This patent disclosure relates generally to oil separators for removing oil and/or particulate matter from gasses discharged from an internal combustion engine, and more particularly to oil separators utilized in a crankcase ventilation system for discharging gasses from an engine crankcase.
Internal combustion engines are widely used to convert a combustible fuel into rotational motion that in turn can be used for mechanical work such as powering or propelling machinery. For example, diesel locomotive engines combust diesel fuel to rotate a crankshaft that propels the locomotive. The crankshaft is generally disposed in a crankcase underneath the engine block and below the cylinders in which combustion takes place. Present in the crankcase may be oil vapor or other lubricants and additionally blow-by gasses, i.e., gasses that inadvertently pass by the piston rings and down the combustion cylinders, gasses that pass through a pressurized intake manifold, gasses that bypass the turbo seals, gasses that bypass valve guide seals, etc, may accumulate there. Typically, it is desirable to remove the gasses and other particulate matter accumulating in the crankcase and maintain the crankcase at a slightly negative pressure, for example, in order to prevent an unintended explosion of combustible gasses in the crankcase or over-pressurization of the crankcase that may blowout gaskets or seals and result in leakage of fluids. To accomplish this, a negative crankcase ventilation system may be utilized.
U.S. Pat. No. 6,647,973 (“the '973 patent”), for example, describes a ventilation system that removes blow-by gasses and other gasses and oil vapor from the crankcase of a diesel engine and directs them to the exhaust system and eventually to the atmosphere. For environmental protection and to reduce soot and other harmful emissions, the '973 patent describes a two-stage filtration assembly that can remove oil vapor and particulate matter from the crankcase gasses. The first-stage includes a first-stage chamber that directly interfaces with the crankcase and a second-stage that includes a separate second-stage chamber adjacently disposed next to the first-stage chamber. As described in the '973 patent, the second-stage chamber is mounted at an angle of about 20° relative to the horizontal so that separated oil collecting at the bottom of the second-stage chamber may drain to a passageway located at the bottom-most point of the first-stage chamber and back to the crankcase. Configurations such as the foregoing for removing separated oil and/or particulate matter from the filtration assembly are desirable because, if separated oil and other particles accumulate in the filtration assembly, they may clog the assembly or they may suddenly discharge through the exhaust system and into the environment. Additionally, configuring the filtration assembly to remove and return oil and/or particulate matter to the crankcase may help prolong the functional life of the crankcase filter elements.
The disclosure describes, in one aspect, a two-stage oil separator for ventilating gasses from a crankcase of an internal combustion engine. The two-stage oil separator can include a housing having a lower end and an upper end. The lower end of the housing communicates with the crankcase and the upper end communicates with the exhaust system of the internal combustion engine. The housing also defines an internal flow channel extending generally upwards from the lower end toward the upper end. A first-stage filter element is disposed in the flow channel toward or in the lower end. The first-stage filter element includes a first filter media of a relatively coarse porosity. A second-stage filter element is disposed toward or in the upper end and generally upward of the first-stage filter element and includes a second filter media of relatively finer porosity.
In a further aspect, there is disclosed a method of ventilating gasses from a crankcase that in part provides a housing including a lower end and an upper end. The lower end communicates with the crankcase and the upper end communicates with an exhaust system. The housing thereby defines at least in part a generally upward flow channel. The method includes directing the crankcase gasses to a first stage filter element disposed toward or in the lower end of the housing and separating from the crankcase gasses relatively larger droplets of oil and or particulate matter. The method further includes directing the crankcase gasses generally upwards through the generally upward flow channel to a second stage filter element disposed toward or in the upper end of the housing and filtering from the crankcase gasses relatively smaller oil droplets and/or particulate matter.
In yet another aspect, the disclosure describes an internal combustion engine having a crankcase with a rotating crankshaft disposed therein. The crankshaft defines a horizontal axis of rotation. The internal combustion engine includes a first two-stage oil separator having a generally upright housing communicating with the crankcase via a lower end and communicating with an exhaust system of the internal combustion engine via an upper end. The first two-stage oil separator further includes a first-stage filter element disposed toward or in the lower end and a second-stage filter element disposed toward or in the upper end vertically above the first-stage filter element. The internal combustion engine also includes a second two-stage oil separator having a generally upright housing communicating with the crankcase via a lower end and communicating with the exhaust system via an upper end. Like the first two-stage oil separator, the second two-stage oil separator also includes a first-stage filter element disposed toward or in the lower end and a second-stage filter element disposed toward or in the upper end vertically above the first-stage filter element. Further, the first and second two-stage oil separators are radially offset from each other with respect to the horizontal axis of rotation.
