FIELD OF INVENTION

This invention relates to an excavation apparatus, and in particular, though not exclusively, to an underwater (e.g., subsea) excavation apparatus. The invention also relates to an excavation system, device or tool, such as an underwater excavation system, device or tool, and to a method of excavation, such as underwater excavation.

The invention also pertains to an underwater excavation apparatus or system comprising means for disturbing a seabed, ocean floor, lake bed, river bed soil or soils or the like, e.g., for disturbing relatively firm soils.

BACKGROUND TO INVENTION

Mass flow excavators operate by directing a high volume flow of fluid under low pressure at a seabed to displace seabed material. This is in contradistinction to jet type apparatus which direct a low volume flow of fluid under high pressure at the seabed. A mass flow excavator is typically tethered from a vessel by means of a crane wire, which is used to lower and retrieve the excavator, and to maintain the excavator at a given distance from the seabed or structure requiring excavation, such as a subsea oil or gas pipeline. In order to control the excavation, sonar detection means can be used to allow the excavator operator to view the excavation in real time. Cameras and metal detection means can also be used to assist the operator.

Underwater mass flow excavation apparatus are known. For example, GB 2 297 777 A (HOLLANDSCHE BETONGROEP) and WO 98/27286 (LEDINGHAM CHALMERS TRUSTEE et al), the contents of which are incorporated herein by reference.

Mass flow excavation is a means of creating cavities in a seabed or the like with relatively low pressure(s) (usually measured in Kilopascals, KPa), e.g., in sand, soft clay, and/or pre-loosened or disturbed material. The mass flow excavation may be assisted by a mechanical means or high pressure jetting means for agitating the seabed. These ancillary means of cutting the seabed then rely on mass flow excavation means to remove and disperse the seabed material. Mass flow excavators typically comprise a hollow body or housing and at least one impeller or rotor provided within the housing which draws fluid into the housing and directs the fluid out of the housing towards the seabed.

Known mass flow excavators comprise impellers designed to draw in large volumes of fluid, and to discharge the fluid at relatively low speed and low pressure - typically less than 7m/s and less than 25 KPa. Due to the relatively low pressure and low fluid flow speed of mass flow excavation, many passes may be required to effectively excavate an area, as with each pass only a limited penetration of the seabed may be achieved. It is a further characteristic of mass flow excavation that trenches created in the seabed may be relatively wide but shallow. This is because the mass flow excavator may first move looser material on the surface due to pressure limitations before penetrating firmer material underneath, creating a wide and ill-defined or uncontrolled excavation profile.

Further, mass flow excavation apparatus are primarily suitable for excavation by directing fluid at the seabed, but due to the low-pressure nature of the apparatus, such are of limited use in the collection and removal of seabed material by suction. Thus, after the mass flow device has disturbed the seabed material, a separate tool such as a centrifugal pump, may require to be deployed to suck up and remove the material.

To distinguish from “mass flow”, the term “controlled flow” is hereinafter used in connection with an excavator of the present invention which may be configured to produce and/or direct a flow of fluid at a pressure of typically around 35 KPa to 120 KPa and volume flow of typically around 1 m ³ /s to 8 m ³ /s. In contrast to mass flow devices, the higher-pressure capability of a controlled flow apparatus or device makes the controlled flow apparatus or device suitable for excavation in both excavation (e.g., jetting) mode and also in suction mode where the device may be used for collection and transportation of seabed material away from an excavation site.

It is or may be an object of at least one embodiment of at least one aspect of the present invention to obviate or mitigate one or more problems or disadvantages in the prior art.

It is or may be an object of at least one embodiment of at least one aspect of the present invention to seek to provide an excavation apparatus, such as an underwater excavation apparatus, which is beneficially adapted and/or configured for use in relatively shallow depths, e.g., 1 metre or less.

It is or may be an object of at least one aspect of at least one embodiment of the present invention to provide a means to address a desire for excavating in a relatively controlled and/or rapid manner, e.g., with well-defined seabed excavation profiles.

