FIELD OF INVENTION

The present invention relates to a diffuser for a jet pump of a separator for separating contaminants from a fluid stream which includes entrained contaminants. The present invention also relates to a jet pump comprising such a diffuser, and to a separator comprising such a jet pump. In particular, but not exclusively, the present invention relates to a jet pump of a separator for separating contaminants from a fluid stream which includes entrained contaminants, the diffuser comprising an inlet portion having an inlet which is adapted to receive a fluid stream including residual entrained contaminants, and an outlet portion in fluid communication with the inlet portion and having an outlet through which fluid exits the diffuser. Various other separators are also disclosed.

BACKGROUND

Blow-by gas within a reciprocating engine is generated as a by-product of the combustion process. During combustion, some of the mixture of combustion gases escapes past piston rings or other seals and enters the engine crankcase outside of the pistons. The term “blow-by” refers to the fact that the gas has blown past the piston seals. The flow level of blow-by gas is dependent upon several factors, for example the engine displacement, the effectiveness of the piston cylinder seals and the power output of the engine. Blow-by gas typically has the following components: oil (as both a liquid and an aerosol, with aerosol droplets in the range 0.1 μm to 10 μm), soot particles, nitrous oxides (NOx), hydrocarbons and other organic species, carbon monoxide, carbon dioxide, oxygen, water, and other gaseous air components.

If blow-by gas is retained within a crankcase with no outlet, the pressure within the crankcase rises until the pressure is relieved by leakage of crankcase oil elsewhere within the engine, for example at the crankcase seals, dipstick seals or turbocharger seals. Such a leak may result in damage to the engine.

In order to prevent such damage, and excessive loss of oil, it is known to provide an outlet valve that allows the blow-by gas to be vented to the atmosphere. However, with increasing environmental awareness generally, and within the motor industry in particular, it is becoming unacceptable to allow blow-by gas to be vented to atmosphere due to the discharge of oil and other contaminants from within the crankcase. Furthermore, such venting increases the speed at which crankcase oil is consumed.

Consequently, it is known to filter the blow-by gas. The filtered blow-by gas may then either be vented to the atmosphere as before (in an open loop system), or it may be returned to an air inlet of the engine (in a closed loop system). The blow-by gas may pass through a filtering medium or another known form of gas contaminant separator. The conventional arrangement of an engine blow-by gas/oil separator returning cleaned gas to an engine air intake is commonly referred to as a Closed Crankcase Ventilation (CCV) system.

The filtering of engine blow-by gas using impaction separators which remove contaminants (particularly oil aerosols) from the gas is well known. Typically, separators are fitted downstream of the gases being vented from the engine crankcase, with oil that is separated from the blow-by gasses returned to the engine sump via a drain hose.

As mentioned above, it is necessary to avoid unacceptably high engine crankcase pressures, in order to avoid oil leakage. To this end, the separator must be arranged so that a flow pressure differential across the separator is below an allowable limit set by the engine manufacturer. Typically, an upper limit of between around 5 mbar and 50 mbar is set. The blow-by gas which has been ‘cleaned’ by the separator is returned to the air intake of the engine. In this way, it is ensured that minimal oil aerosols are vented to atmosphere. In some countries, this is a specific requirement of relevant emissions legislation. For closed crankcase ventilation systems, the separation performance of the separator, and the prevention of oil mist contaminating the turbo compressor wheel, are fundamental, measured technical requirements.

The maximum gravimetric efficiency of a separator having a pressure differential within the range defined by either open or CCV systems have been measured and are known in the industry. Generally, 70%-80% of oil aerosols can be removed by mass. Utilising state of the art equipment, the fractional efficiency (i.e. the separation performance at any given particle size) can be measured to particle sizes as small as 0.03 μm. The particle challenge characteristics of the engine can similarly be measured. With engine distribution data and high-resolution fractional efficiency data, the gravimetric efficiency of a separator can now be accurately predicted. In the course of several years of research the previously accepted performance limits of impaction separators for blow-by emissions control have been exceeded. Efficiency levels of 98% and higher have been achieved.

