EP3051110A1

EP3051110A1 - Cooling assembly for a cylinder of an internal combustion engine

Info

Publication number: EP3051110A1
Application number: EP15153123.3A
Authority: EP
Inventors: Jörg SCHELLE; Íñigo Guisasola
Original assignee: Caterpillar Energy Solutions GmbH
Current assignee: Caterpillar Energy Solutions GmbH
Priority date: 2015-01-29
Filing date: 2015-01-29
Publication date: 2016-08-03

Abstract

The present disclosure relates to a cooling assembly (100) for a cylinder of an internal combustion engine comprising a cylinder liner (40) and a cooling jacket (42). The cylinder liner (40) comprises a circumferential groove (50) formed in an upper part of an outer surface (41) of the cylinder liner (40). A circumferentially extending guiding surface (46) is formed in the outer surface (41) of the cylinder liner (40) and merges with a lower end (51) or an upper end (55) of the groove (50). The cooling jacket (42) is disposed around the cylinder liner (40) and includes a guiding portion (62) facing the guiding surface (46). A tear-off edge (54) is formed in cooling jacket (42) adjacent to the lower end (51) or the upper end (55) of the groove (50). In this manner, a ring-shaped nozzle (53) for the coolant entering the groove (50) is formed, and a turbulent flow of coolant is produced that enters the groove (50) to efficiently cool the cylinder liner (40).

Description

Technical Field

The present disclosure generally relates to a cooling assembly for a cylinder of an internal combustion engine, in particular, a cooling assembly including a cylinder liner and a cooling jacket disposed around the cylinder liner.

Background

Generally, internal combustion engines comprise a plurality of cylinders defining a combustion chamber for combustion of fuel such as gaseous fuels or liquid fuels. Each combustion chamber is generally defined at least in part by a cylinder liner inserted in a respective cylinder bore formed in an engine block of the internal combustion engine. As a result of the combustion inside each combustion chamber, high temperatures are present inside the combustion chamber, in particular, in an upper region of the cylinder liner. Therefore, in order to ensure the durability of the cylinder liners, the cylinder liners have to be cooled using a coolant such as cooling water or the like. In practice, a compromise has to be found between the durability of the cylinder liner and the reduction of the thickness of the same to achieve a desired cooling effect.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.

Summary of the Disclosure

According to one aspect of the present disclosure, a cylinder liner for a cylinder of an internal combustion engine comprises a circumferential groove formed in an upper part of an outer surface of the cylinder liner and a circumferentially extending guiding surface formed in the outer surface of the cylinder liner. The guiding surface merges with a lower end or an upper end of the groove. The guiding surface is configured to mate with a guiding portion of a cooling jacket disposed around the upper part of the outer surface of the cylinder liner to define a ring-shaped cooling passage for guiding a coolant to the groove.
According to another aspect of the present disclosure, a cooling assembly for a cylinder of an internal combustion engine comprises the cylinder liner according to the above aspect and a cooling jacket disposed around the upper part of the outer surface of the cylinder liner. The cooling jacket includes a guiding portion facing the guiding surface of the cylinder liner to define a ring-shaped cooling passage for guiding coolant to the circumferential groove of the cylinder liner. The cooling jacket further includes a tear-off edge formed adjacent to the lower end or the upper end of the circumferential groove of the cylinder liner for forming a ring-shaped nozzle for the coolant entering the groove.
According to a further aspect of the present disclosure, an internal combustion engine comprises an engine block, at least one cylinder defined at least in part by the engine block, and the cooling assembly of the above aspect of the present disclosure associated with the at least one cylinder.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

Brief Description of the Drawings

Fig. 1 shows an schematic diagram of an exemplarily disclosed internal combustion engine;
Fig. 2 shows a cross-sectional view of an exemplarily disclosed cooling assembly;
Fig. 3 shows an enlarged view of the exemplarily disclosed cooling assembly of Fig. 2; and
Fig. 4 shows an enlarged cross-sectional view of another exemplarily disclosed cooling assembly.