It is or may be an object of at least one aspect of at least one embodiment of the present invention to provide a means to address a desire for excavating in relatively harder soil conditions, e.g., with soil hardness from 100KPa to 400 KPa or above 120KPa. SUMMARY OF INVENTION

According to a first aspect of the present invention there is provided an excavation apparatus, such as an underwater excavation apparatus or a controlled flow (underwater) excavation apparatus, comprising a rotor having or comprising one or more or a plurality of first (impeller) rotor blades and one or more or a plurality of second (splitter/splitter impeller) rotor blades.

Provision of a/the second rotor blade(s), e.g., between adjacent first blades, may effectively narrow a width of an end of a fluid passage, e.g., between adjacent first rotor blades. This may obviate or mitigate a need to increase a diameter of the rotor if the excavation apparatus is to be used for hard soils, e.g., above 100KPa such as 100KPa to 400KPa.

The excavation apparatus may comprise a stator. The stator may have or comprise a plurality of first stator blades and optionally a plurality of second (splitter) stator blades.

The excavation apparatus beneficially may comprise a single rotor.

The excavation apparatus beneficially may comprise a single stator.

The apparatus may comprise a housing.

The housing may comprise or have at least one inlet and at least one or an outlet.

The first (impeller) rotor blades may comprise one or more, e.g., a plurality of primary (impeller) rotor blades.

The second (splitter) rotor blades may comprise one or more, e.g., a plurality of secondary or splitter rotor blades.

A/each second rotor blade may be provided between adjacent (pairs of) first rotor blades.

A leading edge of a/each second rotor blade may commence or start midway along, e.g., 35% to 45% along, a length of a/an adjacent first rotor blade, e.g., 38% measured at a hub and 42% measured at the housing.

A height of the first rotor blade(s) and/or second rotor blade(s) may reduce along a length of the respective blade, e.g., in a direction from inlet to outlet.

A distance between and/or an area of a flow path between adjacent first and second rotor blades and/or a distance between and/or an area of the flow path between adjacent primary rotor blades and/or between adjacent splitter rotor blades may increase along the length of the respective rotor blades. (In each case the length of the respective rotor blade may be measured from the at least one inlet towards the outlet). Such arrangement may be of benefit in providing an excavation apparatus adapted for use in firmer seabed or riverbed conditions which require higher pressure in order to excavate the soil.

The rotor and/or the stator may be provided in the housing. The housing may comprise an axis or longitudinal axis, the rotor and the stator optionally being arranged coaxially upon or with the axis.

The rotor may be provided proximal the inlet(s). The stator may be provided proximal the outlet.

The rotor may have a rotor rotation axis, which may comprise or be coincident with a/the longitudinal axis of the housing.

The rotor may comprise a first body. The plurality of first and/or second rotor blades may be provided within the housing.

In use, flow of fluid past or across the rotor may be at a first angle a from the axis of rotation.

There may be excavation and/or suction modes of the excavation apparatus. In excavation and/or in suction mode fluid may flow from the at least one inlet to the outlet of the excavation apparatus.

The rotor rotation axis may extend between (a level of) the at least one inlet and the outlet.

The first body may comprise a first cone member.

The first angle a may diverge away from the axis in a direction away from at least one of the at least one inlets and towards the outlet.

An apex of the rotor or first cone member may face the inlet or an inlet end of the housing.

The plurality of first and/or second rotor blades may comprise aerofoil blades, which may be optionally disposed, such as circumferentially disposed, on a/the first cone member.

The first stator blades may comprise one or more, e.g., a plurality of primary stator blades.

The second stator blades may comprise one or more, e.g., a plurality of secondary or splitter blades.

A/each second stator blade may be provided between an adjacent pair of first stator blades.

A leading edge of a/each second stator blade may commence or start midway alone, e.g., 45% to 55% along, a length of an adjacent first stator blade, e.g., 48% measured at the hub and 52% measured at the housing. A height of the first and second stator blades may increase (or alternatively reduce) along a length of the respective stator blade, e.g., in a direction from inlet to outlet.

