Piston optimized for combustion flame velocity and compression ratio in engine systems

Abstract

A piston (22) for an internal combustion engine (12) includes a piston skirt (64) and a piston crown (70) attached to the piston skirt and including a combustion face (72). The combustion face forms a piston rim (74) and a combustion bowl (78). A bowl rim (82) defines an intersection of the combustion bowl and the piston rim, and a reentry surface (84) defining a reentry angle extends between the bowl rim and the bowl outer wall. A ratio of a bowl depth dimension coincident with the piston central axis to a compressed height dimension coincident with the piston central axis is from about 0.30 to about 0.35.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to a piston for an internal combustion engine, and more particularly, to a piston having features proportional to enhanced flame speed and compression ratio. BACKGROUND

[0002] Internal combustion engines are widely used throughout the world for purposes ranging from vehicle propulsion to operation of pumps and compressors, to generation of electricity. A typical internal combustion engine employs a plurality of pistons reciprocating in cylinder bores in response to controlled combustion reactions to rotate a crankshaft, producing rapid pressure and temperature increases to drive the pistons. For decades, engineers have experimented with various fuels, exhaust treatment equipment and techniques, and different operating strategies in an effort to improve engine operation, reliability, and performance.

[0003] In recent years, a great deal of engineering resources have been devoted to developing pistons optimized for various applications. Depending on the engine type, the pistons are typically formed with specified combustion face geometries intended to interact with fuel, air, and / or exhaust streams during operation to achieve various purposes including optimization of emissions and / or efficiency, to mitigate or otherwise control in-cylinder temperatures and / or mechanical wear or corrosion, and for various other purposes. It has been observed that changes in piston geometry, often seemingly quite small, can have disproportionate effects on engine operation and performance, and the results of switching any one variable regarding piston geometry can often be quite unpredictable. Moreover, the difficulty of optimizing piston design is compounded by adding or removing piston volume, particularly on the combustion face, affecting the geometric compression ratio, often requiring other modifications to the piston or entire engine and support system design to maintain the compression ratio at a desired level. Optimized piston designs can have widely varying geometries depending on fuel type and many different operating parameters and different engine applications. One known piston is presented in U.S. Patent No. 9,670,829 to Boving et al. SUMMARY

[0004] In one aspect, a piston for an internal combustion engine includes: a piston skirt having a piston pin bore formed therein and defining a piston pin axis; and a piston crown having a combustion face and a combustion bowl, the combustion face forming a piston edge extending circumferentially around a piston central axis, the combustion bowl having a bowl bottom plate extending radially outward from the piston central axis to a bowl outer wall. The combustion face also includes a bowl edge defining an intersection of the combustion bowl and the piston edge, and a re-entry surface extending between the bowl edge and the bowl outer wall. A bowl depth dimension coinciding with the piston central axis is defined between the piston edge and the bowl bottom plate, and a compression height dimension coinciding with the piston central axis is defined between the piston edge and the piston pin axis. The ratio of the bowl depth dimension to the compression height dimension is about 0.30 to about 0.35.

[0005] On the other hand, a piston for an internal combustion engine includes: a piston skirt having a piston pin bore formed therein and defining a piston pin axis; and a piston crown including a combustion face and a combustion bowl, the combustion face forming a piston edge extending circumferentially around a piston central axis. The combustion face also includes a bowl edge defining an intersection of the combustion bowl and the piston edge, and a re-entry surface defining a re-entry angle of the bowl. The combustion bowl has a U-shaped profile axially below the re-entry surface relative to the piston central axis in a plane including the piston central axis. The ratio of the bowl depth dimension coinciding with the piston central axis to the compression height dimension coinciding with the piston central axis is 0.3 or greater.

