DK177989B1

DK177989B1 - A large two-stroke internal combustion engine and an exhaust gas receiver for a large two-stroke internal combustion engine

Info

Publication number: DK177989B1
Application number: DK201400112A
Authority: DK
Inventors: Jørgen Løvschall Rasmussen; Henrik Baldur Hansen
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2014-02-27
Filing date: 2014-02-27
Publication date: 2015-02-16
Also published as: JP5837241B2; JP2015161303A; KR101538690B1; CN104763507B; CN104763507A

Description

A LARGE TWO-STROKE INTERNAL COMBUSTION ENGINE AND AN EXHAUST GAS RECEIVER FOR A LARGE TWO-STROKE INTERNAL COMBUSTION ENGINE

FIELD OF THE INVENTION

The present invention relates to a large two-stroke internal combustion engine, and to an exhaust gas receiver for a large two-stroke internal combustion engine .

BACKGROUND OF THE INVENTION

The exhaust gas receiver of a large two-stroke combustion (diesel) engine is a highly loaded component that receives the hot (approximately 450°C inside the exhaust gas receiver) exhaust gases from the individual cylinders at a pressure of up to 4 bar.

Due to the large size of the exhaust gas receiver (can be significantly over 10 m long and have a diameter of up to approx. 2,2 m) and the high operating temperature, thermal expansion of the exhaust gas receiver is very significant, and the larger engines have an exhaust gas receiver that can be divided into two or more housing parts separated by bellows to absorb the dimensional changes caused by the thermal expansion. The complete exhaust gas receiver and any parts belonging thereto are covered with a layer of insulating material, so that the temperature of the outside surface of the exhaust gas receiver is substantially below the temperature of the exhaust gases inside the exhaust gas receiver. Safety regulations require that the temperature of the outside surface of the exhaust gas receiver is below 220°C, so that there are no exposed engine parts having a temperature sufficiently high to ignite engine fuel or other oils that inadvertently come into contact therewith. In practice the outer surface of the exhaust gas receiver is so well insulated that its surface temperature remains below 150°C.

The exhaust gas receivers are in the middle of their longitudinal extension, or at one end, supported by a relatively rigid main support. Several flexible supports are distributed along the length of the exhaust gas receiver, typically on either side of the rigid support, and connect the exhaust gas receiver with the engine housing or engine main structure. The flexible supports are conventionally formed by a single plate that allows a substantial movement in the longitudinal direction of the exhaust gas receiver which is reguired to compensate for the thermal expansion or contraction of the exhaust gas receiver as it heats up or cools down.

On top of the thermal and pressure load, the vibrating movement of the engine shakes the construction and thereby further increases the mechanical load on the exhaust gas receiver.

The main support includes two closely spaced upright parallel plates, one connected rigidly to the main structure of the engine and the other upright plate rigidly connected to a downwardly projecting main bracket that is secured to the lowermost portion of the exhaust gas receiver. The two closely spaced upright parallel plates are connected near their upper ends and near their lower ends by respective packs of flexible plates to absorb the longitudinal forces created from the gas pulsations inside the exhaust gas receiver.

The main support fixes the exhaust gas receiver in the longitudinal direction. The downwardly projecting main bracket is welded to the outer side of relatively thin metal shell in the lowermost portion of the exhaust gas receiver. In order to distribute the forces that have to be transmitted between the main bracket and the exhaust gas receiver the main bracket has to be of a certain size. However, the main bracket projects downwardly from the metal shell of the exhaust gas receiver and the insulation layer around the metal shell has to extend around the downwardly projecting main bracket, causing insulation of the exhaust gas receiver in the area of the main bracket to be more challenging.

Further, the exhaust gas temperature inside the receiver is above 400 degrees Celsius. This results in the bracket outside the receiver sharply cooling down. This phenomenon introduces stress gradients in the main bracket, in particular in the longitudinally extending main plate and the associated weldings between the main plate and the metal shell of the exhaust gas receiver.

DISCLOSURE OF THE INVENTION

On this background, it is an object of the present invention to provide an exhaust gas receiver and engine that at least partially solve the above problem.

This object is achieved by providing an elongated, essentially cylindrical exhaust gas receiver having a metal shell with a hollow interior, the exhaust gas receiver comprising a plurality of exhaust gas inlets and one or more exhaust gas outlets, a plurality of support points for connecting the exhaust gas receiver to a plurality of secondary supports that are flexible in the longitudinal direction of the exhaust gas receiver and stiff in the transverse direction of the exhaust gas receiver, at least one main bracket including a longitudinally and radially extending main metal plate for connecting the exhaust gas receiver to a main support that is stiff in the longitudinal direction of the exhaust gas receiver, whereby at least a portion of the main metal plate projects into the hollow interior of the exhaust gas receiver.

