DK170447B1 - Process and internal combustion engine - Google Patents

Description

DK 170447 B1 i

The invention relates to a method for cooling a cylinder liner in an internal combustion engine, in particular a large two-stroke main engine in a ship, in which the liner in its upper part has several cooling surfaces distributed along the circumference of the liner which are cooled by cooling water to dissipate heat from the liner's running surface.

In a large two-stroke internal combustion engine, the upper portion of the casing, which usually protrudes from the cylinder portion and is tensioned down against it by means of a cover, is very thermally and mechanically stressed by the heat and pressure resulting from the combustion. The temperature level on the inner casing surface of the cylinder casing for the piston is of crucial importance for the casing's life and thus also for the economy of the diesel engine. If the temperature of the runner surface becomes too high, heater cracks will occur in the liner and if the temperature becomes too low, sulfuric acid from the combustion products can condense on the running surface, causing increased wear due to corrosive degradation of the liner material and degradation of the lubricating oil film on the running surface.

The temperature of the tread will normally vary with the load of the engine, and since the engine must be able to run for extended periods of time at both high and low loads, the linings are traditionally designed such that the temperature of the tread plate 25 at the maximum load of the engine is close to the maximum permissible temperature. The high temperature level allows, at partial load, to maintain sufficiently high temperature that acids do not condense on the running barn.

The cylinder lubricating oil and the lining material are affected by the high temperature at full engine load, and raising this temperature can lead to breakdown of the lubricating oil and permanent damage to the lining material. in the form of the above-mentioned heater cracks. The current cooling method thus in practice limits the power produced in the DK 170447 B1 2 cylinder, unless a certain risk of acid condensation is accepted at low load.

This problem has been solved by controlling the temperature of the running surface by regulating the flowing amount of cooling water. The cooling water and thus the cooling surfaces usually have a temperature of about 70 ° C. Experiments with water flow control have shown that a 50% reduction in water flow can lead to a temperature rise of approx. 10 ° C on the running surface. A temperature increase of only 10 ° C at low engine load provides very limited opportunities to increase the heat dissipation at high load, and therefore, large limitations of low flow water flow must be made to have a noticeable effect at high load.

15 A small water flow entails the serious risk that the cooling water over certain areas of the cooling surfaces becomes largely stagnant, leading to microcookings in the water immediately outside the cooling surface. The microcookings will lock the temperature of the heat sink at a level that depends on the operating pressure of the cooling water, because the heat must be dissipated by steam. At a typical cooling water pressure of from 2-3 bar, the temperature of the water vapor and thus also the cooling surface will be from 120-130 ° C. Such an increase in temperature of from 50 to 60 ° C of the cooling surface leads partly to the progressive propagation of the microcooking area and partly to local overheating of the adjacent area on the running surface. Therefore, a regulation of the water flow entails a risk of damage to the upper part of the casing, where the heat load 30 is greatest.

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The invention has for its object to provide safe cooling of the cylinder liner along its entire height and over a wide load range of the engine.

This is achieved by a method which according to the invention is characterized in that the intensity of cooling is varied according to the heat load on the casing by directing the cooling water to selected cooling surfaces whose number and / or distance from the running surface is adjusted to the actual heat load. .

For example, if the load of the engine increases, the heat input to the running surface and thus the need for cooling it will increase, so that the cooling intensity must be increased, which can be done by directing the cooling water to cooling surfaces which are closer to the running surface, so that the temperature gradient between the running surface and the cooling surface becomes larger and the amount of heat dissipated increases. The cooling water can also be directed to several cooling surfaces, which increases the heat dissipation.

In case of decreasing engine load, cooling surfaces located at a greater distance from the running surface can be selected and / or the number of cooling surfaces can be reduced. This cooling intensity control can be made without changing the water flow, thereby eliminating the risk of microcooking.

The variable cooling, depending on the engine load, also provides a very uniform temperature on the running surface over the entire engine load range.

Therefore, the temperature of the running surface can. is selected at a suitable distance from both the acid dew point and the temperature at which the lubricating oil or lining material shows initial damage. The uniform lubrication and temperature conditions significantly increase the life of the casing.