International Patent Publication No. WO-2014/155054 discloses a prior separator in which contaminated engine crankcase blow-by gases entering a first chamber are separated from a second chamber by a rolling diaphragm forming a radial seal at the interface between the chambers. The first chamber has approximately the same pressure as the engine crankcase, while the second chamber references atmosphere. Blow-by gas enters a third chamber by passing through an acceleration aperture. Impaction and separation of oil particles due to radial acceleration occurs both on the diaphragm face, and on the surface of an annular coalescer material inserted opposite the outlet of the acceleration aperture. Use of a pre-cyclone, and the separator described, provides a high efficiency of oil removal, meeting the required gravimetric performance.

A jet pump is connected downstream of the third chamber, to create pressure lift. The jet pump is powered via air bleed from a turbocharger of the engine, and thus synergy is used to create pressure lift. The developed pressure lift is used to enhance the performance of the inertial separator, subjecting the third chamber to a vacuum. Separated oil is agglomerated into liquid droplets which drain into a sump. This oil will drain into the first chamber when the engine is keyed off, or at some idle conditions when the differential over the valve is less than 1 mbar. When the oil reaches the first chamber, it can drain through a lower spigot back to the engine crankcase.

The jet pump operates by taking a small amount of boosted air from a pre or post turbocharger intercooler manifold and directing it through a jet nozzle. The air expands and passes through a diffuser of progressively increasing flow area, entering an inlet of the diffuser at a velocity of up to around 450 m/s. This creates a static negative pressure in the third chamber, thus effectively subjecting the third chamber to a vacuum. The high velocity of the air passing through the jet pump diffuser can cause a proportion of any residual oil to separate/condense into liquid droplets at a boundary layer adjacent a wall of the diffuser. It is possible that this oil could migrate to the outlet, and eventually exit to the turbocharger or atmosphere. It is therefore desirable to improve separator efficiency.

SUMMARY

According to a first aspect of the present invention, there is provided a diffuser for a jet pump of a separator for separating contaminants from a fluid stream which includes entrained contaminants, the diffuser comprising:a. an inlet portion having an inlet which is adapted to receive a fluid stream including residual entrained contaminants, the inlet defining a first flow area;b. an outlet portion in fluid communication with the inlet portion and having an outlet through which fluid exits the diffuser, in which a flow path for the fluid stream is defined which extends from the inlet to the outlet, and in which the outlet defines a second flow area which is greater than the first flow area so that a velocity of fluid flowing through the inlet is greater than a velocity of fluid flowing through the outlet; andc. a communication port extending through a wall of the diffuser and having an inlet which communicates with an interior of the diffuser and an outlet which communicates with an exterior of the diffuser, in which the inlet of the communication port is located at a position along the flow path which is between the inlet of the diffuser and the outlet of the diffuser, so that contaminants which have become separated from the fluid stream during flow along the flow path can be removed from the diffuser through the communication port.

The present invention provides the advantage that it enables contaminants which have become separated from the fluid stream during flow along the diffuser, and/or which have condensed on an inner wall of the diffuser, to be removed from the diffuser through the communication port. This reduces the risk of the contaminants passing to the outlet of the diffuser and so exiting to the atmosphere, or to other engine components such as a compressor of a turbocharger. Typically, residual contaminants separated and/or which have condensed from the fluid stream will reside on an inner wall of the diffuser, where they risk becoming re-entrained with fluid in the fluid stream.

Reference is made in this document to a “jet pump”. The terms “eductor pump” and “venturi pump” may be used interchangeably with the term jet pump.

Reference is made to the removal of residual contaminants entrained in the fluid stream. It will be understood that these are contaminants which remain in the fluid stream following separation from the fluid stream upstream of the jet pump, for example by impacting on an impaction surface of the separator.

Reference is made to flow areas defined by the inlet and the outlet of the diffuser. It will be understood that these may be taken to be areas defined by openings of the diffuser which form the inlet and the outlet.

The diffuser may serve for reducing the velocity of the fluid in the flow path from a first velocity at the diffuser inlet to a second, lower velocity at the diffuser outlet. The diffuser may also serve for increasing the pressure of the fluid in the flow path from a first pressure at the diffuser inlet to a second, higher pressure at the diffuser outlet. A lower velocity/higher pressure flow may be more suitable for discharge to the atmosphere and/or supply to an engine component such as a compressor of a turbocharger. The diffuser may act as, or make generally take the form of, a venturi tube. As will be understood by persons skilled in the art that such flow velocity decrease and pressure increase may cause contaminants to separate from the fluid in the fluid stream and/or condensation of contaminants on the inner wall of the diffuser.

