WO2009037496A2

WO2009037496A2 - A separator

Info

Publication number: WO2009037496A2
Application number: PCT/GB2008/050768
Authority: WO
Inventors: Jamie Archer; Adrian Mincher; Mark A. Glynn
Original assignee: Parker Hannifin (Uk) Ltd
Priority date: 2007-09-22
Filing date: 2008-09-02
Publication date: 2009-03-26
Also published as: GB201003420D0; GB0813939D0; GB2465514A8; GB2465514A; GB0718519D0; GB2452980A; WO2009037496A3; GB2465514B

Abstract

A separator for separating contaminants from a fluid stream. The separator comprises a chamber (20), a first inlet (6) for receiving a first fluid stream, and a convergent nozzle (18) at a first end of the chamber (20;58) coupled to the first inlet (6) for accelerating the first fluid stream passing into the chamber (20;58). The separator further comprises a second inlet (2) for receiving a second fluid stream including entrained contaminants into the chamber (20;58), the second inlet (2) being arranged relative to the first inlet (6) such that the first fluid stream can entrain and accelerate the second fluid stream forming a combined fluid stream within the chamber (20;58). The separator further comprises a surface (36, 50) coupled to the chamber (20;58) arranged such that the surface (36;50) can cause a deviation in the course of the combined fluid stream incident upon it such that contaminants are separated from the combined fluid stream.

Description

A Separator

The present invention relates to a separator. In particular, the present invention relates to a separator for separating particulate, liquid and aerosol contaminants from a fluid stream. Certain embodiments of the present invention relate to a separator for separating particulate, liquid and aerosol contaminants from a blow-by gas stream within a reciprocating engine.

Blow-by gas within a reciprocating engine is generated as a by-product of the combustion process. During combustion, some of the mixture of gases escape past piston rings or other seals and enter 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 lOμm), soot particles, nitrous oxides (NOx), hydrocarbons (both gaseous hydrocarbons and gaseous aldehydes), 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 which 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 increasingly unacceptable to allow blow-by gas, which is inevitably contaminated with oil and other contaminants from within the crankcase, to simply be vented to atmosphere. 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 filtering may be performed by passing the blow-by gas through a filtering medium, or another known form of gas contaminant separator. For a closed loop system, filtration is required in order to remove oil, soot and other contaminants to protect engine components from fouling and any resultant reduction in performance or failure of a component.

There is an increasing demand for higher efficiency cleaning of blow-by gas in both open and closed loop systems. For instance, separation efficiency of greater than 85% measured by mass (gravimetric) for particles greater than or equal to 0.3μm is required by many engine manufacturers.

Separation using filter mediums is undesirable as such filters have a finite lifespan before they become clogged and must be replaced. Engine manufacturers and end users in general prefer to only use engine components that can be fitted and remain in place for the life of the engine. While fit for life separators are known, typically only driven centrifugal separators have hitherto been able to achieve the required levels of separation efficiency.

Such a driven centrifugal separator is cumbersome and has moving parts which may be prone to failure. Impactor separators (where separation occurs as a contaminated gas stream is incident upon an impactor plate transverse to the gas flow) are not usually able to achieve the required separation efficiency.

It is an object of embodiments of the present invention to obviate or mitigate one or more of the problems associated with the prior art, whether identified herein or elsewhere. Specifically, it is an object of embodiments of the present invention to provide a high efficiency, fit for life separator for separating contaminants from a fluid stream that is not dependent upon moving parts.

According to an aspect of the present invention there is provided a separator for separating contaminants from a fluid stream, comprising: a chamber; a first inlet for receiving a first fluid stream into the chamber including a convergent nozzle for accelerating the first fluid stream; a second inlet for receiving a second fluid stream including entrained contaminants into the chamber, the second inlet being arranged relative to the first inlet such that the first fluid stream can entrain and accelerate the second fluid stream forming a combined fluid stream within the chamber; and a surface coupled to the chamber arranged such that the surface can cause a deviation in the course of the combined fluid stream incident upon it such that contaminants are separated from the combined fluid stream.

An advantage of the present invention is that contaminants can be removed from a fluid stream without the need for driven or moving parts while still achieving high separation efficiency. The present invention is particularly suitable for separating contaminants from a gas stream. More particularly, the present invention is suitable for removing contaminants from a blow-by gas stream derived from an internal combustion engine. Such a separator may be a fit for life separator owing to the absence of moving parts that may fail or filter mediums that would be prone to clogging and require periodic replacement. Advantageously, the separator provides for high separation efficiency and low or no pressure drop across the system between the blow -by gas inlet and the blow-by gas outlet. Furthermore, separators in accordance with embodiments of the present invention are relatively small, simple and cost effective to manufacture and have a small number of parts.

The surface may comprise an impaction plate. The impaction plate may be positioned in a plane at approximately 90° to the combined fluid stream, such that the impaction plate can cause a deviation in course of the combined fluid stream of approximately 90°. The separator may further comprise a gap extending about at least a portion of the periphery of the impaction plate at the end of the chamber remote from the convergent nozzle, arranged such that the combined fluid stream can pass through the gap into a collection space. The gap may further comprise a bend operable to cause a further deviation in the course of the combined fluid stream.

The impaction plate may be mounted such that it can move within the chamber towards and away from the first inlet, decreasing and increasing respectively the size of the gap about at least a portion of the periphery of the impaction plate. The impaction plate may be biased towards the first inlet, the impaction plate further comprising one or more protrusions arranged to space the impaction plate apart from the chamber wall when the impaction plate is at its position closest to the first inlet to preserve at least a minimum size of gap.

Advantageously, biasing the impaction plate towards the first inlet, for instance by mounting the impaction plate upon a spring, allows the position of the impaction plate to vary according to the flow rate of the combined fluid stream. When the flow rate is low, the impaction plate moves towards the first inlet. This reduces the size of the annular gap so that separation efficiency is increased. When the flow rate increases, the force of the combined fluid stream incident upon the impaction plate causes the impaction plate to be forced back against the action of the spring, thereby increasing the size of the gap. Advantageously, this prevents excessive pressure from building up within the crank case.

Alternatively, the surface may comprise an interior surface of a cyclone chamber arranged to receive the combined fluid stream.

The separator may further comprise a second impaction surface within the second inlet arranged such that the second impaction surface causes a deviation in the course of the second fluid stream incident upon it such that contaminants are separated from the second fluid stream.

Advantageously, this allows separation to take place within the second inlet before the fluid streams have combined. This may comprise the primary separation. This reduces the requirement for separation of the combined fluid stream, which allows for a more effective jet pumping effect. This in turn allows for high rates of separation efficiency to be achieved within the second inlet.

The second inlet may comprise a narrowed portion, the second impaction surface being positioned proximal to the narrowed portion such that the second fluid stream is incident upon the second impaction surface after passing through the narrowed portion. The second inlet may further comprise a bypass valve arranged such that when fluid pressure within the second inlet exceeds a predetermined value the bypass valve opens to allow at least a portion of the second fluid to pass through a second narrowed portion and be incident upon a third impaction surface.

The separator may further comprise a fluid outlet allowing the cleaned fluid stream to exit the separator. The separator may further comprise a drain positioned to allow contaminants to drain from the separator.

