GB2553106B

GB2553106B - A Liquid storage tank assembly and a baffle assembly for a vehicle

Info

Publication number: GB2553106B
Application number: GB1614322.4A
Authority: GB
Inventors: Cheung Raymond; Terry Lawrence
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2016-08-22
Filing date: 2016-08-22
Publication date: 2019-07-31
Anticipated expiration: 2036-08-22
Also published as: GB201614322D0; GB2553106A

Description

A LIQUID STORAGE TANK ASSEMBLY AND A BAFFLE ASSEMBLY FOR A VEHICLE

TECHNICAL FIELD

The present disclosure relates to a liquid storage tank assembly and more particularly, but not exclusively, to a fuel tank assembly for a vehicle. Aspects of the invention relate to a liquid storage tank assembly, to a baffle assembly for a liquid storage tank and to a vehicle.

BACKGROUND

It is known to provide a baffle arrangement in a vehicle fuel tank to control the movement of fuel in the tank caused, for example, when the vehicle accelerates, decelerates and/or corners. If the movement of fuel is not adequately controlled, liquid waves develop and collide and splash on the tank surface causing vibrations to develop in the fuel tank. This can lead to airborne and structure borne noises that are audible to a vehicle passenger. This is commonly referred to as “slosh” and is particularly problematic for vehicles with large fuel tanks and for hybrid and start-stop vehicles where background engine noise is often absent. Similar problems occur in other liquid storage tanks subject to movement, such as bulk liquid transport containers and liquid storage tanks in aircraft, spacecraft, ships and boats. In a vehicle carrying liquid in large volumes, uncontrolled movement of liquid can lead to vehicle stability issues as wells as noise issues.

Known baffle arrangements include the use of a fixed perforated baffle plate. In a fuel tank, the fixed baffle plate typically extends transversely across the tank to control the movement of fuel in a forward and rearward direction of the vehicle, which is often the most problematic. The fixed baffle plate only allows fuel to flow past it through the perforations, reducing the momentum and kinetic energy of the liquid and so reducing slosh noise. Whilst this type of fixed baffle arrangement is effective, it is one dimensional and may not sufficiently control movement of fuel in other directions. A further issue is that noise can be generated as a result of the fuel hitting the fixed baffle.

There is, therefore, a need to provide a liquid storage tank assembly which address the disadvantages of the prior art arrangements.

There is also a need for a liquid storage tank assembly having a baffle arrangement which is capable of controlling the flow of liquid in multiple directions.

There is a further need for a liquid storage tank assembly having a baffle arrangement which is more effective at attenuating the energy of liquid moving in the tank and/or which attenuates the energy in a different manner to the known baffle arrangements.

There is a still further need for a liquid storage tank assembly having a baffle arrangement which produces less noise when impacted by moving liquid.

It is an aim of the present invention to address disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects of the invention provide a liquid storage tank assembly, a vehicle and a baffle assembly for a liquid storage tank assembly.

According to an aspect of the invention, there is provided a liquid storage tank assembly comprising a tank having perimeter walls defining an interior volume for storing liquid and a baffle assembly mounted within the interior volume, characterised in that the baffle assembly comprises at least one rotor mounted for free rotation about an axis, the at least one rotor having a plurality of radially extending blades and the at least one rotor being configured to rotate about the axis of rotation in response to movement of liquid in the interior volume of the tank wherein the axis of rotation of the at least one baffle assembly extends in a vertical direction between upper and lower regions of the tank.

Movement of liquid within the interior volume impinging on the blades may cause the at least one rotor to rotate about the axis of rotation. The blades may be curved. The blades may be curved radially and/or about their longitudinal axis. Alternatively or in addition, the blades may be inclined relative to the axis of rotation at a pitch angle, which pitch angle may vary over the length of each blade.

In an embodiment, the baffle assembly comprises a plurality of rotors mounted for rotation about a common axis of rotation. At least two of said plurality of rotors may be contra-rotating. In an embodiment, the baffle assembly comprises at least three rotors mounted for rotation about a common axis of rotation, each rotor being configured to rotate in an opposite direction about the axis of rotation to an adjacent rotor.