The outlet of the communication port may be adapted to be exposed to fluid at a pressure which is lower than a pressure of the fluid contained within the diffuser, so that contaminants are drawn through the communication port. The contaminants may be entrained within a bleed stream separated from the fluid stream flowing along the flow path through the diffuser. The outlet may be adapted to be coupled to a source of a vacuum. The inlet of the communication port may be adapted to be exposed to fluid contained within the diffuser. The outlet may be adapted to communicate with a fluid which is at a pressure that is less than the pressure of the fluid contained within the diffuser, which fluid may be contained within a part of the diffuser that the inlet of the communication port opens on to. This may create a pressure differential across the communication port from its inlet to its outlet, which may serve to draw contaminants through the communication port (which may be entrained within the bleed stream). The outlet may be adapted to communicate with a chamber containing a fluid which is at a pressure which is less than the pressure of the fluid contained within the diffuser.

The diffuser may be tubular and may have a generally circular shape in cross-section. The diffuser may define a bore extending from the inlet to the outlet. The bore may be generally circular in shape. Other arcuate shapes for the diffuser/bore may be suitable, including elliptical and oval. The diffuser may have a substantially constant internal profile (for example circular) extending from the inlet to the outlet.

The communication port, or at least its inlet, may be disposed in a location which promotes the flow of contaminants from the diffuser under the action of gravity. The communication port may extend through a part of the wall of the diffuser which is disposed lowermost, and which may be disposed lowermost during use of the diffuser. This may facilitate flow of contaminants from the diffuser into the communication port. The communication port may be disposed at a location on a perimeter of the diffuser which is disposed lowermost. The communication port may be disposed at or near a position that is approximately 180° around a circumference of the diffuser from an upper region of the diffuser, when looking along its length (i.e. a six o'clock position).

The communication port may be defined by a bore extending through the wall of the diffuser. The bore may have a longitudinal axis extending between the inlet and the outlet of the port. The axis may be substantially parallel to a longitudinal axis of the diffuser, the diffuser axis extending between its inlet and its outlet.

Whilst the withdrawal of contaminants from the diffuser can be affected via a single communication port, it will be understood that the diffuser may comprise a plurality of communication ports. The communication ports may be spaced apart around a perimeter of the diffuser, and/or along a length of the diffuser.

The diffuser may comprise a contaminant outlet tube in fluid communication with the outlet of the communication port. The outlet tube may define a passage for the flow of contaminants (and fluid in which the contaminants may be entrained) from the diffuser to a remote location. The outlet tube may advantageously provide the ability to discharge contaminants to a calm zone, which may be an area of the separator which experiences reduced fluid disturbance in comparison to other areas of the separator. This may help to avoid re-entrainment of the contaminants in the fluid flowing through the separator and into the diffuser. The outlet tube may comprise an inlet which communicates with the outlet of the communication port. The outlet tube may be provided integrally with the diffuser.

The diffuser may comprise a transition portion disposed between the inlet portion and the outlet portion. The transition portion may define a third flow area which is greater than the first flow area but less than the second flow area. This may promote the formation of an eddy within the outlet portion. The eddy may be disposed downstream of the transition portion and may be disposed towards or within a boundary layer of the fluid contained within the diffuser. As will be understood by persons skilled in the art, the boundary layer forms adjacent a boundary of the diffuser, in this case an inner wall of the diffuser. A portion of the fluid flowing along the flow path from the inlet towards the outlet may enter the eddy. Fluid in the eddy may flow in a reverse direction from the outlet back towards the inlet, which may re-entrain contaminants (that may reside on an inner wall of the outlet portion) which have separated or condensed from the fluid stream during flow along the flow path. The portion of the fluid may flow along an eddy flow path, which may extend generally in a loop so that the fluid in the eddy flow path flows along the diffuser generally towards the outlet before reversing direction to flow generally towards the inlet. The portion of the fluid may flow around the eddy flow path multiple times. The portion of the fluid may leave the eddy flow path and exit the diffuser through the communication port.

