Patent Description:
Ejector devices are known for the pumping of fluids, e.g. liquids or gases. Operation of ejector devices is based upon the venturi principle. Velocity of a relatively high pressure fluid (called the "motive" fluid) along a channel provides a suction effect on a relatively low pressure fluid (called the "entrained" or "suction" fluid). The suction fluid is entrained into the main flow through the channel and ejected from the ejector device as a "discharge" fluid. Examples of such ejector devices which use a motive liquid to pressurise a gas may be called a jet pump, a liquid jet compressor or a Venturi pump.

Ejector devices have an advantage over many conventional mechanical pumps in that they can have substantially no moving parts, so may therefore provide a longer service life in many practical applications. Ejectors have been used with a combination of different fluids over the years and can be found in a multitude of industries.

<FIG> shows an example of an ejector device described in <CIT>. The ejector device <NUM> has a motive fluid inlet portion <NUM> through which a motive fluid can enter the device <NUM>. The motive fluid may for example be pumped by a pump (not shown) into and through the motive fluid inlet or injector portion <NUM>. The velocity of the motive fluid increases as it passes through a conical nozzle portion <NUM> of the device <NUM> before being injected through an outlet aperture <NUM> of the nozzle portion <NUM> at an apex thereof into an inlet aperture <NUM> of a diffuser portion <NUM>. The diffuser portion <NUM> provides a fluid conduit in the form of a Venturi tube, in which, passing from the inlet aperture <NUM> of the diffuser portion <NUM> towards an outlet aperture <NUM> thereof, a diameter of the conduit initially decreases along a first length of the diffuser portion <NUM> to a diameter less than that of the inlet aperture <NUM>, then remains at that reduced diameter for a short distance, and then along a second length of the diffuser portion <NUM> the diameter of the conduit increases towards the outlet aperture <NUM> of the diffuser portion <NUM>.

The outlet aperture <NUM> of the nozzle portion <NUM> and the inlet aperture <NUM> of the diffuser portion <NUM> are in fluid communication with a suction fluid inlet portion <NUM> of the device <NUM>. As a flow of motive fluid flows out from the outlet aperture <NUM> of the nozzle portion <NUM> and into the diffuser portion <NUM>, the motive and suction fluids are mixed, and this results in a transfer of momentum and thus kinetic energy from the motive fluid to the suction fluid. This is accompanied by a reduction in the flow velocity of the combined fluids and an increase in the pressure of the suction fluid phase. It is to be noted that this is a reverse process to that occurring in the nozzle portion <NUM> where an increase in motive fluid velocity occurs, thereby reducing a pressure of the motive fluid as it exits the nozzle portion <NUM> through its outlet aperture <NUM>.

In practical applications of ejectors of the type shown in <FIG>, the motive fluid may be a liquid or a gas or any other suitable fluid, and the suction fluid may independently also be a liquid or a gas or any other suitable fluid. However, in many particularly useful applications such ejector devices may be used to pressurise and thus pump gaseous fluids, in which case the motive fluid may typically be a liquid phase and the suction fluid may be the gaseous phase to be pumped.

<FIG> shows an example of an ejector device with a single channel, where a "channel" is a combination of a nozzle and a diffuser. An ejector device may have multiple channels. An example of a multichannel ejector device is described in <CIT>.

Ejector devices may be deployed for extended periods, such as a period of years, or tens of years. At some point during deployment it may be necessary to change the internal components of an ejector device to adapt to different operating conditions. For example, consider an ejector device is deployed to pump gas or oil from a well. The pressure of the well changes over a period of time. This may require a different nozzle and/or diffuser to allow the ejector to function at required parameters. <CIT> describes an ejector with a nozzle and a diffuser which can each, individually, be replaced.

<CIT> describes an ejector with a housing in tubular form. <CIT> describes an ejector pump. <CIT> describes a vacuum ejector with a multinozzle drive stage and booster. <CIT> describes a liquid-gas ejector. <CIT> describes an ejector condenser. <CIT> describes an ejector assembly and vacuum pump. <CIT> describes an ejector condenser with a plurality of columns.

There is provided an ejector device according to claim <NUM>.

The nozzle and diffuser assembly may be called a nozzle-diffuser assembly or a nozzle-diffuser channel.

Optionally, the connecting structure is configured to concentrically align the nozzle and the diffuser about a longitudinal axis of the nozzle and diffuser assembly.

Optionally, the connecting structure is a hollow tubular structure.

Optionally, the connecting structure comprises a plurality of apertures around a perimeter of the connecting structure.

Optionally, the connecting structure comprises at least one of: (i) a collar free of apertures at an upstream end of the connecting structure; (ii) a collar free of apertures at a downstream end of the connecting structure. The collars provide strength to the connecting structure. The collars can help to simplify assembly of an overall nozzle and diffuser assembly. This is particularly useful if the connecting structure is manufactured as a separate element to the nozzle and/or the diffuser, as the collar at the upstream end can be aligned with, and connected to, the nozzle and/or the collar at the downstream end can be aligned with, and connected to, the diffuser.

Optionally, the diffuser has an inlet with an inlet cross sectional area and the plurality of apertures have a combined aperture cross sectional area, and wherein the combined aperture cross sectional area is equal to, or greater than, the inlet cross sectional area.

Optionally, the nozzle and diffuser assembly is removable as a single assembly from one end of the housing.

Optionally, the fluid outlet is located at a downstream end of the housing and the nozzle and diffuser assembly is removable from the downstream end of the housing.

Optionally, the ejector device comprises at least one sealing element to form a fluid-tight seal between the nozzle and diffuser assembly and an interior of the housing.

Optionally, the at least one sealing element is carried by the nozzle and diffuser assembly.

Optionally, a downstream end of the nozzle and diffuser assembly comprises a flange which is configured to fit within a recess at a downstream end of the housing.

