WO2009127232A1

WO2009127232A1 - Scuffing detection

Info

Publication number: WO2009127232A1
Application number: PCT/EP2008/003090
Authority: WO
Inventors: Henrik Rolsted Jensen; Jesper Weis Fogh; Jens Bagge
Original assignee: Man Diesel Filial Af Man Diesel Se, Tyskland
Priority date: 2008-04-17
Filing date: 2008-04-17
Publication date: 2009-10-22
Also published as: KR101363340B1; CN102027219B; CN102027219A; KR101267506B1; KR20120126119A; KR20110007189A; JP2011517746A; JP4729138B2

Abstract

A method for detection of pre-scuffing events in a large multicylinder two-stroke diesel engine by recognizing the characteristic temperature fluctuations of pre-scuffing events. The temperature fluctuations are characterized by the time span between their peaks and the magnitude of the fluctuations. Automatic countermeasures may be initiated after detection of the pre-scuffing event. The countermeasures may automatically be ended.

Description

SCUFFING DETECTION

FIELD OF THE INVENTION

The present invention relates to a method for detecting scuffing in a large two-stroke diesel engine, in particular to method for detecting a pre-scuffing condition, a method for detecting a scuffing condition and to a method for detecting the end of a scuffing condition.

BACKGROUND OF THE INVENTION

Disturbances in the operation of large two-stroke diesel engines can lead to a reduction of power and to damage to the cylinders and pistons. The loss of power can be significant and if the engine has to be taken out of operation this can cause great problems, for example when the large two-stroke diesel engine is used as the main source of power in an oceangoing vessel.

The piston rings and liner surface experience all three wear regimes as described by the Stribeck curve (figure 1) relating the (viscosity, load, speed) to the coefficient of friction. These three regimes are Boundary Lubrication, Mixed Lubrication and Hydrodynamic Lubrication. Hydrodynamic lubrication is the condition where there is full separation of the surfaces by an oil film. If the load is only partly carried by the oil film pressure and partly by contact by asperities the condition is named mixed lubrication. If the complete load is carried by asperities and the only separation is a molecular thin oil film, the condition is known as boundary lubrication.

In large two-stroke diesel engines boundary lubrication is always present to a small extent around top dead Center (TDC) , where the velocity of the piston approaches zero. In case bore polish is taking place the amount of boundary lubrication may rise to a level where scuffing will occur.

The existing countermeasures are costly since cylinder lubrication oil is relatively expensive and power reduction is also undesirable. Thus, it is important to determine whether scuffing condition has ceased to exist so that the countermeasures can be canceled in good time.

DISCLOSURE OF THE INVENTION

Our research has shown that the change in friction coefficient, when the boundary lubrication amounts a critical value, will result in a unique temperature fluctuation pattern of the liner surface temperature.

This condition will exist for a period of approximately

10 to 20 minutes before any scuffing takes place. In this period proper counteractions can be taken manually or automatically by connecting the alarm system to the cylinder lubricator system.

When a pre-scuffing condition is detected the cylinder lubrication oil dosage can be increased relative to the normally required dosage to prevent a scuffing state to occur. Another possibility is to connect the alarm system to the electronic control system of the engine, which then can reduce the load on the cylinder concerned. This condition is called "High Friction Condition", cf. figure. If no proper actions are taken this condition will develop into scuffing with heavy wear of the cylinder liner. The liner temperature in the scuffing condition is stable at a high level.

On this background, it is an object of the present invention to provide a method for detecting a pre- scuffing condition.

This object is achieved by providing a method for detecting a pre-scuffing condition in a large multi- cylinder turbocharged two-stroke diesel engine, the method comprising continuously or intermittently measuring the cylinder wall temperature in the upper region of the cylinders, determining if the temperature development of a cylinder fluctuates, and issuing a pre- scuffing alarm when the peaks or the dips of the temperature fluctuations of the cylinder concerned are separated by a time span that falls in a predetermined range and the temperature difference between the peaks and the dips of the temperature fluctuation exceeds a predetermined threshold.

Our research has shown that the time span between the peaks or between the dips of the cylinder wall temperature fluctuations and the magnitude of the fluctuations are the most characteristic aspects of pre- scuffing events. By ensuring that time span between the peaks or dips of the temperature fluctuations falls within the predetermined range and by ensuring that the temperature difference between the peaks and the dips exceeds a predetermined threshold it is possible to ensure that pre-scuffing events are reliably issued when pre-scuffing occurs with a minimum of false alarms and a minimum of pre-scuffing events for which no alarm is issued.

