WO2004076855A1

WO2004076855A1 - Pitch regulation system

Info

Publication number: WO2004076855A1
Application number: PCT/DK2004/000136
Authority: WO
Inventors: Tom Weiling; Flemming M. Christensen
Original assignee: Avn Hydraulik A/S
Priority date: 2003-02-27
Filing date: 2004-02-27
Publication date: 2004-09-10

Abstract

The present invention concerns a pitch regulation system for the blades (6) of a rotating propeller (1), including a hydraulic oil station (7) which is provided with a hydraulic oil tank (10), a hydraulic oil pump (8) and a control unit, one rotating propeller shaft (12) with a number of internal hydraulic oil ducts (13, 14), and a transition arrangement (9) interconnecting the hydraulic oil station (7) and the rotating propeller shaft (12), where the hydraulic station (7) is disposed in a stationary position at least under the rotating propeller shaft (12), that the transition arrangement (9) includes a number of connecting branches (15, 16) which connect the internal hydraulic oil ducts (13, 14) with the hydraulic oil pump (8) and/or the hydraulic oil tank (10), and that the transition arrangement (9) is disposed over the hydraulic oil tank (10).

Description

Pitch Regulation System

Scope of the Invention

The present invention concerns a pitch regulating system for the blades of a rotating propeller, including a hydraulic oil station which is provided with a hydraulic oil tank, a hydraulic oil pump and a control unit; one rotating propeller shaft with a number of internal hydraulic oil ducts; and a transition arrangement interconnecting the hydraulic oil station and the rotating propeller shaft.

Background of the Invention

When generating electric power, propellers are used that rotate by the action of either an air flow or a liquid flow. By the propulsion of vessels, propellers that rotate by the action of an engine are used.

Common to these are that it is possible to control the power from the propeller by turning the propeller blades relative to the air flow or liquid flow. The efficiency of the propellers depends on how large inclination these propeller blades have in relation to the air flow and/or the liquid flow and the force from the latter.

In order to optimise the achieved power, different pitch regulation systems have been produced which are adapted to turn the propeller blades so that they, irrespectively of the direction of and the force from the air flow or the liquid flow can be adjusted to an angle that results in optimal power.

Previously, pitch regulation systems were simple mechanical systems which by means of e.g. belt drive, gear wheels and similar were able to turn the propeller blades.

The disadvantage has been that it has been difficult to build up a system which mechanically can be integrated in a rotating propeller, since the propeller blades, which are mounted on a mill head/hub, rotate about another plane than the rotating movement of the main shaft extending through a nacelle. The simple mechanical systems have been substituted by either pneumatic pitch regulation systems or hydraulic pitch regulation systems, where instead of a mechanical connection to each propeller blade, an actuator is provided at each propeller blade. By supplying compressed air or hydraulic oil to the propeller blade actuators, will be pos- sible to turn the propeller blades.

A drawback of pneumatic/hydraulic pitch regulation systems is that the compressed air/hydraulic oil is to be supplied from a hydraulic oil station and out to the actuators, e.g. from the nacelle via the main shaft to the mill head/hub and the actuators of the propeller blades.

In order to avoid this, a hydraulic oil station has been provided in the mill head/hub, providing the propeller blade actuators with hydraulic oil, or there is provided a number of hydraulic oil stations in the mill head/hub that each supply hydraulic oil to one of the actuators of the propeller blades.

A drawback of this feature is that these hydraulic stations are built up so that they rotate with the mill head/hub, implying some production and operation problems, as e.g. the hydraulic station is typically provided with a hydraulic oil tank which is hermeti- cally sealed, so that the hydraulic oil will remain in the hydraulic oil tank irrespectively of the orientation of the hydraulic tank.

Furthermore, the hydraulic oil tank is to be designed so that the hydraulic oil pump has access to hydraulic oil all the time, without any leakage occurring anywhere, or air bubbles appearing in the hydraulic oil forwarded to the propeller blade actuators.