Optionally, a downstream end of the housing has a downstream housing end face and wherein, when the nozzle and diffuser assembly is fitted within the housing, a downstream end face of the nozzle and diffuser assembly is configured to substantially align with the downstream housing end face.

The first and second supporting walls may substantially seal a volume between the supporting walls, such that fluid entering the volume between the walls via the suction fluid inlet is prevented from passing beyond the walls unless it is drawn into the diffuser via the apertures in the connecting structure.

Optionally, the housing has an unobstructed interior volume between the first supporting wall and the second supporting wall. The provision of supporting walls, rather than larger supporting structures which extend axially along the housing, has an advantage of reducing an amount of material and therefore weight and cost of the ejector device. Providing an unobstructed interior volume between the supporting walls can help to reduce pressure loss between the suction fluid inlet and the diffusers. Providing an unobstructed interior volume between the supporting walls can also allow easier cleaning of the interior volume of the housing.

Optionally, the ejector device comprises a plate which is configured to fit across a respective downstream end of the plurality of nozzle and diffuser assemblies.

Optionally, a downstream end of the housing has a downstream housing end face and wherein, when the plate is fitted to the device, a downstream end face of the plate is configured to substantially align with the downstream housing end face.

Optionally, the housing comprises a first housing part and a second housing part, the first housing part configured to connect with the second housing part at a joint to form a fluid-tight housing, wherein the second supporting wall is located at, or upstream of, the joint between the first housing part and the second housing part.

The suction fluid inlet may be axially aligned with apertures of the connecting structure (or from apertures of the plurality of connecting structures) such that there is a direct radial path between the suction fluid inlet and the apertures. Optionally, the suction fluid inlet is axially offset from apertures of the connecting structure (or from apertures of the plurality of connecting structures where the housing is configured to receive a plurality of the nozzle and diffuser assemblies). This can help improve uniformity of distribution of fluid around the connecting structure or structures. This in turn can improve an efficiency of the ejector device.

A centreline of the suction fluid inlet may be axially offset from apertures of the connecting structure by at least or substantially <NUM> diameters of the suction fluid inlet, or by at least or substantially one diameter of the suction fluid inlet, or by at least or substantially two diameters of the suction fluid inlet, or by at least or substantially three diameters of the suction fluid inlet.

An aspect provides a method of maintaining an ejector device according to claim <NUM>.

Optionally, the method comprises one of:.

An advantage of this arrangement is that the nozzle can accurately aligned with respect to the diffuser. Alignment of the nozzle with respect to the diffuser is determined during manufacture of the nozzle and diffuser assembly. The term "alignment" refers to the nozzle and the diffuser being aligned concentrically about the same longitudinal axis. This contrasts with prior art ejectors where the nozzle and the diffuser and independently supported by different parts of the ejector, or ejector housing. This means that in prior art systems alignment of the nozzle with respect to the diffuser is determined by features of the housing (e.g. shoulders) in which the nozzle and the diffuser are housed or supported. These features can become deformed or damaged. This can also avoid the need to perform alignment checks on the ejector after installing the nozzle and diffuser assembly.

An advantage of this arrangement is that a nozzle and diffuser channel of an ejector system can be inspected, maintained or replaced in a reduced time. This reduces time that the ejector is out of operation, and reduces cost of maintenance.

An advantage of this arrangement is that a nozzle and diffuser channel of an ejector system can be inspected, maintained or replaced by removing a piece of the pipework at a single end of the ejector. For example, by removing pipework at just the downstream end of the ejector. This reduces the number of connections that need to be broken, remade and re-checked for fidelity. During this period the housing remains in situ.

An advantage of this arrangement is that only one end of the ejector device needs to be provided with features to allow access to the interior of the housing. For example, only one end of the ejector device requires a flanged-connection. Advantageously, only a downstream end of the ejector device is provided with a connection to allow access. Optionally, the connecting structure cage is configured such that it has minimal pressure drop on the path to the diffuser, whilst providing a strong and rigid connection that maintains the concentricity of the nozzle and the diffuser.

In implementing some embodiments or examples of the invention, the components of the injector portion may be designed with various shapes, configurations and/or orientations which may achieve a particular desirable flow behaviour of generating certain defined components of flow of the motive fluid, as will be discussed further below.

Other objects and advantages may be apparent from the further definitions and descriptions which follow below.

Within the scope of this application it is envisaged and explicitly intended that the various aspects, embodiments, features, examples and alternatives, and in particular any of the variously defined and described individual features thereof, set out in any of the preceding paragraphs, in any part of the following description and/or accompanying drawings, may be taken and implemented independently or in any combination. For example, features described in connection with one particular embodiment or aspect are to be considered as applicable to and utilisable in all embodiments of all aspects, unless expressly stated otherwise or such features are, in such combinations, incompatible.

Embodiments of the present invention in its various aspects will now be described, by way of example only, with reference to the accompanying drawings, in which:.

<FIG> show an example of a single-channel ejector device <NUM>. The ejector device <NUM> comprises a housing <NUM> and a nozzle-diffuser assembly <NUM>. <FIG> shows the housing <NUM> of the ejector device. <FIG> shows the nozzle-diffuser assembly <NUM>. <FIG> shows the ejector device <NUM> in assembled form, with the nozzle-diffuser assembly <NUM> of <FIG> fitted within the housing <NUM> of <FIG>.

The housing <NUM> comprises a first inlet <NUM>, a second inlet <NUM> and an outlet <NUM>. The first inlet <NUM> will be called a motive inlet or a high pressure inlet. The first inlet <NUM> is configured to receive a high pressure fluid. The first inlet <NUM> is located at a first, upstream, end of the housing <NUM>. The second inlet <NUM> will be called a suction inlet or a low pressure inlet. The second inlet <NUM> is configured to receive a fluid which is typically at a lower pressure than the pressure received at the first inlet <NUM>. The second inlet <NUM> is located part-way along the housing <NUM>. The outlet <NUM> is configured to output a combination of the fluids received via the first inlet <NUM> and the second inlet <NUM>. The outlet <NUM> is located at a second, downstream, end of the housing <NUM>. The housing <NUM> is configured to retain the pressures of the fluids the nozzle-diffuser channel is designed to perform over.

