WO2017155519A1

WO2017155519A1 - Pistons and internal combustion engines incorporating the same

Info

Publication number: WO2017155519A1
Application number: PCT/US2016/021411
Authority: WO
Inventors: Joey A. MALFA; Jess A. MCFARLEN
Original assignee: Speed Of Air, Inc.
Priority date: 2016-03-08
Filing date: 2016-03-08
Publication date: 2017-09-14

Abstract

A piston for an internal combustion engine includes a piston skirt, a piston head having a crown on the piston skirt, and a series of gas release slots defined in the piston crown. The gas release slots extend radially outward from a central area of the crown toward an outer perimeter of the crown.

Description

PISTONS AND INTERNAL COMBUSTION ENGINES

INCORPORATING THE SAME

The present disclosure relates generally to pistons for internal combustion

BACKGROUND

[0002] Internal combustion engines are utilized in wide array of applications, including automobiles, agricultural vehicles, and maritime vehicles. Internal combustion engines typically include a cylinder block defining at least one cylinder, a piston configured to reciprocate in the cylinder, a cylinder head defining at least one intake port and at least one exhaust port, and a system to supply an air-fuel charge to a combustion chamber defined by the piston, the cylinder, and/or the cylinder head.

[0003] In conventional internal combustion engines, a flame front generated during the combustion stroke (i.e., the power stroke) may be prematurely extinguished (i.e., truncated). Truncation of the flame front may result in reduced power output, increased fuel consumption, and increased emissions. Depending on the fuel type, soot may build-up due to the incomplete combustion of the air-fuel charge. Additionally, in conventional internal combustion engines, the air-fuel charge may ignite and burn unevenly across the piston, which may also result in increased emissions due to the incomplete combustion of the air-fuel charge in the combustion chamber.

[0004] To mitigate the increased emission production caused by the incomplete combustion of the air-fuel charge in the combustion chamber, conventional internal combustion engines may incorporate one or more exhaust gas treatment components, such as catalytic converters, air injection systems, exhaust gas recirculation (EGR) systems, and/or selective catalytic reduction (SCR) systems. However, these exhaust gas treatment components may be costly to incorporate and/or maintain.

[0005] Additionally, during combustion in a conventional internal combustion engine, the flame front contacts the relatively cooler metal components defining the combustion chamber (e.g., the cylinder lining, the cylinder head, and the piston). -j These relatively cooler components reduce the temperature of the flame front, which slows the combustion event and may extinguish the flame front before all of the air- fuel charge is combusted, which increases emissions from the engine and the buildup of soot in the engine if the engine is a diesel engine.

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SUMMARY

[0006] The present disclosure is directed to various embodiments of a piston for an internal combustion engine. In one embodiment, the piston includes a piston skirt,

10 a piston head having a crown on the piston skirt, and a series of gas release slots defined in the crown of the piston head. The gas release slots extend radially outward from a central area of the crown toward an outer perimeter of the crown. The gas release slots may taper between a wider end proximal to the central area

^ and a narrower end distal to the central area and/or the gas release slots may taper between a deeper end proximal to the central area and a shallower end distal to the central area. The piston may include a combustion bowl defined in the crown of the piston head, and the gas release slots may be arranged circumferentially around a periphery of the combustion bowl. The combustion bowl may include at least one

20

sidewall, a base, and a cone extending up from the base. The piston may not include a combustion bowl (e.g., the piston may have a flat top or a raised dome configuration). The combustion bowl, the crown of the piston head, and/or the gas release slots may include a series of surface features. The surface features may be 25 projections, depressions, or combinations thereof. The surface features may have one or more prismatic shapes, one or more non-prismatic shapes, portions of such shapes, or combinations thereof. The piston may include a thermal barrier coating on at least a portion of the piston head.

[0007] The present disclosure is also directed to various embodiments of an internal combustion engine. The internal combustion engine may be any type of engine, such as a two-stroke engine or a four-stroke engine, and a combustion ignition engine (e.g., a diesel engine) or a spark ignition engine (e.g., a gasoline engine). In one embodiment, the internal combustion engine includes a cylinder ^ block defining at least one cylinder, a piston configured to reciprocate in the at least one cylinder, and a cylinder head coupled to the cylinder block defining an intake port and an exhaust port. The piston includes a piston skirt, a piston head having a crown, and series of gas release slots defined in the crown of the piston head. The gas release slots extend radially outward from a central area of the crown toward an outer perimeter of the crown. The piston may include a combustion bowl defined in the crown of the piston head, and the gas release slots may be arranged circumferentially around a periphery of the combustion bowl.

[0008] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features and advantages of embodiments of the present disclosure will become more apparent by reference to the following detailed description when considered in conjunction with the following drawings. In the drawings, like reference numerals are used throughout the figures to reference like features and components. The figures are not necessarily drawn to scale.

