustible gases. |
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