PISTON, OPTIMIZED FOR COMBUSTION FLAME SPEED AND COMPRESSION RATIO IN ENGINE SYSTEM

Abstract

A piston (22) for an internal combustion engine (12) comprises a piston skirt (64) and a piston crown (70) attached to the piston skirt, which includes a combustion surface (72). The combustion surface forms a piston rim (74) and a combustion bowl (78). A bowl rim (82) defines an intersection between the combustion bowl and the piston rim, and a re-entrant surface (84) extends between the bowl rim and a bowl outer wall, defining an angle of entry. The ratio of a bowl depth dimension coinciding with the piston centerline to a compression height dimension coinciding with the piston centerline is approximately 0.30 to approximately 0.35.

Description

Technical field

[0001] The present disclosure relates generally to a piston for an internal combustion engine and in particular to a piston with features designed for an increased flame speed and an improved compression ratio. State of the art

[0002] Internal combustion engines are used extensively worldwide for a variety of purposes, from powering vehicles and driving pumps and compressors to generating electrical power. Conventional internal combustion engines use a number of pistons that move back and forth within cylinder bores to rotate a crankshaft in response to a controlled combustion reaction, which creates a rapid rise in pressure and temperature to drive the pistons. For decades, engineers have explored a wide range of fuels, exhaust aftertreatment devices and technologies, and operating strategies in efforts to improve engine operation, reliability, and performance.

[0003] In recent years, considerable technical resources have been invested in the development of pistons optimized for various applications. Depending on the type of engine, a piston is typically designed with a specific combustion surface geometry intended to interact with flows of fuel, air, and / or exhaust gases during operation for various purposes, including optimizing emissions and / or efficiency, mitigating cylinder temperatures and / or mechanical wear or corrosion, and for various other purposes. It has been observed that often seemingly minor changes in piston geometry can have disproportionate effects on engine operation and performance, and that the results of altering any variable related to piston geometry can often be quite unpredictable.Furthermore, adding or removing piston volume, particularly on the combustion surface, complicates piston design optimization and affects the geometric compression ratio, often necessitating further modifications to the piston or overall engine and system design to maintain the desired compression ratio. Depending on the fuel type, a variety of operating parameters, and different engine applications, optimized piston designs can exhibit highly diverse geometries. One well-known piston is described in U.S. Patent No. 9,670,829 by Bowing et al. Brief description

[0004] In one aspect, a piston for an internal combustion engine comprises a piston skirt with a pivot pin bore formed therein and defining a pivot pin axis, and a piston crown with a combustion surface that forms a piston rim extending circumferentially around a piston central axis, and a combustion chamber bowl with a bowl base extending radially outward from the piston central axis to a bowl outer wall. The combustion surface further comprises a bowl rim that defines an overlap between the combustion chamber bowl and the piston rim, as well as a re-entrant area that extends between the bowl rim and the bowl outer wall. A bowl depth dimension, coinciding with the piston central axis, is defined between the piston rim and the bowl base, and a compression height dimension, also coinciding with the piston central axis, is defined between the piston rim and the pivot pin axis.The ratio of the trough depth dimension to the compaction height dimension is approximately 0.30 to approximately 0.35.

[0005] In another aspect, a piston for an internal combustion engine comprises a piston skirt with a pivot pin bore formed therein and defining a pivot pin axis, and a piston crown with a combustion surface that forms a piston rim extending circumferentially around a piston center axis, as well as a combustion bowl. The combustion surface also includes a bowl rim that forms an intersection between the combustion bowl and the piston rim, and a re-entrant surface that defines a bowl entry angle. The combustion bowl has a U-shaped profile that lies axially below the re-entrant surface, with respect to the piston center axis, in a plane that encloses the piston center axis. The ratio of a bowl depth dimension coinciding with the piston center axis to a compression height dimension coinciding with the piston center axis is 0.3 or greater.

