US20130104817A1

US20130104817A1 - Engine assembly including crankcase ventilation system

Info

Publication number: US20130104817A1
Application number: US13/281,504
Authority: US
Inventors: Alan S. Miller
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2011-10-26
Filing date: 2011-10-26
Publication date: 2013-05-02
Also published as: CN103075230A; DE102012219308A1

Abstract

An engine assembly includes an engine structure, an air intake assembly and a crankcase ventilation assembly. The engine structure defines a cylinder bore, an intake port and a crankcase. The air intake assembly is in communication with the intake port. The crankcase ventilation assembly includes a housing and a baffle located within the housing. The housing defines an inlet in communication with the crankcase and an outlet in communication with the air intake assembly. Apertures in the baffle define a first characteristic flow rate and spacing between the baffles and housing defines a second characteristic flow rate. In one arrangement, the first and second characteristic flow rates are offset from one another. In another arrangement, the first and second characteristic flow rates are equal to or offset from one another and are each greater than a maximum blowby flow rate of the engine assembly.

Description

FIELD

The present disclosure relates to engine crankcase ventilation systems.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines may combust a mixture of air and fuel in cylinders and thereby produce drive torque. A portion of the combustion gases (blowby) may escape the combustion chamber past the piston and enter the engine crankcase. Crankcase ventilation systems may be incorporated into engines in order to mitigate the effects of blowby gases in the crankcase.

SUMMARY

An engine assembly may include an engine structure, an air intake assembly and a crankcase ventilation assembly. The engine structure may define a cylinder bore, an intake port in communication with the cylinder bore, and a crankcase. The air intake assembly may be in communication with the intake port. The crankcase ventilation assembly may include a housing and a baffle located within the housing. The housing may define an inlet in communication with the crankcase, an outlet in communication with the air intake assembly and an air flow path along a length (L) defined from the inlet to the outlet. A standing wave resonant frequency of the housing is defined by:
$f = \frac{c}{4 L};$
where c is the speed of sound. The baffle may be located within the housing at a position within the flow path between the inlet and the outlet. The baffle may define apertures extending through the baffle and each defining an effective diameter (D₁). An outer perimeter region of the baffle may be spaced from the housing and the spacing between the outer perimeter region of the baffle and the housing may define a flow area (A). The outer perimeter region of the baffle and the housing may define a perimeter (P) surrounding the flow area (A). The flow area (A) and the perimeter (P) define a hydraulic diameter (D₂):
$D_{2} = \frac{4 A}{P};$
and the crankcase ventilation assembly defines first and second characteristic flow rates (Q₁, Q₂):
$Q_{1} = (\frac{{fD}_{1}^{3}}{St}) (\frac{π}{4});$ $Q_{2} = (\frac{{fD}_{2}}{St}) (A);$
with the first and second characteristic flow rates being offset from one another.
In an alternate arrangement, the first and second characteristic flow rates may be equal to or offset from one another and may each be greater than a maximum blowby flow rate of the engine assembly.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

FIG. 1 is schematic illustration of an engine assembly according to the present disclosure;

FIG. 2 is a perspective view of a valve cover from the engine assembly of FIG. 1;

FIG. 3 is a perspective view of a crankcase ventilation assembly from the engine assembly of FIG. 1; and

