EP2503116A1 - Cylinder assembly and piston for a longitudinally flushed stroke piston combustion engine - Google Patents

Abstract

The cylinder arrangement comprises a piston (3) which is provided as two piece piston. A mantle piston (32) is provided with a piston ring (33), where a main piston (31) is positioned in the mantle piston. A retaining device is provided at a cylinder for the mantle piston. The rinsing air (41) is introduced from an inlet area (22) to a combustion chamber (200) by the rinsing air opening (320) of the mantle piston.

Description

The invention relates to a cylinder assembly and a piston for a longitudinally flushed reciprocating internal combustion engine, in particular for a slow-running longitudinally flushed two-stroke large diesel engine according to the preamble of the independent claims.

Large diesel engines are often used as drive units for ships or in stationary operation, eg for driving large generators for generating electrical energy. The engines usually run for long periods in continuous operation, which places high demands on the reliability and availability. Therefore, for the operator in particular long maintenance intervals, low wear and an economical handling of fuels and supplies are central criteria for the operation of the machines. Among other things, the piston running behavior of such large-bore slow-running diesel engines is a determining factor for the length of the maintenance intervals, the availability and the lubricant consumption also directly for the operating costs and thus for the economy. With that comes the complex problem of piston running behavior in large diesel engines, an ever greater importance.

In large diesel engines, but not only these, the piston lubrication is performed by lubricating means in the reciprocating piston or in the cylinder wall, is applied by the lubricating oil on the tread of the cylinder wall, the friction between the piston and the tread and thus the wear of the tread and to minimize the piston rings. So today with modern engines, such as the Wärtsilä two-stroke engines, the wear of the tread at less than 0.05 mm with a service life of 1000 hours. The lubricant delivery rate is in such engines significantly below 1.3 g / kWh and should not least be further reduced for cost reasons, if possible, while the wear is to be minimized.

In this case, very different solutions are known as lubrication systems for lubricating the running surfaces of the cylinder, both as far as the actual execution of the lubrication devices themselves, as well as the procedures for lubrication. The corresponding solutions are well known to the skilled person in their different variants.

However, all measures to improve the lubrication and the piston running leave a problem untouched, the design and thus inevitably occurs in the previously known longitudinally flushed internal combustion engines. As is well known to those skilled in the known longitudinally-flushed two-stroke engines, the fresh air, often referred to as scavenging air introduced at the bottom of the cylinder via scavenging air usually in the form of scavenging slots in the combustion chamber of the cylinder, while the piston is in the vicinity of his is bottom dead center and clears the path for the fresh air into the combustion chamber of the cylinder.

The scavenging ports, through which the fresh air is blown, for example, from a turbocharger into the cylinder under a predetermined pressure, per se do not allow uniform formation of the lubricating oil film on the inner surface of the cylinder in the region of the scavenging slots, since the scavenging ports have openings in the cylinder wall of the cylinder and therefore interrupt the lubricating oil film. The negative influence of the scavenging slots on the formation of the lubricating oil film on the running surface of the cylinder is even below and far above, so even outside the cylinder portion in which the scavenging slots are formed, clearly pronounced. That is, due to the purging slits disturbance of the lubricating oil film on the cylinder surface continues in areas far away from the scavenging and thus far away from the scavenging the piston running behavior and the lubrication between piston or piston rings and cylinder wall significantly negative.

Another negative side effect of the scavenging slots results from their interaction with the piston rings as they pass through the scavenging slots as they move near bottom dead center. Since the piston rings must have a certain mechanical radial prestress so that they can cooperate more or less sealingly with the cylinder wall, these are not formed as completely closed rings, but the piston rings are rather formed as open rings with a gap, so that a radially to externally directed clamping force is created, which presses the piston ring sealingly against the cylinder wall. Under unfavorable conditions, the margins at the gap of the piston ring can be partially pressed into the flushing slots due to the radially outward acting tension of the piston ring, whereby they can get caught on the boundaries of the scavenging slots, resulting in dangerous scratches or grooves on the cylinder or on the cylinder wall near the scavenging slots. In the worst case, this can become a butt and devastation of the cylinder and / or the piston, which can lead to dangerous situations especially in a ship on the high seas.

