Piston with combustion stabilizing bowl

Abstract

A piston for an engine may include an annular body including a combustion bowl defining a volume and surrounded at a top side thereof by an annular crown portion defining a top compression surface having an inner edge defining an inlet opening to the combustion bowl. The opening may include an area for combustion gases to enter the bowl during a compression stroke of the piston. The combustion bowl may include a recessed surface that defines a tangent that forms a recessed angle with the top pressing surface. The recessed angle may be in the range of 28.0 degrees to 32.0 degrees. The ratio of the bowl volume to the area of the inlet opening may be in the range of 45 mm to 52 mm. The ratio of bowl volume to the recessed angle may be in the range of 12 cc / deg to 15 cc / deg.

Description

Technical Field

[0001] The present disclosure generally relates to pistons having a contoured bowl geometry with a concave surface for use in internal combustion engines. More particularly, the present disclosure relates to pistons having a contoured bowl geometry with a concave surface that can improve combustion stability in low-compression natural gas engines. Background Art

[0002] Internal combustion engines are used throughout the world for a wide range of applications, from vehicle propulsion to pump and compressor operation to power generation. A typical internal combustion engine employs multiple pistons that reciprocate within cylinder bores in response to a controlled combustion reaction that causes a rapid increase in pressure and temperature, rotating a crankshaft to drive the pistons. For decades, engineers have experimented with a wide variety of fuels, exhaust treatment devices and technologies, and operating strategies in an effort to improve engine operation, reliability, and performance.

[0003] In recent years, significant engineering resources have been devoted to developing pistons optimized for various applications. Depending on the engine type, the piston may be formed with a specified combustion face geometry that is designed to interact with the flow of fuel, air, and / or exhaust gas during operation to achieve various objectives, including optimizing emissions and / or efficiency, mitigating or otherwise controlling in-cylinder temperature and / or mechanical wear or corrosion, and various other objectives. It has been observed that seemingly very small changes in piston geometry can often have an outsized effect on engine operation and performance, and the results of switching any one variable regarding piston geometry are often quite unpredictable. Furthermore, exacerbating the difficulty of optimizing piston design, particularly in the combustion face, the addition or removal of piston volume affects the geometric compression ratio, which often requires other modifications to the piston or the entire engine and supporting system design to maintain the compression ratio at the desired level. Depending on the fuel type and many different operating parameters, as well as different engine applications, the optimized piston design can have a wide variety of geometries.

[0004] Indian Published Patent Application No. 201621045122A (the '122 patent application) discloses a piston having a recessed combustion chamber on the piston head for increasing the combustion rate. The piston may also include the recessed combustion chamber facing the cylinder head having an injector. The injector is a fuel injector for introducing fuel into the combustion chamber, where a mixture of fuel and air is allowed to burn. The internal structural design of the combustion chamber can be formed into a circular shape of a rotating body, with the circular shape having an axis along the direction of translational movement of the piston. At the piston head, an opening is formed by a series of interconnected petals configured in the shape of a flower. By better mixing the air and fuel, the complete assembly further increases the combustion rate, thereby reducing nitrogen oxide emissions and particulate matter emissions. Summary of the Invention

[0005] In one or more examples, a piston can be configured to reciprocate within a bore of an engine. The piston can include an annular body including a combustion bowl that defines a volume and is surrounded on its top side by an annular crown portion that defines a top extrusion surface. The top extrusion surface can include an inner edge that defines an opening to the combustion bowl. The opening can include an area for combustion gases to enter the bowl during a compression stroke of the piston. The combustion bowl can include a concave surface that extends axially downward and radially outward relative to the top extrusion surface and defines a tangent that forms a concave angle with the top extrusion surface. The concave angle can be in the range of 28.0 degrees to 32.0 degrees.

[0006] In one or more examples, a piston may be configured to reciprocate within a bore of an engine. The piston may include an annular body including a combustion bowl defining a bowl volume and surrounded on its top side by an annular crown portion defining a top extrusion surface. The top extrusion surface may include an inner edge defining an inlet opening to the combustion bowl. The inlet opening may include an area for combustion gases to enter the bowl during a compression stroke of the piston. The combustion bowl may include a concave surface extending axially downward and radially outward relative to the top extrusion surface and defining a tangent forming a concave angle with the top extrusion surface. The ratio of the bowl volume to the area of ​​the inlet opening may be in the range of approximately 45 mm to approximately 52 mm.