Preferably, a pre-scuffing alarm is only issued when at least a sequence with a predetermined number of the fluctuations occurs. Thus, the number of false pre- scuffing alarms can be further reduced.

The method may further comprise increasing cylinder lubrication level to a level above the level for normal operation for the cylinder for which the alarm is issued. This countermeasure serves to prevent further pre- scuffing events.

The method may further comprise decreasing load level to a level below the level for normal operation for the cylinder for which the alarm is issued. This countermeasure serves to prevent further pre-scuffing events.

It is another object of the invention to provide a method for use in a large multi-cylinder two-stroke diesel engine for determining when to return to normal operation when countermeasures have been taken after a pre-scuffing cylinder alarm has been issued for one of the cylinders, the method comprising determining the time span that has passed since initiation of the countermeasures, and automatically returning to normal operation of the cylinder for which the pre-scuffing alarm has been issued after the time span has exceeded a predetermined threshold. By automatically returning to normal operating condition expenses and inconveniences associated with the pre- scuffing alarm condition can be kept to a minimum.

Preferably, the return to normal operation is performed gradually.

It is another object of the invention to provide a method for detecting a scuffing condition in a large multi- cylinder turbocharged two-stroke diesel engine, the method comprising continuously or intermittently measuring the cylinder wall temperature in the upper region of the cylinders, and issuing a scuffing alarm for a cylinder when the cylinder wall temperature of a cylinder is higher than the average temperature of the other cylinders by more than a predetermined value, or the cylinder wall temperature of a cylinder exceeds a predetermined alarm temperature.

By providing a method for detecting a scuffing condition countermeasures can be taken to avoid further damage to the engine.

Preferably, a scuffing alarm is only issued when the cylinder wall temperature increase of a cylinder occurred with a temperature gradient that exceeds a predetermined threshold.

The method may further comprise automatically increasing cylinder lubrication from a normal level to an increased level and reducing load of the cylinder concerned from a normal level to a reduced level for the cylinder for which the alarm was issued. It is another object of the invention to provide method for determining that a scuffing event in a large multi- cylinder two-stroke diesel engine has ended, comprising continuously or intermittently measuring the cylinder wall temperature in the upper region of the cylinders, determining if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued exceeds the average cylinder wall temperature of the other cylinders by a value less than a given threshold, or the cylinder wall temperature of the cylinder for which a scuffing alarm was issued is below a predetermined fixed cylinder wall alarm temperature by a predetermined margin .

By automatically detecting that a scuffing and has ended, measures can be taken to return to normal operating condition and expenses and inconveniences associated with the pre-scuffing alarm condition can be kept to a minimum.

Preferably, the method further comprises automatically returning to normal operation of the cylinder for which the scuffing alarm was issued with a predetermined delay from the determination of the end of the scuffing event.

It is another object of the invention to provide an apparatus to carry out a method for detecting a pre- scuffing condition in a large two-stroke diesel engine. The apparatus has at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine if the temperature development of a cylinder fluctuates, and is configured to issue a pre-scuffing alarm when the peaks or the dips of the temperature fluctuations of the cylinder concerned are separated by a time span that falls in a predetermined range and the temperature difference between the peaks and the dips of the temperature fluctuation exceeds a predetermined threshold.

It is yet another object of the invention to provide an apparatus to carry out a method for returning to a normal operating condition after countermeasures have been issued in connection with a pre-scuffing alarm, the apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine the time span that has passed since initiation of the countermeasures, and the processor is configured to automatically returning to normal operation after the time span has exceeded a predetermined threshold.

It is a further object of the invention to provide an apparatus to carry out a method for issuing a scuffing alarm in a large multi-cylinder two-stroke diesel engine, the apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to issue a scuffing alarm for a cylinder when the cylinder wall temperature of a cylinder is higher than the average temperature of the other cylinders by more than a predetermined value, or when the cylinder wall temperature of a cylinder exceeds a predetermined alarm temperature.

It is a further object of the invention to provide an apparatus to carry out a method for automatically detecting that a scuffing condition of a cylinder has ceased to exist in a large two-stroke diesel engine, the apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued exceeds the average cylinder wall temperature of the other cylinders by a value less than a given threshold, or if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued is below a predetermined fixed cylinder wall alarm temperature by a predetermined margin.

