GB2461057A

GB2461057A - Ram air turbine

Info

Publication number: GB2461057A
Application number: GB0811181A
Authority: GB
Inventors: Werner Schiffers; David Reginald Trainer; Mark David Taylor
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2008-06-19
Filing date: 2008-06-19
Publication date: 2009-12-23
Also published as: GB0811181D0

Abstract

A ram air turbine for a vehicle comprises a turbine 2 mounted within a compartment 3 to the side of a fluid stream 5 in use, the turbine 2 being selectively deployable from the compartment 3 and into the fluid stream to provide drag and/or electrical power through an electrical machine associated with the turbine 2. The compartment may have a door 6 which is displaced when the turbine 2 is deployed. The vehicle may be an aircraft and the turbine 2 may be deployed during a period of descent or deceleration of the aircraft. The ram air turbine may directly power electrical systems of the vehicle, possibly by pulse activation. Alternatively the power generated may be stored electrically (batteries), mechanically or pneumatically (compressed gas). The ram air turbine may provide a power supply distinct in terms of current, voltage or frequency from other power supply systems in the vehicle. The turbine 2 may have variable pitch blades 8, and the angle of the turbine 2 in the fluid flow may be adjustable. The vehicle could also be ship, the ram air turbine being used to assist steering or braking as well as electrical power generation.

Description

RAM AIR TURBINES

The present invention relates to ram air turbines and more particularly to ram air turbines utilised in vehicles such as aircraft and methods of operating such ram air turbines.

It is known to use ram air turbines (RAT) within such vehicles as aircraft and in particular commercial and military aircraft. The ram air turbines provide electrical power in emergency conditions such as when or if the main engine or engines fail. As will be appreciated the main component of a ram air turbine is a turbine which is connected to a generator which creates electrical power.

During flight the ram air turbine is stowed in a compartment within the fuselage of an aircraft or other vehicle. This compartment is aerodynamically configured such that it is recessed to create limited drag. Ira such circumstances the compartment is to one side of an air flow passing over a body or fuselage of the aircraft or other vehicle. When required, that is to say when emergency power is required, a door in the compartment opens and the ram air turbine swings out into the air stream or air flow passing over the fuselage.

The high speed of the air flow drives the turbine which then powers a generator to provide electrical power to electrical systems within the vehicle. In such circumstances critical machinery can still remain operational should the main engines of the vehicle fail.

Such critical machinery includes hydraulic systems, flight controls, flight critical instrumentation and avionic systems. The amount of electrical power generated will depend upon requirements, the size of the ram air turbine and other factors.

Ram air turbines in the above circumstances are provided for emergency use. The remainder of the time the ram air turbine is non-functional and as indicated above stowed away. In such circumstances ram air turbines particularly with regard to aircraft add significantly to weight and are not fully utilised.

In accordance with aspects of the present invention there is provided a ram air turbine for a vehicle comprising a turbine upon a mounting within a vehicle compartment aerodynamically recessed to one side of a fluid stream in use, the turbine upon the mounting in use selectively displaceable into the fluid stream from the compartment to provide a drag variation and/or electrical power condition variation through an electrical machine associated with the turbine.

Also in accordance with aspects of the present invention there is provided a method of operating a ram air turbine within a moving vehicle whereby the ram air turbine generates or uses electrical power, the method comprising providing the ram air turbine upon a mounting within an aerodynamically recessed compartment to one side of the fluid stream, the ram air turbine electively deployable upon the mounting into the fluid stream from the compartment and the ram air turbine used to provide a drag variation and/or adjust electrical power conditions in the vehicle.

Typically, the vehicle is an aircraft.

Generally, the compartment has a door displaceable when the turbine is deployed.

Generally, the turbine is deployed when an associated vehicle enters a descent or deceleration phase.

Generally, the electrical power from the turbine is used directly to power an electrical power system in the vehicle.

Possibly, the electrical power generated from the ram air turbine is used selectively to provide power for pulse activation of electrical systems in the vehicle.

Possibly the storage means comprises electrical, mechanical, pneumatic or other storage means.