[0007] In one or more examples, a piston can be configured to reciprocate within a bore of an engine. The piston can include an annular body including a combustion bowl that defines a bowl volume and is surrounded on its top side by an annular crown portion that defines a top extrusion surface. The top extrusion surface can include an inner edge that defines an opening to the combustion bowl. The opening can have an area for combustion gases to enter the bowl during a compression stroke of the piston. The combustion bowl can include a concave surface that extends axially downward and radially outward relative to the top extrusion surface and defines a tangent that forms a concave angle with the top extrusion surface. The ratio of the bowl volume to the concave angle can be in the range of approximately 12 cc / deg to approximately 15 cc / deg. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a perspective view of an internal combustion engine with a piston according to one or more examples.

[0009] Figure 2 yes Figure 1 A cross-sectional view of an internal combustion engine, particularly showing a piston according to one or more examples.

[0010] Figure 3 is a cross-sectional view of a piston according to one or more examples. DETAILED DESCRIPTION

[0011] Now refer to Figure 1 , shows an internal combustion engine 12 that may employ various embodiments of pistons constructed according to the principles described herein. Engine 12 may include an engine or cylinder block 14 in which a piston (not shown) reciprocates, and an engine or cylinder head 16 that may contain various engine components for introducing fluid into the bore / combustion chamber located in engine block 14.

[0012] Now go to Figure 2 , shows a cross-sectional view of a combustion engine system 10 including an internal combustion engine 12. The engine system 10 may include a unitary combustion engine 12 having a cylinder block 14 and a cylinder head 16 attached to the cylinder block 14. One or more combustion cylinders 18 may be formed in the cylinder block 14. That is, although only a single cylinder is shown, the internal combustion engine system 10 may include a multi-cylinder engine, and the description provided herein should be understood to apply equally to multiple cylinders and supporting systems or equipment. In one or more examples, several cylinders may be arranged in an inline pattern, a V-pattern, a radial pattern, or another pattern.

[0013] Cylinder 18 may include cylinder liner 20, and piston 22 may be movable within cylinder 18 between a bottom dead center (BDC) position and a top dead center (TDC) position, the distance between these positions defining a compression height 88. Engine 12 may be particularly adapted for a four-stroke engine cycle, although other engine cycles may also be provided. That is, for each power stroke of the piston, an intake, compression, and exhaust stroke may also be provided.

[0014] The piston 22 may be pivotally coupled to a first end of a connecting rod 24, for example, at a piston pin, and the other end of the connecting rod 24 may be coupled to a crankshaft 26. Thus, the up and down motion of the piston 22 may drive the rotational motion of the crankshaft. Furthermore, an oil sprayer 28 may be oriented to spray cooling and lubricating oil onto the underside of the piston 22. The sprayed oil may be received into an oil gallery within the piston to help maintain a suitable piston temperature.

[0015] The engine system 10 may also include an intake system 30. The intake system 30 may include an intake conduit 32 configured to deliver intake air for combustion to the cylinders 18. The intake system 30 may also include an intake manifold 40 and intake runners 41 extending from the intake manifold 40 to intake ports 43 that feed the cylinders 18. The intake manifold 40 may be coupled to a plurality of intake runners, each of which extends to one of the plurality of cylinders. The engine system 10 may also include a turbocharger 34 having a compressor 36 positioned to pressurize the intake air flow in response to rotation of a turbine 38. The engine system 10 may also include an exhaust manifold 42 configured to receive exhaust flow from the cylinders 18 and deliver the exhaust flow to the turbine 38 via an exhaust conduit 44.

[0016] The engine system 10 may also include a fuel inlet valve 48 positioned to allow fuel to flow from the fuel supply pipe 46 to the intake conduit 32. The illustrated arrangement may be a fumigant fuel inlet arrangement. In other examples, the engine system 10 may employ port injection, including a fuel injection valve extending into or near the intake port 43, or may employ manifold injection. It is contemplated that the engine system 10 may operate using a gaseous fuel such as natural gas. Natural gas or other gaseous fuels may be supplied from a pressurized fuel tank, a gas pipeline, a mine, or various other sources. The engine system 10 may also operate using various fuel mixtures including natural gas and gaseous molecular hydrogen, or various other gaseous hydrocarbon fuels and mixtures such as methane, ethane, biogas, landfill gas, or other fuels.