Of course, it is also not necessary to change the design of the casing if the existing motor is modified for continuous operation at another load 30 (derating or unprating). The load-dependent control of the cooling intensity also enables an increase in the heat load on the casing beyond what is possible today, which allows the design of engines with higher power per unit. cylinder.

DK 170447 B1 4

It is preferred that the cooling water is directed to selected groups of cooling surfaces, where the cooling surfaces in groups with several cooling surfaces have substantially the same course with respect to the running surface, and that the cooling water flow is regulated such that the individual group is either fully open or completely closed for flow. . The temperature load on the casing is decreasing in direction away from its upper end, and some of the cooling surfaces must therefore extend so inclined with respect to the running surface that they lie in a downward direction away from it. The grouping of the cooling surfaces so that the surfaces of each group have the same course counteract imbalances in the cooling of the casing when switching on or off a group. Since the stresses in the casing material depend on both the thermal and mechanical stresses, the grouping and the consequent uniform cooling of the casing will help ensure that the casing's ability to absorb mechanical stresses does not vary substantially along the cross-section perpendicular to the casing's longitudinal axis. By leaving the 20 individual group either fully switched on or off, a well-defined predetermined cooling effect is achieved on the casing depending on the current combination of switched groups, which makes it easy to program a control of the cooling currents depending on the engine load.

25 The heat incident on the running surface falls away from the upper portion of the casing because the pressure and temperature of the combustion gas fall during the downward working layer of the piston. Thus, in a casing portion located below the upper portion, the cooling requirement may become so low that there is no risk of microcooking on the associated cooling surface. The cooling intensity at this surface can therefore conveniently be adjusted by changing the flow of cooling water, which gives the advantage that the cooling water flow to the cooling surfaces of the upper portion is not limited by the relatively low cooling demand at the cooling surface of the underlying portion.

Abnormal operating conditions can be suitably compensated for by measuring and recording the actual temperatures at the running surface, comparing the recorded temperatures with predetermined limit values and adjusting the cooling intensity to the nearest new level if a limit value is exceeded. The limit values can be set as an upper and a lower deviation from the desired mean temperature of the liner, and the measurement of the actual temperatures makes it possible to simply correct for changed heat loads, for example due to altered ambient conditions such as air and cooling water temperatures. which can provide load-dependent variations in the heat input of the running surface. With this approach, the temperature control becomes more finely labeled and accurate than can be obtained from a predetermined cooling regulation based on experience values for the relationship between the heat load and the engine load. However, the relationship between the choice of active cooling surfaces and the cooling intensity must be predetermined.

In order to prevent the automatic cooling control from detecting actual malfunctions in the engine, an alarm signal may be issued if the adjustment of the cooling intensity is due to a local temperature change on the running surface. Such a local change may be due, for example, to poor condition of a piston ring or other mechanical failure of a motor component. The alarm signal allows the 30 operating personnel to make an independent assessment of whether the failure component needs to be repaired or whether it is safe to continue with increased cooling intensity.

The optimal control of the temperature of the liners 35 is achieved only when the cooling intensity is individually regulated for each cylinder lining, so that individual variations in the working conditions of the cylinders can be compensated.

The invention also relates to an internal combustion engine, in particular a large two-stroke main engine in a ship, with several 5 cylinder liners, each of which is clamped down against the cylinder portion by a cover which, together with the casing and the associated piston, delimits an internal combustion chamber where the casing in its the upper portion has several water-cooled cooling surfaces distributed according to its circumference to dissipate heat from the casing's running surface, characterized in that the cooling surfaces are divided into groups, each having a separate cooling water supply passage and a regulating means for controlling the water flow in the passage.

The groups located in the upper portion of the casing will typically have a regulating means in the form of a shut-off means which can open or close completely to the water flow, while groups located below the upper portion may have a valve for controlling the flow rate.

In a preferred embodiment, the groups 20 are mutually at least part of the extent of the cooling surfaces in the axial direction of the casing at different distances from the running surface. This allows for the control of the cooling intensity in relatively fine jumps, because the cooling effect of a larger distance from the running surface 25 is limited by the smaller temperature gradient between the running surface and the cooling surface of the group. For cooling surface groups located inside the casing material, the radial separation of the groups also offers the advantage that the mechanical strength of the casing is not attenuated by the cooling surfaces.