The convergent nozzle may comprise a convergent-divergent nozzle. The convergent nozzle may comprise a tube including a restricted central portion. The chamber may be generally cylindrical and the chamber diameter proximate to the convergent nozzle may be between 2 and 5 times larger than the diameter of the narrowest diameter of the convergent nozzle. The convergent nozzle may be arranged to generate a region of reduced pressure within the chamber about the first inlet operable to draw in the second fluid stream from the second inlet.

The separator may further comprise an annular second nozzle surrounding the first inlet, the second nozzle being in communication with the second inlet such that the second fluid stream can flow through the second nozzle. The second inlet may communicate with an annular space surrounding the chamber, the annular space in turn communicating with the annular second nozzle. The annular second nozzle may be arranged such that the second fluid stream can flow into the chamber generally parallel to the first fluid stream from the first inlet.

The chamber may be generally formed as a cylinder, the diameter of the chamber reducing towards the surface.

The fluid streams may comprise gas streams. The separator may be operable to separate particulate, liquid and/or aerosol contaminants from the combined gas stream. The separator may be operable to separate greater than 95% of particles greater than 0.3μm in diameter from the combined fluid stream. In another aspect of the present invention there is provided an internal combustion engine including a separator as described above, wherein the second inlet is arranged to receive blow-by gas derived from a crankcase. The first inlet may be arranged to receive a pressurised gas stream derived from a turbocharger and the separator may be operable to separate crankcase oil from the combined gas stream, the separator being arranged to return separated crankcase oil to the crankcase.

The internal combustion engine may further comprise a vacuum limiting valve coupled to a gas outlet. The internal combustion engine may further comprise a pressure regulation valve coupled to the second inlet. The internal combustion engine may further comprise a check valve coupled to a contaminant drain arranged to prevent contaminants being drawn into the separator through the contaminant drain.

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

Figure 1 is a perspective view of a separator in accordance with a first embodiment of the present invention;

Figure 2 is a cross sectional view through the separator of figure 1;

Figure 3 is an enlarged portion of the cross sectional view of figure 2;

Figure 4 is a graph illustrating the variation of engine output power with engine speed for an exemplary engine firstly without a separator fitted, and secondly with a separator in accordance with an embodiment of the present invention fitted to extract contaminants from a blow-by gas stream;

Figure 5 schematically illustrates a separator in accordance with embodiments of the present invention used in a closed loop application in combination with a reciprocating engine; Figure 6 is a perspective view of a separator in accordance with a second embodiment of the present invention,

Figure 7 is a first cross sectional view through the separator of figure 6 illustrating the relative arrangements of the gas mlets;

Figure 8 is a second cross sectional view through the separator of figure 6 in a plane that is perpendicular to the plane illustrated in figure 7, illustrating the relative arrangement of the gas outlet and the contaminant outlet,

Figure 9 is a cross sectional view through of a separator in accordance with a third embodiment of the present invention m a first mode of operation,

Figure 10 is a cross sectional view of the separator of figure 9 in a second mode of opeiation,

Figuie 1 1 is a partially cut away perspective view of the part of the separator of figure 9 in the fust mode of operation,

Figuie 12 is a perspective view of a baffle plate forming part of the separator of figure 9,

Figure 13 is a perspective view of a separator in accordance with a fourth embodiment of the present invention, and

Figure 14 is a cross sectional view through the separator of figure 13

Referring first to figure 1, this is a perspective view of a separator in accordance with a first embodiment of the present invention for separating liquid, aerosol and particulate contaminants from a blow-by gas stream. The separator compπses a blow-by gas inlet 2, a cleaned blow-by gas outlet 4, a boost gas inlet 6 and an oil dram 8 The boost gas comprises a pressuπsed gas source, which may be either pressuπsed air (for instance from a turbocharger) or exhaust gas The boost gas need not be at a high velocity on entering the boost gas inlet The boost gas could be static, though under pressure Optionally, the boost gas could be obtained from the exhaust or the turbocharger and stored in a separate holding chamber or collector prior to being passed to the boost gas inlet. The oil drain 8 allows separated oil and other contaminants to be extracted, either to be returned to the engine crankcase or stored in another chamber. Each of the inlets and outlets are suitable for connection to hoses for transfer of the various fluids to or from the engine or other devices. Flanges 10 are provided on each inlet or outlet to assist in attaching hoses.

Referring to figure 2, this illustrates in cross section the separator of figure 1 through a plane passing through the axis of each inlet or outlet. The separator is formed from three parts: an inlet assembly 12, an outlet assembly 14 and an impactor assembly 16. The three parts are indicated by differing hashed lines for each part. The three parts may be formed from a polymeric material, for example glass filled nylon, formed by injection moulding. It will be appreciated that the separator could be formed in other embodiments from a differing number of components, and other suitable materials and production techniques are well known to the skilled person. For instance, the inlet assembly 12, or just the nozzle 18 could be made from sintered or injection moulded metal. The three parts are joined together using appropriate known fixing techniques, such as bolts, adhesive or welding. Seals 28 may be required between each part in order to prevent leakage.

Pressurised boost gas enters the separator via boost gas inlet 6. When used on a turbocharged engine the pressurised gas may be derived from the intake manifold. Alternatively, the pressurised gas could be derived directly from the turbocharger, however it is preferable to derive the air from the intake manifold as at this stage the turbocharger gas has passed through a heat exchanger (alternatively referred to as an intercooler) so that it is cooled from approximately 180-200⁰C to 50-60⁰C. Using cooler boost gas allows the separator to be formed from lower cost materials which do not need to be resistant to such high temperatures. Alternatively, exhaust gas derived from before or after the turbocharger may be used as the boost gas. The boost gas typically is at a pressure of between IBar and 4Bar.

The boost gas passes through nozzle 18, which accelerates the boost gas (and causes a consequent reduction in pressure). The nozzle 18 is formed as a convergent nozzle. In particular, the nozzle may be a convergent-divergent nozzle, such as a de-Lavaal nozzle, which is well known in the art. Other suitable nozzle shapes are known. The boost gas is accelerated to a high velocity, for instance between 100-500m.s^~', with the boost gas typically exceeding mach 1 at least in the region of nozzle 18. A convergent nozzle advantageously accelerates the boost gas to very high speeds, which consequently entrains the blow-by gas and accelerates the blow-by gas to high speeds. Furthermore, use of convergent nozzle advantageously results in a high degree of intermixing between the boost gas and the blow-by gas, resulting in improved separation of contaminants from the blow-by gas.

The resultant high speed boost gas jet passes into chamber 20 along the axis of the device indicated by line 22, which passes through the centre of boost gas inlet 6. The high velocity boost gas jet causes a region of reduced pressure within the chamber 20 in the vicinity of the nozzle 18. Pressure is reduced by up to 150mBar relative to external atmospheric pressure. This reduction in pressure allows contaminated blow-by gas to be drawn in though annular nozzle 24, which surrounds nozzle 18. Annular nozzle 24 is in communication with annular space 26 that surrounds chamber 20 and is in turn in communication with blow-by gas inlet 2. Therefore, blow-by gas is sucked into chamber 20 through annular nozzle 24, which provides an annular flow of blow-by gas about the high speed boost gas jet. The blow-by gas flow is parallel to the boost gas flow, which aids the entrainment of the blow-by gas The relatively low speed blow-by gas is entrained by the high speed boost gas jet, intermixing with the boost gas and accelerating to approach the speed of the boost gas. Annular nozzle 24 assists the entrainment, mixing and acceleration of the blow-by gas by surrounding the high speed boost gas jet which results in a greater proportion of the gas streams being in contact with one another.

