DK177325B1

DK177325B1 - A large two-stroke diesel engine and a supporting plate structure for connection between an engine main structure and an exhaust gas receiver

Info

Publication number: DK177325B1
Application number: DKPA201100051A
Authority: DK
Inventors: Joergen Marken
Original assignee: Man Diesel & Turbo Deutschland
Priority date: 2011-01-25
Filing date: 2011-01-25
Publication date: 2013-01-07
Also published as: JP4995990B1; KR101730122B1; JP2012154334A; CN102720576B; DK201100051A; CN102720576A; KR20120086246A

Abstract

A supporting plate structure (100) for connection between an engine main structure (1) and an exhaust gas receiver (16), said plate structure (100) comprising: two opposite steel plates (110, 115), each having a first and a second end (117, 118) - at least one spacer (130) maintaining said two plates (110, 115) in a spaced apart relationship, said spacer (130) being arranged between said plates (110, 115) at a location (116) between said first (117) and second 118) end, and - a connector (102, 105) at said first end (117) and at said second end (118), said connectors (102, 105) maintaining said two steel plates (110, 115) at a respective spacing (82, 83) between each other at said ends (117, 118) and said at least one spacer (130) inaintaining said two steel plates (110, 115) at a second and larger spacing (Sl) between each other at said spacer (130)A supporting plate structure (100) for connection between an engine main structure (1) and an exhaust gas receiver (16), said plate structure (100) comprising: two opposite steel plates (110, 115), each having a first and a second end (117, 118) - at least one spacer (130) maintaining said two plates (110, 115) in a spaced apart relationship, said spacer (130) being arranged between said plates (110, 115) at a location (116 ) between said first (117) and second 118) end, and - a connector (102, 105) at said first end (117) and at said second end (118), said connectors (102, 105) maintaining said two steel plates (110, 115) at a respective spacing (82, 83) between each other at said ends (117, 118) and said at least one spacer (130) inaintaining said two steel plates (110, 115) at a second and larger spacing (Sl) between each other at said spacer (130)

Description

i DK 177325 B1

A LARGE TWO-STROKE DIESEL ENGINE AND A SUPPORTING PLATE STRUCTURE FOR CONNECTION BETWEEN AN ENGINE MAIN STRUCTURE AND AN EXHAUST GAS RECEIVER

5 FIELD OF THE INVENTION

The present invention relates to a large two-stroke diesel engine with an engine main structure, and to a supporting plate structure for connection between an 10 engine main structure and an exhaust gas receiver.

BACKGROUND OF THE INVENTION

The exhaust gas receiver of a large two-stroke diesel 15 engine is a highly loaded component that receives the hot (approximately 450°C) 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 20 significantly over 10 m long and have a diameter of up to 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 25 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 thick layer of insulating material, so that the temperature of the outside surface of the 30 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 no exposed engine parts have a 2 DK 177325 B1 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 5 temperature remains below 150°C.

The exhaust gas receivers are in the middle of their longitudinal extension, or at one end, supported by a rigid main support. Several flexible supports are 10 distributed along the length of the exhaust gas receiver 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 15 movement in the longitudinal direction of the exhaust gas receiver which is required to compensate for the thermal expansion/contraction of the exhaust gas receiver as it heats up/cools down.

20 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. One particular problem is vibrations of the flexible supports that inter alia give 25 rise to unwanted noise. Attempts have been made to solve this problem by applying welded reinforcing ribs to the flexible supports, thereby lowering their natural frequency; however, cracks have been experienced where the ribs are welded to the supports, and overall the 30 problem has not been solved to full satisfaction.

DE4309615 shows a connector for marine engine exhaust systems, with first and second plates mounted one above the other. A third plate is mounted in parallel to the 3 DK 177325 B1 lower plate to prevent a turning or the first and secoon plates relative to each other.

DISCLOSURE OF THE INVENTION 5

On this background, it is an object of the present invention to provide a supporting plate structure that at least partially solves the above problem, and this is done by increasing the lowest natural frequency of the 10 flexible supports without compromising the need for a reliable and durable plate structure.

This object is achieved by providing the flexible support as a pair of flexible steel plates arranged to extend 15 transversally to said longitudinal direction, the steel plates extending with their major faces opposite to each other at a varying spacing (SI, S2, S3) between the upper end and the lower end thereof, at least one spacer being arranged between the steel plates at a location between 20 the upper end and the lower ends to maintain the steel plates at a larger spacing (SI) at the spacer.