By providing a main bracket with a main plate that extends through the shell into the hollow interior of the exhaust gas receiver the size and the surface area of the portion of the main bracket that projects outwardly from the shell is reduced.

The portion of the main bracket that projects outwardly from the shell acts like a heating fin, which is disadvantageous since the heat of the exhaust gases should not be lost and should be used by e.g. a turbocharger and the portion of the main bracket that projects outwardly from the shell and needs to be provided with a insulation cover and it is an advantage when the insulation cover can become smaller or can be avoided.

With the exhaust receiver according to the invention heat loss via the main plate and eventually via the transverse plates is reduced, and insulation cover can be avoided or at least simplified and reduced in size. Further, insulation of the exhaust gas receiver in the area of the main support is simplified.

Further, the portion of the main bracket that projects outwardly from the shell is sharply cooling down relative to the inner temperature of the exhaust gas receiver of approx. 400 deg. C. This phenomenon cause stress gradients in the main plate and the associated weldings that connect the main plate to the shell and to transverse plates of the bracket.

With the exhaust gas receiver according to the invention the portion of the main bracket that projects outwardly from the shell can be reduced and thereby stress gradients can be reduced correspondingly. Consequently the temperature of the bracket during engine operation becomes more uniform.

In an example embodiment the main metal plate projects both into the hollow interior and projects from the exterior of the shell.

In an example embodiment the bracket includes one or more traverse metal plates that at least partially project into the hollow interior and the one or more transverse metal plates being connected to the main metal plate.

In an example embodiment the main metal plate is downwardly projecting relative to the exhaust gas receiver in its intended position of use, and wherein the main metal plate has a downwardly facing edge and the downwardly facing edge is configured as an attachment surface for attachment of the main bracket to the main support.

In an example embodiment the downwardly facing edge is provided with threaded bores that extend upwardly into the main metal plate. Thus, a practical arrangement is provided for connecting the main metal plate to the main support,

In an example embodiment the main metal plate is connected to the metal shell by welds that are applied from the hollow interior and preferably also by welds that are applied from the exterior of the exhaust gas receiver .

By providing a bracket with a main plate that extends through the shell into the hollow interior of the exhaust gas receiver the weldings that connect the main plate to the shell of the exhausts gas receive can be applied to-and from the inside of the shell, and thereby provide a stronger and more robust connection.

The object above is also provided by providing a large two-stroke diesel engine comprising an engine main structure, an exhaust gas receiver as defined hereabove, a main support and a plurality of secondary supports arranged below the exhaust gas receiver to support the exhaust gas receiver on the engine main structure, the secondary supports being distributed along the length of the exhaust gas receiver, and the secondary supports each having an upper end mounted to the exhaust gas receiver and a lower end mounted to the engine main structure.

Further objects, features, advantages and properties of the exhaust gas receiver and engine according to the invention will become apparent from the detailed description .

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiment shown in the drawings, in which:

Fig. 1 is a view of the long side of a large two-stroke internal combustion engine with a conventional exhaust gas receiver,

Fig. 2 is a view of the rear end of the engine shown in Fig. 1,

Fig. 3 is a side view of a conventional exhaust gas receiver for a large two-stroke internal combustion engine,

Fig. 4 is a detailed of the view of the conventional exhaust gas receiver of Fig. 3,

Fig. 5 is a perspective view of a prior art main bracket of the exhaust gas receiver of Fig. 3 including a view of apportion of a main bracket,

Fig. 6 is a cross sectional view of the lower portion of the exhaust gas receiver of Fig. 3 and its main support bracket,

Fig. 7 is a cross sectional view of the lower halve of an exhaust gas receiver according to an example embodiment of the invention,

