Swiss Roll Combustors
The Swiss-roll combustor is a combustor inside by a spiral heat exchanger (Figure 1 Left) and was first proposed by Professor Weinberg in 1974. The cold reactants swirl into the center reaction zone through a spiral inlet channel. After exothermic reaction, the hot products swirl out through the adjacent spiral outlet channel. The heat from the products is exchanged to the cold reactants via the spiral heat exchanger. This raises the temperature of the reactants above their adiabatic temperature and this excess enthalpy enables combustion to be self-sustained in either ultra-lean or ultra-rich conditions that are beyond the flammability limits without heat recirculation.
Many studies have demonstrated its superior performance in heat recirculation and the effect on promoting internal reaction. Specifically, it has been shown effective at extending the flammability of a variety of fuels and enabling achievement of equilibrium state concentrations. Several features make the Swiss-roll combustor extremely thermally efficient. First, the large heat transfer to heat loss area ratio enables highly efficient heat exchange in a very confined volume. Second, the curvature of the channel creates a centrifugal instability (Dean vortices) that further enhances heat transfer. Third, the reaction zone, which has the largest potential for heat loss, is surrounded by the spiral heat exchanger so most of heat loss from the reaction can be recovered. Fourth, long inlet channels with elevated temperature provide a long residence time that may significantly reduce the formation of non-equilibrium state products.
ACT has been developing Swiss-roll related technologies together with Professor Paul Ronney at University of Southern California (USC). Extensive experimental work and detailed CFD based modeling (Figure 2) has been performed to understand the effect of heat recuperation on the chemical reaction. Fuel reformers are currently being developed. In addition, new fabrication methods have been developed at ACT including high temperature brazing (Figure 3 Right) and 3D printing of metal reactors (Figure 3 Left).
 Lloyd, S. and Weinberg, F., “A Burner for Mixtures of Very Low Heat Content,” Nature, 251, 47-49 (1974).
 Jones, A., Lloyd, S., and Weinberg, F., “Combustion in Heat Exchangers,” Proceedings of the Royal Society of London Section A, 360, 97-115 (1978).
 Chen, C. and Ronney, P., “Three-dimensional Effects in Counterflow Heat-recirculating Combustors,” Proceedings of the Combustion Institute, 33, 3285-3291 (2011).
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