WO2004099583A1

WO2004099583A1 - Method and arrangement for cooling of a cylinder lining

Info

Publication number: WO2004099583A1
Application number: PCT/SE2004/000643
Authority: WO
Inventors: Magnus Hagberg; Zoltan Kardos
Original assignee: Scania Cv Ab (Publ)
Priority date: 2003-05-06
Filing date: 2004-04-28
Publication date: 2004-11-18
Also published as: SE524977C2; SE0301302L; SE0301302D0

Abstract

Method for external cooling of a cylinder liner (1) of a liquid-cooled combustion engine whereby thermal energy is transferred from the cylinder liner to coolant (4) of the engine’s ordinary cooling system. The method is distinguished particularly by the fact that the transfer takes place in two successive stages whereby the cylinder liner (1) is cooled as a first stage by a first cooling medium (5) which is itself cooled as a second stage by said coolant (4). The invention also relates to a device for cylinder liner cooling.

Description

Method and arrangement for cooling of a cylinder lining

Background

1. Technical field

The present invention relates to a method for external cooling of a cylinder liner of a combustion engine cylinder whereby thermal energy is transferred from the cylinder liner to the coolant of the engine's cooling system.

The invention also relates to a device for external cooling of a cylinder liner.

2. Description of the state of the art

Techniques of substantially the kind indicated above are known whereby thermal energy from combustion in the cylinder heats the cylinder liner and is transferred to coolant (sometimes mainly water) of the engine's cooling system by external contact with the cylinder liner.

The possibilities of this way of cooling away the thermal energy arising from combustion are limited, thereby imposing restrictions on permissible temperature in the combustion chamber. This limitation is because the heat transferred to the coolant is limited, the boiling point of the coolant is only about 100°C (in the case of water) and very substantial impairment of the heat transfer occurs when vaporisation takes place at the contact with the coolant, where vaporisation is also for other reasons particularly undesirable or unacceptable. Another desideratum is to limit the total liquid volume of the cooling system.

A practice known from GB-709 675 in the case of combustion engines which are air- cooled by means of cooling flanges and have two pistons and a common combustion chamber is for the intermediate wall between the cylinders to be cooled by means of sodium which vaporises, expands and thereafter condenses in an expansion chamber which is cooled by means of cooling flanges. Although that method makes it possible to reduce the necessary wall thickness, it still results in relatively ineffective air cooling.

A practice known from GB-2 004 323 is for a cylinder and exhaust ducts to be air- cooled by means of cooling flanges and surrounded by spaces filled with sodium which during operation melts and is intended to damp noise from the combustion chamber in the cylinder without appreciably hindering heat conduction to the cooling flanges.

However, that known technique is not suited to achieving more effective cooling of liquid-cooled combustion engines.

One object of the present invention is to provide more effective cooling of a cylinder of a liquid-cooled combustion engine and thereby be able to allow a higher temperature in the combustion chamber of the cylinder.

Summary of the invention

The object of the present invention is achieved by means of a method and a device according to the independent claims.

Further advantages are achieved with the versions according to the respective dependent claims.

Brief description of the drawing

The invention is described in more detail below in connection with embodiments and the attached drawing, in which: - Fig. 1 depicts schematically a central axial section through a first embodiment of a device according to the invention, with a piston which is not depicted in section. Detailed description of preferred embodiments

Ref. 1 denotes a cylinder liner of a liquid-cooled combustion engine whereby the cylinder liner 1 constitutes at its upper portion 2 a combustion chamber 3. For external cooling of the cylinder liner, thermal energy (heat) generated in the combustion chamber is intended to be transferred from the cylinder liner to the coolant 4 of the engine's ordinary cooling system, which is only schematically represented in principle in the form of the coolant 4.

According to the invention, there are devices for effecting said transfer in two successive stages whereby a first cooling medium 5 is arranged to cool the cylinder liner externally as a first stage and to be itself cooled by said coolant as a second stage.

According to a preferred embodiment, the first cooling medium 5 has a substantially higher melting point and also boiling point than the coolant of the engine's ordinary cooling system. One example is sodium with melting point 97.8°C and boiling point 890°C. Other examples are other alkali metals. Alloys are also conceivable. The advantage is that the boiling point is higher than operating temperatures occurring in the combustion chamber.

According to one version, the engine is a diesel engine.

According to the version depicted in Fig. 1, the first cooling medium 5 is arranged in a jacket 6 around the cylinder's combustion region to provide heat transfer contact with, on one side, the cylinder liner and, on the other side, said coolant, which is arranged to surround at least parts of the jacket.

According to a preferred version, the first cooling medium comprises a sodium-based substance which, at the temperatures to which it is heated by its contact with the cylinder liner adjacent to the combustion chamber, is molten when the engine is in full operation. According to a preferred version, the first cooling medium, such as said substance, is intended to at least partly undergo successive alternating phase transformations, in principle from solid to liquid as the first stage and from liquid to solid as the second stage, thereby enabling the cooling medium by phase transformation to extract more thermal energy from the cylinder liner than would be extracted by pure temperature rise of the cooling medium.

It is also preferred that there be devices, which are exemplified below, for forcing the first cooling medium to pass axially along the cylinder liner and for forcing the first cooling medium to pass at least a surface 7 which is in heat transfer contact with the coolant. According to the version depicted in Fig. 1, there is a pump means 8 comprising an annular element 9 which is situated in the jacket and which runs in the circumferential direction of the cylinder liner in order to effect said forced passage. The annular element 9 is arranged for axial movement in an inner space 10 of the jacket which extends axially and in the circumferential direction of the cylinder liner, which inner space communicates with an outer space 11 of the jacket, which outer space is arranged to be cooled by said coolant, so that the first cooling medium is arranged to be pumped between said spaces and be thereby alternately heated and cooled. The movements of the annular element are illustrated schematically by two- directional arrows 12, and the flow of the first cooling medium is depicted schematically by two-directional arrows 13. According to the version depicted, said spaces 10,11 are constituted by means of an axial intermediate wall 14 which runs in the circumferential direction in the jacket and delineates an upper aperture 15 and a lower aperture 16 whereby the first cooling medium is intended to pass to and fro.