The nozzle-diffuser assembly <NUM> comprises a nozzle <NUM> and a diffuser <NUM> which are connected together by a connecting structure <NUM>. The connection is such that the nozzle-diffuser assembly <NUM> can be inserted, as a single combined assembly, into the housing <NUM> via a single end of the housing <NUM>. The nozzle-diffuser assembly <NUM> can also be removed, as a single combined assembly, from the housing <NUM> via the single end of the housing <NUM>. In <FIG> the nozzle-diffuser assembly <NUM> can be inserted via the outlet <NUM> end of the housing <NUM>. The outlet <NUM> is at a lower pressure than the first inlet <NUM> and therefore it is easier to provide access at the outlet <NUM>. For example, the dimensions of flanges, and the fittings to secure the flanges together, at the outlet <NUM> are smaller than would be required at the first inlet <NUM>.

<FIG> shows a cross section through the housing <NUM> and the nozzle-diffuser assembly <NUM>. An internal wall <NUM> of the housing <NUM> defines a bore. Typically the bore has a circular cross-sectional shape. The nozzle-diffuser assembly <NUM> has an outer diameter which is slightly smaller than a diameter of the internal wall <NUM>. The internal wall <NUM> of the housing <NUM> may have a substantially constant diameter along its length (i.e. the internal wall is cylindrical). Alternatively, the internal wall <NUM> of the housing <NUM> may have a smaller diameter nearer the upstream end (e.g. the internal wall <NUM> has a tapered shape or the internal wall <NUM> has a collar of smaller diameter). This can allow the nozzle-diffuser assembly <NUM> to move into position with reduced friction between the outer surface of the nozzle-diffuser assembly <NUM> and the internal wall <NUM>. This can help to reduce wear or damage to any seals, such as O-rings <NUM>, <NUM>. The nozzle-diffuser assembly <NUM> carries O-rings <NUM>, <NUM> to form a seal against the internal wall <NUM>. In this example the O-rings <NUM>, <NUM> are carried by the nozzle-diffuser assembly <NUM>. This has an advantage of allowing the O-rings to be inspected and/or replaced when the nozzle-diffuser assembly <NUM> is removed from the housing <NUM>. In another example the O-rings <NUM>, <NUM> may be located within the housing <NUM>.

The nozzle <NUM> has a nozzle channel <NUM>. The nozzle channel <NUM> is aligned with a longitudinal axis of the nozzle-diffuser assembly <NUM>. A width/diameter of the nozzle channel <NUM> reduces towards the downstream end (tip) of the nozzle <NUM>. This shape of the nozzle channel <NUM> causes fluid to increase in velocity as it passes towards the downstream end of the nozzle. The increase in velocity is accompanied by a reduction in pressure. The outer surface of the nozzle <NUM> also reduces in width/diameter towards the downstream end of the nozzle. This provides a surface over which suction fluid <NUM> can flow.

The diffuser <NUM> has a diffuser channel <NUM>. The diffuser channel <NUM> varies in width/diameter between an upstream end and a downstream end of the diffuser <NUM>. In <FIG> the diffuser channel <NUM> comprises: a first portion 171A in which the diffuser channel <NUM> reduces in width/diameter (i.e. a converging portion); a second portion 171B in which the diffuser channel <NUM> has a substantially constant width/diameter; and a third portion 171C in which the diffuser channel <NUM> increases in width/diameter (i.e. a diverging portion). Other arrangements are possible. For example, the relative axial lengths of the first, second and third portions 171A, 171B, 171C can be different to the diffuser shown here. The narrowest diameter of the diffuser channel <NUM> may be different to the diffuser shown here.

The connecting structure <NUM> connects the nozzle <NUM> to the diffuser <NUM>. In <FIG> the connecting structure <NUM> is a hollow tubular structure. The connecting structure <NUM> has a plurality of apertures, or orifices <NUM>, configured to allow fluid to pass into the interior of the connecting structure <NUM>. The connecting structure <NUM> resembles a cage. In <FIG> the apertures <NUM> are distributed around the connecting structure. Narrow struts <NUM> are provided between adjacent apertures <NUM>. The tubular structure <NUM> connects to the nozzle <NUM> in the region where the outer surface of the nozzle <NUM> begins to taper. The tubular structure <NUM> connects to the diffuser <NUM> at the upstream end of the diffuser. The outer diameter of the connecting structure <NUM> is equal, or substantially equal, to the outer diameter of the nozzle <NUM> and the diffuser <NUM>. In this way, the outer diameter of the nozzle-diffuser assembly is substantially equal along its length. The connecting structure <NUM> axially spaces the outer surface of the nozzle <NUM> from the diffuser channel <NUM>. In the example shown in <FIG> the downstream end of the nozzle <NUM> is substantially aligned with the upstream end of the diffuser <NUM>, but other arrangements are possible. The connecting structure <NUM> defines a region <NUM> between the connecting structure <NUM> and the outer surface of the nozzle <NUM>.