[0010] FIGS. 1A-1 B are a perspective view and a cross-sectional view of a piston according to one embodiment of the present disclosure;

[0011] FIGS. 2A-2B are a perspective view and a cross-sectional view of a piston according to another embodiment of the present disclosure; and

[0012] FIGS. 3A-3B are cross-sectional views of an internal combustion engine incorporating a piston according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

[0013] The present disclosure is directed to various embodiments of a piston for use in an internal combustion engine. The pistons of the present disclosure may be used in any type of internal combustion engine, including diesel engines, gasoline engines, natural gas engines, bio-fuel engines, methane gas engines, kerosene engines, and heavy fuel engines. The pistons of the present disclosure may be configured to be used in engines running on traditional hydrocarbons or biofuel. Additionally, the pistons of the present disclosure may be used in two-stroke or four- stroke internal combustion engines. Additionally, the pistons of the present disclosure may be used with compression ignition engines and spark ignition engines.

[0014] The pistons of the present disclosure include one or more surface features configured to promote increased combustion of the air-fuel charge in the combustion chamber by directing and accelerating the flame front radially outward across the crest of the piston during the combustion cycle. The pistons of the present disclosure may also include one or more surface features configured to induce the formation of a turbulent boundary layer on the piston that isolates the flame front from the relatively cooler piston to promote increased combustion of the air-fuel charge. Accordingly, the pistons of the present disclosure include one or more surface features that are configured to alter the flow dynamics of the flame front to increase combustion of the air-fuel charge in the combustion chamber compared to internal combustion engines using conventional pistons. Increasing the proportion of the air- fuel charge that is combusted increases power output, reduces fuel consumption, and reduces emissions, such as nitrogen oxides (NOx) (i.e., NO and NO2), carbon oxides (e.g., CO and CO2), hydrocarbons (e.g., HC and HCO), and other emissions. The one or more surfaces features on the pistons of the present disclosure are also configured to reduce the production and build-up of soot in the internal combustion engine, which is commonly due to the incomplete combustion of the air-fuel charge in the combustion chamber.

[0015] With reference now to FIGS. 1A-1 B, a piston 100 according to one embodiment of the present disclosure includes a skirt 101 and a piston head 102 having a crown 103 on an outer end of the skirt 101. In the illustrated embodiment, the piston head 102 includes a sidewall 104 defining a series of annular slots 105 that include piston ring grooves and optional oil control ring grooves that are configured to receive piston rings and an optional oil ring. The skirt 101 defines an opening 106 configured to receive a wrist pin connecting the piston 100 to a connecting rod. Although in the illustrated embodiment the crown 103 is planar or substantially planar, in one or more embodiments, the crown 103 may be non-planar (e.g., curved or sloped). Additionally, in the illustrated embodiment, the piston 100 defines a combustion bowl 107 extending down from the crown 103 of the piston head 102. In the illustrated embodiment, the combustion bowl 107 includes an annular sidewall 108, a base 109 recessed from the crown 103, a cone 110 extending from the base 109 toward the crown 103, and a curved wall 111 (e.g., a radius) connecting the base 109 to the annular sidewall 108. In one or more embodiments, the combustion bowl 107 may have any other shape suitable for the intended application of the piston 100, such as, for instance, the type of internal combustion engine (e.g., a gasoline engine) and/or the composition of the fuel used in the engine. Additionally, in one or more embodiments, the piston 100 may be provided without the combustion bowl 107.

[0016] In the illustrated embodiment, the piston 100 also defines a series of gas release slots, grooves, or channels 112 extending down from the crown 103 of the piston head 102. In the illustrated embodiment, the gas release slots 112 are circumferentially arranged around a periphery 113 of the combustion bowl 107. In the illustrated embodiment, the periphery 113 of the combustion bowl 107 is defined at an intersection or an interface between the annular sidewall 108 of the combustion bowl 107 and the crown 103 of the piston 100. Additionally, in the illustrated embodiment, the gas release slots 112 extend radially outward from the periphery 113 of the combustion bowl 107 toward an outer periphery 114 of the crown 103. In the illustrated embodiment, the outer periphery 114 of the crown 103 is defined at an intersection or an interface between the crown 103 and the sidewall 104 of the piston head 102. Although in the illustrated embodiment the piston 100 includes ten gas release slots 112, in one or more embodiments, the piston 100 may include any other number of gas release slots 112 suitable for the intended application of the piston 100, such as, for instance, from two to twenty gas release slots 112. In the illustrated embodiment, each of the gas release slots 112 tapers between a wider end 115 proximal to the periphery 113 of the combustion bowl 107 and a narrower end 116 distal to the periphery 113 of the combustion bowl 107 (e.g., the narrower ends of the gas release slots 112 are proximal to the outer periphery 114 of the crown 103). Although in the illustrated embodiment the gas release slots 112 taper linearly, in one or more embodiments, the gas release slots 112 may taper non- linearly between the wider and narrower ends 115, 116. In one embodiment, the narrower ends 116 of the gas release slots 112 have a width from approximately 0.25mm to approximately 0.75mm (e.g., approximately 0.5mm) and the wider ends 115 of the gas release slots 112 have a width from approximately 10mm to approximately 20mm (e.g., approximately 15mm). Additionally, in the illustrated -j embodiment, each of the gas release slots 112 tapers between a deeper end 117 proximal to the periphery 113 of the combustion bowl 107 and a shallower end 118 distal to the periphery 113 of the combustion bowl 107 (e.g., the shallower ends 118 of the gas release slots 112 are proximal to the outer periphery 114 of the crown

