TECHNICAL FIELD
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.
BACKGROUND
As 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.
SUMMARY
According to a first aspect of the disclosure, there is provided 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.
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:
- 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.
DESCRIPTION OF FIGURES
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:
FIG. 1 shows a plot of blow-by gas volume against engine speed and engine load, for an example Internal combustion petrol engine.
FIG. 2 shows an example V-configuration engine block, with an embodiment of the presently described oil separator mounted to an engine block.
FIG. 3 shows crankcase breathing passages and blow-by gas flow routes for an example V-configuration engine.
FIG. 4 shows, in schematic form, a crankcase breathing system incorporating an oil separator such as the oil separator that is the subject of embodiments of the present disclosure.
FIG. 5 shows underside perspective views, with and without a base/closing plate installed, of a preferred embodiment of an oil separator according to the present disclosure, including some features which are disclosed herein as being optional.
FIG. 6 shows a plan view of an oil separator according to embodiments of the present disclosure, looking into the housing from the direction of the base (which is absent in this view), towards the roof.
FIG. 7 shows a plan view of the oil separator, similar to FIG. 6, with gas and oil flow patterns shown.
FIG. 8A is a top down view of a prototype oil separator according to an embodiment having a central second wall, and showing optional features including an oil drain channel 810 and gas redirection features 820, through an optional detachable transparent lid 830.
FIG. 8B is a side view of the prototype oil separator of FIG. 8A, showing the optional detachable lid side-on.
FIG. 9A is a top-down view through the optional detachable transparent lid 830, showing the optional drain channel 810, and pooling of separated oil as droplets 910 on the roof of the housing.
FIG. 9B is a perspective view of an oil separator according to an embodiment incorporating an oil return slot 920 in the base of a weir dam 541 between first and second portions of a passageway in the housing.
FIG. 10A is a diagram representing gas flow intensity in an embodiment having a central second wall, at a flow rate of 40 Litres per minute with a 5-micron oil droplet size, showing relatively high flow rates at pinch points formed between the tips of baffles and their respective opposing walls, and also showing vortices in the gas flow in front of the baffles, which baffles are angled contrary to the direction of gas flow.
FIG. 103 is a diagram representing gas flow intensity in an embodiment having an offset second wall, at a flow rate of 40 Litres per minute with a 5 micron oil droplet size, showing relatively high flow rates at pinch points formed between the tips of baffles and their respective opposing walls, and also showing vortices in the gas flow in front of the baffles, which baffles are angled contrary to the direction of gas flow, and furthermore showing generally higher gas acceleration and deceleration than in the embodiment of FIG. 10A.
FIG. 11A is a plot of separator efficiency against droplet size, at a flow rate of 40 Litres per minute, for a number of example oil separators of which Concept 3 corresponds to FIG. 10A and Concept 4 corresponds to FIG. 10B, showing superior performance of Concept 4.
FIG. 11B is a plot of separator efficiency against droplet size, at a flow rate of 165 Litres per minute, for a number of example oil separators of which Concept 3 corresponds to FIG. 10A and Concept 4 corresponds to FIG. 10B, showing superior performance of Concept 4.
FIG. 12 is a plot of differential pressure drop from inlet to second outlet, for a range of air flow rates, showing a superior pressure drop for Concept 4, indicative of superior oil separation performance.
FIG. 13 is a plot of separator efficiency against air flow rate, at a constant droplet size, showing that while the separation efficiency of an example existing oil separator (labelled PA) drops off at higher flow rates, separation efficiency of Concept 4 actually increases at higher flow rates up to at least 160 Litres/minute.
DETAILED DESCRIPTION
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.
