Technical field

[001] The present invention relates to a nozzle for a cooling arrangement of a piston in an internal combustion piston engine according to the preamble of claim 1.

[002] The present invention relates to a cooling arrangement for a piston of an internal combustion engine, which piston is arranged inside a cylinder liner of the engine, the cooling arrangement comprising a cooling oil gallery arranged inside the piston, and a cooling oil nozzle attached to inner surface of the cylinder liner for injecting cooling oil to the piston, and a cooling oil duct in the cylinder line for supplying the cooling oil to the nozzle.

Background art

[003] Invention relates to the field of internal combustion piston engine. Cooling of pistons in large medium speed internal combustion piston engines is typically arranged through drillings in the crankshaft, connecting rods and gudgeon pins. In high-speed engines, piston cooling is often implemented by utilizing oil jets. Oil jet cooling is advantageous also in medium speed engines, since that way there is no need for oil drillings in the crank gear components and it allows thus higher loading and lower manufacturing costs. In a typical oil jet cooling arrangement, the cooling arrangement is provided with a separate oil system for piston cooling. Oil injection nozzles for spraying the cooling oil are arranged inside the engine block. Through the injection nozzles, the oil is sprayed onto the bottom side of each piston. The piston skirt is provided with a space for receiving the oil. There are drillings in the piston which lead from the oil receiving area into a piston crown cooling gallery. A drawback of this kind of piston cooling arrangements is that the spraying distance is relatively long, which has an adverse effect on the functioning of the cooling arrangement. The cooling arrangements may also be challenging to implement, since the space inside the engine block and especially below the cylinders is limited because of the moving connecting rods and counterweights.

[004] WO2013121105A1 discloses cooling arrangement for a reciprocating piston of an internal combustion piston engine, in which engine the piston is arranged inside a cylinder liner of the engine and comprises a piston crown and a piston skirt, and the cooling arrangement comprising a cooling oil gallery that is arranged at least partly inside the piston crown, a nozzle for injecting cooling oil into a space between the piston and the cylinder liner below the piston crown, an opening that is arranged on the bottom surface of the cooling oil gallery for introducing the cooling oil from the space below the piston crown into the cooling oil gallery, and a cooling medium duct for supplying the cooling oil to the nozzle which is arranged inside the cylinder at such a height that the tip of the nozzle is above the center axis of the gudgeon pin of the piston when the piston is at bottom dead center. The solution disclosed in WO2013121105A1 relies on basic idea that the nozzle is arranged close to the bottom surface of the cooling oil gallery and therefore the spraying distance is short, and the cooling effect of the cooling oil is improved.

[005] Even if the disclosed cooling arrangement system is advantageous as such, it has been discovered that the oil jet which the nozzle creates needs to be accurately directed to the opening arranged on the bottom surface of the cooling oil gallery.

[006] An object of the invention is to provide a nozzle for cooling arrangement of a piston in an internal combustion piston engine which provides improved jet form suitable for transfer the cooling to the piston effectively.

Disclosure of the Invention

[007] Objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention. [008] According to an embodiment of the invention a nozzle for a cooling arrangement of a piston in an internal combustion piston engine comprises a body in which a flow channel for cooling oil is arranged, an inlet for cooling oil and an outlet for cooling oil, wherein the inlet comprises attaching means for attaching the nozzle to the engine.

[009] The flow channel of the nozzle comprises at least one flow conditioner between the inlet and the outlet, in which flow conditioner cross-sectional area of the flow channel is comprised of multiple parallel flow conduits, and the outlet has a cross-sectional area which is smallerthan the smallest cross-sectional area of the flow channel.

[0010] This way a solid flow pattern which reach over a long span remaining solid and laminar is obtained. Thus supplying cooling oil to a piston is improved. The nozzle can be attached to the lower end of the cylinder liner.

