Patent Publication Number: US-2019186355-A1

Title: Thermal barriers for engines and methods of making the same

Description:
This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/379,429 filed on Aug. 25, 2016, the content of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates generally to thermal barriers for component surfaces in an engine. 
     TECHNICAL BACKGROUND 
     The efficiency of combustion engines may be improved by retaining heat from ignited fuel in the combustion chamber. This can be accomplished by minimizing heat loss to the surrounding engine. One solution has been to insulate parts of the combustion chamber. A problem with insulating the combustion chamber from the surrounding engine may be creating a reliable bond between the thermal barrier and combustion chamber component surfaces. 
     Accordingly, a need exists for improved thermal barriers within combustion engines. 
     SUMMARY 
     According to an embodiment of the present disclosure, a thermal barrier is disclosed. In embodiments, the thermal barrier comprises an array of module each comprising a metallic shield. In embodiments, an edge of at least one shield in the module array overlaps the first or second edge of an adjacent shield in the module array. 
     According to an embodiment of the present disclosure, a thermal barrier is disclosed. In embodiments, the thermal barrier comprises an array of module each comprising a metallic shield. In embodiments, each shield in the module array comprises a body with a mounting portion and an overlapping portion. In embodiments, the overlapping portion of at least one shield in the module array overlaps at least a segment of the mounting portion of at least one adjacent shield in the module array. 
     According to an embodiment of the present disclosure, a method of making a thermal barrier is disclosed. In embodiments, making the thermal barrier comprises joining a portion of each shield in the module array directly or indirectly with at least one of the surfaces within an internal combustion engine. 
     Before turning to the following Detailed Description and Figures, which illustrate exemplary embodiments in detail, it should be understood that the present inventive technology is not limited to the details or methodology set forth in the Detailed Description or illustrated in the Figures. For example, as will be understood by those of ordinary skill in the art, features and attributes associated with embodiments shown in one of the Figures or described in the text relating to one of the embodiments may well be applied to other embodiments shown in another of the Figures or described elsewhere in the text. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be better understood, and features, aspects and advantages other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such detailed description makes reference to the following drawings. 
         FIG. 1  is a cross-sectional view of a combustion chamber in an engine during an intake stroke according to an exemplary embodiment. 
         FIG. 2  is a cross-sectional view of the combustion chamber in the engine of  FIG. 1  during an exhaust stroke according to an exemplary embodiment. 
         FIG. 3  is a plot of change in brake thermal efficiency (%) of an internal combustion engine at cruise operating conditions vs. piston thermal conductivity at 400° C. (W/m·° C.). 
         FIG. 4  is a perspective view of a thermal barrier on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 5  is another perspective view of the thermal barrier in  FIG. 4  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 6  is a cross-sectional view of the thermal barrier in  FIG. 4  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 7  is a perspective view of a thermal barrier on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 8  is a perspective view of a thermal barrier on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 9  is another perspective view of the thermal barrier in  FIG. 8  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 10  is a perspective view of a thermal barrier on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 11  is another perspective view of the thermal barrier in  FIG. 10  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 12  is a perspective view of a thermal barrier on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 13  is an overhead view of the thermal barrier in  FIG. 12  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 14  is a cross-sectional view of the thermal barrier in  FIG. 12  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 15  is another cross-sectional view of the thermal barrier in  FIG. 12  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
         FIG. 16  is an additional cross-sectional view of the thermal barrier in  FIG. 12  on a surface within a combustion chamber of an engine according to exemplary embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosure belongs. Although any methods and materials similar to or equivalent to those described herein can be used in the practice or testing of the present disclosure, the exemplary methods and materials are described below. 
     Engine fuel efficiency is affected by the thermal conductivity of the materials used to make the various components of an engine. This is particularly true for components within the combustion chamber of an engine (e.g., wall of the combustion chamber, pistons, valves, exhaust ports, manifolds, etc.). The higher the thermal conductivity of materials used in the combustion chamber, the more combustion energy lost to heat energy. By lowering the thermal conductivity of materials directly exposed to the combustion reaction, more energy of combustion is available for performing work and powering the engine (i.e., to drive the piston). That is, heat of combustion that is not lost to heat energy can be used to drive a turbocharger in the exhaust manifold and/or more effectively light off the catalytic converter during a cold-start of the engine. In addition, lowering the thermal conductivity of materials directly exposed to the combustion reaction may reduce the heat load on the engine&#39;s cooling system and thereby potentially improve aerodynamics of the vehicle with less air being diverted from outside the vehicle for the cooling system. Accordingly, the overall efficiency of the vehicle and engine (including fuel efficiency) may be improved with thermally resistant materials.  FIG. 3  provides a plot of change in brake thermal efficiency (%) of an internal combustion engine at cruise operating conditions vs. the piston material&#39;s thermal conductivity at 400° C. (W/m·° C.).  FIG. 3  illustrates the effect of piston material thermal conductivity on brake thermal efficiency of an engine at cruise operating conditions. The trend of  FIG. 3  evidences that the increase in efficiency of an engine at cruise conditions may improve exponentially or in a non-linear fashion by reducing the thermal conductivity of materials (for the appropriate temperature range) used within the combustion chamber. 