As shown in FIG. 1, which is a plot 100 of blow-by gas volume 130 against engine speed 120 and engine load (measure by torque 110), for an example internal combustion petrol engine, the amount of blow-by gas can vary greatly with engine operating conditions. For example, a blow-by gas volume flow of about 40 L/min equates to around 70/80 mph at c.2000 rpm, a flow of about 165 L/min might result from Wide Open Throttle (WOT) conditions at high revolution rates, and a flow of about 250 L/min can result under simultaneous conditions of high speed and low load (such as in overrun conditions when the throttle is closed after accelerating to high engine speeds). An ideal oil separator should be able to efficiently separate oil droplets of varying sizes from blow-by gases under all such operating conditions. The design of such an oil separator, however, is not an easy task. Embodiments of the oil separator disclosed herein go at least some way to accomplishing this function.
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 FIG. 2, many engines, especially those in high performance vehicles such as sports cars, use a V-configuration, having two (or more) cylinder banks 220 arranged in a V pattern, each bank of cylinders and associated connecting rods joined to a common crankshaft housed in the crankcase. Such an arrangement is advantageous due to its ability to package a relatively large amount of swept cylinder volume in a relatively small exterior engine block volume. Cylinder heads (not shown) are arranged on top of each cylinder bank 220, and the resulting space in the cylinder V 230 is a convenient space to mount ancillary engine equipment. The design of an oil separator (such as the oil separator 210 embodiment shown) so that it can physically fit in the limited space within a cylinder V 230, while being convenient to fit and remove, and while having the required capacity to efficiently separate oil droplets from the blow-by gases over the full range of engine operating conditions, at the temperatures that are common within a cylinder V 230 (especially in V-configurations which place the exhaust ports of the cylinder head inside the cylinder V), is a non-trivial matter. It will be noted that although the oil separator 210 of FIG. 2 is shown mounted in a cylinder V 230, such an oil cooler 210 as described herein and overcoming the above-mentioned technical constraints, can be applied to other mounting configurations and to other engine configurations.
As shown in FIG. 2, the provided oil cooler 210 is conveniently attached to the cylinder block of the engine 200 at a mounting interface having a breather port for allowing blow-by gases to pass out of the engine block and into the oil separate, and an oil drainage port for allowing recovered oil to pass out of the oil separator and into the engine block, such that the number of hose connections needed to be manually made during engine assembly is reduced. As shown in FIG. 3, a breather port 350 and an oil drain port 360 are provided in a top face of the engine block 200 in the cylinder V 230, and those ports connect directly to corresponding ports provided in the bottom face of the oil separator 210. As shown in FIG. 5, the breather port 350 is arranged to interface with an inlet 520 of the oil separator 210 and the oil return port 360 is arranged to interface with a first outlet 521 of the oil separator 210 (when the oil separator 210 is fitted to the engine block 200), as shown in FIG. 5. A resilient seal (such as a rubber or Viton seal) can be provided in a seal channel 550 so as to prevent leakage of oil or blow-by gases.
As shown in FIG. 2, a breather gallery 355 is provided, in communication with the crankcase 300 and with the breather port 350, so as to permit blow-by gases 370, emerging from the underside of the pistons into the crankcase 300, to pass out of the crankcase 300 to the breather port 350. Further, an oil return gallery 365 is provided in communication with the oil return port 360 and with an oil return pipe 240, the lower end of which pipe 240 is located in use below the level of oil 345 in the engine's oil reservoir, so that blow-by gases are discouraged from being pushed up the oil return pipe 240 against the flow of oil returning to the oil reservoir. Oil returning from the oil separator 210 via the oil return port 360 is thereby directed via the oil return gallery 365 to the oil return pipe 240, and into the oil reservoir. Optionally a similar oil return pipe 240 and oil return gallery (which may double as the breather gallery 355) can be provided on the breather gallery 355 side of the engine block 200, to allow any oil that might flow back into the engine block 200 via the breather port 350 (against the flow of blow-by gases) to return to the engine's oil reservoir.
