OIL SEPARATOR
The present disclosure relates to a device for separating oil from crankcase blow-by gases such as gases that leak past the piston rings of an internal combustion engine, from the combustion chambers into the crankcase, and also to a method of separating oil from such crankcase blow-by gases.
The present disclosure relates to a device for separating oil from crankcase blow-by gases such as gases that leak past the piston rings of an internal combustion engine, from the combustion chambers into the crankcase, and also to a method of separating oil from such crankcase blow-by gases.
BACKGROUNDAs is well known, an internal combustion engine, such as a conventional petrol or diesel engine for a motor vehicle such as a car, converts chemical potential energy into kinetic energy by burning fuel with an oxidiser such as the oxygen present in air to produce high pressure, high temperature, gases (including CO, CO2 and H2O), from which mechanical energy is extracted by the expansion (and resultant cooling) of those gases in a variable-volume combustion chamber. Most often, that expansion is carried out by the movement of a piston in a cylinder so as to accommodate the necessary change in combustion chamber volume, although other arrangements are known such as that used in a Wankel engine. In a conventional piston/cylinder engine, although a seal exists around the circumference of the piston body (e.g. in the form of one or more piston rings) which aims to prevent the combustion gases from escaping the combustion chamber and passing into the crankcase, inevitably this seal is not 100% effective, and thus some combustion gases pass from the combustion chamber into the crankcase. Similar effects exist in other engine architecture types.
Such gases, termed “bow-by gases”, generally contain not only unburnt fuel, combustion products, and other gases such as water vapour, but also contain minute droplets of the engine's lubricating oil which typically become entrained into the flow of blow-by gases as the gases pass over oil-covered surfaces of the engine's components, and pass through the crankcase which houses the crankshaft that spins at up to several thousand revolutions per minute. If not vented from the crankcase, the blow-by gases would lead to a build-up of pressure inside the crankcase relative to ambient air pressure, which would be sufficient to force lubricating oil out of the engine. For environmental, aesthetic and practical reasons, said lubricating oil is preferably kept inside the crankcase rather than being lost outside the engine.
Initial solutions for venting crankcase pressure simply allowed said blow-by gases to vent to the atmosphere via an opening high up in the crankcase. For environmental reasons (given the content of blow-by gases) such solutions are no longer permitted. More recent solutions therefore pass blow-by gases form the crankcase into the engine's intake, and initially this was done using a simple tube from the crankcase into the engine's intake. Under certain engine operating conditions, however, the volume flow of blow-by gases to be vented from the crankcase can be high enough to cause problems with accurate regulation of fuel/air ratio and thus problems with regulating exhaust emissions. This is at least partly due to the combustible hydrocarbon content of the blow-by gases (e.g. the aforementioned unburnt fuel and droplets of lubricating oil), which when burnt will combine with the oxygen in the intake air/fuel mixture, upsetting the fine balance of air/fuel which is required to keep exhaust emissions low.
Problems in such early existing systems were also encountered with excessive oil consumption, leading to shortened servicing schedules and reliability problems, since any lubricating oil which was entrained into the blow-by gases was either lost to the atmosphere or was passed to the engine's intake to be burnt with the air/fuel mixture.
Such burning of lubricating oil is further undesirable, given that it has different properties compared to the petrol or diesel fuel that a given engine will be optimised for burning, leading to incomplete combustion of said lubricating oil which can result in deposits building up in the internal cavities and passages of the engine and thereby can cause reduced efficiency, and also given the additives in lubricating oil which are often incompatible with exhaust catalysts and NOx control systems and which can thereby reduce the lifetime of such components.
It is thus desirable to remove as much of the lubricating oil content of blow-by gases as possible, over as wide a range of engine operating conditions as possible. Preferably, the oil should be separated from the blow-by gases and returned to the engine's oil reservoir, so that the oil remains available for lubricating the engine, thereby lengthening service intervals and improving reliability. It is further desirable to perform such oil separation in a device which is as compact as possible, as robust as possible, has the lowest possible servicing requirements, and has a form that can be conveniently packaged in an engine bay and is cheap and easy to manufacture.
