Patent Application
20100055479
The present disclosure is directed to a combustion chamber defining component and, more particularly, to a coating for a combustion chamber defining component.
During engine combustion, high temperatures within the combustion chamber may develop. These temperatures may reach, for example, between about 300 and about 800 degrees Celsius. Combustion chamber defining components such as, for example, a flame deck of an engine cylinder head facing the combustion chamber, may be subjected to high thermal stresses from combustion. The high thermal stresses may lead to failures in the cylinder head due to thermal fatigue. Portions of the cylinder head particularly prone to thermal fatigue may be areas where hot spots develop such as, for example, a valve port bridge between an exhaust valve opening and an air intake valve opening. Hot spots may develop in these areas because the valve openings reduce the amount of cylinder head sectional area available to conduct and dissipate the heat from combustion.
One attempt at protecting combustion chamber defining components from thermal stresses is described in U.S. Pat. No. 4,495,907 (the '907 patent) issued to Kamo. The '907 patent discloses a layer of thermally insulative material bonded to a combustion chamber defining component via a bonding material and impregnated with a soluble chromium compound. A barrier layer comprised of silica, chromium, and aluminum may be applied to the thermally insulative material.
Although the applied layers of the '907 patent may provide a method for protecting a combustion chamber defining component, it may fail to adequately dissipate heat away from hot spots of the component. Also, thermally insulative layers may have limited durability at high temperatures and may therefore fail to protect combustion chamber defining components.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other deficiencies in the art.
In accordance with one aspect, the present disclosure is directed toward a method for coating a combustion chamber defining component. The method includes applying a thermally conductive layer to a surface of the combustion chamber defining component, the thermally conductive layer having a thermal conductivity greater than the combustion chamber defining component.
According to another aspect, the present disclosure is directed toward a method for coating a combustion chamber defining component. The method includes removing material from a substrate of the combustion chamber defining component and applying a thermally conductive layer to the substrate of the combustion chamber defining component, the thermally conductive layer having a thermal conductivity of between about 75 and about 450 Watt/meter*Kelvin. The method also includes applying an anti-oxidant layer to the thermally conductive layer.
As illustrated in
As illustrated in
First layer 160 may be a thermally conductive layer provided on at least a portion of substrate 155 and may have a thermal conductivity such as, for example, of between about 75 and about 450 Watt/meter*Kelvin, between about 150 and about 400 Watt/meter*Kelvin, or between about 200 and about 300 Watt/meter*Kelvin. First layer 160 may be applied at areas of cylinder head 115 prone to hot spots such as, for example, valve port bridge 150 of flame deck surface 138, and other portions of flame deck surface 138. First layer 160 may be made from highly thermally conductive materials such as, for example, copper, aluminum, boron nitride, or silicon carbide. When made from a copper material, first layer 160 may have a thermal conductivity such as, for example, of between about 125 and about 395 Watt/meter*Kelvin, between about 150 and about 350 Watt/meter*Kelvin, or between about 200 and about 300 Watt/meter*Kelvin. First layer 160, when made from a copper material, may have a greater thermal conductivity than substrate 155. When made from a copper material, first layer 160 may transfer heat from combustion temperatures of up to at least about 800° Celsius. When made from an aluminum material, first layer 160 may have a high thermal conductivity such as, for example, of between about 70 and about 223 Watt/meter*Kelvin, between about 100 and about 200 Watt/meter*Kelvin, or between about 125 and about 175 Watt/meter*Kelvin. First layer 160, when made from aluminum material, may have a greater thermal conductivity than substrate 155. When made from an aluminum material, first layer 160 may transfer heat from combustion temperatures of up to at least about 600° Celsius. When made from a boron nitride material, first layer 160 may have a high thermal conductivity such as, for example, of between about 15 and about 33 Watt/meter*Kelvin, or between about 20 and about 30 Watt/meter*Kelvin. When made from a silicon carbide material, first layer 160 may have a high thermal conductivity such as, for example, of between about 75 and about 120 Watt/meter*Kelvin, or between about 85 and about 110 Watt/meter*Kelvin. First layer 160 may have any suitable thickness such as, for example, between about 0.1 μm and about 3.0 mm.
Second layer 165 may be provided on at least a portion of first layer 160 as a protective sealing layer to reduce oxidation of first layer 160 to a negligible amount under ambient conditions and under combustion conditions. Second layer 165 may be made from an anti-oxidant material and may provide a barrier between oxidizing effects of combustion within combustion chamber 120 and first layer 160. Second layer 165 may be a made from a nickel-chromium-aluminum-yttrium (NiCrAlY) material. The NiCrAlY material may include between about 54% and about 83% nickel, between about 15% and about 30% chromium, between about 2% and about 14% aluminum, and about 2% or less Yttrium. It is contemplated that second layer 165 may also be a NiCrAl material that may not include Yttrium. Second layer 165 may also be made from stainless steel. When made from NiCrALY, NiCrAl, or stainless steel material, second layer 165 may have any suitable thickness such as, for example, between about 0.1 μm and about 3.0 mm. Second layer 165 may alternatively be made from a zirconia ceramic material and may have a low thermal conductivity such as, for example, of between about 0.5 and about 2.2 Watt/meter*Kelvin, or between about 1.0 and about 2.0 Watt/meter*Kelvin. When made from the zirconia material, second layer 165 may have any suitable thickness such as, for example, between about 0.1 μm and about 1.0 mm. It is also contemplated that first layer 160 may include NiCrALY, NiCrAl, stainless steel, and/or zirconia material to reduce oxidation.
Prior to conducting heat from combustion into substrate 155, first layer 160 may conduct the heat from restricted locations on cylinder head 115 having a reduced sectional area and thereby being prone to developing hot spots such as, for example, an interior location between openings 140 and/or 145. First layer 160 may conduct the heat from the restricted locations to unrestricted locations of cylinder head 115 having a greater sectional area that is unreduced by openings such as, for example, openings 140 and/or 145. For example, first layer 160 may conduct heat radially outward from valve port bridges 150 toward an outside edge of cylinder head 115. Heat transfer by first layer 160 may reduce the probability of hot spots developing on cylinder head 115. When second layer 165 is made from zirconia material, the zirconia material may act as an insulating layer to retain heat in cylinder head 115 and thereby additionally improving an efficiency of engine 100.
The disclosed coating may be used in any machine subject to thermal stresses such as, for example, a machine having an internal combustion engine. The disclosed coating may be used to coat any component prone to developing hot spots such as, for example, a combustion chamber defining component such as a cylinder head.
In step 185, first layer 160 may be applied to substrate 155 via any suitable method known in the art such as, for example, high velocity oxy-fuel (HVOF) thermal spraying using powder or wire arc thermal spraying. First layer 160 may also be applied via a cold spraying technique or a plating technique. In step 190, second layer 165 may be applied to first layer 160 using a similar technique as step 185. In step 195, coating 158 may be finished by milling or grinding surface 138 to meet surface finish requirements of cylinder head 115.
Prior to conducting heat from combustion into substrate 155, first layer 160 may transfer the heat away from locations on cylinder head 115 prone to developing hot spots, thereby reducing thermal stresses in substrate 155 of cylinder head 115. Second layer 165 may substantially reduce oxidation of first layer 160 from combustion. Coating 158 may thereby reduce thermal stresses from combustion within combustion chamber 120.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed coating. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed method and apparatus. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