A distance between and/or an area of the flow path between adjacent first and second stator blade and/or a distance between and/or an area of the flow path between adjacent primary stator blades and/or between adjacent splitter stator blades may decrease along the length of the respective stator blades. In each case the length of the stator blade being measured from inlet towards outlet. Such arrangement may be of benefit in creating an excavation apparatus adapted for use in firmer seabed or riverbed conditions which require higher pressure in order to excavate the soil.

Such arrangement may be of benefit in excavation apparatus adapted for use in relatively shallow waters, e.g., as such may allow relatively low profile/height excavation apparatus.

The stator may be coaxial with the rotor and/or optionally the stator may be provided between the rotor and the outlet.

In use, flow of fluid past or across the stator may be at a second angle p from the axis of rotation of the rotor.

The stator may comprise a second body, such as a second cone member.

The second angle may converge towards the axis in a direction away from the inlet and towards the outlet.

An apex of the stator or second cone member may face the outlet.

The plurality of first and second stator blades may comprise aerofoil blades, which may be disposed on a/the second cone member.

The first angle a may be selected from either: in the range of 55° to 75°, or 65°.

The second angle p may be selected from in the range of 55° to 75°, or 65°.

The at least one inlet may be provided on or at a side or sides or on or at an end of the housing.

The at least one inlet may be provided around, e.g., circumferentially or peripherally around a/the side of the housing.

The housing may comprise a longitudinal axis. The housing may be symmetrical with respect to the longitudinal axis.

The one or more inlets may be provided inclined and/or offset from or transversely or substantially transversely to the longitudinal axis.

The one or more inlets may be provided perpendicularly or substantially perpendicularly to the longitudinal axis. The/each of the one or more inlets may be provided non-parallel to the longitudinal axis of the housing.

The/each of the one or more inlets may be provided at an angle, e.g., non-zero (0°) angle, e.g., perpendicularly or substantially perpendicularly, to the/each of the one or more outlets.

The/each at least one inlet may be provided near or adjacent an end of the housing.

The/each of the one or more outlets may be provided on or at an/another end of the housing such as on and/or parallel to a/the longitudinal axis.

The apparatus may be adapted to provide an inclined or horizontal or substantially horizontal or a non-vertical or substantially non-vertical flow of fluid/water into the housing, in use, such as in a first or excavation mode of operation.

The fluid/water flow into the housing may be inclined at a converging angle to a longitudinal axis of the housing.

The excavation apparatus may be adapted to provide a coaxial or substantially coaxial or vertical or substantially vertical or a non-horizontal or substantially nonhorizontal flow of fluid/water out of or from the housing, in use.

The excavation apparatus may be adapted to provide and/or direct, in use, a flow of fluid/water, e.g., at a pressure of 200 KPa to 400 KPa and/or a volume flow of 0.5m ³ /s to 4m ³ /s.

There may be provided a fluid flow path(s) or passage extending from the/each at least one inlet to the outlet. The at least one rotor and/or the at least one stator may be provided in the flow path.

The/each fluid flow path may comprise a first (inlet) section, which may extend from the at least one inlet.

The/each fluid flow path may comprise a second (rotor) section, which may contain at least part of a rotor. Said second section may diverge away from a/the (longitudinal) axis of the housing.

The/each fluid flow path may comprise a third (stator) section, which may contain at least part of a stator. Said third section may converge towards a/the (longitudinal) axis of the housing.

The/each fluid flow path may comprise a fourth (outlet) section, which may extend to the at least one or the outlet.

The/each fluid flow path may comprise a first inlet portion/fi rst portion which may be provided at or adjacent the/each at least one inlet. Said first inlet portion/first portion may optionally and advantageously converge towards a/the (longitudinal) axis of the housing, e.g., at a non-zero angle, e.g., between 0° and 90°, 45°, and 90°, or at 90°. Said first inlet portion/first portion may optionally and advantageously be substantially horizontal, in use, and/or perpendicular to a/the (longitudinal) axis of the housing and/or said first inlet portion/first portion may be substantially straight.