Further objects, features, advantages and properties of the method and apparatus 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 embodiments shown in the drawings, in which:

figure 1 is a graph illustrating various lubrication regimes, figure 2 is a detailed cross-sectional view of the top of a single cylinder of a multicylinder engine, figure 3 is a diagrammatic overview of the cylinders, the injection system, the cylinder lubrication system, the temperature sensing system and the electronic control system of an engine according to an embodiment of the invention, and figure 4 is a graph illustrating the cylinder wall temperature development of the cylinder showing pre- scuffing events.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 illustrates the so called Stribeck curve. The piston rings and liner surface experience all three wear regimes as described by this curve relating the (viscosity, load, speed) to the coefficient of friction. These three regimes are Boundary Lubrication, Mixed Lubrication and Hydrodynamic Lubrication. Hydrodynamic lubrication is the condition where there is full separation of the surfaces by an oil film. If only partly of the load is carried by the oil film pressure and partly by contact by asperities the condition is named mixed lubrication. If the complete load is carried by asperities and the only separation is molecular thin oil film, the condition is known as boundary lubrication.

In large two-stroke diesel engines boundary lubrication is always present to a small extent around top dead Center (TDC) , where the velocity of the piston is approaching zero. In case bore polish is taking place the amount of boundary lubrication may rise to a level where scuffing will occur.

The occurrence of bore polish is in this document labeled a pre-scuffing event.

Figure 2 illustrates one of the cylinders 10 of a large multicylinder two-stroke diesel engine of the crosshead type. A piston 12 moves up and down in the cylinder 10. The top of the cylinder is covered by a cylinder cover 14. The cylinder cover 14 is provided with an exhaust valve 16 and with fuel injectors 18.

Temperature sensors 20 and 20' are provided in the area where the movement of the piston 12 is reversed, the so- called Top Dead Center (TDC) . The temperature sensors 20,20' are located in the cylinder liner wall, and connected to an electronic control system ECS of the engine (figure 3) via signal cables 22. The temperature sensors 20,20' measure the cylinder wall temperature in the upper area of the perspective cylinder and the signal of the temperature sensors is transferred by the data cables 22 to the electronic control system. In the shown embodiment there are two diametrically opposite temperature sensors 20,20' . However, it would also be possible to use only a single temperature sensor 20 per cylinder or to use more than two temperature sensors per cylinder that are distributed along the circumference of the cylinder.

Cylinder lubricator ports 26 are also provided along the circumference of the cylinder. Typically three cylinder lubrication ports 26 are provided for each cylinder, although other numbers of cylinder lubrication ports could be used. The cylinder lubrication ports 26 are provided with cylinder oil by a cylinder oil pump 24 associated with each cylinder. The cylinder oil pump 24 adjusts the dosage of the cylinder oil to the operating conditions of the engine. During normal operation the dosage is set to be no more than adequate since cylinder oil is relatively expensive. The dosage will be influenced by the fuel quality and be higher when low- quality fuel with a high sulfur content is used and depends on the load and running speed of the engine or on the load of a specific cylinder.

Figure 3 shows an engine according to an embodiment of the invention with five cylinders 10. The number of cylinders in this embodiment merely exemplary and invention could be used on multi-cylinder large two- stroke diesel engines with any other number of cylinders.

The temperature sensors 20, 20' of each of the cylinders 10 are connected via the signal cables 22 to the electronic control system ECS of the engine. The cylinder lubrication pumps 24 of each of the cylinders 10 are also connected to the electronic control system. The same applies to be fuel injection system that is connected to the electronic control system ECS via signal cables 28.

The cylinder wall temperature values supplied by the temperature sensors 20,20' of the cylinders 10 are measured and evaluated by the electronic control system. The electronic control system includes at least one processor that is configured to measure and analyze the cylinder wall temperature signals. The measurement of the cylinder wall temperatures may be intermittent, for example once every second or continuous.

The processor analyzes the cylinder wall temperatures of each of the cylinders 10 and analyzes the development of these on the cylinder wall temperatures of each of the cylinders 10. The processor issues a pre-scuffing alarm if any of the cylinders displays a temperature development that is typical for a pre-scuffing event. Figure 4 illustrates a typical pre-scuffing event followed by hypothetical scuffing event (indicated by the interrupted line) for cylinder number four. The pre- scuffing event commences by cylinder wall temperature fluctuations with a magnitude of fluctuation in the range between approximately 25 to approximately 65°C.

The time span between the peaks of the cylinder wall temperature fluctuations (or for that matter between the dips) is typically in the range between approximately 6 to approximately 18 minutes. The period of time in which these events take place in figure 4 is labeled "high friction condition". In this state friction is increased but not to the level of friction that occurs during actual scuffing.