Existing solutions for separating oil from blow-by gases include simple mesh screens or canisters filled with metal gauze to encourage oil droplets to come out of suspension in the gases, and housings containing baffles arranged to encourage the blow-by gases to change direction and thereby separate the entrained oil droplets from the gases. However, no existing solution has so far been made available which possesses all of the above-mentioned desirable qualities. For example, although wire mesh or gauze type oil separators are cheap and easy to manufacture, their efficiency is relatively low and drops still further at higher flow rates, and furthermore they are prone to clogging and losing effectiveness over time. Other types of oil separators, even if they represent an improvement over a simple gauze or mesh type oil separator, are in many cases less efficient that is desirable, or are only efficient within a narrow range of operating conditions, and/or are not suitable for packaging in a convenient form factor.
The present disclosure aims to alleviate and/or address, at least to a certain extent, the problems, difficulties or limitations associated with existing oil separators and/or oil separation methods.
SUMMARYAccording to a first aspect of the disclosure, there is provided a device for separating oil from crankcase blow-by gases, the device comprising:
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- a housing;
- an inlet arranged to admit the blow-by gases into the housing;
- a first outlet arranged to permit oil separated from the blow-by-gases to exit the housing;
- a second outlet arranged to permit gases having an oil content lower than that of the admitted blow-by-gases to exit the housing; and
- a passageway in the housing, the passageway having a first end proximate to the inlet, and a second end distal from the first end and proximate to the second outlet;
- wherein the passageway comprises a plurality of baffles, successive ones of at least some of the baffles extending from alternate ones of first and second walls of the passageway, towards a respective other one of the first and second walls, the baffles being angled at least partly against a direction of flow within the passageway, said direction being from the inlet to the second outlet.
Optionally, each baffle extends between a base of the housing and a roof of the housing.
Optionally, the device is arranged to be mounted between cylinder banks in a V-configuration engine.
Optionally, at least one of the inlet and first outlet are located in the base of the housing.
Optionally, the second outlet is positioned closer to the roof than to the base.
Optionally, the passageway comprises sequentially arranged first and second portions. Optionally the first and second portions are at least partially separated by a weir comprising a dam and a roof. Optionally, the weir is arranged to impart swirl to the flow of gases within the passageway, and/or optionally the weir comprises a drain hole at the interface between the weir and the base, arranged to allow separated oil to pass therethrough.
Optionally, the second portion has a different cross-sectional area than the first portion. Optionally, the second portion has a larger cross-sectional area than the first portion, and/or optionally the difference in the cross-sectional area between the first and second portions is achieved by providing for the width of the passageway between the first and second walls in the first portion to be correspondingly different to the width of the passageway between the first and second walls in the second portion.
Optionally, the second portion is arranged to provoke greater changes of direction in the gases flowing through that portion than in the first portion. Optionally, the greater changes of direction are provoked by virtue of at least one of: the longitudinal spacing of the baffles being shorter; the angles of the baffles with respect to the walls being more exaggerated; the distance between the tips of the baffles and their respective opposing wall being altered.
Optionally, the passageway is generally arranged in a U shape, and the first portion and the second portion form respective first and second parts of the U shape.
Optionally, a tip of each baffle forms a pinch point with the adjacent opposing one of the first and second walls.
Optionally, the base comprises an oil drain channel for conveying separated oil to the first outlet. Optionally, the oil drain channel slopes downwards so as to assist conveyance of the separated oil to the first outlet by gravitational action.
Optionally, the roof comprises at least one portion that slopes downwards to encourage oil droplets that have accumulated on the roof to be returned to the base by gravitational action.
Optionally, at least one of the pinch points is preceded in the passageway by a gas redirection feature.
In a second aspect, there is provided a motor vehicle, such as a motor car, which includes a device as specified in the first aspect.
In a third aspect there is provided a method of separating oil from crankcase blow-by gases, the method comprising:
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- admitting blow-by gases into a passageway in a housing via an inlet, the passageway having a first end proximate to the inlet, a first outlet, and a second end distal from the first end and proximate to a second outlet;
- passing the blow-by-gases past a plurality of baffles disposed in the passageway, successive ones of at least some of the baffles extending from alternate ones of the first and second walls of the passageway, towards a respective other one of the first and second walls, the baffles being angled at least partly against a direction of flow within the passageway, said direction being from the inlet to the second outlet, such that oil is separated from the blow-by-gases;
- permitting oil separated from the blow-by-gases to exit the housing via the first outlet; and
- permitting gases having an oil content lower than that of the admitted blow-by-gases to exit the housing via the second outlet.