In addition, a considerable amount of lubricating oil is lost through the scavenging slots when passing the piston ring package. Namely, a certain amount of lubricating oil is always stored in the piston ring package, which accumulates in the piston ring packet during the movement of the piston in the cylinder and which is also under an increased gas pressure, which is essentially built up during the combustion process in the piston ring package and stored therein. If the piston ring package then passes through the scavenging slots, the overpressure stored in the piston ring pack discharges abruptly via the scavenging slots into the receiver chamber or into the piston subspace and at the same time conveys most of the lubricating oil also stored in the piston ring package through the scavenging slots into the receiver chamber. On the one hand, this leads to the loss of the relatively expensive lubricating oil and, on the other hand, leads to unnecessary contamination of the receiver space. In addition, the lubricating oil is no longer available for lubrication during further movement of the piston.

Another disadvantage is the fixed geometry of the scavenging slots. This is particularly disadvantageous in terms of a possible application as a "dual fuel" engine, so as an engine that can be operated with different fuels, for example, alternatively with heavy oil or gas or other fuel. In particular, the non-variable geometry or size of the scavenging slots is such an application in the way.

The object of the invention is therefore to provide a new cylinder assembly and a piston for a cylinder assembly of a longitudinally-flushed reciprocating internal combustion engine, in particular for a slow-running two-stroke large diesel engine, which from the prior Technique known problems, which are particularly determined by the scavenging slots in the lower part of the known cylinder arrangement substantially avoids.

The objects of the invention solving these objects are characterized by the features of independent claims 1 and 9.

The dependent claims relate to particularly advantageous embodiments of the invention.

The invention thus relates to a cylinder assembly for a longitudinally purged reciprocating internal combustion engine, in particular for a slow-running longitudinally purged two-stroke large diesel engine, comprising a cylinder with a combustion chamber and an inlet region, in which cylinder a piston along a cylinder axis between a top dead center and a bottom dead center and is installed movable, wherein on the cylinder a scavenging air inlet for introducing scavenging air is provided in the combustion chamber. According to the invention, the piston is a two-part piston, comprising a shell piston with a piston ring and a main piston positioned in the shell piston. In this case, a retaining device for the mantle piston is provided on the cylinder such that the mantle piston can be lifted in the region of bottom dead center by the retaining device from the main piston with respect to the cylinder axis, so that the purging air can be introduced from the inlet region through a scavenging air opening of the mantle piston into the combustion chamber ,

Characterized in that according to the present invention, the piston is a two-part piston with an outer shell piston and a main piston positioned therein and at a lower end of the cylinder a retaining means for the shell piston is provided such that the shell piston in the region of bottom dead center by the Retaining device from the main piston in relation to the cylinder axis can be lifted, so that the purge air from the inlet region through a scavenging air opening of the jacket piston is introduced into the combustion chamber, the shell piston or the piston skirt arranged on the piston ring and thus the piston as a whole, in its movement in the Near bottom dead center with the scavenging air, in particular so with the scavenging no longer in direct contact, so that even the scavenging slots can be completely dispensed with.

That is, in the inventive solution, the function of the release of the scavenging slots is replaced by the two-piece piston in its movement in the region of bottom dead center. This is achieved in that the shell piston in the cylinder in its movement after completion of a combustion process in the direction of bottom dead center, on which arranged on the cylinder liner in the lower region of the cylinder or integrated therein retainer, preferably damped stored. Since the main piston is operatively connected via the piston rod to the crankshaft, the main piston moves further towards its bottom dead center, while the mantle piston is held by the retainer and remains in this position until the main piston returns from its bottom dead center position towards returns top dead center and then takes the jacket piston again.

In this way, the piston rings of the piston ring assembly arranged on the jacket piston always remain in the closed part of the cylinder liner of the cylinder, so that a blow-off of the lubricating oil contained in the piston ring package, e.g. through the scavenging slots or towards the bottom of the piston can no longer occur.

The fact that in the inventive cylinder arrangement of the piston skirt and thus the piston ring package not directly with a Air inlet opening cooperates in the lower region of the cylinder, through which air inlet opening fresh air is blown, for example, from a turbocharger in the cylinder under a predetermined pressure, there are various advantages.