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103). Accordingly, in the illustrated embodiment, each of the gas release slots 112 tapers between a wider and deeper end 115, 117 proximal to the periphery 113 of the combustion bowl 107 and a narrower and shallower end 116, 118 distal to the periphery 113 of the combustion bowl 107. In one embodiment, the deeper ends 117 10 of the gas release slots 112 have a depth from approximately 8mm to approximately 16mm (e.g., approximately 12mm) and the shallower ends 118 of the gas release slots 112 have a depth from approximately 0mm to approximately 0.5mm (e.g., 0.25mm). In one or more embodiments, the gas release slots 112 may not taper between the wider and narrower ends 115, 116 (e.g., the gas release slots 112 may

15

have a constant or substantially constant width) and/or the gas release slots 112 may not taper between deeper and shallower ends 117, 118 (e.g., the gas release slots 112 may have a constant or substantially constant depth). Additionally, although in the illustrated embodiment the gas release slots 112 are uniformly or on

substantially uniformly spaced around the periphery 113 of the combustion bowl 107, in one or more embodiments, the gas release slots 112 may be non-uniformly spaced around the periphery 113 of the combustion bowl 107. Furthermore, although in the illustrated embodiment the gas release slots 112 extend radially outward on

25 the crown 103 of the piston 100, in one or more embodiments, the gas release slots

112 may have any other suitable configuration. For instance, in one or more embodiments, the gas release slots 112 may extend spirally or helically outward on the crown 103 of the piston 100 toward the outer periphery 114 of the crown 103.

^ [0017] Additionally, in the illustrated embodiment the gas release slots 112 have a curved (e.g., rounded) cross-sectional shape. In one or more embodiments, the gas release slots 112 may have any other suitable cross-sectional shape, such as, for instance, an angular (e.g., chamfered) cross-sectional shape. In the illustrated embodiment, the narrower and shallower distal ends 116, 118 of the gas release

35 slots 112 are spaced apart from the outer periphery 114 of the crown 103 (i.e., the gas release slots 112 do not extend entirely to the outer periphery 114 of the crown -j 103). In one or more embodiments, the gas release slots 112 may extend completely to the outer periphery 114 of the crown 103.

[0018] In one or more embodiments in which the piston 100 does not include the combustion bowl 107, the series of gas release slots 112 may extend radially

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outward from a central area or region of the crown 103 toward the outer periphery 114 of crown 103. In one or more embodiments, the central area of the crown 103 may encompass a center point of the crown 103 defined at an intersection between a longitudinal axis L of the piston 100 and the crown 103. In one or more 10 embodiments the central area may not be centered on the crown 103 such that the gas release slots 112 are not centered on the crown 103. In one or more embodiments, the gas release slots 112 may extend radially outward from a common point on the crown 103 (e.g., the gas release slots 112 may extend radially outward from a central point on the crown 103).

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[0019] The configuration of the gas release slots 112 (e.g., the size, shape, and arrangement of the gas release slots 112) and/or the number of gas release slots 112 may vary depending on a variety of factors, including the size of the piston 100 and the type of fuel used in the internal combustion engine in which the piston 100 is on

operated.

[0020] When the piston 100 according to one embodiment of the present disclosure is operated in an internal combustion engine (e.g., a diesel engine), an air-fuel charge in the combustion chamber is ignited during the combustion stroke

25 (i.e., the power stroke). During the combustion stroke, the flame front of the ignited air-fuel charge expands. The flame front is the boundary or interface between the combusted air-fuel charged and the unignited air-fuel charge in the combustion chamber. The gas release slots 112 are configured to direct and accelerate the

^ flame front radially outward across the crown 103 the piston 100. For instance, in the illustrated embodiment, the gas release slots 112 are configured to direct and accelerate the flame front from the combustion bowl 107 in the piston 100 radially outward along the crown 103 of the piston 100 towards the outer periphery 114 of the crown 103. In one or more embodiments in which the piston 100 does not

35 include the combustion bowl 107, the gas release slots 112 are configured to direct and accelerate the flame front from a central area of the crown 103 of the piston 100 radially outward toward the outer periphery 114 of the crown 103. Directing and accelerating the flame front radially outward across the crown 103 of the piston 100 is configured to combust a greater proportion of the air-fuel charge in the combustion chamber compared to an otherwise comparable internal combustion engine incorporating a piston without gas release slots. Combusting a greater proportion of the air-fuel charge in the combustion chamber increases the power output of the internal combustion engine and reduces fuel consumption, emissions (e.g., NOx, carbon oxides, and hydrocarbons), and soot production, which are caused by an unignited air-fuel charge remaining in the combustion chamber following the combustion stroke.