[0011] Advantageously the nozzle is monolithic structure made by additive manufacturing and therefore the nozzle is very stiff and robust while the flow conditioner can be made extremely efficient.

[0012] According to an embodiment of the invention the outlet is provided with an end part constricting the cross-sectional area of the flow channel. This provides acceleration of cooling oil flow before exiting the nozzle providing a longer reach of the oil jet.

[0013] Advantageously the constriction is realized such that the outlet is provided with a conical end part constricting the cross-sectional area of the flow channel.

[0014] According to an embodiment of the invention the flow conditioner comprises at least three parallel flow conduits which have at least one common intermediate wall between two flow conduits.

[0015] Preferably each conduit of the flow conditioner has cross section defined such that distance between center line of each adjacent conduit is the same. This way to transition of the flow out from the flow conditioner is smooth and turbulence is minimized. [0016] According to an embodiment of the invention each conduit of the flow conditioner section has hexagon cross section.

[0017] According to an embodiment of the invention the attaching means comprises a flange having partial cylindrical support surface. This facilitates attachment of the nozzle to the liner without a need of a separate intermediate part.

[0018] Advantageously the outlet is at an angle in relation to the inlet flange such that the jet is directed parallel to a cylinder liner of the engine, when installed for use. In some practical application this can be realized such that the inlet and the outlet have an opening direction and the opening directions are at substantially right angle in respect to each other.

[0019] According to an embodiment of the invention the nozzle comprises a flow conditioner in which each conduit of the flow conditioner has cross section defined such that distance between center line of each adjacent conduit is the same, and which nozzle comprises a conical end part wherein the flow conditioner extends from inlet of the nozzle to the conical end part. This way to transition of the flow out from the flow conditioner is smooth and turbulence is minimized.

[0020] A cooling arrangement for a reciprocating piston of an an internal combustion piston engine, which piston is arranged inside a cylinder liner of the engine, the cooling arrangement comprising a cooling oil gallery arranged inside the piston, and a cooling oil nozzle for injecting cooling oil into the cooling oil gallery via an opening that is arranged to the cooling oil gallery, and a cooling oil duct for supplying the cooling oil to the nozzle. The nozzle comprises a body in which a flow channel for cooling oil is arranged, an inlet for cooling oil and an outlet for cooling oil, wherein the inlet comprises attaching means for attaching the nozzle to the engine. The flow channel of the nozzle comprises at least one flow conditioner between the inlet and the outlet, in which flow conditioner cross- sectional area of the flow channel is comprised of multiple parallel flow conduits, and the outlet has a cross-sectional area which is smaller than the smallest cross- sectional area of the flow channel. [0021] In this context the word monolithic is used in the meaning of formed as a single piece or composed of material without joints or seams.

[0022] The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0023] In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which

Figure 1 illustrates schematically a piston cooling arrangement provided with a nozzle according to an embodiment of the invention,

Figure 2 illustrates a view a nozzle for a cooling arrangement of a piston in an internal combustion piston engine according to an embodiment of the invention,

Figure 3 illustrates another view a nozzle according to Figure 2,

Figure 4 illustrates another view a nozzle according to Figure 2,

Figure 5 illustrates a nozzle for a cooling arrangement of a piston in an internal combustion piston engine according to another embodiment of the invention, and

Figure 6 illustrates another view a nozzle according to Figure 5.