The/each fluid flow path may comprise a second inlet portion/second portion, which may extend or continue from the first inlet portion/first portion. Said first inlet portion/second portion may optionally and advantageously be curved, bent or arcuate and/or may be convex relative to a/the (longitudinal axis) of the housing.

The/each fluid flow path may comprise a rotor portion/third portion, which may extend or continue from the inlet section/second inlet portion/second portion. Said first rotor portion/third portion may optionally and advantageously be substantially straight, may be coincident with or contain at least a part or parts of the rotor, and/or may diverge away from a/the (longitudinal) axis of the housing, e.g., in a flow direction from the inlet to the outlet, e.g., at an angle a of 55° to 75°, e.g., 65°

The/each fluid flow path may comprise a further or intermediate portion/fourth portion, which may extend or continue from the first rotor portion/third portion. Said further or intermediate portion/fourth portion may optionally and advantageously be curved, bent or arcuate, and/or may be concave relative to a/the (longitudinal) axis of the housing.

The/each fluid flow path may comprise a stator portion/fifth portion which may extend or continue from the further or intermediate portion/fourth portion. Said first stator portion/fifth portion may optionally and advantageously be substantially straight, may be coincident with or contain at least part or parts of the stator, and/or may converge towards a/the (longitudinal) axis of the housing, e.g., in a flow direction from the inlet to the outlet, e.g., at an angle p of 55° to 75°, e.g., 65°. Such arrangement may be of benefit for excavation apparatus adapted for use in relatively shallow waters, e.g., as such may allow for a relatively low profile/height excavation apparatus.

The/each fluid flow path may comprise a first outlet portion/sixth portion, which may extend or continue from the stator portion/fifth portion. Said first outlet portion/sixth portion may optionally and advantageously be curved, bent or arcuate, and/or may be convex relative to a/the (longitudinal) axis of the housing.

The/each fluid flow path may comprise a second outlet portion/seventh portion, which may extend or continue from the first outlet/sixth portion. Said second outlet portion/seventh portion may be provided at or adjacent the outlet. Said second outlet portion/seventh portion may optionally and advantageously be substantially vertical, in use, and/or parallel to a/the (longitudinal) axis of the housing, and/or substantially straight.

In a first mode of operation, which may comprise an excavation mode, the outlet may face an area to be excavated, and in such mode the inlet(s) may be provided above, e.g., directly above, the outlet.

In a second mode of operation, which may comprise a suction mode, the inlet may be proximal an area which has been excavated and/or requires to be cleared, and in such mode the inlet(s) may be provided below, e.g., directly below, the outlet.

An inside of the housing may converge from the at least one inlet towards the rotor.

The inside of the housing may diverge from the inlet end of the rotor towards the outlet end of the rotor.

The inside of the housing may converge from the stator towards the outlet.

The outlet may be substantially coaxial with the rotor and/or the stator and/or the axis of the housing.

The housing may be circumferentially/rotationally symmetrical about a/the axis of the housing.

The excavation apparatus may comprise means or an arrangement for dampening reactive torque on the excavation apparatus caused by rotation of a/the rotor, in use.

The excavation apparatus and/or the at least one rotor beneficially may comprise a single rotor.

The torque dampening means beneficially does not comprise a second rotor, such as a second rotor counter-rotating to the at least one (single) rotor.

The excavation apparatus and/or the at least one stator beneficially may comprise a single stator.

The housing may comprise a hollow body.

The rotor and/or the stator may be provided in the housing. The housing may comprise an axis. The rotor and the stator may be arranged coaxially, such as upon the axis. The housing may be provided upon the axis. The rotor may be provided proximal the at least one inlet and/or the stator may be provided proximal the outlet.

The rotor may comprise a first body, such as a first cone body, and/or the plurality of first and second rotor blades, e.g., disposed on the first body.

The stator may comprise a second body, such as a second cone body, and/or the plurality of first and/or second stator blades, e.g., disposed on the second body.