Detailed Description

The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described therein and illustrated in the drawings are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of patent protection. Rather, the scope of patent protection shall be defined by the appended claims.
The present disclosure may be based in part on the realization that, in order to assure the durability of a cylinder liner, it may be necessary to provide a wall thickness for the cylinder liner that results in a low heat transfer and therefore insufficient cooling of the cylinder liner, in particular, in an upper region of the cylinder liner. Further, the present disclosure may be based in part on the realization that a higher heat transfer coefficient can be reached when the flow velocity of coolant flowing along this upper region of the cylinder liner is increased. In this respect, the present disclosure may be based in part on the realization that an increase of the flow velocity can be obtained by providing an appropriate contour on the outer surface of the cylinder liner and an inner surface of a cooling jacket disposed around the upper region of the cylinder liner.
In particular, the present disclosure may be based on the realization that an increased flow velocity and a higher heat transfer coefficient can be reached by establishing a spray or nozzle between the cylinder liner and the cooling jacket. A tear-off edge may be provided in the inner surface of the cooling jacket or the outer surface of the cylinder liner to create a turbulent flow adjacent to the region of the outer surface of the cylinder liner that needs to be cooled the most.
Referring now to the drawings, an exemplary embodiment of an internal combustion engine 1 is illustrated in Fig. 1. Internal combustion engine 1 may include features not shown, such as fuel systems, air systems, cooling systems, peripheries, drivetrain components, etc. For the purposes of the present disclosure, internal combustion engine 1 is considered as a four-stroke gaseous fuel internal combustion engine. One skilled in the art will recognize, however, that internal combustion engine 1 may be any type of engine (liquid fuel, dual fuel, gaseous fuel, etc.). Furthermore, internal combustion engine 1 may be of any size, with any number of cylinders, and in any configuration ("V", in-line, radial, etc.). Internal combustion engine 1 may be used to power any machine or other device, including locomotive applications, on-highway trucks or vehicles, off-highway trucks or machines, earth moving equipment, generators, aerospace applications, marine applications, offshore applications, pumps, stationary equipment, or other engine powered applications.
Referring to Fig. 1, internal combustion engine 1 is suited to essentially any application wherein an internal combustion power source is desired, and internal combustion engine 1 comprises an engine block 2, at least one cylinder 4 providing at least one combustion chamber 6 for combusting fuel, a piston 8, a crank-shaft 10 connected to piston 8 via a piston rod 12, and a cylinder head 14. Piston 8 is configured to reciprocate within cylinder 4.
Internal combustion engine 1 further comprises an air/fuel supply system comprising a fuel source 16, an air inlet 18, a gas mixer 20, an intake manifold (not shown), an intake valve 24, and an intake pathway 26. Intake valve 24 is fluidly connected to combustion chamber 6. Intake valve 24 is configured to enable injection of compressed charge air and/or a mixture of compressed charge air and gaseous fuel into combustion chamber 6. After combusting the gas mixture, the exhaust gas is released out of the combustion chamber 6 via an outlet valve 28 into an exhaust gas outlet pathway 30, which may fluidly connect to an associated exhaust gas system 32 for treating the exhaust gas. Outlet valve 28 is also fluidly connected to combustion chamber 6.
Internal combustion engine 1 may also be a direct or port injection engine, or may include a pre-combustion chamber. Gaseous fuel internal combustion engine 1 may further include an exhaust gas recirculation system that may be operable to recirculate exhaust gas.
Those skilled in the art will appreciate that the compression ratio of gaseous fuel internal combustion engine 1 may be insufficient to cause compression ignition of gaseous fuel in combustion chamber 6. Therefore, each cylinder 4 of gaseous fuel internal combustion engine 1 is equipped with a spark plug 34.
A gas mixer 20 is provided and preferably disposed upstream of the intake manifold that supplies a combustion mixture to engine block 2 and associated cylinder 4. In particular, gas mixer 20 is configured to provide a mixture of gaseous fuel and air having a predetermined AFR. Gas mixer 20 may communicate with an electronic control module via a communication line, which in turn provides electronic signals to gas mixer 20 to control, for example, the AFR. The electronic control module may be further configured to control the overall operation of internal combustion engine 1. To control operation of internal combustion engine 1, the electronic control module may be further connected to various sensors such as combustion mixture pressure and temperature sensors, combustion peak pressure sensor, exhaust gas temperature and pressure sensors, lambda sensor.
Referring now to Fig. 2, an exemplary embodiment of a cooling assembly 100 for cylinder 4 is shown in a cross-sectional view.
As shown in Fig. 2, cooling assembly 100 includes a cylinder liner 40 and a cooling jacket 42 disposed around cylinder liner 40. Cylinder liner 40 may be inserted into engine block 2, and an upper end of cylinder liner 40 may project from engine block 2 when cylinder liner 40 is inserted in engine block 2. Cooling jacket 42 may be disposed around the upper part of cylinder liner 40 projecting from engine block 2 and surround the same. Cylinder head 14 may be disposed on top of cylinder liner 40 and cooling jacket 42, as shown in Fig. 2.
An outer surface 41 of cylinder liner 40 may include a circumferential groove 50 formed in an upper part of outer surface 41 of cylinder liner 40, a circumferentially extending guiding surface 46 formed in outer surface 41 of cylinder liner 40, and an abutment portion 45 formed in a region of outer surface 41 below circumferentially extended tapered guiding surface 46. In the exemplary embodiment, guiding surface 46 is formed as a tapered guiding surface. In other embodiments, however, guiding surface 46 may not be a tapered guiding surface, for example, may extend parallel to a longitudinal axis of cylinder liner 40. Abutment portion 45 extends substantially perpendicular to the longitudinal axis of cylinder liner 40 to facilitate insertion of cylinder liner 40 in engine block 2 during installation of cylinder liner 40. Cylinder liner 40 is supported on engine block 2 via abutment portion 45.