The inlet of the diffuser may describe a maximum internal dimension, which may be a width (and which may be a diameter when the diffuser bore is circular). The outlet may describe a maximum internal dimension, which may correspond to that of the inlet, and which may be a width (optionally a diameter). The maximum internal dimension described by the outlet may be greater than the corresponding maximum internal dimension defined by the inlet.

The transition portion may define an opening describing a maximum internal dimension, which may correspond to that of the inlet, and which may be a width (optionally a diameter). The maximum internal dimension described by the opening of the transition portion may be greater than the corresponding maximum internal dimension defined by the inlet, and less than the corresponding maximum internal dimension defined by the outlet. This may assist in formation of the eddy, which may be formed at or near to an intersection between the transition portion and the outlet portion.

The transition portion may comprise a lip, or a ridge, rim, ledge, step or shoulder, which may describe the maximum internal dimension of the opening. The lip may be defined between the inlet portion and the outlet portion. The lip may be disposed in the flow path. An internal bore of the diffuser may step up from the maximum internal dimension described by the lip, to the maximum internal dimension defined by the outlet. The step change in the dimension may promote formation of the eddy, which may form at a location downstream of the lip.

The lip may define a surface which faces generally towards the outlet of the diffuser. The diffuser may define a longitudinal axis extending from the inlet to the outlet. The lip surface may be disposed transverse to the longitudinal axis. This may promote the flow of contaminants, particularly liquid contaminants such as oil, (which have separated/condensed from the fluid stream e.g. on to the internal surface of the diffuser) towards a lower region of the diffuser, under the action of gravity.

The lip surface may be disposed at a non-perpendicular angle relative to the longitudinal axis. The lip surface may be disposed at an angle of up to around 89° relative to the longitudinal axis, optionally in the range of about 80° to about 89°, for example about 80° to about 85°. The lip surface may therefore be disposed at an angle of at least 1° relative to a line which is perpendicular to the longitudinal axis. The lip surface may be declined in a direction from an upper region of the diffuser towards a lower region of the diffuser. A portion of the lip surface which is disposed towards the lower region of the diffuser may therefore be closer to the outlet than a portion of the lip surface which is disposed towards the upper region of the diffuser.

The lip surface may be substantially planar so that all of the lip surface is in the same plane and at the same angle. The lip surface may alternatively be curved.

The communication port may be located generally in the region of an intersection between the transition portion and the outlet portion. This may promote the flow of fluid with entrained contaminants through the communication port, and in particular the drawing of fluid flowing in the eddy through the port. The lip surface may be arranged relative to the inlet of the communication port so as to promote the flow of contaminants from the lip surface towards the inlet. The lip surface may comprise a lower region which is arranged to discharge fluid running along the lip surface from the surface and into the inlet of the communication port. This may be achieved by positioning the lip surface so that an edge of the lip surface is adjacent to the inlet, suitably above the inlet, and proximate to the inlet in a direction along the length of the diffuser. The inlet of the communication port may communicate with the outlet portion of the diffuser. The inlet may open on to the outlet portion. However, at least part of the inlet may open on to the transition portion, for example the lip surface. The inlet may straddle the transition portion (for example the lip surface) and the outlet portion.

The diffuser may comprise a channel extending at least part way around an internal surface of the diffuser. The channel may communicate with the communication port of the diffuser. The channel may serve for directing contaminants to the inlet of the communication port. The channel may extend around an internal perimeter of the diffuser, which may be an internal circumference where the diffuser has a circular bore. The channel may extend around the entire internal surface of the diffuser.

The provision of such a channel may provide the advantage that it helps to prevent re-entrainment of contaminants which have separated from the fluid flowing through the diffuser back into the body of fluid flowing along the diffuser towards the outlet. The channel may also assist in directing contaminants to the communication port for evacuation.