The present technology may be carried out in various ways and embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
As mentioned above, internal combustion engines suffer in use from combustion gases passing past the piston rings (or equivalent features in other engine architectures, such as the rotor seals in a Wankel engine) and into the crankcase, such gases being termed blow-by gases. In use, minute oil droplets (e.g. in the range of around 1 to 100 microns diameter) are typically entrained into the blow-by gases from the lubricated surfaces of components inside the engine block, e.g. as the blow-by gases pass over such surfaces, and as the crank and other moving components stir the gases, and as lubricating oil sprays from the crank bearings and other moving components. For the above-mentioned reasons, it is important to recover as much of this oil from the blow-by gases as possible, and return it to the engine's oil reservoir (e.g. the engine's sump or dry ump lubrication reservoir) rather than allow it to pass into the engine's intake system whereupon it would otherwise be mixed with the fuel air mixture and be burnt in the combustion chambers.
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A further consideration for the design of an oil separator is the physical packaging of the oil separator. As shown in the example engine 200 in
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In operation, according to
All of the above operation, described by way of example so as to place the invention into context, is desirably carried out using an oil separator with as high an efficiency as possible. Such an efficient oil separator which can be conveniently packaged and used as described above will now be described in detail.
As shown in
The passageway 515 further comprises a plurality of baffles 530. Each baffle extends from one of the first and second walls 513, 514 towards the other one of the first and second walls 513, 514, such that a tip of the baffle is proximate to that other one of the first and second walls 513, 514, thereby forming a pinch point 565 between the baffle tip and that other one of the first and second walls 513, 514.
Successive ones of at least some of the baffles 530 extend from alternating ones of the first and second walls 513, 514 of the passageway 515, such that in operation the flow of blow-by gases 370 past those baffles 530 is forced to bend back-and-forth, between a position proximate to the first wall 513 and a position proximate to the second wall 514, as the gases flow along the passageway 515 from inlet 520 to the second outlet 522.
Each baffle 530 extends from its respective one of the first and second walls 513, 514 at an angle to that wall, which angle is smaller on the upstream side of the baffle 530 than a right angle (the upstream side being nearer to the inlet 520, along a path that the passageway 515 takes through the housing 510, than the opposite, downstream, side of the baffle 530), i.e. the tip of each baffle 530 is angled towards the inlet end of the passageway 515, or put another way the tip of each baffle 530 is angled at least partially against the direction of flow of gases in the passageway 515, which direction is in use from the inlet 520 to the second outlet 522.
In general, when in operation, as gases flow through each pinch point 565, the gases are accelerated (by virtue of the reduced cross-sectional area of the passageway 515 at the pinch point 565), and are subsequently decelerated as they flow into the wider part of the passageway 515 after the pinch point 565. By virtue of the different inertial properties of oil and gas, this acceleration/deceleration causes oil droplets suspended in the blow-by gases 370 to separate from the gas content of the blow-by gases 370, whereupon the oil droplets fall out of suspension and attach to one of the roof 511, base 512, and first and second walls 513, 514.
Preferably each baffle also extends between the base 512 and the roof 511 when the base 512 (which in some embodiments is removable) is fitted to the oil separator 210, such that all of the blow-by gases 370 are directed by each baffle 530 past the pinch point 565 that is formed between the baffle tip and the corresponding other one of the first and second walls 513, 514, thereby minimising efficiency losses otherwise caused by gas bypassing the pinch points 565.
Preferably the second outlet 522 is raised with respect to the base 512, so as to discourage separated oil from exiting the passageway 515 in the housing 510 via the second outlet 522, thereby encouraging separated oil to exit the housing 510 via the first outlet 521, and improving efficiency.