The torque dampening means may comprise or include anti-rotation vanes. The excavation apparatus may comprise a motor for driving the rotor. The at least one inlet may be provided (longitudinally) between a/the motor and the rotor.

According to a second aspect of the present invention there is provided an excavation system or tool, such as an underwater system or tool, comprising at least one excavation apparatus according to the first aspect of the present invention.

According to a third aspect of the present invention there is provided a method of excavation, such as a method of underwater excavation, the method comprising: providing at least one excavation apparatus according to the first aspect of the present invention; and excavating a location, such as an underwater location, using said excavation apparatus.

It should be understood that any features defined above in accordance with any aspect of the present invention or below in relation to any specific embodiment of the present invention may be utilised, either alone or in combination with any other feature defined in any other aspect or embodiment of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, which are:

Figure 1 a schematic sectional side view of an excavation apparatus according to a first embodiment of the present invention;

Figure 2 a view from above of a rotor of the excavation apparatus of Figure 1 ;

Figure 3 a side view of the rotor of Figure 2;

Figure 4 a view from below of a stator of the excavation apparatus of Figure 1 ;

Figure 5 a side view of the stator of Figure 4;

Figure 6 a view from below of an alternative stator of the excavation apparatus of Figure 1 ; and

Figure 7 a side view of the alternative stator of Figure 6.

DETAILED DESCRIPTION OF DRAWINGS

Referring to Figures 1 to 5, there is shown an excavation apparatus comprising an underwater excavation apparatus, generally designated 5, according to a first embodiment of the present invention.

The excavation apparatus 5, such as a controlled flow (underwater) excavation apparatus, comprises a rotor 10 having or comprising one or more rotor blades 11 comprising one or more or a plurality of first (impeller) rotor blades 12 and one or more or a plurality of second (splitter/splitter impeller) rotor blades 14.

Provision of the second rotor blade(s) 14 between adjacent first rotor blades 12 effectively narrows a width of an end of a fluid passage 16 between adjacent first rotor blades 12. This can obviate or mitigate a need to increase a diameter of the rotor 10 if the excavation apparatus 5 is to be used for hard soils, e.g., above 100KPa such as 100 KPa to 400KPa.

The excavation apparatus 5 comprises a stator 15. The stator 15 has or comprises a plurality stator blades 45 comprising first stator blades 46 and (optionally/beneficially) a plurality of second (splitter) stator blades 47.

The excavation apparatus 5 beneficially comprises a single rotor.

The excavation apparatus 5 beneficially comprises a single stator.

The apparatus comprises a housing 20.

The housing 20 comprises or has at least one inlet 25 and at least one or an outlet 30. The first (impeller) rotor blades 12 comprise one or more, i.e., a plurality of primary (impeller) rotor blades.

The second (splitter) rotor blades 14 comprise one or more, i.e., a plurality of secondary or splitter rotor blades.

A/each second rotor blade 14 is provided between adjacent (pairs of) first rotor blades 12.

A leading edge of a/each second rotor blade 14 commences or starts midway along, e.g., 35% to 45% along, a length of a/an adjacent first rotor blade 12, e.g., 38% measured at a hub and 42% measured at the housing 20.

A height of the first rotor blade(s) 12 and/or second rotor blade(s) 14 reduce along a length of the respective blade.

A distance between and/or an area of a flow path between adjacent first and second rotor blades 12, 14 and/or a distance between and/or an area of the flow path between adjacent primary rotor blades and/or between adjacent splitter rotor blades increases along the length of the respective rotor blades 12, 14. (In each case, the length of the respective rotor blade 12, 14 can be measured from the at least one inlet 25 towards the outlet 30).

Such arrangement can be of benefit in providing an excavation apparatus adapted for use in firmer seabed or riverbed conditions which require higher pressure in order to excavate the soil.

The rotor 10 and/or the stator 15 are provided in the housing 20. The housing 20 comprises an axis or longitudinal axis A, the rotor 10 and the stator 15 being arranged coaxially upon or with the axis A.

The rotor 10 is provided proximal the inlet(s) 25. The stator 15 is provided proximal the outlet 30.