Possibly, the electrical power is stored in a storage means. Possibly, the storage means comprises a battery or a compressed gas vessel.

Typically, the turbine is used to provide a distinct electrical power supply from other electrical power supply systems in the vehicle.

Possibly, the electrical power generated by the ram air turbine is distinct in terms of current, voltage or frequency from other electrical power supply systems in the vehicle.

Possibly, the ram air turbine has a blade assembly and the blade assembly incorporates variable pitched blades to adjust the drag variation.

Possibly, the mounting is configured to present the turbine variably in the air stream. Possibly the mounting varies the presentation of the turbine in the air stream in terms of angle.

Aspects of the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic cross section of a ram air turbine in a stowed state; Figure 2 is a schematic illustration of a ram air turbine in a deployed state; Figure 3 is a schematic illustration of utilisation of an air turbine in accordance with aspects of the present invention; and, Figure 4 is a schematic illustration of a system for utilisation of a ram air turbine in addition to existing turbines for electrical power generation within a vehicle such as an aircraft.

Figure 1 provides a schematic illustration of a ram air turbine arrangement 1 in which a ram air turbine 2 is located within a compartment 3 formed in a vehicle body structure or fuselage 4. The compartment 3 is provided to one side of an air stream 5 such that it is effectively aerodynamically recessed with regard to other parts of the body or fuselage 4 for appropriate aerodynamic profiling within a vehicle such as an aircraft. Aspects of the present invention will be described particularly with regard to aircraft but it will be understood that other vehicles such as ships may also incorporate ram air turbines for use with respect to electrical power generation conditions as well as drag with regard to the vehicle when required, Figure 2 provides a schematic cross section of the arrangement 1 depicted in Figure 1 in a deployed state. In such circumstances a door 6 has been opened and through a mounting 7 the turbine 2 deployed into the air stream 5.

In such circumstances the turbine 2 and in particular the blades 8 of the turbine 2 will rotate in the air stream 5.

Such rotation provides power to an electrical machine configured to act as electrical power generator. The electrical machine is not illustrated in figure 2 but is coupled through appropriate couplings and cable to an electrical power distribution system within a vehicle. It will be understood for accommodation purposes the blades 8 may fold within the compartment 2 and be urged outwardly by an appropriate spring bias into a deployed state as depicted in figure 2.

As described above generally such deployment of ram air turbines with respect to prior arrangements has been for emergency generation of electrical power. In accordance with aspects of the present invention ram air turbines are utilised in non-emergency conditions and selectively to increase their utility and acceptability with regard to vehicles such as aircraft. It will be appreciated particularly with regard to aircraft every time the aircraft starts to descend there is a requirement for significant electrical power to stimulate electrical systems whilst increasing drag upon the aircraft to slow the aircraft would be beneficial.

In such circumstances during a descent phase or approach phase that is to say when an aircraft is preparing to land, the aircraft speed needs to be reduced and therefore the ram air turbine may provide for drag variation in such circumstances.

In accordance with aspects of the present invention the turbine is deployed when an increase in drag for the vehicle is required. Such drag will contribute to a speed reduction with regard to the aircraft during flight which may be beneficial with regard to reducing the necessary fuel required for reverse thrust or friction braking. In such circumstances the door 6 will be selectively opened to deploy the ram air turbine 2 when required. In such circumstances when the ram air turbine 2 is deployed the air stream 5 will function upon the blades 8 and extract energy from the air flow over the blades 8. Such wind milling and extraction from the air stream passing over the vehicle will turn the turbine 2 and allow an electrical power generator switched to a motor associated with the ram air turbine 2 to provide a drag variation as well as the potential for electrical power generation.

It will be understood that the electrical power in particular generated from the ram air turbine 2 can be utilised in a number of ways. Figure 3 provides a schematic illustration of such processes. Thus, a ram air turbine 12 is associated with an electrical machine 13 which in turn is controlled by device 14 and generally converters 15 for the respective electrical systems within a vehicle such as an alternating current electrical system 16, a direct electrical current system 17, electrical energy storage 18 and/or direct temporary electrical load supply 19. It will be appreciated that within a vehicle such as an aircraft a number of electrical systems will generally be provided and in such circumstances various electrical machines in the form of electrical generators and/or motors will be utilised to meet these requirements.