[0021] Still referring to the embodiment illustrated in FIGS. 1A-1 B, the piston 100 includes a series of surface features 119. The surface features 119 are configured to work in conjunction with the gas release slots 112 to prevent the premature extinction (i.e., truncation) of the flame front and thereby increase the proportion of the air-fuel charge in the combustion chamber that is combusted during the combustion stroke. Although not being bound by a particular theory, it is believed that the surface features 119 function as turbulators that induce the formation of a thin turbulent boundary layer over at least a portion of the piston 100 as the flame front flows over the surface features 119. The thin boundary layer on the piston 100 (or a portion thereof) insulates the flame front from the relatively cooler piston 100 (or portions thereof), which might otherwise slow the combustion of the air-fuel charge and/or prematurely extinguish (i.e., truncate) the flame front. For instance, direct contact between the flame front and one or more surfaces of the relatively cooler piston 100 may extinguish the flame front prior to the combustion of all or substantially all of the air-fuel charge in the combustion chamber. Accordingly, during each combustion stroke of the piston 100, the flame front is spaced apart from the piston 100 by a gap corresponding to the thickness of the turbulent boundary layer (e.g., the flame front progresses slightly above the relatively cooler surfaces of the piston 100). In this manner, the surface features 119 are configured to prevent or at least mitigate a reduction in the temperature of the flame front and/or a deceleration in the rate at which the flame front is expanding or propagating, which might otherwise be caused by direct contact between the flame front and the relatively cooler surfaces of the piston 100. In this manner, the surface features 119 are configured to increase the proportion of the air-fuel charge combusted during the combustion stroke compared to an otherwise comparable piston without the surface features, which increases the power output of the internal combustion engine incorporating the piston 100 and reduces the fuel consumption, the soot production, and the emissions of the internal combustion engine.

[0022] The surface features 119 may be provided on the crown 103 (or a portion thereof), the combustion bowl 107 (or a portion thereof), the gas release slots 112 (or a portion thereof), or combinations thereof. In the illustrated embodiment, the surface features 119 are provided on the annular sidewall 108, the base 109, the curved wall 111 , and the cone 110 of the combustion bowl 107. Accordingly, in the illustrated embodiment, the surface features 119 are on each surface or feature of the combustion bowl 107. In one or more embodiments, the surface features 119 may be provided on only a portion of the combustion bowl 107. Additionally, in the illustrated embodiment, the surface features 119 are provided on the crown 103 of the piston head 102. The surface features 119 may be a series of discrete protuberances (e.g., projections), a series of discrete depressions (e.g., indentations), or combinations thereof. In the illustrated embodiment, the surface features 119 are hemi- or semi-spherical depressions (e.g., dimples). In one or more embodiments, the surface features 119 may have any other suitable shape or combination of shapes, such as, for instance, one or more prismatic shapes (e.g., polyhedral shapes, such as pyramidal shapes), one or more non-prismatic shapes (e.g., conical shapes, frusto-conical shapes, semi-ellipsoidal shapes, and/or cylindrical shapes), or portions of such shapes. The surface features 119 may have any suitable size, such as, for instance, an average depth or height from approximately 1/4mm to approximately 7mm. In one or more embodiments, the surface features 119 have an average width (e.g., an average diameter) from approximately 1/2mm to approximately 12mm or more. In one embodiment, the surface features 119 have an average width (e.g., an average diameter) from approximately 1.5mm to approximately 9.5mm. Additionally, in one or more embodiments, edges of adjacent surface features 119 may be spaced apart from each other by any suitable distance, such as, for instance, by an average distance from approximately 3mm to approximately 7mm. Additionally, in the illustrated embodiment, the surface features 119 are arranged in a matrix-like pattern (e.g., an aligned grid pattern). In one or more embodiments, the surface features 119 may be arranged in any other suitable pattern, such as, for instance, an offset or staggered grid pattern, a spiral pattern, or combination thereof. In one or more embodiments, the surfaces features 119 (or at least some of the surface features 119) may have an irregular arrangement.

[0023] The configuration of the surface features 119 (e.g., the size, shape, spacing, and arrangement of the surface features 119) and/or the number surface features 119 may vary depending on a variety of factors, including, for instance, the size of the piston 100, the type of fuel used in the internal combustion engine in which the piston 100 is operated, the size of the combustion chamber, and the type of fuel delivery system used in the internal combustion engine. Additionally, the configuration of the surface features 119 (e.g., the size, shape, spacing, and arrangement of the surface features 119) may vary depending on the location of the surface features 119 on the piston 100. For example, in one or more embodiments, the configuration of the surface features 119 in the combustion bowl 107 may be different than the configuration of the surface features 119 on the crown 103 of the piston head 102. Additionally, in one or more embodiments, the piston 100 may be provided without the surface features 119.

[0024] The gas release slots 112 and the surface features 119 may be formed in the piston 100 by any suitable manufacturing process or technique, such as, for instance, by machining, casting, etching, or combinations thereof. Additionally, the gas release slots 112 and the surface features 119 may be formed in the piston 100 during the fabrication of the piston 100 or subsequent to the fabrication of the piston 100. For instance, a piston may be retrofitted to include the gas release slots 112 and/or the surface features 119.

[0025] In one or more embodiments, the piston 100 (or a portion thereof) may be coated with a thermal barrier coating. The thermal barrier coating is configured to thermally insulate the piston 100 (or a portion thereof) to reduce heat transfer from the flame front to the piston 100. Otherwise, heat transfer from the flame front to the piston 100 could sufficiently cool and/or decelerate the flame front to cause premature extinction of the flame front. In this manner, the thermal barrier coating on the piston 100 (or a portion thereof) is configured to increase the proportion of the air-fuel charge that is combusted during the combustion stroke. As described above, the increased combustion of the air-fuel charge increases power output and reduces fuel consumption, emissions, and the production of soot. The thermal barrier coating may include any suitable thermally insulating material or materials, such as, for instance, an aluminum-filled ceramic.