Further objects, features, advantages and properties of the exhaust gas receiver according to the invention will 25 become apparent from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present 30 description, the invention will be explained in more detail with reference to the exemplary embodiment shown in the drawings, in which: 4 DK 177325 B1

Fig. 1 is a view of the long side of a large two-stroke engine with the plate structure according to an embodiment of the invention,

Fig. 2 is a view of the rear end of the engine shown in 5 Fig. 1,

Fig. 3a is a perspective view of the end of an exhaust gas receiver supported by the plate structure according to an embodiment of the invention,

Fig. 3b is a side view of the embodiment of fig. 3a, 10 Fig. 3c is a plane view of the embodiment of fig. 3a,

Fig. 4 is a schematic side view of the plate structure when being mounted and where the exhaust gas receiver is in the cold state,

Fig. 5 shows schematically and out of scale a flash image 15 of the vibrating plate structure during operation of the engine, and

Fig. 6 shows for comparison how the lowest natural frequency of the plate structure can be varied.

20 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figs. 1 and 2 show the engine main structure 1 of a large two-stroke diesel engine in side view and end view, respectively. The engine is a uniflow low-speed two-25 stroke crosshead diesel engine of the crosshead type, which may be a propulsion system in a ship or an engine in a power plant. These engines have typically from 3 up to 14 cylinders in line. The engine is built up from a bedplate 2 with the main bearings for the crankshaft 30 (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.

c DK 177325 B1

O

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 5 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 10 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 of the exhaust gas receiver 16 by an exhaust passage. The cylinder frame 5 forms together 15 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 20 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 25 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 30 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 6 DK 177325 B1 electrically-driven auxiliary scavenge air blowers 13.

The auxiliary blowers assist the turbocharger compressor at low and medium load conditions.

5 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 10 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 15 exhaust gas receiver 16 during maintenance and overhaul.

The exhaust gas receiver 16 is supported by the scavenge air receiver 9 of the engine main structure 1. More specifically, the exhaust gas receiver 16 is at half its 20 length supported by a rigid main support 22 fixing the middle of the exhaust gas receiver relative to the scavenge air receiver 9; the main support 22 may alternatively be arranged at an end of the exhaust gas receiver 16. As shown, a plurality of flexible supports 25 100 according to the invention also for supporting the exhaust gas receiver are distributed along the length of the exhaust gas receiver on either side of the rigid support 22. The flexible supports 100 are each defined by a plate structure that follows any temperature-induced 30 lengthwise contraction or expansion of the exhaust gas receiver 16 in relation to the engine housing/scavenge air receiver 9 as the exhaust gas receiver 16 heats up or cools down. Total thermal expansion of the exhaust gas receiver 16 in the transverse direction, perpendicular to 7 DK 177325 B1 the plane of fig. 1, is relatively small due to the smaller dimension. To avoid any transverse vibrations of the exhaust gas receiver 16 the flexible supports 100 show little or no resiliency in the transverse direction 5 of the exhaust gas receiver 16.

Conventionally, one upright plate having a thickness in the order of 10-25 mm has been used for making the individual plate structures 100, and each upright plate 10 is conventionally welded to the scavenge air receiver 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. As mentioned in the introduction, undesired resonant vibrations of these 15 plate structures have been experienced in the engine's running range.

Fig. 3a shows the end portion of the elongated exhaust gas receiver 16 opposite the turbocharger 10 in greater 20 detail, with an upright supporting plate structure 100 according to the invention arranged between the exhaust gas receiver 16 and a mounting bracket 9' of the scavenge air receiver 9.

25 The novel plate structure 100 includes as seen better in fig. 3b two flexible steel plates 110, 115 extending in the transverse direction of the exhaust gas receiver 16 opposite each other between mounting devices 120, 125 that rigidly connect the plate structure 100 to the 30 exhaust gas receiver and scavenge air receiver 9, respectively. The thickness of the two plates may be the same, and may be selected broadly; plate thicknesses in the order of 5-10 mm will often be selected.

8 DK 177325 B1

The plates 110, 115 are preferably similar or identical, and each plate has two opposite major faces and side edges. The two steel plates 110, 115 are arranged with a major face of each plate opposite the major face of the 5 other plate. Each plate 110, 115 has an upper end 117 and a lower end 118, as shown in fig. 3c, and the plate structure 100 has a spacer 130 maintaining a central area 116 of the two plates 110, 115 in a spaced apart relationship, the spacer 130 being arranged between the 10 two plates 110, 115 at a location between the upper 117 and lower 118 end. A respective connector 102, 105 at the upper end and at the lower end maintain the two plates 110, 115 closer to each other at the upper and lower ends so that the plate structure 100 will have the shown, 15 outwardly bulging configuration. A location of the spacer 130 exactly halfway between the two ends 117, 118 is not essential for the invention as an outwardly bulging structure as shown in fig. 3b and with the plates 110, 115 fixed to each other by the spacers 130 will generally 20 give the desired technical properties of the plate structure 100.

