EP0509956B1 - Arrangement for cooling a cylinder of an internal combustion Diesel engine - Google Patents

Description

The invention relates to an arrangement for the cylinder cooling of a reciprocating piston internal combustion engine of the diesel type, with at least one cylinder insert arranged in a cylinder block, which is surrounded by an annular space through which coolant flows and which is spanned by a cylinder cover through which coolant coming from the annular space flows, the coolant after flowing back through the cylinder cover via a cooler to the annulus.

In a known arrangement of this type (DE 1 942 846), the amount of coolant coming from the cooler flows successively first through the annular space, then through the cooling channels present in the upper thickened end of the cylinder insert and finally through the cylinder cover. The amount of coolant is adjusted so that at 100% load of the internal combustion engine the temperature of the inner surface of the cylinder insert, which forms the running surface for the working piston, is always slightly above the dew point temperature of water. This avoids that - due to the high sulfur content (4% and more) of the fuels used in diesel internal combustion engines today - sulphurous acid (H2SO3) and sulfuric acid (H2SO4) lead to corrosion on the combustion chamber walls. Of the two acids mentioned, the sulfurous acid is the more unpleasant one because the combustion product necessary for its formation, namely SO2, is produced in larger quantities and at lower temperatures than the SO3 necessary for the formation of sulfuric acid. The condensate of the sulfuric acid, which only appears in small quantities, can also be neutralized with lubricating oil additives. If the dew point temperature for water is undershot, considerable condensation of sulfuric acid is to be expected, which can result in adhesive wear on the running surface of the cylinder insert due to the destroyed lubricating oil film and on the running surfaces of the piston rings as well as on the running surface of the cylinder insert. In the known arrangement, falling below the dew point temperature can easily occur during part-load operation of the reciprocating piston internal combustion engine.

A further arrangement for cooling a cylinder block and a cylinder cover is known from EP 0 038 556. In this case, the cylinder cover and the cylinder block are cooled with a separate liquid flow and with a liquid flowing essentially transversely to the direction of travel of a cylinder, in order to keep the cylinder head at a lower temperature than the cylinder block. This prevents the engine from knocking and reduces the emissions of unburned hydrocarbonates. A disadvantage of this device can be seen in the fact that if it were operated with a fuel with a high sulfur content, a considerable condensation of sulfurous acid can be expected on the cylinder cover.

The invention has for its object to improve a cooling arrangement of the type mentioned in such a way that formation of sulfurous acid is reliably avoided even at part-load operation of the internal combustion engine.

This object is achieved according to the invention in that a line leading to the cylinder cover branches from the line leading from the cooler to the annular space, that a controller is provided which, depending on the load, distributes the coolant quantity coming from the line leading to the annular space and the line leading to the cylinder cover, and that a bypass line is connected to the coolant line between the cylinder cover and the radiator and opens into the line leading to the annular space below the branch of the line leading to the cylinder cover. Due to the line leading to the cylinder cover, part of the coolant quantity is always fed directly to the cylinder cover during operation of the internal combustion engine. Of the other part of the coolant quantity flowing to the annular space, which is supplemented by the quantity supplied via the bypass line and which is reduced compared to the known arrangements and has a higher temperature, now brings about less intensive cooling in the annular space, so that the tread temperature is raised. This ensures that a drop below the dew point temperature and thus also formation of sulfurous acid is avoided for all loads of the internal combustion engine. The running surfaces of the cylinder insert and the piston rings are no longer attacked by corrosion.

Fig.1

ein Fliessschema für das Kühlmittel an einem schematisch dargestellten Zylinder,

Fig.2

einen Axialschnitt durch einen Teil des Zylinders,

Fig.2a

das Detail A in Fig.2 in grösserem Massstab,

Fig.3

ein Temperatur-Diagramm, aufgetragen über die Höhe des Zylindereinsatzes, bei 100% Last und

Fig.4

ein Temperatur-Diagramm, aufgetragen über die Höhe des Zylindereinsatzes, bei 50% Last.

An embodiment of the invention is explained in more detail in the following description with reference to the drawing. Show it:

Fig. 1

a flow diagram for the coolant on a schematically illustrated cylinder,

Fig. 2

an axial section through part of the cylinder,

Fig.2a

the detail A in Fig. 2 on a larger scale,

Fig. 3

a temperature diagram, plotted against the height of the cylinder insert, at 100% load and

Fig. 4

a temperature diagram plotted against the height of the cylinder insert at 50% load.