The rotor 10 has a rotor rotation axis, which comprises or is coincident with the longitudinal axis A of the housing 20.

The rotor 10 comprises a first body 39. The plurality of first and second rotor blades 12, 14 are provided within the housing 20.

In use, flow of fluid past or across the rotor 10 is at a first angle a from the axis of rotation.

There are excavation and optionally suction modes of the excavation apparatus. In excavation and/or in suction mode fluid can flow from the at least one inlet 25 to the outlet 30 of the excavation apparatus 5.

The rotor rotation axis extends between (a level of) the at least one inlet 25 and the outlet 30. The first body comprises a first cone member.

The first angle a diverges away from the axis A in a direction away from at least one of the at least one inlets 25 and towards the outlet 30.

An apex of the rotor 10 or first cone member faces the inlet 25 or an inlet end of the housing 20.

The plurality of first and/or second rotor blades 12, 14 comprise aerofoil blades, which can be optionally disposed, such as circumferentially disposed, on the first cone member.

The first stator blades 46 comprise one or more, i.e. , a plurality of primary stator blades.

The second stator blades 47 comprise one or more, i.e., a plurality of secondary or splitter blades.

A/each second stator blade 47is provided between an adjacent pair of first stator blades 46.

A leading edge of a/each second stator blade 47 commences or starts midway alone, e.g., 45% to 55% along, a length of an adjacent first stator blade 46, e.g., 48% measured at the hub and 52% measured at the housing 20.

A height of the first and second stator blades 46, 47 can reduce along a length of the respective stator blade 46, 47.

A distance between and/or an area of the flow path between adjacent first and second stator blades 46, 47 and/or a distance between and/or an area of the flow path 49 between adjacent primary stator blades and/or between adjacent splitter stator blades may decrease along the length of the respective stator blades 46, 47. In each case the length of the stator blade 46, 47 can be measured from inlet towards outlet. Such arrangement can be of benefit in creating an excavation apparatus 5 adapted for use in firmer seabed or riverbed conditions which require higher pressure in order to excavate the soil.

Such arrangement can be of benefit in excavation apparatus 5 adapted for use in relatively shallow waters, e.g., as such may allow relatively low profile/height excavation apparatus.

The stator 15 is coaxial with the rotor 10 and the stator is provided between the rotor 10 and the outlet 30.

In use, flow of fluid past or across the stator 15 is at a second angle from the axis of rotation of the rotor 10.

The stator 15 comprises a second body 40, such as a second cone member. The second angle p converges towards the axis A in a direction away from the inlet 25 and towards the outlet 30.

An apex of the stator 15 or second cone member faces the outlet 30.

The plurality of first and second stator blades 46, 47 comprise aerofoil blades, which can be disposed on the second cone member.

The first angle a can be selected from either: in the range of 55° to 75°, or 65°.

The second angle can be selected from in the range of 55° to 75°, or 65°.

The at least one inlet 25 is provided on or at a side or sides 26 (or alternatively on or at an end) of the housing 20.

The at least one inlet 25 is provided around, e.g., circumferentially or peripherally around a/the side of the housing 20.

The housing 20 comprises longitudinal axis A. The housing 20 is symmetrical with respect to the longitudinal axis A.

The one or more inlets 25 are provided inclined and/or offset from or transversely or substantially transversely to the longitudinal axis A.

The one or more inlets 25 are provided perpendicularly or substantially perpendicularly to the longitudinal axis A.

The/each of the one or more inlets 25 are provided non-parallel to the longitudinal axis A of the housing 20.

The/each of the one or more inlets 25 is provided at an angle, e.g., non-zero (0°) angle, e.g., perpendicularly or substantially perpendicularly, to the/each of the one or more outlets 30.

The/each at least one inlet 25 is provided near or adjacent an end 29 of the housing 20.

The/each of the one or more outlets 30 are provided on or at an/another end 31 of the housing 20 such as on and/or parallel to a/the longitudinal axis A.