Fig. 8 is a detailed view of a portion of the bracket shown in Fig. 7, and

Fig. 9 is a perspective cut open view of the central lower portion of the exhaust gas receiver and and the main bracket shown in Fig. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figs. 1 and 2 show an example embodiment of a large two-stroke internal combustion (diesel) engine with a main structure 1 in side view and end view, respectively. The engine is in this embodiment a uniflow low-speed two-stroke crosshead diesel engine with crossheads, which may be a propulsion system in a ship or an engine in a power plant. These engines have typically from 4 up to 14 cylinders in line. The engine is built up from a bedplate 2 with the main bearings for the crankshaft (only the flywheel 3 that is attached to the end of the crankshaft is visible). The bedplate 2 can be made in one part or be divided into sections of suitable size in accordance with production facilities. A welded design A-shaped frame box 4 is mounted on the bedplate 2. On the exhaust side, the frame box 4 is provided with relief valves for each cylinder while, on the camshaft side, the frame box 4 is provided with a large hinged door for each cylinder. The crosshead guide planes (not shown) are integrated in the frame box 4. A cylinder frame 5 is mounted on top of the frame box 4. Staybolts (not shown) connect the bedplate 2, the frame box 4 and the cylinder frame 5 and keep the structure together. The cylinder frame 5 carries the individual cylinders 6. Each of the cylinders of the engine is connected to an inlet 15 of the exhaust gas receiver 16 by an exhaust passage. The cylinder frame 5 forms together with the cylinder liners 6 the scavenge air space. The scavenge air receiver 9, is bolted to the cylinder frame 5. A piston (not shown) is received inside each of the cylinder liners 6. A piston rod (not shown) connects the bottom of the piston to the top of a crosshead (not shown). The cylinder liners 6 are carried by the cylinder frame 5.

The engine is fitted with one or more turbochargers 10 arranged on the side or at the aft end of the engine. The cylinders are of the uniflow type and have scavenge air ports (not shown) located in an airbox, from which the scavenge air receiver 9 is supplied with scavenge air pressurized by the turbocharger 10. The air intake to the turbocharger 10 takes place directly from the engine room through an intake silencer (not shown) of the turbocharger. From the turbocharger 10, the air is led via an air cooler 11, a charging air pipe 12 and the scavenge air receiver 9 to the scavenge ports of the cylinder liners 6. The engine is provided with hydraulically- or electrically-driven auxiliary scavenge air blowers 13. The auxiliary blowers 13 assist the turbocharger compressor at low and medium load conditions .

An exhaust valve (not shown) is mounted centrally in the top of the cylinder in a cylinder cover 14. At the end of the expansion stroke the exhaust valve opens before the engine piston passes down past the scavenge air ports, whereby the combustion gases in the combustion chamber above the piston flow out through an exhaust passage opening into an exhaust gas receiver 16, and the pressure in the combustion chamber is relieved. The exhaust valve closes again during the upward movement of the piston. Manhole covers allow access of service personnel into the exhaust gas receiver 16 during maintenance and overhaul.

As shown in Fig. 1, the exhaust gas receiver 16 is preferably supported by the scavenge air receiver 9 of the engine main structure 1. In alternative embodiments the exhaust gas receiver 16 may be mounted to other main engine structures, such as the frame box 4 or the cylinder frame 5, via a main support 22 and plurality of secondary supports 21 as described below. Now returning to Fig. 1, the exhaust gas receiver 16 is supported on the scavenge air receiver 9 by a main support 22 that is rigid in the longitudinal direction but flexible in the vertical direction. In the embodiment shown, the main support 22 is provided at the middle of the exhaust gas receiver 16, fixing the middle of the exhaust gas receiver 16 relative to the scavenge air receiver 9. The main support 22, preferably is arranged centrally with respect to the exhaust gas receiver 16, however it does not necessarily need to be positioned exactly in the middle, but may be offset slightly. The main support 22 may alternatively be arranged near a longitudinal end of the exhaust gas receiver 16. As shown, the exhaust gas receiver 16 is further mounted on the scavenge air receiver 9 via a plurality of secondary supports 21 that are stiff in the transverse direction and in the vertical direction but flexible in the longitudinal direction of the exhaust gas receiver 16. The secondary supports 21 essentially consists of a vertical metal plate extends transverse to the longitudinal axis of the exhaust gas receiver 16 and this metal is fixed at its lower end to the engine main structure 1 and at its upper end to the exhaust gas 16 receiver by a suitable racket.