Optionally the passageway 515 comprises a first portion and a second portion (as shown in
Optionally the link position comprises a weir 540. Said weir 540 comprises: a weir dam 541 extending upwards from the base 512 to a first vertical position in the housing 510 that is part-way up towards the roof 511; and optionally said weir further comprises a weir roof 542 extending downwards from the roof 511 to a second vertical position in the housing that is part-way down towards the base 512, such that in operation gases passing through the weir 540 are forced to change direction in a up/down direction, which in combination with the side-to-side direction changes caused by the baffles 530, can impart swirl to the gases in use such that additional oil is caused to separate from the blow-by gases, both by virtue of the up-down direction changes at the weir, and by centrifugal action by virtue of the swirl imparted to the gases. Optionally the first vertical position is higher than the second vertical position, thereby forcing a double inversion of the up-down direction of the gases as they pass through the weir in use, thereby enhancing oil separation.
As shown in
In addition to being arranged to have a wider range of gas speeds (i.e. greater acceleration/deceleration between pinch points), the second portion by virtue of being wider between first and second walls can be arranged to direct the gas flow through more extreme angles, resulting in the oil droplets being subjected to even greater acceleration, thereby encouraging the droplets to fall out of suspension and hit the passageway walls and baffles. A similar effect can be achieved by varying the longitudinal spacing between baffles along the passageway, and the angles of the baffles with respect to the passageway walls, so as to vary the distances between baffle tips, and the angles that the gas must bend by in order to travel through the passageway from baffle to baffle.
Furthermore, in a similar way to how the gas speed in the passageway 515 between baffles 530 can be varied by altering the cross-sectional area of the passageway 515, the gas speed at each pinch point 565 can be varied by altering the distance between the tips of the baffles 530 and their respective opposing wall. Thus, each portion of the passageway can be optimised for a particular oil droplet size and/or flow rate, and so the operating range of an oil separator according to such an embodiment can be widened compared with an oil separator having a passageway with only a single cross-sectional area.
In the embodiment of
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Optionally, as shown in
Embodiments of the presently disclosed oil separator 210 can be fabricated using commonly known metal casting, plastics injection moulding, additive manufacturing (such as 3D printing), and/or machining processes as are well-known in the art. For example, the housing (incorporating the first and second walls 513, 514, and the roof 511, as well as inlet 520, first and second outlets 521, 522, and baffles 530, as well as any of the optional components that are illustrated as being part of the housing in such embodiments) can be cast or machined from metal such as aluminium or an alloy thereof, or can be injection moulded from glass-reinforced polyester or other plastics material suitable for withstanding the temperatures found in an engine bay, especially in the engine V 230 of a V-configuration engine block 200. 3D printing techniques are also applicable to the manufacture of such an oil separator 210. The base 512 can be similarly manufactured. Alternatively, the base 512 and housing 510 can, in embodiments, be manufactured in a single piece by techniques such as lost wax casting or by 3D printing. Precision features such as mounting holes can be made using machining or by any process known to the skilled man that is capable of producing such precision.
As illustrated in
In addition, by virtue of the baffles 530 successively extending from alternating walls, the blow-by gases 370 are forced to rapidly pass from side to side in the passageway 515, whereupon the greater inertia of the oil droplets (and thus lower ability to change direction), compared to the gas content of the blow-by gases, causes at least some of the droplets to fail to change direction before hitting the baffles 530 and walls 513, 514, whereupon they come out of suspension and hit the internal surfaces of the oil separator 210, from where they return to the base 512 under gravity.
Furthermore, as the gas approaches the pinch point 565, another portion of the gas is blocked by the baffle 530 and caused to circulate backwards in a vortex 750. This vortex is accentuated by the angle of the baffle 530 being against the direction of gas flow. Circulating motion of the gas and oil droplets at the outer edges of the vortex 750 encourages separation of the oil and the gases by a centrifuging action, wherein the oil droplets hit the baffles and walls and are thereby separated from the gas content. Additionally, stalling of the blow-by gases at the centre of said vortex 750 permits oil droplets to fall out of suspension under gravity, further enhancing separation efficiency.
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The present invention may be carried out in the form of many different embodiments, some of which have been described herein as examples, and many different modifications are envisaged to the embodiments described. For example, features from any particular embodiment or aspect can be combined with any other embodiment or aspect, and alternative examples are envisaged incorporating any mix of features disclosed in the various illustrated and discussed example embodiments, with the only exception to this being where such features are clearly mutually exclusive for technical reasons. The scope of the invention is not therefore to be limited by the specific example embodiments described herein, but instead is defined by the accompanying claims.