In <FIG> the hollow tubular structure <NUM> has a cylindrical wall with apertures <NUM> in the wall. The hollow tubular structure <NUM> has a cylindrical collar <NUM> at an upstream end and a cylindrical collar <NUM> at a downstream end. The collars <NUM>, <NUM> are regions which are free of apertures <NUM>, i.e. regions where there are no apertures <NUM>. The collars <NUM>, <NUM> increase strength of the connecting structure <NUM>. The collars <NUM>, <NUM> can also provide regions for connecting the connecting structure <NUM> to the nozzle <NUM> and diffuser <NUM>. For example, the collar can provide a surface to weld to the nozzle <NUM>. The collar <NUM> can surround part of the nozzle <NUM> when the connecting structure is assembled to the nozzle. The connection between the connecting structure <NUM> and the nozzle <NUM> can be achieved by pressing together with a press or interference fit, welding or some other form of connection, such as a screwed fit. During assembly, collar region <NUM> at the upstream end of the tubular structure <NUM> can be aligned with and connected to a cylindrical downstream end of the nozzle <NUM>. During assembly, collar region <NUM> at the downstream end of the tubular structure <NUM> can be aligned with and connected to a cylindrical upstream end of the diffuser <NUM>. The connection between the connecting structure <NUM> and the diffuser <NUM> can be achieved by pressing together with a press or interference fit, welding or some other form of connection, such as a screwed fit. The connecting structure can be manufactured as a separate element to the nozzle <NUM> and/or the diffuser <NUM> and then assembled. The collar(s) allow the connecting structure to be aligned with, and connected to, the nozzle <NUM> and/or the diffuser <NUM> during assembly. The axial length of each of the collars <NUM>, <NUM> can be different to what is shown in <FIG>. For example, the nozzle-diffuser assembly <NUM> shown in <FIG> has longer collars <NUM>, <NUM>.

<FIG> shows, in simple terms, fluid flows in the ejector device. It will be understood that the precise path of the fluid flows are more complex than it is possible to show here. There is a flow <NUM> of motive fluid from the first inlet <NUM>, through the nozzle channel <NUM> and into the diffuser channel <NUM>. The shape of the nozzle channel <NUM> causes a jet of motive fluid to flow from the downstream tip of the nozzle <NUM>. This creates a low pressure region near the tip of the nozzle <NUM>. The low pressure region serves to entrain suction fluid via the second inlet <NUM>. There is a flow of suction fluid from the second inlet <NUM> which passes through apertures <NUM> of the connecting structure <NUM>, into the region <NUM> between the connecting structure <NUM> and the outer surface of the nozzle <NUM>. Suction fluid is guided by the outer surface of the nozzle <NUM> towards the low pressure region at the inlet of the diffuser channel <NUM>. The motive fluid and suction fluid combine in the diffuser <NUM>. The shape of the diffuser channel <NUM> serves to combine the fluid flows. For the suction fluid, the diffuser channel <NUM> is narrowing and therefore causes the suction fluid to speed up. For the motive fluid, the diffuser channel <NUM> is wider than the tip of the nozzle <NUM> and therefore causes the motive fluid to slow down. A combined fluid flow exits the outlet <NUM> of the ejector device. A more detailed description of the operation of a nozzle and a diffuser of an ejector device is available in, for example, <CIT>.

Typically, the ejector <NUM> is fitted within an overall fluid flow system of pipes or conduits. Each end of the ejector device <NUM> has a suitable connector for connecting to a fluid conduit or other fitting or device. One type of connector is a flange. A pair of fittings are connected together by aligning their respective flanges together and securing the flanges together by bolts or other fixings. Other types of connector are possible, suitable for the mechanical design conditions of system the device is connected to.

In <FIG> the downstream (outlet end) of the housing <NUM> has a shoulder <NUM>. The shoulder <NUM> is a radially-extending surface, orthogonal to the longitudinal axis of the housing <NUM>. The housing continues downstream of the shoulder <NUM>, with a collar <NUM> having a radial outer surface <NUM> on the downstream end face. The collar <NUM> and shoulder <NUM> together define a recess for receiving a downstream end of the nozzle-diffuser assembly <NUM>. The nozzle-diffuser assembly <NUM> has a flange <NUM> which is configured to locate against the shoulder <NUM> of the housing <NUM>. <FIG> shows the flange <NUM> of the nozzle-diffuser assembly <NUM> located against the shoulder <NUM>. The flange <NUM> has a diameter which is less than the internal diameter of the collar <NUM>. The flange <NUM> has an axial length which is substantially equal to the axial distance between the shoulder <NUM> and outer surface <NUM> of the housing. This allows an outer surface <NUM> of the flange <NUM> to lie in the same plane as the radial surface <NUM> of the housing. A flange (or other fitting) can be pressed against the flange <NUM> and the outer surface <NUM> of the housing. This provides a surface to connect against, and also securely retains the nozzle-diffuser assembly <NUM> within the housing <NUM>.

The arrangement described above provides an end stop for axial movement of the nozzle-diffuser assembly <NUM>. The nozzle-diffuser assembly <NUM> can be inserted into the housing <NUM> until the flange <NUM> rests against the shoulder <NUM> of the housing <NUM>.

In <FIG>, the upstream end of the nozzle-diffuser assembly <NUM> has an annular radial surface <NUM>. An upstream end of the housing <NUM> has a radial end surface <NUM>. It will be understood that differently shaped surfaces could be provided at the upstream end, such as inclined surfaces.

In the example shown in <FIG> axial movement of the nozzle-diffuser assembly <NUM> is constrained at the upstream end (by radial surface <NUM>) and at the downstream end (by shoulder <NUM>). In other examples, the nozzle-diffuser assembly <NUM> may be configured to allow for thermal expansion at the upstream end. For example, there can be an axial gap between the upstream end of the nozzle-diffuser assembly <NUM> and a wall of the housing <NUM>. This can have an advantage of allowing for thermal expansion.