Thus, conversion by a converter 15 is typical to meet the varying requirements of each system 16 to 19.

The electrical machine 13 may be a generator which is of a synchronous type, an induction type or permanent magnet machine or switched reluctance electrical machine.

Each system has their own particular requirements in terms of actuation control or electrical power conversion and the appropriate arrangement for particular systems 16 to 19 will be chosen as required. Similarly, with respect to frequency, whether that be variable or constant or direct electrical current, the electrical power considerations will be provided through specific or general controller 14 or conversion systems within a vehicle such as an aircraft.

In the above circumstances it will be appreciated that the electrical power provided by the ram air turbine can be utilised in a number of ways.

The electrical power provided by the ram air turbine can be used immediately to supplement an electrical power bus whether that be alternating current or direct current and so reduce the requirements from the main electrical power generating systems. These main electrical power generating systems will typically utilise gas turbine engines or other engines within the vehicle. Thus by reducing the power generation requirements for these engines it will be understood that less fuel burn will be required and also the load upon the normal generator may be reduced possibly extending its operational life and efficiency characteristics. Furthermore, in some circumstances a smaller main engine may be specified.

Alternatively, the electrical power generated through the electrical machine associated with the ram air turbine could be utilised with respect to peak power requirements in the vehicle. Thus, with respect to an aircraft during a descent phase when the main engines are not required to provide so much thrust but electrical power requirements may be significant utilisation of a ram air turbine in accordance with aspects of the present invention may allow closer matching with the electrical power demand without necessitating use of the main engines to meet that demand.

This reduction in required generating capacity from the main generator may improve efficiency. It will also be understood that operation of some systems such as hydraulics for deployment of landing gear will generally be of a pulse type such that the electrical power provided through the ram air turbine will enable such peaks in electrical power demand to be more easily met.

A third possibility is to take electrical power generated by the ram air turbine and associated electrical machine and store that electrical power. Clearly, storage of electrical power can have significant problems in that electrical batteries tend to be quite heavy but such batteries can be provided particularly with regard to land vehicles such as ships. Nevertheless, where appropriate electrical power storage means can be provided it will be understood that electrical power may be utilised in taxiing procedures with regard to aircraft or to enable electrical power to be provided to start the main engines as required.

One possible mechanism for storing electrical power is to pressurise a gas within a vessel utilising an appropriate pump and then when required that pressurised fluid such as compressed air is utilised to drive in a reverse direction the pump which in turn will then turn an electrical machine for electrical power generation. Clearly such an approach is not exceptionally efficient but nevertheless will allow some electrical power to be stored. A further alternative for power storage may be through a fly wheel.

With regard to some vehicles it will be appreciated that generally compromises must be made with respect to the electrical power systems. In such circumstances a standard electrical power supply system will be specified in terms of a common electrical power bus from which electrical power will be drawn but with converters as required. By provision of a ram air turbine in accordance with aspects of the present invention it will be appreciated that a dedicated electrical power bus different or distinct from the common electrical power supply system may be provided.

In such circumstances the dedicated electrical power bus may have a different voltage and/or frequency range which can be utilised appropriately with regard to electrical systems within the vehicle. In such circumstances it is possible to provide a "dirty" power bus with high harmonic pollution in comparison with the highly regulated common electrical power bus for short term usage and in relation to electrical actuator systems which do not require such high quality electrical systems for sensors etc. This will enable some simplification of electrical loads and their filtering and therefore offers weight and size benefits with respect to an air frame in aircraft etc. A further alternative utilisation of a ram air turbine in accordance with aspects of the present invention is to alter the turbine from a generator of electrical power to a consumable electrical power. In such circumstances the turbine will enter a motoring mode in order to extract electrical power from a power bus and therefore behave as a controlled load or regulator for the electrical power system within the vehicle. In such circumstances it may be possible to provide a dynamic breaking load to control system voltage and frequency shifts under transient conditions. Furthermore, instead of providing a passive drag through the energy taken to drive the turbine and therefore electrical motor for electrical generation it may be possible particularly in ground movements for the turbine to be driven and behave as a motor. A further example would be with regard to dissipation of regenerated power from other motor drive both during braking.