During the rinsing-closing process known from the prior art, that is to say when the piston upper part closes the rinsing slots, the piston upper part is exposed to an oil mist. This oil mist results from cylinder lubricating oil which is previously blown, for example, during the downward movement of the piston in the direction of bottom dead center by the pressure discharge from the ring package of the piston rings in the piston bottom. The aforementioned oil mist settles in the form of deposits, burns and coked and settles as Ölkoks on the piston upper part, which can lead to the well-known harmful "liner polishing" and in the worst case even to feed. In a two-part piston according to the present invention, the piston upper part can not be acted upon by the above-described oil mist in the purge air, since the peripheral surface of the jacket piston no longer comes into direct contact with the purge air. Thus, when using the two-part piston according to the invention, the harmful oil coke deposits on the upper piston part are reliably prevented, at least massively reduced.

A further advantage arises from the fact that, in the cylinder arrangement according to the invention, the jacket piston and thus the piston ring assembly do not interact directly with an air inlet opening in the lower region of the cylinder, through which air inlet opening fresh air is blown, for example, from a turbocharger into the cylinder under a predetermined pressure a completely uniform formation of the lubricating oil film on the inner surface of the cylinder. The lubricating oil film can form over the entire running surface of the cylinder completely evenly to the lower end of the cylinder where the retaining element is located.

The lubricating oil film on the cylinder wall is thus no longer interrupted by the air inlet openings, since the lubricating oil film is no longer formed in the region of the air inlet openings, but only up to the retainer. A negative influence of the air inlet openings, e.g. a negative influence by the scavenging slots on the formation of the lubricating oil film is thus excluded.

Thus, a harmful interaction of the air inlet openings is excluded with the piston rings, as they no longer interact directly with the air inlet openings as such. Thus, the edges on the gap of the piston ring due to the radially outwardly acting tension of the piston ring can not be pressed into the air inlet openings, and consequently can no longer get caught at the boundaries of the scavenging slots, so that by the inventive cylinder arrangement, the dangerous scratches or Grooves on the cylinder or on the cylinder wall can no longer occur.

Also, no lubricating oil is lost over the scavenging slots, since the piston ring package with the air inlet openings no longer comes into direct contact, so that the lubricating oil remains in the piston ring package and is available for further lubrication. As a result, a considerable amount of lubricating oil can ultimately be saved, the lubrication between the piston and cylinder is massively improved, in particular in the lower region of the cylinder in the vicinity of the bottom dead center and the receiver chamber is no longer contaminated by lubricating oil from the piston ring package.

In a preferred exemplary embodiment, a damping element is provided on the retaining device and / or on the jacket piston, so that the jacket piston can be absorbed in a damped manner by the retaining device. The piston moves in the operating state at a considerable speed in the direction of its bottom dead center, so that in the In most cases, a damping element must be provided so that the jacket piston is not braked too abruptly by the retainer, which could lead to severe damage to the piston and cylinder.

The arrangement according to the invention also for the first time offers the possibility of providing an adjusting device, so that an opening cross-section of the scavenging air opening can be set. It is namely a further advantage of the two-part piston according to the invention that the opening cross section of the scavenging air opening can even be variably adjusted. For a given piston geometry, the opening cross section results essentially from the distance between the jacket piston and the main piston in the open state.

This distance can be influenced, for example, by varying the distance of the retaining device from the bottom dead center of the piston or by, for example, changing the rest position of the jacket piston by providing an actuating device, e.g. is provided in the form of a spacer. The greater the distance between the retaining device and the jacket piston is selected by the actuator, the greater is the opening cross section for the purge air between the main piston and shell piston at a given crank angle. The same applies, of course, if the distance of the retaining device to bottom dead center is greater.

In this case, the adjusting device may be, for example, a hydraulic, pneumatic or electric adjusting device, wherein the adjusting device may be provided, inter alia, on the retaining device and / or on the jacket piston. In particular, for example, the damping element can be additionally designed as an adjusting device accordingly. That is, the actuator may, for example, the axial position of the Set retaining device in the cylinder. For this purpose, the restraining device can be provided, for example, as a ring formed in the interior of the cylinder, which ring can be displaced by the adjusting device along the cylinder axis. Or in another example, the actuator may be a spacer provided between the skirt and retainer, the height of which can be variably adjusted.

Due to the possibility of variably adjustable opening cross-section for the scavenging air, so the ability to make the flushing flexible, the engine can be easily and very flexible optimized by simply changing the opening cross section between the main piston and shell piston, for example, for certain load ranges, such as the partial load range.

In addition, an engine with a cylinder arrangement according to the invention can for the first time also be used as a "dual fuel" engine, which can alternatively be operated with various fuels such as gas, heavy oil, diesel oil or other fuels, because now the amount of scavenging air entering the combustion chamber during the flushing process is introduced, can be variably adjusted for the first time in very wide limits.