The plurality of secondary supports 21 are distributed along the length of the exhaust gas receiver 16 on either side of the main support 22. The secondary supports 21 are each defined by a plate structure that follows any temperature-induced lengthwise contraction or expansion of the exhaust gas receiver 16 in relation to the engine housing/scavenge air receiver 9 (or another engine structure to which it is mounted (not shown) ) as the exhaust gas receiver 16 heats up or cools down. During engine operation, hot gas from the combustion chambers of the cylinders is collected in the exhaust gas receiver 16. Therefore, due to thermal expansion of the materials used in the exhaust gas receiver 16, the length of the exhaust gas receiver 16 will increase during engine operation. Due to the overall length of an exhaust gas receiver 16 in large two stroke diesel engines (5-35 meters) the expansion in the longitudinal direction may be considerable (in the order of several centimeters). To avoid any transverse vibrations of the exhaust gas receiver 16 the secondary supports 21 show little or no resiliency in the transverse direction of the exhaust gas receiver 16.

Conventionally, one upright plate having a thickness in the order of 10-25 mm is used for the secondary supports 21, and each upright plate is conventionally bolted to the scavenge air receiver 9, and bolted to the exhaust gas receiver 16 with the major surface of the plate being oriented in the transverse direction of the exhaust gas receiver 16, i.e. perpendicular to a longitudinal axis of the elongate exhaust gas receiver 16.

The shell of the exhaust gas receiver 16 is covered with a layer of insulation material 17, to avoid heat loss and to ensure that the temperature of the outside surface of the exhaust gas receiver is below 220°C, so that no exposed engine parts have a temperature sufficiently high to ignite engine fuel or other oils that inadvertently come into contact therewith. The insulation layer 17 includes an outer layer of thin metal plates. The outer surface of insulation layer 17 of the exhaust gas receiver 16 is so well insulated that its surface temperature remains below 150°C.

Figs. 3 to 6 show of a prior art elongated exhaust gas receiver 16 similar to the one shown with the engine in Fig. 1 The exhaust gas receiver 16 is provided with a plurality of exhaust gas inlets 15 that serve to connect to the exhaust bends of individual cylinders of the engine 1. In the shown embodiment the exhaust gas receiver 16 is provided with two radial outlets 19 that serve to connect to an inlet of one or more turbochargers 10 .

The shell 33 of the exhaust gas receiver 16 is covered by the insulation layer 17. However, the main bracket that connects the exhaust gas receiver 16 to main support 22 reguires a separate heat insulation cover 18. Due to the irregular shape of the bracket the heat insulation cover 18 is also irregularly shaped, complicated and large in size .

As best seen in Figs. 5 and 6 a prior art bracket for connecting the exhaust gas receiver includes a main metal plate 25 and a number of transverse metal plates, welded to one another and to the bottom of the shell 33 of the exhaust gas receiver 16. The main metal plate 25 projects radially and downwardly from the bottom of the shell 33 exhaust gas receiver 16 and has no parts that protrude into the hollow interior 20 of the exhaust gas receiver 16.

The main support 22 has two closely spaced parallel plates that extend vertically and longitudinally relative to the exhaust gas receiver. The two parallel plates are connected to one another by two packs of flexible metal plates 29. The upper pack of flexible metal plates can be seen in Fig. 6, while the lower pack cannot be seen and is arranged near or at the lower end of the two parallel plates of the main support. The parallel plate construction of the main support 22 allows for flexibility of the main support 22 in the vertical direction, but prevents rotation about the vertical axis and the horizontal axis and ensures the required longitudinal rigidity.

Furthermore, the pack of flexible metal plates reduces local deformation of the exhaust gas receiver. In addition the angular stiffness is increased. Due to the larger rigidity, the margin against vibrations of the main support 22 is increased.

Figs. 7 to 9 show the exhaust gas receiver 16 with its main bracket according to an example embodiment of the invention. The main bracket serves to connect the exhaust gas receiver 16 to the main support 22. The main support can be like described above with two parallel plates that provide flexibility in the vertical direction, or can be of a simpler construction and does not need to be flexible in order to be used with the new exhaust gas receiver 16 and main bracket.

The main bracket includes a longitudinally and radially extending main metal plate 25. At least a portion 26 of the main metal plate 25 projects through the shell 33 into the hollow interior 20 of the exhaust gas receiver 16. Another portion 27 of the main metal plate 25 projects from the shell 33 of the exhaust gas receiver 16 in a bottom area of the latter.

In the example embodiment the main bracket includes one or more traverse metal plates 28 that project into the hollow interior 20 and the transverse metal plates 28 are connected to the portion 26 of the metal plate 25, preferably by welds. In an embodiment the transverse metal plates 28 are connected to the inner side of the metal shell 33, preferably by welds that are applied from the interior of the metal shell 33.