The channel may be disposed at a non-perpendicular angle relative to a longitudinal axis of the diffuser. The channel may be disposed at an angle of up to around 89° relative to the longitudinal axis, optionally in the range of about 80° to about 89°, for example about 80° to about 85°. The channel may therefore be disposed at an angle of at least 1° relative to a line which is perpendicular to the longitudinal axis. The channel may be declined in a direction from an upper region of the diffuser towards a lower region of the diffuser. A portion of the channel which is disposed towards the lower region of the diffuser may therefore be closer to the outlet than a portion of the lip surface which is disposed towards the upper region of the diffuser.

The channel may be defined by a channel element, which may be located within the diffuser at a position along the flow path which is disposed between the inlet of the diffuser and the outlet of the diffuser. The channel element may be an insert which is adapted to be located within the diffuser, suitably within the bore of the diffuser. The channel element may be annular or generally ring-shaped.

The channel may be defined between an external surface of the channel element and the internal surface of the diffuser. The channel element may comprise an inner surface defining a tubular bore forming part of the flow path, and an outer surface which defines the channel. The channel element may comprise a recess or step in the outer surface, which may extend at least part way around the outer surface, and which at least partly defines the channel. The channel may be defined between the recess and the internal surface of the diffuser.

The channel element may comprise at least one flow passage which communicates with the channel. Contaminants may be drawn through said flow passage into the channel, and then out of the diffuser through the communication port.

At least one downstream flow passage may be provided, having a first end which opens on to the channel, and a second end which opens on to the interior of the diffuser at a location which is downstream of the communication port. Said flow passage may serve for drawing contaminants in or near an eddy defined downstream of the channel element into the channel and so to the communication port.

At least one upstream flow passage may be provided, having a first end which opens on to the channel, and a second end which opens on to the interior of the diffuser at a location which is upstream of the communication port. Said flow passage may serve for drawing contaminants at or near an internal surface of the diffuser (e.g. in a boundary layer) upstream of the channel element into the channel and so to the communication port.

The at least one flow passage may extend through the channel element, and may extend through a body of the channel element. This may apply particularly to a downstream flow passage. Said flow passage may be: a closed passage such as a bore; or a recess formed in an outer surface of the channel element, the flow passage being defined by the recess and an internal surface of the diffuser.

The channel element may comprise a plurality of flow passages, which may be spaced apart around a perimeter of the channel element. Where the channel element is annular/ring-shaped, the flow passages may be spaced apart around a circumference of the element. The flow passages may be equally spaced. Whilst any suitable number of passages may be provided, possible arrangements include flow passage spacings of: 120°; 90°; 60°; 45° and 30°. A particularly suitable spacing may be 90°. It will be understood that the spacings may be measured from centre to centre of the flow passages, considered in a direction around the perimeter of the channel element.

The at least one flow passage may be defined between an external surface of a part of the channel element and an internal surface of the diffuser. This may apply particularly to an upstream flow passage. Said flow passage may be a space or void extending at least part way around the external surface of said part of the channel element, which may be an annular passage. Said flow passage may extend around an entire perimeter of the channel element.

The channel element may comprise a shoulder part adapted to abut an internal surface of the diffuser (which may serve for mounting the channel element in the diffuser), and a channel part which extends from the shoulder part and which defines at least part of the channel. The shoulder part and the channel part may be provided integrally or as separate parts which are coupled together. Where the channel element comprises at least one upstream flow passage, the channel part may define said flow passage. The channel part may be mountable within the diffuser bore so that it is free floating/cantilevered within the bore, spaced from the internal surface of the diffuser. This may be achieved via the shoulder part, which mounts the channel element in the diffuser.

The channel element may comprise a central opening forming part of, and/or which is on or in, the flow path. The central opening may define a further flow area which is less than the second flow area. The central opening may define a further flow area which is greater than the first flow area.

The channel element may define at least part of the transition portion. The channel element may be provided at a location which is downstream of the transition portion, along the flow path.

According to a second aspect of the present invention, there is provided a jet pump comprising a diffuser according to the first aspect of the invention.

According to a third aspect of the present invention, there is provided a separator comprising a jet pump having a diffuser according to the first aspect of the invention.

Further features of the diffuser forming part of the jet pump of the second and third aspects of the invention may be derived from the text set out elsewhere in this document, in particular from the text defining optional further features of the diffuser of the first aspect of the invention.