Particularly advantageous is provided on the cylinder an evacuation hole for the exchange of lubricating oil. By evacuation bores, for example, lubricating oil can be spent from the tread of the cylinder from the inside of the cylinder to the outside and there either disposed of or reused. It is also possible to introduce lubricating oil into the cylinder via the previously mentioned evacuation bores.

Particularly preferably, a centering means for centering the main piston with respect to the jacket piston is provided on the main piston and / or on the shell piston, so that on the one hand the main piston is always accurately inserted into the shell piston. And on the other hand in the assembled state of the piston of the main piston and the shell piston always positively positively act together so that the combustion chamber is sealed during the compression phase, the combustion phase and the expansion phase until the beginning of the rinsing phase safely against the piston subspace.

The centering means may be in a manner known to those skilled in the art, for example, a guide bushing in the interior of the shell piston and / or on an outer surface of the main piston, or even more preferably a conical shape of the main piston and / or the shell piston. If the piston upward movement in the direction of top dead center is then initiated starting from bottom dead center, then the main piston automatically centers in the shell piston and closes the purge air opening of the shell piston so that the piston can again assume its normal function as a working piston.

The invention further relates to a piston for a longitudinally purged reciprocating internal combustion engine, in particular for a slow-running longitudinally purged two-stroke large diesel engine with a cylinder arrangement according to the invention. The piston of the invention is in a cylinder of the cylinder assembly along a cylinder axis between a top dead center and a bottom dead center back and forth installable installed. According to the invention, the piston is a two-part piston, comprising a jacket piston with a piston ring assembly and a main piston positionable in the shell piston, so that the shell piston in the installed state in the region of bottom dead center by a retaining device of the cylinder with respect to the cylinder axis from the main piston can be lifted.

Particularly preferably, a damping element is provided on the jacket piston.

By a specifically provided adjusting device can be adjustable in the installed state, an opening cross-section of a scavenging air opening of the jacket piston, wherein the adjusting device is advantageously a hydraulic, pneumatic or electrical adjusting device. In particular, the adjusting device may be provided on the jacket piston and, in particular, the damping element itself is designed as an adjusting device.

Particularly preferably, a centering means for centering the main piston in the shell piston is provided on the main piston and / or on the shell piston, wherein the centering means may be, for example, a guide bush or a conical shape of the main piston or the shell piston.

Fig. 1

eine bekannte Zylinderanordnung mit Spülschlitzen im Längsschnitt;

Fig. 2a

schematische Darstellung einer ersten erfindungsgemässen Zylinderanordnung mit Kolben im geschlossenen Zustand;

Fig. 2b

die Zylinderanordnung der Fig. 2a mit Kolben im geöffneten Zustand;

Fig. 3

ein zweites Ausführungsbeispiel einer erfindungsgemässen Zylinderanordnung mit Evakuationsbohrungen und Stelleinrichtung;

Fig. 4a

ein spezielles Ausführungsbeispiel eines erfindungsgemässen Kolbens;

Fig. 4b

das Beispiel der Fig. 4a in perspektivischer Ansicht;

Fig. 4c

Darstellung des Inneren des Mantelkolbens gem. Fig. 4a bzw. Fig. 4b;

The invention will be explained in more detail below with reference to the schematic drawing. Show it:

Fig. 1

a known cylinder arrangement with scavenging slots in longitudinal section;

Fig. 2a

schematic representation of a first inventive cylinder assembly with piston in the closed state;

Fig. 2b

the cylinder arrangement of Fig. 2a with piston in the open state;

Fig. 3

A second embodiment of an inventive cylinder assembly with evacuation holes and actuator;

Fig. 4a

a special embodiment of a piston according to the invention;

Fig. 4b

the example of Fig. 4a in perspective view;

Fig. 4c

Representation of the interior of the shell piston gem. Fig. 4a respectively. Fig. 4b ;

Fig. 1 shows in a schematic representation partially in section a cylinder assembly 1 'with cylinder liner 2', piston 3 'and fresh air supply system 400'.

The cylinder assembly 1 'of Fig. 1 is a typical arrangement well known for prior art longitudinally scavenged two-stroke large diesel engines. For better distinction of the known cylinder arrangement, the corresponding reference numerals are provided with an apostrophe, while the reference numerals to features according to the invention cylinder arrangements wear no apostrophe.

