GB2491620A

GB2491620A - Impactor oil separator with cut in flat elastomeric valve element

Info

Publication number: GB2491620A
Application number: GB201109619A
Authority: GB
Inventors: Luigi Cuccia
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-06-09
Filing date: 2011-06-09
Publication date: 2012-12-12
Anticipated expiration: 2031-06-09
Also published as: GB2491620B; GB201109619D0

Abstract

An impactor oil separator for crankcase gases has a first plate 3 having a plurality of holes 4,4A,4B through which the gases flow, a second plate (5, fig 1) to change the gas flow path , some holes having valves 10,13 that open or close according to the working condition of the engine and the pressure loss across the impactor. The valve 10,13 can be passive with a cross-shape cut in a flat elastomeric valve membrane, and valves can open at different pressures.

Description

IMPACTOR OIL SEPARATOR FOR CRANKCASE

Technical Field

The present invention relates to an oil separator device, in particular to be used in a crankcase ventilation system JO (CCV).

Background

Crankcase gases contain a mixture of oil, air, water, fuel and blow-by gases, i.e. gases that are blown through the piston ring. Crankcase gases have to be returned to the combustion chamber and, before being exhausted, the oil should be separated from the gases. To separate oil from gases, oil separators are located in the path of the gases for CCV.

A known type of oil separator includes an impactor and a fleece, although separators provided with only an impactor are also known, e.g. from US-A-5,204,203; this document also contains a discussion on the standard way of designing a impactor (see e.g. col. 5, lines 6-27). A known impactor includes a first plate that has a plurality of holes through which the oil-loaded gases flow, a fleece and a second plate that has no holes and that functions as a wall onto which the gases flow is deflected along a different flow path.

The oil-containing gases flow through the first plate holes and are accelerated by the passage through the holes; oil separates from the accelerated flow in the fleece and against the second plate, and it is eventually collected or directly sent to the engine, depending on the position of the separator. A schematic view of the functioning of a known Inpactor-Fleece Separator is shown in fig. 1.

Acceleration of the gas is important to obtain a good separation of oil droplets from the gas flow; efficiency in the separation is usually evaluated by referring to the cut size of the oil droplets, i.e. the minimum dimension of the oil particles that are separated by the impactor. The smaller is the cut size, the greater is the efficiency in the separation process.

Separation efficiency also depends on the flow rate of the gases through the impactor, because an increase in the flow rate corresponds to a decrease of the cut size of the oil particles; this results in a problem because the volume flow rate (1/mm) of an autovehicle engine changes dramatically from idle condition to full load condition; in fact the volume can be 100 times higher at full load than at idle condition.

Moreover, the efficiency also depends on the number of holes in the impactor first plate; an increase of the number of the holes results in a decrease of the efficiency of separation.

A further problem is due to the fact that the impactor is a flow resistance, i.e. a flow restrictor, that produces a pressure loss between upstream and downstream areas, i.e. across the impactor itself; the consequence can be a positive crankcase pressure over wide operating areas. On the other side, if the pressure loss is reduced, e.g. by increasing the number of holes in the first impactor plate, the separation efficiency is reduced. For each engine the impactor separator parameters are adjusted to provide a Pressure Loss that is acceptable and an acceptable cut size of the oil particle. However an increase of the flow rate of the gases results in an increase of the pressure loss.

It is an aim of the present invention to solve the above problems and to provide an irnpactor that can have a reduced pressure loss and a high separation efficiency, with reduced influence of the gases volume flow, i.e. flow rate, (1/mm).

Sumrrta ry The problem is solved by the present invention, that relates to an impactor oil separator for separating oil from flowing gases in a crankcase system, comprising a first plate having a plurality of holes through which said gases flow, a second plate connected to said first plate, said second plate being positioned to change the flow path of said gases, the combination of said first and second plate causing a separation of oil particles from the flow of gases, characterized in that at least part of the said holes in the said first plate are provided with valves that open or close according to at least the value of the pressure loss across the impactor.

Preferably, the first plate, or acceleration plate, has a number of holes that are free of valves and some holes provided with valves; most preferably, the holes have all the same diameter.

S

In the preferred embodiment, the valves are passive valves that change the cross-sectional area of the corresponding hole along the flow axis of the gases when a specific value of pressure loss is reached.

According to another aspect, the valves comprise an elastomeric membrane that preferably has a partial cut in a cross shape; said cut provides four triangle portions of the valve that allow deformation of the membrane portions by the flow of gases. The membrane preferably has a diameter greater than the diameter of the corresponding hole of the first plate.

In another exemplary embodiment, the impactor oil separator comprises two or more types of valves, each type being suitable to open at a different pressure loss than the other type(s) of valves.

The invention thus also relates to an impactor separator as a component of an internal combustion engine.

The invention also relates to a method of separating oil particles from a gas flow in a crankcase, comprising the step of flowing said gases through an impactor separator as above disclosed, said separator including acceleration holes in a first plate of said impactor, characterized in that the pressure loss across said impactor in the gas flow is controlled by means of at least one valve provided on at least one hole of said impactor first plate.

