Exhaust plenum chamber constructions including thermal barrier coatings for opposed-piston engines

Abstract

An exhaust plenum chamber with a thermal barrier coating for an opposed-piston engine reduces heat rejection to coolant, while increasing exhaust temperatures, fuel efficiency, and quicker exhaust after-treatment light-off. The exhaust plenum chamber can include a coating on the inside surface of the chamber. Posts which are structural and provide cooling channels or passageways can be present in the exhaust plenum chamber and coated with the thermal barrier coating material.

What is claimed is: 
     
         1 . An opposed-piston engine, comprising:
 a cylinder block;   a cylinder disposed in the cylinder block, the cylinder including a cylinder wall having an interior surface defining a bore centered on a longitudinal axis of the cylinder and intake and exhaust ports formed in the cylinder wall near respective opposite ends of the cylinder, the intake and exhaust ports each including an array of port openings extending through the cylinder wall to the bore;   an exhaust plenum chamber in the cylinder block in which the exhaust port of the cylinder is situated such that the exhaust plenum chamber receives all exhaust gas from the cylinder; and   a coating on an inside surface of the exhaust plenum chamber that reduces heat transfer from exhaust gas to the cylinder block.   
     
     
         2 . The opposed-piston engine of  claim 1 , wherein the exhaust plenum chamber comprises at least one support post of the engine block. 
     
     
         3 . The opposed-piston engine of  claim 2 , wherein the support post comprises a coolant passageway. 
     
     
         4 . The opposed-piston engine of  claim 3 , wherein liquid coolant flows through the coolant passageway during operation of the engine. 
     
     
         5 . The opposed-piston engine of  claim 1 , wherein the coating comprises a thermally insulating material. 
     
     
         6 . The opposed-piston engine of  claim 5 , wherein the thermally insulating material has a low coefficient of thermal conductivity. 
     
     
         7 . The opposed-piston engine of  claim 5 , wherein the coating comprises any one of zirconia, alumina, a chrome-containing composition, a cobalt-containing composition, a nickel-containing composition, and an yttrium-containing composition, or any combination thereof. 
     
     
         8 . The opposed-piston engine of  claim 5 , wherein the coating is spray deposited or dip coating deposited onto the inside surface of the exhaust plenum chamber. 
     
     
         9 . The opposed-piston engine of  claim 1 , wherein the exhaust plenum chamber includes a base metal that comprises gray iron. 
     
     
         10 . The opposed-piston engine of  claim 1 , further comprising a plurality of cylinders in the cylinder block, the cylinders being disposed in an inline array. 
     
     
         11 . The opposed-piston engine of  claim 10 , wherein each cylinder comprises a liner retained in a tunnel in the cylinder block. 
     
     
         12 . The opposed-piston engine of  claim 1 , wherein the cylinder comprises a liner retained in a tunnel in the cylinder block. 
     
     
         13 . The opposed-piston engine any one of  claims 1 ,  10 , and  12 , wherein the exhaust plenum chamber further comprises at least one exhaust outlet, the at least one exhaust outlet being in fluid communication with one or more of a turbine inlet, an EGR inlet, and an after-treatment device. 
     
     
         14 . The opposed-piston engine of any one of  claims 1 ,  10 , and  12  wherein the exhaust plenum chamber comprises at least one engine block support post with a coolant passageway fluidly coupled to a source of liquid coolant. 
     
     
         15 . A method of making an exhaust plenum chamber of an opposed-piston engine, the method comprising applying a coating layer comprising a material of low thermal conductivity to an inside surface of the exhaust plenum chamber, the exhaust plenum chamber comprising at least one post. 
     
     
         16 . The method of  claim 15 , further comprising preparing a base metal of the inside surface of the exhaust plenum chamber for application of the coating layer. 
     
     
         17 . The method of  claim 15  or  16 , further comprising treating the exhaust plenum chamber after application of the coating layer. 
     
     
         18 . The method of  claim 15 , wherein the exhaust plenum chamber further comprises a floor and a ceiling, and wherein the at least one post extends from the floor to the ceiling. 
     
     
         19 . The method of  claim 18 , wherein the at least one post comprises a conduit or passageway through a center portion of the at least one post, and further wherein the conduit or passageway is fluidly connected to a source of cooling fluid.