Contra-rotation of the baffle rotors results in the liquid being divided into layers in alternative flow patterns around the axis of rotation (X).

In an embodiment where the baffle assembly has two or more rotors, a drive arrangement is operative between two of the rotors to transmit rotary motion from one rotor to the other. The drive arrangement may comprise a number of wheels which frictionally engage drive surfaces of the two rotors.

The blades may comprise perforations.

There may be a minimal clearance between the radially outer tips of the blades and the walls of the tank. The at least one rotor may have an outer diameter which is only slightly smaller than a minimum internal dimension of the tank, said minimal internal dimension being taken in a direction perpendicular to the axis of rotation in the plane of rotation of the rotor. The outer diameter of the at least one rotor may be at least 85% of the minimum internal dimension of the tank, the minimal internal dimension being taken in a direction perpendicular to the axis of rotation. The outer diameter may be greater than 90% or 95% of the minimum dimension.

The baffle assembly may comprise a shaft mounted to the tank, the at least one rotor being rotatably mounted on the shaft. Alternatively, the baffle assembly may comprise first and second mounting formations on the tank with said at least one rotor rotatably supported between the first and second mounting formations. In an embodiment, the baffle assembly comprises at least two rotors, one of the rotors being rotatably supported on the first mounting formation and a further rotor being rotatably support on the second mounting formation. Each rotor may be rotatably interconnected with an adjacent rotor. At least one of the first and second mounting formations may be a stub axle.

There may be more than one baffle assembly mounted within the interior volume. In which case, at least one baffle assembly may have an axis of rotation that is not parallel to the axis of rotation of at least one other of the baffle assemblies.

The tank may be liquid storage tank for a vehicle. The tank may be a fuel tank for a vehicle.

According to another aspect of the invention, there is provided a liquid storage tank assembly comprising a tank having perimeter walls defining an interior volume for storing liquid and a baffle assembly mounted within the interior volume, the baffle assembly comprising a plurality of rotors mounted for rotation about an axis, each rotor having a plurality of radially extending blades, wherein at least two of the rotors are configured to rotate in opposite directions about the axis of rotation in response to movement of liquid in the interior volume of the tank.

According to another aspect of the invention, there is provided a vehicle comprising a liquid storage tank assembly according to either of the previously mentioned aspects of the invention.

According to a still further aspect of the invention, there is provided a baffle assembly for use in a liquid storage tank according to the either of the first or second mentioned aspects of the invention, the baffle assembly comprising at least one rotor mountable in a tank for free rotation about an axis, the at least one rotor having a plurality of radially extending blades.

The baffle assembly, may have any of the features of the baffle assembly of the liquid storage tank assembly according to the first aspect of the invention as set out above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a motor vehicle having a liquid storage tank in accordance with an aspect of the invention;

Figure 2 is a side view of an embodiment of baffle assembly for use in a liquid storage tank in accordance with an aspect of the invention, schematically illustrating the walls of a tank in ghost;

Figure 3 is a perspective view from the side of a further embodiment of a baffle assembly for use in a liquid storage tank in accordance with an aspect of the invention;

Figure 4 is a perspective view from above of the baffle assembly of Figure 3 and

Figure 5 is a view similar to that of Figure 3 but showing a still further embodiment of a baffle assembly for use in a liquid storage tank in accordance with an aspect of the invention.

DETAILED DESCRIPTION

The invention will be described by way of example only with reference to embodiments in which the liquid storage tank assembly is a fuel tank assembly for a vehicle. However, the arrangements disclosed can be adapted for any suitable applications in which a liquid is stored in a tank subject to movement. Such applications might include tanks for storage of other types of liquid in a vehicle, including liquids such as urea, water, waste water and the like. Other suitable applications include bulk transport tanks for liquids as well as storage tanks used in aerospace, rail and nautical vehicles.