     Conventional methods for lowering the thermal conductivity of materials within the combustion chamber have included the use of thermal barriers. Conventional thermal barriers for combustion chambers of internal combustion engines may have one or more of several problems. One major shortcoming for conventional thermal barriers may be that the thermal barrier spalls or separates from the surface within the combustion chamber when exposed to the violent combustion kinetics, high pressures (e.g., 10 bars-500 bars), and high gas temperatures (e.g., 1000° C.-3000° C.) therein. Spalling of thermal barriers including brittle ceramic materials into the combustion chamber can cause damage (e.g., gouge, plug, etc.) to other engine components and the catalytic convertor. Another shortcoming of conventional thermal barriers may be insufficient thermal resistivity properties or a different coefficient of thermal expansion (CTE) than the combustion chamber surface which may lead to separation at high temperatures. Yet another shortcoming may be non-uniform thicknesses of conventional thermal barriers on engine component surfaces. Another short coming of conventional thermal barriers may be the development of mechanical strain within surfaces of the thermal barrier exposed to temperature cycling within a combustion chamber during engine operation. In conventional thermal barriers, thermal strain is sometimes managed by using low CTE coatings or compositional gradients through the coating thickness. These measures, however, constrain the materials available for use as a thermal barrier. Yet another shortcoming of conventional thermal barriers is their failure to utilize convective cooling mechanisms within the combustion chamber. 
     The present application is directed to a thermal barrier  200  on any metallic surface within an internal combustion engine  100 .  FIG. 1  provides a cross-sectional view of example engine  100  during an intake stroke.  FIG. 2  provides another cross-sectional view of example engine  100  with piston  104  in a full-exhaust stroke position. Engine  100  of the present disclosure may be gasoline, diesel, natural gas, propane, or any other liquid or gas hydrocarbon powered internal combustion engine including any number (e.g., 1, 2, 3, 4, 5, 6, . . . , 12, . . . ) of combustion chambers. Engine  100  includes a number of components including a combustion chamber  102  with a piston  104  therein. Piston  104  is connected to a crankshaft  110  by a connecting rod  108  within a crankcase  112  of engine  100 . Piston  104  includes a top surface  120  adjacent combustion chamber  102 . Piston top surface may be flat, bowled, domed, or any combination thereof. Piston  104  may be made from carbon steel, aluminum, or other metals typically used in automotive applications. An intake valve  106 , an intake duct  119 , an exhaust valve  114 , an exhaust duct  118 , and a spark/glow plug  116  are also adjacent combustion chamber  102 . Of course other components and configurations of engine  100  are possible and are in accordance with the present disclosure. 
     In  FIG. 2 , intake valve  106  is closed and exhaust valve  114  is open (when piston  104  is at a full-exhaust stroke position) connecting exhaust duct  118  with combustion chamber  102  and thereby forming a chamber exhaust volume  122 . Chamber exhaust volume  122  is defined by wall surfaces and end surfaces of combustion chamber  102 , a surface of intake valve  106 , a surface of exhaust valve  114 , top surface  120  of piston  104 , and walls of exhaust duct  118  (which may include a turbocharger). In another embodiment, intake valve  106  and exhaust valve  114  are closed (when piston  104  is at a full-compression stroke position) thereby forming a chamber compression volume  121  (not shown). Chamber compression volume  121  is defined by walls and top surfaces of combustion chamber  102 , a surface of intake valve  106 , a surface of exhaust valve  114 , and top surface  120  of piston  104 . In yet another embodiment, intake valve  106  is open and exhaust valve  114  is closed (when piston  104  is at a full-intake stroke position) connecting intake duct  119  with combustion chamber  102  and thereby forming a chamber intake volume  123 . Chamber intake volume  123  is defined by wall surfaces and end surfaces of combustion chamber  102 , a surface of intake valve  106 , a surface of exhaust valve  114 , top surface  120  of piston  104 , and walls of intake duct  119 . 