Circumferential extending tapered guiding surface 46 tapers inward towards the upper end of cylinder liner 40 and extends from a region of outer surface 41 of cylinder liner 40 adjacent to abutment portion 45. Guiding surface 46 merges with a lower end 51 of groove 50. As used therein, the term "merge" means that one portion of a surface is immediately connected to another portion of the surface. As will be described below, this includes a smooth transition from one portion to another portion, and also includes a connection via an edge formed between two portions, i.e., a discontinuous transition where an angle is formed between two surfaces merging with each other. In the embodiment shown in Fig. 2, tapered guiding surface 46 smoothly merges with lower end 51 of groove 50.
Circumferential groove 50 includes lower end 51 and an upper end 55 and extends around upper part of cylinder liner 40 with a curved cross-section. A radius of curvature of circumferential groove 50 may be between around 0.1 and around 0.25 times the inner diameter of the cylinder bore, i.e., the outer diameter of the portion of cylinder liner 40 that is inserted into the cylinder bore. It should be appreciated that, in some embodiments, the radius of curvature of groove 50 may be different. Further, the radius of curvature of groove 50 may not be constant. Accordingly, the values given above may specify a mean radius of curvature of groove 50. Circumferential groove 50 may be disposed in the region of cylinder liner 40 corresponding to the upper third of the cylinder stroke of piston 8 reciprocating in cylinder liner 40.
Guiding surface 46 is configured to mate with a guiding portion 62 of cooling jacket 42 disposed around upper part of outer surface 41 of cylinder liner 40. In this manner, a ring-shaped cooling passage 52 is defined between cylinder liner 40 and cooling jacket 42. Ring-shaped cooling passage 52 is configured to guide coolant to groove 50. In the exemplary embodiment, guiding portion 62 is a tapered portion configured to mate with tapered guiding surface 46 of cylinder liner 40. In other embodiments, however, guiding portion 62 may be formed as a straight portion or the like. A taper angle of tapered guiding surface 46 with respect to the longitudinal axis of cylinder liner 40 may be between 5° and 25°, for example, between 10° and 20°, or around 15°.
Cooling jacket 42 includes tapered guiding portion 62 and a tear-off edge 54 formed adjacent to lower end 51 of the circumferential groove 50. In the exemplary embodiment, a taper angle of tapered guiding portion 62 is substantially the same as the taper angle of tapered guiding surface 46. It will be appreciated, however, that in other embodiments the taper angle of tapered guiding portion 62 may differ from the taper angle of tapered guiding surface 46. Further, while in the exemplary embodiment shown in Fig. 2 both tapered guiding surface 46 and tapered guiding portion 62 are formed as linear portions, in other embodiments, tapered guiding surface 46 and/or tapered guiding portion 62 may extend towards the upper end of cylinder liner 40 with an arcuate configuration, for example, may include a convex or concave surface.
Cooling jacket 42 further includes a curved portion 60 extending between guiding portion 62 and tear-off edge 54. Curved portion 60 is curved towards cylinder liner 40 and is configured to guide coolant exiting from ring-shaped cooling passage 52 into circumferential groove 50. A radius of curvature of curved portion 60 may be matched to the radius of curvature of circumferential groove 50, and may be between around 0.1 and around 0.2 times the inner diameter of the cylinder bore. In some embodiments, the radius of curvature of curved portion 60 may be smaller than the radius of curvature of groove 50.
Cooling jacket 42 further includes a straight portion 56 extending upward from tear-off edge 54. Straight portion 56 extends to the position in the vicinity of upper end 55 of circumferential groove 50. Straight portion 56 substantially extends opposite circumferential groove 50 facing the same. It should be noted that, in some embodiments, straight portion 56 may project into circumferential groove 50. Further, it will be appreciated that, in some embodiments, portion 56 may also be formed as a curved portion. An angle formed between curved portion 60 and straight portion 56 (i.e., between the tangent to curved portion 60 and straight portion 56) at tear-off edge 54 may be between around 20° and around 60°, for example, between 30° and 50°, or around 40°.
Cooling jacket 42 also includes an inlet 44 for coolant such as cooling water or the like. Coolant entering via inlet 44 may be guided to a coolant accumulating chamber 48 fluidly connected to cooling passage 52 formed between guiding surface 46 and guiding portion 62. Coolant flowing out from circumferentially extending groove 50 may enter a coolant inlet 58 formed in cylinder head 14.
As shown in detail in Fig. 3, tear-off edge 54 and lower end 51 of circumferential groove 50 may define a ring-shaped nozzle 53 at lower end of groove 50. Coolant flowing through cooling passage 52 may enter circumferential groove 50 via ring-shaped nozzle 53. At tear-off edge 54 formed in coolant jacket 42, a turbulent flow of the coolant entering circumferential groove 50 may be produced. Further, the turbulent flow of coolant is directed into circumferential groove 50 by curved portion 60 formed between guiding portion 62 and tear-off edge 54. The turbulent flow of coolant flows along the bottom surface of groove 50, thereby cooling the associated region of the wall of cylinder liner 40. In this manner, the region of the wall of cylinder liner 40 adjacent to groove 50 is effectively cooled. Coolant exits circumferential groove 50 at upper end 55 of the same. Adjacent to upper end 55 of groove 50, a rounded-off portion 64 is formed adjacent to straight portion 56 in cooling jacket 42 to facilitate a flow of coolant from groove 50.
Fig. 4 shows another exemplary embodiment of a cooling assembly 100. In the exemplary embodiment shown in Fig. 4, tear-off edge 54 is not formed in cooling jacket 42. Instead, an edge 70 is formed at lower end 51 of groove 50. In particular, edge 70 is formed between guiding surface 46 and circumferential groove 50. An angle α formed between guiding surface 46 and circumferential groove 50 at edge 70 may be between around 120° and around 160°, for example, between 130° and 150°, or around 140°. Cooling jacket 42 includes a rounded-off portion 72 disposed adjacent to lower end 51 of circumferential groove 50. In the embodiment shown in Fig. 4, ring-shaped nozzle 53 is formed by curved portion 60 and edge 70. At edge 70, a turbulent flow of coolant is produced in the manner described above, and may be directed towards groove 50 by curved portion 60 formed between guiding portion 62 and rounded-off portion 72 of cooling jacket 42. As described above, coolant exits circumferential groove 50 at upper end 55 of the same. It should be appreciated that the same effects described above for the embodiment shown in Figs. 2 and 3 can be achieved with the embodiment shown in Fig. 4.
It will be appreciated that different geometries may be used in accordance with the present disclosure, depending on the respective applications. For example, cooling passage 52 may be formed with a thickness of between around 1 mm and around 3 mm.