The term “vehicle” as used herein is not limited to motor vehicles such as cars, lorry’s, trucks, vans, busses and the like but includes any self-propelled or towed conveyance suitable for transporting liquid in a tank or which may incorporate a tank for storing liquid of any type.

The terms “upper”, “lower”, horizontal”, and vertical” and the like as used herein refer to the relative disposition of the parts or features when located on a vehicle standing upright on a generally horizontal surface and should be construed accordingly.

Throughout this specification, corresponding reference numerals but increased by 100 in each case will be used to denote corresponding parts and features in each of the embodiments.

Figure 1 illustrates schematically a motor vehicle 10 having a fuel tank assembly 12 in accordance with an aspect of the invention. The fuel tank assembly 12 includes a fuel tank 14 having perimeter walls 16 which define a main reservoir 18 having an interior volume within which liquid fuel is stored and a filler neck 20 through which fuel can be introduced into the interior volume of the reservoir 18. The fuel tank 14 can be constructed from any suitable materials and in any suitable manner. For example, the fuel tank 14 may be made from metal, polymer, or composites. The fuel tank 14 contains a fuel pump (not shown) and/or a fuel level sensor (not shown) as is well known in the art.

Mounted within the interior volume of the main reservoir portion 18 of the fuel tank is a baffle assembly 22 for controlling the movement of the fuel in the reservoir 18.

Several embodiments of a baffle assembly 22 in accordance with an aspect of the invention and which are suitable for use in the fuel tank 14 will now be described with reference to Figures 2 to 5.

Referring to Figure 2, a first embodiment of a baffle assembly 22 for use as part of the fuel tank assembly 12 includes a shaft 24 to which are mounted a pair of rotors 26A, 26B. The baffle assembly 22 is mounted in the reservoir 18 of the fuel tank 12 and the position of the peripheral walls 16 of the tank which define the reservoir 18 are indicated in ghost in Figure 2. The peripheral walls 16 define an upper wall 28, a lower wall 30 and side walls 32. The shaft 24 is mounted to a base 34 which is affixed to the lower wall 30 of the reservoir so that the shaft 24 extends generally vertically upwardly from the bottom wall 30 toward the upper wall 28.

The rotors 26A, 26B are located one above the other on the shaft. Each rotor has a generally cylindrical hub 36A, 36B mounted to the shaft 24. The hubs 36A, 36B are free to rotate about the shaft 24 such that the rotors 26A, 26B rotate about the longitudinal axis X of the shaft which is disposed generally vertically. The longitudinal axis X of the shaft will be referred to as the rotational axis of the baffle assembly 22. The hubs 36A, 36B may be a close sliding fit directly about the shaft 24 or bearing means may be provided between the hubs 36A, 36B and the shaft 24.

Each rotor 26A, 26B has three blades 38A, 38B extending radially outwardly from the hub 36A, 36B. The blades 38A, 38B are in the form of relatively thin plates of generally rectangular shape with rounded, radially outer tips 38C. Each blade has a longitudinal axis Y which extends radially outwardly relative to the longitudinal axis X of the shaft. The blades are aligned with their widths extending generally in the direction of the axis of rotation X, such that their major surfaces are at least partially aligned in a vertical direction. The blades 38A, 38B act as baffles which are able to rotate about the axis X in response to movement of liquid across the reservoir 18 impinging on the blades. In the present embodiment of a fuel tank 12, the movement of fuel in the reservoir 18 will tend to be predominantly horizontal, that is to say forward or backwards in the longitudinal direction of the vehicle or from side to side in a lateral direction or a combination of the two. Put another way, since the axis of rotation X is aligned generally vertically, the movement of fuel is predominantly in a direction perpendicular to the axis of rotation X. Accordingly, the blades 38A, 38B are arranged so that movement of fuel across the tank within the plane of rotation a rotor having at least a component which is perpendicular to the axis of rotation X will impinge on the blades of that rotor.

Operation of the baffle assembly 22 with a full fuel tank 14 will now be described.