Advantageously for use within an engine, the contaminated blow-by gas is actively drawn out of the crankcase and into the separator, allowing for control of the pressure within the crankcase. The pressure within the crankcase is thus typically controlled to within +/- 50mBar relative to external atmospheric pressure. The generated suction may be separately controlled by providing a pressure control valve connected to the blow-by gas inlet 4, or elsewhere connected to the engine. Alternatively, if the separator would otherwise keep the pressure within the crankcase too low then an impaction stage may be provided in the blow-by inlet 4 to reduce the pressure drop in the crankcase. The additional impaction stage may simply comprise an additional 90° turn within the blow-by inlet 2 or annular space 26. As will be described in greater detail below, the additional impaction stage within the blow-by gas inlet may in fact comprise the primary impaction surface for filtering contaminants from the blow-by gas. That is, the boost gas nozzle 18 is arranged to draw blow-by gas into the chamber such that it is incident upon an impaction surface before the gas streams are combined in order to separate out contaminants.

Referring now to figure 3, this is an enlarged portion of the cross sectional view of figure 2, illustrating the nozzle 18 and chamber 20 in greater detail. The boost gas nozzle 18 and annular blow-by gas nozzle 24 are generally constructed as for a jet pump, as is known in the art. In order to achieve satisfactory entrainment and acceleration of the blow-by gas, preferably the diameter of chamber 20 indicated by arrow 30 should be between 2 to 5 times greater, preferably 3 to 4 times greater, than the critical diameter (typically, the smallest diameter) of boost gas nozzle 18 indicated by arrow 32. The position of the critical diameter (alternatively referred to as the throat of the nozzle) may vary from the narrowest point of the nozzle due to aerodynamic effects, as is known in the art of nozzle design.

The chamber 20 is generally formed as a cylinder, however side walls 34 are not straight for the whole of their length. It can be seen from figure 3 that sides walls 34 taper inwardly towards the end of the chamber remote from nozzle 18. This tapering assists in controlling the direction of flow and mixing of the combined gas flow. In order for separators in accordance with embodiments of the present invention to efficiently separate contaminants from blow-by gas, it is desirable that the degree of intermixing of the gas flows is maximised.

The tapering additionally serves to create a vortex within the combined gas flow as entrained blow-by gas and boost gas passes back along the side walls 34 of chamber 20 towards the annular nozzle 24. The vortex appears within the curved section of the chamber as a result of the flow conditions. The boost gas jet is in an axial direction along the centre of chamber 20 towards the impaction plate 36. Blow-by gas entering through annular nozzle 24 is entrained and drawn towards the boost gas jet as a result of the pressure drop around nozzle 18. However, due to the viscosity of the blow-by gas this motion sets up a rotating vortex. Even if the side walls of the chamber 20 are straight, a vortex may appear, however the strength of the vortex is affected by the geometry of the chamber, and increased by curved side walls. The vortex is occurs withm planes that include the axis of the separator passing through the boost gas nozzle towards the impaction plate This differs from the plane of the vortex withm a centrifugal or cyclone separator known m the art which typically is in a plane transverse to the axis of the gas entering a cyclone chamber and rotating about a central axis of the device.

The vortex further encourages the gas streams to mix and increases the acceleration of the blow-by gas allowing the blow-by gas portion of the combined gas flow to approach the speed of the boost gas jet. It has been observed that the vortex results in the contaminants beginning to separate withm chamber 20. There may also be some initial separation of contaminants as a result of the mixing of the high speed boost gas and the lower speed blow-by gas stream

The combined gas flow is incident upon impaction plate 36 at the end of chamber 20 remote fiom nozzle 18. The impaction plate 36 is transverse to the flow of gas, and preferably at approximately 90° to the gas flow. The combined gas flow is forced to turn through 90° to pass round impaction plate 36 to pass through annular space 38. This turning causes particulate and liquid contaminants to be impacted on the surface of the plate The gas passing through annular space 38 then undergoes a second 90° bend passing around impaction plate 36 into collection space 40 (see figure 2). The second 90° bend also serves to separate out contaminants. The contaminants then flow under gravity towards oil dram 8 where they can be extracted. The oil can be returned to the crankcase, or stored separately. The cleaned gas stream passes out of the separator through blow-by gas outlet 4 The degree of separation is significantly higher than that encountered for blow-by gas streams incident upon an impaction plate without acceleration using a boost gas While impaction plate 36 is illustrated as being flat (at least in the surface facing nozzle 18) this need not necessarily be the case. For instance, the impaction plate may be curved such that it presents a convex or a concave surface towards nozzle 18. A curved surface may increase the separation efficiency for certain embodiments of the present invention OiI within the gas stream as an aerosol is coalesced by impaction on the impaction plate 36. Additionally oil is coalesced on the outer wall of the collection space at the second 90° bend. The second 90° bend contributes significantly to the efficiency of the separator as determined by the percentage of oil within the blow-by gas stream that is removed. When the gas passes into collection space 40 coalesced oil is encouraged to drain away to oil drain 8 by being flung against curved wall 42. A check valve may be provided in oil drain 8, as is commonly found in conventional oil separators. Similarly, a pressure regulator connected to the blow-by gas outlet 4 may be provided before passing back to the engine air intake manifold.

Separators according to the above described embodiments of the present invention have been observed to provide gravimetric separation efficiency in the range 95-98% for particles greater than or equal to 0.3μm. It is possible that smaller particles still may be efficiently filtered.

Embodiments of the present invention adapted to filter contaminants from blow-by gas in a closed loop system typically operate with a flow of blow-by gas of 50-800 1/min. For higher flow rates within this range it can be desirable to combine two or more separators to achieve the required flow rate. Increased flow rates can be accommodated by increasing the size of the nozzle 18 and chamber 20.

The flow of boost gas through nozzle 18 when using boost gas derived from the turbocharger of an engine typically comprises less than 1% of the total engine gas flow, so as to have a negligible effect on engine performance. Referring to figure 4, this is a graph illustrating the variation of engine output power with engine speed for an exemplary engine firstly without a separator fitted (the line indicated by diamonds), and secondly with a separator in accordance with an embodiment of the present invention fitted to extract contaminants from a blow-by gas stream (the line indicated by squares). It can be seen that there is a negligible difference between the two plotted lines, the difference between the two lines being less than the measurement error for the power measurements. As an example, a 6 litre diesel engine consumes approximately 19800-22700 litres per minute (700-800 cubic feet per minute - CFM) of air when running at maximum rated power and speed. The maximum rated power is the engine speed at which the engine develops the maximum power. For such an engine, nozzle 18 typically varies between 0.5 and 15mm according to the amount of blow-by gas to be cleaned.