The separator may comprise a housing defining an inlet. The separator may comprise a first chamber, which may be defined within the housing, the first chamber arranged to receive a first fluid stream from the inlet for flow along the chamber, optionally for axial flow along the chamber. The separator may comprise an impaction surface provided within the housing and located downstream of the first chamber. The impaction surface may be arranged to deflect the first fluid stream after it leaves the first chamber such that contaminants are separated from the first fluid stream. The separator may comprise a further chamber defined by the housing and arranged to receive the first fluid stream following impaction on the impaction surface. The separator may comprise a dividing wall which separates the further chamber from the impaction surface, the dividing wall having at least one aperture formed in it through which the first fluid stream can pass out of the chamber towards the impaction surface. The separator may comprise an actuator which is arranged to move along an actuator axis to adjust the open cross-sectional area of the at least one aperture in the dividing wall according to a pressure differential between fluid pressure in the first chamber and a pressure reference (which may be atmospheric pressure) by moving along the dividing wall so as progressively to occlude the apertures.

The fluid stream flowing along the diffuser may contain residual contaminants which remain entrained with the fluid following impaction on the impaction surface. The fluid stream including residual entrained contaminants may be a second fluid stream and may comprise the first fluid stream exiting the chamber following impaction on the impaction surface, and a further fluid injected into the separator through an injection assembly of the jet pump. The first fluid stream may therefore be entrained with the fluid injected through the injection assembly and directed into the diffuser. The jet pump may serve for accelerating the velocity of the fluid that has exited the chamber following impaction on the impaction surface. This may generate a region of reduced pressure which serves to draw the first fluid stream through the separator, in particular through the at least one aperture in the dividing wall.

The actuator may comprise a flexible seal for occluding the at least one aperture, which may be a flexible diaphragm. The chamber having an inlet through which a fluid stream enters the separator may be a first chamber. The separator may comprise a second chamber which references atmospheric pressure, and which may provide the pressure reference. The seal may isolate the first chamber from the second chamber. The separator may comprise a third chamber. The impaction surface may be disposed in the third chamber. The outlet of the diffuser communication port may communicate with the third chamber. The third chamber may contain fluid at a pressure which is less than the pressure of the fluid contained within the diffuser (at least in the region of the communication port). The inlet of the diffuser may communicate with the third chamber so that, during operation of the jet pump, the flow of fluid along the flow path through the diffuser acts to reduce the pressure of fluid in the third chamber relative to the pressure of fluid in the first chamber, to draw fluid through the separator (in particular the at least one aperture in the dividing wall) and into the third chamber.

The actuator may be movable between a fully open position (which may be an upper position) in which the seal provides a minimum occlusion of the at least one aperture and a fully closed position (which may be a lower position) in which the seal provides a maximum occlusion of the at least one aperture. The seal may be configured so that the at least one aperture is not occluded when it is in its fully open position. The seal may be configured to completely occlude the at least one aperture in its fully closed position. Occlusion of the at least one aperture may involve restricting an effective flow area of the aperture.

The dividing wall may comprise a plurality of apertures. Each aperture may be at least one of circumferentially spaced around and axially spaced along the dividing wall from at least one other aperture.

The dividing wall may have a cylindrical tubular shape. The chamber may be defined by the dividing wall. The cylindrical tubular shape of the dividing wall may have a circular cross-section.

The jet pump may be located downstream of the impaction surface, and arranged to generate a pressure differential which draws the first fluid stream through the separator. The jet pump may be coupled to the housing, and may comprise a fluid injection assembly and the diffuser. The diffuser may be arranged in fluid communication with the further chamber so that the first fluid stream exits the further chamber and flows into the diffuser. The fluid injection assembly may be arranged to inject a further fluid into the diffuser to form a second fluid stream comprising the injected fluid and the first fluid stream. The further fluid may be air derived, for example, from a turbocharger of an engine. The fluid injection assembly may comprise an injector arranged to inject the further fluid into the diffuser, and a flange for securing the injection assembly to the housing. The flange may be sealingly coupled to the housing via a friction weld. Use of a friction weld may both securely couple the flange (and so the injection assembly) to the housing and seal the flange (and so the injection assembly) relative to the housing. This may be achieved in a single procedure/step and may avoid a requirement to provide other couplings such as a threaded coupling, nut and bolt assemblies or the like between the flange and the housing. The housing and the flange may be of a plastics material, which may be a polymeric material, and which may be a thermoplastics material. This may promote fusion welding, such as a spin welding technique, an ultrasonic welding technique, or an electromagnetic welding technique. Other parts of the separator, including of the injection assembly, may be formed of such materials.