[0006] In another aspect, an internal combustion engine system includes: an engine housing having a cylinder bore formed therein; an engine cylinder head; and a piston movable within the cylinder bore between a bottom dead center (BDC) position and a top dead center (TDC) position. The piston includes a piston skirt and a piston crown, the piston skirt having a piston pin bore formed therein and defining a piston pin axis, the piston crown including a combustion face and a re-entry combustion bowl, the combustion face forming a piston edge extending circumferentially around a piston central axis. The ratio of the bowl depth dimension coinciding with the piston central axis to the compression height dimension coinciding with the piston central axis is about 0.30 to about 0.35. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of an internal combustion engine system according to one embodiment;

[0008] Figure 2 This is a cross-sectional side view schematic diagram of a piston according to one embodiment; and

[0009] Figure 3 From Figure 2The view rotated 90 degrees, such as Figure 2 A cross-sectional side view of the piston. Detailed Implementation

[0010] Reference Figure 1 An internal combustion engine system 10 according to one embodiment is shown. The engine system 10 includes an internal combustion engine 12 having an engine housing or cylinder block 14 and an engine cylinder head 16 attached to the cylinder block 14. A combustion cylinder 18 is formed in the cylinder block 14 and may be one of a plurality of combustion cylinders formed therein. Although in Figure 1 Only a single cylinder and associated hardware are shown in this document; however, it should be understood that the internal combustion engine system 10 is typically a multi-cylinder engine, and the description and discussion of any component of the engine system 10 in the singular herein shall be understood as referring by analogy to other similar components of the engine system 10. The combustion cylinders in the cylinder block 14 may include any number of cylinders in any suitable arrangement, such as inline, V-type, or other arrangements.

[0011] Cylinder liner 20 is positioned within cylinder block 14, and piston 22 is movable within cylinder 18 in a generally conventional manner between bottom dead center (BDC) and top dead center (TDC) positions. Engine 12 is typically, but not necessarily, configured to operate in a four-stroke engine cycle. Piston 22 is coupled to connecting rod 24, which in turn is coupled to crankshaft 26. Injector 28 can be oriented to spray coolant and lubricating oil onto the underside of piston 22 and into oil passages therein, also in a generally conventional manner.

[0012] Engine system 10 also includes an intake system 30. The intake system 30 includes an intake duct 32 configured to deliver intake air for combustion to cylinder 18. The intake system 30 also includes an intake manifold 40 and an intake passage 41 extending from the intake manifold 40 to an intake port 43 fed to cylinder 18. Those skilled in the art will appreciate that the intake manifold will typically be coupled to multiple intake passages, each extending to one of multiple cylinders. Engine system 10 also includes a turbocharger 34 having a compressor 36 positioned to pressurize the incoming intake airflow in response to rotation of turbine 38. Engine system 10 also includes an exhaust manifold 42 configured to receive exhaust flow from cylinder 18 and deliver it to turbine 38 via exhaust duct 44.

[0013] Engine system 10 also includes a fuel inlet valve 48, which is positioned to allow fuel flow from fuel supply 46 to intake manifold 32. The arrangement shown will be considered a fumigation fuel inlet arrangement. In other cases, engine system 10 may be port-injected (including fuel injection valves extending into or near intake port 43) or manifold-injected. Engine system 10 is envisioned to typically operate with gaseous fuels such as natural gas. Natural gas or other gaseous fuels may be supplied from pressurized fuel tanks, gas pipelines, mines, or various other sources. Engine system 10 may also operate with 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, etc.).

[0014] Intake valve 52 is shown supported in engine cylinder head 16 and movable to open or close fluid communication between intake port 43 and cylinder 18. Exhaust valve 54 similarly selectively fluidly connects cylinder 18 to exhaust manifold 42. In typical applications, 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 be spark-ignited and includes spark plug 56 positioned to extend through engine cylinder head 16 into cylinder 18 to generate an electric spark for igniting the fuel and air mixture in cylinder 18. Spark plug 56 may be electrically connected to electronic control unit 58 or another suitable electrical or magnetic device for generating a spark at the spark gap in cylinder 18. Alternatively, other embodiments may employ a pre-combustion chamber spark plug that provides a pre-combustion chamber within cylinder 18 or provides a pre-combustion chamber fluidly connected to the cylinder for igniting a pre-combustion chamber charge that ignites the main fuel and air charge in cylinder 18 according to well-known principles.