In FIG. 1, 1 denotes a cylinder block of a multi-cylinder reciprocating piston internal combustion engine of the diesel type, 2 denotes a cylinder insert which is inserted in the cylinder block 1 and protrudes from the cylinder block with its upper end, and 3 denotes a cylinder cover spanning the cylinder insert 2. The three parts mentioned of the cylinder are cooled by a liquid coolant, for example water, for which a main circuit 5 and a secondary circuit 13 are provided. The main circuit 5 consists of a line 6 extending from the cylinder cover 3, a cooler 7 connected to the line 6, a coolant pump 8 and a line 9 which leads from the cooler 7 to the cylinder block 1 and in which the coolant pump 8 is arranged. Within the cylinder, between the connection of the line 9 to the cylinder block 1 and the connection of the line 6 to the cylinder cover 3, there is a flow path 10 shown in broken lines, which is described in more detail below with reference to FIG. The main circuit 5 also includes a bypass line 11 which bypasses the cooler 7. At the branch of the bypass line 11 from the line 6, a distribution valve 12 is arranged, which, depending on its temperature, divides the coolant coming from the valve cover 3 and flowing in the main circuit 5 into a quantity flowing into the cooler 7 and a quantity flowing through the bypass line 11. In the line 9 there is also a distribution valve 17, namely between the coolant pump 8 and the cylinder block 1. In the line 6 between the cylinder cover 3 and the distribution valve 12 and in the line 9 between the distribution valve 17 and the cylinder block 1 is a distribution line 6 'and 9' arranged to which the other cylinders, not shown, of the internal combustion engine are connected.

The secondary circuit 13 consists of a coolant pump 14 containing line 15 which branches off from the distribution line 6 'and opens into the distribution line 9'. From the distribution valve 17 branches off a line 16 which opens directly into the cylinder block 3 and in which the distribution lines 6 'and 9' corresponding distribution line 16 'is arranged. The distribution valve 17 is under the influence of a regulator 18, which is connected to the load of the internal combustion engine via a signal line 19 dependent target signal receives. In addition to the target signal, the controller also receives at least one actual value signal which is directly or indirectly dependent on the temperature of the running surface of the cylinder insert 2 and which is supplied via the signal line 20.

According to FIG. 2, the lower half of the cylinder insert 2 projects into the cylinder block 1, which, separated by a wall 1 ', has an upper space 22 through which coolant flows and a lower space 23 through which purge air flows. The cylinder insert 2 has, in its lower region and distributed over its circumference, a plurality of flushing slots 24 which let purge air from the purge air space 23 into the cylinder insert when the working piston 50, which is shown only rudimentary in its upper dead center OTP, near its lower dead center UTP exposes the flushing slots 24. The cylinder insert 2, the tread is denoted by 2 ', is provided at its upper end with the cylinder cover 3, in which a plate-shaped outlet valve 25 is arranged approximately in the center of the cylinder insert. Starting from the seat surface interacting with the exhaust valve 25, an exhaust duct 26 is provided in the cylinder cover 3, via which the exhaust gases are expelled by the piston 50 moving upward when the valve 25 is open. The machine shown is therefore a two-stroke internal combustion engine with longitudinal purging. It can be used to drive ships as well as to drive electrical generators. In addition to the exhaust duct 26, the cylinder cover 3 also has spaces 27 and 28 through which coolant flows.

Between the cylinder insert 2 and the opening 51 receiving it in the cylinder block 1, a sleeve 30 is arranged, which extends approximately in the central region of the cylinder insert over approximately half its length. The sleeve has a little on its outer surface projecting ring approach with which it is supported on a shoulder at the opening 51. The lower end of the sleeve 30 is held by a ring 31 while maintaining a distance from the cylinder insert. In the area of the upper end of the sleeve 30, the cylinder insert 2 is somewhat thickened, so that there is a narrow annular gap 32 between the upper end of the sleeve 30 and the adjacent outer surface of the cylinder insert, as shown in FIG. 2a. This design creates an annular space 33 between the sleeve 30 and the region of the cylinder insert 2 which is adjacent to it and which is essentially filled with stagnant coolant. With the dimensioning of the annular gap 32, the coolant temperature in the intermediate space 33 can be preset within certain limits. The intermediate space 33 can have a low flow, for which purpose a valve 33 'is provided in a drain line connected to the intermediate space, as shown in FIG. The valve 33 'also serves to empty the intermediate space 33.

The cylinder block 1 has in its wall above the room 22 a supply channel 34 for coolant, to which the end of the line 9 coming from the distribution line 9 'is connected in a manner not shown. The cylinder insert 2 is thickened in the form of a collar at its upper end and, in this thickened region, has cooling bores 35 which run obliquely in a manner known per se and are uniformly distributed over the circumference of the cylinder insert. A support ring 36 extends between the underside of the collar-shaped thickening of the cylinder insert 2 and the cylinder block 1, leaving an annular space 37 between itself and the cylinder insert 2 and an annular space 38 between itself and the upper half of the sleeve 30. The coolant from line 9 therefore initially flows in via cooling channel 34 the annular space 38, then into the annular space 37 and from there into the cooling holes 35 of the collar-shaped thickening.