In a preferred embodiment, the liner is designed such that the first group comprises several elongated, elongate cooling channels distributed along the liner substantially extending upwardly and inwardly toward the tread surface that a second group comprises several liner members. circumferentially spaced elongated cooling ducts extending substantially upwardly and inwardly from the casing toward the tread surface, preferably such that the upper portion of the ducts 5 is at a greater distance from the tread surface than the corresponding portion of the ducts in the first group, and that a the third group comprises a single circumferential cooling surface at the outside of the casing radially adjacent to the channels of the first and second groups, and preferably a fourth group with a single circular cooling surface at the outside of the casing located axially below the other groups.

It is known that a cylinder liner for a large two-stroke internal combustion engine in its upper with greater wall thickness can have a single group of elongated cooling ducts extending substantially upwardly and inwardly toward the running surface at such an angle. relative to the cylinder axis, that the cooling ducts in their entirety form a hyperboloid. These 20 ducts are closest to the running surface in the upper section of the casing, where the heat load is greatest, and the slopes of the ducts ensure that the cooling intensity in the downward direction decreases roughly as the heat is applied. The use of an additional group 25 of elongated cooling ducts within the casing wall makes it possible to achieve a large jump in cooling intensity by engaging the second group. If the channels in their upper section are radially outside the channels in the first group, the change in cooling intensity at the switch-on becomes smaller. Thus, in designing a new cylinder liner for a particular cylinder performance, the course of the channels can be determined so that precisely the desired difference in cooling intensity is obtained when the channels are switched on.

Constructively, it is very simple to provide a single circular cooling surface at the outside of the casing, and such a cooling surface as far as possible away from the running surface enables a fine adjustment of the cooling intensity.

As mentioned above, the cooling requirement is less at a greater distance from the upper portion of the casing, so that if desired here the cooling can be done only by means of a single circumferential cooling surface at the outside of the casing.

An example of an embodiment of the engine according to the invention is explained in greater detail with reference to the schematic drawing, in which FIG. 1 and 2 show radial sections through the upper part of a cylinder liner along lines I-I and II-II in FIG. 3, FIG. 3 on a smaller scale cross-section through the liner along line III-III of FIG. 1 and 2 and 15 FIG. 4 is a wiring diagram for cool charge groups in the casing.

In FIG. 1 and 2, a section of a top section -1 of a cylinder liner is shown for a large two-stroke cross-head motor. Such an engine is very well known both as a 20 main engine in a ship and as a stationary power producing engine and should not be described in more detail here but may be, for example, MAN B&W DIESEL and can typically have the type designation L60MC, where 60 indicates a cylinder bore of 60 cm. The upper section 1 is provided for clamping between a cylinder cover and the upper side of the cylinder portion of the engine mounted on an engine rack and an underlying bottom frame. The section 1 has a downwardly facing lower abutment surface 2 which rests against the surface of a corresponding abutment on the upper side of the cylinder portion 30, and an upwardly annular upper abutment surface 3 for supporting the cylinder cover (not shown) which, by means of a cover pin, is pressed down against the cylinder portion with a force. that is greater than the largest upward 35 force on the cover during combustion. The upper section 1 has a large wall thickness DK 170447 B1, so that it can transfer the large axial directional forces from the cover to the cylinder part and can withstand the radially outward pressure in the combustion chamber and the temperature load therefrom. In a motor 5 with a cylinder bore of 60 cm, the upper section 1 can have an axial length of approx. 70 cm and a lower section 4 can have an axial length of approx. 1.8 m. If, for example, the bore is 90 cm, the corresponding lengths are approx. 105 cm for the upper section and 250 cm for the lower 10 section.

The lower section 4 is not burdened by the axial compressive forces from the cover and the pressure effect from the combustion gases is also less. The section 4 therefore has substantially less wall thickness than the upper section.