[0015] Still referencing Figure 2 and 3 The features of piston 22 are shown in further detail. Piston 22 includes a piston skirt 64, which is generally formed as part of piston skirt portion 96 and has a piston pin hole 66 formed therein and defining a piston pin axis 68. Piston 22 also includes a piston crown 70 having a combustion surface 72 and a combustion bowl 78, the combustion surface forming a piston edge 74 extending circumferentially around the piston central axis 76. Combustion bowl 78 may include a re-entry combustion bowl and has a bowl bottom plate 80 extending radially outward from the piston central axis 76 to a bowl outer wall 81. Combustion surface 72 also includes a bowl edge 82 defining the intersection of combustion bowl 78 and piston edge 74, and a re-entry surface 84 extending between bowl edge 82 and bowl outer wall 81.

[0016] In the illustrated embodiment, the piston edge 74 extends planarly between the piston outer top surface 90 and the bowl edge 82. The piston outer top surface 90 may include a plurality of piston ring grooves 91, each piston ring groove extending circumferentially around the piston central axis 76 and configured to receive piston rings containing fluid within the cylinder 18 during use. The bowl bottom plate 80 may extend planarly between the piston central axis 76 and the bowl outer wall 81. Thus, each of the piston edge 74 and the bowl bottom plate 81 may be planar and may be parallel to each other. The bowl outer wall 81 may include an arcuate surface 92 extending radially outward and axially upward relative to the piston central axis 76 from the bowl bottom plate 80, and a cylindrical surface 94 extending axially upward relative to the piston central axis 74 from the arcuate surface 92 and circumferentially around the piston central axis 76.

[0017] The combustion bowl 78 may have a U-shaped profile axially below the re-entry surface 84 relative to the piston central axis 76 in a plane including the piston central axis 76. The re-entry surface 84 may extend from the bowl edge 82 to a cylindrical surface 94. A combustion surface 72, axially below the re-entry surface 84 relative to the piston central axis 76, can be understood as being formed by a total of three surfaces (including the cylindrical surface 94, the arcuate surface 92, and the bowl bottom plate 80). The combustion surface 72 may have a uniform rotational profile around the piston central axis 76. The arcuate surface 92 may... Figure 2 and 3 The plane of the page defines a radius of curvature of approximately 15 mm. The re-entry surface 84 can define a radius of curvature of approximately 10 mm in this plane. The cylinder bore diameter 60 is also... Figure 1 As shown in the figure. In this embodiment, the cylinder bore diameter 60 is approximately 170 mm.

[0018] As described above, piston 22 is understood to have a piston skirt portion 96 including a piston skirt 64. The piston skirt portion 96 is attached to piston crown 70, and in the illustrated embodiment, this attachment can be achieved by friction welding (such as inertial welding) or another strategy. A first weld post 98 and a second weld post 100 both extend circumferentially around piston central axis 76 and together attach piston skirt 64 to piston crown 70. Oil passage 102 is partially formed in piston crown 70 and partially formed in piston skirt portion 96, and extends circumferentially around combustion bowl 78. The first weld post 98 can extend from oil passage 102 to combustion bowl 78. Those skilled in the art will recognize that, compared to some other piston designs, the weld post extends to combustion bowl 78, while some conventional pistons place friction-welded posts below the combustion bowl.

[0019] Continue to refer generally to the attached diagram, but focus on Figure 2A bowl depth dimension 86, coinciding with the piston central axis 76, is defined between the piston edge 74 and the bowl base plate 80. A compression height dimension 88, coinciding with the piston central axis 76, is defined between the piston edge 74 and the piston pin axis 68. The ratio of the bowl depth dimension 86 to the compression height dimension 88 can be greater than 0.3. In an improvement, the ratio of the bowl depth dimension 86 to the compression height dimension 88 can be from about 0.30 to about 0.35, and in another improvement, from about 0.31 to about 0.33. In yet another improvement, the ratio of the bowl depth dimension 86 to the compression height dimension 88 can be about 0.32. In some practical embodiments, the bowl depth dimension 86 can be about 31 mm, and the compression height dimension can be about 96 mm.