[0026] The embodiment of the piston 100 illustrated in FIGS. 1A-1 B may be particularly suitable for use in a diesel engine, although a person of ordinary skill in the art would appreciate that modifications to the piston 100 (e.g., modifications to the configuration of the combustion bowl 107) may render the piston 100 suitable in any other type of internal combustion engine (e.g., a gasoline or gaseous fuel engine).

[0027] With reference now to FIGS. 2A-2B, a piston 200 according to another embodiment of the present disclosure includes a skirt 201 and a piston head 202 having a crown 203 on an outer end of the skirt 201. The embodiment of the piston 200 illustrated in FIGS. 2A-2B is similar to the embodiment of the piston 100 illustrated in FIGS. 1A-1 B except for the configuration of the combustion bowl and the configuration of the gas release slots. In the illustrated embodiment, the piston 200 defines a combustion bowl 204 extending down from the crown 203 of the piston head 202 that includes an annular sidewall 205, a base 206, and a curved wall 207 (e.g., a radius) connecting the base 206 to the annular sidewall 205. Accordingly, unlike the embodiment of the piston 100 illustrated in FIGS. 1A-1 B, the combustion bowl 204 in the embodiment of the piston 200 illustrated in FIGS. 2A-2B is provided without a cone.

[0028] Additionally, in the illustrated embodiment, the piston 200 includes a series of gas release slots, grooves, or channels 208 extending down from the crown 203 of the piston head 202. In the illustrated embodiment, the gas release slots 208 are circumferentially arranged around a periphery 209 of the combustion bowl 204 and extend radially outward from the periphery 209 of the combustion bowl 204 toward an outer periphery 210 of the crown 203. The gas release slots 208 are configured to direct and accelerate a flame front radially outward across the crown 203 when then piston 200 is incorporated into an internal combustion engine to increase the proportion of the air-fuel charge that is combusted during each combustion stroke and thereby increase the power output of the engine and reduce fuel consumption, emissions, and the production of soot. Although in the illustrated embodiment the piston 200 includes eight gas release slots 208, in one or more embodiments the piston 200 may include any other suitable number of gas release slots 208, such as, for instance, from two to twenty gas release slots 208. Additionally, in the illustrated embodiment, each of the gas release slots 208 tapers between a wider and deeper end 211 proximal to the periphery 209 of the combustion bowl 204 and a narrower and shallower end 212 distal to the periphery 209 of the combustion bowl 204. The gas release slots 208 may have any suitable cross-sectional shape, such as, for instance, a curved (e.g., rounded) cross-sectional shape and/or an angular (e.g., chamfered) cross-sectional shape. In one or more embodiments, the gas release slots 208 may have a constant or substantially constant width and/or the gas release slots 208 may have a constant or substantially constant depth. Additionally, although in the illustrated embodiment the narrower and shallower ends 212 of the gas release slots 208 are spaced apart from the outer periphery 210 of the crown 203, in one or more embodiments, the gas release slots 208 may extend completely to the outer periphery 210 of the crown 203.

[0029] Additionally, in one or more embodiments, the piston 210 may include surface features 213 on the crown 203 (or a portion thereof), the combustion bowl 204 (or a portion thereof), or the gas release slots 208 (or a portion thereof), or combinations thereof. In the embodiment illustrated in FIGS. 2A-2B, the surface features 213 are provided on the combustion bowl 204 and the crown 203 of the piston head 202. As described in more detail above, it is believed that the surface features 213 create a boundary layer over at least a portion of the piston 200 as the flame front flows over the surface features 213 and that the boundary layer insulates the flame front from the relatively cooler piston 200 (or portions thereof), which might otherwise slow the combustion of the air-fuel charge and/or prematurely extinguish (i.e., truncate) the flame front. The configuration of the surface features 213 (e.g., the size, shape, spacing, and arrangement of the surface features) and/or the number surface features 213 may vary depending on a variety of factors, including, for instance, the size of the piston 200, the type of fuel used in the internal combustion engine in which the piston 200 is operated, the size of the combustion chamber, and the type of fuel delivery system used in the internal combustion engine. For instance, in one or more embodiments, the surface features 200 may have one or more prismatic shapes (e.g., polyhedral shapes, such as pyramidal shapes), one or more non-prismatic shapes (e.g., conical shapes, frusto-conical shapes, hemi- or semi- spherical shapes, such as dimples, semi-ellipsoidal shapes, and/or cylindrical shapes), or portions of such shapes. Additionally, the configuration of the surface features 213 (e.g., the size, shape, spacing, and arrangement of the surface features 213) may vary depending on the location of the surface features 213 on the piston 200. In one or more embodiments, the configuration of the surface features 213 may be the same or similar to the configuration of the surface features 119 described above with reference to the embodiment of the piston 100 illustrated in FIGS. 1A-1 B. In one or more embodiments, the piston 200 may be provided without the surface features 213.