     Thermal barrier  200  of the present disclosure may benefit from the non-steady state operation of combustion engines. Specifically, thermal barrier  200  may protect a surface  101  in the combustion chamber during ignition and combustion of the reactants, which will cause thermal barrier  200  to heat up significantly. That is, thermal barrier  200  may also act as a “shield” or a “finned heat sink” to reduce thermal radiation to the piston surface from each combustion event. Following each combustion event in the chamber, during the remaining interval of the crank cycle, thermal barrier  200  may be convectively cooled by outgoing combustion products and incoming combustion reactants such that heat absorbed by thermal barrier  200  during combustion does not radiate to the piston surface. That is, heat of combustion captured by thermal barrier  200  may be convectively transferred or released to combustion products exiting the chamber and combustion reactants entering the chamber so that a majority of the heat of combustion does not reach the combustion chamber surfaces. Thus, thermal barrier  200  acts as a “finned heat sink” or a “heat shield” for surface  101 . 
     Thermal barrier  200  of the present disclosure may be on any metallic surface within engine  100 . In an exemplary embodiment, thermal barrier  200  is on a metallic surface  101  within combustion chamber  102 . Metallic surface  101  may be surfaces defining compression exhaust volume  121 , surfaces defining chamber exhaust volume  122 , or surfaces defining chamber intake volume  123 . In one embodiment, surface  101  may not be wall surfaces of combustion chamber  102  contacted by piston  104 . That is, thermal barrier  200  may be excluded from surfaces in chamber  102  subjected to mechanical friction from piston  104  or areas along the crevice quench that may wear or separate thermal barrier  200  from that surface. In another exemplary embodiment, metallic surface  101  is piston top surface  120 , wall surfaces and end surfaces of combustion chamber  102 , a surface of intake valve  106 , a surface of exhaust valve  114 , walls of exhaust duct  118 , or walls of intake duct  119 . 
     Thermal barrier  200  of the present disclosure includes an array of modules  201 . The array of modules  201  (also called “module array” herein) may include any number of modules  201  greater than  1  module. In embodiments, each module  201  in the array includes a fin or shield  206 . The overall length and width of thermal barrier  200  including the array of modules  201  can have any suitable lateral dimensions (e.g., from about 0.1 mm to about 100 cm), including substantially equal dimensions. In embodiments, thermal barrier  200  includes lateral dimensions substantially equivalent to the applicable surface  101  within combustion chamber  102 . In embodiments, thermal barrier  200  conforms substantially to the 2-dimensional and/or 3-dimensional contours of metallic surface  101 . That is, the shape of thermal barrier  200  may conform to the rounded or non-uniform shapes of surface  101  to which it is connected, including a curved piston top surface  120 . In embodiments, thermal barrier  200  may be discontinuous on surface  101  and localized to “hot spots” within the combustion chamber. 
       FIGS. 4-14  provide embodiments of thermal barrier  200  on surface  101 . Thermal barrier  200  includes an array of modules each including a metallic shield  206  or fin. Each shield  206  in the module array includes a body with a first edge  208  opposite a second edge  210 . Each shield  206  in the module array also includes an upper portion  212  opposite a lower portion  214 . In embodiments, at least a segment of lower portion  214  of each shield  206  in the module array joins directly or indirectly with surface  101 . In embodiments, the segment of lower portion  214  of each shield  206  joining directly or indirectly with surface  101  is contiguous second edge  210  of each shield  206  (as shown in  FIG. 4 ). 
     In embodiments, at least a segment of lower portion  214  is spaced apart from upper portion  212  of an adjacent shield  206  in the module array by a first distance D 1 . In embodiments, first edge  208  of at least one shield  206  in the module array is spaced apart from upper portion  212  of an adjacent shield in the module array by a distance D 1 . In embodiments, first edge  208  (contiguous lower portion  214 ) of at least one shield  206  in the module array is spaced apart by distance D 1  from upper portion  212  of an adjacent shield in the module array. Distance D 1  may be substantially orthogonal to surface  101 . In embodiments, at least a segment of lower portion  214  of each shield  206  is substantially parallel to surface  101 . Shield  206  and surface  101  may be joined by metallic bonding, metal-to-metal bonding, or direct mechanical attachment. The connection between shield  206  and surface  101  is configured to resist the combustion temperatures and pressures within combustion chamber  102  during operation of engine  100 . For example, shield  206  may resist spalling from surface  101  for ≥100,000 miles inside operating engine  100 . Shield  206  may be applied to surface  101  via 3-D printing, metallic plating, welding (arc, laser, plasma, or friction), brazing, plasma spraying, mechanical fastening, or other conventional methods of creating metallic bonding or metal-to-metal bonds. 