[0017] Intake valve 52 is shown supported in engine cylinder head 16 and is movable to open or close fluid communication between intake port 43 and cylinder 18. Similarly, exhaust valve 54 selectively fluidly connects cylinder 18 to exhaust manifold 42. In one or more examples, a total of two intake valves and a total of two exhaust valves may be provided for each cylinder in the engine. Engine system 10 may also employ spark ignition and include a spark plug 56 positioned to extend through engine cylinder head 16 into cylinder 18 to generate an electrical spark that is used to ignite the fuel and air mixture in cylinder 18. Spark plug 56 may be electrically connected to an electronic control unit 58 or another suitable electrical or magnetic device for generating a spark at a spark gap in cylinder 18. Still other embodiments may employ a pre-chamber spark plug that provides a pre-chamber within or is fluidly connected to the cylinder 18 to ignite a pre-chamber charge that ignites the main charge of fuel and air in the cylinder 18 according to known principles.

[0018] In the particular example of the present disclosure, the cylinder 18 may define a combustion chamber 62 disposed between the piston 22 and a bottom surface of the engine head 16. The cylinder may include a longitudinal axis L64 and a radial direction R66 perpendicular to the longitudinal axis L64.

[0019] Now refer to Figure 3 , further details of a piston for use in engine system 10 or another engine system may be described. As shown, piston 22 may have an annular body including a generally annular crown portion 68 having a longitudinal axis. It should be understood that the annular body of piston 22 may itself define a longitudinal axis and a radial direction when not in the bore of the engine, but such longitudinal axis and radial direction of the piston will coincide or nearly coincide with the longitudinal axis and radial direction of bore 18 when installed in bore 18. In addition, a skirt 70 is shown, which in some embodiments of the present disclosure may be a full skirt. This may not be the case in other embodiments of the present disclosure. The skirt and crown portion may be integral, monolithic, etc.

[0020] The piston 22 may also include a corrugated combustion bowl 72 and Figure 3 A cross-sectional plane (the cross-sectional plane containing the longitudinal axis L64 and the radial direction R66) defines a maximum axial depth D74, measured from the planar compression surface 76 (or a plane containing the surface) to the bottom concave arcuate surface 78, which defines the bottom end 80 of the swirl pocket 82 (so-called because it promotes mixing and atomization of fuel in air to help improve combustion efficiency). In some embodiments of the present disclosure, the ratio of the compression height 88 of the piston 22 to the maximum axial depth D74 may be in the range of 2.05 to 2.475 (e.g., approximately 2.26). Such a range may be considered to provide a low geometric compression ratio. In such embodiments, the ratio of the maximum diameter D84 of the combustion bowl defined by the concave arcuate side surface to the minimum diameter of the combustion chamber defined by the cylindrical surface (see D86) may be in the range of 0.94 to 1.14, or a ratio of 1.02 to 1.08 may be provided.

[0021] Additionally, the corrugated combustion bowl 72 may include a concave surface 90 extending from the planar extrusion surface 76. Figure 3 and a concave arcuate side surface 94 extending axially downward from the concave surface 90 defining an axial height H96 of the concave arcuate side surface 94. In some embodiments, a concave angle in the range of 28.0 to 32.0 degrees or a concave angle of 30 degrees may be provided. The ratio of the compressed height 88 to the axial height H96 is in the range of 4.0 to 13.0, or more specifically, in the range of 8.0 to 10.0 (may be approximately 8.7). It should be noted that Figure 2The most accurate depiction of this compression height, Figure 3 The compression height shown is an approximation as it roughly represents the amount of piston travel. Note that the piston can be slightly higher than Figure 2 The bottom dead center in the compression height is 0.0133°, and therefore, the bottom of the compression height is slightly below the top surface of the piston.

[0022] More specifically, the concave arcuate side surface 94 of the swirl pocket 82 can be axially spaced from the planar extrusion surface 76 (i.e., other surfaces interposed, such as the concave surface 90, etc.) and the bottom concave arcuate surface 78. For example, in some embodiments of the present disclosure, the swirl pocket 82 can include a cylindrical surface 100 (i.e., having a draft angle of less than 7.0 degrees) that defines a minimum diameter D86 of the combustion bowl 72 within a range of 111.0 mm to 114.0 mm. Furthermore, in some embodiments of the present disclosure, a ratio of a maximum axial depth D74 of the undulating combustion bowl 72 to an axial height H96 of the concave arcuate side surface 94 can be within a range of 2.6 to 5.6 (and can be approximately 3.9).