[0020] Continue to refer generally to the attached diagram, but now focus on Figure 3 The combustion surface 72 defines a bowl opening size 108. The bowl opening size 108 can be understood as the diameter of the opening of the combustion bowl 78 passing through the piston central axis 76. In some embodiments, the bowl opening size 108 can be approximately 111 mm. The combustion surface 72 also defines a maximum bowl diameter 110 at the location of the cylindrical surface 94. The reentry angle 112, defined as the angle between the reentry surface 84 and the piston edge 74, can be greater than 75 degrees, and in practical embodiments is approximately 77 degrees.

[0021] Figure 3 The diagram also shows a clearance distance 104 that can extend between the piston 22 and the engine cylinder head 12 when the piston 22 is in the TDC position, and a clearance volume 106 defined between the combustion face 72 and the engine cylinder head 16. The clearance distance 104 can be approximately 4 mm. The clearance volume 106 can be approximately 397 cubic centimeters. The ratio of the combustion bowl volume to the clearance volume can be approximately 0.70 to approximately 0.75. The piston 22 also defines an opening area, which is understood as the area of ​​the circle defined by the opening size 108. The ratio of the bowl opening area to the clearance area, defined as the sum of the bowl opening area and the piston edge area, can be approximately 0.38 to approximately 0.45. In an improvement, the ratio of the bowl opening area to the clearance area can be approximately 0.43. A similar range of ratios can exist between the bowl opening area and the cross-sectional bore area of ​​the cylinder bore 18, but the cross-sectional area of ​​the cylinder bore 18 can be slightly larger than the sum of the bowl opening area and the piston edge area. The combustion bowl 78 can limit the aspect ratio of the maximum bowl diameter 108 to the bowl depth dimension 86 at the cylindrical surface 94 to approximately 0.27.

[0022] Industrial applicability

[0023] It has been observed that, in at least some cases, increased turbulence in the combustion chamber fluid flow can be associated with enhanced combustion flame velocity. In a general sense, increased turbulence helps to promote a rapid flame velocity, thereby accelerating combustion and, in some cases, improving engine efficiency, performance, and emissions. When operating engine system 10, the relatively small clearance distance 104 helps to provide a relatively rapid compression of fuel and air between the piston edge 72 and the cylinder head 16 as the piston 22 approaches the TDC position, due to the compression of the premixed gaseous fuel and air during the compression stroke. The compressed fuel and air mixture flows across the bowl rim 82 and, at least in part, based on the re-entry profile of the combustion bowl 78, generates turbulence that helps to promote a rapid flame velocity.

[0024] As also stated above, relatively small changes in piston geometry can have significant and / or unpredictable effects. Many engines are configured to operate at relatively tightly defined compression ratios. According to this disclosure, piston 22 can be understood as being very close to engine cylinder head 16 at TDC to facilitate strong compression of fuel and air. However, all else being equal, reducing the clearance distance will affect the compression ratio by reducing the volume in the cylinder bore. Therefore, combustion bowl 78 is manufactured relatively deep to maintain a compression ratio for a given stroke distance and compression height. The range of dimensions and ratios disclosed herein can help provide a piston with a compression ratio of approximately 13.3:1, while providing a faster flame velocity due to the high compression velocity and the turbulence caused by the inflow into the re-entry combustion bowl.

[0025] The term “approximately” is used in this document to describe certain dimensions and proportions. The term “approximately” can be understood as indicating approximation, as understood by those skilled in the art of engine and piston design, for example, through approximation, convention, or routine rounding to a consistent number of significant figures. According to the latter, “approximately 0.3” should be understood to mean 0.25 to 0.34. “Approximately 0.32” means 0.315 to 0.314, and so on. Dimensions or proportions listed without the preceding relative term can be understood as indicating dimensions or proportions within a measurement tolerance.

[0026] This specification is for illustrative purposes only and should not be construed as limiting the scope of this disclosure in any way. Therefore, those skilled in the art will understand that various modifications can be made to the embodiments currently disclosed without departing from the full and reasonable scope and spirit of this disclosure. Other aspects, features, and advantages will become apparent from the accompanying drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more”. The term “one” or similar language is used when intended to refer to only one item. Furthermore, as used herein, the terms “has,” “have,” “having,” etc., are intended to be open-ended terms. Additionally, the phrase “based on” is intended to mean “at least partially based on” unless otherwise expressly stated.