     As shown in  FIGS. 4-7 , first edge  208  of at least one shield  206  in the module array overlaps an edge  208 ,  210  of an adjacent shield  206  in the module array by a second distance D 2 . That is, the first edge  208  of at least one shield  206  in the module array overlaps with first edge  208  or second edge  210  of at least one adjacent shield  206  in the module array by second distance D 2 . In embodiments, shield edges that overlap may be in contact or spaced apart. In embodiments, one shield edge that overlaps another shield edge may be further described as above, overhanging, or on top of the other shield edge. In embodiments, first edge  208  of at least 30% of shields  206  in the module array overlap the first or second edge  208 ,  210  of at least one adjacent shield  206  in the module array by distance D 2 . In embodiments, first edge  208  of all shields  206  in the module array overlap the first or second edge  208 ,  210  of an adjacent shield  206  in the module array by distance D 2 . In embodiments, distance D 2  is measured substantially parallel to surface  101 . Distance D 2  may be measured at room temperature (e.g., 25° C.). In embodiments, distance D 2  may be measured during operation of engine  100  when thermal expansion of adjacent shields  206  forms overlap distance D 2 . That is, edges of adjacent shields  206  in the module array may not overlap at room temperature and may have to be measured at elevated temperatures (e.g., during operation of the engine) when the shields  206  are in a state of thermal expansion. 
     In additional embodiments, each shield  206  in the module array includes a body with a mounting portion  213  and an overlapping portion  215 . Mounting portion  213  connects directly or indirectly to overlapping portion  215  in an individual shield  206 . In embodiments, mounting portion  213  of each shield  206  in the module array joins directly or indirectly with surface  101 . In embodiments, overlapping portion  215  of at least one shield  206  in the module array is spaced apart by distance D 1  from mounting portion  213  of an adjacent shield  206  in the module array. In embodiments, distance D 1  is measured substantially orthogonal to surface  101 . Distance D 1  may be measured at room temperature (e.g., 25° C.) or during operation of engine  100 . In further embodiments, overlapping portion  215  of at least one shield  206  in the module array overlaps at least a fraction of mounting portion  213  of at least one adjacent shield  206  in the module array. In embodiments, the fraction of mounting portion  213  overlapped by overlapping portion  215  of at least one shield  206  in the module array may be in contact or spaced apart with overlapping portion  215 . In embodiments, overlapping portion  215  may be further described as above, overhanging, or on top of a fraction of mounting portion  213 . Overlapping portion  215  of at least one shield  206  in the module array overlaps an edge  208 ,  210  of at least one adjacent shield  206  in the module array by distance D 2 . In embodiments, overlapping portion  215  of at least  30 % of shields  206  in the module array overlap mounting portion  213  of at least one adjacent shield  206  in the module array by distance D 2 . In embodiments, overlapping portion  215  of all shields  206  in the module array overlap mounting portion  213  of an adjacent shield  206  in the module array by distance D 2 . 
     The body of each shield  206  in the module array may be rectangular (as shown in  FIGS. 4-7 &amp; 10-11 ), square, hexagonal, triangular, heptagonal, circular (as shown in  FIGS. 8-9 &amp; 12-16 ), annular, and combinations thereof. The body of each shield  206  may also be in the shape of a fin. Of course other shapes and polygons are in accordance with the present disclosure. In embodiments, thickness T 1  of each shield  206  is defined between upper portion  212  and lower portion  214 . In embodiments, shield  206  is substantially solid between upper portion  212  and lower portion  214 . Thickness T 1  of shield  206  may be from about 0.001 mm to about 5 mm, or from about 0.1 mm to about 2 mm, or even from about 0.1 mm to about 1 mm. In addition to thickness T 1 , each shield  206  also includes a length and a width. In embodiments, thickness T 1  is substantially uniform across the length and the width of shield  206 . In embodiments, the body of each shield  206  in the module array includes a substantially uniform (e.g., +/−1 mm) thickness T 1  between upper portion  212  and lower portion  214 . As shown in  FIG. 4 , thickness T 1  of shield  206  may be measured from the top of surface  101  joined to lower portion  214  of shield  206 . Upper portion  212  of each shield  206  may be configured for direct exposure to the combustion reaction (and associated temperatures and pressures) in combustion chamber  102 . In embodiments, upper portion  212  of each shield  206  may have a variation tolerance along its surface in compliance with tolerances required for combustion chamber  102  in engine  100 , such as ≤1 mm, or ≤0.01 mm. 