Detailed Description of Drawings

[0024] In the figure 1 there is shown a cooling arrangement 12 for a reciprocating piston 14 of an internal combustion piston engine 10 according to an embodiment of the invention. In the figure 1 , the piston 14 is at bottom dead center position. The engine 10 where the piston cooling arrangement is used is a large medium or low speed an internal combustion piston engine. The engine can be used, for instance, as a main or an auxiliary engine of a ship, or at a stationary power plant for producing electricity. The engine can be provided with suitable number of cylinders according to required power output, which can be arranged for example in line or in a V-configuration. Each cylinder of the engine is provided with a cylinder liner 16 attached to a block 18 of the engine 10. The piston 14 is arranged reciprocate in the cylinder liner 16. A cylinder head which is assembled on top of the cylinder liner is not shown here. The piston comprises a piston crown 14.1 and a piston skirt 14.2. The piston 14 is connected to a connecting rod 20 with a gudgeon pin 22. In the embodiment of the figure 1 the piston 14 is a so-called box-type piston, where the piston skirt 14.2 is open at the ends of the gudgeon pin 22. A space is thus formed below the piston crown 14.1 between the cylinder liner 16 and the piston 14 at both ends of the gudgeon pin 22.

[0025] For cooling the piston 14, the engine is provided with a cooling arrangement 12 for cooling the piston. The cooling arrangement is used for introducing cooling oil onto the bottom surface of the piston 14. In the embodiment shown in the figure 1 the cooling oil is introduced further into an oil gallery 24 that is arranged at the upper end of the piston 14 and at least partly inside the piston crown 14.1. The cooling arrangement comprises a nozzle 26 that is arranged inside the cylinder. The nozzle 26 operates as an injector which produces a jet with solid stream. The nozzle 26 is configured to produce a constantly flowing jet which remains as a solid stream until hitting the bottom of the piston 14 during the whole span of reciprocating movement of the piston 14. There is a suitable oil pump in the engine (not shown) to which the cooling arrangement for supplying the cooling oil to the nozzle 26, is connected.

[0026] In the embodiment of the figure 1 , a cooling oil duct 28 is arranged partly inside the wall of the cylinder liner 16. With this arrangement, the need for separate pipes can be reduced. The nozzle 26 is arranged to protrude from the wall of the cylinder liner 16 into the cylinder.

[0027] In the figure 1 there are shown two alternative routes for the cooling oil duct. First an opening at lower end surface of the cylinder liner 16 for introducing the cooling oil into the cooling oil duct 28 inside the wall of the cylinder liner 16 is disclosed and secondly a cooling oil duct 28 through the wall of cylinder liner 16 by a drilling in the lower radial support of the cylinder liner 16 is introduced. The inner surface of the cylinder liner 16 is provided with an opening, which is in fluid communication with the cooling oil duct 28. Through the opening, the cooling oil can be supplied to an inlet of the nozzle 26. The nozzle 26 is generally L-shaped, and an outlet of the nozzle 26 points generally towards the piston 14. The cooling oil jet is directed to the bottom surface of the cooling oil gallery 24 of the piston.

[0028] Figures 2 to 4 shows a nozzle 26 for a cooling arrangement 12 of a piston in an internal combustion piston engine 10 according to an embodiment of the invention. The figure 2 depicts the nozzle 26 seen from above and sideways of the nozzle, the figure 3 depicts a cut-out view of the nozzle 26 and the figure 3 shows an outlet 36 of the nozzle seen directly in front of the outlet, which is above when installed for use. The nozzle 26 comprises a body 30 into which a flow channel 32 for cooling oil is arranged, an inlet 34 for the cooling oil and an outlet 36 for the cooling oil. The inlet is configured to be connected to the oil duct 28 as illustrated in the figure 1. The inlet 34 also comprises attaching means 40 for attaching the nozzle to the engine 10 to a part which has outlet of the cooling oil duct. The attaching means is preferably a flange provided with holes 42 for attachment screws. The flange surface is not flat but curved so as to conform with the surface of the cylinder liner. Thus, the flange has a partial cylindrical surface, which has its center of curvature on the side of the nozzle body 30.

The inlet 34 is an opening in the flange 40. After the inlet 34, in the intended flow direction of the cooling oil, the flow channel has a smooth bend, with radius of curvature R. Actual radius of such a smooth curve in practical application is effected inter alia by geometry of the flow channels 32, oil viscosity and oil temperature.