Industrial Applicability

In the following, cooling of cylinder liner 40 during operation of internal combustion engine 1 will be described with reference to Figs. 2 and 3.
During operation of internal combustion engine 1, coolant may enter cooling jacket 42 via inlet 44. Coolant entering inlet 44 may be guided to coolant accumulating chamber 48 via channels (not shown) formed in cooling jacket 42. Coolant from coolant accumulating chamber 48 is delivered to circumferential groove 50 via cooling passage 52 formed between circumferentially extending tapered guiding surface 46 and tapered guiding portion 62. Coolant from cooling passage 52 enters circumferential groove 50 via ring-shaped nozzle 53 formed between lower end 51 of groove 50 and tear-off edge 54. Further, coolant from cooling passage 52 is guided into groove 50, i.e., towards a bottom portion of the same, via curved portion 60 of cooling jacket 42.
At tear-off edge 54, a turbulent flow of coolant is produced. The turbulent flow results in an increase of the flow velocity of coolant flowing along the bottom surface of groove 50, thereby resulting in a higher heat transfer coefficient when compared to the case where tear-off edge 54 is not present. After flowing along the bottom of circumferential groove 50, coolant exits circumferential groove 50 at upper end 55 of the same and enters coolant inlet 58 of cylinder head 14.
It will be readily appreciated that tear-off edge 54 may also be formed adjacent to upper end 55 of groove 50 in case coolant flows in the opposite direction, i.e., from the top of cylinder liner 40 to the bottom of the same. In this case, guiding portion 62 of cooling jacket 42 is formed in an upper part of the same. Cylinder liner 40 and cooling jacket 42 may have a corresponding symmetric configuration with respect the other parts shown in Figs. 3 and 4. Further, in case edge 70 is formed in cylinder liner 40, edge 70 may be formed at upper end 55 of groove 50, and cylinder liner 40 and cooling jacket 42 may have an appropriate configuration to achieve the desired flow of coolant in groove 50 as described above.
Although the preferred embodiments of this invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.