Claims

1. A piston (22) for an internal combustion engine (12), comprising: Piston skirt (64), the piston skirt having a piston pin hole (66) formed therein and defining the piston pin axis. The piston top (70) includes a combustion surface (72) and a combustion bowl (78). The combustion surface forms a piston edge (74) that extends circumferentially around the piston's central axis. The combustion bowl has a bowl bottom plate (80) that extends radially outward from the piston's central axis to the outer wall (81) of the bowl. The combustion surface also has a bowl edge (82) that defines the intersection of the combustion bowl and the piston edge, and a re-entry surface (84) that extends between the bowl edge and the outer wall of the bowl. A bowl depth dimension coinciding with the piston's central axis is defined between the piston edge and the bowl bottom plate, and a compression height dimension coinciding with the piston's central axis is defined between the piston edge and the piston pin axis; and The ratio of the bowl depth dimension to the compression height dimension is approximately 0.30 to approximately 0.

35.

2. The piston according to claim 1, wherein the piston edge extends planarly between the piston outer top surface (90) and the bowl edge, and the bowl bottom plate extends planarly between the piston central axis and the bowl outer wall; The outer wall of the bowl includes an arcuate surface (92) that extends radially outward and axially upward relative to the central axis of the piston from the bottom plate of the bowl, and a cylindrical surface (94) that extends axially upward from the arcuate surface and circumferentially around the central axis of the piston.

3. The piston of claim 1, wherein the re-entry surface extends from the edge of the bowl to the cylindrical surface, and the combustion bowl defines a U-shape having a uniform rotational profile circumferentially about the central axis of the piston.

4. The piston according to any one of claims 1-3, wherein: The ratio of the bowl depth to the compression height is approximately 0.32; and The combustion bowl has an aspect ratio of approximately 0.27 at its cylindrical surface.

5. The piston according to any of the preceding claims, wherein the bowl depth is about 31 mm and the compression height is about 96 mm.

6. The piston according to any of the preceding claims, wherein the combustion surface defines a bowl opening area and a piston edge area, and the ratio of the bowl opening area to a gap area defined as the sum of the bowl opening area and the piston edge area is from about 0.38 to about 0.

45.

7. The piston according to claim 6, wherein the ratio of the bowl opening area to the gap area is about 0.

43.

8. The piston according to any of the preceding claims further includes a piston skirt portion (96) including the piston skirt, and a first weld post (98) and a second weld post (100) that together attach the piston skirt portion to the piston top. An oil passage (102) is formed in the piston top and extends circumferentially around the combustion bowl, and the first welded post extends from the oil passage to the combustion bowl and extends circumferentially around the piston central axis.

9. The piston of claim 1, wherein the piston edge extends planarly between the outer top surface of the piston and the edge of the bowl, and the bottom plate of the bowl extends planarly between the central axis of the piston and the outer wall of the bowl, and the ratio is 0.31 to 0.

33.

10. An internal combustion engine system (10), comprising: Engine housing (14), the engine housing having a cylinder bore (18) formed therein; Engine cylinder head (16); Piston (22), which is movable within the cylinder bore between the bottom dead center (BDC) position and the top dead center (TDC) position; The piston includes a piston skirt (64) and a piston crown (70). The piston skirt has a piston pin hole (66) formed therein and defining a piston pin axis. The piston crown includes a combustion surface (72) and a re-entry combustion bowl (78). The combustion surface forms a piston edge (74) that extends circumferentially around the piston's central axis. The ratio of the bowl depth dimension coinciding with the piston's central axis to the compression height dimension coinciding with the piston's central axis is approximately 0.30 to approximately 0.

35.

11. The engine system of claim 10, wherein a clearance volume is defined between the combustion surface and the engine cylinder head at the TDC location, and the ratio of the combustion bowl volume to the clearance volume is about 0.70 to about 0.

75.

12. The engine system according to claim 10 or 11, wherein the ratio of the combustion bowl volume to the gap volume is about 0.

71.

13. The engine system according to any one of claims 10-12, wherein the piston edge extends planarly between the piston outer top surface (90) and the edge of the combustion bowl, and the ratio of the bowl opening area of ​​the combustion bowl to the bore area of ​​the cylinder is 0.38 to 0.45.

Images