As shown in FIG. 4, which places the oil separator 210 described herein in context when used in an example closed loop crankcase ventilation system 400, the oil separator 210 is mounted when in use to an example engine having an engine block 200. Said oil separator has an outlet 522 which is communicably connected to components of the engine's Intake system, such as compressors 420 (via respective one-way valves 435) and throttle bodies 450 (via respective pressure control valves 440 and one-way valves 445). One or more connections to allow air from the air intake(s) 410 to be bled (e.g. via one way valves 415 and cam covers 430) Into the engine block 200 can optionally be provided in some systems, to prevent negative pressure conditions from occurring within the crankcase 300 in operation (which conditions would undesirably encourage blow-by gases to pass into the crankcase from the combustion chambers, negatively affecting performance and emissions).
In operation, according to FIG. 4, with reference also to FIG. 5, blow-by gases 370 from the crankcase 300 pass into the oil separator 210, wherein oil droplets are separated from the blow-by gases 370, the resulting recovered oil is returned to the engine's oil reservoir, and the resulting “cleaned gases” (i.e. gases having an oil content that is lower than the oil content of the blow-by gases 370 admitted into the inlet 520 of the oil separator 210) are permitted to exit the housing 510 of the oil separator 210 via second outlet 522. Depending on the particular current operating condition of the engine (e.g. throttle wide open, throttle closed, compressors spinning at high rpm or low rpm, etc.), the cleaned gases are passed from the second outlet 522 of the oil separator 210 to one or both of the compressor inlet(s) 410 and the throttle body/bodies 450. Not shown in FIG. 4 is that the compressor outlets 470 are, in this example, fed via a water charged air cooler to the inlets of the throttle bodies 450, and the outlets of the throttle bodies 460 are fed into an intake manifold of the engine which supplies the cylinder banks 220 with air. Thus, the cleaned gases (which nevertheless contain some content of oil, albeit a lower one than that of the blow-by gases admitted into the inlet 520 of the oil separator 210) are consumed by the engine, and burnt with the fuel/air mixture. The reduced hydrocarbon content of the cleaned gases, by virtue of the reduced oil content, results in improved emissions performance since smaller adjustments to the ideal fuel/air mixture ratio are required to compensate for blow-by gas content, and furthermore the improved ratio of oil returned to the engine's oil reservoir versus oil burnt in the combustion chambers results in lower oil consumption, increased service intervals and greater reliability.
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 FIG. 5, an embodiment of an oil separator 210 according to the present disclosure has a housing 510, which houses a passageway 515 provided for blow-by gases to flow through, the passageway 515 having a first end and a second end, the first end proximate to an inlet 520, and the second end distal from the first end and proximate to the second outlet 522 (and preferably also to the first outlet 511, although in other embodiments the first outlet can be located elsewhere along the passageway 515). The housing 510 comprises a base 512, a roof 511, and first 513 and second 514 walls, and the passageway 515 is defined by said base 512, by said roof 511 which is opposite the base 512, and by said first 513 and second 514 walls which oppose each other and are adjacent to the base 512 and to the roof 511. The inlet is arranged to admit blow-by gases 370 into the passageway 515 in the housing 510. The first outlet is arranged to permit oil separated by the oil separator 210 from the blow-by gases 370 to exit the housing 510. The second outlet is arranged to permit gases having an oil content lower than that of the admitted blow-by gases 370 (i.e. “cleaned” gases from which oil has been separated by the oil separator 210) to exit the housing 510.