The separator housing may define a drain.

The jet pump may be a primary jet pump located downstream of the impaction surface, the primary jet pump arranged to generate a pressure differential which draws the first fluid stream through the separator. The primary jet pump may comprise a fluid injection assembly and a diffuser, the diffuser arranged in fluid communication with the further chamber so that the first fluid stream exits the further chamber and flows into the diffuser. The fluid injection assembly may be arranged to inject a further fluid into the diffuser to form a second fluid stream comprising the injected fluid and the first fluid stream.

The separator may comprise a secondary jet pump for evacuating contaminants from the further chamber, which contaminants have been separated from the first fluid stream and collected in the further chamber. The secondary jet pump may communicate with the drain so that the contaminants can exit the separator through the drain. The secondary jet pump may be disposed entirely within the separator housing.

The provision of a secondary jet pump provides the advantage that contaminants can be continuously drained from the further chamber during operation of the separator. Accordingly, drainage of contaminants does not require a vehicle engine to be keyed off, and so deactivation of the separator.

Positioning the secondary jet pump entirely within the housing enables fluid flow to and through the secondary jet pump to be routed internally of the separator, which may provide advantages including ease of manufacture and/or assembly, improved safety (less likelihood of damage to externally routed piping), and improved aesthetic qualities.

The secondary jet pump may be arranged to generate a pressure differential which draws the contaminants from the further chamber. The secondary jet pump may receive a supply of further fluid from the injector assembly of the primary jet pump, to generate the pressure differential. The secondary jet pump may comprise a fluid injection assembly and a diffuser. The injection assembly of the secondary jet pump may receive the supply of further fluid from the primary jet pump. The injection assembly of the secondary jet pump may direct the supply of further fluid into an inlet of its diffuser. The injection assembly of the secondary jet pump may communicate with the injection assembly of the primary jet pump for the supply of further fluid to the secondary jet pump. A communication channel may be provided between the injection assembly of the primary jet pump and the secondary jet pump, which communication channel may be routed internally of the housing. The diffuser of the secondary jet pump may have an outlet which communicates with a lower chamber of the separator, which may define the drain. The secondary jet pump may communicate with the further chamber so that contaminants are drawn from the further chamber and directed into its diffuser for discharge into the lower chamber. The contaminants may be drawn into the diffuser by the pressure differential which is created by operation of the secondary jet pump. The secondary jet pump may open on to the further chamber at a location which is between the injection assembly and the diffuser.

The fluid injection assembly of the primary jet pump may comprise an injector arranged to inject the further fluid into the diffuser, and a flange coupled to the injector for securing the injector to the housing. The flange may be sealingly coupled to the housing via a friction weld. The fluid injection assembly may comprise an inlet tube, and a flange coupled to the inlet tube for securing the inlet tube to the housing. The flange may be sealingly coupled to the housing via a friction weld. The injector flange and the inlet tube flange may be friction welded to the housing in a single step or procedure. The injector flange may be an inner flange, and the inlet flange may be an outer flange. A chamber may be defined between the inlet tube and the injector, which may communicate with the secondary jet pump, in particular with the communication channel.

According to a fourth aspect of the present invention, there is provided a separator for separating contaminants from a fluid stream which includes entrained contaminants, comprising:a. a housing defining an inlet;b. a first chamber provided within the housing and arranged to receive a first fluid stream from the inlet for flow along the chamber;c. an impaction surface provided within the housing and located downstream of the first chamber, the impaction surface being arranged to deflect the first fluid stream after it leaves the first chamber such that contaminants are separated from the first fluid stream;d. a further chamber provided within the housing and arranged to receive the first fluid stream following impaction on the impaction surface; ande. a jet pump located downstream of the impaction surface, the jet pump arranged to generate a pressure differential which draws the first fluid stream through the separator;f. in which the jet pump is coupled to the housing and comprises a fluid injection assembly and a diffuser, the diffuser arranged in fluid communication with the further chamber so that the first fluid stream exits the further chamber and flows into the diffuser, and the fluid injection assembly arranged to inject a further fluid into the diffuser to form a second fluid stream comprising the injected fluid and the first fluid stream;g. and in which the fluid injection assembly comprises an injector arranged to inject the further fluid into the diffuser, and a flange for securing the injection assembly to the housing, the flange being sealingly coupled to the housing via a friction weld.