[0030] In one or more embodiments, the piston 200 (or a portion thereof) may be coated with a thermal barrier coating (e.g., an aluminum-filled ceramic) to reduce heat transfer from the flame front to the piston 200, which might otherwise sufficiently cool and/or decelerate the flame front to cause premature extinction of the flame front. In this manner, the thermal barrier coating on the piston 200 (or a portion thereof) is configured to increase the proportion of the air-fuel charge that is combusted during the combustion stroke and thereby increase power output and reduce fuel consumption, emissions, and the production of soot.

[0031] The embodiment of the piston 200 illustrated in FIGS. 2A-2B may be particularly suitable for use in a gasoline engine, although a person of ordinary skill in the art would appreciate that modifications to the piston 200 (e.g., modifications to the configuration of the combustion bowl 204) may render the piston 200 suitable in any other type of internal combustion engine (e.g., a diesel or gaseous fueled engine). Additionally, in one or more embodiments, the piston 200 may be provided without the combustion bowl 204 (e.g., the piston 200 may be a flat top or domed piston).

[0032] FIGS. 3A-3B illustrate an internal combustion engine 300 according to one embodiment of the present disclosure. In the illustrated embodiment, the internal combustion engine 300 is a four-stroke diesel engine including a cylinder block 301 defining at least one cylinder 302, a piston 303 configured to reciprocate in the cylinder 302, a cylinder head 304 coupled to the cylinder block 301 defining an intake port 305 and an exhaust port 306, an intake valve 307 received in the intake port 305, an exhaust valve 308 received in the exhaust port 306, and a diesel fuel injector 309 coupled to the cylinder head 304. The internal combustion engine 300 -j also includes a connecting rod 310 having one end pivotally coupled to the piston 303 by a wrist pin 311 and an opposite end rotatably coupled to a crank shaft.

[0033] The intake valve 307 and the exhaust valve 308 each include a head 312, 313 and a shaft 314, 315 extending from the head 312, 313, respectively. The shafts

5

314, 315 of the intake valve 307 and the exhaust valve 308 are received within valve guides 316, 317, respectively, coupled to the cylinder head 304. The shafts 314, 315 are configured to slide within the valve guides 316, 317, respectively, as the intake valve 307 and the exhaust valve 308 reciprocate between open and closed 10 positions. The internal combustion engine 300 also includes a cam shaft configured to drive the valves 307, 308 and control the timing of the opening and closing of each valve 307, 308. Although in the illustrated embodiment the cylinder head 304 includes a single intake port 305 and a single exhaust port 306 for the cylinder 302, in one or more alternate embodiments, the cylinder head 304 may define a plurality of exhaust ports and/or a plurality of intake ports for each cylinder of the internal combustion engine 300. The internal combustion engine 300 also includes an intake manifold for supplying air to the combustion chamber through the one or more intake ports 305 and an exhaust manifold for drawing exhaust gas from the combustion on

chamber through the one or more exhaust ports 306. Additionally, in one or more embodiments, the internal combustion engine 300 may include multiple intake valves and/or multiple exhaust valves for each cylinder 302.

[0034] In the embodiment illustrated in FIGS. 3A-3B, the piston 303 includes a 25 skirt 318 and a piston head 319 having a crown 320 on an outer end of the skirt 318.

Additionally, in the illustrated embodiment, the piston 303 defines a combustion bowl 321 extending down from the crown 320 of the piston head 319. In the illustrated embodiment, the combustion bowl 321 includes an annular sidewall 322, a base 323, a cone 324 extending from the base 323, and a curved wall 325 (e.g., a radius)

30

connecting the base 323 to the annular sidewall 322.

[0035] Additionally, in the illustrated embodiment, the piston 303 includes a series of gas release slots, grooves, or channels 326 extending down from the crown 320 of the piston head 319. In the illustrated embodiment, the gas release slots 326 are 35 arranged circumferentially around a periphery 327 of the combustion bowl 321. The gas release slots 326 extend radially outward from the periphery 327 of the combustion bowl 321 toward an outer periphery 328 of the crown 320. Although in -j the illustrated embodiment the piston 303 includes eight gas release slots 326, in one or more embodiments the piston 303 may include any other suitable number of gas release slots 326, such as, for instance, from two to twenty gas release slots 326. Additionally, in the illustrated embodiment, each of the gas release slots 326

5

tapers between a wider and deeper end 329 proximal to the periphery 327 of the combustion bowl 321 and a narrower and shallower end 330 distal to the periphery 327 of the combustion bowl 321. In one or more embodiments, the configuration of the gas release slots 326 may be the same or similar to the gas release slots 112 10 described above with reference to the embodiment of the piston 100 illustrated in FIGS. 1A-1 B.