For illustration purposes figure 4 shows provision of an electrical power distribution system in a vehicle such as an aircraft. Thus, an electrical power bus 41 is associated with a number of electrical power generators or usage sources. The electrical power sources are provided through an auxiliary power unit 42, a high pressure turbine 43, an intermediate pressure turbine 44, a low pressure turbine 45 and a ram air turbine 46 in accordance with aspects of the present invention. Each of the sources 42 to 46 is associated through a generator and an appropriate alternating AC/DC current converter to provide electrical power to the common bus 41. Power in such circumstances is extracted from an engine with respect to the sources 43 to in relation to turbines and also with regard to an auxiliary power unit when the main engine is inoperative as well as a ram air turbine 46 in accordance with aspects of the present invention. The generators 42 to 46 in such circumstances meet the requirement of loads 47 during all phases of operation. It will be appreciated that a ram air turbine 46 is generally not used during normal flight conditions and as indicated previously acts as an emergency electrical power supply which can be rapidly deployed to maintain operation of particularly safety critical systems.

It will be understood that by addition of a ram air turbine Ira accordance with aspects of the present invention greater flexibility with regard to electrical power generation and variation of electrical power conditions is provided to enable better optimisation of performance from equipment within an aircraft.

As indicated above a ram air turbine in accordance with aspects of the present invention extracts power from the air stream about a vehicle in operation. In such circumstances such extraction acts as a drag upon continued movement of the vehicle and in particular an aircraft and in such circumstances allows deceleration whilst providing regenerative electrical power sources. It will be understood that the ram air turbine comprises generally a plurality of blades mounted on an appropriate rotor and shaft to drive the electrical machine associated with the turbine. It will be understood that the pitch of the blades in the turbine may be varied to vary the drag and/or the electrical power generated through the associated electrical machine. Furthermore, as the ram air turbine is typically presented upon a shaft extending from a mounting within a compartment the angle of presentation of that shaft can be adjusted and therefore the presentation of the blades of the turbine in use. Such variations may allow adjustments with regard to drag as well as electrical power generation. The angular presentation of the shaft as well as the blades may be adjusted dependent upon desired drag quotients and electrical power condition variations required.

Aspects of the present invention relate particularly to allowing selective deployment of a ram air turbine to increase drag and therefore reduce air speed particularly with regard to aircraft but potentially also other vehicles. Furthermore, the ram air turbine as indicated allows generation of electrical power or through appropriate configuration of an electrical machine motoring of the ram air turbine to provide desired electrical power regulation as well as adjustments in aerodynamic flow.

It will be understood that ram air turbines may be deployed during a number of phases with regard to vehicle movements and in particular with regard to aircraft flight conditions. Deployment may be continuous or short term dependent upon requirements. Where a ram air turbine is deployed to provide power it will be understood that this may occur as and when required and in such circumstances when such power is no longer required the ram air turbine may be retracted within its compartment again from out of the air stream and therefore will no longer provide the electrical power and/or drag variation in accordance with aspects of the present invention. Temporary provision of electrical power and additional electrical power is typically useful for provision of pulse actuation loads such as in relation to electrical power activation of flaps and slats within an aircraft or other vehicle.

As indicated above ram air turbines may also be adapted for utilisation with regard to vehicles such as ships to assist with regard to ship braking. It will be understood that the ram air turbine will be deployed as appropriate in order to slow a ship and assist in turning or simple stopping of that ship in use or docking.

Furthermore, such utilisation of ram air turbines will also assist with respect to regenerative electrical power generation for the ship. It will be understood with regard to vehicles such as ships provision of means for electrical power storage whether that be through batteries or compressed gas may be more conveniently accommodated than with regard to aircraft.