If fuel is caused to move across the tank 14, say in the direction of arrow A in Figure 2, some of the moving fuel will imping on the blades 38A, 38B of the rotors. If the forces acting on a rotor to either side of the axis X are not equal, the rotor will be rotated about the axis X until the forces are brought into balance. Generally, this will have the effect of aligning the blades relative to the direction of movement of the fuel in a position at which they are most effective in dampening the movement of the fuel and thus reducing the momentum and kinetic energy in the moving fuel. Thus, regardless of the direction of movement of the fuel across the tank, the rotor blades 38A, 38B are always brought into a position at which they operate effectively as baffles. This contrasts with static baffle plates which may only be effective in relation to fuel moving in certain directions across the tank but not others. A further benefit of the rotating baffle assembly 22 is a reduction in impact noise. Because the blades 38A, 38B move, the force with which the fluid impacts on the blades is reduced, thus reducing the impact noise in comparison with a fixed baffle plate. In addition, imparting movement to the rotor will also help to dissipate some of the momentum and kinetic energy from the fuel.

It should be noted that the rotors 26A, 26B are freely mounted about the shaft 24, that is to say there is no driving connection between the rotors and the shaft. The rotors 26A, 26B are driven to rotate only by the movement of liquid in the tank. Furthermore, the two rotors 26A, 26B are able to rotate about the axis X independently of one another.

In this embodiment, the blades 38A, 38B are inclined relative to the axis of rotation X at a pitch angle which varies along the length of the blades. The inclination of the blades will direct fuel in either a downward or upward direction in the tank as it moves over the blades. This may also be beneficial reducing the momentum and kinetic energy in the fuel and preventing slosh. However, the blades 38A, 38B need not be inclined and could be arranged with their major surfaces substantially parallel to the axis of rotation X.

Having multiple rotors 36A, 36B aligned along the axis X which are able to rotate about the axis freely and independently of one another allows the baffle assembly 22 to continue to operate effectively even when the tank is not full. As the fuel level in the tank falls, less fuel will impinge on the blades 38B of the upper rotor 36B and the forces may be insufficient to cause the upper rotator 36B to rotate. Nevertheless, the lower rotor 36A will continue to operate as described above until the fuel level drops significantly as the tank empties. It will be appreciated that the baffle assembly 22 could have more than two rotors rotatable about the axis X if desired to vary the damping at a range of fuel levels in the tank.

The blades 38A, 38B on the rotors 26A, 26B are dimensioned to maximise the chances of fluid moving across the tank contacting at least one blade on one of the rotors and/or to minimise gaps through which fuel can pass from one side of the tank to another without impacting on a blade. Accordingly, the length of the blades is selected so that there is a minimal spacing between the tips of the blades and the closest side wall region 32 of the tank 14. In other words, the outer dimeter of each rotor 26A, 26B is dimensioned to be only slightly less than the minimum internal dimension of the tank 14, taken in a direction perpendicular to the axis to rotation X in the plane of rotation of the rotor. The outer dimeter may be 85%, or 90%, or 95% or more of the minimum internal dimension. In the vertical direction of the tank, the blades are dimensioned to minimise the gaps between the upper wall 28 of the tank and the upper edges of the blades 38B on the upper rotor 26B, the lower wall 30 of the tank and the lower edges of the blades 38A on the lower rotor 26A and between the blades 38A, 38B on the two rotors themselves. The design of the tank itself may be configured for optimal use with the rotor baffle assembly 22. The rotors 26A, 26B are also configured so that fluid moving across the tank 12 within the plane of rotation of a rotor 26A, 26B in any direction will contact at least one blade on that rotor regardless of the rotational orientation or the rotor. In the present embodiment, each rotor 26A, 26B has three blades 38A, 38B spaced 120 degrees apart but more than three blades can be provided. For example, each rotor could have four or more blades which would typically be equi-spaced about the hub.