15 The circular cylindrical inside of the casing forms a · running surface 5 for the piston rings on the piston which is housed in the casing. The wall thickness of the lower section is sufficient to absorb the steering forces from the piston, and at the bottom of the lower section there are a series of purging air ports around the periphery of the casing which are exposed when the piston is near the bottom dead point position, so that purging air can flow. up through the combustion chamber and out through the exhaust passage in the cover, and charge air can fill the combustion chamber 25 at the same time as the compression stroke is started.

The liner is most thermally loaded in an upper portion 6 which extends axially from the upper abutment surface 3 to the upper edge of a recess 7 incorporated in the lower portion of the upper section 1 on the outside of the liner 30. A first group of cooling ducts 8 is drilled from a projecting surface 9 at the upper end of the recess into the upper wall portion of the liner so that the ducts 8 extend inclined inwardly toward the running surface 5 and lie obliquely relative to a radial section through the casing. For convenience, the channels 8 in FIG. 1 and DK 170447 B1 10 2 as if they were in the radial section. In FIG. 3 it is seen that the cooling ducts are evenly distributed along the periphery of the casing and that the number of bores is sufficiently large * to provide a substantially even cooling of the running surface 5 5.

The cooling ducts 8 are blind bores and in each bore is inserted a pipe 10 with smaller outer diameters than the inner diameter of the duct, so that there is an annular cooling gap between the duct and the duct wall. The lower end 10 of the tube has a protruding flange abutting a shoulder portion 11 in the channel 8. The upper portion of the tube is bent in a corrugated shape so that the top opening 12 of the tube is centered relative to the bore. The tube may be retained in the liner by a tensioning ring 15 abutting the tube flange. After inserting the tube 10, the duct 8 is closed downwardly by a body * 13 which may be a plug or a threaded cover. The channel 8 communicates with a radial inlet channel 14 and a radial outlet channel 20 15 located at a level above the shoulder 11. The access channel opens into the lower section of the cooling channel 8 below the shoulder 11, and as the flange of the tube 10 abuts the shoulder and blocks it. annular channel around the tube, the entrained water is forced to flow upwardly 25 within the tube 10 and further through the annular space around the tube 10 down to the outlet channel 15.

Another group of elongated cooling ducts 8 'is formed in itself in the same way as the cooling ducts of the first group, and the second group of channel elements 30 shown in FIG. 2 is designated by the same reference numerals as in FIG. 1 simply applied a mark.

The cooling ducts 8 'in the second group are drilled at a smaller angle relative to the running surface 5, so that the upper sections 16' of the channels are at a greater distance from the running surface than the corresponding section 16 of the channels DK 170447 B1 11 8 in the first group, which causes the channels 8 'to give less cooling intensity than the channels 8.

A casing 17 surrounds the upper portion of the casing and is spaced from a circular cooling surface 18 extending parallel to the casing axis, so that an annular cooling chamber 19 is formed between this casing and the casing 19. As the casing surface 18 acts at the outer periphery of the casing, furthest away from the running surface 5, and the temperature gradient out to the surface 18 is therefore 10 least possible. The cooling surface 18 is the only surface in a third group.

Since the heat load is greatest in the upper portion 6 of the casing, this is also where the greatest variations in the heat load occur when the engine load 15 changes. The three batches of cooling surfaces of the upper part, each with its own cooling intensity, enable a precise adjustment of the cooling intensity to the immediate need. In the area below the upper portion, the cooling requirement is substantially smaller and the cooling can therefore be handled with a single circular 20 cooling surface 20 at the outside of the casing. This surface is the only cooling surface in a fourth group.

The recess 7 is designed such that the cooling surface 20 is inclined upwardly towards the running surface 5. Since the cooling intensity of the surface depends on the distance inwards 25 to the running surface 5, the inclined course of the surface 20 ensures that its cooling effect grows somewhat as the rise towards the casing upper end of the heat incident on the running surface 5. In the upper portion 6 the inclined bores in the first and second groups ensure a corresponding adaptation to the upwardly increasing heat incident.