FIG. 4 is a fragmentary section view of the crankcase ventilation assembly shown in FIG. 1.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
When an element or layer is referred to as being “on,” “engaged to,” “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
With reference to FIG. 1, an engine assembly 10 may include an engine structure 12, a valvetrain assembly 14, pistons 16, a crankshaft 18, connecting rods 20 coupling the pistons 16 to the crankshaft 18, an air intake assembly 22 and a crankcase ventilation assembly 24. The engine structure 12 may include an engine block 26 defining cylinder bores 28, an oil pan 30 coupled to the engine block 26, a cylinder head 32 coupled to the engine block 26 and a cylinder head cover 34 coupled to the cylinder head 32. The cylinder head 32 may define intake and exhaust ports 36, 38. It is understood that the present teachings apply to any number of piston-cylinder arrangements and a variety of reciprocating engine configurations including, but not limited to, V-engines, inline engines, and horizontally opposed engines. It is also understood that the present disclosure is applicable to all types of engine ventilation arrangements including, but not limited to positive crankcase ventilation systems and closed crankcase ventilation systems, as well as both gasoline and diesel engines.
The engine structure 12 may define a crankcase 40 in communication with a fresh air source (A). The crankcase 40 may be in communication with a housing 42 defined by the cylinder head 32, the cylinder head cover 34 and a separator plate 44 via passages (not shown) defined by the cylinder head 32. The valvetrain assembly 14 may include intake and exhaust valves 46, 48, intake and exhaust camshafts 50, 52, intake valve lift mechanisms 54 engaged with the intake valves 46 and the intake camshafts 50 and exhaust valve lift mechanisms 56 engaged with the exhaust valves 48 and the exhaust camshafts 52.
The air intake assembly 22 is in communication with the intake ports 36 and may include an air induction assembly 58, a throttle valve 60 and an intake manifold 62. With additional reference to FIGS. 2 and 3, the crankcase ventilation assembly 24 may be in communication with the crankcase 40 and the air intake assembly 22 and may include the separator plate 44, a foul air line 66 and a flow control device 68. The foul air line 66 may be in communication with the crankcase 40 and the air intake assembly 22 at a location downstream of the throttle valve 60 to remove blowby gases from the crankcase 40. The flow control device 68 may include a valve, an orifice and/or a nozzle to control flow from the housing 42 to the air intake assembly 22.
The separator plate 44 may define air inlets 70 into the housing 42, providing communication between the blowby gases from the crankcase 40 and the housing 42. The cylinder head cover 34 may define an outlet 72 for the housing 42 and may be in communication with the foul air line 66. The flow rate across the flow control device 68 may generally be defined by a pressure in the air intake assembly 22 below atmospheric pressure, resulting in a pressure drop across the flow control device 68. The flow rate across the flow control device 68 may be a steady-state flow rate through the outlet 72 of the housing 42 and may be generally constant over a broad range of pressure values in the air intake assembly 22.
A standing wave frequency (f_s) for the housing 42 may be defined by:
$f_{s} = \frac{c}{4 L}$
where (c) is the speed of sound in air and (L) is the length of the housing 42 from the furthest inlets 70 to the outlet 72. The vortex shedding frequency (f_v) at which vortex shedding takes place in the housing 42 may be defined by:
$f_{v} = \frac{VSt}{D}$
where (V) is flow velocity, St is Strouhal number (smooth tube value of 0.2 used in present example) and (D) is effective diameter. The baffles 64 and the housing 42 may be arranged so that the standing wave frequency (f_s) and the vortex shedding frequency (f_v) are not coincident with one another.
During operation of the engine assembly 10, blowby gas (byproducts of combustion) may escape past the piston and into the crankcase. The baffles 64 may each define apertures 74 and a spacing between an outer periphery 76 of the baffles 64 and the housing 42. An upper region 78 of each baffle 64 may be curved and extend in a flow direction of gas within the housing 42. In the present non-limiting example, the upper region 78 may extend at an angle of at least sixty degrees relative to the main body 80 of the baffle 64.