The arrangement comprises a cylinder 2 ', which is also referred to as a cylinder liner 2', in which a piston 3 'along a cylinder wall of the cylinder 2' is arranged back and forth movable. The piston 3 'comprises a piston ring packing 33', which is shown here schematically with only two piston rings.

The combustion chamber 200 ', which is located in the combustion chamber region 21' of the cylinder 2 ', is delimited at the top by a cylinder cover with an injection nozzle and exhaust valve.

The piston 3 ', which reciprocates in the operating state of the large diesel engine between the top dead center OT' and the bottom dead center UT ', via the piston rod 8' with a in Fig. 1 not shown crosshead connected, from which the reciprocating movement of the piston 3 'is transmitted to the crankshaft, also not shown, of the machine. The piston rod 8 'is guided through the receiver space 401', which adjoins the inlet area 22 'of the cylinder liner 2' below, and the stuffing box 402 ', which seals the receiver space 401' against the crankshaft space below, so that no fresh air 41 ', symbolized by the arrow 41', which supplies a likewise not shown turbocharger under a high pressure, for example, under a pressure of four bar in the receiver chamber 401 ', from the receiver room 401' in the underlying crankshaft space 9 'can pass.

Again Fig. 1 can be seen and is generally known, is in the receiver chamber 401 'always generated by the turbocharger gas pressure of the fresh air 41', which thus always by design rests on the piston bottom of the piston 3 '.

After a combustion process initiated in the combustion chamber 200 'when the piston 3' is very close to the top dead center OT ', the piston 3' moves toward the bottom dead center UT 'due to the combustion pressure built up in the combustion chamber 200'. wherein, when the piston surface is below the scavenging air opening 4 'with scavenging slots 221', scavenging air 41 'can reach the combustion space 200' via the scavenging slots 4 'from the receiver space 401', so that they can be burned in the combustion space 200 'for the next combustion process. is available.

On its way from top dead center OT 'to bottom dead center UT' and back, the piston must inevitably pass through the scavenging ports 4 'in the inlet region 22', which has the negative consequences already described in detail, which need not be repeated here in detail.

In Fig. 2a is a first inventive cylinder arrangement in the case of a longitudinally-flushed two-stroke large diesel engine simplified schematically shown. The cylinder assembly 1 of Fig. 2a shows a piston in the closed state. For reasons of clarity, all, for the understanding of the invention not essential components of the large diesel engine in the Fig. 2a to Fig. 3 not explicitly shown.

The cylinder assembly 1 of Fig. 2a comprises a cylinder 2 with a combustion chamber 200 and an inlet region 22, through which purging air can be introduced into the cylinder. The inlet region 22 or the other components of the large diesel engine can be known in principle as known from the prior art and in Fig. 1 already described, be designed.

The combustion chamber 200 is limited by a cylinder cover, not shown, with injection nozzle and exhaust valve. The main piston 31 of the piston 3, which reciprocates in the operating state of the large diesel engine along a cylinder axis Z between the top dead center and the bottom dead center UT, is connected via the piston rod 8 with a crosshead, also not shown, from which the back and forth movement of the piston 3 is transmitted to the crankshaft, not shown, of the two-stroke large diesel engine. To this end, the piston rod 8 is guided by a receiver space, not shown, which extends in the inlet region 22 of the cylinder 2 in accordance with the illustration, and is connected to the crankshaft in an effective manner. In the receiver room, scavenging air 41 is provided via a scavenging air inlet 4, which a turbocharger, also not shown, operates in a manner known per se under a high pressure, e.g. at a pressure of four bar to the receiver room feeds.

According to the present invention, the piston 3 is a two-part piston 3 comprising a jacket piston 32 with a piston ring package 33 and a piston positioned in the piston 32 main piston 31. The cylinder 2 is a Retaining device 5 provided for the shell piston 32 such that the shell piston 32 in the area of bottom dead center UT by the retainer 5 from the main piston 31 with respect to the cylinder axis Z can be lifted, so that, as in Fig. 2b illustrated, the purge air 41 from the inlet portion 22 through a purge air opening 320 of the shell piston 32 is introduced into the combustion chamber 200.

The introduction of the scavenging air 41 via the scavenging air opening 320 of the jacket piston 32 is in Fig. 2b illustrated, showing a cylinder assembly 1 according to the invention with piston 3 in the open state.