Referring now to figure 5 this schematically illustrates a separator 50 in accordance with an embodiment of the present invention used in a closed loop application in combination with a reciprocating engine in order to extract contaminants from blow-by gas derived from a crankcase. Air filter 52 draws in external air (line 54) and filters the air before passing the air to a turbocharger 56 (line 58). The turbocharged air then passes to intercooler 60 (line 62) where it is cooled before passing to the air intake manifold of engine 64 (line 66). Exhaust gases from engine 66 are passed back to the turbocharger 56 (line 68) where they are used to drive the turbocharger 56. Blow-by gases from the crankcase of engine 64 pass to separator 50 (line 70). Separator 50 also receives a small volume of air from the turbocharger 56 (line 72) which serves as the boost gas. Cleaned blow-by gas is returned to the air intake of turbocharger 56 (line 74) and the separated oil is returned to the crankcase of engine 64 (line 76). In alternative embodiments of the present invention the cleaned blow-by gas may be returned to the intake of air filter 52 such that the blow-by gas is subjected to further filtering prior to being passed to the air intake manifold of engine 64.

In accordance with embodiments of the present invention, a vacuum limiting valve may be coupled to a gas outlet from the separator in order to prevent cleaned gas from being drawn back into the separator. Additionally, a pressure regulation valve may be coupled to the blow-by gas inlet to prevent gas being drawn out of the separator into the crankcase. Furthermore, a check valve may be coupled to the oil drain to prevent oil being drawn into the separator from the crankcase, or wherever the separated oil is stored, through the oil drain.

It will be appreciated that the system illustrated in figure 5 may be modified. For instance, the boost gas may be derived from the exhaust of engine 64 (line 68). Cleaned blow-by gas may similarly be passed to be combined with the exhaust gases (line 68). Separated oil may be stored separately and not returned to the crankcase of engine 64. Other possible configurations will be readily apparent to the appropriately skilled person. Referring now to figure 6, this is a perspective view of a separator in accordance with a second embodiment of the present invention for separating liquid, aerosol and particulate contaminants from a blow-by gas stream. Where the separator illustrated in figure 6 shows features corresponding to those identified for the separator illustrated in figure 1 , the same reference numerals have been used.

The separator comprises a blow-by gas inlet 2, a cleaned blow-by gas outlet 4, a boost gas inlet 6 and an oil drain 8. The boost gas comprises a pressurised gas source, which may be either pressurised air (for instance from a turbocharger) or exhaust gas. The oil drain 8 allows separated oil and other contaminants to be extracted, either to be returned to the engine crankcase or stored in another chamber. Each of the inlets and outlets are suitable for connection to hoses for transfer of the various fluids to or from the engine or other devices. Flanges 10 are provided on each inlet or outlet to assist in attaching hoses. The separator further comprises a cyclone main body 50 and a cyclone lid 52, as will be described in greater detail below.

Referring to figure 7, this illustrates in cross section the separator of figure 6 through a plane passing through the axis of each gas inlet. That is, the cross section of figure 7 is in a plane that is positioned passing transversely through the main cyclone body 50 underneath the cyclone lid 52. The separator is formed from three parts: a boost gas inlet assembly 54, a blow-by gas and cyclone assembly 56 and the cyclone lid 52 (not illustrated in figure 7). The separator parts are indicated by differing hashed lines for each part. The separator may be formed from similar materials and using similar production techniques as those described above in connection with the first embodiment of the separator illustrated in figures 1 to 3.

Pressurised boost gas enters the separator via boost gas inlet 6, derived from the same sources as described above for the first embodiment of the separator.

The boost gas passes through nozzle 18, which accelerates the boost gas (and causes a consequent reduction in pressure). The nozzle 18 is formed as a convergent nozzle. In particular, the nozzle may be a convergent-divergent nozzle, such as a de-Lavaal nozzle, which is well known in the art. Other suitable nozzle shapes are known. The boost gas is accelerated to a high velocity, for instance between 100-50OmS^"1, with the boost gas typically exceeding mach 1 at least in the region of nozzle 18.

The resultant high speed boost gas jet passes into mixing chamber 58 along the axis of nozzle 18 indicated by line 60, which passes through the centre of boost gas inlet 6. The high velocity boost gas jet causes a region of reduced pressure within the chamber 58 in the vicinity of the nozzle 18. Pressure is reduced by up to 150mBar relative to external atmospheric pressure. This reduction in pressure allows contaminated blow-by gas to be drawn in though annular nozzle 24, which surrounds nozzle 18. Annular nozzle 24 is in communication with annular space 26 that surrounds chamber 20 and is in turn in communication with blow-by gas inlet 2. Therefore, blow-by gas is sucked into chamber 20 through annular nozzle 24, which provides an annular flow of blow-by gas about the high speed boost gas jet. The blow-by gas flow is parallel to the boost gas flow, which aids the entrainment of the blow-by gas The relatively low speed blow-by gas is entrained by the high speed boost gas jet, intermixing with the boost gas and accelerating to approach the speed of the boost gas.

As for the first embodiment of the separator, the contaminated blow-by gas is actively drawn out of the crankcase and into the separator, allowing for control of the pressure within the crankcase. The pressure within the crankcase is thus typically controlled to within +/-50mBar relative to external atmospheric pressure. As before, the generated suction may be separately controlled by providing a pressure control valve connected to the blow-by gas inlet 4, or elsewhere connected to the engine or an impaction stage in the blow-by inlet 4 to reduce the pressure drop in the crankcase.

As for the first embodiment, the boost gas nozzle 18 and annular blow-by gas nozzle 24 are generally constructed as for a jet pump, as is known in the art. In order to achieve satisfactory entrainment and acceleration of the blow-by gas, preferably the diameter of chamber 58 indicated by arrow 62 should be between 2 to 5 times greater, preferably 3 to 4 times greater, than the critical diameter (typically, the smallest diameter) of boost gas nozzle 18 indicated by arrow 64 The position of the critical diameter (alternatively referred to as the throat of the nozzle) may vary from the narrowest point of the nozzle due to aerodynamic effects, as is known in the art of nozzle design. The chamber 58 is generally formed as a cylinder, however side walls 34 need not be straight for the whole of their length. Tapering may assist in controlling the direction of flow and mixing of the combined gas flow. The tapering can additionally serve to create a vortex within the combined gas flow as entrained blow-by gas and boost gas passes back along the side walls of chamber 58 towards the annular nozzle 24.

The combined gas flow passes into cyclone chamber 66, defined by cyclone body wall 50 and cyclone lid 52. The curved inside surface of cyclone body wall 50 cause the combined gas flow to change direction and spiral towards the bottom of the cyclone, as indicated by the arrows 68. This change in direction causes particulate and liquid contaminants to be impacted on the inside surface of cyclone body wall 50. As the combined gas jet enters the cyclone chamber 66 it is still travelling at a high speed (generated by nozzle 18). This high speed gas jet creates a significant increase in separation efficiency, compared to conventional cyclone separators. As the combined gas stream passes further into the cyclone and spirals downwards the energy in the gas stream dissipates partly and the gas stream slows.

