WO2015132453A1 - Method and system for detecting a hydrostatic lock during the engine start - Google Patents

Method and system for detecting a hydrostatic lock during the engine start Download PDF

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Publication number
WO2015132453A1
WO2015132453A1 PCT/FI2015/050050 FI2015050050W WO2015132453A1 WO 2015132453 A1 WO2015132453 A1 WO 2015132453A1 FI 2015050050 W FI2015050050 W FI 2015050050W WO 2015132453 A1 WO2015132453 A1 WO 2015132453A1
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WO
WIPO (PCT)
Prior art keywords
acceleration
speed measurement
crankshaft
engine
starting event
Prior art date
Application number
PCT/FI2015/050050
Other languages
French (fr)
Inventor
Daniele GRANÀ
Original Assignee
Wärtsilä Finland Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wärtsilä Finland Oy filed Critical Wärtsilä Finland Oy
Priority to EP15705338.0A priority Critical patent/EP3114341A1/en
Publication of WO2015132453A1 publication Critical patent/WO2015132453A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N9/00—Starting of engines by supplying auxiliary pressure fluid to their working chambers
    • F02N9/04—Starting of engines by supplying auxiliary pressure fluid to their working chambers the pressure fluid being generated otherwise, e.g. by compressing air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/04—Introducing corrections for particular operating conditions
    • F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
    • F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M15/00—Testing of engines
    • G01M15/04—Testing internal-combustion engines
    • G01M15/042—Testing internal-combustion engines by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12
    • G01M15/046—Testing internal-combustion engines by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12 by monitoring revolutions
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/16—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by evaluating the time-derivative of a measured speed signal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B21/00—Engines characterised by air-storage chambers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/10—Parameters related to the engine output, e.g. engine torque or engine speed
    • F02D2200/1012—Engine speed gradient
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02N—STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR
    • F02N2200/00—Parameters used for control of starting apparatus
    • F02N2200/02—Parameters used for control of starting apparatus said parameters being related to the engine
    • F02N2200/022—Engine speed
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
    • G01P3/42—Devices characterised by the use of electric or magnetic means
    • G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
    • G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
    • G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to starting event systems for a reciprocating combustion engine that has a control unit for controlling and monitoring different functions of the engine. Especially the invention relates to starting of reciprocating combustion engines.
  • the reciprocating combustion engine contains cylinders wherein fuel is burned in order to move pistons in the cylinders.
  • the cylinder and piston provide a chamber for burning the fuel.
  • the pistons are connected to the crankshaft in order to rotate it.
  • the cylinder/s of the engine may contain undesired liquid like water or oil due to challenging environmental conditions (for example through intake air) or leakage in the engine.
  • the undesired liquid may cause a state that is called hydrostatic lock.
  • the hydrostatic lock occurs when a volume of liquid greater than the volume of the cylinder at its minimum, like the chamber's volume at the end of the piston's stroke, enters the cylinder. Since most common liquids are incompressible, the piston cannot complete its travel due an increase in cylinder pressure well above ordinary operating pressures. This means that either the engine must stop rotating or a mechanical failure occurs.
  • a starting event system for a reciprocating combustion engine is equipped with a speed measurement arrangement and a control unit.
  • the control is in connection with the speed measurement arrangement to receive speed measurement data of a crankshaft of the engine.
  • the control unit has an acceleration calculation unit to calculate acceleration of the crankshaft by using the received speed measurement data, and the starting event system is further provided with an air compression device and an air delivery arrangement to deliver the compressed air into cylinders of the engine in order to rotate the crankshaft slowly.
  • the control unit is further provided with an detector unit that is in connection with the acceleration unit in order to detect accelerations of the crankshaft.
  • the detector unit is further arranged to detect a hydrostatic lock in at least one cylinder of the engine utilizing the detected accelerations.
  • Figure 1 illustrates an example of a starting event system for a reciprocating combustion engine according to the invention
  • Figure 2 illustrates a schematic diagram of acceleration of the crankshaft
  • Figure 3 illustrates a flow diagram example of a method according to the invention
  • FIG. 1 illustrates an example of an embodiment of the invention.
