Fuel-Flexible Combustor

Abstract

A liquid-hydrocarbon fuel is used to produce thermal energy by introducing the liquid-hydrocarbon fuel and air to a vaporizer. The liquid-hydrocarbon fuel is vaporized in the vaporizer to produce hydrocarbon-fuel vapor, and the hydrocarbon-fuel vapor and air are blended to form a hydrocarbon-fuel-vapor-and-air mixture. Then, hydrocarbon-fuel-vapor-and-air mixture is introduced to a catalytic combustor including a catalyst, wherein the catalyst promotes oxidation of the hydrocarbon-fuel vapor to form a carbon-dioxide- and water-vapor-containing exhaust and to generate thermal energy. The carbon-dioxide- and water-vapor-containing exhaust and air is then introduced to a recuperator, wherein the recuperator transfers thermal energy from the carbon-dioxide- and water-vapor-containing exhaust to the air to produce heated air.

What is claimed is: 
     
         1 . A method for converting a liquid-hydrocarbon fuel into thermal energy, the method comprising:
 introducing the liquid-hydrocarbon fuel and air to a vaporizer;   vaporizing the liquid-hydrocarbon fuel in the vaporizer to produce hydrocarbon-fuel vapor and blending the hydrocarbon-fuel vapor and air to form a hydrocarbon-fuel-vapor-and-air mixture; then   introducing the hydrocarbon-fuel-vapor-and-air mixture to a catalytic combustor including a catalyst, the catalyst promoting oxidation of the hydrocarbon-fuel vapor to form a carbon-dioxide- and water-vapor-containing exhaust and generate thermal energy; and then   introducing the carbon-dioxide- and water-vapor-containing exhaust and air to a recuperator, wherein the recuperator transfers thermal energy from the carbon-dioxide- and water-vapor-containing exhaust to the air to produce heated air.   
     
     
         2 . The method of  claim 1 , wherein the air introduced to the vaporizer is heated air produced by transferring thermal energy from the carbon-dioxide- and water-vapor-containing exhaust in the recuperator. 
     
     
         3 . The method of  claim 1 , wherein the vaporizer includes a porous structure and the method further comprises flowing the air through the porous structure, wherein the porous structure promotes wicking of the liquid-hydrocarbon fuel, evaporation of the liquid-hydrocarbon fuel into the air to produce evaporated-hydrocarbon fuel, and mixing of the evaporated-hydrocarbon fuel into the air. 
     
     
         4 . The method of  claim 1 , wherein the catalyst is selectively coated on selected areas of interior surfaces but not on other areas of interior surfaces of the catalytic combustor so as to selectively generate thermal energy at the selected areas of interior surfaces of the catalytic combustor. 
     
     
         5 . The method of  claim 4 , wherein the amount of the catalyst on the selected areas of interior surfaces of the catalytic combustor is varied so as to maintain a constant specific hydrocarbon-oxidation rate. 
     
     
         6 . The method of  claim 1 , wherein thermal energy is transferred from the exhaust to the hydrocarbon fuel and air within the vaporizer to form a heated hydrocarbon-fuel vapor and air mixture. 
     
     
         7 . A combustion apparatus for converting liquid-hydrocarbon fuels into thermal energy, the apparatus comprising:
 a vaporizer coupled with a source of liquid-hydrocarbon fuel and with a source of air, the vaporizer comprising a porous structure that promotes vaporization of the liquid-hydrocarbon fuel and distributes the vaporized liquid-hydrocarbon fuel into the air to form a mixed hydrocarbon-fuel-vapor-and-air product;   a catalytic combustor located downstream of the vaporizer, the catalytic combustor comprising a combustor enclosure that has internal surfaces coated with a catalyst that can cause a reaction involving the hydrocarbon-fuel vapor and the air that forms a carbon-dioxide-and-water-vapor-containing exhaust product and generates thermal energy; and   a recuperator located downstream of the combustor, wherein the recuperator is configured to transfer thermal energy from the carbon-dioxide-and-water-vapor-containing exhaust product to an air stream to form a heated air stream that can be fed to the vaporizer.   
     
     
         8 . The apparatus of  claim 7 , wherein the vaporizer is located within the recuperator, and wherein the recuperator is configured to transfer thermal energy from the carbon-dioxide-and-water-vapor-containing exhaust product to the hydrocarbon-fuel vapor and air. 
     
     
         9 . The apparatus of  claim 7 , wherein the porous structure comprises a reticulated-foam material. 
     
     
         10 . The apparatus of  claim 9 , wherein the reticulated-foam material defines pores smaller than 0.1 mm and pores larger than 0.5 mm. 
     
     
         11 . The apparatus of  claim 7 , wherein the mass of the catalyst coating per unit area of the internal surfaces of the combustor enclosure increases as the distance from the vaporizer increases. 
     
     
         12 . The apparatus of  claim 7 , wherein the combustor enclosure is cylindrical and includes a combustor outlet configured to release the carbon-dioxide-and-water-vapor-containing exhaust product from the combustor enclosure. 
     
     
         13 . The apparatus of  claim 12 , further comprising a cylindrical inner liner, comprising an upstream end and a downstream end, and located within the combustor enclosure that defines an annular space for flow of the reacting hydrocarbon-fuel vapor and air. 
     
     
         14 . The apparatus of  claim 13 , wherein the cylindrical inner liner is perforated to define a flow path for the exhaust from the annular space to the combustor outlet. 
     
     
         15 . The apparatus of  claim 13 , wherein the annular space is defined by a gap between the combustor enclosure and the cylindrical inner liner that is less than 3 mm. 
     
     
         16 . The apparatus of  claim 13 , wherein the cylindrical inner liner includes a catalyst coating that can cause a reaction involving the hydrocarbon-fuel vapor and the air that forms a carbon-dioxide-and-water-vapor-containing exhaust product and generates thermal energy. 
     
     
         17 . The apparatus of  claim 16 , wherein the mass of the catalyst coating per unit area of the cylindrical inner liner increases as the distance from the vaporizer increases. 
     
     
         18 . The apparatus of  claim 13 , further comprising a cylindrical non-metallic heat shield located within the combustor enclosure at the upstream end of the cylindrical inner liner that defines an annular space for flow of the hydrocarbon-fuel vapor and air. 
     
     
         19 . The apparatus of  claim 18 , wherein an annular gap across the annular space between the combustor enclosure and the non-metallic cylindrical heat shield is smaller than an annular gap across the annular space between the combustor enclosure and the cylindrical inner liner. 
     
     
         20 . The apparatus of  claim 7 , wherein the combustor enclosure has planar surfaces and includes a combustor outlet configured to release the carbon-dioxide-and-water-vapor-containing exhaust product from the combustor enclosure. 
     
     
         21 . The apparatus of  claim 20 , further comprising a divider between the combustor enclosure and the recuperator that defines a planar space for flow of the reacting hydrocarbon-fuel vapor and air. 
     
     
         22 . The apparatus of  claim 21 , wherein the planar space is defined by a gap between the combustor enclosure and the divider that is less than 3 mm. 
     
     
         23 . The apparatus of  claim 21 , wherein the divider includes a catalyst coating on its combustor-enclosure-facing surface that can cause a reaction involving the hydrocarbon-fuel vapor and the air that forms a carbon-dioxide-and-water-vapor-containing exhaust product and generates thermal energy. 
     
     
         24 . The apparatus of  claim 23 , wherein the mass of the catalyst coating per unit area of the combustor-enclosure-facing surface of the divider increases as the distance from the combustor outlet decreases.