An alternative may be to place a hydraulic oil station within the nacelle of the mill, whereby hydraulic oil is supplied to the actuators in the mill head/hub via ducts in the main shaft. This entails that a transition arrangement is to be provided between the hydraulic oil station and the main shaft, allowing continual flow of hydraulic oil when the main shaft is rotating. The above solution has the drawback that it is difficult to make the transition arrangement 100% tight, entailing that when the main shaft is rotating and the propeller blades are pitch regulated, leakage of hydraulic oil in the transition arrangement occurs.

This result in frequent service intervals, where new hydraulic oil is to be filled on the hydraulic oil station, implying use of manpower and time to fill hydraulic oil on the hydraulic station, and the area around the transition arrangement is to be cleaned from hydraulic oil, implying manpower and time to be used for cleaning.

In UK patent application GB A 1 071 779 is described a pitch regulation system where a hydraulic station including control unit is disposed in the mill nacelle. The main shaft is designed with internal ducts for supply and return of hydraulic oil to the actuators of the propeller blades and returning electric signals from the mill head/hub to the control unit.

Transfer of hydraulic oil from the hydraulic oil station to the main shaft occurs via a bearing surrounding the main shaft, where the bearing furthermore is provided with connecting branches for the hydraulic station and with internal annular recesses that allow hydraulic oil to pass from the connecting branches to internal ducts when the main shaft rotates.

The described pitch regulation system in GB A 2 071 779 has the drawback that it is difficult to keep tight the bearing surrounding the main shaft due to e.g. changing temperatures during operation, the pump pressure of the hydraulic oil and wear on sealings/packings, resulting in increased hydraulic oil consumption and increased cleaning of the mill nacelle.

Object of the Invention Therefore, it is the purpose of the present invention to indicate a pitch regulation system with permanently mounted hydraulic oil station in the mill head/hub, which in a secure, easy and simple way regulates the supply and return flows of the hydraulic oil in connection with regulating the propeller blades on a rotating propeller simultaneously with leakage/waste of hydraulic oil being substantially reduced.

This is achieved by a pitch regulation system of the kind mentioned in the introduction as specified in the characterising part of claim 1, and where the hydraulic station is disposed in a stationary position at least under the rotating propeller shaft, that the transition arrangement includes a number of connecting branches which connect the internal hydraulic oil ducts with the hydraulic oil pump and/or the hydraulic oil tank, and that the transition arrangement is disposed over the hydraulic oil tank.

Description of the Invention

It is a constructional advantage that the hydraulic station in the mill head/hub is disposed at a stationary position at least under the rotating propeller shaft, since the hydraulic oil station includes a hydraulic oil tank which will be placed under the propel- ler shaft and which thereby may collect hydraulic oil leaking from the transition arrangement.

The rotating propeller shaft is either an integrated part of the main shaft of the mill or is connected to the main shaft of the mill and is turning around with it.

By placing the transition arrangement in the mill head/hub, the length required for piping in the transition arrangement and the propeller shaft and on to the actuators is reduced.

Internally in the propeller shaft, internal ducts for supplying and returning hydraulic oil for the propeller blade actuators, where the hydraulic oil pump of the hydraulic oil station is pumping hydraulic oil from the hydraulic oil tank via the transition arrangement into the supply ducts in the rotating propeller shaft.

The transition arrangement includes a number of connecting branches for the internal duct for supplying and returning hydraulic oil, so that the hydraulic oil pumped out to the actuators of the propeller blades is recirculated back to the hydraulic oil tank. The transition arrangement between the hydraulic oil station and the rotating propeller shaft is placed over the hydraulic oil tank, implying that possible leakages arising in the transition arrangement will be collected in the hydraulic oil tank.

This means that the leakage out in the mill head/hub is considerably reduced, whereby the frequency of the cleaning is significantly reduced, and at the same time the same amount of hydraulic oil is not to be used for operating the pitch regulation system.

The connecting branches are provided in connection with annular ducts in the transition arrangement, so that even if the propeller shaft rotates, it is possible that the hydraulic oil pump will press hydraulic oil to the actuators of the propeller blades.

In an embodiment of the present invention, the hydraulic oil station surrounds the ro- tating propeller shaft, and the transition arrangement is an integrated part of the hydraulic oil tank.