The novel plate structure 100 will normally be mounted on a mounting flange 16' on the exhaust gas receiver 16 and 25 another lower mounting device 125 on a mounting bracket 9' of the engine main structure, which in the shown embodiment would be a bracket 9' on the scavenge air receiver 9. The two mounting devices are in the cold state of the engine in a horizontally offset position in 30 that the mounting flange 16' in the longitudinal direction of the exhaust gas receiver 9 will be located closer to the rigid support 22 than the lower mounting bracket 9', i.e. offset to the right in fig. 3b. The cold state horizontal distance or spacing between the upper 9 DK 177325 B1 mounting flange 16' and lower mounting bracket 9' is preferably selected such as to correspond to the relative longitudinal expansion of the exhaust gas receiver 16 with respect to the engine main structure, i.e. the 5 scavenge air receiver 9, when in the hot, operational state; in this manner the mounting flange 16' and the mounting bracket 9' will be located aligned and above each other with substantially no horizontal spacing . when the exhaust gas receiver 16 is at its working 10 temperature.

The plate structures 100 are installed prior to operation of the engine, i.e. with the aforementioned cold state horizontal spacing between the mounting flange 16' and 15 the mounting bracket 9', and serve as is conventional to support the exhaust gas receiver 16 and to assist in securing the exhaust gas receiver 16 in place during rolling movements of a ship.

20 It is desirable that the plates 110, 115 forming the plate structure 100 in the hot state be located symmetrically with respect to a hot state axis A of symmetry of the plate structure 100, as is shown in fig.

3b. To this end the plate structure 100 is elastically or 25 plastically deformed or bent into a slightly askew or bend configuration in the process of mounting the plate structure 100 to the offset mounting flange 9' and mounting bracket 16' in the cold state. After mechanically forcing the plate structure 100 into 30 alignment with the non-aligned off-set flange 9' and bracket 16' is the plate structure 100 connected with the mounting devices on the flange 16' and bracket 9' , respectively, wherein the plate structure 100 will assume an askew configuration as schematically illustrated in 10 DK 177325 B1 fig. 4. As the exhaust gas receiver 16 heats up and expands to the point where the flange 16' and bracket 9' are no longer horizontally offset the bending forces applied during mounting will be reduced to a minimum at 5 which point the primary forces on the plate structure 100 are those that are due to the vertical load resulting from the weight of the exhaust gas receiver 16 combined with the forces arising due to engine vibrations.

10 In respect to the connection with the plate structure 100 bolts 106 are tightened to prevent any free rotational movement of the plate ends 117, 118 with respect to the mounting devices 120, 125. Metal bar connectors 102, 105 may be arranged between the plates 110, 115 at their 15 upper and lower ends 117, 118, and the same bolts may be used for connecting the plates to each other via the connectors 102, 105 and for connecting the plate structure 100 to the flange 16' and bracket 9' , respectively, via the mounting devices 120, 125.

20

Additionally, transverse to the plate structure 100 and about halfway (in area 116) between the upper and lower ends 117, 118 a row of spacers 130, which may comprise bolts with bolt heads 132, are arranged to fix the plates 25 110, 115 in relation to each other and to ensure that there is no movement of the plates 110, 115 to or from each other at the spacers 130. The spacers 130 maintain the plate 110, 115 with a mutual spacing SI in area 116 that is larger than the mutual spacing S2, S3 between the 30 plates 110, 115 at their upper and lower ends 117, 118, respectively, as also shown by the enlarged parts in fig.

3b; S2 may be the same as S3. In this manner the plate structure 100 will assume the outwardly bulging geometrical configuration shown in fig. 3b and will n DK 177325 B1 vibrate transversally as a column formed as a truss structure, as shown in fig. 5; it will be understood that this vibration will be in the longitudinal direction of the exhaust gas receiver 16. The spacers 130 may be 5 tubular metal tubes with internal, headed bolts extending through holes formed in the plates 110, 115 and cooperating with nuts to maintain or fix the spacing SI.

In this manner a purely mechanical connection requiring no welding can be formed.