Figures 3 and 4 illustrate a further embodiment of a baffle assembly 122 for use in the fuel tank 14 of Figure 1. The baffle assembly 122 is similar to that of the previous embodiment 22 and so only significant differences will be described in detail.

The baffle assembly 122 has a shaft 124 mounted to a base 134 and a pair of baffle rotors 126A, 126B mounted to the shaft for rotation about a longitudinal axis of the shaft. The baffle rotors 126A, 126B are similar to the rotors of the previous embodiment except that they each have four radially extending blades 138A, 138B equi-spaced 90 degrees apart about on the hub 136. In this embodiment, the blades 138A, 138B are arranged so that movement of the fuel having at least a component which is perpendicular to the axis of rotation X impinging on the blades with sufficient force will cause the rotors 126A, 126B to rotate about the axis X. In the present embodiment, the blades 138A, 138B are radially curved, that is to say they curve radially relative to the axis of rotation X. As best seen in Figure 4, the blades 138A on one rotor 126A are all curved in a first direction whilst the blades 138B on the other rotor 126B are all curved in the opposite direction. This arrangement results in the rotors 126A, 126B being rotated in opposite directions in response to movement of fuel across the tank. Alternatively, or additionally, to being curved radially, the blades 138A, 138B could be curved about their longitudinal axis Y so as to have a vertically scooped formation. Those skilled in the art of rotor blade design will appreciate that the blades can be configured in numerous different ways to achieve contra-rotation and any known arrangements for configuring the blades to cause rotation of the rotors in response to movement of a liquid in the tank 14 can be adopted.

Operation of the rotary baffle assembly 122 will now be described.

With reference to Figure 3, movement of fuel across the tank 14 in the direction of arrow B within the plane of rotation of the lower rotor 126A will cause the lower rotor 126A to rotate in a clockwise direction (as viewed from above) about the axis of rotation X, due to the curved shape of the blades. Whereas, movement of fuel across the tank in the same direction within the plane of rotation of the upper rotor 126B will cause the upper rotor to rotate in an anticlockwise direction (as viewed from above) about the axis of rotation X. Rotational movement of a rotor 126A, 126B and its blades will tend to direct fuel flowing across the tank to flow in one direction or another about the axis of rotation X. Thus in the above example where the lower rotor 126A rotates clockwise and the upper rotor 126B rotates anti-clockwise, fuel in the plane of rotation of the lower rotor will be directed to flow in a clockwise direction about the axis of rotation X, whilst fuel in the plane of rotation of the upper rotor 126B will tend to be directed about the axis of rotation X in an anti-clockwise direction. Deflection of the fuel about the axis of rotation X by a baffle rotor 126A, 126B attenuates the momentum and kinetic energy of the liquid. Furthermore, the use of contra-rotating baffle rotors 126A, 126B in accordance with an aspect of the invention has an additional effect of dividing the fuel into layers which are directed in different directions about the axis of rotation X. This further attenuates the momentum and kinetic energy of the fuel. Without wishing to be bound to any particular theory, it is believed that the movement of adjacent layers of fuel in different directions produces shear forces between the liquid in the different layers which attenuates the momentum and/or kinetic energy in the liquid.

In the baffle assemblies 22, 122 in accordance with the embodiments so far described, the rotors 26A, 26B; 126A, 126B rotate independently of one another. This may be desirable in certain applications. However, there may be circumstances where it is desirable to provide a driving engagement between rotors in a baffle assembly so that an upper rotor is caused to rotate in response to movement of a lower rotor even when the fuel is below the level of the upper rotor. Such an embodiment is illustrated in Figure 5.