This disclosure relates to a crankcase ventilation system for removing gasses from the crankcase of an internal combustion engine such as a diesel locomotive engine. However, the ventilation system may be utilized in other applications such as with engines that combust other types of fuel or are used for other purposes such as generation of electricity or powering machinery. Referring to
In the embodiment illustrated in
The first two-stage oil separator 122 communicates with the crankcase 110 to receive crankcase gasses and can direct those gasses onto the exhaust duct 104. To drive or draw the crankcase gasses through the first two-stage oil separator to the exhaust duct 104, an ejector 128 connects the separator and the exhaust duct. The J-shaped ejector 128, which may take the form of an eductor, an aspirator, a Venturi tube or the like, is attached to the first two-stage oil separator 122 via an ejector port 130 and also attaches to the exhaust duct 104 via a flexible exhaust port 132. As will be appreciated by those of skill in the art, the ejector 128 includes internal nozzles so that a high-pressure motive fluid introduced at one end of the ejector can expand internally and generate an internal vacuum such as by generating a Venturi effect that draws crankcase gasses into the ejector through the ejector port 130. Motive fluid and the crankcase gasses can discharge from the ejector 128 to the exhaust duct 104 via the exhaust port 132. The motive fluid can be cooled turbo-charged air diverted from the turbo 102 by an ejector line 134. In the illustrated embodiment depicted in
Referring to
Referring to
To separate out oil and particulate matter entrained in the crankcase gasses, the two-stage oil separator 122 includes a lower first-stage filter element 160 and an upper second-stage filter element 162. The first-stage filter element 160 is disposed inside the lower elbow portion 142 toward or within the lower vertical region 156 of the flow channel 150 and thus proximate to the lower end 138 of the housing 136. The incoming crankcase gasses therefore have already been directed upwards when they encounter the first-stage filter element 160. As will be described in further detail herein, the first-stage filter element 160 includes a first filter media 164 of relatively coarser porosity to separate out larger oil droplets and particulate matter from the crankcase gasses. For example, the first filter media 164 can be particularly suited to remove larger oil droplets and particulate matter on the order of 5 microns or larger while allowing smaller droplets and particles to pass through. The gasses enter the bottom of the first-stage filter element 160, undergo separation, exit through the top and are directed toward the upper vertical region 158 of the flow channel 150.
The second-stage filter element 162 is disposed in the upright portion 144 toward or within the upper vertical region 158 of the flow channel 150 and thus proximate the upper end 139 of the housing 136. The second-stage filter element is therefore downstream of the first-stage filter element 160 to receive the upwardly directed, first-stage filtered crankcase gasses. The second-stage filter element 162 includes a second filter media 166 that is relatively finer than the first filter media 164 and can filter smaller oil droplets and particulate matter. For example, the second filter media 166 can be adapted to remove droplets and particles on the order of 1 micron or larger. After passing through the second-stage filter element 162, the filtered and cleaned crankcase gasses exit the two-stage oil separator 122 via the ejector 128 that can direct the crankcase gasses onto the exhaust duct.
The first-stage filter element 160 and the second-stage filter element 162 are vertically aligned along the vertical reference line 154 such that the second-stage filter element is located vertically above the first-stage filter element. The first-stage filter element 160 can be slightly spaced below the second-stage filter element 162 by, for example, two or three inches though in other embodiments they can physically contact each other. Hence, the first-stage filter element 160 and the second-stage filter element 162 may appear in a vertically stacked relationship. Additionally, the incoming crankcase gasses must rise vertically upwards along the vertical reference line 154 to proceed from the first-stage filter element 160 to the second-stage filter element 162.