The apparatus 5 is adapted to provide an inclined or horizontal or substantially horizontal or a non-vertical or substantially non-vertical flow of fluid/water into the housing 20, in use, such as in a first or excavation mode of operation.

The fluid/water flow into the housing 20 is inclined at a converging angle to the longitudinal axis A of the housing 20.

The excavation apparatus 5 is adapted to provide a coaxial or substantially coaxial or vertical or substantially vertical or a non-horizontal or substantially nonhorizontal flow of fluid/water out of or from the housing 20, in use. The excavation apparatus 5 is adapted to provide and/or direct, in use, a flow of fluid/water, e.g., at a pressure of 200 KPa to 400 KPa and/or a volume flow of 0.5m ³ /s to 4m ³ /s.

There is provided a fluid flow path F or passage extending from the/each at least one inlet 25 to the outlet 30. The at least one rotor 10 and/or the at least one stator 15 is provided in the flow path F.

The fluid flow path F comprises a first (inlet) section, which extends from the at least one inlet 25.

The fluid flow path F comprises a second (rotor) section, which contains at least part of the rotor 10. Said second section diverges away from the longitudinal axis A of the housing 20.

The fluid flow path F comprises a third (stator) section, which contains at least part of the stator 15. Said third section converges towards the longitudinal axis A of the housing 20.

The fluid flow path F comprises a fourth (outlet) section, which extends to the at least one or the outlet 30.

The fluid flow path F comprises a first inlet portion/first portion Fi which is provided at or adjacent the/each at least one inlet 25. Said first inlet portion/first portion Fi advantageously converges towards the longitudinal axis A of the housing 20, e.g., at a non-zero angle, e.g., between 0° and 90°, 45°, and 90°, or at 90°. Said first inlet portion/first portion Fi advantageously is substantially horizontal, in use, and/or perpendicular to the longitudinal axis of the housing 20 and/or said first inlet portion/first portion Fi is substantially straight.

The fluid flow path F comprises a second inlet portion/second portion F2, which extends or continues from the first inlet portion/first portion Fi. Said second inlet portion/second portion F2 is advantageously curved, bent or arcuate and convex relative to the longitudinal axis A of the housing 20.

The fluid flow path F comprises a rotor portion/third portion F3, which extends or continues from the inlet section/second inlet portion/second portion F2. Said rotor portion/third portion F3 is advantageously substantially straight, coincident with or contains at least a part or parts of the rotor 10, and diverges away from the longitudinal axis A of the housing 120, e.g., in a flow direction from the inlet 25 to the outlet 39, e.g., at an angle a of 55° to 75°, e.g., 65°.

The fluid flow path F comprises a further or intermediate portion/fourth portion F4, which extends or continues from the first rotor portion/third portion F3. Said further or intermediate portion/fourth portion F4 is advantageously curved, bent or arcuate, and concave relative to the longitudinal axis A of the housing 20.

The fluid flow path F comprises a stator portion/fifth portion F5 which extends or continues from the further or intermediate portion/fourth portion F4. Said first stator portion/fifth portion F5 is advantageously substantially straight, coincident with or contains at least part or parts of the stator 15, and converges towards the longitudinal axis A of the housing 20, e.g., in a flow direction from the inlet 25 to the outlet 30, e.g., at an angle p of 55° to 75°, e.g., 65°. Such arrangement can be of benefit for excavation apparatus adapted for use in relatively shallow waters, e.g., as such may allow for a relatively low profile/height excavation apparatus.

The fluid flow path F comprises a first outlet portion/sixth portion Fe, which extends or continues from the stator portion/fifth portion F5. Said first outlet portion/sixth portion Fe is advantageously curved, bent or arcuate, and convex relative to the longitudinal axis A of the housing 20.

The fluid flow path F comprises a second outlet portion/seventh portion F7, which extends or continues from the first outlet/sixth portion Fe. Said second outlet portion/seventh portion F? is provided at or adjacent the outlet 30. Said second outlet portion/seventh portion F? is advantageously substantially vertical, in use, parallel to the longitudinal axis A of the housing 20, and substantially straight.