[0006] In another aspect, an internal combustion engine system comprises an engine block with a cylinder bore formed within it, a cylinder head, and a piston that is movable within the cylinder bore between bottom dead center (BDC) and top dead center (TDC) positions. The piston includes a piston skirt with a pivot pin bore that defines a pivot axis, and a piston crown with a combustion surface that forms a piston rim extending circumferentially around a piston axis, as well as a re-entrant combustion bowl. The ratio of a bowl depth dimension coinciding with the piston axis to a compression height dimension coinciding with the piston axis is approximately 0.30 to 0.35. Brief description of the drawings Fig. Figure 1 is a schematic view of an internal combustion engine system according to one embodiment; Fig. Figure 2 is a cutaway, schematic side view of a piston according to one embodiment; and Fig. Figure 3 is a cutaway, schematic side view of a piston as shown in Fig. 2, at 90 degrees opposite the view of Fig. 2 turned. Detailed description

[0007] With reference to Fig. Figure 1 shows an internal combustion engine system 10 according to one embodiment. The engine system 10 comprises an internal combustion engine 12 with an engine housing or cylinder block 14 and an engine head 16 attached to the cylinder block 14. An internal combustion cylinder 18 is formed in the cylinder block 14, which can be one of a plurality of internal combustion cylinders formed therein. Although in Fig. Since only a single cylinder and the associated hardware are shown in Figure 1, it is understood that the internal combustion engine system 10 is generally a multi-cylinder engine, and the present description and discussion of any single component of the engine system 10 is to be understood as referring by analogy to other similar components of the engine system 10. Internal combustion cylinders in cylinder block 14 can comprise any number of cylinders in a suitable arrangement, such as an inline arrangement, a V-arrangement, or any other.

[0008] A cylinder liner 20 is arranged within the cylinder block 14, and a piston 22 is movable within the cylinder 18 in a generally accepted manner between a bottom dead center (BDC) position and a top dead center (TDC) position. Engine 12 is typically, but not necessarily, configured for operation in a four-stroke engine cycle. Piston 22 is coupled to a connecting rod 24, which in turn is coupled to a crankshaft 26.

[0009] An oil atomizer 28 can be aligned to spray cooling and lubricating oil onto the underside of the piston 22 and into an oil channel located therein, also in a generally accepted manner.

[0010] Engine system 10 also includes an intake system 30. Intake system 30 includes an intake duct 32, which is configured to direct intake air for combustion to cylinder 18. Intake system 30 also includes an intake manifold 40 and an intake port 41, which extends from intake manifold 40 to an intake port 43 that supplies cylinder 18. Experts in the field will understand that an intake manifold would normally be coupled to a plurality of intake ports, each extending to one of a plurality of cylinders. Engine system 10 also includes a turbocharger 34 with a compressor 36, which is arranged to pressurize an incoming intake airflow in response to the rotation of a turbine 38. Engine system 10 also includes an exhaust manifold 42, which is configured to receive an exhaust flow from cylinder 18 and direct it via an exhaust port 44 to turbine 38.

[0011] Engine system 10 also includes a fuel inlet valve 48 arranged to allow a fuel flow from a fuel supply 46 to intake port 32. The illustrated arrangement will be recognized as a premixed fuel inlet arrangement. In other cases, engine system 10 may have indirect injection, including a fuel injector extending into or near the intake port 43, or port fuel injection. It is assumed that engine system 10 is typically operated with 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.Engine system 10 can also be operated with various fuel mixtures, including natural gas and gaseous molecular hydrogen, or with various other gaseous hydrocarbon fuels and mixtures such as methane, ethane, biogas, landfill gas or others.

[0012] An intake valve 52 is mounted in the engine head 16 and is shown to be movable in order to open or close a fluid connection between intake port 43 and cylinder 18.