Referring now to figure 8, this illustrates the separator of figure 6 is cross section through the cyclone 66 and the gas outlet 4 and contaminant outlet 8. The combined airstream passes into cyclone 66 and spirals downwards. Cleaned gas then passes upwards through passage 70 that connects with gas outlet 4. Gas outlet 4 may connect with that engine air intake. Contaminants that have been separated from the gas stream by impacting upon the main cyclone body wall 50 then flow under gravity towards oil drain 8 where they can be extracted. The oil can be returned to the crankcase, or stored separately. The degree of separation is significantly higher than that encountered for blow-by gas streams entering a cyclone without acceleration using a boost gas.

Oil within the gas stream as an aerosol is coalesced by impaction on the cyclone body wall 50. A check valve may be provided in oil drain 8, as is commonly found in conventional oil separators. Similarly, a pressure regulator connected to the blow-by gas outlet 4 may be provided before passing back to the engine air intake manifold. Embodiments of the present invention described above utilise a jet of boost gas passing through and accelerated by a nozzle in order to create a region of low pressure which draws in blow-by gas. The blow-by gas is entrained by the boost gas jet and accelerated towards an impaction surface. However, under certain conditions, for a separator coupled to a vehicle engine, the boost gas supply may be interrupted. The requirement to separate contaminants from the blow-by gas may continue even without the presence of the boost gas jet,

Referring now to figure 9, this is a cross sectional view of a separator in accordance with a third embodiment of the present invention for separating liquid, aerosol and particulate contaminants from a blow-by gas stream. The separator is operable to separate contaminants from blow-by gas even when the boost gas jet is interrupted. The separator illustrated in figure 9 is generally similar to the separator illustrated in figure 2, although the view is reversed such that the boost gas enters through boost gas inlet 6 on the right of figure 9. Where features are not explicitly explained to be different from the corresponding features of figures 1 to 3 it may be assumed that they are designed, constructed and operated in a similar manner. Where the separator illustrated in figure 9 shows features corresponding to those identified for the separator illustrated in figure 1 , the same reference numerals have been used.

The separator of figure 9 comprises a blow-by gas inlet 2, a cleaned blow-by gas outlet 4, a boost gas inlet 6 and an oil drain 8. As for the first and second embodiments of the present invention, the boost gas comprises a pressurised gas source, which may be either pressurised air (for instance from a turbocharger) or exhaust gas. The boost gas need not be at a high velocity on entering the boost gas inlet. The oil drain 8 allows separated oil and other contaminants to be extracted, either to be returned to the engine crankcase or stored in another chamber. Each of the inlets and outlets are suitable for connection to hoses for transfer of the various fluids to or from the engine or other devices. Flanges 10 are provided on each inlet or outlet to assist in attaching hoses. The construction of the separator of figure 9 may in general be the same as for the separator of figure 1.

The boost gas passes through nozzle 18, which accelerates the boost gas (and causes a consequent reduction in pressure). The nozzle 18 may be generally the same as for the nozzle of figure 2. The resultant high speed boost gas jet passes into chamber 20. The high velocity boost gas jet causes a region of reduced pressure within the chamber 20 in the vicinity of the nozzle 18. This reduction in pressure allows contaminated blow-by gas to be drawn in though annular nozzle 24, which surrounds nozzle 18. Annular nozzle 24 is in communication with annular space 26, which surrounds chamber 20 and is in turn in communication with blow-by gas inlet 2. Therefore, blow-by gas is sucked into chamber 20 through annular nozzle 24, which provides an annular flow of blow-by gas about the high speed boost gas jet. The relatively low speed blow-by gas is entrained by the high speed boost gas jet, intermixing with the boost gas and accelerating to approach the speed of the boost gas. The acceleration and intermixing of the blow-by gas within chamber 20 is generally the same as for the first described embodiment of the present invention.

The combined gas flow is incident upon impaction plate 36 at the end of chamber 20 remote from nozzle 18. The combined gas flow is forced to turn through 90° to pass round impaction plate 36. This turning causes particulate and liquid contaminants to be impacted on the surface of the plate. The gas then undergoes a second 90° bend passing around impaction plate 36 into collection space 40. The second 90° bend also serves to separate out contaminants. The contaminants then flow under gravity towards oil drain 8 where they can be extracted. The oil can be returned to the crankcase, or stored separately. The cleaned gas stream passes out of the separator form the collection space 40 through blow- by gas outlet 4.

As described so far, the operation of the separator of figure 9 is the same as for the separator of figures 1 to 3. Boost gas is supplied via the boost gas inlet 6 from the turbocharger. However, when the vehicle engine is idling, or under engine braking conditions, the supply of boost gas to the boost gas inlet 6 is reduced. The jet pumping effect is reduced or interrupted completely. Figure 9 differs from figure 2 in that the impaction plate 36 is mounted upon a spring 80, which is coupled between the impaction plate 36 and a mount 82 extending from the side walls of collection space 40. Impaction plate 36 is biased by spring 80 towards the boost gas inlet 6. Figure 9 illustrates the separator in a first mode of operation in which, under engine idle conditions, the impaction plate 36 is pressed hard against shoulder 84 at the end of chamber 20 by the spring 80. The annular space between impaction plate 36 and shoulder 84 is reduced to a minimum in figure 9. The minimum gap available is preserved by castellations 86 upon the impaction plate 36 which prevent the annular gap being completely sealed off. The castellations 86 comprise lugs that space the impaction surface 36 apart from the shoulder 84. Typically, the impaction surface 36 may be circular. The castellations 86 may be spaced apart around the impaction surface 36. The castellations may vary in number and typically will be arranged to occupy only a small proportion of the periphery of the impaction surface. The size of each castellation, that is the gap they preserve between the impaction surface and the shoulder, is chosen to allow for adequate separation of contaminants from blow-by gas for the particular application of the separator under engine idle conditions. That is, the minimum size of the annular gap surrounding impaction surface 36 is determined by the minimum flow rate of blow-by gas from the crankcase and can be adjusted by varying the size of castellations 86. It will be appreciated that in some embodiments the castellations may be omitted such that the annular gap around the impaction surface is completely sealed when the flow rate of blow-by gas under engine idle conditions reduces below a predetermined level (set by the force provided by the spring). Alternatively, the minimum gap between the shoulder and the impaction surface may be preserved by limiting the travel of the impaction surface in some other way.

As before, the blow-by gas undergoes a first 90° turn when it is incident upon the impaction plate 36. It then undergoes a second 90° turn to pass around the impaction surface 36 into the collection space 40. An open media may be provided within the collection space to further improve the separation efficiency by reducing the re- entrainment of contaminants.

Under engine idle conditions, where the reduced boost gas supply results in little or no jet pumping effect, reducing the size of the annular gap around the impaction surface increases the separation efficiency and allows for gravimetric efficiency of greater than 65% based on measuring the separation of all particles.

Referring now to figure 10, once the supply of boost gas is restored, the separator changes to a second mode of operation in which the jet of boost gas incident upon the impaction surface 36 overcomes the resistance of the spring 80. The size of the annular gap surrounding the impaction surface is increased. Under the conditions of figure 10 the separator functions in substantially the same manner as that illustrated in figures 1 to 3. The spring rate of spring 80 may be optimised to allow the annular gap around the impaction plate 36 to be increased proportionally with the flow of boost gas.