In Fig. 2b The main piston 31 moves just near the bottom dead center UT and is therefore separated from the shell piston 32, which is in the retainer 5, which is designed as a retaining ring in the interior of the cylinder 2 deducted. Characterized in that the jacket piston 32 deposited in the retainer 5 and the main piston 31 is separated from the shell piston 32, the purge air opening 320 is open in the shell piston 32, so that an opening cross-section 111 is formed, through which the purge air can flow into the combustion chamber 200, as is symbolized by the arrows 41.

Based on Fig. 3 Finally, a second, very important for practice embodiment of an inventive cylinder assembly 1 with damping element 10 is shown schematically, wherein the damping element 10 is formed as an adjusting device 11 in the form of a spacer element.

The adjusting device 11 and the damping element 10 is here a hydraulic element, which can be acted upon by hydraulic fluid, not shown, with a predetermined amount of hydraulic fluid under a predetermined pressure, whereby on the one hand, the damping force, me the jacket piston 32 when placed on the Retaining device 5 is damped, is adjustable. On the other hand, at the same time or alternatively, the distance between retaining device 5 and shell piston 32 is adjustable, so that thereby the opening cross-section 111 and thus the supply of scavenging air 41 in the combustion chamber 200 to the respective operating conditions is flexibly adaptable.

Due to the flexible adjustability of the scavenging air supply, the two-stroke large diesel engine of the invention can be used for the first time as a "dual fuel" engine, which can be operated alternatively with various fuels such as gas, heavy oil, diesel oil or other fuels, because now the amount of scavenging air 41, which is introduced into the combustion chamber 200 during the flushing process, for the first time can be set variably within very wide limits.

Moreover, in the embodiment according to Fig. 3 provided on the cylinder 2 an evacuation hole 12 for the exchange of lubricating oil. As a result of the evacuation bore 12, for example, lubricating oil can be brought out of the running surface of the cylinder 2 from the interior of the cylinder 2 to the outside and either disposed of there or fed for reuse. It is also possible to introduce lubricating oil into the cylinder 2 via the aforementioned evacuation bore 12 as an alternative.

Furthermore, according to Fig. 2a to Fig. 4c provided on the main piston 31 and the shell piston 32, a centering means 13 for centering the main piston 31 with respect to the shell piston 32, so that on the one hand, the main piston 31 is always accurately inserted into the shell piston 32. And on the other hand in the assembled state of the piston 3 of the main piston 31 and the shell piston 32 always positively positively act together so that the combustion chamber 200 during the compression phase, the combustion phase and the expansion phase until at the beginning of the rinsing phase is securely sealed against the piston subspace largely pressure.

The centering means 13 is provided here by way of example on an outer surface of the main piston 31 as a conical design of the main piston 31 and in the form of a corresponding inversely conical surface on the shell piston 32. If the piston upward movement in the direction of top dead center is then initiated in the operating state from bottom dead center UT, the main piston 31 automatically centers in the shell piston 32 and thus closes the scavenging air opening 320 of the shell piston 32 so that the piston 3 again assumes its normal function as a working piston can.

Based on Fig. 4a is a further specific embodiment of a piston according to the invention shown schematically, with a better understanding Fig. 4b the example of Fig. 4a again in a perspective view and in Fig. 4c a more detailed representation of the interior of the shell piston 32 gem. Fig. 4a respectively. Fig. 4b you can see.

Also in the embodiment gem. Fig. 4a to 4c is provided on the main piston 31 and the shell piston 32, a centering means 13 for centering the main piston 31 with respect to the shell piston 32, so that here again on the one hand, the main piston 31 is always accurately inserted into the shell piston 32. And on the other hand in the assembled state of the piston 3 of the main piston 31 and the shell piston 32 always positively positively cooperate such that the combustion chamber during the compression phase, the combustion phase and the expansion phase until the beginning of the rinsing phase is securely sealed against the piston subspace largely pressure.

The centering means 13 is provided here on an outer surface of the main piston 31 as a conical design of the main piston 31 and in the form of a corresponding inversely conical surface on the shell piston 32.

In addition, the main piston 31 has a first anti-rotation 1301, here in the example via a plurality of first anti-rotation 1301 and a corresponding number of second anti-rotation 1302 inside the shell piston 32. The first anti-rotation 1301 and the second anti-rotation 1302 act in the assembled state of Piston 3 together so that a rotation of the shell piston 32 against the main piston 31 at least during the compression phase, the combustion phase and the expansion phase until the beginning of the rinsing phase is reliably prevented.