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 FIG. 5, although in the general case described above the passageway 515 can be unitary). Optionally the first and second portions are arranged in different directions (such as opposing directions) and communicatively linked at a position 540 inside the housing, such that the first portion of the passageway 515 is arranged between the Inlet 520 and the link position 540 thereby providing for a first direction of flow 571, and the second portion of the passageway is arranged between the link position 540 and the second outlet 522 thereby providing for a second direction of flow 572 that is different to the first direction of flow 571. In the illustrated embodiment, the first wall 513 (which is an exterior wall of the housing 520) extends from a position adjacent to the inlet 520 to the link position 540 as the first wall 513 of the first portion, continues around the end of the housing past the link position 540, and continues from there in the opposite direction to the second outlet 522 as the first wall 513 of the second portion. In said illustrated example, the second wall 514 extends from a position adjacent to the inlet 520 to the link position 540 as the second wall of the first portion, thereby the passageway 515 forms a U shape. In the Illustrated embodiment, the second wall of the first portion also serves as the second wall of the second portion, however in other embodiments a dedicated second wall for the second portion can be provided. Furthermore, the labels of the first and second walls can be the same, or can be swapped when comparing one portion to another portion. In further embodiments, more than two portions of the passageway, each with respective first and second walls can be provided. By providing two or more portions of the passageway 515 which extend in different directions, it is possible to provide a longer passageway 515 in the same length of housing 510, or provide the same length of passageway 515 in a shorter housing 510, thereby assisting the packaging of the oil separator 210 into the tight spaces available in a typical engine bay, such as in a cylinder V 230 between two banks 220 of cylinders.
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 FIG. 5, the base 512 optionally comprises a mounting face 553 for mounting the base to an engine block 200 which may have a corresponding mounting face as shown in FIG. 2. The base 512 optionally comprises a port for the inlet 520 and a port for the first outlet 521. The base 512 also optionally has a seal channel 550 into which a resilient seal (e.g. made of a material such as rubber or Viton) can be fitted so as to provide an effective seal between the base 512 and the engine block 200, and thereby prevent leakage of gases and/or liquids at the interface between said oil separator 210 and engine block 200. In other embodiments, the connections to the oil separator 210 can be provided by conventional means such as by flexible or fixed tubing and associated fittings. Although provision of the inlet port 520 and the first outlet port 521 in a mounting face 553 of the base 512 improves the convenience of the oil separator by reducing assembly effort, this port arrangement is not essential for the operation of the oil separator 210. Provided that the oil separator 210 is provided with an inlet port 520 proximate to the first end of the passageway 515, and is provided with a first outlet 521 somewhere along the passageway (preferably near the second outlet 522 so that separated oil does not have to flow contrary to the direction of gas flow), then providing the inlet and first outlet ports 520, 521 in the mounting face 553 is not essential for the operation of the other advantageous features that are disclosed herein. To assist with the secure mounting and alignment of the seal and the ports 520, 521, the base 512 optionally has one or more dowels 551, and/or one or more mounting holes 552.
FIG. 6 shows many of the same features of the oil separator 210 that are shown in FIG. 5, but in 2-dimensional view rather than in a perspective view. The 2D view of FIG. 6 is a view looking upwards from the underside of the housing 510 (where the base 512 that is not shown in FIG. 6 can be mounted) towards the roof 511 of the housing 510. Also shown in FIG. 6 are intrusions corresponding with exterior recesses 620, which can intrude into the housing 510 so as to provide a recess in the exterior of the housing 510 which may be useful for mounting other equipment items to the engine block 200 via the oil separator 210. A sealing ridge 610 is also shown for increasing the effectiveness of a seal with the base 512.