[0013] Similarly, an exhaust valve 54 selectively connects cylinder 18 fluidically to exhaust manifold 42. In a typical application, a total of two intake valves and two exhaust valves can be provided for each cylinder of an engine. Engine system 10 can also be spark-ignited and includes a spark plug 56 arranged to extend through engine head 16 into cylinder 18 to generate an electric spark for igniting a fuel-air mixture in cylinder 18. Spark plug 56 can 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.In other implementations, a pre-chamber spark plug could be used, which provides a pre-chamber within cylinder 18 or in fluid communication with it, to ignite a pre-chamber charge that ignites a main charge of fuel and air in cylinder 18 according to known principles. With reference now made to the... Fig. 2 and Fig. 3. Features of piston 22 are described in more detail below. Piston 22 comprises a piston skirt 64, which is typically formed as part of a piston skirt section 96 and has a pivot pin bore 66 formed therein, defining a pivot pin axis 68. Piston 22 also comprises a piston crown 70 with a combustion surface 72, which forms a piston rim 74 extending circumferentially around a piston central axis 76, and a combustion chamber bowl 78. The combustion chamber bowl 78 may include a re-entrant combustion chamber bowl and has a bowl base 80 extending radially outward from the piston central axis 76 to the bowl outer wall 81. The combustion surface 72 further comprises a bowl rim 82, which forms an intersection of the combustion chamber bowl 78 and the piston rim 74, and a re-entrant surface 84 extending between the bowl rim 82 and the bowl outer wall 81.

[0014] In the illustrated embodiment, the piston rim 74 extends planarly between an outer piston base surface 90 and the bowl rim 82. The outer piston base surface 90 can have a plurality of piston ring grooves 91, each extending circumferentially around the piston central axis 76 and configured to receive a piston ring containing liquids in the cylinder 18 during operation. The bowl bottom 80 can extend planarly between the piston central axis 76 and the bowl outer wall 81. Thus, both the piston rim 74 and the bowl bottom 81 can be planar and parallel to each other.

[0015] The outer wall 81 of the combustion chamber bowl can have a curved surface 92 extending radially outward and axially upward from the bowl floor 80 with respect to the piston center axis 76, as well as a cylindrical surface 94 extending axially upward from the curved surface 92 with respect to the piston center axis 74 and circumferentially around the piston center axis 76. The combustion chamber bowl 78 can have a U-shaped profile lying axially below the re-entrant surface 84 with respect to the piston center axis 76 in a plane that includes the piston center axis 76. The re-entrant surface 84 can extend from the bowl edge 82 to the cylindrical surface 94. Axially below the re-entrant surface 84, with respect to the piston center axis 76, the combustion surface 72 can be understood as being formed by a total of three surfaces, including the cylindrical surface 94, the curved surface 92, and the bowl floor 80. The combustion surface 72 can have a uniform rotational profile around the piston center axis 76.A curved surface 92 can have a radius of curvature in the plane of the side in . Fig. 2 and Fig. 3 defines a diameter of approximately 15 millimeters. The re-entrant surface 84 can have a radius of curvature of approximately 10 millimeters in this plane. A cylinder bore diameter 60 is also defined in Fig. Figure 1 shows that in one implementation, the cylinder bore diameter is approximately 170 millimeters.

[0016] As mentioned above, piston 22 is understood to have a piston skirt section 96 that includes piston skirt 64. Piston skirt section 96 is attached to piston head 70 and, in the illustrated embodiment, can be fastened by friction welding, for example, by inertial welding or another strategy. A first weld post 98 and a second weld post 100 each extend circumferentially around the piston central axis 76 and together fasten piston skirt 64 to piston head 70. An oil channel 102 is formed partly in piston head 70 and partly in piston skirt section 96 and extends circumferentially around combustion chamber recess 78. The first weld post 98 can extend from oil channel 102 to combustion chamber recess 78.Experts in the field will recognize that, unlike certain other piston designs, a weld post extends to combustion chamber recess 78, whereas in certain conventional pistons a friction weld post is arranged below a combustion chamber recess.

[0017] With continued reference to the drawings in general, but with a focus on Fig. 2. A cavity depth dimension 86 is defined between the piston rim 74 and the cavity floor 80, coinciding with the piston center axis 76. A compression height dimension 88, coinciding with the piston center axis 76, is defined between the piston rim 74 and the pivot pin axis 68. The ratio of cavity depth dimension 86 to compression height dimension 88 can be greater than 0.3. In a refinement, the ratio of cavity depth dimension 86 to compression height dimension 88 can be between approximately 0.30 and approximately 0.35, and in a further refinement, between approximately 0.31 and approximately 0.33. In a further refinement, the ratio of cavity depth dimension 86 to compression height dimension 88 can be approximately 0.32. In certain practical implementations, the trough depth dimension of 86 can be approximately 31 millimeters and the compaction height dimension approximately 96 millimeters.