One baffle 64 is illustrated in FIG. 4 for simplicity. It is understood that in some arrangements the baffle 64 and housing 42 arrangement discussed below may be applied to each of the baffles 64. The apertures 74 may each define an effective diameter (D₁) and the spacing between the outer periphery 76 of the baffle 64 and the housing 42 may define a hydraulic diameter (D₂). The hydraulic diameter (D₂) may be defined by:
$D_{2} = \frac{4 A}{P}$
where (A) is the flow area defined between the outer periphery 76 of the baffle 64 and the housing 42 and (P) is the perimeter surrounding the flow area (A) defined by the outer periphery 76 of the baffle 64 and the housing 42.
The apertures 74 and the spacing between the outer periphery 76 of the baffles 64 and the housing 42 may be defined in terms of first and second characteristic flow rates (Q₁, Q₂). The first and second characteristic flow rates (Q₁, Q₂) are not intended to represent actual flow rates during engine operation, but are instead used for purposes of comparison relative to blowby gas flow rates and the steady-state flow rate through the outlet 72 of the housing 42 and for purposes of defining the apertures 74 and the spacing between the outer periphery 76 of the baffles 64 and the housing 42 relative to one another. The first characteristic flow rate (Q₁) may be associated with the apertures 74 in the baffles 64 and may be defined as:
$Q_{1} = (\frac{{fD}_{1}}{St}) (\frac{π D_{1}^{2}}{4}) = (\frac{{fD}_{1}^{3}}{St}) (\frac{π}{4})$
and the second characteristic flow rate (Q₂) may be associated with the spacing between the outer periphery 76 of the baffles 64 and the housing 42 and may be defined as:
$Q_{2} = (\frac{{fD}_{2}}{St}) (A)$
with frequency (f) being equal to the standing wave frequency (f_s).
In a first non-limiting example, the apertures 74 and the spacing between the outer periphery 76 of the baffles 64 and the housing 42 may be arranged to have the first and second characteristic flow rates (Q₁, Q₂) offset from one another. The first and second characteristic flow rates (Q₁, Q₂) may be offset from one another by at least twenty percent. One of the first and second characteristic flow rates (Q₁, Q₂) may be below a maximum blowby flow rate of the engine assembly 10, and more specifically at least ten percent below the maximum blowby flow rate. The other of the first and second characteristic flow rates (Q₁, Q₂) may be above the maximum blowby flow rate of the engine assembly 10, and more specifically at least ten percent above the maximum blowby flow rate. At least one of the first and second characteristic flow rates (Q₁, Q₂) may be greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation.
In one arrangement of the first non-limiting example, the second characteristic flow rate (Q₂) is greater than the first characteristic flow rate (Q₁) and at least ten percent greater than the maximum blowby flow rate. More specifically, the second arrangement may include the second characteristic flow rate (Q₂) being at least fifty percent greater than the first characteristic flow rate (Q₁). The first characteristic flow rate (Q₁) may be at least ten percent less than the maximum blowby flow rate. The second characteristic flow rate (Q₂) may be at least ten percent greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation and first characteristic flow rate (Q₁) may be at least ten percent less than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation.
In a second arrangement of the first non-limiting example, the first characteristic flow rate (Q₁) is greater than the second characteristic flow rate (Q₂) and at least ten percent greater than the maximum blowby flow rate. The second arrangement may include the first and second characteristic flow rates (Q₁, Q₂) each being greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation, and more specifically each being at least ten percent greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation.
In a second non-limiting example, the apertures 74 and the spacing between the outer periphery 76 of the baffles 64 and the housing 42 may be arranged to have the first and second characteristic flow rates (Q₁, Q₂) equal to or offset from one another. However, the second non-limiting example includes both the first and second characteristic flow rates (Q₁, Q₂) being greater than the maximum blowby flow rate during engine operation. The first and second characteristic flow rates (Q₁, Q₂) may each be at least ten percent greater than the maximum blowby flow rate and at least ten percent greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation. In the present non-limiting example, first and second characteristic flow rates (Q₁, Q₂) may each be at least thirty percent greater than the maximum blowby flow rate and at least thirty percent greater than the steady-state flow rate through the outlet 72 of the housing 42 during engine operation.