     In embodiments, a single or plurality of modules in thermal barrier  200  includes a support  202 . In embodiments of thermal barrier  200 , shield  206  of at least one module joins indirectly to surface  101  by a support  202 . Each support  202  includes a body with a first end opposite a second end, thereby defining a thickness T 2 . Each support  202  has a height or thickness T 2  between its opposite ends, as well as a width (or diameter). In embodiments, the first end or second end of support  202  joins directly or indirectly with surface  101 . In embodiments, the first or second end of support  202  (opposite the end joining surface  101 ) joins directly or indirectly with shield  206  in each module. Support  202  may be joined to surface  101  and shield  206  by metallic bonding, metal-to-metal bonding, or direct mechanical attachment. In other embodiments, shield  206  and support  202  may be integrally formed together such that bonding of individual pieces is not necessary. In embodiments where a module includes a support  202 , lower portion  214  or mounting portion  213  is spaced apart from surface  101  by a third distance D 3 . Distance D 3  may be substantially equivalent to the height of its support  202 . Distance D 3  may be from about 0.001 microns to about 10 mm, or from about 0.001 mm to about 4 mm, or even from about 0.001 mm to about 0.9 mm. 
     The connections between shield  206 , support  202 , and surface  101  are configured to resist the combustion temperatures and pressures within combustion chamber  102  during operation of engine  100 . For example, support  202  may resist spalling from surface  101  for ≥100,000 miles inside operating engine  100 . Support  202  may be applied to surface  101  using the various techniques disclosed herein. Thickness T 2  of support  202  may be distinct from a thickness of material comprising surface  101  by the presence of a void volume  205 . Surface  101  within combustion chamber  102  may be identified from support  202  by a lack of void volume  205 . Alternatively or additionally, an interface at the joining of support  202  and surface  101  (caused by the bonding method) may help define thickness T 2 .  FIGS. 12 &amp; 14-16  provide an exemplary embodiment of thermal barrier  200  with shields  206  joined to surface  101  by supports  202 . 
     Support  202  may have any cross-sectional shape including rectangular, annular, hexagonal, and/or any other polygon shape. Each support  202  may have a circular cross-section as shown in  FIG. 14 . Thickness T 2  of each support  202  may be from about 0.01 mm to about 10 mm, or from about 0.1 mm to about 2 mm, or from about 0.4 mm to about 2 mm, or even from about 0.5 mm to about 1 mm. In exemplary embodiments, thickness T 2  of each support  202  is substantially uniform across the length and the width of thermal barrier  200  including the array of modules  201 . Thickness T 2  of support  202  may be measured from surface  101  to a termination point (or end) of support  202  away from surface  101  (e.g., where support  202  joins directly or indirectly with shield  206 ). 
     In embodiments, support  202  and shield  206  of module  201  may be a metal element or a metal alloy commonly used in combustion chamber  102  manufacturing. The metal or metal alloy may include carbon steel, stainless steel, aluminum alloy, aluminum, nickel plated aluminum, titanium alloy, hastelloy, nickel based super alloy, cobalt-based super alloy, and combinations thereof, for example. The metal or metal alloy encompassing support  202  and shield  206  may also be other super alloys including nickel, chromium, cobalt, and combinations thereof. The metal or metal alloy of support  202  and shield  206  may have the same (or different) coefficient of thermal expansion (CTE) as the material encompassing surface  101  (assuming similar operating temperature ranges) to minimize thermal expansion stresses and failures at their connection. In an exemplary embodiment, the CTE of the metal or metal alloy of support  202  and shield  206  may be within 150% of the CTE as the material encompassing surface  101  (assuming similar operating temperature ranges). In yet another embodiment, the CTE of the metal or metal alloy of support  202  may be within 150% of the CTE of the metal or metal alloy of shield  206 . 
     In embodiments, a void volume  205  is defined between lower portion  214  of at least one shield  206  and upper portion  212  of an adjacent shield  206  in the module array. That is, void volume  205  may be defined between lower portion  214  and upper portion  212  of adjacent overlapping modules (i.e., between distance D 1 ). In embodiments, void volume  205  is defined between overlapping portion  215  of at least one shield  206  and mounting portion  213  of at least one adjacent shield  206  in the module array. In embodiments, void volume  205  is further defined between lower portion  214  and surface  101  or overlapping portion  215  and surface  101 .  FIGS. 4-8, 10, 12, and 14  illustrate the location of void volume  205  below individual modules in the array. 