The separator may comprise a dividing wall provided within the housing and which separates the first chamber from the impaction surface. The dividing wall may have at least one aperture formed in it through which the first fluid stream can pass out of the first chamber towards the impaction surface. The pressure differential generated by the jet pump may draw the first fluid stream through the at least one aperture. The separator may comprise an actuator which is arranged to move along an actuator axis to adjust an open cross-sectional area of the at least one aperture in the dividing wall according to a pressure differential between fluid pressure in the first chamber and a pressure reference by moving along the dividing wall so as progressively to occlude the at least one aperture.

According to a fifth aspect of the present invention, there is provided a method of assembling a separator for separating contaminants from a fluid stream which includes entrained contaminants, in which the method comprises:a. providing a housing defining an inlet;b. providing a first chamber within the housing which can receive a first fluid stream from the inlet for flow along the chamber;c. providing an impaction surface within the housing and arranging the impaction surface so that it is located downstream of the first chamber so that it can deflect the first fluid stream after it leaves the first chamber to separate contaminants from the first fluid stream;d. providing a further chamber within the housing which can receive the first fluid stream following impaction on the impaction surface;e. coupling a jet pump comprising a fluid injection assembly and a diffuser to the housing downstream of the impaction surface, the jet pump being arranged to generate a pressure differential which draws the first fluid stream through the separator;f. arranging the diffuser in fluid communication with the further chamber so that the first fluid stream can exit the further chamber and flow into the diffuser;g. arranging an injector of the fluid injection assembly so that it can inject a further fluid into the diffuser to form a second fluid stream comprising the injected fluid and the first fluid stream; andh. securing the fluid injection assembly to the housing by sealingly coupling a flange of the injection assembly to the housing using a friction welding procedure.

Further features of the separator of the fourth aspect of the invention (for example of the jet pump and particularly the injection assembly and the diffuser), and the method of the fifth aspect of the invention, may be derived from the text set out elsewhere in this document, in particular from the text relating to any one of the first to third aspects of the invention.

According to a sixth aspect of the present invention, there is provided a separator for separating contaminants from a fluid stream which includes entrained contaminants, comprising:a. a housing defining an inlet and a drain;b. a first chamber provided within the housing and arranged to receive a first fluid stream from the inlet for flow along the chamber;c. an impaction surface provided within the housing and located downstream of the first chamber, the impaction surface being arranged to deflect the first fluid stream after it leaves the first chamber such that contaminants are separated from the first fluid stream;d. a further chamber provided within the housing and arranged to receive the first fluid stream following impaction on the impaction surface;e. a primary jet pump located downstream of the impaction surface, the primary jet pump arranged to generate a pressure differential which draws the first fluid stream through the separator, in which the primary jet pump comprises a fluid injection assembly and a diffuser, the diffuser arranged in fluid communication with the further chamber so that the first fluid stream exits the further chamber and flows into the diffuser, and the fluid injection assembly arranged to inject a further fluid into the diffuser to form a second fluid stream comprising the injected fluid and the first fluid stream; andf. a secondary jet pump for evacuating contaminants from the further chamber, which contaminants have been separated from the first fluid stream and collected in the further chamber, in which the secondary jet pump communicates with the drain so that the contaminants can exit the separator;g. in which the secondary jet pump is disposed entirely within the separator housing.

Further features of the separator of the sixth aspect of the invention (for example of the primary and secondary jet pumps) may be derived from the text set out elsewhere in this document, in particular from the text relating to any one of the first to fifth aspects of the invention.

In another aspect of the present invention, there is provided a crankcase ventilation system comprising the separator of any one of the third, fourth or sixth aspects of the invention.

Further aspects of the invention may comprise one or more feature derived from one or more of the aspects of the invention set out above.