It is also preferred that existing pump means such as the annular element 9 depicted be arranged to follow the axial reciprocating movements of the piston 17 arranged in the cylinder liner. Said pump means may be operated under mechanical, magnetic or electrical control.

The method, like the functioning of the device, according to the invention has probably been substantially indicated above. Cooling the cylinder liner in two liquid stages achieves very effective cooling which means that a higher temperature (combustion temperature) can be allowed in the combustion chamber. The heat transfer in the boundary layer between a liquid and the surface of a solid body is normally very good and effective. Forced passage of the cooling medium maintains a high temperature difference which makes the heat transfer more effective.

Using phase transformations which respectively absorb energy and release energy enables more heat to be extracted from the cylinder liner than would be extracted by pure temperature rise of the first cooling medium.

It is in many cases practical to adapt the composition and characteristics of the first cooling medium to the cooling situation so that it becomes entirely molten upon contact with the cylinder liner and forms a partly solidified slurry during and after ^• cooling by means of the coolant. Slurry means a mudlike mixture of solid and liquid phases.

The invention was described above in connection with examples of embodiments. Further embodiments and minor modifications/adjustments are of course conceivable without departing from the concept of the invention.

Claims

1. A method for external cooling of a cylinder liner of a liquid-cooled combustion engine whereby thermal energy is transferred from the cylinder liner to coolant of the engine's ordinary cooling system, characterised in that the transfer takes place in two successive stages whereby the cylinder liner (1) as a first stage is cooled by a first cooling medium (5) which as a second stage is cooled by said coolant (4).

2. A method according to claim 1, characterised in that the first cooling medium (5) has a substantially higher melting point and also boiling point than said coolant (4).

3. A method according to claim 1 or 2, characterised in that said first cooling medium undergoes successive alternate phase transformations, in principle from solid to liquid as the first stage and in principle from liquid to solid as the second stage.

4. A method according to claim 2 or 3, characterised in that the first cooling medium is arranged in a jacket (6) around the cylinder's combustion region (3) for heat transfer contact with, on one side, the cylinder liner and, on the other side, said coolant.

5. A method according to claim 1 , 2, 3 or 4, characterised in that the first cooling medium comprises a sodium-based substance.

6. A method according to claim 1, 2, 3, 4 or 5, characterised in that the composition and characteristics of the first cooling medium are adapted to the cooling situation so that it is in principle entirely molten upon contact with the cylinder liner and forms a partly solidified slurry during and after cooling by the coolant.

7. A method according to claim 1, 2, 3, 4, 5 or 6, characterised in that the first cooling medium is forced to pass axially along the cylinder liner.

8. A method according to claim 7, characterised in that the first cooling medium is forced to pass at least one surface (7) for heat transfer contact with said coolant.

9. A method according to claim 7 or 8, characterised in that the forced passage is effected by means of pump means (8, 9) which preferably follow the axial reciprocating movements of the piston (17).

10. A device for external cooling of a cylinder liner of a liquid-cooled combustion engine whereby thermal energy is transferred from the cylinder liner to coolant of the engine's ordinary cooling system, characterised in that there are devices (4, 5, 6, 7) for effecting said transfer in two successive stages whereby a first cooling medium (5) is arranged to cool the cylinder liner (1) as a first stage and is to be cooled by said coolant (4) as a second stage.

11. A device according to claim 1, characterised in that the first cooling medium (5) has a substantially higher melting point and also boiling point than said coolant (4).

12. A method according to claim 10 or 11, characterised in that the first cooling medium is arranged in a jacket (6) around the cylinder's combustion region (3) for heat transfer contact with, on one side, the cylinder liner and, on the other side, said coolant, which surrounds at least parts of the jacket.

13. A method according to claim 10, 11 , or 12, characterised in that there are devices (8, 9) for forcing the first cooling medium to pass axially along the cylinder liner.

14. A method according to claim 13, characterised in that there are devices for forcing the first cooling medium to pass at least one surface (7) which is in heat transfer contact with the coolant.

15. A device according to claim 13 or 14, characterised in that there are pump means (8, 9) arranged in the jacket for effecting the forced passage.

16. A device according to claim 15, characterised in that said pump means are arranged to follow the axial reciprocating movements of the piston.

17. A device according to claim 15 or 16, characterised in that said pump means are arranged for axial movement in an inner space (10) of said jacket which extends in the circumferential direction of the cylinder liner, which inner space communicates with an outer space (11) arranged to be cooled by said coolant, so that the first cooling medium is arranged to be pumped between said spaces and be thereby alternately heated and cooled.

18. A device according to claim 15, 16 or 17, characterised in that said pump means comprise an annular element (9) running in a circumferential direction of the cylinder liner.

19. A device according to claim 15, 16, 17 or 18, characterised in that said pump means are operated under mechanical, magnetic or electrical control.

20. A device according to any one of claims 10-19, characterised in that the first cooling medium takes the form of a sodium-based substance.

21. A device according to any one of claims 10-20, characterised in that the first cooling medium is arranged and intended to undergo successive alternate phase transformation, in principle from solid to liquid as the first stage and in principle from liquid to solid as the second stage.

2. A device according to claim 21, characterised in that the composition and characteristics of the first cooling medium are adapted to the cooling situation so that in principle it is entirely molten upon contact with the cylinder liner and forms a partly solidified slurry during and after cooling by the coolant.