[0023] Specific geometric values ​​may include the following values. In some embodiments of the present disclosure, a small radius may connect the planar extrusion surface 76 to the concave surface 90 (e.g., may have a radius of 0 to 0.2 mm (or in the range of Figure 3 In addition, the planar extrusion surface 76 (with a small radius, if present) can define an inlet opening diameter D106 in the range of 100.0 mm to 106.0 mm, or a diameter D106 of 103.0 mm can be provided. In the case where the inlet opening is circular in shape, the area of ​​the inlet opening can therefore be approximately 7854 mm. 2 Up to approximately 8825mm 2 range, or can provide approximately 8332mm 2 Similarly, the concave arcuate side surface 94 defines a minimum arcuate surface diameter D108 within a range of 115.0 mm to 118.0 mm, while the maximum axial depth D74 of the wavy combustion bowl 72 is within a range of 41.0 mm to 44.0 mm. Other size ranges are possible in other embodiments of the present disclosure, such as in the case of scaled-up or scaled-down designs.

[0024] Still refer to Figure 3 In a cross-sectional plane, the crown portion 68 may include a top extrusion surface 76 and a concave surface 90 extending axially downward and radially outward from the top extrusion surface 76 and defining a tangent line T110 that forms a concave angle A92 with the top extrusion surface 76, the concave angle being in the range of 28 degrees to 32 degrees, or an angle of 30 degrees may be provided. The concave surface 90 may have various shapes, including Figure 3When the concave surface 90 is conical, the tangent line T110 and the concave surface 90 may coincide, as shown in FIG. Figure 3 When observed in cross section.

[0025] As mentioned previously herein, in some embodiments of the present disclosure, the swirl bag 82 further includes a concave arcuate surface (e.g., concave arcuate side surface 94) extending from the concave surface 90 and defining a radius of curvature ROC90. Figure 3 In the cross-sectional plane of the embodiment of the present invention, the center of the radius of curvature C90 can be set at an axial distance AC90 from the top extrusion surface 76 that is within the range of 8.5 mm to 10.5 mm. If this is the case, in some embodiments of the present disclosure, the center of the radius of curvature C90 can be set at an axial distance AC90 from the top extrusion surface 76 that is within the range of 9.5 mm to 11.0 mm. In addition, the concave arcuate surface can be a precise radius, but it does not have to be. As used herein, the term "arc" refers to any surface that is not conical or planar, and can include a radius, multiple radii, ellipses, spline curves, polynomial curves, etc.

[0026] Furthermore, the converging surface 112 can extend radially inward from the concave arcuate side surface 94 toward the longitudinal axis L64, defining a lower tangent line T112 at Figure 3 The converging surface 112 forms an acute angle A112 with the longitudinal axis L64 in the cross-sectional plane of FIG. In some embodiments of the present disclosure, this acute angle is within a range of 18.0 to 22.0 degrees. Like the concave surface, the converging surface 112 can also be conical, but need not be. A convex transition surface 113 can also be provided extending from the lower end of the converging surface 112 and leading to the cylindrical surface 100.

[0027] As previously mentioned herein, the vortex bag 82 may have a cylindrical surface 100 extending axially downward from the converging surface 112 or from the convex transition surface. The vortex bag 82 may also include a concave bottom end defining surface extending from the cylindrical surface 100 (e.g., see the bottom concave arcuate surface 78 defining the bottom end 80). The convex arcuate surface 118 may extend upward from the concave bottom end defining surface 78 to a flat platform surface 120 perpendicular to the longitudinal axis L64 (i.e., the flatness of the surface may be within 0.5 mm or less).

[0028] Continue to refer Figure 3, transition surface 113 may be defined by radius ROC 122 and may connect converging surface 112 to cylindrical surface 100. In some embodiments of the present disclosure, radius of curvature ROC 122 may be in the range of 13.0 mm to 17.0 mm. Furthermore, in some embodiments of the present disclosure, concave bottom end defining surface 78 may have radius of curvature ROC 114 in the range of 8.0 mm to 12.0 mm, while convex arcuate surface 118 may have radius of curvature ROC 118 in the range of 50.0 mm to 54.0 mm.