[0029] In the nozzle 26 there is at least one flow conditioner 38 arranged to the flow channel 32 after the smooth bend section, between the inlet 34 and the outlet 36. In the flow conditioner 38 cross-sectional area of the flow channel 32 is comprised of multiple parallel flow conduits 32’. When there are several separate flow conduits 32’ which single conduit 32’ has considerably smaller cross- sectional area compared the total cross-sectional area of the flow channel 32, intensity of turbulence of the flow in considerably decreased. The separate flow conduits 32’ are separated by substantially thin wall, thickness being less than 1 mm, but more than 0,3mm. This way the total cross sectional flow area of the flow conditioner 38 is substantially equal to cross sectional flow area of the flow channel 32. The flow conditioner 38 shown in the figure 3 comprises three parallel flow conduits 36’ which have at least one common intermediate wall between two flow conduits. In the embodiment shown in the figure 3 there is a straight portion of the flow channel 32 after the flow conditioner 38 extending to the outlet 36. Thus figure 3 shows an embodiment where the bend is followed by the flow conditioner 38 which is followed by a straight portion of the flow channel 32.

[0030] Length of the flow conditioner 38 and number of parallel flow conduits 32’ has a relationship to the radius of curvature R of the smooth bend. Increasing the length of the flow conditioner 38 and/or increasing the number flow conduits 32’ allows using smaller radius of curvature R. Suitable balance between the variables can be easily found by testing. The general aim is to reduce flow interference in outlet flow. The desired outcome of the solid jet can be evaluated visually.

[0031] The angle of the bend is 90°, having, of course, deviations due to manufacturing and/or installation tolerances. The inlet 34 and the outlet 36 have an opening direction and the opening directions are at substantially at right angle in respect to each other. The angle means the angle between a normal of the surface of the cylinder liner and flow direction of cooling oil at the outlet. The nozzle 26 is configured to direct the cooling oil flow in a direction of longitudinal axis of the cylinder liner 16, that is parallel to the liner of the engine. This way the flow jet hits a same spot of the piston regardless of the distance between the piston 14 and the nozzle 36.

[0032] As it also come clear from the figure 3 the outlet 36 has a cross-sectional area which is smaller than the smallest cross-sectional area of the flow channel 36. In other words, the outlet is provided with an end part which constricts the cross-sectional area of the flow channel at the very end of the channel. The flow conditioner 38 ends before the constriction at the outlet 36. This way the exit flow velocity of the cooling oil is accelerated before exiting the nozzle 26. [0033] In the embodiment shown in the figures 2 to 4 there is a constriction 44 directly downstream the inlet 34 before the bend, such that the cross-sectional area of the conduit 32 is smaller than the cross-sectional area of the inlet 34. The constriction also first directs the channel 32 to direction which is opposite to the direction of the outlet 36. This relates to the curved section such that a center of curvature of the bend is, in the terms of the figures 2 to 4 vertically in the area of the inlet 34.

[0034] Figures 5 and 6 shows a nozzle 26 for a cooling arrangement 12 of a piston in an internal combustion piston engine 10 according to another embodiment of the invention. The figure 5 depicts the nozzle 26 seen from above and sideways of the nozzle and the figure 6 depicts a cut-out view of the nozzle 26.

[0035] The nozzle 26 comprises a body 30 and a flow channel 32 for cooling oil arranged to the body. There is also an inlet 34 for the cooling oil and an outlet 36 for the cooling oil. The inlet is configured to be connected to the oil duct 28 as illustrated in the figure 1. The inlet 34 also comprises a flange 40 as attaching means for attaching the nozzle to the engine. The flange is provided with holes 42 for attachment screws. The flange surface is not flat but curved so as to conform with the surface of the cylinder liner. Thus, the flange has a partial cylindrical surface, which has its center of curvature on the side of the nozzle body 30.