Claims

What is claimed is:

1. An engine assembly comprising:

an engine structure defining a cylinder bore, an intake port in communication with the cylinder bore, and a crankcase;

an air intake assembly in communication with the intake port; and

a crankcase ventilation assembly including:

a housing defining an inlet in communication with the crankcase, an outlet in communication with the air intake assembly and an air flow path along a length (L) defined from the inlet to the outlet, a standing wave resonant frequency of the housing defined by:

f = \frac{c}{4 L};

where c is the speed of sound; and

a first baffle located within the housing at a position within the flow path between the inlet and the outlet, the first baffle defining a first aperture extending through the first baffle and defining an effective diameter (D₁) and an outer perimeter region of the first baffle spaced from the housing, the spacing between the outer perimeter region of the first baffle and the housing defining a flow area (A) and the outer perimeter region of the first baffle and the housing defining a perimeter (P) surrounding the flow area (A), the flow area (A) and the perimeter (P) defining a hydraulic diameter (D₂):

D_{2} = \frac{4 A}{P};

and the crankcase ventilation assembly defining first and second characteristic flow rates (Q₁, Q₂):

Q_{1} = (\frac{{fD}_{1}^{3}}{St}) (\frac{π}{4});

Q_{2} = (\frac{{fD}_{2}}{St}) (A);

with the first and second characteristic flow rates being offset from one another.

2. The engine assembly of claim 1, wherein the first and second characteristic flow rates are offset from one another by at least 20 percent.

3. The engine assembly of claim 2, wherein one of the first and second characteristic flow rates is below a maximum blowby flow rate of the engine assembly.

4. The engine assembly of claim 2, wherein the first characteristic flow rate is greater than the second characteristic flow rate.

5. The engine assembly of claim 2, wherein the second characteristic flow rate is at least 50 percent greater than the first characteristic flow rate.

6. The engine assembly of claim 1, wherein one of the first and second characteristic flow rates is at least 10 percent greater than a maximum blowby flow rate of the engine assembly.

7. The engine assembly of claim 6, wherein the other of the first and second characteristic flow rates is less than the maximum blowby flow rate of the engine assembly.

8. The engine assembly of claim 7, wherein the one of the first and second characteristic flow rates is at least 10 percent greater than a steady-state flow rate through an outlet of the housing during engine operation.

9. The engine assembly of claim 8, wherein the other of the first and second characteristic flow rates is at least 10 percent less than the steady-state flow rate through the outlet of the housing during engine operation.

10. The engine assembly of claim 8, wherein the other of the first and second characteristic flow rates is at least 10 percent greater than the steady-state flow rate through the outlet of the housing during engine operation.

11. The engine assembly of claim 1, wherein the baffle defines a plurality of apertures including the first aperture with each of the apertures defining the effective diameter (D₁).

12. The engine assembly of claim 1, wherein the crankcase ventilation assembly includes a plurality of baffles including the first baffle within the housing along the air flow path, with each of the plurality of baffles defining apertures having the effective diameter (D₁) and the outer perimeter region of each of the plurality of baffles and the housing defining the perimeter (P) and the flow area (A).

13. An engine assembly comprising:

an air intake assembly in communication with the intake port; and

a crankcase ventilation assembly including:

f = \frac{c}{4 L}

where c is the speed of sound; and

D_{2} = \frac{4 A}{P}

Q_{1} = (\frac{{fD}_{1}^{3}}{St}) (\frac{π}{4});

Q_{2} = (\frac{{fD}_{2}}{St}) (A);

with the first and second characteristic flow rates each being greater than a maximum blowby flow rate of the engine assembly.

14. The engine assembly of claim 13, wherein each of the first and second characteristic flow rates are at least 10 percent greater than the maximum blowby flow rate.

15. The engine assembly of claim 13, wherein each of the first and second characteristic flow rates are at least 10 percent greater than a steady state flow rate through the outlet of the housing during engine operation.

16. The engine assembly of claim 13, wherein each of the first and second characteristic flow rates are at least 30 percent greater than the maximum blowby flow rate and at least 30 percent greater than a steady state flow rate through the outlet of the housing during engine operation.

17. The engine assembly of claim 13, wherein the baffle defines a plurality of apertures including the first aperture with each of the apertures defining the effective diameter (D₁).

18. The engine assembly of claim 13, wherein the crankcase ventilation assembly includes a plurality of baffles including the first baffle within the housing along the air flow path, with each of the plurality of baffles defining apertures having the effective diameter (D₁) and the outer perimeter region of each of the plurality of baffles and the housing defining the perimeter (P) and the flow area (A).