[0018] With continued reference to the drawings in general, but now focusing on Fig. 3, defines a combustion area of ​​72 and a trough opening dimension of 108.

[0019] The combustion bowl opening dimension 108 can be understood as the diameter of an opening in the combustion chamber bowl 78 that passes through the piston's central axis 76. In some embodiments, the combustion bowl opening dimension 108 can be approximately 111 millimeters. The combustion surface 72 also defines a maximum bowl diameter 110 at a point on the cylindrical surface 94. An entry angle 112 between the re-entering surface 84 and the piston edge 74 can be greater than 75 degrees, approximately 77 degrees in a practical implementation.

[0020] Fig.Figure 3 illustrates a clearance 104 that can extend between piston 22 and cylinder head 12 when piston 22 is in the TDC position, and a dead space 106 defined between combustion surface 72 and cylinder head 16. The clearance 104 can be approximately 4 millimeters. The dead space 106 can be approximately 397 cubic centimeters. The ratio between combustion chamber bowl volume and dead space can be between approximately 0.70 and approximately 0.75. Piston 22 also defines an opening area, which is to be understood as a circular area defined by the opening dimension 108. The ratio of bowl opening area to clearance, defined as the sum of the bowl opening area and the piston skirt area, can be between approximately 0.38 and approximately 0.45. In a refinement, the ratio of bowl opening area to clearance can be approximately 0.43.A similar ratio can exist between the bowl opening area and the cross-sectional area of ​​the cylinder bore 18, although the cross-sectional area of ​​the cylinder bore 18 may be somewhat larger than the sum of the bowl opening area and the piston skirt area. The combustion chamber bowl 78 can have an aspect ratio of approximately 0.27 between the maximum bowl diameter 108 on the cylindrical surface 94 and the bowl depth dimension 86. Commercial applicability

[0021] It has been observed that increased turbulence in the fluid flow within a combustion cylinder can be associated with an increased combustion flame speed, at least in certain cases. In a general sense, increased turbulence contributes to a faster flame speed, which accelerates combustion and, in some cases, improves the engine's efficiency, power, and emissions. When the engine system 10 is operating, during a compression stroke when the premixed gaseous fuel and air are compressed as the piston 22 approaches top dead center (TDC), the relatively small clearance 104 contributes to the relatively rapid compression of fuel and air between the piston skirt 72 and the cylinder head 16.The compressed fuel-air mixture flows over the edge of the bowl 82 and, at least partly based on the re-entering profile of the combustion chamber bowl 78, generates turbulence that promotes a rapid flame speed.

[0022] As also mentioned above, relatively minor changes to the piston geometry can have disproportionate and / or unpredictable effects. Many engines are designed to operate with a relatively narrowly defined compression ratio. According to the present disclosure, it can be understood that piston 22 comes very close to the cylinder head 16 at top dead center (TDC) to promote strong compression of fuel and air. However, a reduction in clearance would, all other things being equal, affect the compression ratio by reducing the volume in the cylinder bore. Accordingly, the combustion chamber recess 78 is relatively deep to maintain a compression ratio at a given stroke and compression height.The dimensions and ratio ranges disclosed herein can contribute to providing a piston with a compression ratio of approximately 13.3:1 while simultaneously achieving a higher flame speed resulting from the high flow velocity and turbulence caused by the flow into the re-entering combustion chamber recess.

[0023] Certain dimensions and proportions are described herein using the term "approximately." The term "approximately" can be understood as generally or roughly significant, as it would be understood by an expert in the field of engine and piston design, for example, by approximation, convention, or conventional rounding to a consistent number of significant figures. According to the latter, "approximately 0.3" is understood to be a value between 0.25 and 0.34. "Approximately 0.32" means between 0.315 and 0.314, and so on. Any dimension or proportion listed without a preceding relative term can be understood as the dimension or proportion within the margin of error.