An annular sheath 21 surrounds the recess 7 so that a cooling chamber is formed between the sheath and the surface 20. The sheath 21 extends upwardly past the surface 9 35 and over a central portion 22 provided with circular grooves for distributing cooling water between the ducts in the same group. The grooves are radially outwardly closed by the sheath 21. A series of sealing means 23 located in associated grooves abut the inside 5 of the sheaths and provide the necessary sealing between the cooling surfaces and the grooves on the periphery of the casing.

Inlet and outlet of cooling water for the individual groups takes place through pipes which are fixed on the outside of the sheaths 17 and 21 next to through holes in them.

10 The drawing shows only one inlet and outlet pipes for each group, but it is of course possible to use several sets of pipes for each group, since the sets can then be distributed along the periphery of the casing so that there is no long flow path from one inlet to a 15 cooling channel access channel.

An annular distribution channel 24 at the periphery of the casing connects the inlet channels 14 of the first group with each other and with an inlet pipe 25. The outlet channels 15 pass through a 20 inlet connecting duct 26 in connection with an outlet pipe 27. Similarly, the inlet channels 14 'are through a distribution channel 28 is connected to flow with an inlet pipe 29, and the outlet channels 15 'are through a connecting channel 30 in flow communication with an outlet pipe 31. The cooling chamber 19 communicates with an inlet pipe 32 at the bottom of the chamber and an outlet pipe 33 at the chamber top. The cooling chamber in the recess 7 communicates with an inlet pipe 34 and an outlet pipe 35, also positioned at the bottom and top of the chamber, respectively.

The flow of water in the four groups is regulated by means of valves controlled by a valve in FIG. 4, as shown in dashed lines, is connected to each 35 valve in a controlled manner. The first three groups of cooling surfaces located in the upper portion 6 can be provided by means of 3/2-way valves 37, 38 and 39, ie. valves with 3 connections and two positions, fully switched on or off, so that the entire flow of water flows either through or outside the group.

5 With those of FIG. 4, the entire flow of water is passed through all three groups, so that the cooling intensity in the upper part 6 is maximum. Each discharge pipe 27, 31 and 33 contains a non-return valve, respectively.

40, 41 and 42, which prevent cooling water from flowing backwards 10 into a disengaged group.

The fourth group with the cooling surface 20 must remove such relatively limited quantities of heat that there is little risk of microcooking at the cooling surface, which allows the cooling intensity to be controlled by means of an infinitely adjustable control valve 43 which can direct part of the water flow outside the fourth The exhaust pipe 35 also contains a check valve 47.

It is possible to assemble several of the valves into a single valve block where the valve has an appropriate number of inlets and outlets and valve positions so that the above-mentioned control of the water flow is achieved.

The calculator 36 can be supplied through a line 44 with information on the instantaneous load of the motor and on this basis provide control signals to the valves in accordance with a predetermined relationship between the load and the need for cooling.

It is also possible to place temperature sensors 45 at the running surface 5 and through a conduit 46 to supply information to the calculator about the actual temperature of the casing at the selected measurement points. In the latter case, the calculator contains predetermined information on the cooling intensity levels that result from the possible combinations of active cooling groups as well as information on permissible deviations from the desired lining temperature. If the measured temperature passes one of these predetermined limit values, the calculator switches the cooling system to the nearest level of cooling intensity.

The sensors 45 may be located in the axial direction of the casing at different distances from the abutment surface 3 and at the same axial level there may be several sensors distributed along the circumference of the casing. It is preferred that some of the sensors be at such a distance from the surface 3 that the running surface next to the sensors is covered by the piston rings. If the sensors 10 distributed around the perimeter measure different temperatures, this may be an indication of a piston ring failure. There may also be at least one sensor positioned at the point of the casing which is experientially exposed to the highest temperature.

Hereinafter, an example of load-dependent dependent or disengaging of the three heat sink groups in the upper portion 6 of the casing is described.