Figure 11 illustrates spring mounted impaction surface in the closed condition of figure 9. It can be seen that when fully closed the castellations 86 allow the combined boost gas and blow-by gas to flow through a plurality of slots formed between pairs of adjacent castellations 86.

Under engine idle conditions the flow rate of blow-by gas is reduced. Spring 80 forces the impaction surface 36 against shoulder 84 reducing the annular gap to a minimum as illustrated in figure 9, which serves to maximise the separation of contaminants from the reduced flow of blow-by gas. However, during engine braking conditions, in addition to the supply of boost gas being reduced, the flow rate of the blow-by gas may increase significantly, for instance it may double or triple. As the flow rate of the blow-by gas increases, this can provide sufficient energy to overcome the resistance of the spring 80, thereby pushing back impaction surface 36 and increasing the size of the annular gap around the impaction surface as illustrated in figure 10. The variable annular gap prevents the pressure within the crankcase from exceeding beyond predetermined levels under engine braking conditions in which there is no boost gas to draw the blow-by gas from the crankcase. It will be appreciated that a spring mounted impaction surface able to adjust the size of an annular gap surrounding the impaction surface to maximise the separation efficiency for a variable flow rate supply of blow-by gas may be applied to other filters where there is no supply of boost gas to accelerate the blow-by gas under engine running conditions.

The collection space 40 illustrated in figures 9 and 10 comprises a series of baffles 88 in the end of the collection space 40 remote from the boost gas inlet 6. Additionally, baffles 90 are provided extending around spring 80. The baffles assist in preventing coalesced oil from being re-entrained within the cleaned blow-by gas stream. Figure 12 illustrates baffles 88 formed on an end plate of the collection space 40. The baffles 88 form a series of concentric rings having slots formed in the lower part of each ring to allow oil to drain away to the oil drain 8. As cleaned gas is incident upon the end plate of the collection space 40 the baffles prevent coalesced oil from being driven upwards towards the cleaned blow-by gas outlet 4.

For the embodiments of the present invention described above, the primary separation occurs when the combined gas stream is incident upon an impaction surface. That is, the boost gas jet draws blow-by gas from the crankcase, which is then entrained and mixed with the boost gas jet before the primary separation takes place. However, in alternative embodiments of the present invention, the boost gas continues to draw blow-by gas from the crankcase, however before the gas streams intermix the accelerated blow-by gas stream is incident upon an impaction surface. This may comprise the primary separation stage, with further separation occurring in a similar manner to that described above once the combined gas stream has been formed. In some embodiments, there may be little or no separation after the combined gas stream has been formed.

Referring now to figure 13, this is a perspective view of a separator in accordance with a fourth embodiment of the present invention for separating liquid, aerosol and particulate contaminants from a blow-by gas stream. The separator illustrated in figure 13 is similar to the separator illustrated in figures 1 to 3. Where features are not explicitly explained to be different from the corresponding features of figures 1 to 3 it may be assumed that they are designed, constructed and operated in a similar manner. Where the separator illustrated in figure 13 shows features corresponding to those identified for the separator illustrated in figure 1 , the same reference numerals have been used.

The separator of figure 9 comprises a blow-by gas inlet 2, a cleaned blow-by gas outlet 4, a boost gas inlet 6 and an oil drain 8. As for the first, second and third embodiments of the present invention, the boost gas comprises a pressurised gas source, which may be either pressurised air (for instance from a turbocharger) or exhaust gas. The boost gas need not be at a high velocity on entering the boost gas inlet. The oil drain 8 allows separated oil and other contaminants to be extracted, either to be returned to the engine crankcase or stored in another chamber. Each of the inlets and outlets are suitable for connection to hoses for transfer of the various fluids to or from the engine or other devices. Flanges 10 are provided on each inlet or outlet to assist in attaching hoses. The construction of the separator of figure 13 may in general be the same as for the separator of figure 1. The separator may typically be made in four to five sections from a polymeric material, for example glass filled nylon. Other constructions and materials will be readily apparent to the appropriately skilled person. For example, the nozzle section forming part of boost gas inlet 6 may be made from a sintered or metal injection moulded part. The various parts of the separator may be joined together using appropriated fixing techniques, which will be well know to the skilled person, such as clips, bolts, adhesive or welding. Seals such as O-rings may be provided to prevent leakage from the separator.

Referring to figure 14, this illustrates in cross section the separator of figure 13 in a plane passing through the axis of each inlet or outlet. The boost gas passes through nozzle 18, which accelerates the boost gas (and causes a consequent reduction in pressure). The nozzle 18 may be generally the same as for the nozzle of figure 2. The resultant high speed boost gas jet passes into chamber 20. The high velocity boost gas jet causes a region of reduced pressure within the chamber 20 in the vicinity of the nozzle 18. This reduction in pressure allows contaminated blow-by gas to be drawn in though annular nozzle 24, which surrounds nozzle 18. Annular nozzle 24 is in communication with annular space 26, which surrounds chamber 20 and is in turn in communication with blow-by gas inlet 2. Therefore, blow-by gas is sucked into chamber 20 through annular nozzle 24, which provides an annular flow of blow-by gas about the high speed boost gas jet. The relatively low speed blow-by gas is entrained by the high speed boost gas jet, intermixing with the boost gas and accelerating to approach the speed of the boost gas. The acceleration and intermixing of the blow-by gas within chamber 20 is generally the same as for the first described embodiment of the present invention.

When the engine is operating, boost gas enters the separator through inlet 6. The pressurised boost gas may be compressed air from the intake manifold of a turbocharged engine. The boost gas could be derived directly from the turbocharger however it is desirable to take the air from the manifold as the air will typically pass through a heat exchanger (a charge air cooler) where it will be cooled from 180-200⁰C to 50-60°C which aids the use of lower cost materials in the construction of the separator. Alternatively, exhaust gas from before or after the turbocharger may be used as the boost gas. The boost gas typically is pressurised to between lbar and 4bar. Higher pressure boost gas could be used if available within the engine. For alternative embodiments of the present invention in which the separator is not coupled to a vehicle engine, the boost gas may be provided from other systems.

The boost gas passes through the nozzle 18 causing the pressure to drop and the velocity to increase substantially. The nozzle is typically a de-Laval or convergent-divergent nozzle design, although alternative nozzle forms available to the skilled person may be used. The boost gas is accelerated to high speeds between, typically lOOm.s^"1 to 500 m.s^"1. Typically the boost gas will achieve sonic velocity in the nozzle 18 with mach numbers of approximately 1 or slightly higher.

The resultant gas jet passes through chamber 20 towards the blow-by gas outlet 4. The high velocity jet of boost gas lowers the pressure within chamber 20 causing a jet pumping effect as blow-by gas is drawn in and entrained along with the boost gas. The blow-by gas is drawn in through the blow-by inlet 2 into the inlet annular space 26. Advantageously, for embodiments of the present invention which are coupled to a vehicle engine, as the contaminated blow-by gas is actively drawn into the system pressure in the crankcase is not elevated and can be controlled to a desired level. Typically, the pressure within the crankcase may be controlled such that it is slightly above or below atmospheric pressure, for instance -50mBar to 50mBar about atmospheric pressure. In alternative embodiments of the present invention, suction of blow-by gas into annular chamber 26 may be controlled by an integrated pressure control valve or a valve situated elsewhere on the engine. Alternatively, additional impaction stages could be included in the blow-by inlet of the system.