Removal of the nozzle-diffuser assembly <NUM> will now be described. In <FIG> a fitting <NUM> is connected to the downstream end of the housing <NUM>. Firstly, the fitting <NUM> is removed from the ejector, such as disconnecting a flange connected to the flange at the downstream end of the housing <NUM>. This provides access to the interior of the housing <NUM>. The nozzle-diffuser assembly <NUM> can then be withdrawn, as a single assembly, from the interior of the housing. Once the nozzle-diffuser assembly <NUM> has been withdrawn from the housing, it can be inspected (e.g. for routine maintenance, cleaning etc.) and re-inserted into the housing. Alternatively, the nozzle-diffuser assembly <NUM> which has been withdrawn from the housing may be replaced with a different nozzle-diffuser assembly <NUM>.

The different nozzle-diffuser assembly <NUM> may have one or more of: a different nozzle <NUM> (e.g. a differently shaped or dimensioned nozzle channel <NUM>, a different cross-sectional outlet size at the nozzle tip, a different cross-sectional outlet size at the nozzle inlet, a differently shaped or dimensioned exterior of the nozzle); a different diffuser <NUM> (e.g. differently shaped or dimensioned diffuser channel <NUM>; different relative dimensions between the portions 171A, 171B, 171C of the diffuser channel); a different spacing between the nozzle and the diffuser. After inserting a nozzle-diffuser assembly <NUM> into the housing, the fitting is reconnected to the flange at the downstream end of the housing.

The nozzle-diffuser assembly <NUM> may be provided with one or more features to ease withdrawal from the housing. Options include: a lip or ridge that can be gripped with a tool; threaded bores that allow a tool to connect to, and withdraw, the nozzle-diffuser assembly <NUM>.

<FIG> shows the connecting structure <NUM> in more detail. The outer surface <NUM> of the nozzle <NUM> is visible inside the connecting structure <NUM>. In this example the apertures <NUM> have a generally racetrack shape. The apertures <NUM> are configured to minimise pressure drop of the fluid from the suction inlet <NUM>. This can be achieved by providing a total cross section of all the apertures <NUM> equal to, or greater than, the cross sectional area of the inlet (i.e. upstream end) of the diffuser <NUM>. As an example, the number of apertures per connecting structure <NUM> may be between six and eight, or between six and ten. Other numbers of apertures are possible. The struts <NUM> provide structural support and maintain structural integrity. For example, the struts <NUM> are configured to maintain alignment of the nozzle <NUM> with respect to the diffuser <NUM> during use. The struts <NUM> are configured to maintain alignment of the nozzle <NUM> with respect to the diffuser <NUM> (i.e. withstand mechanical deformation) during the forces encountered while the nozzle-diffuser assembly <NUM> is inserted within and/or removed from the housing.

An upstream end of the connecting structure <NUM> is connected the nozzle <NUM>. The connection can be achieved by pressing together with a press or interference fit, welding or some other form of connection, such as a screwed fit. Another type of connection may be used. A combination of connection types may be used. A downstream end of the connecting structure <NUM> is connected to the diffuser <NUM>. The connection can be achieved by pressing together with a press or interference fit, welding or some other form of connection, such as a screwed fit. Another type of connection may be used. A combination of connection types may be used.

There are various options for manufacturing and assembling the nozzle-diffuser assembly <NUM>. One option is to separately form the nozzle <NUM>, the diffuser <NUM> and the connecting structure <NUM> and then to assemble these items together. Another option is form two of these as a single item and then assemble to the remaining item (e.g. form the diffuser and the connecting structure as a single item and assemble to the nozzle). Another option is to form the nozzle <NUM>, the diffuser <NUM> and the connecting structure <NUM> as a single integrated item.

In <FIG> the housing <NUM> has a single suction inlet <NUM>. <FIG> show two alternative arrangements. In <FIG> the housing <NUM> has a first (motive) inlet <NUM>, an outlet <NUM> and a plurality of second (suction) inlets <NUM>. Each suction inlet <NUM> is defined by a discrete conduit extending outwardly from the housing <NUM>. The total number of suction inlets may be more than two. In <FIG> the housing <NUM> has a first (motive) inlet <NUM>, an outlet <NUM> and a plurality of second (suction) inlets <NUM>. The suction inlets <NUM> are provided as apertures in the wall of the housing <NUM>. A distribution chamber (not shown) may surround the plurality of suction inlets <NUM> and connect to a main suction inlet.

<FIG> shows an example of a multi-channel ejector device <NUM>. The ejector device <NUM> comprises a housing <NUM> and a plurality of nozzle-diffuser assemblies <NUM>. <FIG> shows the plurality of nozzle-diffuser assemblies <NUM> fitted within the housing <NUM>.

The housing <NUM> is formed as two housing parts: 410A, 410B. Housing parts 410A, 410B are connected together at a joint or connection 410C. Housing part 410B may be removed from housing part 410A to allow access to the nozzle-diffuser assemblies <NUM>. The connection between the housing parts 410A, 410B may be implemented as a pair of flanges and fixings, or by some other type of connection which allows the housing parts to be removed from one another. The joint between the housing parts 410A, 410B is capable of forming a fluid-tight seal and may comprise one or more sealing elements. The joint between the housing parts 410A, 410B is provided at the downstream end of the housing.

The housing <NUM> comprises a first inlet <NUM>, a second inlet <NUM> and an outlet <NUM>. The first (motive) inlet <NUM> is configured to receive a high pressure fluid. The first inlet <NUM> is located at a first, upstream, end of the housing <NUM>. The second (suction) inlet <NUM> is configured to receive a fluid which is typically at a lower pressure than the pressure received at the first inlet <NUM>. The second inlet <NUM> is located part-way along the housing <NUM>. The outlet <NUM> is configured to output a combination of the fluids received via the first inlet <NUM> and the second inlet <NUM>. The outlet <NUM> is located at a second, downstream, end of the housing <NUM>.

