Patent Application
20230417162
The present disclosure relates generally to systems using thermal barrier coatings, and more particularly, to the use of thermal barrier coatings to modify thermal characteristics of engine components.
The components of an internal combustion engine often experience damage caused by the use of the engine. One example of the type of damage or wear that can occur is frictional damage (or frictional wear) caused by the movement of engine component surfaces against each other, such as the piston rings and inside cylinder wall of a cylinder. This relational movement cases surface damage to the components. To minimize frictional wear, in addition to smoothing the surfaces of the contacting components, liquid lubricants such as oil or coatings such as Teflon (R) are often used. These lubricants or coatings provide an interface whereby the damage to the engine components is reduced. The oil reduces the friction between moving component, helps cool the components, and remove contaminants.
Engine components can also be damaged due to excessive heat. As most components in a typical combustion engine are comprised of a metal or metal alloy, excessive heat can degrade the crystalline structure of these components. If the crystalline structure of the metal or metal alloy is degraded enough, the metal or alloy can become brittle and break. The damage to the metal or alloy crystalline structure can be caused in a single overheating event or over time. In some instances, even a typical engine operating temperature, not an overheating event, can initiate damage to some components. The damage to the crystalline structure is often irreversible, meaning that the engine component's structural integrity has degraded and will not improve, and more significantly, will likely continue to degrade over time and the continued operation of the engine.
Engine components can also be damaged due to the differential heat across the component itself or proximate components. As discussed herein, “differential heat” describes a condition in which one location of the component (or proximate component) has a different temperature than another location of the component (or proximate component). Different (or differential) temperatures can cause damage for various reasons. For example, different temperatures within the same component can cause microscopic stress fractures caused by an uneven expansion of material. These stress fractures in the crystalline lattice of the metal increase in number and size as the component is used, potentially leading to an eventual failure of the component.
A mechanism for carbon capture is described in Japanese Publication No. JP20005337180A (hereinafter referred to as “the '180 reference”). In particular, the '180 reference describes a system directed toward mitigating the potential wear on engine components caused by excessive engine temperatures. The system of the '180 reference describes the use of thermal barrier coatings to coat components of a turbine engine. The thermal barrier coating is tested for structural integrity under the temperature conditions found in the turbine engine. However, the disclosure of the '180 reference discloses issues with the thermal barrier coatings themselves, not the components to which the thermal barrier coatings are applied. Thus, the system described in the '180 reference is still prone to component wear and possible damage caused by, for example, the differential heat across the component itself or proximate components.
Examples of the present disclosure are directed to overcoming deficiencies of such systems.
In one aspect of the present disclosure, an engine component includes a surface, a first area of the surface having a first rate of temperature change, a second area of the surface having a second rate of temperature change, wherein the second rate of temperature change is lower than the first rate of temperature change, and a first coating of a thermal barrier coating applied to the first area, the first coating configured to reduce a rate of heat transfer into and out of the first area to reduce a difference of a rate of temperature change between the second area and the first area.
In another aspect of the present disclosure, a method of modifying an engine component includes identifying an engine component for thermal characteristic modification, determining a thermal map across a surface of the engine component, and applying a first coating of a thermal barrier coating to the surface to reduce a temperature difference between a first area of the surface and a second area of the surface.
In a still further aspect of the present disclosure, a valve for use in an internal combustion engine includes a stem, a head that transitions from the stem, the head comprising a surface that receives a portion of heat generated during a combustion of a fuel, wherein the surface comprises a first area having a first rate of temperature change and a second area having a second rate of temperature change, wherein the second rate of temperature change is lower than the first rate of temperature change, and a first coating of a thermal barrier coating applied to the first area, the first coating configured to reduce a rate of heat transfer into and out of the first area to reduce a difference of a rate of temperature change between the second area and the first area.
Technologies described below are directed to systems and methods for using thermal barrier coatings to modify engine component thermal characteristics. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
The cylinder head 100 includes chamber interface section 110. When mated to a cylinder of an engine block, the volume between a piston of the engine block and the chamber interface section 110 forms a combustion chamber whereby fuel is combusted by the combustion engine. The chamber interface section 110 includes a bowl 112, sometimes referred to as a “firedeck,” that provides an enclosed space for gases compressed by the cylinder near the end of the compression stroke (or top dead center) to ignite. The expanding gases resulting from the ignition of the fuel force a piston, during a power stroke, to move or rotate a component, typically a crankshaft if the engine is used for motive power. However, it should be noted that the pistons can also move or turn other components in different engine types such as a shaft for power generation. The presently disclosed subject matter is not limited to any particular use for a compression engine. Further, the presently disclosed subject matter is not limited to any type of fuel, such as gasoline or diesel engines. Additionally, the presently disclosed subject matter is not limited to any specific compression cycle, as two or four stroke cycle engines, as well as other internal combustion engine types, are considered to be within the scope of the presently disclosed subject matter.