  • a starting event system for a reciprocating combustion engine 1 is equipped with a speed measurement arrangement that can, for example, be a speed sensor 8 and formations or marks on the edge of the flywheel 9.
  • the flywheel is in connection with the crankshaft 6 of the engine.
  • the starting event system is also provided with a control unit 7 that is in connection with the speed measurement arrangement 8, 9 to receive speed measurement data of the crankshaft.
  • the control unit 7 has an acceleration calculation unit 10 to calculate acceleration of the crankshaft by using the received speed measurement data.
  • the starting event system is further provided with an air compression device 1 1 that comprises of an air compressor 12 and a tank 13 for the compressed air.
  • an air delivery arrangement 14, 15, 16 to deliver the compressed air into cylinders 2 of the engine in order to rotate the crankshaft 6 slowly.
  • the tank can, for example, be connected to several engines for delivering the compressed air to them.
  • the use of the compressed air is practical since it suits for retrofit installation for existing engines, and it also suits as equipment for new engines. Since other gases can also be used instead of air, the air compression device and the air deliver arrangement mean in this context to be suitable for other suitable gases as well. Therefore the compressed air means any compressed gas in this context as well.
  • the control unit has a detector unit 19 that is in connection with the acceleration calculation unit 10 in order to detect accelerations of the crankshaft.
  • the detector unit 19 is further arranged to detect a hydrostatic lock in at least one cylinder of the engine utilizing the detected accelerations.
  • the cylinder 2 and a piston 3 provide a combustion chamber 4 in the cylinder for burning fuel which causes movement of the piston 3.
  • the piston is in connection with the crankshaft in order to rotate it.
  • the compressed air can, for example, be transferred into combustion chamber 4 through an inlet 16 in a cylinder head 5.
  • the idea is that if there's a hydrostatic lock inside the combustion chamber, the acceleration of the crankshaft is noticeable. Actually, the crankshaft may even stop to move at a certain point just because the inertia force of the system is bigger than the force given by the compressed air. It is more likely that the hydrostatic lock occurs when the volume of the combustion chamber is at it's minimum volume 17. So, acceleration of the crankshaft means slowing down and speeding up in this context.
  • the compressed air is used to rotate the crankshaft during starting of the reciprocating combustion engine 1. It is difficult to control the compressed air system in order to make the crankshaft accelerate smoothly due to inertia of the system.
  • the acceleration can be calculated from the speed measurement by calculating derivatives of the speed measurement data.
  • the calculation of the derivatives may, for example, be obtained by a simple embodiment of calculating ⁇ / ⁇ wherein v is speed and t is time.
  • the detector unit 19 comprises a normal acceleration value, and the detection of the hydrostatic lock occurs when the calculated acceleration is above the normal acceleration value.
  • the calculation is made in the acceleration calculation unit 10.
  • the detector unit 19 that is in connection with the acceleration calculation unit 10 comprises a normal acceleration value, which is a normal acceleration of the crankshaft, mostly due to the said pendulum effect.
  • the normal acceleration is a predetermined acceleration, representing normal starting event of the reciprocating combustion engine without a hydrostatic lock. It can be obtained, for example, by testing, and being for example an average acceleration of pendulum effect.
  • the predetermined acceleration is saved in order to compare the predetermined acceleration to the calculated acceleration.
  • the detection of the hydrostatic lock occurs when the calculated acceleration is above the normal acceleration value.
  • the detection of the hydrostatic lock may occur when the calculated acceleration is at least 50% over the normal acceleration value. If the acceleration remains within a certain limit, i.e. it is normal acceleration; it can be presumed that the engine doesn't have any hydraulic lock. Other possible ranges are, for example at least 40% and at least 60%.
  • the air delivery arrangement comprises a distribution piping 14 for connecting the air compression device 1 1 to at least two of the cylinders. At least two cylinders are needed to rotate the crankshaft in four stroke engines.