FIG. 8A is a view of a prototype model (referred to as Concept 3) of an embodiment, wherein the second wall 514 occupies a central position between the first wall of the first portion of the passageway 515 and the first wall of the second portion of the passageway 515, such that the first and second portions of the passageway 515 have approximately equal cross-sectional areas. The view shown in FIG. 8A looks downwards through an optional removable transparent roof 511 towards the base 512. The inlet 520 is labelled, and the second outlet 522 is on the left of the Figure. Visible in the base 512 is an oil drain channel 810 in which separated oil can collect and flow towards the first outlet 521. The oil drain channel is preferably sized with a width and depth that provides sufficient cross-sectional area to allow oil to flow to the first outlet 521 at the required rate, but which limits the surface area of the recovered oil that is exposed to the gas flow within the oil separator 210, so as to prevent recovered oil from being re-entrained into the gas flow within the oil separator 210. Optionally the oil drain channel has a profile in the base that slopes downwards towards the first outlet 521 so as to assist with drainage of separated oil out of the first outlet 521 under gravity. Optionally, gas redirection features 820 can be provided on first and/or second walls 513, 514, preferably ahead of each baffle 530, so as to redirect gases away from the wall (e.g. first wall 513) on which the gas redirection feature 820 is present, and towards a subsequent baffle 530 extending from the opposite wall (e.g. second wall 514). This enhances the formation of vortices 750 and consequent stalling of the gases by the baffle 530, assisting the oil droplets to fall out of suspension under gravity. The optional weir 540 comprising weir dam 541 and weir roof 542 is also shown. As shown in FIG. 8B, the roof 511 of the housing 510 is optionally removable, and in the shown embodiment is fixed to the housing walls with fasteners, although in other embodiments the roof 511 and/or base 512 can be integral with the housing walls.
FIG. 9A is a top-down view of a different embodiment of the presently disclosed oil separator (referred to as Concept 4), wherein the second wall 514 is optionally offset in the housing 510, towards one of: the first wall of the first portion of the passageway 515; and the first wall of the second portion of the passageway 515; such that the first and second portions of the passageway 515 have unequal cross-sectional areas. Preferably, in this optional embodiment, the first portion of the passageway 515 (proximate to the inlet 520) is thus provided with a smaller cross-sectional area than the second portion of the passageway 515 is provided with. Providing two portions of the passageway 515, each having different cross-sectional areas, allows for each portion to be optimised for a different operating range in terms of volume flow rates and/or oil droplet sizes. For example, a portion of the passageway arranged with a relatively smaller cross-sectional area will experience generally faster flow rates in the parts of the passageway between baffles 530, compared with a portion of the passageway arranged with a relatively larger cross-sectional area. Each portion of the passageway will thereby experience a particular differential between gas speed at a pinch point position and gas speed between baffles, depending on the dimensions of that portion of the passageway. The gas speeds in said first portion may thus be optimised for separating relatively large and heavy oil droplets which tend to fall out of suspension in the gas relatively easily. Conversely, the second portion, having a relatively larger cross-sectional area, can be optimised for encouraging any remaining smaller, lighter, oil droplets to fall out of suspension, by being arranged with a larger speed differential between the gas speed at a pinch point position and the gas speed between baffles.
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 FIG. 6, an oil separator having a passageway 515 comprising two portions forming a U shape and divided by a weir 540, with 3 baffles in the first portion and 5 baffles in the second portion, has been found to be particularly effective across a wide range of operating conditions.
FIG. 9A also shows the optional oil drain channel 810 for assisting separated oil to drain to the first outlet 521 without being re-entrained into the gas flow.
Also shown in FIG. 9A is the optional weir 540, comprising weir dam 541 and weir roof 542. As shown in the illustrated embodiments, the weir is advantageously positioned at the turn between first and second portions of the passageway 515, so that in use the up-down redirection of the gases combines with the reversal of the gases at the junction between the first and second portions, thereby allowing for swirl to be imparted to the gases. Also shown in FIG. 9A are droplets 910 of recovered oil which in the test environment were found to collect on the roof 511 of the housing 510. Downwardly sloping features can optionally be provided on the roof 511 so as to assist such oil droplets 910 to overcome surface tension of the oil and return under gravitational force to the base 512 via the walls 513, 514, so that they can drain out of the first outlet 521 rather than being re-entrained into the gas flow.
Optionally, as shown in FIG. 9B the weir dam 541 incorporates an oil return slot 920 that is sized to be smaller in terms of cross-sectional area than a weir opening above the weir dam 541 from the first vertical position to the roof 511 of the housing 510, small enough that gases passing through the weir tend to take the easier route through the weir opening rather than passing through the oil return slot 920, but large enough so that oil which may collect on the upstream side of the weir 540 can pass through the oil return slot 920 to the downstream side of the weir and from there onwards to the first outlet 521 where the oil returns to the engine block 200.