The plurality of nozzle-diffuser assemblies <NUM> are supported within the housing by a pair of supporting walls <NUM>, <NUM>. A first supporting wall <NUM> is provided near the upstream end of the first housing part 410A and a second supporting wall <NUM> is provided near the downstream end of the first housing part 410A. Each of the supporting walls <NUM>, <NUM> has a plurality of bores for receiving the nozzle-diffuser assemblies <NUM>. A nozzle-diffuser assembly <NUM> is supported by a bore in the supporting wall <NUM> and by a bore in the supporting wall <NUM>. The bores in the supporting wall <NUM> are shaped to form an end stop. In the example of <FIG> the wall <NUM> has a radial end surface or collar <NUM>. The surface <NUM> serves as an end stop to limit axial movement of the nozzle-diffuser assembly <NUM> when it is inserted within the housing <NUM>. The upstream end of the nozzle-diffuser assembly <NUM> has an annular radial surface to fit against the end stop. It will be understood that this end stop function could be achieved with differently shaped surface, such as an inclined surface.

In the example of <FIG> the housing <NUM> has an unobstructed interior volume between the first supporting wall <NUM> and the second supporting wall <NUM>. That is, there is no other supporting structure for the nozzle-diffuser assemblies <NUM>. Only the nozzle-diffuser assemblies <NUM> are positioned within the volume between the supporting walls <NUM>, <NUM>. The provision of supporting walls <NUM>, <NUM>, rather than larger supporting structures which extend axially along the housing, has an advantage of reducing an amount of material and therefore weight and cost of the ejector device <NUM>. As the nozzle <NUM> and diffuser <NUM> of each nozzle-diffuser assembly <NUM> are connected into one integrated assembly, there is no need to provide a longer axial support for the nozzle or the diffuser. Providing an unobstructed interior volume between the supporting walls <NUM>, <NUM> can help to reduce pressure loss between the suction inlet <NUM> and the diffusers <NUM>.

The housing <NUM> can be provided with a drain port <NUM>. The drain port <NUM> is closed by a closure device such as a plug, stopper or tap. The drain port <NUM> can be opened during maintenance or servicing to allow the interior volume of the housing <NUM> to be drained and cleaned. Providing an unobstructed interior volume between the supporting walls <NUM>, <NUM> makes it easier to clean the interior volume. By contrast, if each diffuser were supported in a longer axial slot it would be more difficult to clean the interior volume.

The first housing part 410A increases in width/diameter downstream of the first inlet <NUM>.

This provides a diverging chamber <NUM> to distribute the incoming fluid to the respective upstream ends of the plurality of nozzle-diffuser assemblies <NUM>. The central portion of the housing <NUM> has a substantially constant width/diameter. The second housing part 410B decreases in width/diameter downstream of the connection 410C. This provides a converging chamber <NUM> which helps to converge the flows from the plurality of nozzle-diffuser assemblies <NUM>.

Each of the plurality of nozzle-diffuser assemblies <NUM> is similar to the nozzle-diffuser assembly <NUM>. Each nozzle-diffuser assembly <NUM> comprises a nozzle <NUM> and a diffuser <NUM> which are connected together by a connecting structure <NUM>. Each of the nozzle-diffuser assemblies <NUM> can be inserted, as a single combined assembly, into the housing part 410A via the downstream end of the housing part 410A.

Each of the nozzle-diffuser assemblies <NUM> has an outer diameter which is slightly smaller than a diameter of the bore in the supporting walls <NUM>, <NUM>. This allows the nozzle-diffuser assembly <NUM> to slide into position. The nozzle-diffuser assembly <NUM> carries O-rings to form a seal against the supporting walls <NUM>, <NUM>.

The connecting structure <NUM> connects the nozzle <NUM> to the diffuser <NUM>. The connecting structure <NUM> has a plurality of apertures configured to allow fluid to pass into the interior of the connecting structure <NUM>. The connecting structure <NUM> resembles a cage. In use, fluid flows via the suction <NUM> into the region around the plurality of nozzle-diffuser assemblies <NUM>. Fluid from the suction inlet <NUM> is distributed between the plurality of nozzle-diffuser assemblies <NUM> and enters the connecting structures of the nozzle-diffuser assemblies <NUM>. The fluid paths shown in <FIG> are illustrative. Within the nozzle-diffuser assemblies <NUM>, the process is the same as described above for the nozzle-diffuser assembly <NUM> and will not be described further. Combined fluid (i.e. motive fluid and suction fluid) is output from the downstream ends of the nozzle-diffuser assemblies <NUM> and converged by the housing before flowing out of the outlet <NUM>.

In <FIG> it will be understood that, for each of the individual nozzle-diffuser assemblies <NUM>, the alignment of the nozzle <NUM> with respect to the diffuser <NUM> is determined by the assembly <NUM> itself. This contrasts with conventional multi-channel ejector devices where the alignment of the nozzle with respect to the diffuser is determined by supports within the housing.

In <FIG> the connecting structures <NUM> are axially offset along the housing from the suction inlet <NUM>. In this example a centreline 412A of the suction inlet <NUM> is offset from a centreline 482A of the apertures <NUM> by an axial distance <NUM>. This can provide an advantage of maximising the length of the diffuser <NUM> for a given length of housing. It can also help to allow the fluid arriving via inlet <NUM> to settle to some extent before entering apertures <NUM> of one of the nozzle-diffuser assemblies <NUM>. The unobstructed interior volume between the supporting walls <NUM>, <NUM> provides flexibility with nozzle-diffuser assemblies. There can be a range of different types of nozzle-diffuser assemblies <NUM> which are each suited to particular applications. For example, some applications may require a longer diffuser <NUM> section. The different types of nozzle-diffuser assemblies <NUM> can have apertures <NUM> positioned at different axial positions, while still being positioned within the unobstructed interior volume.

In <FIG> a downstream end of each of the individual nozzle-diffuser assemblies <NUM> is provided with a flange. The flange locates within a complementary recess in the supporting wall <NUM>. A nozzle-diffuser assembly <NUM> can be retained within the housing by fixings passing through the flange into the supporting wall <NUM>.