  • the distribution piping comprises cylinder specific valves 15 for controlling admission of the compressed air into the respective cylinder.
  • control unit 7 can be connected to the valves 15 for controlling operation of the valves
  • the engine 1 comprises an absolute rotary encoder 18 that is connected with the control unit.
  • the absolute rotary encoder is a device that can determine the crank angle of the engine even when the engine is at rest.
  • the absolute rotary encoder can be connected to the crankshaft.
  • this publication discloses the air delivery arrangement and it's control arrangement in a more detailed manner than Figure 1.
  • Another possible embodiment is to use a specific cam on the crankshaft for indicating the crank angle and moments to open the each valve 15. Further, the crank angle information may also be obtained from a camshaft of the engine.
  • Figure 2 shows a schematic view of a normal acceleration 20 of the cranksaft and acceleration 21 of the crankshaft if the hydrostatic lock occurs in at least one cylinder of the reciprocating combustion engine.
  • the normal acceleration is showed as a solid line, and the acceleration due to the hydrostatic lock is showed as a dashed line.
  • the normal acceleration value 22 (absolute value) gives a range, wherein the normal acceleration occurs.
  • the system for detecting a hydrostatic lock is independent from the engine speed.
  • the hydrostatic lock can be selected to be determinated, for example, when the acceleration is 50-70% higher than the normal value. It has been noticed that on standard installations, depending from other boundary conditions (engine temperature for example), the engine can rotate faster or slower (with the same air pressure) but this is not be a problem for the inventive arrangement. When using the invention, no Fourier analysis is needed. So the invention provides a more simple and reliable to detect the hydrostatic lock.
  • the air pressure what is needed for rotating the crankshaft slowly, depends on the engine itself, like it's type, size and power. 18 bars are needed for example to medium size diesel engines.
  • the slow rotation means in this context a rotation speed that is below rotation speed required when the engine is running and combusting. Since the running speed varies also greatly due to a great number of different engines, the slow rotation means a speed in a range above zero rpm to about 70 rpm in most types of the reciprocating combustion engines.
  • FIG. 3 shows an example of a method according to the invention.
  • a starting event method is for a reciprocating combustion engine 1 that is equipped with a speed measurement arrangement 8, 9 and a control unit 7.
  • the control unit is in connection with the speed measurement arrangement.
  • the method comprises a step for receiving 31 speed measurement data of a crankshaft 6 of the engine.
  • the method further comprises steps for calculating 31 acceleration of the crankshaft 6 by using the received speed measurement data, delivering 33 compressed air into at least two cylinders 2 of the engine in order to rotate the crankshaft, detecting 34 accelerations of the crankshaft 6 as response to the calculating acceleration, and detecting a hydrostatic lock 35 in at least one cylinder 2 of the engine utilizing the detected accelerations.
  • the acceleration can be calculated from the speed measurement by calculating derivatives of the speed measurement data.
  • The can comprise substeps for comparing the calculated acceleration to normal acceleration level, detecting acceptable acceleration if the calculated acceleration is at the normal level or with in an acceptable deviation up to 49% outside the normal acceleration level and, detecting acceleration outside the acceptable deviation in order to detect the hydrostatic lock. These steps can be situated into the above said detection steps in a reasonable manner. So, detection of the hydrostatic lock can occur in this example when the calculated acceleration is at least 50% over the normal acceleration value 22.
  • the delivering of the compressed air is controlled by cylinder specific valves 15.
  • Figure 3 shows a way how the inventive method can be provided. It should be noted that this is not the only way, but more like an example. It is practical that the functions of receiving speed measurement and calculation acceleration are running when the compressed air is delivered into the cylinders, for example. But these three steps may be turned on simultaneously as well.
  • the water in the combustion chamber should be removed, for example by unscrewing the spark plugs or injectors and suck or drain the liquid from the combustion chamber/s. Extra work may also be required, such as flushing out corrupted operating fluids and replacing damaged gaskets.