The blow-by gas drawn into chamber 20 by the jet pump first passes through a pre impaction gap 100. Coalescent media may be provided within the pre impaction gap 100 to aid the entrapment of contaminants, and so increase the overall efficiency of the separator. The impaction gap 100 forces the gas to make a 90° turn and reduces the pressure of the blow-by gas. The impaction gap 100 functions as a convergent nozzle and increases the velocity of the blow-by gas. The blow-by gas is then accelerated into an impaction surface 102 and passes around a second 90° bend which causes contaminants to be separated from the blow-by gas. In alternative embodiments further bends may be provided encouraging further separation. For embodiments of the present invention used as oil separators, for instance on a diesel engine, the oil is coalesced from being aerosol particles to being liquid oil which can then be directed by gravity towards the drain 8.

Contaminants separated by striking the impaction surface 100 collect within a first oil sump 104. The oil is then allowed to drain through oil drain 106 which directs the oil to a second oil sump 108. The oil within second oil sump 108 drains through a second oil drain 110 which extends lower than a third oil sump 112 at the bottom of the separator to prevent re-entrainment of oil into the cleaned gas flow. The second oil drain 110 communicates with the main separator oil drain 8 and exits the separator.

In the event of an engine braking condition, as discussed above the supply of boost gas is reduced resulting in a reduction or interruption of the suction of blow-by gas from the blow-by gas inlet 2. Furthermore, under engine braking conditions the blow-by gas flow rate increases. To accommodate the increase flow of blow-by gas, one or more bypass valves 114 are provided within annular space 26 to allow excess blow-by gas to bypass the initial impaction surface 102. Blow-by gas passing through the or each bypass valve 114 and enters chamber 116. The blow-by then passes through a second pre-impaction gap 118 passing into oil drain 106 where it incident upon the side of the oil drain 106 causing separation of contaminants. Separation efficiency is maintained at high levels and pressure in the engine is prevented from exceeding a predetermined level, according to the parameters of the pressure release bypass valve 1 14. Separated oil from the bypass section collects within the second oil sump 108 and drains from the separator as described above through the second oil drain 110. It will be appreciated that in some embodiments of the present invention the bypass channel provided by bypass valves 116 may not be required.

Any oil which is re-entrained in the gas flow past impaction gap 100 within chamber 20 is accelerated by the boost gas jet. The chamber 20 passes through the centre portion of the separator. A narrowed portion 124 of the chamber 20 serves to increase the velocity of the combined gas stream as the combined gas stream exits the narrowest portion. The combined gas stream is incident upon a third impaction surface 120 within the third oil sump 112. Advantageously the third impaction surface causes further separation of contaminants from the combined gas stream which have not already been removed by the blow-by gas passing through impaction gap 100. The third impaction surface 120 causes a change in flow direction as the combined gas stream passes upwards around second oil sump 108 to the gas outlet 4. The change in flow direction reduces the re-entrainment of oil within sump 1 12. Oil which has collected within the third oil sump drains through the oil outlet 8. Cleaned blow-by gas passes upwards through slots around the second oil sump 108 (not shown in figure 14) and passes out through the blow-by gas outlet 4.

Baffles 122 are provided within the third oil sump 112 to prevent the flow of cleaned gas from entraining oil droplets. The baffles 122 direct the gas flow and liquid oil toward the drain. The drained oil exiting the separator through outlet 8 may be stored separately or returned to the crank case as discussed above in connection with figure 5.

It will be appreciated that the separator illustrated in figures 13 and 14 may be varied, for instance by incorporating features of the other embodiments of the present invention described above. For instance, further impaction surfaces may be provided to increase the separation efficiency. Within chamber 20 curved walls or spiral inserts may be provided to encourage centrifugal separation. Open filter media may be provided, which may be advantageous in some instances to increase the separation efficiency. Furthermore, tighter filter media may be provided for extremely high separation efficiency (>99%). It will be appreciated that if a tight filter media is provided then this may mean that the separator requires periodic servicing to replace the media.

Embodiments of the present invention in accordance with figures 13 and 14 have been shown to have a gravimetric efficiency in the range 95-99% based on measuring all particles down to a size of 0.3 microns. For vehicle engine applications of the embodiment of the present invention illustrated in figures 13 and 14, when acting as a closed system (that is, the cleaned blow-by gas is returned to the turbocharger) the separator may operate with flows between 501 to 8001 per minute. Alternatively, a series of separators operating in parallel may be provided to increase the flow rate of blow-by gas which can be accommodated. For larger flows a larger nozzle and body may be required, which can be achieved scaling the separator illustrated in figures 13 and 14. Advantageously, for separators in accordance with figures 13 and 14, providing impaction of the blow-by gas stream before the two gas streams are mixed results in the majority of contaminants being removed before the combined gas stream is formed. Consequently, when the combined gas stream is incident upon the third impaction surface 120, relatively little separation is still required. Therefore, the gap through which the combined gas stream passes to reach the gas outlet 4 need not be as narrow, as is the case for the first and third embodiments of the present invention described above in connection with figures 1 to 3 and 9 to 12. The reduced restriction on gas flow exiting the separator allows for an improved jet pumping effect. In particular, the flow of boost gas may be increased, allowing greater suction of blow-by gas from the blow-by gas inlet 2. In turn, the increased flow rate of the blow-by gas allows for increased separation efficiency at the first impaction surface 102.

Preferably, the flow of boost gas through the nozzle, when using compressed air from the turbocharger, is less than 1% of the total engine volume flow so as to have a negligible effect on engine performance. As an example, a 6 litre diesel engine will consume approximately 700-800 Cubic Feet per Minute (CFM) of air when running at a rated power condition. The proportion of this air flow drawn off as boost gas can be controlled by varying the size of the nozzle. Typically, the nozzle may be between 0.5mm and 15mm in diameter according to the size of the engine and the amount of contaminated blow-by gas to be treated. Pressure in the jet chamber 20 may be reduced by 150mBar according to the system geometry.

When used in connection with separating contaminants from a blow-by gas stream derived from an internal combustion engine the separators described above may be modified by providing the separator with suitable attachments for connecting to an engine. Alternatively, the separator may be integrated with part of an engine, for instance an air intake manifold or the oil drain. Means for coupling the separator to an engine will be readily apparent to the appropriately skilled person.

The separator described above may be modified by adding further bends through which the gas must pass after the impaction surface, if further separation is required. Similarly, to increase the separation efficiency, other features may be provided such as further impaction plates and curved walls or spiral inserts within the chamber to encourage centrifugal separation. Providing an open filter medium (which is not subject to clogging due to the degree of openness) within the collection space or within the cyclone chamber can improve separation efficiency by providing a surface on which the oil can coalesce, and reducing the amount of re-entrainment of separated contaminants. For applications in which an extremely high degree of separation (greater than 99%) is required, a tighter filter medium can be provided in collection space. Such a tighter filter medium may require periodic replacement.