In a first mode of operation, which comprises an excavation mode, the outlet 30 faces an area to be excavated, and in such mode the inlet 25 is provided above, i.e., directly above, the outlet 30.

In a second mode of operation, which comprises a suction mode, the inlet25 is proximal an area which has been excavated and/or requires to be cleared, and in such mode the inlet 25 is provided below, i.e., directly below, the outlet 30.

An inside of the housing 20 converges from the at least one inlet 25 towards the rotor 10.

The inside of the housing 20 diverges from the inlet end of the rotor 10 towards the outlet end of the rotor 10.

The inside of the housing 20 converges from the stator 15 towards the outlet 30.

The outlet 30 is substantially coaxial with the rotor 10 and the stator 15 and the axis A of the housing 20.

The housing 20 is circumferentially/rotationally symmetrical about the axis A of the housing 20. The excavation apparatus 5 comprises means or an arrangement (not shown) for dampening reactive torque on the excavation apparatus 5 caused by rotation of the rotor 10, in use.

The excavation apparatus 5 and/or the at least one rotor 10 beneficially comprise a single rotor.

The torque dampening means beneficially does not comprise a second rotor, such as a second rotor counter-rotating to the at least one (single) rotor.

The excavation apparatus 5 and/or the at least one stator 15 beneficially comprise a single stator.

The housing 20 comprises a hollow body.

The rotor 10 and the stator 15 are provided in the housing 20. The housing 20 comprises axis A. The rotor 10 and the stator 15 are arranged coaxially, such as upon the axis A. The housing 20 is provided upon the axis A. The rotor 15 is provided proximal the at least one inlet 25 and the stator 15 is provided proximal the outlet 30.

The rotor 10 comprises first body 39, such as a first cone body, and the plurality of first and second rotor blades 12, 14 are disposed on the first body 39.

The stator 15 comprises a second body 40, such as a second cone body, and the plurality of first and second stator blades 46, 47 are disposed on the second body 40.

The torque dampening means can comprise or include anti-rotation vanes.

The excavation apparatus may comprise a motor 70 for driving the rotor 10. The rotor is provided (longitudinally) between the at least one inlet 25 and the at least one outlet 30.

Referring to Figures 6 and 7, there is shown an alternative stator 15a for use in the excavation apparatus 5. The stator 15a is similar in many respects to the stator 15, like parts being denoted by like integers, but suffixed “a”.

The present invention provides an excavation system or tool 205, such as an underwater system or tool, comprising at least one excavation apparatus 5 as hereinbefore described.

The present invention provides a method of excavation, such as a method of underwater excavation, the method comprising: providing at least one excavation apparatus 5 as hereinbefore described; and excavating a location, such as an underwater location, using said excavation apparatus.

It will be appreciated that the embodiment of the present invention hereinbefore described is given by way of example only, and is not meant to be limiting of the invention in any way. It will be particularly appreciated that the arrangement of the at least one inlet is adapted and/or designed to provide and/or encourage fluid flow ingress from a side or sides rather than an end/top of the housing. This is of particular benefit when operating at or near a surface of a body of fluid/water and/or in relatively shallow depths, e.g. so as to reduce any vortex effects at the inlet. Another key feature of such an excavation apparatus, particularly for such use, is a relatively large stator path converging angle relative to the longitudinal axis A, as such reduces the required height of the housing. To achieve the shorter, low profile, housing height, the provision of the secondary/splitter blades is of particular benefit. As shown in Figure 1 , height Ai minus A2 is greater than height Ci minus C2. A second rotor blade(s) 14 start at B. Also, first rotor blade(s) 12 and second rotor blades 14 end at position C.

Referring to Figure 1 , a first stator blade(s) 46 start at position D and end at position F. Also, second stator blade(s) 47 start at position E and end at position F. As shown in Figure 2, a distance between first rotor blades 12 increases along a length of the first rotor blades 12 - see 1a, 1b to 2a, 2b - i.e., 1a to 2a is less than 1b to 2b. Also, distance 3a to 4a is less than distance 3b to 4b.