The range of the magnitude of the cylinder wall temperature fluctuations may vary from engine to engine may depend on engine size and design and can be determined empirically. This also applies to the range of the time span between the peaks of the temperature fluctuations .

The processor is configured to issue a pre-scuffing alarm when it has determined that the temperature fluctuations match the characteristic of a scuffing event. Thus, the processor determines whether the time span between the peaks of the fluctuation falls within the predetermined range and determines whether the temperature fluctuations exceed a predetermined magnitude.

If this determination is positive the processor issues a pre-scuffing alarm and in an embodiment the processor will also automatically initiate pre-scuffing event countermeasures . These pre-scuffing event countermeasures may include increasing the cylinder lubrication oil dosage to a level above that of normal operation. This increase is effected by a signal from the electronic engine control system ECS to the cylinder lubrication pump 24 of the cylinder for which the pre-scuffing alarm has been issued. The pre-scuffing event countermeasures may also include reducing the load on the cylinder for which the alarm has been issued. This countermeasure is effected by the electronic control system ECS by changing the amount and/or timing of the fuel injection via the respective signal cable 28. The pre-scuffing event countermeasures may also include reducing the engine speed.

The processor is in an embodiment configured to apply a stricter control for the detection of a pre-scuffing event. The extra restriction is in the form of a minimum number of consecutive cylinder wall temperature fluctuations that have to occur before an alarm is issued. A minimum number of consecutive fluctuations could be set to be two or three fluctuations (at least two of three peaks) .

In an embodiment the processor is also configured to automatically determine when to return to normal operation when countermeasures have been taken after a pre-scuffing cylinder alarm has been issued for one of the cylinders 10. Hereto, the processor determines the time span that has passed since initiation of the countermeasures, and automatically returns to normal operation of the cylinder 10 for which the pre-scuffing alarm has been issued after the time span has exceeded a predetermined threshold. The return to normal operation is performed gradually.

If no countermeasures are taken the pre-scuffing events will eventually result in a scuffing condition. The cylinder temperature development of a scuffing event is illustrated by the interrupted line of figure 4. If a scuffing event occurs (e.g. because pre-scuffing events were not detected or the pre-scuffing alarm countermeasure were inadequate) the processor is configured to issue a scuffing alarm when the temperature gradient Δt/ΔT of the cylinder concerned exceeds a given threshold for a minimum amount of time. Also if the cylinder wall temperature of a given cylinder exceeds the maximum alarm set point a scuffing condition alarm is issued.

The processor is configured to detect that a scuffing condition is present and automatically issues a scuffing alarm. Further, the processor is in embodiment configured to automatically apply countermeasures, such as increasing the cylinder lubrication oil dosage significantly, for example to maximum level when a scuffing event is detected. The countermeasures may further include a reduction on the load of the cylinder for which the alarm is issued through manipulation of the fuel injection of the cylinder concerned. The processor may further be configured to automatically reduce the engine speed as a countermeasure after a scuffing alarm has been issued.

The processor may in embodiment also be configured to determine when a scuffing event has ended. In this case the processor is configured to cancel the scuffing alarm when the cylinder temperature of the cylinder for which the alarm was issued drops below the maximum alarm set point by a predetermined margin. The processor can also be configured to automatically end the scuffing countermeasures after a predetermined delay from the point of time at which the processor has determined that the scuffing event has ended. The automatic ending of the scuffing countermeasures by the processor can be performed gradually or step-by-step.

The invention has numerous advantages. Different embodiments or implementations may yield one or more of the following advantages. It should be noted that this is not an exhaustive list and there may be other advantages which are not described herein. One advantage of the invention is that it provides a reliable method for detecting pre-scuffing events. Another advantage of the invention is that it provides for automatic initiation of countermeasures upon detection of pre-scuffing events. A further advantage of the invention is that it provides for automatic ending of countermeasures to a pre-scuffing event. Another advantage of the invention is that it provides for a reliable method for detecting a scuffing event. Another advantage of the invention is that it provides for a method for automatically initiating countermeasures upon detection of a scuffing event. A further advantage of the invention is that it provides for automatic detection of the ending of a scuffing event .

The term "comprising" as used in the claims does not exclude other elements or steps. The term "a" or "an" as used in the claims does not exclude a plurality. Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. Moreover, it should be appreciated that those skilled in the art, upon consideration of the present disclosure, may make modifications and/or improvements on the device hereof and yet remain within the scope and spirit hereof as set forth in the following claims.

