Patent Application
20160097308
The present disclosure relates generally to a ventilation system and, more particularly, to a system for ventilating a crankcase of an internal combustion engine.
An internal combustion engine typically includes an engine block that at least partially defines one or more cylinders. A piston is reciprocatingly disposed within each cylinder and, together with a cylinder head, forms a combustion chamber. A mixture of fuel and air is introduced into the combustion chamber and is compressed by the piston in preparation for combustion. When combustion takes place, the expanding gases force the piston downward to rotate a connected crankshaft, thereby converting chemical energy into kinetic energy.
During a compression stroke of the piston and during combustion, some of the compressed and expanding gases leak through a necessary clearance between the piston and cylinder and into a space below (i.e., into a crankcase). This leakage of gases is commonly known as “blow-by”. During operation of the engine, the blow-by gases build within the crankcase, resulting in a high-pressure region that acts against movement of the piston and reduces engine efficiency.
Crankcase ventilation systems are typically employed so as to reduce the pressure in the crankcase. In particular, gases from the crankcase are vented to the atmosphere. In some applications, these gases can have oil entrained therein that should not be discharged. For this reason, oil separators are commonly used to separate oil from the gases prior to discharge and to return the oil to the crankcase. Some oil separators draw blow-by gases from the crankcase of an engine using a vacuum produced with compressed air from an engine's turbocharger or from another compressed air source, such as an air compressor powered by the crankshaft of the engine.
An exemplary crankcase ventilation system is disclosed in international patent application PCT/EP2009/003751 of Kölmel et al. that published as WO2009156036 (the '036 publication) on Dec. 30, 2009. The '036 publication discloses an engine having dual cylinder banks and a crankcase ventilation system with multiple oil separators. Each cylinder bank is assigned an oil separator and a dedicated air induction system having a turbocharger, intercooler, and conduits connecting the oil separator to the air induction system. The crankcase ventilation system includes a conduit leading from the engine's crankcase to the oil separator, where gas is separated from oil and drawn through one of two paths into the air induction system. A vacuum produced upstream of the turbocharger compressor draws gas through the first path, and a vacuum produced downstream of the turbocharger compressor draws gas through the second path. Valves at the exit of the oil separators direct separated gas toward the path having the stronger vacuum, depending on load conditions of the engine. Oil collected in the separators is returned to the crankcase through an oil return conduit.
Although perhaps somewhat effective at venting a crankcase, the system of the '036 publication may be bulky and consume too much space on the assembled engine. In addition, because each cylinder bank relies on pressurized air from only a single source (i.e. from a turbocharger), the ventilation system of the '036 publication may lack sufficient vacuum in some situations.
The disclosed ventilation system is directed to overcoming one or more of the problems set forth above.
In one aspect, the present disclosure is directed to a ventilation system for use with an engine having a crankcase. The ventilation system may include a first source of compressed air and a second source of compressed air. The ventilation system may also include a plurality of oil separators, each in separate communication with the crankcase. The ventilation system may further include a distribution manifold in fluid communication with the plurality of oil separators, and a shuttle valve fluidly connected between the distribution manifold and the first and second sources of compressed air.
In another aspect, the present disclosure is directed to a method of venting a crankcase. The method may include directing fluid from the crankcase to a plurality of oil separators in parallel. The method may also include pressurizing air at a first location and at a second location, and selectively diverting pressurized air from the first location or from the second location to the plurality of oil separators.
Engine 10 may also include a crankshaft 14 that is rotatably disposed within engine block 11. A connecting rod (not shown in
A cavity known as a crankcase 15 may at least partially be defined by engine block 11 below the combustion chambers. Lubricant, for example engine oil, may be provided from crankcase 15 to internal engine surfaces to reduce metal-on-metal contact and thereby inhibit damage to the surfaces. Crankcase 15 may serve as a sump for collecting and supplying this lubricant.
During the compression and power strokes of engine 10, some of the compressed and expanding gases may leak from the combustion chambers through a necessary clearance between each piston and cylinder into the crankcase. The leaked gases are referred to as blow-by gases. The blow-by gases may become entrained with lubricant in crankcase 15 and increase the pressure therein. Crankcase vents 16 may be provided to relieve blow-by gases from the crankcase into the atmosphere.
The venting of blow-by gases to the atmosphere may be regulated to reduce the discharge of pollutants. To comply with these regulations, at least one oil separator 17 may be connected to each crankcase vent 16 for separating entrained lubricant from blow-by gases before venting only the gases to the atmosphere. As seen in
Crankcase vents 16 and oil separators 17 may be located near an end of each cylinder bank 12 at a rear end of engine 10. Oil separators may have a single gas inlet 18 for receiving fumes from crankcase 15. Inlets 18 of oil separators 17 may be fluidly connected to crankcase vents 16 by conduits 19. Outlets 20 of oil separators 17 may be fluidly connected to blow-by gas vents 21 via outlet conduits 22. An engine exhaust pipe and after-treatment system 24 may be located above engine 10, and blow-by gas vents 21 may be extended into and communicate with after-treatment system 24. In this configuration, conduits 19 and 22 may be oriented substantially vertically.