The baffle assembly 222 in Figure 5 is similar to the baffle assembly 122 in accordance with the previous embodiment, to which the reader should refer for a detailed description. The baffle assembly 122 differs from the assembly 122 in that it has a drive arrangement, indicated generally at 242, which is operative between the hubs 236A, 236B of the rotor assemblies 226A, 226B. The drive arrangement 242 comprises a plurality of wheels 244 arranged in a cage 246. The wheels 244 are each able to rotate about their own axis and frictionally engage an upper drive surface of the hub 136A of the lower rotor and a lower drive surface of the upper hub 236B. The wheels 144 act to transfer drive between the two rotor assemblies whilst allowing them to rotate in opposite directions about the axis of rotation X. In use, even when the level of fuel in the tank has fallen below the upper rotor, rotational movement of the lower rotor 226A in response to movement of fuel across the tank in its plane of rotation is transferred to the upper rotor 226B so that the upper rotor 226B is rotated in the opposite direction. Causing the upper rotor 226B to rotate in addition to the lower rotor 226A provides additional resistance to the movement of the fuel in the lower portion of the tank which can help to further attenuate the momentum and/or kinetic energy in the fuel.

As shown in the accompanying drawings, the baffle blades 38A, 38B, 138A, 138B, 238A, 238B may be perforated. However, this is not essential and the blades 38A, 38B, 138A, 138B, 238A, 238B may be solid. Perforations or through holes 40, 140, 240 in the blades reduces the force with which the fuel impacts the blades, dissipating energy through the holes. This may be desirable to reduce the noise and vibration produced by fuel impacting on the blades. However, the turning force on a baffle rotor due to movement of the fuel is the product of pressure (i.e. force per unit area) and the surface area of the baffle blades. Accordingly, reducing the surface area by perforating the blades reduces the turning force applied to the rotor. In some applications it may be more beneficial to use solid blades as this will result in greater rotation of the baffle rotors, with the resulting attenuating effects on the momentum/kinetic energy of the liquid as discussed above. Furthermore, rotation of the blades will itself reduce the impact noise. In practice, whilst at least some perforations may be provided in the blades to reduce impact noise, it is expected that in most applications perforations will only be introduced to the extent that this does have a significant adverse effect on the rotation of the rotors caused by movement of the liquid and the benefits which result therefrom. This is particularly so for baffle assemblies with contra-rotating rotors. Those skilled in the art will be able to optimise the design based on the desired outcomes of any particular application.

The components of the baffle assemblies 22, 122, 222 can be made of any suitable materials, taking into account suitability for immersion in any given liquid. Suitable material may include any of those used for the tank itself, such as: metal, polymer, or composites, for example

Whilst in the embodiments described the rotors 26A, 26B, 126A, 126B, 226A, 226B are mounted about a shaft 24, 124, 224 for rotation, it will be appreciated that the rotors could be mounted within the tank for rotation about a common axis X without the use of a shaft extending through both rotor hubs. For example, the hub of the lower rotor 26A, 126A, 226A could be mounted to a feature such as a stub axle on the lower wall 30 of the tank and the hub of the upper rotor 26B, 126B, 226B mounted to a corresponding feature on the upper wall 28 of the tank. The two hubs may be inter-connected in a manner which permits them to rotate relative to one another.

The above embodiments are described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. For example, the number of baffle rotors in a baffle assembly 22, 122, 222 can be varied. In some applications a single baffle rotor may prove to be beneficial whilst for other applications more than two baffle rotors rotating about a common axis can be adopted. Where three or more contra-rotating baffle rotors are provided in a baffle assembly, it is expected that adjacent rotors will be configured to rotate in opposite directions to create adjacent layers of liquid which move in different directions. Thus in a baffle assembly having three contra-rotating baffle rotors, the middle rotor could be configured to rotate in the opposite direction to that of the upper and lower baffle rotors. However, it is not essential in the broadest aspect of the invention to use contra-rotating baffle rotors as some benefit may be obtained by using more than one baffle rotor in a baffle assembly where all the rotors rotate in the same direction about the axis of rotation. It should also be appreciated that more than one baffle assembly 22, 122, 222 may be incorporated into a liquid storage tank 14 in accordance with the invention. For use in land based vehicles in particular, it is expected that the axis of rotation X will extend between upper and lower regions of the tank in a generally vertical or upright alignment. However, in some cases the axis may be aligned differently and the direction of the axis of rotation X can be selected to best suit the needs of any given application. Furthermore, where more than one baffle assembly is incorporated into a tank 14, the baffle assemblies need not all be aligned with their axes of rotation X parallel to one another. In some applications it may be advantageous to have baffle rotors which rotate about different, non-parallel axes of rotation X. Finally, as discussed, the invention is not limited to application a fuel tank in or for a vehicle but can be applied to any liquid storage tank which is subject to movement or agitation resulting in movement of liquid in the tank which requires control.