[0036] Additionally, in one or more embodiments, the piston 303 may include surface features 331 on the crown 320 (or a portion thereof), the combustion bowl 321 (or a portion thereof), or the gas release slots 326 (or a portion thereof), or

15

combinations thereof. In the embodiment illustrated in FIGS. 3A-3B, the surface features 331 are provided on the combustion bowl 321 and the crown 320 of the piston 303. The configuration of the surface features 331 (e.g., the size, shape, spacing, and arrangement of the surface features) and/or the number surface on

features 331 may vary depending on a variety of factors, including, for instance, the size of the piston 303, the type of fuel used in the internal combustion engine in which the piston 303 is operated, the size of the combustion chamber, and the type of fuel delivery system used in the internal combustion engine. For instance, in one 25 or more embodiments, the surface features 331 may have one or more prismatic shapes (e.g., polyhedral shapes, such as pyramidal shapes), one or more non- prismatic shapes (e.g., conical shapes, frusto-conical shapes, hemi- or semi- spherical shapes, such as dimples, semi-ellipsoidal shapes, and/or cylindrical shapes), or portions of such shapes. Additionally, the configuration of the surface

30

features 331 (e.g., the size, shape, spacing, and arrangement of the surface features) may vary depending on the location of the surface features on the piston 303. In one or more embodiments, the configuration of the surface features 331 may be the same or similar to the configuration of the surface features 119 described 35 above with reference to the embodiment of the piston 100 illustrated in FIGS. 1A-1 B.

In one or more embodiments, the piston 303 may be provided without the surface features 331. [0037] In one or more embodiments, the piston 303 (or a portion thereof) may be coated with a thermal barrier coating (e.g., an aluminum-filled ceramic) to reduce heat transfer from the flame front to the piston 303, which might otherwise sufficiently cool and/or decelerate the flame front to cause premature extinction of the flame front. In this manner, the thermal barrier coating on the piston 303 (or a portion thereof) is configured to increase the proportion of the air-fuel charge that is combusted during the combustion stroke and thereby increase power output and reduce fuel consumption, emissions, and the production of soot.

[0038] In operation, the piston 303 is configured to reciprocate (arrow 332) within the cylinder 302 between an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. During the intake stroke, piston 303 moves down within the cylinder 302 from a top dead center position to a bottom dead center position, the cam moves the intake valve 307 into an open position to permit air to flow through the intake port 305 into the combustion chamber, and the diesel fuel injector 309 injects diesel fuel into the combustion chamber to create an air-fuel charge in the combustion chamber. During the compression stroke, the piston 303 moves within the cylinder from the bottom dead center position back to the top dead center position and thereby compresses the air-fuel charge. In the illustrated embodiment, the internal combustion engine 300 is a compression ignition engine such that the air-fuel charge is combusted by the increased temperature and pressure caused by the compression of the air-fuel charge. During the combustion stroke (i.e., the power stroke), the air-fuel charge is ignited and a flame front begins to expand within the combustion chamber, which forces the piston 303 down into the bottom dead center position. In the illustrated embodiment, the gas release slots 326 are configured to direct and accelerate the flame front from the combustion bowl 321 in the piston 303 radially outward across the crown 320 of the piston 303 toward the outer periphery 328 of the crown 320. Directing and accelerating the flame front radially outward across the crown 320 of the piston 303 is configured to combust a greater proportion of the air-fuel charge in the combustion chamber compared to an otherwise comparable internal combustion engine incorporating a piston without gas release slots. Combusting a greater proportion of the air-fuel charge in the combustion chamber increases the power output of the internal combustion engine 300 and reduces fuel consumption, emissions (e.g., NOx, carbon oxides, and hydrocarbons), and soot production, which are caused by an unignited air-fuel charge remaining in the combustion chamber following the combustion stroke. Additionally, the expansion of the flame front during the combustion stroke forms a boundary layer over at least a portion of the piston 303 as the flame front flows over the surface features 331. The boundary layer insulates the flame front from the relatively cooler piston 303 (or portions thereof), which might otherwise slow the combustion of the air-fuel charge and/or prematurely extinguish (i.e., truncate) the flame front. In this manner, the surface features 331 promote the combustion of a greater proportion of the air-fuel charge, which increases the power output of the internal combustion engine 300 and reduces fuel consumption, emissions (e.g., NOx, carbon oxides, and hydrocarbons), and soot production. During the exhaust stroke, the cam moves the exhaust valve 308 into an open position and the piston 303 moves up in the cylinder 302 into the top dead center position and thereby expels the exhaust gases out through the exhaust port 306.

[0039] Although the embodiment of the internal combustion engine 300 illustrated in FIGS. 3A-3B is a four-stroke diesel engine, in one or more embodiments the internal combustion engine 300 may by any other suitable type of engine, such as, for instance, a two- or four- stroke gasoline engine or a two-stroke diesel engine. The internal combustion engines of the present disclosure may be compression ignition engines or spark ignition engines. In one or more embodiments in which the internal combustion engine 300 is a two-stroke engine, the internal combustion engine 300 is provided without the intake valve 307 and the exhaust valve 308. Although in the illustrated embodiment the internal combustion engine 300 is a compression ignition engine, in one or more embodiments the internal combustion engine 300 may be a spark ignition engine and the internal combustion engine 300 may be provided with a spark plug to provide an ignition source to ignite the air-fuel mixture during the combustion stroke of the piston 303. Additionally, in one or more embodiments in which the internal combustion engine 300 is gasoline engine, the diesel fuel injector 309 is replaced by a fuel supplier (e.g., one or more fuel injectors or one or more carburetors) for supplying fuel to the combustion chamber. In one or more embodiments, the internal combustion chamber 300 may also include one or more air pressure boosters (e.g., a turbocharger or a supercharger) configured to increase the volume and pressure of the air supplied to the combustion chamber. The internal combustion engine 300 may be configured for use with any type of fuel, such as, for instance, gasoline, diesel, natural gas, bio-fuels, methane, and kerosene.