Engine load in% Group 1 Group 2 Group 3 95-105 + + + 20 85-95 + + 75-85 + - + 60-75 + - - 40-60 - + + 20-40 + 25 0-20 + In the diagram a load of 100% corresponds to the motor running at 100% nominal mean pressure and 100% nominal rpm, which is usually referred to as the nominal L1 point of the motor. The MCR point of the motor may not be higher than the L1 point, but for example, by means of derated motors it is well known to place the MCR point at a load corresponding to, for example, 85% of the L1 point. The diagram immediately shows that it is not necessary to change the lining simply because the motor is derated, since the cooling intensity is automatically adjusted according to the power provided by the motor.

Instead of blind bores with inner tubes, the cooling ducts within the upper portion 6 may be through 5 ducts extending from a lower inlet opening up to an upper outlet opening. These channels may be made by drilling at least two intersecting channel portions into the casing wall material, but in order to avoid stress concentrations in the casing, it is preferred that the 10 passages be formed of shaped tubes embedded in the casing. This also gives great freedom to choose an optimal course of the channels.

Claims (10)

A method of cooling a cylinder liner in an internal combustion engine, in particular a large two-stroke main engine in a ship, the liner of its upper portion (6) having 5 more cooling surfaces (8) distributed along the liner circumference, which are cooled by cooling water to dissipate heat. from the liner's running surface (5), characterized in that the cooling intensity varies depending on the heat load on the liner by passing the cooling water 10 to selected cooling surfaces (8, 8 ', 18) whose number and / or distance from the running surface is adjusted to the current heat load. Method according to claim 1, characterized in that the cooling water is directed to selected groups 15 of cooling surfaces, wherein the cooling surfaces (8, 8 ') in groups with several cooling surfaces have essentially the same course with respect to the running surface (5) and that the cooling water flow is regulated such that the individual group is either fully open or completely closed for flow. Method according to claim 2, characterized in that the liner in a portion located below the upper portion (6) has a cooling surface (20), wherein the cooling intensity is adjusted by changing the flow of cooling water quantity. Method according to one of Claims 1 to 3, characterized by compensating for abnormal operating conditions by measuring and recording the actual temperatures at the running surface (5), comparing the recorded temperatures with predetermined limit values and the cooling intensity is adjusted to the nearest new level if a limit value is exceeded. Method according to claim 4, characterized in that an alarm signal is issued if the adjustment of the cooling intensity is due to a local temperature change on the running surface. Method according to one of the preceding claims, characterized in that the cooling intensity 5 is individually regulated for each cylinder liner. A combustion engine, in particular a large two-stroke main engine of a ship, with several cylinder liners, each of which is clamped down against the cylinder portion by means of a cover, which together with the casing and the associated piston delimits a combustion chamber, the casing in its upper portion (6). ) has several water-cooled cooling surfaces (8) distributed according to its circumference to dissipate heat from the casing (5) of the casing, characterized in that the cooling surfaces (8, 8 ', 18, 20) are divided into groups, each having a separate cooling water access passage. (25, 24, 29, 28, 32, 34) and a regulator (37-39, 43) for controlling the water flow in the passage. An internal combustion engine according to claim 7, characterized in that the groups mutually over at least part of the extent of the cooling surfaces in the axial direction of the casing are at different distances from the running surface. An internal combustion engine according to claim 7 or 8, characterized in that a first group comprises a plurality of elongate cooling channels (8) distributed along the circumference, which extend from the outer surface of the casing substantially upwards and inwards towards the running surface (5). second group comprises several elongate cooling channels (8 ') distributed along the circumference of the casing 30 extending from the outer surface of the casing substantially upwardly and inwardly towards the running surface (5), preferably such that the upper portion (16') of the channels (8 ') is at a greater distance from the running surface than the corresponding section (16) 35 of the channels (8) of the first group, and a third group comprises a single circumferential cooling surface (18) at the outer side of the casing radially adjacent to the channels ( 8, 8 ') in the first and second groups, 5 and preferably a fourth group with a single circumferential cooling surface (20) at the outer surface of the casing located axially below the other groups. Internal combustion engine according to one of claims 7-9, characterized in that the first, second 10 and the third group each have a valve (37, 38, 39) which either passes the circulating cooling water quantity all the way through or completely past the respective The valves are controlled so that the current combination of open cooling water groups produces a cooling intensity corresponding to the instantaneous heat load on the liner. 4