Oil separator inlets 18 and outlets 20 may each be independently mounted rearward of cylinder heads 13. In this way, a filter housings 26 of oil separators 17 may also remain rearward of cylinder banks 12. Inlets 18 and outlets 20 may be mounted to an existing support structure 25 on engine 10 to avoid the use of additional mounting materials. Support structure 25 may be any suitable structure on engine 10. Filter housings 26 may fluidly connect oil separator inlets 18 to oil separator outlets 20. Filter housing 26 may also be detachable therefrom without decoupling any other connections within crankcase ventilation system 1.
Oil separators 17 may include a filter media located within filter housing 26 for separating lubricants from blow-by gases. Separated oil may be trapped by the filter media while blow-by gases may pass through the filter media before being vented to the atmosphere. Oil trapped within the filter media may accumulate and subsequently flow back downward into crankcase 15 through inlet 18, inlet conduit 19, and crankcase vent 16. In this way, oil separators 17 may not require additional fittings or conduits to return separated oil to crankcase 15. Gas flow through oil separators 17 may follow a substantially vertical path from crankcase vents 16 to oil separator inlets 18, and oil may return to crankcase 15 along the same substantially vertical path.
Oil separators 17 may use compressed air to generate a vacuum for drawing blow-by gases from crankcase 15. For example, a compressed air inlet 27 may fluidly connect a compressed air supply to a venturi located within filter housing 26 of each oil separator 17 to create a low-pressure space therein. The low-pressure space may be fluidly connected to crankcase vent 16 through filter housing 26 and inlet conduit 19, thereby creating a vacuum that draws fumes from crankcase 15 into oil separators 17. Accordingly, the supply of pressurized air to oil separators 17 may create negative pressure inside crankcase 15. Negative pressure may be maintained in crankcase 15 by continuously supplying oil separators 17 with a sufficient flow rate of compressed air at a sufficient pressure.
An air supply circuit 33 may supply crankcase ventilation system 1 with compressed air. Air supply circuit 33 may include an air induction system 28 of engine 10, which may include one or more turbochargers 29 driven by engine exhaust, and a charge air cooler 30. Air supply circuit 33 may also include an air compressor 31. Air compressor 31 may be any suitable type of air compressor and may be driven with power generated by engine 10. For example, air compressor 31 is depicted in
Turbocharger 29 and air compressor 31 may be fluidly connected to a single shuttle valve 34 via first and second air supply conduits 35 and 36 respectively. Charge air cooler 30 of engine 10 may be fluidly connected between turbocharger 29 and the shuttle valve 34. Shuttle valve 34 may be fluidly connected to compressed air inlets 27 of oil separators 17 via a distribution manifold 37 and distribution lines 38. Shuttle valve 34 may be configured to selectively divert compressed air from either first compressed air source or second compressed air source to distribution manifold 37. Shuttle valve 34 may divert the compressed air based on a pressure of each compressed air source. For example, shuttle valve 34 may be configured to divert compressed air from a higher-pressure one of the first and second compressed air sources to distribution manifold 37.
Air pressure from the first and second air sources may vary over a power output range of engine 10. For example, air pressure from the first location may be higher when a power output of engine 10 is equal to or greater than about 30-40% of its maximum rated power. Alternatively, air pressure from the second location may be higher when the power output of engine 10 is below about 30-40% of its maximum rated power. In this way, the supply of compressed air from a combination of the first and second air sources through shuttle valve 34 to distribution manifold 37 during operation of engine 10 may be substantially constant.
Distribution manifold 37 may be fluidly connected to two or more oil separators 17 of crankcase ventilation system 1. Distribution manifold 37 may deliver a substantially constant supply of compressed to each oil separator 17. While two oil separators 17 are shown in
The disclosed crankcase ventilation system may be applicable to any combustion engine where the atmospheric discharge of blow-by gases is regulated, and where spatial constraints around the engine are important. The disclosed ventilation system may have a reduced footprint on the engine and also high efficiency in venting blow-by gases to the atmosphere. The operation of crankcase ventilation system 1 will now be discussed with reference to
During operation of engine 10, a substantially constant supply of compressed air may be generated by two different sources at two different locations. For example, turbocharger 29 may be driven by exhaust gases of engine 10, and air compressor 31 may be an auxiliary air compressor. Compressed air from turbocharger 29 and air compressor 31 may be delivered to shuttle valve 34 through air supply lines 35 and 36 respectively. Compressed air from turbocharger 29 may pass through charge air cooler 30 before reaching shuttle valve 34 to cool the compressed air, which may have been heated by the turbocharger 29.
Shuttle valve 34 may constantly and selectively divert compressed air from turbocharger 29 and air compressor 31 to distribution manifold 37 based on pressure conditions at the first and second locations. In particular, shuttle valve 34 may selectively divert compressed air to distribution manifold 37 from the higher-pressure source.
Each oil separator 17 may receive the compressed air from distribution manifold 37 through a distribution line 38 at a single compressed air inlet 27. Oil separators 17 may use the compressed air to create and maintain a vacuum that draws blow-by gases from the crankcase 15 of engine 10 through crankcase vent 16. In particular, compressed air inlet 27 may direct compressed air to a venture (not shown in
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed ventilation system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed ventilation system. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