Claims

CLAIMS :

1. A method for detecting a pre-scuffing condition in a large multi-cylinder turbocharged two-stroke diesel engine, said method comprising

continuously or intermittently measuring the cylinder wall temperature in the upper region of the cylinders,

determining if the temperature development of a cylinder fluctuates, and

issuing a pre-scuffing alarm when the peaks or the dips of the temperature fluctuations of the cylinder concerned are separated by a time span that falls in a predetermined range and the temperature difference between the peaks and the dips of the temperature fluctuation exceeds a predetermined threshold.

2. A method according to claim 1, wherein a pre-scuffing alarm is issued when at least a sequence with a predetermined number of said fluctuations occurs.

3. A method according to claim 1 or 2, further comprising increasing cylinder lubrication level to a level above the level for normal operation for the cylinder for which the alarm is issued.

4. A method according to any of claims 1 to 3, further comprising decreasing load level to a level below the level for normal operation for the cylinder for which the alarm is issued.

5. A method for use in a large multi-cylinder two-stroke diesel engine for determining when to return to normal operation when countermeasures have been taken after a pre-scuffing cylinder alarm has been issued for one of the cylinders, said method comprising:

determining the time span that has passed since initiation of the countermeasures, and

automatically returning to normal operation of the cylinder for which the pre-scuffing alarm has been issued after said time span has exceeded a predetermined threshold.

6. A method according to claim 6, wherein said return to normal operation is performed gradually.

7. A method for detecting a scuffing condition in a large multi-cylinder turbocharged two-stroke diesel engine, said method comprising:

continuously or intermittently measuring the cylinder wall temperature in the upper region of the cylinders, and

issuing a scuffing alarm for a cylinder when:

the cylinder wall temperature of a cylinder is higher than the average temperature of the other cylinders by more than a predetermined value,

or the cylinder wall temperature of a cylinder exceeds a predetermined alarm temperature.

8. A method according to claim 7, wherein a scuffing alarm is only issued when the cylinder wall temperature increase of a cylinder occurred with a temperature gradient that exceeds a predetermined threshold.

9. A method according to claim 7 or 8, further comprising automatically increasing cylinder lubrication from a normal level to an increased level and reducing load of the cylinder concerned from a normal level to a reduced level for the cylinder for which the alarm was issued.

10. A method for determining that a scuffing event in a large multi-cylinder two-stroke diesel engine has ended, comprising:

determining if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued exceeds the average cylinder wall temperature of the other cylinders by a value less than a given threshold, or

the cylinder wall temperature of the cylinder for which a scuffing alarm was issued is below a predetermined fixed cylinder wall alarm temperature by a predetermined margin.

11. A method according to claim 11, further comprising returning to normal operation of the cylinder for which the scuffing alarm was issued with a predetermined delay from the determination of the end of the scuffing event.

12. An apparatus for detecting a pre-scuffing condition in a large multi-cylinder turbocharged two-stroke diesel engine, said apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine if the temperature development of a cylinder fluctuates, and is configured to issue a pre-scuffing alarm when the peaks or the dips of the temperature fluctuations of the cylinder concerned are separated by a time span that falls in a predetermined range and the temperature difference between the peaks and the dips of the temperature fluctuation exceeds a predetermined threshold.

13. An apparatus for use in a large multi-cylinder two- stroke diesel engine for determining when to return to normal operation when countermeasures have been taken after a pre-scuffing cylinder alarm has been issued for one of the cylinders, said apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine the time span that has passed since initiation of the countermeasures, and said the processor is configured to automatically return to normal operation after said time span has exceeded a predetermined threshold.

14. An apparatus for detecting a scuffing condition in a large multi-cylinder turbocharged two-stroke diesel engine, said apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to issue a scuffing alarm for a cylinder when the cylinder wall temperature of a cylinder is higher than the average temperature of the other cylinders by more than a predetermined value, or when the cylinder wall temperature of a cylinder exceeds a predetermined alarm temperature .

15. An apparatus for determining that a scuffing event in a large multi-cylinder two-stroke diesel engine has ended, said apparatus having at least one temperature sensor for each cylinder in the upper region of the cylinder wall coupled to a processor that is configured to determine if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued exceeds the average cylinder wall temperature of the other cylinders by a value less than a given threshold, or if the cylinder wall temperature of the cylinder for which a scuffing alarm was issued is below a predetermined fixed cylinder wall alarm temperature by a predetermined margin.

16. A large two-stroke diesel engine with a device according to any of claims 13 to 16.