Claims

1. A liquid storage tank assembly comprising a tank having perimeter walls defining an interior volume for storing liquid and a baffle assembly mounted within the interior volume, characterised in that the baffle assembly comprises at least one rotor mounted for free rotation about an axis, the at least one rotor having a plurality of radially extending blades and the at least one rotor being configured to rotate about the axis of rotation in response to movement of liquid in the interior volume of the tank wherein the axis of rotation of the at least one baffle assembly extends in a vertical direction between upper and lower regions of the tank.

2. A liquid storage tank assembly as claimed in claim 1, wherein the blades are curved.

3. A liquid storage tank assembly as claimed in any one of claim 1 or claim 2, wherein the blades are inclined relative to the axis of rotation at a pitch angle.

4. A liquid storage tank assembly as claimed in claim 3, wherein the pitch angle varies over the length of each blade.

5. A liquid storage tank assembly as claimed in any one of the preceding claims, wherein the baffle assembly comprises a plurality of rotors mounted for rotation about a common axis of rotation.

6. A liquid storage tank assembly as claimed in claim 5, wherein at least two of said plurality of rotors are configured to rotate in opposite directions about the axis of rotation in response to movement of liquid in the interior volume of the tank.

7. A liquid storage tank assembly as claimed in claim 6, wherein the baffle assembly comprises at least three rotors mounted for rotation about a common axis of rotation, each rotor being configured to rotate in an opposite direction about the axis of rotation to an adjacent rotor in response to movement of liquid in the interior.

8. A liquid storage tank assembly as claimed in any one of claims 5 to 7, in which a drive arrangement is operative between at least two rotors to transmit rotary motion from one rotor to the other.

9. A liquid storage tank assembly as claimed in any one of the preceding claims, wherein the blades comprise perforations.

10. A liquid storage tank assembly as claimed in any one of the previous claims, wherein an outer diameter of the at least one rotor is at least 85% of a minimum internal dimension of the tank, the minimal internal dimension being taken in a direction perpendicular to the axis of rotation.

11. A liquid storage tank assembly as claimed in any one of the preceding claims, wherein the baffle assembly comprises a shaft mounted to the tank, the at least one rotor being rotatably mounted on the shaft.

12. A liquid storage tank assembly as claimed in any one of claims 1 to 11, wherein the baffle assembly comprises first and second mounting formations mounted to the tank, the at least one rotor rotatably supported between the first and second mounting formations.

13. A liquid storage tank assembly as claimed in claim 12, wherein the baffle assembly comprises at least two rotors, one of the rotors being rotatably supported on the first mounting formation and a further rotor being rotatably support on the second mounting formation.

14. A liquid storage tank assembly as claimed in claim 12 or claim 13, wherein at least one of the first and second mounting formations is a stub axle.

15. A liquid storage tank assembly as claimed in any one of the preceding claims, wherein more than one baffle assembly is mounted within the interior volume of the tank.

16. A liquid storage tank assembly as claimed in claim 16, wherein at least one baffle assembly has an axis of rotation that is not parallel to the axis of rotation of at least one other of the baffle assemblies.

17. A liquid storage tank assembly as claimed in any one of the preceding claims, wherein the tank is a liquid storage tank for a vehicle.

18. A liquid storage tank assembly as claimed in claim 17, wherein the tank is a fuel tank for a vehicle.

19. A vehicle comprising a liquid storage tank assembly as claimed in any one of claims 1 to 18.

20. A baffle assembly for use in a liquid storage tank as claimed in any one of claims 1 to 18.