Although particular embodiments of the present invention described above relate primarily to the use of the described separator for separating particulate and liquid aerosol contaminants from a blow-by gas stream within a reciprocating engine, the present invention is not limited to this. Indeed, the separator can be used to separate contaminants from a gas stream derived from other forms of internal combustion engine. More generally, the present invention can be applied to separate contaminants from any gas stream, such as compressed air lines, separating cutting fluid from gas streams in machine tools and separating oil mist in industrial air compressors. More generally still, the present invention can be used to separate contaminants from any fluid stream. That is it may also be applied to liquid streams. The separator may be advantageously used to separate contaminants from an oil fuel supply within an internal combustion engine. The separator can be used in both open loop systems where the cleaned fluid stream is vented to the atmosphere, or in closed loop systems where the cleaned fluid stream is reused.

The boost gas can be derived from any source of pressurised gas, for instance exhaust gas, compressed gas from a turbocharger or an engine intake manifold, compressed gas from a vehicle braking system or other sources.

Embodiments of the present invention described above relate to an impaction plate or a cyclone. However, the present invention is not limited to these two examples. In its broadest sense, as defined by the claims, the invention comprises means for accelerating a fluid stream using a second fluid stream which passes through a convergent nozzle which accelerates the second fluid stream. The accelerated jet of the second fluid entrains and accelerates the first fluid stream, intermixing with the first fluid stream. The combined fluid stream is then incident upon some form of surface which causes a change in direction in the combined fluid stream, resulting in separation of contaminants due to a centrifugal effect. Separation efficiency is increased relative to separator assemblies known in the art due to the high degree of acceleration provided by the nozzle assemblies described above.

The separator may comprise a stand alone device. Alternatively, it may readily be integrated into other engine components, for example an engine valve cover, timing cover, crankcase, cylinder head, engine block or turbocharger. The separator may be mounted directly on the engine, or mounted away from the engine.

Further modifications and applications of the present invention will be readily apparent to the appropriately skilled person, without departing from the scope of the appended claims.

Claims

CLAIMS:

1. A separator for separating contaminants from a fluid stream, comprising: a chamber; a first inlet for receiving a first fluid stream into the chamber including a convergent nozzle for accelerating the first fluid stream; a second inlet for receiving a second fluid stream including entrained contaminants into the chamber, the second inlet being arranged relative to the first inlet such that the first fluid stream can entrain and accelerate the second fluid stream foπning a combined fluid stream within the chamber; and a surface coupled to the chamber arranged such that the surface can cause a deviation in the course of the combined fluid stream incident upon it such that contaminants are separated from the combined fluid stream.

2. A separator according to claim 1, wherein the surface comprises an impaction plate.

3. A separator according to claim 2, wherein the impaction plate is positioned in a plane at approximately 90° to the combined fluid stream, such that the impaction plate can cause a deviation in course of the combined fluid stream of approximately 90°.

4. A separator according to claim 2 or claim 3, further comprising a gap extending about at least a portion of the periphery of the impaction plate at the end of the chamber remote from the convergent nozzle, arranged such that the combined fluid stream can pass through the gap into a collection space.

5. A separator according to claim 4, wherein the gap further comprises a bend operable to cause a further deviation in the course of the combined fluid stream.

6. A separator according to claim 4 or claim 5, wherein the impaction plate is mounted such that it can move within the chamber towards and away from the first inlet, decreasing and increasing respectively the size of the gap about at least a portion of the periphery of the impaction plate.

7. A separator according to claim 6, wherein the impaction plate is biased towards the first inlet, the impaction plate further comprising one or more protrusions arranged to space the impaction plate apart from the chamber wall when the impaction plate is at its position closest to the first inlet to preserve at least a minimum size of gap.

8. A separator according to claim 1, wherein the surface comprises an interior surface of a cyclone chamber arranged to receive the combined fluid stream.

9. A separator according to any one of the preceding claims, further comprising a second impaction surface within the second inlet arranged such that the second impaction surface causes a deviation in the course of the second fluid stream incident upon it such that contaminants are separated from the second fluid stream.

10. A separator according to claim 9, wherein the second inlet comprises a narrowed portion, the second impaction surface being positioned proximal to the narrowed portion such that the second fluid stream is incident upon the second impaction surface after passing through the narrowed portion.

11. A separator according to claim 10, wherein the second inlet further comprises a bypass valve arranged such that when fluid pressure within the second inlet exceeds a predetermined value the bypass valve opens to allow at least a portion of the second fluid to pass through a second narrowed portion and be incident upon a third impaction surface.

12. A separator according to any one of the preceding claims, further comprising a fluid outlet allowing the cleaned fluid stream to exit the separator.

13. A separator according to any one of the preceding claims, further comprising a drain positioned to allow contaminants to drain from the separator.

14. A separator according to any one of the preceding claims, wherein the convergent nozzle comprises a convergent-divergent nozzle.

15. A separator according to claim 14, wherein the convergent nozzle comprises a tube including a restricted central portion.

16. A separator according to claim 14, wherein the chamber is generally cylindrical and the chamber diameter proximate to the convergent nozzle is between 2 and 5 times larger than the diameter of the narrowest diameter of the convergent nozzle.

17. A separator according to any one of the preceding claims, wherein the convergent nozzle is arranged to generate a region of reduced pressure within the chamber about the first inlet operable to draw in the second fluid stream from the second inlet.

18. A separator according to any one of the preceding claims, further comprising an annular second nozzle surrounding the first inlet, the second nozzle being in communication with the second inlet such that the second fluid stream can flow through the second nozzle.

19. A separator according to claim 18, wherein the second inlet communicates with an annular space surrounding the chamber, the annular space in turn communicating with the annular second nozzle.

20. A separator according to claim 18 or claim 19, wherein the annular second nozzle is arranged such that the second fluid stream can flow into the chamber generally parallel to the first fluid stream from the first inlet.

21. A separator according to any one of the preceding claims, wherein the chamber is generally formed as a cylinder, the diameter of the chamber reducing towards the surface.

22. A separator according to any one of the preceding claims, wherein the fluid streams comprise gas streams.

23. A separator according to claim 22, wherein the separator is operable to separate particulate, liquid and/or aerosol contaminants from the combined gas stream.

24. A separator according to any one of the preceding claims, wherein the separator is operable to separate greater than 95% of particles greater than 0.3μm in diameter from the combined fluid stream.

25. An internal combustion engine including a separator according to claim 24, wherein the second inlet is arranged to receive blow-by gas derived from a crankcase.

26. An internal combustion engine according to claim 25, wherein the first inlet is arranged to receive a pressurised gas stream derived from a turbocharger and the separator is operable to separate crankcase oil from the combined gas stream, the separator being arranged to return separated crankcase oil to the crankcase.

27. An internal combustion engine according to claim 25 or claim 26, further comprising a vacuum limiting valve coupled to a gas outlet.

28. An internal combustion engine according to any one of claims 25 to 27, further comprising a pressure regulation valve coupled to the second inlet.

30. An internal combustion engine according to any one of claims 25 to 28, further comprising a check valve coupled to a contaminant drain arranged to prevent contaminants being drawn into the separator through the contaminant drain.