  • the acceleration calculation unit 10 and the detector unit 19 can provide a single entity. It is evident from the above that the invention is not limited to the embodiments described in this text but can be implemented in many other different embodiments within the scope of the inventive idea.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Combined Controls Of Internal Combustion Engines (AREA)

Abstract

The aim of the invention is to detect the hydrostatic lock before in a more reliable way (1). The starting event system is equipped with a speed measurement arrangement (8, 9) and a control unit (7). The control unit has an acceleration calculation unit (10) to calculate acceleration of the crankshaft (6) by using the received speed measurement data. The system is further provided with an air compression device (11) and an air delivery arrangement (14, 15, 16) to deliver the compressed air into cylinders (2) of the engine in order to rotate the crankshaft slowly. The control unit (10) is further provided with a detector unit (19) that is in connection with the acceleration unit in order to detect a hydrostatic lock in at least one cylinder of the engine.

Description

METHOD AND SYSTEM FOR DETECTING A HYDROSTATIC
LOCK DURING THE ENGINE START
Field of technology
The present invention relates to starting event systems for a reciprocating combustion engine that has a control unit for controlling and monitoring different functions of the engine. Especially the invention relates to starting of reciprocating combustion engines.
Prior art
As known the reciprocating combustion engine contains cylinders wherein fuel is burned in order to move pistons in the cylinders. The cylinder and piston provide a chamber for burning the fuel. The pistons are connected to the crankshaft in order to rotate it. The cylinder/s of the engine may contain undesired liquid like water or oil due to challenging environmental conditions (for example through intake air) or leakage in the engine.
The undesired liquid may cause a state that is called hydrostatic lock. The hydrostatic lock occurs when a volume of liquid greater than the volume of the cylinder at its minimum, like the chamber's volume at the end of the piston's stroke, enters the cylinder. Since most common liquids are incompressible, the piston cannot complete its travel due an increase in cylinder pressure well above ordinary operating pressures. This means that either the engine must stop rotating or a mechanical failure occurs.
If the hydrostatic lock occurs, a mechanical failure is likely. Common damages can be bent or broken connecting rods, a fractured head, a fractured block, crankcase damage, damaged bearings, or any combination of these. Damages usually require replacement of the engine or a substantial rebuild of its major components. If an internal combustion engine runs under low power, the engine may stop suddenly with no immediate damage.
Short description of invention The aim of the invention is to detect the hydrostatic lock before any damage occurs in the engine. The invention detects if there is the hydrostatic lock, and a normal system doesn't see the hydrolock. In the solution according to the invention, a starting event system for a reciprocating combustion engine is equipped with a speed measurement arrangement and a control unit. The control is in connection with the speed measurement arrangement to receive speed measurement data of a crankshaft of the engine. The control unit has an acceleration calculation unit to calculate acceleration of the crankshaft by using the received speed measurement data, and the starting event system is further provided with an air compression device and an air delivery arrangement to deliver the compressed air into cylinders of the engine in order to rotate the crankshaft slowly. The control unit is further provided with an detector unit that is in connection with the acceleration unit in order to detect accelerations of the crankshaft. The detector unit is further arranged to detect a hydrostatic lock in at least one cylinder of the engine utilizing the detected accelerations.
List of figures
In the following, the invention is described in more detail by reference to the enclosed drawings, where
Figure 1 illustrates an example of a starting event system for a reciprocating combustion engine according to the invention, Figure 2 illustrates a schematic diagram of acceleration of the crankshaft and Figure 3 illustrates a flow diagram example of a method according to the invention
Description of the invention
Figure 1 illustrates an example of an embodiment of the invention. A starting event system for a reciprocating combustion engine 1 is equipped with a speed measurement arrangement that can, for example, be a speed sensor 8 and formations or marks on the edge of the flywheel 9. The flywheel is in connection with the crankshaft 6 of the engine. The starting event system is also provided with a control unit 7 that is in connection with the speed measurement arrangement 8, 9 to receive speed measurement data of the crankshaft. The control unit 7 has an acceleration calculation unit 10 to calculate acceleration of the crankshaft by using the received speed measurement data.