The main metal plate 25 is downwardly projecting relative to the exhaust gas receiver 16 in the intended position of use of the exhaust gas receiver 16, and the main metal plate 25 has a downwardly facing edge that is configured as a horizontally extending attachment surface for attachment of the main plate 25 to said main support 22.

Hereto, the downwardly facing edge is provided with an array of longitudinally spaced threaded bores 30 that extend upwardly into the main metal plate 25. The main metal plate is connected to the main support 22 with threaded bolts (not shown) that are screwed into the treaded bores 30 and clamp a plate of the main support 22 with correspondingly sized and spaced holes to the main metal plate 25.

The main metal plate 25 is connected to the metal shell 33 by welds 35 that are applied from the hollow interior 20 and preferably also by welds 36 that are applied from the exterior of the exhaust gas receiver 16.

The main metal plate 25 has a portion 26 that is projecting into the hollow interior 20, and a portion 27 that is projecting to the exterior of the shell 33. The division between these two portions is a horizontal line that coincides with the intersection of the main metal plate 25 with the shell 33.

The main metal plate 25 may be manufactured from a single piece of metal plate such as e.g. a steel plate or alternatively, be manufactured from a plurality of metal plates, such as e.g. steel plates.

The insulation layer can cover the shell 33, also in the area of the main bracket and a separate heat insulation cover for the main bracket can be avoided when the main bracket is constructed in accordance with the present invention .

Although the present invention has been described in detail for purpose of illustration, it is understood that such detail is solely for that purpose, and variations can be made therein by those skilled in the art without departing from the scope of the invention.

Claims

1. Aflang, i alt væsentligt cylindrisk beholder (16) til udstødsgas med en metalskal (33) med et hult indre (20), hvilken beholder (16) til udstødsgas omfatter: en flerhed af indgange (15) til udstødsgas og én eller flere udgange (19) til udstødsgas, en flerhed af støttepunkter til forbindelse af beholderen til udstødsgas med en flerhed af sekundære støtter (21), der er mere fleksible i den langsgående retning af beholderen (16) til udstødsgas end i den tværgående retning af beholderen (16) til udstødsgas, mindst én hovedkonsol indbefattende en langsgående og radialt udstrækkende hovedmetalplade (25) til tilslutning af beholderen (16) til udstødsgas til en hovedstøtte (22), der er mere stiv i den langsgående retning af beholderen (16) til udstødsgas end i den tværgående retning af beholderen til udstødsgas, hvorved mindst en del (26) af hovedmetalpladen (25) rager ind i det hule indre (20) af beholderen til udstødsgas.

2. Beholder (16) til udstødsgas ifølge krav 1, hvor hovedmetalpladen (25) rager både ind i det hule indre (20) og rager frem fra det ydre af skallen (33).

3. Beholder (16) til udstødsgas ifølge krav 1 eller 2, hvor hovedkonsollen indbefatter én eller flere tværgående metalplader (28), der mindst delvist rager ind i det hule indre (20), og hvor den ene eller flere tværgående metalplader (28) er forbundet med metalpladen (25).

4. Beholder (16) til udstødsgas ifølge et hvilket som helst af kravene 1 til 3, hvor hovedmetalpladen (25) rager nedefter i forhold til beholderen (16) til udstødsgas i den tilsigtede position for anvendelse af beholderen (16) til udstødsgas, og hvor hovedmetalpladen (25) har en nedadvendende kant og den nedadvendende kant er konfigureret som en fastgørelsesoverflade til fastgørelse af hovedpladen (25) til hovedstøtten (22).

5. Beholder (16) til udstødsgas ifølge et hvilket som helst af kravene 1 til 4, hvor den nedadvendende kant er forsynet med gevindskårne boringer (30), der strækker sig opefter og ind i hovedmetalpladen (25).

6. Beholder (16) til udstødsgas ifølge et hvilket som helst af kravene 1 til 5, hvor hovedmetalpladen (25) er forbundet med metalskallen (33) ved hjælp af svejsninger (35), der er udført fra det hule indre (20) og fortrinsvis ligeledes ved hjælp af svejsninger (36), der er udført fra det ydre af beholderen (16) til udstødsgas.

7. Stor totaktsdieselmotor omfattende en hovedstruktur til motoren (1), en beholder (16) til udstødsgas ifølge krav 1, en hovedstøtte (22) og en flerhed af sekundære støtter (21), der er placeret under beholderen (16) til udstødsgas til at støtte beholderen (16) til udstødsgas på motorens hovedstruktur (1).