The at least one valve opens when a specific value of pressure loss is reached, so as to open at least one further hole in said first plate of the impactor. In a further embodiment, different valves open at different pressure losses, i.e. a first group of valves open when the pressure loss is e.g. 8 mbar and a second group open at a pressure loss of e.g. 12 mbar.

The invention provides several advantages over the prior art.

The improved impactor separator makes it possible to avoid or limit the increase of pressure loss that normally occurs when the volume flow across the impactor increases. The value of the pressure loss can thus remain similar to the value that was selected for optimal performance of the separation process.

Another advantage is that the invention impactor can be used with existing engine and crankcase designs; a further advantage is that the addition of extra holes in the first plate of the impactor is easy and not expensive to carry out.

Brief Description of the Drawiçgs

Further advantages and features of an embodiment of the present invention will be more apparent from the

description below, provided with reference to the

accompanying drawings, purely by way of a non-limiting

example, wherein:

-Fig. I is a schematic view of the functioning principle of operation of an impactor oil separator; -Fig. IA is a schematic view 6f the position of an impactor separator in an Internal Combustion Engine

according to the prior art;

-Fig. 2 is a perspective view of the basic structure of an impact separator; -Fig. 3 is a perspective front view, partial, of a separator according to an exemplary embodiment of the invention; -Fig. 4 is a back view of the separator of fig. 3; -Fig. 5 is a partial, enlarged, sectional view of the front plate of the separator of fig. 3; -Fig. 6 is a perspective view of a valve according to an embodiment of the invention; -Fig. 7 is an enlarged sectional view of the valve of fig. 6 -Fig. 8 is a graph of the pressure drop in the operation of a separator according to the invention.

Detailed Description

The operation of an impactor oil separator is schematically shown in fig. 1, that does not refer to an embodiment of the invention. A flow of crankcase gases 2, including blow-by gas from the cylinder and carrying small oil particles 8A, enters a first plate 3 (acceleration plate) of an inpactor 1, through a plurality of holes 4. As previously mentioned, the gas flow 2 is accelerated against a second plate 5 and a fleece 6; second plate 5 is free from holes and diverts the flow of gas into a different path, that is vertical instead of horizontal as is the flow path in holes 4. Oil droplets 8 separate from the diverted flow and are collected and sent to the oil pan 16. The clean flow 7 is re-circulated into the combustion chamber 19.

Fig. 1A shows the position of an impactor separator 1 in an internal combustion engine 14 according to known prior art.

The separator 1 receives crankcase gases through duct 15 that is connected to the rocker cover 17. Outlet 18 of duct is located into the air intake manifold 20. The engine is provided in a known way with an oil pan 16 and a combustion chamber 19.

An example of a structure of a prior art impactor separator is shown in fig. 2; as visible, fleece 6 is inserted between first and second plates, 3 and 5; and first plate 3 is provided with holding means 9 in the form of ribs and pointed elements, to hold in place the fleece.

Figures 3 and 4 show the front and the back of first plate 3 in an impactor according to an exemplary embodiment of the invention, where first plate 3 has six standard holes 4, i.e. holes according to the known technique.

Additionally, plate 3 has two further holes 4A, that are both provided with a valve 10; valves 10 open or close according to the working condition of the engine, namely according to the value of the pressure loss across the irupactor.

In the embodiment shown in the figures, holes 4 and holes 4A have identical diameter, however different diameters can be used. Valves 10 are passive valves, i.e. valves that open or close according to the value of the pressure loss across the impactor without having to resort to valve actuating devices. In the preferred exemplary embodiment here disclosed, valves 10 are membrane valves made of an elastomer suitable to withstand the temperature and the operating conditions; an example of suitable materials are Ethylene Acrylic Elastomers (AEM) such as Vamac ® from DuPont and Hydrogenated Nitrile Rubbers (HNBR) such as Zetpol ® from Zeon.

Valve 10 of the exemplary embodiment is a flat element, a kind of "membrane", provided with a cut 11 that has the shape of a cross (see fig. 6 and 7) and that extends partially from the center of the valve; in the shown embodiment the cut is in the form of two grooves perpendicular to each other that define four quasi-triangular portions 12 of valve 1; different shapes and profiles of cut 11 can be used as well as different types of valves. The shape of the cut, the thickness T (fig. 7) of the valve and the physical properties of the material of which the valve is made, will determine the pressure required to open the valve by pushing the triangular portions 12 as schematically shown by arrows in fig. 7.

As visible from exemplary embodiment.of figure 5, the diameter of valve 10 is greater than the diameter of corresponding hole 4, to allow fixing the valve over the hole; preferably length L of the cut 11 is corresponding to the diameter of hole 4A.

In a further embodiment, the impactor is comprising two or more types of valves, each type being suitable to open at a different pressure loss than the other type(s) of valves.

More in detail, first plate 3 is provided with another set of holes 4B and corresponding valves 13, shown with dotted lines in fig. 3 and 4. Valves 13 of this embodiment are made such as to open at a different and higher pressure than valves 10, so as to open at a different moment than valves 10.