The starting event system is further provided with an air compression device 1 1 that comprises of an air compressor 12 and a tank 13 for the compressed air. There is also an air delivery arrangement 14, 15, 16 to deliver the compressed air into cylinders 2 of the engine in order to rotate the crankshaft 6 slowly. Other embodiments for the air compression device and the air delivery arrangement are possible. The tank can, for example, be connected to several engines for delivering the compressed air to them. The use of the compressed air is practical since it suits for retrofit installation for existing engines, and it also suits as equipment for new engines. Since other gases can also be used instead of air, the air compression device and the air deliver arrangement mean in this context to be suitable for other suitable gases as well. Therefore the compressed air means any compressed gas in this context as well. The control unit has a detector unit 19 that is in connection with the acceleration calculation unit 10 in order to detect accelerations of the crankshaft. The detector unit 19 is further arranged to detect a hydrostatic lock in at least one cylinder of the engine utilizing the detected accelerations.
As can be seen in the figure the cylinder 2 and a piston 3 provide a combustion chamber 4 in the cylinder for burning fuel which causes movement of the piston 3. The piston is in connection with the crankshaft in order to rotate it. The compressed air can, for example, be transferred into combustion chamber 4 through an inlet 16 in a cylinder head 5.
The idea is that if there's a hydrostatic lock inside the combustion chamber, the acceleration of the crankshaft is noticeable. Actually, the crankshaft may even stop to move at a certain point just because the inertia force of the system is bigger than the force given by the compressed air. It is more likely that the hydrostatic lock occurs when the volume of the combustion chamber is at it's minimum volume 17. So, acceleration of the crankshaft means slowing down and speeding up in this context. The compressed air is used to rotate the crankshaft during starting of the reciprocating combustion engine 1. It is difficult to control the compressed air system in order to make the crankshaft accelerate smoothly due to inertia of the system. When rotating the crankshaft in slow speed with only a few rpm (revolutions per minute), there exists a pendulum effect: once the piston goes to the TDC (Top Dead Centre), the piston accumulates energy, and after going over the TDC the piston starts to rotate the crankshaft on the other side. The pendulum effect can be quite difficult to notice. For avoiding this effect the only possibility is to have higher pressure for the system which means to have higher rpm. This causes other problems. In the invention, acceleration is used instead of speed analysing for detecting the hydrostatic lock. With this innovation, there is no need to increase the speed, pendulum effect is not a problem as long as you can understand it is something 'natural' and no caused by an hydrostatic lock. Acceleration analysis gives this kind of indication.
The acceleration can be calculated from the speed measurement by calculating derivatives of the speed measurement data. The calculation of the derivatives may, for example, be obtained by a simple embodiment of calculating Δν/Δί wherein v is speed and t is time. The detector unit 19 comprises a normal acceleration value, and the detection of the hydrostatic lock occurs when the calculated acceleration is above the normal acceleration value. The calculation is made in the acceleration calculation unit 10. As said the detector unit 19 that is in connection with the acceleration calculation unit 10 comprises a normal acceleration value, which is a normal acceleration of the crankshaft, mostly due to the said pendulum effect. The normal acceleration is a predetermined acceleration, representing normal starting event of the reciprocating combustion engine without a hydrostatic lock. It can be obtained, for example, by testing, and being for example an average acceleration of pendulum effect. The predetermined acceleration is saved in order to compare the predetermined acceleration to the calculated acceleration.
The detection of the hydrostatic lock occurs when the calculated acceleration is above the normal acceleration value. For example, the detection of the hydrostatic lock may occur when the calculated acceleration is at least 50% over the normal acceleration value. If the acceleration remains within a certain limit, i.e. it is normal acceleration; it can be presumed that the engine doesn't have any hydraulic lock. Other possible ranges are, for example at least 40% and at least 60%.