     In embodiments, void volume  205  is configured to allow convective cooling of shields  205  in the module array after a combustion event. That is, combustion reaction products exiting the combustion chamber and combustion reactants (e.g., air, gasoline, diesel fuel, oil, etc.) entering the combustion chamber may flow into void volume  205  and absorb heat of combustion from shields  205  to cool thermal barrier  200 . This may prevent a majority of the heat of combustion from reaching surface  101 . Combustion reactants and products flowing from intake valve  106  to exhaust valve  114  may convectively cool thermal barrier  200  by exposure to upper portion  212  and a segment of lower portion  214  defining distance D 1  and void volume  205 . In embodiments, void volume  205  is configured to reduce fluid flow from exhaust valve  114  to intake valve  106  in combustion chamber  102 . That is, as shown in  FIG. 16 , the flow of combustion reactants and/or products (shown by arrow  400 ) contiguous thermal barrier  200  may be reduced in one direction by interaction with void volume  205  between upper portion  212  of at least one module and lower portion  214  of an adjacent module in the array. In embodiments, void volume  205  is configured to improve convective cooling of the modules  201  in thermal barrier  200 . In embodiments, void volume  205  is a tortuous volume around a plurality of supports  202  (defined by thickness T 2 ) within the module array. In embodiments, void volume  205  may be a singular void space or a plurality of discrete and/or interconnected voids. In embodiments, void volume  205  extends across at least 50% of thickness T 2 , or substantially across thickness T 2 , or up to 100% of thickness T 2 . In embodiments, void volume  205  extends across distance D 1 . In embodiments, the volumetric ratio of support  202  to vacant volume  205  along a length, width, and thickness T 2  of thermal barrier  200  may be from about 3:1 to about 1:20. 
     In embodiments where convective cooling of shields  206  is not desirable or possible (based on engine operation or performance), thermal barrier  200  may include an insulation material  204 . In embodiments, insulation material  204  is contained with vacant volume  205  between shield  206  and surface  101 . That is, vacant volume  205  is at least partially filled with insulation material  204 . Thus, a portion of vacant volume  205  is occupied (or eliminated) by the presence of insulation material  204  therein. Insulation material  204  may fill from 5% to 99% of vacant volume  205 . Referring to  FIGS. 6, 10, and 12 , insulation material  204  (shown as a cross-hatched area) is contained within vacant volume  205 . In embodiments, the volumetric ratio of support  202  to insulation material  204  along a length, width, and thickness T 1  in thermal barrier  200  may be from about 1:1 to about 1:5. In embodiments, insulation material  204  may fill the vacant volume defined along a length, width, and distance D 1 . In embodiments, insulation material  204  has a density gradient along distance D 1 . The volumetric ratio, density, and location of insulation material  204  may allow for “tuning” of thermal barrier  200  to achieve a desired thermal conductivity. 
     In an exemplary embodiment, insulation material  204  is interlocked within thickness T 2  (between shields  206  and surface  101 ) and distance D 2  (between upper portion  212  and lower portion  214  or between overlapping portion  215  and mounting portion  213 ) such that insulation material  204  does not escape, spall, or flake out from vacant volume  205  into combustion chamber  102  during operation of engine  100 . In embodiments, surface  101 , upper portion  212 , and/or lower portion  214  of at least one shield  206  in the module array may be corrugated to prevent movement (via skin friction) or loss of insulation material  204  into combustion chamber  102  during operation of engine  100 . In embodiments, lower portion  214  or overlapping portion  215  may include at least one member  218 . Member  218  may be any shape, including spherical as depicted in  FIGS. 5-7 . Member  218  may be joined to lower portion  214  or overlapping portion  215  by metallic bonding, metal-to-metal bonding, or direct mechanical attachment methods described herein. Member  218  may be configured to partially enclose insulation material  204  within vacant volume  205 . Member  218  may also prevent overlapping portion  215  from contacting mounting portion  312  during operation of the engine. Member  218  may also increase the volume and surface area of a shield and may assist with convective cooling of thermal barrier  200 . 
     Insulation material  204  may be air, a ceramic material, and/or combinations thereof. In embodiments, insulation material  204  is any material that is capable of flowing or being contained within vacant volume  205  and with a thermal conductivity from about 0.01 W/m·K to about 12.0 W/m·K at 400° C., or from about 0.1 W/m·K to about 8.0 W/m·K at 400° C., or even from about 0.1 W/m·K to about 4.0 W/m·K at 400° C. Insulation material  204  is a composition having a low thermal conductivity to increase the thermal resistivity of thermal barrier  200  (when in vacant volume  205 ) such that more energy of combustion is available for performing work and powering engine  100 . 
