US20070068146A1

US20070068146A1 - Exhaust treatment system having hydraulically-actuated air valve

Info

Publication number: US20070068146A1
Application number: US11/236,486
Authority: US
Inventors: Rodney Rolffs; Manoj Baweja; John Gierszewski
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2005-09-28
Filing date: 2005-09-28
Publication date: 2007-03-29
Also published as: DE112006002606T5; CN101278108A; WO2007040786A1

Abstract

An exhaust treatment system for a power source is disclosed. The exhaust treatment system has an inlet configured to receive an exhaust flow from the power source, a filtering medium configured to remove particulate matter from the exhaust flow, and an outlet configured to direct the exhaust flow from the filtering medium to the atmosphere. The exhaust treatment system also has a heating device configured to raise the temperature of the particulate matter entrained within the filtering medium, a supply of pressurized air, and a pilot-operated valve configured to selectively direct the pressurized air to the heated particulate matter.

Description

TECHNICAL FIELD

The present disclosure relates generally to an exhaust treatment system and, more particularly, to an exhaust treatment system having a hydraulically-actuated air valve.

BACKGROUND

Internal combustion engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous compounds and solid particulate matter, which may include unburned carbon particulates called soot. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of particulate matter emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. One method that has been implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine using a particulate trap. A particulate trap is a filter designed to trap particulate matter in, for example, a wire mesh or ceramic honeycomb filtering media. Over time, the particulate matter may accumulate in the filtering media, thereby reducing filter functionality and engine performance.
Various regeneration techniques may be employed to manage the accumulated particulate matter. For example, U.S. Pat. No. 5,090,200 (the U.S. Pat. No. '200 patent) issued to Arai on Feb. 25, 1992, describes a regeneration system for a particulate trap provided in an exhaust pipe of an engine. The regeneration system includes a heater provided on a front face of the particulate trap, a blower to pressurize regeneration air, a solenoid-operated air valve, and a bypass valve. When the particulate trap is saturated with particulate matter, the bypass valve is opened and the heater is turned on to initiate combustion. To facilitate the combustion of the particulate matter, the blower is turned on and the air valve is electronically controlled according to various input to allow the pressurized regeneration air to blow toward the operational heater.
Although the regeneration system of the U.S. Pat. No. '200 patent may sufficiently regenerate the particulate trap, the system may be expensive and costly to operate. In particular, because the solenoid directly opens the air valve against pressurized air, the solenoid must be large to overcome the force of the high pressure regeneration air. The large solenoid may increase the component cost of the regeneration system, require complex and expensive control systems, and require high currents that add to the operating cost of the system and reduce efficiency of the machine employing the system.
The disclosed exhaust treatment system is directed to overcoming one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed to an exhaust treatment system. The exhaust treatment system includes an inlet configured to receive an exhaust flow from the power source, a filtering medium configured to remove particulate matter from the exhaust flow, and an outlet configured to direct the exhaust flow from the filtering medium to the atmosphere. The exhaust treatment system also includes a heating device configured to raise the temperature of the particulate matter entrained within the filtering medium, a supply of pressurized air, and a pilot-operated valve configured to selectively direct the pressurized air to the heated particulate matter.
In another aspect, the present disclosure is directed to a method of treating an exhaust flow of a power source. The method includes directing the exhaust flow from the power source to a filtering medium to remove particulate matter from the exhaust flow, directing the exhaust flow from the filtering medium to the atmosphere, and raising the temperature of the particulate matter entrained within the filtering medium. The method also includes regulating a flow of pilot fluid to an air valve to selectively pass pressurized air to the heated particulate matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of a work machine having an exemplary disclosed exhaust treatment system; and
FIG. 2 is a cross-sectional illustration of an exemplary disclosed pilot-operated air valve for the exhaust treatment system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary work machine 10 having multiple systems and components that cooperate to accomplish a task. Work machine 10 may perform some type of operation associated with an industry such as mining, construction, farming, transportation, power generation, or any other industry known in the art. For example, work machine 10 may embody a mobile work machine such as an excavator, a dozer, a loader, a backhoe, a motor grader, a dump truck, or any other earth moving machine. Work machine 10 may alternatively embody a stationary work machine such as a generator set, a furnace, or another suitable stationary machine. Work machine 10 may include a power source 12, an air induction system 14, and an exhaust treatment system 16.