For rotating the crankshaft slowly the compressed air is delivered inside the cylinders. The air delivery arrangement comprises a distribution piping 14 for connecting the air compression device 1 1 to at least two of the cylinders. At least two cylinders are needed to rotate the crankshaft in four stroke engines. The distribution piping comprises cylinder specific valves 15 for controlling admission of the compressed air into the respective cylinder.
There are different ways to control the valves 15. For example, the control unit 7 can be connected to the valves 15 for controlling operation of the valves, and the engine 1 comprises an absolute rotary encoder 18 that is connected with the control unit. The absolute rotary encoder is a device that can determine the crank angle of the engine even when the engine is at rest. As illustrated in Figure 1 , the absolute rotary encoder can be connected to the crankshaft. Having reference to WO 2012035199, this publication discloses the air delivery arrangement and it's control arrangement in a more detailed manner than Figure 1. Another possible embodiment is to use a specific cam on the crankshaft for indicating the crank angle and moments to open the each valve 15. Further, the crank angle information may also be obtained from a camshaft of the engine. Figure 2 shows a schematic view of a normal acceleration 20 of the cranksaft and acceleration 21 of the crankshaft if the hydrostatic lock occurs in at least one cylinder of the reciprocating combustion engine. As can be seen, the difference between the acceleration values obtained when the hydraulic lock was present and when the hydraulic lock was not present, can be detected clearly. Tests can be made in order to find an engine specific or engine type specific normal acceleration value (or ranges for normal acceleration). The normal acceleration is showed as a solid line, and the acceleration due to the hydrostatic lock is showed as a dashed line. The normal acceleration value 22 (absolute value) gives a range, wherein the normal acceleration occurs.
Because the acceleration of the engine is monitored, the system for detecting a hydrostatic lock is independent from the engine speed. The hydrostatic lock can be selected to be determinated, for example, when the acceleration is 50-70% higher than the normal value. It has been noticed that on standard installations, depending from other boundary conditions (engine temperature for example), the engine can rotate faster or slower (with the same air pressure) but this is not be a problem for the inventive arrangement. When using the invention, no Fourier analysis is needed. So the invention provides a more simple and reliable to detect the hydrostatic lock.
The air pressure, what is needed for rotating the crankshaft slowly, depends on the engine itself, like it's type, size and power. 18 bars are needed for example to medium size diesel engines. The slow rotation means in this context a rotation speed that is below rotation speed required when the engine is running and combusting. Since the running speed varies also greatly due to a great number of different engines, the slow rotation means a speed in a range above zero rpm to about 70 rpm in most types of the reciprocating combustion engines.
Figure 3 shows an example of a method according to the invention. A starting event method is for a reciprocating combustion engine 1 that is equipped with a speed measurement arrangement 8, 9 and a control unit 7. The control unit is in connection with the speed measurement arrangement. The method comprises a step for receiving 31 speed measurement data of a crankshaft 6 of the engine. The method further comprises steps for calculating 31 acceleration of the crankshaft 6 by using the received speed measurement data, delivering 33 compressed air into at least two cylinders 2 of the engine in order to rotate the crankshaft, detecting 34 accelerations of the crankshaft 6 as response to the calculating acceleration, and detecting a hydrostatic lock 35 in at least one cylinder 2 of the engine utilizing the detected accelerations.
The acceleration can be calculated from the speed measurement by calculating derivatives of the speed measurement data. The can comprise substeps for comparing the calculated acceleration to normal acceleration level, detecting acceptable acceleration if the calculated acceleration is at the normal level or with in an acceptable deviation up to 49% outside the normal acceleration level and, detecting acceleration outside the acceptable deviation in order to detect the hydrostatic lock. These steps can be situated into the above said detection steps in a reasonable manner. So, detection of the hydrostatic lock can occur in this example when the calculated acceleration is at least 50% over the normal acceleration value 22. The delivering of the compressed air is controlled by cylinder specific valves 15.