     In an embodiment where insulation material  204  includes ceramic material, the ceramic material may have a porosity from about 10% to about 90%, or from about 30% to about 70%. The pores of the ceramic material may include air. Example ceramic materials include, but are not limited to, yttria stabilized zirconia (YSZ), zirconium dioxide, lanthanum zirconate, gadolinium zirconate, lanthanum magnesium hexaaluminate, gadolinium magnesium hexaaluminate, lanthanum-lithium hexaaluminate, barium zirconate, strontium zirconate, calcium zirconate, sodium zirconium phosphate, mullite, aluminum oxide, cerium oxide, and combinations thereof. The ceramic material of exemplary embodiments may be ceramic foam. The ceramic material of exemplary embodiments may also be formed from aluminates, zirconates, silicates, titanates, and combinations thereof 
     In embodiments, the total thickness of thermal barrier  200  is from about 0.1 mm to about 10 mm, or from about 0.1 mm to about 5 mm. In an exemplary embodiment, thermal barrier  200  has a thermal conductivity of about 0.1 W/m·K to about 12 W/m·K at 400° C., or about 1 W/m·K to about 5 W/m·K at 400° C. Various embodiments of composite thermal barrier  200  on a surface within engine  100  are provided in  FIGS. 4-14 . Of course, combinations of these embodiments and other embodiments are in accordance with this disclosure. 
     Distance D 1  may be from about 0.001 micron to about 10 mm, or from about 0.001 micron to about 5 mm, or from about 0.01 mm to about 5 mm, from about 1 mm to about 5 mm, or even from about 0.1 mm to about 3 mm. Distance D 2  may be from about 0.001 micron to about 10 mm, or from about 0.1 mm to about 9 mm, or from about 1 mm to about 8 mm, or even from about 1 mm to about 5 mm. In embodiments, distance D 1  and distance D 2  are configured to allow penetration of combustion reactants and/or products into vacant volume  205  for convective cooling of shields  206 . In embodiments, distance D 1  and distance D 2  are configured to limit or eliminate the spalling of insulation material  204  (if present in thermal barrier  200 ) out of vacant volume  205  into combustion chamber  102 . 
     Thermal barrier  200  of the present disclosure improves conventional thermal barriers. Conventional thermal barriers may create a nonlinear temperature gradient between the combustion chamber surface on which the thermal barrier is attached and other adjacent surfaces which may be cooled by engine coolant. In one example, when a supported shield (or skin) is fixed to a surface of an internal combustion chamber, thermal expansion and contraction of the thermal barrier causes strain within the shield in areas between connection with the combustion chamber surface. That is, in conventional thermal barriers, discrete portions of the barrier are fixed to the combustion chamber surface and areas between the supports experience thermomechanical fatigue from expansion and contraction of the thermal barrier during temperature cycling in the combustion chamber. During heating, the continuous shield experiences compression in areas between the supports. During cooling, the continuous shield experiences tension in areas between the supports. This repeated process via temperature cycling in the combustion chamber can cause thermomechanical fatigue and failure. 
     Thermal barrier  200  of the present disclosure may reduce thermal strains and thermomechanical fatigue in areas between connection with the combustion chamber surface by providing breaks or segmentation in thermal barrier  200 . That is, lower portion  214  and upper portion  212  of at least two shields  206  in the module array are spaced apart by a distance D 1 . In embodiments, overlapping portion  215  and mounting portion  213  of at least two shields  206  in the module array are spaced apart by a distance D 1 . Distance D 1  is measured in the overlapping area (i.e., defined by distance D 2 ) between adjacent shields  206  in the module array as shown in  FIGS. 4-7 . As shown in the  FIGS. 4-7  embodiments, edge  208  of at least one shield in the module array overlaps with edge  210  of an adjacent shield  206  in the module array by distance D 2 . The shields  206  of the module array in the  FIGS. 4-16  embodiments can be described as overlapping, segmented shields or scales. Of course, thermal barrier  200  may include a combination of non-overlapping and overlapping edges. In embodiments, the module array includes a repeating structural pattern. As shown in  FIGS. 4-14 , thermal barrier  200  includes a repeating pattern via the plurality of modules  201  organized in a specific configuration. Thermal barrier  200  may also include a non-repeating pattern or discontinuous pattern of modules on surface  101 . Thermal barrier  200  may be located on “hot spots” within engine  100  to improve thermal resistance. Thus, by providing discrete overlapping shields or scales, thermal barrier  200  reduces thermal strains and thermomechanical fatigue in areas between connection with surface  101 . 