The vertical arrangement and relationship of the first-stage filter element 160 and second-stage filter element 162 is believed to help promote separation of oil and/or particulate matter from the crankcase gasses and overall improves emissions from the exhaust system. In particular, the first-stage filter element and the second-stage filter element and the relative porosity of the first and second filter medias cooperate to improve separation of oil and/or particulate matter from the crankcase gasses and return that matter to the crankcase. Filtration through the two-stage oil separator proceeds in stages from separation of larger droplets and particles to filtration of smaller droplets and particles. This tends to ensure that the appropriate filter media filters the appropriate droplets and particular matter and further that the first and second filter medias cooperate together to increase efficiency. For example, as the filtered oil droplets gathers on the finer porosity second filter media 166, they will coalesce together forming larger, heavier droplets until gravity causes them to fall to the first-stage filter element 160. Those droplets will encounter the larger, separated oil droplets that have accumulated in the coarser porosity first filter media 164 and will coalesce together. Gravity will cause these droplets to fall into the lower vertical region 156 of the flow channel 150. The vertically falling oil droplets may encounter and coalesce with oil vapor entrained in the incoming crankcase gasses further advancing the separation process. The droplets impinge upon the bottom, interior surface of the lower elbow portion 142 which will channel the liquid oil to the crankcase. Additionally, because the flow channel 150 is generally sized to have a generally similar diameter or cross-section from the lower vertical region 156 through the elbow portion 142 to the crankcase flange 146, i.e., the flow channel through these regions is generally proportional, separated oil is less likely to become trapped or otherwise impeded from returning to the crankcase.
Referring to
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To maintain its position, the second-stage filter element 162 can be designed slightly larger in diameter than the upper vertical portion 158 so that it can form an interference fit within the flow channel 150. For example, the porous second filter media 166 can surround the steel rod frame 180 and can yield or be physically displaced when inserted into the upright portion 144 of the housing 136. To assist in inserting and removing the second-stage filter element from the upper vertical region 158, the steel rod frame 180 can also include a handle 182 that allows the second-stage filter element to be pulled from the upright portion 144 of the housing 136. Referring back to
As mentioned above, the first filter media can have a relatively coarser porosity than the second filter media. For example, the first filter media can be made from wire mesh or knitted wire mesh such as 304 stainless steel wire mesh with a coiled construction and which is well suited for separating out the larger oil droplets and/or particulate matter. The density of the first filter media can be on the order of about nine pounds per cubic foot. The second filter element can be made from a combined or co-knit metal wire and fiberglass mesh, such as a 304 stainless steel mesh co-knitted with fiberglass. These materials are found to be well-suited for filtering the smaller oil droplets and/or particulate matter that passes through the first filter media. The second filter media can have a density of about 12 pounds per cubic foot.
Referring to
An advantage of using a cover 190 with a releasable latch mechanism 191 is that the second-stage filter element 162 and, if necessary, the first stage filter element 160 can be accessed without having to detach the upright portion 144 of the housing 136 from the elbow portion 142 of the housing. It is believed that the second-stage filter element 162 using the co-knit stainless steel and fiberglass mesh will require replacement and/or cleaning more frequently than the first-stage filter element in part because the finer porosity of the second filter media may become saturated more quickly than the first filter media. Accordingly, locating the second-stage filter element above the first-stage filter element and closer towards the cover facilitates servicing of the two-stage oil separator.
Using a first two-stage oil separator 122 and a second two-stage oil separator 124 as depicted in
For example, referring to
The present disclosure is applicable to a ventilation system for removing crankcase gasses from the crankcase of an internal combustion engine such as a diesel locomotive engine. Referring back to
By utilizing a two-stage oil separator including the vertically arranged first-stage filter element and second-stage filter element, improvements in the separation of oil and/or particulate matter from the crankcase gasses can be realized. For example, referring to FIG. 7, there is a bar chart graphically illustrating data representing the removal of particulate matter for various throttle levels of a diesel engine for the two-stage oil separator as compared with a prior art single-stage oil separator. In particular, a diesel engine was operated and a portion of the gasses from the exhaust system, including crankcase gasses that passed through the oil separators and were directed into the exhaust system, were diverted to an analyzer that measured the particulate matter suspended in the gasses. Hence, a comparison was obtained that showed by quantity or weight how much particulate matter remained in the crankcase gasses after they had been directed through different oil-separators.
The Y-axis 300 in
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It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.