[0029] This piston geometry can be advantageous because it provides a relatively large bowl volume (which helps reduce and / or control the compression ratio) while also providing a relatively small area for gas to enter the bowl 72. The small area for gas to enter the bowl 72 can increase compression speed and can help improve fuel efficiency. Furthermore, the relatively sharp reentrant angle A92 can promote a more turbulent gas flow into the combustion bowl 72 due to the sudden widening of the available space below the narrower inlet opening. This can also improve fuel efficiency. In one or more examples, the ratio of the combustion bowl volume to the area of ​​the inlet opening can range from 45 mm to 52 mm, or a ratio of 48.5 mm can be provided. Furthermore, the ratio of the combustion bowl volume to the reentrant angle A92 can range from approximately 12 cc / deg to approximately 15 cc / deg, or a range from approximately 13 cc / deg to 14 cc / deg. The ratio of the maximum depth D74 of the combustion bowl 72 to the reentrant angle A92 can also range from approximately 1.3 mm / deg to approximately 1.5 mm / deg. Furthermore, a ratio of the minimum bowl diameter D86 to the recess angle A92 may be in a range of approximately 3.6 mm / deg to approximately 3.9 mm / deg.

[0030] In addition to the above geometries focused on power and combustion efficiency, other geometries may be provided to control the temperature of the piston 22. For example, Figure 3 In a cross-sectional plane, the corrugated combustion bowl 72 may be surrounded by an annular cooling channel 124 defining a maximum annular radial width W124. The cooling channel may be arranged radially adjacent to the swirl pocket 82. In some embodiments, the ratio of the minimum diameter D86 of the combustion bowl 72 to the maximum annular radial width W124 may be in the range of 6.3 to 7.7.

[0031] More specifically, the annular cooling passage 124 may define a radially inner cylindrical surface 126 and a radially outer cylindrical surface 128 that defines a maximum annular radial width W124 of the annular cooling passage 124. Furthermore, the annular cooling passage 124 may also include a conical surface 130 that is radially proximate to and parallel to the conical converging surface 112. Thus, the local wall thickness of the piston 22 remains relatively constant between these features.

[0032] The configuration, ratios, and dimensional ranges of any features of any embodiment discussed herein may be varied from what has been explicitly discussed or shown, depending on the application.

[0033] The piston can be made of steel (e.g., tool steel, stainless steel, etc.), cast aluminum alloy, forged aluminum alloy, or other suitable durable and corrosion-resistant materials. The geometry of the crown portion can be formed in a casting or forging process and then rough and / or finish machined as necessary. Suitable machining processes may include milling, turning, electrical discharge machining, etc.

[0034] Since some or all of the finished geometries of the piston are made using a turning process, those skilled in the art can easily understand that most, almost all, or all of the finished geometries of these components can remain unchanged or can not change significantly along the circumferential direction around the longitudinal axis.

[0035] Industrial Applicability

[0036] The piston and piston bowl described in this disclosure are specifically tailored to meet engine performance targets and accommodate specific piston configurations. Due to the bowl's depth and diameter, it helps maximize volume, thereby providing a lower geometric compression ratio. Simultaneously, a recessed feature at the bowl opening provides a relatively small bowl opening, which can generate relatively high extrusion velocities and help increase the total kinetic energy of the in-cylinder gas mixture. This recessed feature also allows for the aforementioned high extrusion velocities without compromising bowl volume. Furthermore, the ratio of combustion volume in the bowl to cooling volume in the cooling passages provides for increased cooling capacity. This combination of features reduces piston temperatures, reduces unburned hydrocarbons, and improves combustion efficiency when the engine is operating at rated load.

[0037] In practice, pistons, piston crowns, combustion chambers, and / or engine assemblies utilizing any of these components according to any of the embodiments described herein may be offered, sold, manufactured, and purchased as needed or desired in the aftermarket or at OEMs (Original Equipment Manufacturers). For example, the crown or piston may be used to retrofit an existing engine in the art, or may be sold with an engine or equipment utilizing the engine at the equipment's first point of sale.

[0038] The inventors have found that the selected bowl geometry helps achieve a balance between low compression ratio, high extrusion speed and effective cooling of the bowl edge and top area. Other designs may be able to achieve the same low compression ratio, but may affect the desired compression speed or the desired amount of cooling.