Removal of the nozzle-diffuser assemblies <NUM> will now be described. The second housing part 410B is disconnected from the first housing part 410A at joint 410C at the downstream end of the housing <NUM>. This provides clear access to the interior of the housing, and access to the downstream ends of the plurality of nozzle-diffuser assemblies <NUM>. An individual nozzle-diffuser assembly <NUM> can be removed from the housing by removing fixings securing that individual nozzle-diffuser assembly <NUM>. The selected nozzle-diffuser assembly <NUM> can then be withdrawn, as a single assembly, from the interior of the housing. Once the nozzle-diffuser assembly <NUM> has been withdrawn from the housing, it can be inspected (e.g. for routine maintenance, cleaning etc.) and re-inserted into the housing. Alternatively, the nozzle-diffuser assembly <NUM> which has been withdrawn from the housing may be replaced with a different nozzle-diffuser assembly <NUM>. The nozzle-diffuser assembly <NUM> is secured by replacing the fixings. Other nozzle-diffuser assemblies <NUM> may be operated upon in the same way. Finally, the second housing part 410B is reconnected to the first housing part 410A at joint 410C.

Similar to the single channel case of <FIG>, there are some alternatives to how the nozzle-diffuser assemblies <NUM> are supported within the housing <NUM>. In the example shown in <FIG> axial movement of the nozzle-diffuser assembly <NUM> is constrained at the upstream end (by a radial surface of collar <NUM>) and at the downstream end (by a shoulder in the supporting wall <NUM>). In other examples, the nozzle-diffuser assemblies <NUM> may be configured to allow for thermal expansion at the upstream end. For example, there can be an axial gap between the upstream end of the nozzle-diffuser assemblies <NUM> and a constraining surface in supporting wall <NUM>. This can have an advantage of allowing for thermal expansion.

<FIG> show another example of a multi-channel ejector device <NUM>. The multi-channel ejector device <NUM> is similar to the multi-channel ejector device <NUM>. The multi-channel ejector device <NUM> has a larger number of nozzle-diffuser assemblies <NUM> and shows an example of a different configuration at the upstream ends and the downstream ends of the nozzle-diffuser assemblies <NUM>. The ejector device <NUM> comprises a housing <NUM> and a plurality of nozzle-diffuser assemblies <NUM>. <FIG> shows the plurality of nozzle-diffuser assemblies <NUM> fitted within the housing <NUM>. <FIG> shows a more detailed view of the plurality of nozzle-diffuser assemblies <NUM> fitted within the housing <NUM>, with a cut-away view of some of the nozzle-diffuser assemblies <NUM>.

The housing <NUM> is formed as two housing parts: 510A, 510B. Housing parts 510A, 510B are connected together at a connection 510C. Housing part 510B may be removed from housing part 510B to allow access to the nozzle-diffuser assemblies <NUM>. The housing <NUM> comprises a first inlet <NUM>, a second inlet <NUM> and an outlet <NUM>. The first (motive) inlet <NUM> is configured to receive a high pressure fluid. The first inlet <NUM> is located at a first, upstream, end of the housing <NUM>. The second (suction) inlet <NUM> is configured to receive a fluid which is typically at a lower pressure than the pressure received at the first inlet <NUM>. The second inlet <NUM> is located part-way along the housing <NUM>. The outlet <NUM> is configured to output a combination of the fluids received via the first inlet <NUM> and the second inlet <NUM>. The outlet <NUM> is located at a second, downstream, end of the housing <NUM>.

The plurality of nozzle-diffuser assemblies <NUM> are supported within the housing by a pair of supporting walls <NUM>, <NUM>. A first supporting wall <NUM> is provided near the upstream end of the first housing part 510A and a second supporting wall <NUM> is provided at the downstream end of the first housing part 510A. Each of the supporting walls <NUM>, <NUM> has a plurality of bores for receiving the nozzle-diffuser assemblies <NUM>. A nozzle-diffuser assembly <NUM> is supported by a bore in the first supporting wall <NUM> and by a bore in the second supporting wall <NUM>. The bores in the first supporting wall <NUM> may be tapered on their downstream side. This is shown in the detailed view of <FIG>. The tapering can help to make it easier to insert the nozzle-diffuser assembly <NUM> into the supporting wall <NUM>. The upstream end of a nozzle-diffuser assembly <NUM> first locates within the wider portion of the tapered bore before being guided into the narrower portion of the bore.

<FIG> and <FIG> show an example where the nozzle-diffuser assemblies <NUM> are configured to allow for thermal expansion. The upstream end of each of the nozzle-diffuser assemblies <NUM> locates within a bore in the supporting wall <NUM>. The upstream end of each of the nozzle-diffuser assemblies <NUM> is axially spaced from a constraining surface (e.g. any radial surface or feature). This provides an axial gap to allow for thermal expansion of the nozzle-diffuser assemblies <NUM>. During operation, the nozzle-diffuser assemblies <NUM> can safely expand into this gap. This minimises problems which can arise when expansion is constrained, such as distortion of the nozzle-diffuser assemblies or an offset in the angular alignment of the nozzle and the diffuser.

The nozzle-diffuser assemblies <NUM> include a deflector vane or blade <NUM>. The deflector vanes/blades <NUM> impart a rotational force to the motive fluid flowing along the nozzle channel <NUM>. These deflector vanes/blades are described in more detail in <CIT>.