     As shown in  FIG. 15 , thermal barrier  200  allows for limited obstruction of flow of combustion reactants and products (shown by arrow  300 ) in one direction. For examples, flow may be from intake valve  106  to exhaust valve  114  in accordance with normal operation of combustion chamber  102 . As shown in FIG.  16 , thermal barrier  200  may restrict flow (in the area defined by distance D 1 ) of combustion reactants and products (shown by arrow  400 ) at least partially in the opposite direction in combustion chamber  102 . For example, thermal barrier  200  may reduce flow from exhaust valve  114  to intake valve  106 . In embodiments, thermal barrier  200  in  FIGS. 15 and 16  are shown on surface  101  such that a combustion chamber intake valve would be arranged on the left side of the drawing, and an exhaust valve would be arranged on the right side of the drawing. In embodiments, first edges  208  of shields  206  in the module array are closer in proximity to exhaust valve  114  of combustion chamber  102  than opposite second edges  210 . Accordingly, in embodiments, second edges  210  of shields  206  in the module array are closer in proximity to intake valve  106  of combustion chamber  102  than opposite first edges  210 . That is, first edges  208  may act as a baffle and obstruct flow from exhaust valve  114  to intake valve  106 . In embodiments, overlapping portion  215  of at least one shield  206  in the module array is closer in proximity to exhaust valve  114  of combustion chamber  102  than its mounting portion  213 . In embodiments, mounting portion  213  of at least one shield  206  in the module array is closer to intake valve  106  than overlapping portion  215 . In further embodiments, overlapping portion  215  of at least one shield  206  in the module array is closer to exhaust valve  114  that mounting portion  213 . 
     The present disclosure also includes methods of applying thermal barrier  200  to metallic surface  101  within combustion chamber  102  of engine  100 . The method includes preparing surface  101  for application of at least two modules  201 . Preparing surface  101  may include roughening, chemical etching, drilling, cleaning, or other processes of readying surface  101  for application of the plurality of modules  201  thereon. It is envisioned that the method of preparation of surface  101  will likely depend on the method of applying the array of modules on surface  101 . 
     Methods of making thermal barrier  200  may include forming an array of modules  201 . Methods of making thermal barrier  200  may include forming or joining lower portion  214  of a plurality of shields  206  on surface  101 . Methods of making thermal barrier  200  may also include forming or joining a plurality of supports  202  on shield  206 . Joining the plurality of shields  206  on surface  101  or supports  202  on shield  206  includes 3-D printing, metallic plating, mechanical fastening or threading, fusion welding, brazing, resistance welding, diffusion bonding, sintering, or other conventional methods of metal-to-metal bonding. In embodiments, supports  202  may be joined directly or indirectly to surface  101  before supports  202  are joined directly or indirectly to at least one shield  206 . Methods of making thermal barrier  200  may include deforming a portion of shield  206  to create distance D 1  between edge  208  and another edge of an adjacent shield in the module array. 
     Methods of making thermal barrier  200  may include applying thermal barrier  200  to surface  101 . Applying thermal barrier  200  to surface  101  includes joining directly or indirectly at least two shields  206  to surface  101 . Applying thermal barrier  200  to surface  101  includes joining directly or indirectly at least two supports  202  to surface  101 . Applying thermal barrier  200  to surface  101  includes joining directly or indirectly a plurality of modules to surface  101 . A support  202  or shield  206  may be joined to surface  101  via 3-D printing, metallic plating, mechanical fastening or threading, fusion welding, brazing, resistance welding, diffusion bonding, sintering, or other conventional methods of metallically bonding support  202  to surface  101  via metal-to-metal bonds. Methods of applying thermal barrier  200  to surface  101  may include the formation of vacant volume  205 . Vacant volume  205  may be formed by etching, drilling, or any other process of material or metal removal. 
     Methods of making thermal barrier  200  may also include deforming at least a segment of one shield  206  such that the outer edges of at least two module shields  206  are spaced apart by distance D 1 . Methods of making thermal barrier  200  may also include inserting insulation material  204  within vacant volume  205 . Methods of inserting insulation material  204  within vacant volume  205  may include pressure application, injection, pressing, impregnating, and other conventional methods of inserting a solid or gas insulator in vacant volume  205 . It is envisioned that inserting insulation material  204  within vacant volume  205  may be accomplished while applying shields  206  or supports  202  to surface  101 . 
     As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     It is also noted that recitations herein refer to a component of the present invention being “configured” or “adapted to” function in a particular way. In this respect, such a component is “configured” or “adapted to” embody a particular property, or function in a particular manner, where such recitations are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is “configured” or “adapted to” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.