Claims
1. A device for separating oil from crankcase blow-by gases, the device comprising:
- a housing;
- an inlet arranged to admit the blow-by gases into the housing;
- a first outlet arranged to permit oil separated from the blow-by-gases to exit the housing;
- a second outlet arranged to permit gases having an oil content lower than that of the admitted blow-by-gases to exit the housing; and
- a passageway in the housing, the passageway having a first end proximate to the inlet, and a second end distal from the first end and proximate to the second outlet;
- wherein the passageway comprises a plurality of baffles, successive ones of at least some of the baffles extending from alternate ones of first and second walls of the passageway, towards a respective other one of the first and second walls, the baffles being angled at least partly against a direction of flow within the passageway, said direction being from the inlet to the second outlet.
2. The device of claim 1 wherein each baffle extends between a base of the housing and a roof of the housing.
3. The device of claim 1 wherein the device is arranged to be mounted between cylinder banks in a V-configuration engine.
4. The device of claim 3, wherein at least one of the inlet and first outlet are located in the base of the housing.
5. The device of any preceding claim wherein the second outlet is positioned closer to the roof than to the base.
6. The device of any preceding claim wherein the passageway comprises sequentially arranged first and second portions.
7. The device of claim 6, wherein the first and second portions are at least partially separated by a weir comprising a dam and a roof.
8. The device of claim 7 wherein the weir is arranged to impart swirl to the flow of gases within the passageway.
9. The device of any of claims 7 to 8, wherein the weir comprises a drain hole at the interface between the weir and the base, arranged to allow separated oil to pass therethrough.
10. The device of any of claims 6 to 9 wherein the second portion has a different cross-sectional area than the first portion.
11. The device of claim 10 wherein the second portion has a larger cross-sectional area than the first portion.
12. The device of any of claims 10 to 11 wherein the difference in the cross-sectional area between the first and second portions is achieved by providing for the width of the passageway between the first and second walls in the first portion to be correspondingly different to the width of the passageway between the first and second walls in the second portion.
13. The device of any of claims 6 to 12 wherein the second portion is arranged to provoke greater changes of direction in the gases flowing through that portion than in the first portion.
14. The device of claim 13, wherein the greater changes of direction are provoked by virtue of at least one of: the longitudinal spacing of the baffles being shorter; the angles of the baffles with respect to the walls being more exaggerated; the distance between the tips of the baffles and their respective opposing wall being altered.
15. The device of any of claims 6 to 14 wherein the passageway is generally arranged in a U shape, and the first portion and the second portion form respective first and second parts of the U shape.
16. The device of any preceding claim wherein a tip of each baffle forms a pinch point with the adjacent opposing one of the first and second walls.
17. The device of any preceding claim wherein the base comprises an oil drain channel for conveying separated oil to the first outlet.
18. The device of claim 17 wherein the oil drain channel slopes downwards so as to assist conveyance of the separated oil to the first outlet by gravitational action.
19. The device of any preceding claim wherein the roof comprises at least one portion that slopes downwards to encourage oil droplets that have accumulated on the roof to be returned to the base by gravitational action.
20. The device of any preceding claim, wherein at least one of the pinch points is preceded in the passageway by a gas redirection feature.
21. A motor vehicle, such as a motor car, which includes a device as specified in any of the preceding claims.
22. A method of separating oil from crankcase blow-by gases, the method comprising:
- admitting blow-by gases into a passageway in a housing via an inlet, the passageway having a first end proximate to the inlet, a first outlet, and a second end distal from the first end and proximate to a second outlet;
- passing the blow-by-gases past a plurality of baffles disposed in the passageway, successive ones of at least some of the baffles extending from alternate ones of the first and second walls of the passageway, towards a respective other one of the first and second walls, the baffles being angled at least partly against a direction of flow within the passageway, said direction being from the inlet to the second outlet, such that oil is separated from the blow-by-gases;
- permitting oil separated from the blow-by-gases to exit the housing via the first outlet; and
- permitting gases having an oil content lower than that of the admitted blow-by-gases to exit the housing via the second outlet.
Type: Application
Filed: Nov 21, 2017
Publication Date: May 23, 2019
Inventors: Ben Husband (Warwick), Luke Scott (Warwick)
Application Number: 15/819,970