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 FIG. 7, with reference to FIGS. 5 and 6 for structural features, in operation, blow-by gas enters the inlet 520 of the oil separator 210, and passes along the passageway 515 (in the illustrated embodiment, the passageway 515 has the aforementioned optional first and second portions, but the operation described below applies equally to embodiments with a single passageway portion) towards the second outlet 522. As the blow-by gases approach each baffle 530, the gases are stalled (and consequently compressed) and directed towards the pinch point formed between the tip of the baffle 530 and the wall opposite the baffle tip. A portion of the gases passes through the pinch point 565, which portion rapidly accelerates (and expands) as it passes out of the pinch point 565 into the part of the passageway 515 which immediately follows the pinch point 565. This rapid deceleration and then acceleration of the blow-by gases, by virtue of the differing inertia of its gas components and the oil droplets suspended in it, encourages separation of the oil and the gases.
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.
As shown in FIG. 7, after each baffle, the accelerated gases 740 become progressively cleaner (i.e. having a progressively lower oil content), and so the cleaned gases 730 which exit the passageway 515 via the second outlet 522 have a significantly lower oil content than the admitted blow-by gases 710. The oil 720 that is separated from the blow-by gases drains to the base 512 of the passageway 515, and into the oil drain channel 810 shown in FIGS. 8a and 9a, flowing primarily to the first outlet 521 and exiting the oil separator 210. A smaller, secondary, portion of separated oil 720 may also exit the oil separator 210 via the inlet 520, but due to the direction of flow of gases through the passageway 515 opposing the flow of recovered oil out of the inlet 520, the amount of recovered oil 720 flowing out of the inlet 520 versus the amount flowing out of the first outlet 521 is relatively small.
As shown in FIGS. 10a and 10b, which are plots 1000, 1010, showing test results of spatial relative flow velocity 1005, the flow of blow-by gases 370 from inlet 520 through the passageway 515 experiences acceleration at the pinch point 565 (not labelled, for clarity) formed between each baffle 530 and its opposing wall, and subsequent deceleration. Also clearly shown are vortices 750 in front of each baffle 530. Similar acceleration is shown at the weir 540. By comparing FIGS. 10a and 10b, it can be seen that Concept 4 (to which FIG. 10B relates) which is an embodiment having an offset second wall 514 (i.e. non-central within the housing) exhibits consistently higher gas velocities at each pinch point 565, and more consistent vortex 750 formation. Concept 4 is thus a more effective design than Concept 3 to which FIG. 10A relates, however both Concepts are believed to be a significant improvement over existing oil separators.
Additionally, as shown in FIGS. 11a and 11b, which are plots 1100, 1110, of efficiency (y-axis 1106) versus oil droplet size (x-axis 1105) at 40 L/min and at 165 L/min respectively, embodiments of the disclosed oil separator 210 (labelled Concepts 1 to 4) all exhibit improved oil separation efficiency compared to an existing oil separator (labelled PA), both at low flow rates (test parameter=40 L/min) and at high flow rates (test parameter=165 L/min), with Concept 4 being particularly effective. As shown in FIG. 13, which is a plot 1300 of efficiency (x-axis 1305) versus air flow (y-axis 1306) at a constant droplet size, separator efficiency for Concept 4 compared with the tested existing oil separator was found to be an improvement at low flow rates, and an even greater improvement at high flow rates. Finally, as shown in FIG. 12, which is a plot 1200 of differential pressure drop (y-axis 1206) versus air flow rate (x-axis 1205), the differential pressure drop across Concepts 1 to 4 (relating to embodiments of the disclosed oil separator) were all found to be increased over the two existing oil separators which were tested, providing another indication of improved efficiency.
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.
Patent Application
20190153918
