Patent Application
20130104817
The present disclosure relates to engine crankcase ventilation systems.
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.
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:
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):
and the crankcase ventilation assembly defines first and second characteristic flow rates (Q1, Q2):
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.
The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.
Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.
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
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
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 (fs) for the housing 42 may be defined by:
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 (fv) at which vortex shedding takes place in the housing 42 may be defined by:
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 (fs) and the vortex shedding frequency (fv) 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
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:
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:
with frequency (f) being equal to the standing wave frequency (fs).
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.
