Electrical and thermal insulation for a combustion system

Abstract

An electrically enhanced combustor includes bilayer insulation. A thermal insulator protects an electrical insulator from high temperatures that could cause the electrical insulator to become at least somewhat electrically conductive.

What is claimed is: 
     
         1 . A combustor, comprising:
 a furnace wall defining a combustion chamber configured to enclose a combustion reaction;   a power supply configured to output a high voltage; and   a charger operatively coupled to the power supply and to the combustion chamber and configured to receive the high voltage from the power supply and to cause the combustion reaction to carry a charge;   wherein the furnace wall includes a conductive wall adjacent to an outside volume, a thermal insulator adjacent to the combustion chamber, and an electrical insulator disposed between the thermal insulator and the conductive wall.   
     
     
         2 . The combustor of  claim 1 , wherein the thermal insulator is configured to thermally insulate the electrical insulator from the combustion volume; and
 wherein the electrical insulator is configured to electrically insulate the conductive wall from the thermal insulator and the combustion volume.   
     
     
         3 . The combustor of  claim 1 , wherein the conductive wall defines a water jacket. 
     
     
         4 . The combustor of  claim 1 , wherein the outside volume is accessible to a human during normal operation of the combustor. 
     
     
         5 . The combustor of  claim 1 , wherein the electrical insulator includes steatite. 
     
     
         6 . The combustor of  claim 1 , wherein the electrical insulator is configured as a plurality of continuous planes respectively held by gravity adjacent to the conductive wall. 
     
     
         7 . The combustor of  claim 1 , wherein the electrical insulator is configured as a plurality of tiles. 
     
     
         8 . The combustor of  claim 7 , wherein the electrical insulator is configured as a plurality of tiles with air gaps therebetween. 
     
     
         9 . The combustor of  claim 1 , wherein the electrical insulator includes a vacuum. 
     
     
         10 . The combustor of  claim 1 , wherein the electrical insulator includes air. 
     
     
         11 . The combustor of  claim 1 , wherein the thermal insulator includes a ceramic fiber, a refractory fiber, or a refractory ceramic fiber. 
     
     
         12 . The combustor of  claim 1 , wherein the thermal insulator includes a vitreous aluminosilicate fiber. 
     
     
         13 . The combustor of  claim 1 , wherein the thermal insulator includes cordierite. 
     
     
         14 . The combustor of  claim 1 , wherein the thermal insulator includes Mullite. 
     
     
         15 . The combustor of  claim 1 , wherein the thermal insulator includes alumina. 
     
     
         16 . The combustor of  claim 1 , wherein the thermal insulator includes an aerogel. 
     
     
         17 . The combustor of  claim 1 , wherein the thermal insulator is formed as a honeycomb material. 
     
     
         18 . The combustor of  claim 1 , wherein the thermal insulator includes quiescent air channels. 
     
     
         19 . The combustor of  claim 1 , wherein the thermal insulator is configured to insulate the electrical insulator sufficiently to maintain at least 10 megaohms per square. 
     
     
         20 . The combustor of  claim 1 , wherein the thermal insulator is configured to insulate the electrical insulator sufficiently to maintain at least 20 megaohms of resistance to ground. 
     
     
         21 . The combustor of  claim 1 , wherein the conductive wall is in electrical continuity with electrical ground. 
     
     
         22 . The combustor of  claim 1 , wherein the power supply is configured to output a high voltage greater than 1000V magnitude. 
     
     
         23 . The combustor of  claim 22 , wherein the power supply is configured to output a high voltage equal to or greater than 15 kV magnitude. 
     
     
         24 . The combustor of  claim 1 , wherein the thermal insulator includes:
 a first thermal insulator layer;   a second thermal insulator layer; and   an electrically floating electrical conductor positioned between the first and second thermal insulator layers.   
     
     
         25 . The combustor of  claim 1 , wherein the combustor is a solid fuel burner. 
     
     
         26 . The combustor of  claim 1 , wherein the combustor is a gas burner. 
     
     
         27 . The combustor of  claim 1 , further comprising:
 a second power supply voltage lead configured to carry a voltage; and   a region of the thermal insulator operatively coupled to second power supply voltage lead.   
     
     
         28 . The combustor of  claim 27 , wherein the thermal insulator becomes electrically conductive at elevated temperatures responsive to heating by the combustion reaction; and
 wherein at least the region of the thermal insulator is configured to operate as an electrode upon being heated by the combustion reaction.   
     
     
         29 . The combustor of  claim 27 , wherein the second power supply voltage lead passes through an aperture defined by the conductive wall. 
     
     
         30 . A method comprising:
 supporting a combustion reaction in a combustion chamber;   maintaining a first voltage on a conductive wall of the combustion chamber;   electrically insulating the conductive wall from the combustion reaction with an electrical insulation layer;   thermally insulating the electrical insulation layer from the combustion reaction with a thermal insulation layer separate from the electrical insulation layer; and   applying a second high voltage to the combustion reaction.   
     
     
         31 . The method of  claim 30 , wherein maintaining the first voltage includes maintaining electrical continuity with electrical ground. 
     
     
         32 . The method of  claim 30 , wherein applying the second high voltage includes applying between 1000V and 15,000V to the combustion reaction. 
     
     
         33 . The method of  claim 30 , further comprising applying a third voltage to the thermal insulation layer. 
     
     
         34 . The method of  claim 33 , wherein applying the third voltage to the thermal insulator includes applying the third voltage to a conductor that passes through an aperture in the conductive wall and the electrical insulation layer. 
     
     
         35 . The method of  claim 33 , wherein the thermal insulator becomes electrically conductive at a temperature characteristic of the combustion reaction; and
 wherein applying the third voltage to the thermal insulator includes causing a portion of the thermal insulator to operate as an electrode.   
     
     
         36 . The method of  claim 30 , further comprising cooling the conductive wall by passing water through a water jacket thermally coupled to the conductive wall. 
     
     
         37 . The method of claim of  claim 30 , further comprising:
 passing a fuel for the combustion reaction into the combustion chamber through a conductive grate; and   applying a third voltage to the conductive grate.   
     
     
         38 . The method of  claim 30 , wherein the thermal insulation layer includes quiescent air channels. 
     
     
         39 . The method  claim 30 , wherein the thermal insulation layer includes a vitreous aluminosilicate fiber. 
     
     
         40 . The method of  claim 30 , wherein the thermal insulator layer includes cordierite. 
     
     
         41 . The method of  claim 30 , wherein the electrical insulator layer comprises a plurality of steatite tiles separated from each other by air gaps. 
     
     
         42 . The method of  claim 30 , wherein applying a second high voltage to the combustion reaction further comprises:
 passing a gas stream into the combustion chamber;   operating a charger to output charged particles to the gas stream; and   electrically energizing the combustion reaction with the charged particles from the charger.