As discussed above, in some operating conditions engine components can be damaged due to the differential heat across the component itself or components proximate to the engine component, wherein one location or area of the component (or proximate component) has a different temperature than another location of the component (or proximate component). Differential heat can be caused by numerous factors, including different rates of change of temperature. For example, if a part (or area) of a component heats up faster (or cools down faster) than an adjacent or proximate area of the component, the difference in the rate of change of temperature between the two (or more) parts of the component can cause a differential temperature across the component. This differential temperature can cause one part of the component to expand and contract at a different rate and degree than the other part, thus potentially introducing structural defects in the crystalline lattice of the component.
The differential rate of temperature change can be caused by various factors, including a location (i.e., whether or not the component or part of the component is close to or far away from a combustion chamber or a proximity to a cooling source), the size of the area, the alloying of the components, and the like. For example, in
As illustrated in
The different temperatures between the lobes 114 and the bridges 120 during heating and cooling can cause structural defects. These defects can result because the same metal will experience a higher degree of expansion at a higher temperature than at a lower temperature, and also, will experience a higher degree of contraction at a lower temperature than a higher temperature. Thus, because the different areas of the bowl 112, e.g., the lobes 114 and the bridges 120, can be at different temperatures as heat is applied and removed, the different areas will have different degrees of expansion and contraction. Materials such as metals typically expand and contract as the temperature of the materials change. The degree at which the material expands depends on the crystalline structure of the material, but in general, as metal is heated, the metal expands, and conversely, as the metal is cooled, the metal contracts. Therefore, for a given metal, the amount of expansion and contraction depends on the temperature change of the metal. In a steady state situation, whereby the entirety of a metallic component is at or about a single temperature, substantially all the areas of the component have expanded or contracted equally. However, in a non-steady state situation, whereby some areas of the component are at a different temperature than other areas of the component, the amount of expansion/contraction is substantially dependent on the temperature of that area.
To reduce or eliminate the difference in temperature between the lobes 114 and the bridges 120 to reduce the different degrees of expansion and/or contraction between the lobes 114 and the bridges 120, thermal barrier coating (TBC) 124A-124D (referred to herein generally as “the thermal barrier coating 124” and individually as “the thermal barrier coating 124A,” “the thermal barrier coating 124B,” and the like) is applied. A used herein, a “thermal barrier coating” comprises one or more materials that are bonded or applied to a surface, such as the bowl 112. A thermal barrier coating, due to its relatively lower thermal conductivity than the material to which the TBC 124 is bonded to, provides a degree of thermal insulation to the coated surfaces. The insulative properties of the TBC 124 reduces the rate at which heat is transferred into and out of the area to which the TBC is applied. This reduction in the rate of heat transfer can be used to compensate for the different rates of temperature change that may be found in a component, such as the bowl 112.
The TBC 124 can be constructed from various materials including, but not limited to, ceramics or alloys such as Zirconia, Nickel Chromium Aluminum Yttrium (NiCrAlY), Nickel Cobalt Chromium Aluminum Yttrium (NiCoCrAlY), Yttria Stabilized Zirconia (YSZ) and Ceria Stabilized Zirconia (CSZ). The presently disclosed subject matter is not limited to any particular material to be used for the TBC 124. Depending on the particular TBC 124, the thickness of the TBC 124 can range from less than 100 μm to 3000 μm. Further, the manner in which the TBC 124 is applied may vary from spraying, spin coating, plasma deposition, and the like. The presently disclosed subject matter is not limited to any particular manner of applying (or bonding) the TBC 124.
To compensate for different rates of temperature change, the TBC 124 is applied to areas in which a lower rate of temperature change is desired. In the example illustrated in FIG. 1, it is desirable to reduce the rate at which the bridges 120 increase or decrease in temperature relative to the lobes 114. The TBC 124 applied to the portions of the bridges 120 illustrated in
For example, the insulative properties of the TBC 124A reduces the rate at which the bridge 120A heats and cools to a rate closer to the rate at which the lobe 114A heats and cools. The TBC 124A compensates the relatively lower heat capacity of the bridge 120A to be thermally similar to the lobe 114A. By modifying the thermal characteristics without making structural changes to the bridge 120A, the structural nature (such as strength, size, width, and the like) of the lobe 114A and the bridge 120A that are designed in a way to perform their respective functions during the operation of the engine are left unaltered.