10

Fig. 5 shows schematically a flash image of the vibrating plate structure 100 during operation of the engine. The amplitude A of the plate structure 100 vibrations is affected or controlled by the high stiffness of the plate 15 structure 100 midway between the upper and lower end 110, 115 which again may be controlled by the selected plate thicknesses and by the ratio of spacing SI to spacing S2 and S3, respectively. Fig. 6 shows for comparison how the lowest natural frequency of the plate structure 100 can 20 be varied by using spacers 130 providing a desired relative spacing SI between the steel plates 110, 115 midway between their ends 117, 118. The frequency values are compared for pairs of plates having different thickness; as will be seen, the lowest natural frequency 25 generally increases with an increased spacing SI. Using steel plates with larger thickness will also increase the lowest natural frequency. As can be seen, even using a plate thickness of half the conventional thickness of 16 mm will provide advantages; hence, a materials saving is 30 possible through the increased stiffness of the plate structure 100 compared to the conventional single plate structures .

12 DK 177325 B1

It is noted that the plate structure 100 may be formed by mechanically forcing two flat plates 110, 115 together and then connecting them using connectors 102, 105 at their ends 117, 118, thus providing a stressed or biased 5 outwardly bulging plate structure 100 for mounting between the exhaust gas receiver 16 and the scavenge air receiver 9. Alternatively, the two plates 110, 115 may be rolled or otherwise processed to assume a natural unbiased shape as illustrated in fig. 3b, after which 10 they are connected to each other by bolts 106 and spacers 130.

Although the present invention has been described in detail for purpose of illustration, it is understood that 15 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

13 DK 177325 B1

A large two-stroke diesel engine including: 5 a main structure (1) for the engine, an elongated exhaust gas receiver (16) with one or more inputs for the engine exhaust and with one or more outlets for the engine exhaust, 10 a primary support (22) and a number of upright plate structures (100) provided below the exhaust gas receiver (16) to support the exhaust gas receiver (16) on the main structure (1) of the engine 15 - which upright plate structures (100) are distributed along the length of the exhaust gas receiver (16), which upright plate structures (100) each have an upper end (117) mounted on the exhaust gas receiver (16) and a lower end (118) mounted on the main structure (1) of the engine; 25, wherein at least one of the sheet structures (100) includes: - a pair of flexible steel sheets (110, 115) secured together at the upper end (117) and at the lower end (118) intended to extend transversely 30 along the longitudinal direction of the exhaust gas receiver (16) - which steel plates (110, 115) extend with their main faces to each other, the distance between

The steel plates are increased from the upper end (117) and the lower end (118), and - at least one spacer (130) provided between the steel plates (110, 115) in a position between the upper end (117) ) and the lower end (118) - which at least one spacer (130) is adapted to fix the distance (SI) between the steel plates (110, 10 115) at the spacer (130).

A large two-stroke diesel engine according to claim 1, wherein the at least one spacer (130) is arranged to provide the largest possible distance (SI) between the plates (110, 115) halfway, or about halfway, between the upper (117) and lower (118) end.

A large two-stroke diesel engine according to any one of the preceding claims, wherein the plate structures (100) are flexible in the longitudinal direction of the exhaust gas receiver (16) to accommodate a thermal expansion of the exhaust gas receiver (16) relative to the main structure of the engine (1).

A large two-stroke diesel engine according to any one of the preceding claims, including mounting devices (120, 125) for fixed mounting of the plate structures (100) to the exhaust gas receiver (16) at the upper end (117) and to the main structure (1) of the engine at the lower end 30 (118).

A large two-stroke diesel engine according to any one of the preceding claims, wherein the at least one plate structure

15 DK 177325 B1 (100) steel plates (110, 115) are held apart by the at least one spacer (130).

A large two-stroke diesel engine according to any one of the preceding claims, wherein the at least one spacer (130) provides a mechanical connection between the steel plates (110, 115).

A large two-stroke diesel engine according to the preceding claims, wherein the at least one spacer (130) at its longest defines the distance (S1) between the steel plates (110, 115) at the spacer (130).

A large two-stroke diesel engine according to any one of the preceding claims, wherein the at least one spacer (130) establishes a mechanically fixed spacer (SI) without welding between the steel plates (110, 115) at the spacer (130).

A large two-stroke diesel engine according to any one of the preceding claims, wherein the plate structures (100) are supported by a rinsing air receiver (9) for the main structure (1) of the engine.

A large two-stroke diesel engine according to any one of the preceding claims, wherein a plurality of spacers (130) are located on a row. 30