Modifications and alterations to aspects of the present invention will be appreciated by those skilled in the art. Thus for example, as indicated above the blades utilised in the Ram air turbines may be adjustable but it will also be appreciated that the door utilised as a covering to a compartment accommodating the ram air turbine may also be utilised as a flap directing air flow to the turbine as required.

Claims

Claims 1. A ram air turbine for a vehicle comprising a turbine upon a mounting within a compartment aerodynamically recessed to one side of a fluid stream in use, the turbine upon the mounting in use selectively displaceable into the fluid stream from the compartment to provide a drag variation and/or electrical power condition variation through an electrical machine associated with the turbine.
2. A turbine as claimed in claim 1 wherein the vehicle is an aircraft.
3. A turbine as claimed in claim 1 or claim 2 wherein the compartment has a door displaceable when the turbine is deployed.
4. A turbine as claimed in any of claims 1, 2 or 3 wherein the turbine is deployed when an associated vehicle enters a descent or deceleration phase.
5. A turbine as claimed in any preceding claim wherein the electrical power from the turbine is used directly to power an electrical power system in the vehicle.
6. A turbine as claimed in any preceding claim wherein the electrical power generated from the ram air turbine is used selectively to provide power for pulse activation of electrical systems in the vehicle.
7. A turbine as claimed in any preceding claim wherein the electrical power is stored in a storage means.
8. A turbine as claimed in claim 7 wherein the storage means comprises electrical, mechanical or pneumatic storage means.
9. A turbine as claimed in claim 7 or claim 8 wherein the storage means comprises a battery or a compressed gas vessel.
10. A turbine as claimed in any preceding claim wherein the turbine is used to provide a distinct electrical power supply from other electrical power supply systems in the vehicle.
11. A turbine as claimed in claim 10 wherein the electrical power generated by the ram air turbine is distinct in terms of current, voltage or frequency from other electrical power supply systems in the vehicle.
12. A turbine as claimed in any preceding claim wherein the ram air turbine has a blade assembly and the blade assembly incorporates variable pitch blades to adjust the drag variation.
13. A turbine as claimed in any preceding claim wherein the mounting is configured to present the turbine variably in the air stream.
14. A turbine as claimed in claim 13 wherein the mounting varies the presentation of the turbine in the air stream in terms of angle.
15. A ram air turbine substantially as hereirabefore described with reference to the accompanying drawings.
16. A method of operating a ram air turbine within a moving vehicle whereby the ram air turbine generates or uses electrical power, the method comprising providing the ram air turbine upon a mounting within an aerodynamically recessed compartment to one side of a fluid stream, the ram air turbine selectively deployable upon the mounting into the fluid stream from the compartment and the ram air turbine used to provide a drag variation and/or adjust electrical power conditions in the vehicle.
17. A method as claimed in claim 16 wherein the vehicle is an aircraft.
18. A method as claimed in claim 16 or claim 17 wherein the turbine is deployed when an associated vehicle enters a descent or deceleration phase.
19. A method as claimed in any of claims 16 to 18 wherein the electrical power from the turbine is used directly to power an electrical power system in the vehicle.
20. A method as claimed in any of claims 16 to 19 wherein the electrical power generated from the ram air turbine is used selectively to provide power for pulse activation of electrical systems in the vehicle.
21. A method as claimed in any of claims 16 to 20 wherein the electrical power is stored in a storage means.
22. A method as claimed in claim 21 wherein the storage means is electrical, mechanical, pneumatic or other storage means.
23. A method as claimed in any of claims 16 to 22 wherein the turbine is used to provide a distinct electrical power supply from other electrical power supply systems in the vehicle.
24. A method of operating a ram air turbine within a moving vehicle substantially as hereinbefore described with reference to the accompanying drawings.
25. An aircraft incorporating a ram air turbine as claimed in any of claims 1 to 15.
26. An aircraft incorporating a ram air turbine operated in accordance with a method as claimed in any of claims 16 to 24.