This means that the transition arrangement is built into the hydraulic oil tank, that the propeller shaft goes through the hydraulic oil tank, and that any leaks from the transi- tion arrangement will be caught in the hydraulic oil tank, whereby a compact unit and a more secure way of transferring hydraulic oil to the propeller blade actuators are achieved.

By placing the transition arrangement in close connection with the hydraulic oil pump it is not necessary with long piping between the hydraulic oil pump and the transition arrangement.

In an embodiment of the present invention, the hydraulic oil station includes an air filter which ensures possibility of pressure equalisation between the hydraulic oil tank and the surroundings.

The air filter is thus placed in connection with the transition arrangement, and via ducts it communicates through the transition arrangement and down to the hydraulic oil tank of the hydraulic oil station.

This means that it is impossible for the hydraulic oil pump either to form a vacuum or an overpressure in the hydraulic oil tank, so that it will be deformed and possibly leaks occurring as a result.

An unwanted leak will entail waste of hydraulic oil, whereby it will not be possible to maintain a sufficient level of hydraulic oil in the hydraulic oil tank for pitch regulation of the propeller blades.

In an embodiment of the present invention, the hydraulic oil station further includes a cooling and filtering circuit, ensuring uniform temperature of the hydraulic oil and clean hydraulic oil.

By circulation of the hydraulic oil under pressure, the temperature of the hydraulic oil will rise. Since the hydraulic oil has a certain temperature range within which the best properties appear, it is important that the temperature is kept constant. By means of the cooling circuit it is possible to keep a uniform temperature of the hydraulic oil, irre- spectively of rise in temperature due to circulation or to ambient temperature.

The filter in the cooling and filter circuit is used for filtering the hydraulic oil so that impurities will not be circulated around in the hydraulic oil system and cause wear, leaks or the like.

In an embodiment of the present invention, the transition arrangement is a rotating union. A rotating union is a coupling piece applicable at a transition between a fixed unit and a rotating unit. This rotating union is built up with a jacket which via bearings is mounted around the shaft, and with a number of sealings.

In order to make the production process easier, the rotating union is an integrated part of the rotating propeller shaft. This implies that during the making of the propeller shaft, the rotating unint is mounted on the right place, so that the internal ducts of the propeller shaft are connected with the connecting branches in the rotating union.

In an embodiment of the present inventon, the rotating union is constituted by two parts, where a first part includes a number of bearings, and a second part includes a number of sealings, where the first part furthermore connects the rotating union to the hydraulic oil tank.

The fact that the rotating union is composed of two parts implies that it is easy in a simple way to exchange sealings in the union without having to dismount the entire hydraulic oil station. Furthermore, it will be easier to (retro)fιt the rotating union on a propeller shaft when the two parts are assembled around the propeller shaft.

The rotating union is provided with drain so that collection of the hydraulic oil coming from the possible leakages appearing in the rotating unit at the connecting branches and the internal recesses may be provided. The drains have outlet via ducts down into the hydraulic oil tank of the hydraulic oil station, whereby leaking hydraulic oil is collected.

In order to ensure that the propeller blades are regulated so that the selected pitch angle is in accordance with the e.g. the direction of the air flow, the control unit of the hydraulic oil station controls pitch regulation of the propeller blades, and at the same time it communicates with a main control unit.

The main control unit may be the control unit for e.g. a generator and/or an engine, and it may be coupled to a direction measurement device. From the direction measurement device the main control unit can adjust the nacelle so that the mill head/hub always have a direction against the wind and transmit a signal for the control unit in the hydraulic oil station about a certain pitch angle of the propeller blades appropriate for this direction and air flow.

In arctic areas or desert areas, where the temperatures are either very low part of the year or very high in some periods, the hydraulic oil station is designed with a heating/cooling element which is controlled by a thermal control unit which is an integrated part of the control unit of the hydraulic oil station.

This means that e.g. in a desert area where it may be cold at night and hot in the daytime, the control unit of the hydraulic oil station may activate the cooling/heating element at night, so that the temperature of the hydraulic oil has a largely constant temperature providing that e.g. the viscosity of the hydraulic oil is held within predetermined limits regarded as optimal for this type of hydraulic oil and application situa- tion.