At the upper end of the cooling bores 35, these are guided radially outward and connected to a line 39 which opens into the space 27 of the cylinder cover 3. Line 16 is also connected to line 39 and branches off from line 9 at distribution valve 17.

During operation of the reciprocating piston internal combustion engine, the coolant heated in the cylinder flows via line 6 and the distribution valve 12 to the cooler 7, in which the absorbed heat e.g. is released to seawater flowing on the secondary side. The coolant cooled in this way is conveyed by the pump 8 via line 9 to cylinder block 1 and via line 16 to cylinder cover 3. The coolant quantities flowing to the cylinder block 1 and the cylinder cover 3 are set by the distribution valve 17, which is controlled by the controller 18 as a function of the load. A small amount of higher temperature coolant is always added to the amount of coolant flowing to the cylinder block 1 via the line 15 of the secondary circuit 13 because it has not been cooled in the cooler 7.

The coolant flowing to the cylinder block 1 first reaches the annular space 38 via the cooling channel 34. Because of the coolant stagnating in the intermediate space 33, a moderate heat transfer from the cylinder insert 2 to the coolant takes place here. In the annular space 37 above the sleeve 30, the heat transfer is then more intensive because the flowing coolant comes into contact with the cylinder insert 2 here. The same then also applies when the coolant flows through the cooling bores 35. After leaving the cooling bores 35 and before the coolant enters the space 27 of the cylinder cover 3, the reheated coolant becomes in cooler coolant from line 16 is mixed into line 39.

The circuit shown in FIG. 1 thus supplies the cylinder block 1 with a reduced amount of coolant, which is relatively warm due to the admixture of coolant from the line 15 and thus reduces the cooling effect on the cylinder insert 2 accordingly. The space 27 in the cylinder cover 3, however, is always acted upon by the full amount of coolant of a relatively cool temperature. In addition to the reduction in the cooling effect due to the admixture of coolant from the line 15, the cooling effect is weakened by the load-dependent adjustment of the amount of coolant by means of the distribution valve 17. So that the temperatures on the tread 2 'of the cylinder insert 2 are raised compared to the previously usual cooling. This can be seen from Figure 3 for an engine load of 100%. In FIG. 3 the solid line B shows the profile of the tread temperature with a previously customary cooling, whereas the dash-dotted line C shows the profile of the tread temperature for the arrangement according to the invention. The dashed line D shows the course of the dew point temperature for water. From the course of line C there is a clear distance between the tread temperature and the course of the dew point temperature. Because of the small distance between line B and the dew point temperature line D, the tread temperature in FIG. 3 shifts to the right in the known arrangement at partial load of the internal combustion engine, so that the dew point temperature line D falls below, as is the case for 50% load in FIG. 4 is shown. With the new cooling arrangement, however, the tread temperature (line C) remains above the dew point temperature line D even at partial load.

The structural design of the cylinder block, cylinder insert and support ring in FIGS. 3 and 4 thus corresponds to the prior art.

In a departure from the illustration in FIG. 1, it is also possible to arrange the pump 8 of the main circuit in the line 6 upstream of the distribution valve 12 and then to have the line 15 of the secondary circuit 13 branch off between this pump and the distribution valve 12. In this case, the pump 14 of the secondary circuit can be omitted and is replaced by a throttle point in line 15.

If the internal combustion engine is equipped with a turbocharger, this can also be cooled by a subset of the coolant from the main circuit 5. For this purpose, a coolant line containing the turbocharger will be branched off on the line 9 between the coolant pump 8 and the distribution valve 17 and open into the distribution line 6 '.

Claims (2)

1. An arrangement for cooling the cylinders of a reciprocating internal combustion engine of the diesel type, comprising at least one cylinder liner (2) which is disposed in a cylinder block (1), is surrounded by a coolant-conveying annular chamber (38), and is surmounted by a cylinder head (3), through which flows coolant originating from the annular chamber (38) and flowing along the cylinder liner (2), the coolant flowing back to the annular chamber (38) via a cooler (7) after flowing through the cylinder head (3), characterised in that a line (16) leading to the cylinder head (3) branches off from the line (9) leading from the cooler (7) to the annular chamber (38), in that a controller (18) is provided which, in dependence on the internal combustion engine load, divides the coolant coming from the cooler over the line (9) leading to the annular chamber (38) and the line (16) leading to the cylinder head (3), and in that a bypass line (11) is connected to the coolant line (5) between the cylinder head (3) and the cooler (7) and downstream of the branching off of the line (5) leading to the cylinder head (3) leads into the line (9) leading to the annular chamber (38).
2. An arrangement according to claim 1, characterised in that the central zone of the cylinder liner (2) is surrounded by a sleeve (30) which is approximately half as long as the cylinder liner (2) and which between itself and the cylinder insert (2) leaves free an annular gap (33) which in the region of the top end of the sleeve (30) communicates via a restrictor (32) with the annular chamber (38) and which is filled with stagnant coolant during operation of the engine.

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