The method of separating oil particles from gases in a crankcase, that makes use of the above disclosed impactor, comprises the known step of flowing crankcase gases, including blow by gases, through the impactor separator of the invention. The gases flow through the holes of the first plate 3 of the separator 1 and are accelerated, the impactor generates a pressure drop (or pressure loss) that depends from the number of holes. The impactor comprises at least one hole having a valve that is normally closed and that opens when a specific value of pressure loss is reached, so as to open at least one further hole in the first plate of the impactor.

hs previously mentioned, the invention method provides for separating oil particles from gases in a crankcase by f lowing the gases through an impactor separator according to what above disclosed and accelerating the gases in a number of open acceleration holes 4 in the first plate 3 of impactor 1. The pressure loss in the gas flow across the impactor 1 is controlled by means of at least one further valve, 13, provided on at least one additional hole 41k, 4B, of the first plate 3 of impactor 1. Valves 11 and 13 are normally closed and open under a preset pressure, i.e. when the pressure drop in the impactor has reached a preset value. Opening of the additional valves will reduce the pressure loss.

An example of operation is shown in fig. 8. 5.

In fig. 8 a graph shows the pressure loss values in an impactor according to the invention that has six standard holes 4, open and free from valves, i.e. no valves are provided at holes 4. Two additional holes 4A are provided, each hole IA having a valve 11 set to open at a pressure loss of 8 rnbar; moreover, another two further holes 48 having a valve 13 set to open at a pressure loss of 10 mbar are also present in plate 3.

The initial flow rate is 40 1/mm, corresponding to a pressure loss of 4 mbar through the impactor having six open holes (holes 4); the remaining holes 4A and 4B are closed by the corresponding valves 11 and 13.

When the volume flow, or flow rate, increases and reaches about 60 1/mm, the pressure loss increases to 8 mbar: at this pressure valves 11 open to free holes 4A and the pressure loss is reduced to a value of about 5 rnbar. If the increased flow rate is not sufficient to maintain them open, valves 11 will shortly or partially close to open again when the pressure loss increases, acting as a diaphragm.

When the flow rate increases again, e.g. to about 80 1/mm, also the pressure loss will increase, to about 10 mbar: at this value of pressure loss valves 13 open to free two further holes in plate 3, i.e. holes 48. The result is a reduction of the pressure loss to a value of about 6 mbar.

The graph of fig. 8 shows in a dotted line the pressure drop values that would have been reached with the six-holes initial configuration if this configuration was fixed as in the state of the art embodiments. At about 100 1/mm of flow rate, the pressure drop of the prior art embodiments would have been circa 26 mbar, compared to a pressure of about 9 mbar in the embodiment of the invention.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

Claims

CLAIMS1. An impactor oil separator (1) for separating oil from flowing gases (2) in a crankcase system, comprising a first plate (3) having a plurality of holes (4, 414, 4B) through which said gases flow, a second plate (5) connected to said first plate (3), said second plate being positioned to change the flow path of said gases, the combination of said first (3) and second plate (5) causing a separation of oil particles (8) from the flow of gases (7), characterized in that at least part of said holes (4A,43) in the said first plate (3) are provided with valves (10, 13) that open or close according to the working condition of the engine and the value of the pressure loss across the impactor (1).
2. An impactor oil separator according to claim 1, wherein a number of holes (4) is free of valves.
3. An impactor oil separator according to claim 1 or 2, wherein said holes (4, 414, 45) have all the same diameter.
4. An impactor oil separator according to any previous claim, wherein said valves (10, 13) are passive valves that change the cross-sectional area of the corresponding hole along the flow axis of the gases when a specific value of pressure loss is reached.
5. An impactor oil separator according to claim 4, wherein said valves (10, 13) comprise an elastomeric flat element.
6. An impactor oil separator according to claim 5, wherein said flat element has a cut (11) that allows the flow of gases (2) to deform the flat element portions (12) defined by said cut (11).
7. An impactor oil separator according to claim 6, wherein said flat element has a diameter greater than the diameter of the corresponding hole (4A, 4B) of said first plate (3)
8. An impactor oil separator according to any previous claim, comprising two or more types of valves (IA, 4B), each type being suitable to open at a different pressure loss than the other type(s) of valves.
9. An impactor oil separator (1) according to any previous claim as a component of an internal combustion engine (14).
10. A method of separating oil particles from gases in a crankcase, comprising the step of flowing said gases (2) through an impactor separator (1) according to any previous claim, said separator including acceleration holes (4,4A,4B) in a first plate (3) of said impactor, characterized in that the pressure loss across said impactor (1) in the gas flow is controlled by means of at least one valve (10, 13) provided on at least one hole (4A, 4B) of said impactor first plate (3).
11. A method according to claim 10, wherein said at least one valve (10, 13) opens when a specific value of pressure loss is reached, so as to open at least one further hole (4A, 4B) in said first plate (3) of the irnpactor (1).
12. A method according to claim 11, wherein different valves open at different pressure losses.