<FIG> shows some detail of a connection between an upstream end of the connecting structure <NUM> and the nozzle <NUM>. The connecting structure <NUM> has a collar <NUM> at the upstream end and a collar <NUM> at the downstream end. The collars <NUM>, <NUM> are regions which are free of apertures <NUM>. The collar <NUM> surrounds a neck portion <NUM>, <NUM> of the nozzle <NUM>. In this example, the neck portion <NUM>, <NUM> has a smaller diameter than the remainder of the nozzle <NUM> upstream (to the left) of the neck portion. During assembly of the nozzle-diffuser assembly <NUM>, the collar <NUM> of the connecting structure <NUM> is fitted around the neck portion <NUM>, <NUM> of the nozzle <NUM>. The collar <NUM> and the neck portion <NUM>, <NUM> are coaxial. The nozzle-diffuser assembly <NUM> can also use a similar type of connection between the connecting structure <NUM> and nozzle <NUM>.

<FIG> shows a cross-section through the multi-channel ejector device <NUM> in the region of the downstream ends of the nozzle-diffuser assemblies <NUM>. Each nozzle-diffuser assembly <NUM> has a flange <NUM> at the downstream end. The flange <NUM> locates within a recess in the supporting wall <NUM>. The nozzle-diffuser assembly <NUM> can be inserted into the housing until the flange <NUM> engages with a "stop" defined by a surface of the supporting wall <NUM>. A plate <NUM> extends across the downstream ends of the plurality of nozzle-diffuser assemblies <NUM>. The plate <NUM> has a plurality of apertures <NUM> which extend through the plate. The apertures <NUM> are located at positions which align with the outlets <NUM> of the individual nozzle-diffuser assemblies <NUM>. The plate <NUM> has a function of retaining the plurality of nozzle-diffuser assemblies <NUM>. Fixings <NUM> secure the plate <NUM> to the supporting wall <NUM> of the housing. In this example, the plate <NUM> extends radially beyond the plurality of nozzle-diffuser assemblies <NUM> and forms part of the flange of the housing. When the second housing part 510B is coupled to the first housing part 510A (as shown in <FIG>), an axially-directed force is exerted on the plate <NUM> which is transmitted to the downstream ends of the nozzle-diffuser assemblies. This reduces stress on the fixings <NUM>.

Removal of the nozzle-diffuser assemblies <NUM> will now be described. The second housing part 510B is disconnected from the first housing part 510A at joint 510C. This provides access to plate <NUM>. Plate <NUM> is removed. This provides clear access to the downstream ends of the plurality of nozzle-diffuser assemblies <NUM>. An individual nozzle-diffuser assembly <NUM> can be removed from the housing. The selected nozzle-diffuser assembly <NUM> can then be withdrawn, as a single assembly, from the interior of the housing. Once the nozzle-diffuser assembly <NUM> has been withdrawn from the housing, it can be inspected (e.g. for routine maintenance, cleaning etc.) and re-inserted into the housing. Alternatively, the nozzle-diffuser assembly <NUM> which has been withdrawn from the housing may be replaced with a different nozzle-diffuser assembly <NUM>. Other nozzle-diffuser assemblies <NUM> may be operated upon in the same way. Finally, the plate <NUM> is attached to the first housing part 510A and then the second housing part 510B is reconnected to the first housing part 510A at joint 510C.

The multiple-channel examples of <FIG> and <FIG> comprise a first supporting wall <NUM>, <NUM> and a second supporting wall <NUM>, <NUM>. It is possible to provide one or more additional supporting walls. More walls is less desirable as it increases the quantity of material required, increases weight and makes it more difficult to insert and withdraw nozzle-diffuser assemblies.

An ejector of the type described above may be applied in a wide variety of practical applications involving the pumping of a wide variety of "suction" fluids, e.g. gaseous phases, by a wide variety of "motive" fluids, e.g. liquid phases. Various forms of gas compression are especially useful applications. By way of non-limiting examples, some practical applications in which ejector devices may be usefully employed may include any of the following:.

Other practical applications for particular embodiments or examples, in addition to those exemplified above, may also be available.

Thus, in some non-limiting practical examples of the use of ejector devices according to embodiments, any of the following combinations of liquid phase (as the "motive" fluid) and gaseous phase (as the "suction" fluid to be pumped) may be used:.

and various other specific liquid - gas combinations.

It is to be understood that the above description of various specific embodiments has been by way of non-limiting examples only, and various modifications may be made from what has been specifically described and illustrated whilst remaining within the scope of the invention as defined by the appended claims.

Throughout the description and claims of this specification, the words "comprise" and "contain" and linguistic variations of those words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Claim 1:
An ejector device (<NUM>, <NUM>) comprising:
a housing (410A, 410B, 410C, 510A, 510B, 510C) having a motive fluid inlet (<NUM>, <NUM>) to receive motive fluid, a suction fluid inlet (<NUM>, <NUM>) to receive suction fluid and a fluid outlet (<NUM>, <NUM>) to output the motive fluid and the suction fluid
a plurality of nozzle and diffuser assemblies (<NUM>, <NUM>) configured to fit within the housing wherein each of the nozzle and diffuser assemblies comprises:
a nozzle (<NUM>);
a diffuser (<NUM>)
a connecting structure (<NUM>) connecting the nozzle to the diffuser, the connecting structure configured to permit fluid flow between the nozzle and the diffuser, the connecting structure having apertures (<NUM>, <NUM>, <NUM>) configured to allow fluid to be drawn into the fluid flow between the nozzle and the diffuser;
wherein the housing comprises a first supporting wall (<NUM>, <NUM>) and a second supporting wall (<NUM>, <NUM>),
wherein each of the first supporting wall and the second supporting wall extends radially across an interior of the housing, the first supporting wall and the second supporting wall axially spaced apart along the housing, each of the first supporting wall and the second supporting wall having a plurality of bores to receive the plurality of the nozzle and diffuser assemblies, wherein the nozzle and diffuser assemblies are individually removable from a downstream end of the housing,
characterized in that an upstream end of each of the plurality of nozzle and diffuser assemblies is axially spaced from a constraining radial surface of the first supporting wall (<NUM>, <NUM>) of the housing to allow for thermal expansion of the nozzle and diffuser assemblies.