[0039] In other words, various embodiments of the present disclosure break the trade-off between increasing power output using a low compression ratio while simultaneously improving combustion efficiency.

[0040] It should be understood that the foregoing description provides examples of the disclosed components and techniques. However, it is contemplated that other embodiments of the present disclosure may differ in detail from the foregoing examples. All references to the present disclosure or examples thereof are intended to refer to the specific examples discussed at that point and are not intended to imply any limitation on the scope of the present disclosure more generally. All language regarding distinction and disparagement of certain features is intended to be a lack of preference for those features, but does not entirely exclude them from the scope of the present disclosure unless otherwise indicated.

[0041] Recitation of ranges of values ​​herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.

[0042] As used herein, the articles "a" and "an" are intended to include one or more items and are used interchangeably with "one or more." Where only one item is intended, the term "a" or similar language is used. Furthermore, as used herein, the terms "having," "having," "having," "with," and the like are intended to be open-ended terms. Furthermore, the phrase "based on" is intended to mean "based, at least in part, on" unless expressly stated otherwise.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments of the apparatus and assembly methods discussed herein without departing from the scope or spirit of the invention. Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the various embodiments disclosed herein. For example, the construction and function of some devices may differ from those described herein, and certain steps of any method may be omitted, performed in an order different from that specifically mentioned, or in some cases performed simultaneously or in sub-steps. In addition, certain aspects or features of the various embodiments may be changed or modified to produce further embodiments, and features and aspects of the various embodiments may be added to or substituted for other features or aspects of other embodiments to provide yet further embodiments.

[0044] The foregoing detailed description is intended to be illustrative rather than limiting.The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. A piston configured to reciprocate within a bore of an engine, the piston comprising: an annular body including a combustion bowl defining a volume and surrounded on a top side by an annular crown portion, the annular crown portion defining a top extrusion surface, the top extrusion surface having an inner edge defining an inlet opening to the combustion bowl, the inlet opening having an area for combustion gases to enter the bowl during a compression stroke of the piston, wherein the combustion bowl includes a concave surface extending axially downward and radially outward relative to the top extrusion surface and defining a tangent forming a concave angle with the top extrusion surface, the concave angle being in the range of 28.0 degrees to 32.0 degrees.

2. The piston of claim 1 , wherein a ratio of bowl volume to the area of ​​the inlet opening is in the range of about 45 mm to about 52 mm.

3. The piston of claim 1 or 2, wherein a ratio of bowl volume to the recess angle is in the range of about 12 cc / deg to about 15 cc / deg.

4. The piston of any one of claims 1 to 3, wherein the combustion bowl has a maximum depth, and a ratio of the maximum depth to the recess angle is in the range of about 1.3 mm / deg to about 1.5 mm / deg.

5. The piston of any one of claims 1 to 4, wherein the combustion bowl has a minimum diameter, and a ratio of the minimum diameter to the reentrant angle is in the range of about 3.6 mm / deg to about 3.9 mm / deg.

6. The piston of any one of claims 1 to 5, wherein the combustion bowl includes a swirl pocket having the concave surface and a concave arcuate surface extending from the concave surface and having a radius of curvature in the range of 8.5 mm to 10.5 mm.

7. A piston according to claim 6, wherein the vortex pocket further comprises a converging surface extending radially inward from the concave arcuate surface toward the longitudinal axis, defining a lower tangent forming an acute angle with the longitudinal axis, the acute angle being in the range of 18.0 degrees to 22.0 degrees, and optionally, wherein the converging surface is conical.

8. The piston according to claim 7, wherein the vortex bag further comprises a cylindrical surface extending axially downward from the converging surface, a concave bottom end defining surface extending from the cylindrical surface, and a convex arc surface extending upward from the concave bottom end defining surface to a flat platform surface perpendicular to the longitudinal axis.

9. The piston of claim 8, wherein the vortex pocket further comprises a radius connecting the converging surface to the cylindrical surface, the radius of curvature of the radius being in the range of 13.0 mm to 17.0 mm, the radius of curvature of the concave bottom end defining surface being in the range of 8.0 mm to 12.0 mm, and the radius of curvature of the convex arcuate surface being in the range of 50.0 mm to 54.0 mm.

10. The piston of any one of claims 1 to 9, wherein the concave surface is conical.

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