[0040] A person of ordinary skill in the art will appreciate that certain modifications may be made to the piston 303 to achieve its suitability for use with a particular type of engine. For instance, the shape of the combustion bowl 321 may vary depending on the type of engine in which the piston 303 is incorporated. In one or more embodiments in which the internal combustion engine 300 is a gasoline engine, the piston 303 may be the same as or similar to the embodiment of the piston 200 illustrated in FIGS. 2A-2B (e.g., the combustion bowl in the piston may be provided without the cone). Additionally, in one or more embodiments, the piston 303 may be provided without the combustion bowl 321. Accordingly, unlike the embodiment illustrated in FIGS. 3A-3B in which the combustion chamber is defined by the combustion bowl 321 in the piston 303, in one or more embodiments, the combustion chamber may be defined between the crown 320 of the piston 303, an inner wall of the cylinder 302, and an inner surface of the cylinder head 304.

While this invention has been described in detail with particular references to embodiments thereof, the embodiments described herein are not intended to be exhaustive or to limit the scope of the invention to the exact forms disclosed. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of assembly and operation can be practiced without meaningfully departing from the principles, spirit, and scope of this invention. One or more of the features described with reference to one embodiment may be combined with one or more other features described with reference to one or more other embodiments to provide a workable device. Although relative terms such as "outer," "inner," "upper," "lower," and similar terms have been used herein to describe a spatial relationship of one element to another, it is understood that these terms are intended to encompass different orientations of the various elements and components of the invention in addition to the orientation depicted in the figures. Additionally, as used herein, the term "substantially" and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Furthermore, as used herein, when a component is referred to as being "on" or "coupled to" another component, it can be directly on or attached to the other component or intervening components may be present therebetween. Further, any described feature is optional and may be used in combination with one or more other features to achieve one or more benefits.

Claims

WHAT IS CLAIMED IS:

1. A piston for an internal combustion engine, comprising:

a piston skirt;

a piston head having a crown on the piston skirt; and

a plurality of gas release slots defined in the crown of the piston head extending radially outward from a central area of the crown toward an outer perimeter of the crown. 0

2. The piston of claim 1 , wherein each gas release slot of the plurality of gas release slots tapers between a wider end proximal to the central area and a narrower end distal to the central area. 5

3. The piston of claim 2, wherein each gas release slot has a width varying from approximately 1/2mm at the narrower end to approximately 15mm at the wider end.

4. The piston of claim 1 , wherein each gas release slot of the plurality of gas0 release slots tapers between a deeper end proximal to the central area and a

shallower end distal to the central area.

5. The piston of claim 4, wherein each gas release slot has a depth varying fromj- approximately 1/4mm at the shallower end to approximately 12mm at the deeper end.

6. The piston of claim 1 , wherein each gas release slot has an average width from approximately 2.5mm to approximately 15mm and an average depth from0

approximately 3.5mm to approximately 5.5mm.

7. The piston of claim 1 , wherein each gas release slot has a curved cross- sectional shape.

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8. The piston of claim 1 , further comprising a combustion bowl defined in the crown of the piston head, and wherein the gas release slots are arranged

circumferentially around a periphery of the combustion bowl.

9. The piston of claim 8, wherein the combustion bowl comprises at least one sidewall, a base, and a cone extending up from the base.

10. The piston of claim 8, wherein the combustion bowl comprises a plurality of surface features.

1 1. The piston of claim 1 , wherein at least one of the crown or the plurality of gas release slots comprises a plurality of surface features.

12. The piston of claim 11 , wherein the surface features are selected from the group consisting of projections, depressions, and combinations thereof.

13. The piston of claim 11 , wherein the surface features have a shape selected from the group consisting of dimples, prismatic shapes, conical shapes, portions of such shapes, and combinations thereof.

14. The piston of claim 1 , further comprising a thermal barrier coating on at least a portion of the piston head.

15. An internal combustion engine, comprising:

a cylinder block defining at least one cylinder;

a piston configured to reciprocate in the at least one cylinder, the piston comprising a piston skirt, a piston head having a crown on the piston skirt, and plurality of gas release slots defined in the crown of the piston head extending radially outward from a central area of the crown toward an outer perimeter of the crown; and

a cylinder head coupled to the cylinder block defining an intake port and an exhaust port.

16. The internal combustion engine of claim 15, wherein the piston further comprises a combustion bowl defined in the crown of the piston head, and wherein -j the gas release slots are arranged circumferentially around a periphery of the combustion bowl.

17. The internal combustion engine of claim 15, wherein the internal combustion

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engine is a two-stroke engine or a four-stroke engine.

18. The internal combustion engine of claim 15, wherein the internal combustion engine is a diesel engine.

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19. The internal combustion engine of claim 18, further comprising a diesel fuel injector coupled to the cylinder head.

20. The internal combustion engine of claim 15, wherein the internal combustion engine is a gasoline engine.

21. The internal combustion engine of claim 15, further comprising an intake valve in the intake port and an exhaust valve in the exhaust port.

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