In addition, at the first anti-rotation 1301 and a respective damping element 10 is provided, which is designed as an adjusting device 11, wherein the adjusting device 11 may also be a suitable hydraulic, pneumatic or electrical adjusting device 11 or damping element 10, in particular also as simple Spring element, possibly can be configured with adjustable spring travel.

It is understood that the embodiments described in the context of this application are to be understood as exemplary only and the invention is not limited to these examples. In particular, the described embodiments can also be advantageously combined.

Claims (15)

Cylinder arrangement for a longitudinally purged reciprocating internal combustion engine, in particular for a slow-running longitudinally purged two-stroke large diesel engine, comprising a cylinder (2) with a combustion chamber (200) and an inlet region (22), in which cylinder (2) a piston (3) along a cylinder axis ( Z) between a top dead center and a bottom dead center (UT) is mounted back and forth, and on the cylinder (2) a scavenging air inlet (4) for introducing scavenging air (41) into the combustion chamber (200) is provided, characterized that the piston (3) is a two-part piston (3), comprising a shell piston (32) with a piston ring (33) and one in the jacketed flask (32) positioned main piston (31) and the cylinder (2) a retainer (5) for the jacket piston (32) is provided such that the jacket piston (32) in the region of bottom dead center (UT) by the retainer (5) from the main piston (31) in relation to the cylinder axis (Z) abhebb ar is, so that the purging air (41) from the inlet region (22) through a scavenging air opening (320) of the jacket piston (32) into the combustion chamber (200) can be introduced. Cylinder arrangement according to claim 1, wherein a damping element (10) is provided on the retaining device (5) and / or on the jacket piston (32). Cylinder arrangement according to claim 1 or 2, wherein an adjusting device (11) is provided, so that an opening cross section (111) of the scavenging air opening (320) is adjustable. Cylinder arrangement according to claim 3, wherein the adjusting device (11) is a hydraulic, pneumatic or electrical adjusting device (11). Cylinder arrangement according to claim 3 or 4, wherein the adjusting device (11) on the retaining means (5) and / or on the jacket piston (32) is provided and in particular the damping element (10) is designed as adjusting device (11). Cylinder arrangement according to one of the preceding claims, wherein an evacuation bore (12) for exchanging lubricating oil is provided on the cylinder (2). Cylinder arrangement according to one of the preceding claims, wherein a centering means (13) for centering the main piston (31) with respect to the shell piston (32) is provided on the main piston (31) and / or on the shell piston (32). Cylinder arrangement according to claim 7, wherein the centering means (13) is a guide bush or a conical shape of the main piston (31) or the shell piston (32). Piston for a longitudinally flushed reciprocating internal combustion engine, in particular for a slow-running longitudinally-flushed two-stroke large diesel engine with a cylinder assembly (1) according to one of the preceding claims, which piston in a cylinder (2) of the cylinder assembly (1) along a cylinder axis (Z) between a top dead center and a bottom dead center (UT) is reciprocally installable, characterized in that the piston (3) is a two-part piston (3) comprising a shell piston (32) having a piston ring (33) and a in the shell piston (32) positionable main piston (31), so that the jacket piston (32) in the installed state in the area of bottom dead center (UT) by a retaining device (5) of the cylinder (2) with respect to the cylinder axis (Z) from the main piston (31) can be lifted. Piston according to claim 9, wherein a damping element (10) is provided on the jacket piston (32). Piston according to claim 9 or 10, wherein an adjusting device (11) is provided, so that in the installed state, an opening cross-section (111) of a scavenging air opening (320) of the jacket piston (32) is adjustable. Piston according to claim 11, wherein the adjusting device (11) is a hydraulic, pneumatic or electric adjusting device (11). Piston according to claim 11 or 12, wherein the adjusting device (11) on the jacket piston (32) is provided and in particular the damping element (10) is designed as adjusting device (11). Piston according to one of the preceding claims 9 to 13, wherein a centering means (13) for centering the main piston (31) in the shell piston (32) is provided on the main piston (31) and / or on the shell piston (32). Piston according to claim 14, wherein the centering means (13) is a guide bush or a conical shape of the main piston (31) or the shell piston (32).

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