Flameless cooking appliance
A flameless cooking apparatus for use with liquid fuels and for indoor or outdoor use under field operations. The burner exhibits low CO and hydrocarbon emissions and meets standards for burner thermal efficiency when used with JP-8 fuel. The apparatus employs a catalytic burner having among its parts (i) a combustion catalyst; (ii) a conductive surface, e.g., cooking surface; and (iii) in between the catalyst and the conductive surface and in direct physical contact with both surfaces, a heat spreader for conductively transferring heat of combustion from the catalyst to the conductive surface. Also claimed are a method of heat flux and a method of cooking.
1. A flameless cooking appliance comprising:
(a) a combustion chamber comprising a catalytic burner positioned as the top horizontal wall of the chamber, and further comprising one or more contiguous walls enclosing a volume of space within which flameless combustion occurs;
(b) a fuel inlet means for feeding a fuel into the combustion chamber;
(c) an oxidant first inlet means for feeding an oxidant into the chamber;
(d) an ignition means for lighting off a combustion catalyst, the ignition means positioned within the chamber; and
(e) wherein the catalytic burner comprises three components disposed in a sandwich configuration:
(i) the combustion catalyst defining a bottom face and a top face along a vertical axis and comprising a metal substrate configured with a plurality of channels of ultra-short channel length having one or more noble metals deposited thereon, the combustion catalyst positioned interior to the chamber in a direction downstream of the fuel inlet means and oxidant first inlet means such that the fuel inlet means and oxidant first inlet means are configured to deliver fuel and oxidant to the bottom face of the combustion catalyst and combustion gases exit the top face of the combustion catalyst;
(ii) a thermally-conductive metal heat spreader comprising a plurality of metal sheets bent and folded into a structure of alternating ridges and furrows forming corrugated fins having multiple flat contact surfaces configured for thermal conductive heat transfer; and
(iii) a heat conductive surface comprising an interior face positioned interior to the chamber and an exterior face positioned exterior to the chamber; and
further wherein the heat spreader is disposed inside the area between the combustion catalyst and heat conductive surface, wherein the heat spreader is in conductive contact with and is sandwiched in between the combustion catalyst and the heat conductive surface, and the heat spreader multiple flat contact surfaces comprises a plurality of solid-to-solid thermally conductive contact surfaces overlaid across the top face of the combustion catalyst and also overlaid across the interior face of the heat conductive surface; the heat spreader further providing a plurality of channels for exhausting combustion gases from the combustion chamber.
2. The apparatus of claim 1 further comprising a swirling means for mixing the fuel and oxidant prior to contact with the combustion catalyst.
3. The apparatus of claim 1 further comprising a recuperator comprising a heat conductive material, the recuperator positioned in fluid communication with the channels of the heat spreader and further positioned adjacent to the oxidant first inlet means and configured to share a heat exchanging wall with the oxidant first inlet means.
4. The apparatus of claim 3 wherein the recuperator is a heat conductive material selected from aluminum and stainless steel, optionally, having a surface that is flat, corrugated, or shaped into a plurality of fins.
5. The apparatus of claim 1 wherein the metal substrate comprises a metal mesh and the one or more noble metals are selected from platinum, palladium, and rhodium.
6. The apparatus of claim 1 wherein the ignition means comprises a glow plug.
7. The apparatus of claim 1 wherein the metal heat spreader is selected from stainless steel, aluminum, copper, and alloys of nickel.
8. The apparatus of claim 7 wherein the metal heat spreader sheets have a thickness from 25 μm to 500 μm.
9. The apparatus of claim 1 wherein the metal substrate is provided in a stack of from 2 to 20 layers.
10. The apparatus of claim 1 wherein the fuel inlet means is configured to feed and atomize a liquid fuel.
11. The apparatus of claim 10 wherein the fuel inlet means comprises a nozzle or injector configured to feed and atomize a liquid fuel.
12. The apparatus of claim 1 wherein the metal substrate has an ultra-short channel length ranging from 25 microns to 500 microns.
13. The apparatus of claim 1 further comprising an oxidant second inlet means positioned upstream of the catalytic burner and positioned to facilitate atomization of the fuel fed through the fuel inlet means.