In arctic areas, it will typically be the heating element which is activated so that the hydraulic oil does not congeal under the extreme influence of extreme degrees below zero. Furthermore, heating of the hydraulic oil will contribute to the propeller shaft receiving some heating and thereby not freezing in the union, which can be particularly advantageous at calm or in other periods, where the propeller shaft is not moving.

In order to optimise the main control unit, the hydraulic oil station may furthermore include a control and monitoring unit for registering and controlling the rotational speed of the rotating propeller shaft.

Monitoring the rotational speed may e.g. be used for calculating which pitch angle is best for the propeller blades at certain wind directions and at certain wind speeds.

Controlling the rotational speed can be used as a control parameter e.g. for remote control of the propeller, either in control room or at another remotely situated place, where the rotational speed, via conversion formulas, may indicate the absorbed or yielded power.

Furthermore, a monitoring unit will provide that as soon as something abnormal occurs at or around the rotating propeller shaft, one may intervene from the control room, or service personnel may be sent out for checking and possibly repairing the propeller.

In a preferred embodiment of the invention, the hydraulic station is suspended in bearings. In order to ensure that the hydraulic oil station does not turn around with the propeller shaft, the hydraulic oil station is designed so that the larger part of its weight is disposed under the propeller shaft, e.g. by placing the hydraulic oil tank under the propeller shaft as a counterweight. Alternatively, the propeller shaft can be passed through the hydraulic oil tank, and a further weight is e.g. used as counterweight which prevents rotation of the hydraulic oil tank.

The pitch regulation system according to the present invention is applicable to all types of propellers, but in a preferred embodiment of the invention, the pitch regulation is designed so that it is used in connection with the pitch regulation of the wings of a windmill, and that the pitch regulation system is to be used for rotating the blades on a windmill so that the windmill absorbs the largest possible power from the wind.

The pitch regulation system may furthermore be used for stall-mills, where the wing- tips are to be provided with hydraulic pressure.

The pitch regulation system according to the invention may furthermore be used in other places like, for example: a propeller onboard a ship a propeller in a fan a propeller in a mixing unit - a propeller on an airplane a propeller in a turbine

Short Description of the Drawing

In the following, the invention is described with reference to the Figures which, with- out being limiting, show preferred embodiments of a pitch regulation system according of the invention, where: Fig. 1 shows a windmill with pitch regulated wings;

Fig. 2 shows a side view of a hydraulic oil station according to the invention;

Fig. 3 shows a sectional view of the hydraulic oil station; and

Fig. 4 shows a side view of an alternative hydraulic oil station according to the in- vention.

On the Figures, the reference numbers designate the following:

1 propeller

2 mill

3 tower

4 nacelle

5 mill head/hub

6 propeller blades

7 hydraulic oil station

8 hydraulic oil pump motor

9 union

10 hydraulic oil tank

11 air filter

12 propeller shaft

13 return duct

14 supply duct

15 connecting branch

16 connecting branch

17 drain

18 drain

19 filling inlet

20 hydraulic oil station

21 hydraulic oil motor

22 hydraulic oil tank

23 two-part union

24 propeller shaft Detailed Description of the Invention

Fig. 1 shows a propeller 1 mounted on a mill 2, where a nacelle 4 is disposed rotatably on a tower 3 where in connection with the nacelle 4 there is a mill head 5 on which the rotating propeller blades 6 are mounted. The propeller blades 6 are mounted so that they by means of the pitch regulating system may e.g. rotate in the direction A.

On Fig. 2 is seen a hydraulic oil station 7 which includes a hydraulic oil pump motor 8 that is mounted in connection with a hydraulic oil tank 10, and where a hydraulic oil pump (not shown) is placed inside in hydraulic oil tank 10. The hydraulic oil station 7 is disposed under a propeller shaft 12. A union 9 connects the hydraulic oil station 7 with the propeller shaft 12. Upon the union 9 is placed an air filter 11. The propeller shaft 12 is in actual continuation of the main shaft (not shown) of the windmill (not shown).