[0036] In the embodiment of the figures 5 to 6 there is, in the flow channel 32, a flow conditioner 38 which starts directly at the inlet 34 and extends over the portion of a bend to a conical end part at the outlet 36. The conical end part constricts the cross-sectional area of the flow channel 32 and accelerates the velocity before exiting the nozzle.

[0037] In the flow conditioner 38 cross-sectional area of the flow channel 32 is comprised of multiple parallel flow conduits 32’. The conduits 32’ have a cross- sectional shape of a so-called honeycomb, that is a hexagon cross section. In practise, a substantially equivalent function can be obtained by generally polygon shape, like rectangular or square shape. It is also conceivable to provide circular cross-section to the conduits 32’. Advantageously the cross-sectional shape of an individual conduit 32’ is such that distance between center line of each adjacent conduit is the same, which improves the transition of flow from the flow conditioner 38 to the end part, where individual separate flows are united into single flow.

[0038] Like shown in the figure 3, when there are several separate flow conduits 32’ which single conduit 32’ has considerably smaller cross-sectional area compared the total cross-sectional area of the flow channel 32, intensity of turbulence of the flow in considerably decreased. The separate flow conduits 32’ are separated by substantially thin wall, thickness being less than 1 mm, but more than 0,3mm. This way the total cross sectional flow area of the flow conditioner 38 is substantially equal to cross sectional flow area of the flow channel 32. The flow conditioner 38 shown in the figure 3 comprises three parallel flow conduits 36’ which have at least one common intermediate wall between two flow conduits.

[0039] Length of the flow conditioner 38 and number of parallel flow conduits 32’ has a relationship to the radius of curvature R of the smooth bend. Increasing the length of the flow conditioner 38 and/or increasing the number flow conduits 32’ allows using smaller radius of curvature R. The general aim is to reduce flow interference in outlet flow. Suitable balance between the variables can be easily found by testing. The desired outcome of the solid jet can be evaluated visually. The embodiment shown in the figures 5 to 6 provides much more solid jet than the one in the figures 2 to 4. Therefore the embodiment of figures 5 to 6 is intended for use in practical application where the distance between the nozzle and the piston may be longer than in case of the embodiment of the figures 2 to 4. With the embodiment shown in the figures 5 to 6 the cooling oil jet can reach the piston as solid flow even when the piston is at its top dead center.

[0040] Also in the nozzle 26 according to the embodiment of figures 2 to 4 the angle of the bend is 90°, having possible deviations due to manufacturing and/or installation tolerances. The nozzle 26 is configured to direct the cooling oil flow in a direction of longitudinal axis of the cylinder liner 16, that is parallel to the liner of the engine. This way the flow jet hits a same spot of the piston regardless of the distance between the piston 14 and the nozzle 36. The flow conditioner 38 extends over the bend portion of the nozzle 26 from the inlet 34 to the conical end part 46. [0041] As it also come clear from the figures 5 to 6 the outlet part has a conical end part 46 which ends to an outlet 36 the cross-sectional area of which is smaller than the smallest cross-sectional area of the flow channel 36. The conical end part 46 start directly from the flow conditioner 38. Thus, the outlet is provided with an end part which constricts the cross-sectional area of the flow channel at the very end of the channel. This way the exit flow velocity of the cooling oil is accelerated before exiting the nozzle 26.

[0042] In all of the embodiments described here the nozzle is monolithic structure, which can be manufactured by additive manufacturing.

[0043] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the invention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.

Used references

10 an internal combustion piston engine

12 a cooling arrangement

14 a piston

14.1 a piston crown

14.2 a piston skirt

16 a cylinder liner

18 a block

20 a connecting rod

22 a gudgeon pin

24 an oil gallery

26 a nozzle

28 a cooling oil duct 30 a nozzle body

32 a flow channel

32’ conduits of the flow conditioner

34 an inlet 36 an outlet

38 a flow conditioner

40 attaching means

42 a screw hole

44 a constriction 46 a conical end part