Different temperatures in areas of a component can be caused by various reasons including, but not limited to, the location of the area of the component in relation to a heat source, the amount of mass of the area, and the like. As noted above, the TBC 124 may be deposited in various thicknesses, shapes, patterns, and the like to create desired thermal characteristics while maintaining the structural nature of the component. An example of using the TBC 124 to compensate for different masses of areas of the bowl 112 was illustrated in
As shown in
To reduce the different rates of temperature change, the valve area 212 and the valve area 216 can be modified using a TBC 218. As noted above with respect to
Thus, rather than being deposited as a single layer, potentially with varying thicknesses as illustrated in
In addition to using patterns of the TBC to adjust the thermal characteristics of a specific area, TBCs can be deposited in various patterns to achieve other benefits such as TBC crack control. Because TBCs are often formed from very strong but brittle alloys or ceramics, structural defects can occur in the TBCs themselves. These structural defects can result in cracks in the TBC material. As the TBCs are thermally cycled (i.e., heated up and cooled down), these cracks can propagate through the TBC. Other means may be used to control cracks including, but not limited to, concentric rings divided into parts (arcs) or other shapes broken into individual parts. However, using various patterns, the TBC can not only be used to provide the thermal characteristics desired for engine components, but also, provide structural advantages to the TBCs themselves, illustrated by way of example in
For example, if TBC coating 504A develops a crack 506, the distance between the TBC coating 504A and adjacent TBC coatings allows for the crack 506 to only affect and propagate through the TBC 504A rather than affect surrounding or adjacent TBC coatings, such as TBC coating 504C. If the TBC 502 were deposited as a single, monolithic layer, cracks and other structural defects occurring in one location of the TBC 502 can affect other locations of the TBC 502. However, using broken patterns, such as the dot matrix pattern of
At step 702, an engine component is identified for thermal characteristic modification. In
At step 704, a thermal map is created. A thermal map illustrates temperature differences across a surface.
At step 706, using the thermal map 800, a thermal barrier coating 124 is applied. The TBC 124 can be constructed from various materials including, but not limited to, ceramics or alloys such as Zirconia, Nickel Chromium Aluminum Yttrium (NiCrAlY), Nickel Cobalt Chromium Aluminum Yttrium (NiCoCrAlY), Yttria Stabilized Zirconia (YSZ), or Ceria Stabilized Zirconia (CSZ). The presently disclosed subject matter is not limited to any particular material to be used for the TBC 124. Depending on the particular TBC 124, the thickness of the TBC 124 can range from less than 100 μm to 3000 μm. Further, the manner in which the TBC 124 is applied may vary from spraying, spin coating, plasma deposition, and the like.
Further, the TBC can be applied using various patterns to isolate issues with the TBC to certain areas while providing the desired thermal characteristics. For example, the TBC 218 of
The systems and methods described herein, and variations thereof, provide a means to reduce the potential for structural issues in engine components by reducing or minimizing the magnitude of temperature changes across the components. During use, engine components can experience a significant rise and fall in the amount of heat applied to the component. This rise and fall of heat results in a temperature increase and decrease. Because engine components are often shaped with varying sizes, volumes, and areas within the component itself, rates of temperature change can be different. If the difference of the rate of change of temperature is significant enough between two proximate areas of the component, structural damage to the crystalline lattice of the component can occur.
Thermal barrier coatings are applied to surfaces of components to reduce or eliminate the probability of damage due to the heating and cooling of the component. When a component heats or cools, different areas of the component can heat up or cool down at different rates due to various heat capacities of the areas of the component. The different temperatures (and rates of temperature changes) results in different rates of expansion and contraction within the component itself. To reduce the differences of temperature within the component, a thermal barrier coating is applied. The thermal barrier coating acts as a thermal insulator. Due to its insulative properties, the thermal barrier coating reduces the rate of heat transfer into and out of the area to which the thermal barrier coating is applied. Thus, for an area that has a tendency to heat relatively quickly as compared to an area that tends to heat (or cool) relatively slower, the thermal barrier coating slows the rate of temperature increase to be closer to the slower heating (cooling) area, thus minimizing the difference of temperatures of the engine component. Minimizing the difference of temperatures within a component minimizes the differences in expansion and contraction within the component, reducing the potential for stress fractures caused by an uneven expansion of material. This can reduce failures of the component due to structural issues, thereby allowing the component to be used for a longer time.
Unless explicitly excluded, the use of the singular to describe a component, structure, or operation does not exclude the use of plural such components, structures, or operations or their equivalents. As used herein, the word “or” refers to any possible permutation of a set of items. For example, the phrase “A, B, or C” refers to at least one of A, B, C, or any combination thereof, such as any of: A; B; C; A and B; A and C; B and C; A, B, and C; or multiple of any item such as A and A; B, B, and C; A, A, B, C, and C; etc.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.