[0024] The present description serves only for illustration and should not be interpreted as limiting the scope of this disclosure in any way. Those skilled in the art will therefore appreciate that various modifications to the embodiments disclosed herein could be made without deviating from the intended and appropriate meaning and scope of this disclosure. Other aspects, features, and advantages will become apparent upon examination of the accompanying drawings and attached claims. As used herein, the articles "one" are intended to include one or more elements and can be used interchangeably with "one or more." When only one element is intended, the term "one" or similar language is used. Similarly, the terms "comprising," "incorporating," "comprising," or the like are meant to be open-ended.Furthermore, the expression “based on” shall mean “at least partly based on” unless explicitly stated otherwise. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 9,670,829

[0003]

Claims

[1] Piston (22) for an internal combustion engine (12), comprising: defining a piston shaft (64) with a pivot pin bore (66) formed therein and a pivot pin axis; a piston base (70), including a combustion surface (72) forming a piston rim (74) extending circumferentially around a piston central axis, and a combustion chamber recess (78) with a recess base (80) extending radially outwards from the piston central axis to a recess outer wall (81); the combustion surface further comprising a bowl edge (82) which defines an overlap between the combustion chamber bowl and the piston edge, and a re-entrant surface (84) which extends between the bowl edge and the bowl outer wall; A bowl depth dimension coinciding with the piston center axis is defined between the piston rim and the bowl bottom, and a compression height dimension coinciding with the piston center axis is defined between the piston rim and the pivot pin axis; and The ratio of the trough depth dimension to the compaction height dimension is approximately 0.30 to approximately 0.

35. [2] Piston according to claim 1, wherein the piston rim extends planarly between an outer piston base surface (90) and the bowl rim and the bowl base extends planarly between the piston central axis and the bowl outer wall; wherein the bowl outer wall comprises a curved surface (92) extending radially outwards and axially upwards from the bowl base with respect to the piston central axis, and a cylindrical surface (94) extending axially upwards and circumferentially around the piston central axis from the curved surface. [3] Piston according to claim 1, wherein the re-entrant surface extends from the bowl edge to the cylindrical surface and the combustion chamber bowl defines a U-shape with a uniform rotation profile in the circumferential direction around the piston central axis. [4] Piston according to one of claims 1-3, wherein: the ratio of the trough depth dimension to the compaction height dimension is approximately 0.32; and The combustion chamber bowl defines an aspect ratio on the cylindrical surface of approximately 0.

27. [5] Piston according to one of the preceding claims, wherein the bowl depth dimension is about 31 millimeters and the compression height dimension is about 96 millimeters. [6] Piston according to one 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 approximately 0.38 to approximately 0.

45. [7] Piston according to claim 6, wherein the ratio of the bowl opening area to the gap area is approximately 0.

43. [8] Piston according to one of the preceding claims, further comprising a piston stem section (96), including the piston stem, and a first weld post (98) and a second weld post (100) which together fasten the piston stem section to the piston base; wherein an oil channel (102) is formed in the piston base and extends circumferentially around the combustion chamber recess, and the first weld post extends from the oil channel to the combustion chamber recess and circumferentially around the piston central axis. [9] Piston according to claim 1, wherein the piston rim extends planarly between an outer piston base surface and the bowl rim and the bowl base extends planarly between the piston central axis and the bowl outer wall and the ratio is from 0.31 to 0.

33. [10] Internal combustion engine system (10), comprising: an engine housing (14) with a cylinder bore (18) formed therein; a motor head (16); a piston (22) which is 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 (64) with a pivot pin bore (66) formed therein and defining a pivot pin axis, and a piston crown (70) with a combustion surface (72) forming a piston rim (74) extending circumferentially around a piston central axis, and a re-enclosing combustion chamber recess (78); and a ratio of a bowl depth dimension coinciding with the piston center axis to a compression height dimension coinciding with the piston center axis of approximately 0.30 to approximately 0.

35. [11] Engine system according to claim 10, wherein a dead space is defined between the combustion surface and the engine head at the TDC position and the ratio between the combustion chamber bowl volume and the dead space is between about 0.70 and about 0.

75. [12] Engine system according to claim 10 or 11, wherein the ratio of the combustion chamber bowl volume to the dead space is approximately 0.

71. [13] Engine system according to one of claims 10 to 12, wherein the piston edge extends planarly between an outer piston base surface (90) and the bowl edge and the ratio of a bowl opening area of ​​the combustion chamber bowl to a bore area of ​​the cylinder bore is 0.38 to 0.45.

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