Figure 3 shows a way how the inventive method can be provided. It should be noted that this is not the only way, but more like an example. It is practical that the functions of receiving speed measurement and calculation acceleration are running when the compressed air is delivered into the cylinders, for example. But these three steps may be turned on simultaneously as well.
When the hydrostatic lock has been detected, the water in the combustion chamber should be removed, for example by unscrewing the spark plugs or injectors and suck or drain the liquid from the combustion chamber/s. Extra work may also be required, such as flushing out corrupted operating fluids and replacing damaged gaskets.
There are also other ways to obtain the inventive embodiment as illustrated above. For example, the acceleration calculation unit 10 and the detector unit 19 can provide a single entity. It is evident from the above that the invention is not limited to the embodiments described in this text but can be implemented in many other different embodiments within the scope of the inventive idea.

Claims

Claims
1. A starting event method for a reciprocating combustion engine (1 ) that is equipped with a speed measurement arrangement (8, 9) and a control unit (7), the control unit being in connection with the speed measurement arrangement, the method comprising a step for receiving (31 ) speed measurement data of a crankshaft (6) of the engine, characterised in that the method further comprises steps for calculating (32) acceleration of the crankshaft (6) by using the received speed measurement data,
delivering (33) compressed air into at least two cylinders (2) of the engine in order to rotate the crankshaft,
detecting (34) accelerations of the crankshaft (6) as response to the calculating acceleration, and
detecting a hydrostatic lock (35) in at least one cylinder (2) of the engine utilizing the detected accelerations.
2. A starting event method according to Claim 1 , characterised in that the acceleration is calculated from the speed measurement by calculating derivatives of the speed measurement data.
3. A starting event method according to Claim 1 or 2, characterised in that the it comprises substeps for
comparing the calculated acceleration to normal acceleration level,
detecting acceptable acceleration if the calculated acceleration is at the normal level or with in an acceptable deviation up to 49% outside the normal acceleration level and,
detecting acceleration outside the acceptable deviation in order to detect the hydrostatic lock.
4. A starting event method according to Claim 3, characterised in that the detection of the hydrostatic lock occurs when the calculated acceleration is at least 50% over the normal acceleration value (22).
5. A starting event method according to Claim 4, characterised in the delivering of the compressed air is controlled by cylinder specific valves (15).
6. A starting event system for a reciprocating combustion engine (1 ), the system comprising a speed measurement arrangement (8, 9) and a control unit (7), the control being in connection with the speed measurement arrangement to receive speed measurement data of a crankshaft (6) of the engine, characterised in that the control unit (7) has an acceleration calculation unit (10) to calculate acceleration of the crankshaft (6) by using the received speed measurement data, and the starting event system is further provided with an air compression device (11 ) and an air delivery arrangement (14, 15, 16) to deliver the compressed air into at least two cylinders (2) of the engine in order to rotate the crankshaft, the control unit (7) being further provided with an detector unit (19) that is in connection with the acceleration unit (10) in order to detect accelerations of the crankshaft (6), the detector unit being further arranged to detect a hydrostatic lock in at least one cylinder (2) of the engine utilizing the detected accelerations.
7. A starting event system according to Claim 6, characterised in that the acceleration is calculated from the speed measurement by calculating derivatives of the speed measurement data.
8. A starting event system according to Claim 7, characterised in that the detection of the hydrostatic lock occurs when the calculated acceleration is at least 50% over the normal acceleration value (22).
9. A starting event system according to Claim 4, characterised in the air delivery arrangement comprises a distribution piping (14) for connecting the air compression device (1 1 ) to at least two of the cylinders (2), and cylinder specific
valves (15) in the distribution piping for controlling admission of the compressed air into the respective cylinder.
10. A starting event system according to Claim 9, characterised in that the control unit (7) is connected to the valves (15) for controlling operation of the valves, and the engine comprises an absolute rotary encoder (18) that is connected with the control unit (7).
PCT/FI2015/050050 2014-03-07 2015-01-26 Method and system for detecting a hydrostatic lock during the engine start WO2015132453A1 (en)

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