Fig. 3 shows a cross-section of the hydraulic oil station 7, where the hydraulic oil station 7 is mounted under and in comiection with the union 9 which is mounted on the propeller shaft 12. Inside the propeller shaft 12 there is provided a supply duct 14 and a return duct 13. These ducts 13 and 14 are connected to a hydraulic oil tank 10 by means of a connecting branch 15, which is connected to the return duct 13, and a con- necting branch 16, which is connected to the supply duct 14. In order to absorb possible leaks inside the union 9, drains 17 and 18 are provided in connection with the return duct 13 and supply duct 14, draining the union 9 for possible hydraulic oil down into the hydraulic oil tank 10. In connection with the union 9 there is placed an oil filter 11 which is mounted in the top of the union 9 with a packing (not shown), so that via a drain 17 there is possibility of pressure equalisation of the hydraulic oil tank 10.

This means that the hydraulic oil pump (not shown) cannot inadvertently form a vacuum inside the hydraulic oil tank 10, so that it is deformed and leakage occurs. At the side of the hydraulic oil tank 10 there is an inlet 19 which can be used for filling hydraulic oil.

Fig. 4 shows a hydraulic oil station 20 designed with a hydraulic oil motor 21 which is disposed across part of the hydraulic oil tank 22. A two-part union 23 connects the propeller shaft 24 with the hydraulic oil station 20. It is to be noted that shape and size of the hydraulic oil tank 22 and disposition of the hydraulic oil motor 21 and the air filter (not shown) may be adapted according to the need of the individual user so that it is possible to build the hydraulic oil station 20 into different places.

Claims

1. Pitch regulation system for the blades (6) of a rotating propeller (1), including a hydraulic oil station (7) which is provided with a hydraulic oil tank (10), a hydraulic oil pump (8) and a control unit; one rotating propeller shaft (12) with a number of internal hydraulic oil ducts (13, 14); and a transition arrangement (9) interconnecting the hydraulic oil station (7) and the rotating propeller shaft (12); characterized in that the hydraulic station (7) is disposed in a stationary position at least under the rotating propeller shaft (12), that the transition arrangement (9) includes a number of connect- ing branches (15, 16) which connect the internal hydraulic oil ducts (13, 14) with the hydraulic oil pump (8) and/or the hydraulic oil tank (10), and that the transition arrangement (9) is disposed over the hydraulic oil tank (10).

2. Pitch regulation system according to claim 1, characterized in that the hydraulic oil station (7) surrounds the rotating propeller shaft (12), and that the transition arrangement (7) is an integrated part of the hydraulic oil tank (10).

3. Pitch regulation system according to claims 1 - 2, characterized in that the hydraulic oil station (7) furthermore includes an air filter (11).

4. Pitch regulation system according to claim 1, characterized in that the hydraulic oil station (7) furthermore includes a cooling and filtering circuit.

5. Pitch regulation system according to claims 1 - 2, characterized in that the transi- tion arrangement is a rotating union (9).

6. Pitch regulation system according to claim 5, characterized in that the rotating union (9) is an integrated part of the rotating propeller shaft (12).

7. Pitch regulation system according to claims 5 - 6, characterized in that the rotating union (24) is constituted by two parts, of which the first part includes a number of bearings and a second part includes a number of sealings.

8. Pitch regulation system according to claims 5 - 7, characterized in that the rotating union (9) is provide with drain (17, 18).

9. Pitch regulation system according to claim 1, characterized in that the control unit of the hydraulic oil station (7) controls pitch regulation of the propeller blades (6) and simultaneously communicate with a main control unit.

10. Pitch regulation system according to claim 1, characterized in that the hydraulic oil station (7) furthermore includes a heating/cooling element which is controlled by a thermal control integrated in the control of the hydraulic oil station.

11. Pitch regulation system according to claim 1, characterized in that the hydraulic oil station (7) furthermore includes a control and monitoring unit for registering and controlling the rotational speed of the rotating propeller shaft (12).

12. Pitch regulation system according to any of the above claims, characterized in that it is used in connection with pitch regulation of the wings (6) of a windmill (2).