Claims

A cylinder liner (40) for a cylinder (4) of an internal combustion engine (1), comprising:
a circumferential groove (50) formed in an upper part of an outer surface (41) of the cylinder liner (40); and

a circumferentially extending guiding surface (46) formed in the outer surface (41) of the cylinder liner (40), the guiding surface (46) merging with a lower end (51) or an upper end (55) of the groove (50),

wherein the guiding surface (46) is configured to mate with a guiding portion (62) of a cooling jacket (42) disposed around the upper part of the outer surface (41) of the cylinder liner (40) to define a ring-shaped cooling passage (52) for guiding coolant to the groove (50).
The cylinder liner of claim 1, wherein a taper angle of the guiding surface (46) with respect to a central axis of the cylinder liner (40) is between around 5° and 25°, for example, between 10° and 20°, or around 15°.
The cylinder liner of claim 1 or 2, wherein the circumferential groove (50) has a curved cross-section with a radius of curvature of between around 0.1 and around 0.25 times the diameter of the cylinder (4).
The cylinder liner of any one of claims 1 to 3, further comprising an edge (70) formed between the guiding surface (46) and the circumferential groove (50), wherein an angle (α) formed between the guiding surface (46) and the circumferential groove (50) at the edge (70) is between around 120° and around 160°, for example, between 130° and 150°, or around 140°.
The cylinder liner of any one of claims 1 to 4, further comprising an abutment portion (45) formed in a region of the outer surface (41) of the cylinder liner (40) below the circumferentially extending guiding surface (46), the abutment portion (45) being configured to support the cylinder liner (40) on an engine block (2) of the internal combustion engine (1).
A cooling assembly (100) for a cylinder (4) of an internal combustion engine (1), comprising:
the cylinder liner of any one of claims 1 to 5; and

a cooling jacket (42) disposed around the upper part of the outer surface (41) of the cylinder liner (40), the cooling jacket (42) including:
a guiding portion (62) facing the guiding surface (46) of the cylinder liner (40) to define a ring-shaped cooling passage (52) for guiding coolant to the circumferential groove (50) of the cylinder liner (40); and

a tear-off edge (54) formed adjacent to the lower end (51) or the upper end (55) of the circumferential groove (50) for forming a ring-shaped nozzle (53) for the coolant entering the groove (50).
The cooling assembly of claim 6, wherein the cooling jacket (42) includes a curved portion (60) extending from the guiding portion (62) to the tear-off edge (54).
The cooling assembly of claim 7, wherein the curved portion (60) is configured to guide the coolant exiting from the ring-shaped cooling passage (52) into the circumferential groove (50).
The cooling assembly of claim 8, wherein a radius of curvature of the curved portion (60) is between around 0.1 and around 0.2 times the diameter of the cylinder (4).
The cooling assembly of any one of claims 7 to 9, wherein the cooling jacket (42) includes a straight portion (56) extending upward or downward from the tear-off edge (54).
The cooling assembly of claim 10, wherein the straight portion (56) extends to a position in the vicinity of the upper end (55) or the lower end (51) of the circumferential groove (50).
The cooling assembly of any one of claims 7 to 11,
wherein the curved portion (60) extends into the circumferential groove (50).
The cooling assembly of any one of claims 7 to 12,
wherein a taper angle of the guiding portion (62) is substantially the same as a taper angle of the guiding surface (46).
The cooling assembly of any one of claims 7 to 13,
wherein the cooling jacket (42) at least partially defines a coolant accumulating chamber (48) fluidly connected to the cooling passage (52).
An internal combustion engine (1), comprising:
an engine block (2);

at least one cylinder (4) defined at least in part by the engine block (2); and

the cooling assembly (100) of any one of claims 7 to 14 associated with the at least one cylinder (4).