Power source 12 may include a combustion engine having multiple subsystems to produce a mechanical or electrical power output and a flow of exhaust gas. For example, power source 12 may include a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of combustion engine known in the art. Power source 12 may also include a lubrication system 18 and a fuel system 20. It is contemplated that power source 12 may include additional and different subsystems such as, for example, a cooling system, a drive system, a guidance system, or any other appropriate system.
Lubrication system 18 may include components that circulate a lubricant throughout portions of power source 12. Specifically, lubrication system 18 may include a pumping mechanism 22 configured to draw the lubricant from a sump 24 via a supply line 26 and pressurize the lubricant to a predetermined pressure level. Pumping mechanism 22 may embody a variable or fixed displacement pump that is electrically driven or coupled to power source 12 in a direct or indirect drive configuration. The lubricant may include, for example, engine oil. Lubrication system 18 may direct the pressurized lubricant from pumping mechanism 22 to the components of power source 12 via a fluid passageway 28, and return the lubricant to sump 24. A check valve 31 may be disposed within fluid passageway 28 to provide one-directional flow from pumping mechanism 22.
Fuel system 20 may include components that cooperate to deliver injections of pressurized fuel into combustion chambers (not shown) of power source 12. Specifically, fuel system 20 may include a tank 30 configured to hold a supply of fuel, and a fuel pumping arrangement configured to pressurize the fuel and direct the pressurized fuel to fuel injector means (not shown) associated with power source 12.
Tank 30 may constitute a reservoir configured to hold a supply of fuel. The fuel may include, for example, diesel fuel, gasoline, kerosene, a heavy fuel, or any other type of fuel known in the art. One or more systems within work machine 10 may draw fuel from and return fuel to tank 30. It is also contemplated that fuel system 20 may be connected to multiple separate fuel tanks, if desired.
The fuel pumping arrangement may include one or more pumping devices that function to increase the pressure of the fuel. In one example, the fuel pumping arrangement may include a low pressure source 32 and a high pressure source 34 disposed in series and fluidly connected by way of a fuel line 36. Low pressure source 32 may embody a transfer pump configured to provide low pressure feed to high pressure source 34, while high pressure source 34 may receive the low pressure feed and increase the pressure of the fuel to the range of about 40-190 MPa. High pressure source 34 may be connected to power source 12 by way of a fuel line 37. A check valve 38 may be disposed within fuel line 37 to provide one-directional flow of fuel from the fuel pumping arrangement to power source 12.
One or both of low and high pressure sources 32, 34 may be operably connected to and driven by power source 12. In particular, low and/or high pressure sources 32, 34 may be connected with power source 12 in any manner readily apparent to one skilled in the art where an output rotation of power source 12 will result in a corresponding rotation of a drive shaft of low pressure source 32 and high pressure source 34. It is contemplated, however, that one or both of low and high pressure sources 32, 34 may alternatively be driven electrically, hydraulically, pneumatically, or in any other appropriate manner.
Air induction system 14 may include components configured to introduce compressed air into a combustion chamber (not shown) of power source 12. For example, air induction system 14 may include an air filter 40 and a compressor 42. It is contemplated that air induction system 14 may include different or additional components than described above such as, for example, inlet bypass components, venturis, after and/or inter-stage air coolers, exhaust gas recirculation components, and other known components.
Air filter 40 may be configured to remove or trap debris from air flowing into power source 12. For example, air filter 40 may include a full-flow filter, a self-cleaning filter, a centrifuge filter, an electrostatic precipitator, or any other type of air filtering device known in the art. It is contemplated that more than one air filter 40 may be included within air induction system 14 and disposed in a series or parallel arrangement.
Compressor 42 may be configured to compress the air flowing into power source 12 to a predetermined pressure. In particular, compressor 42 may include a fixed geometry type compressor, a variable geometry type compressor, or any other type of compressor known in the art disposed downstream of air filter 40. Compressor 42 may be connected to air filter 40 by way of an inlet passageway 44 and to power source 12 by way of an inlet manifold 46. It is contemplated that more than one compressor 42 may be included and disposed in parallel or in series relationship. It is further contemplated that compressor 42 may be omitted, for example, when a non-compressed air induction system is desired.
Exhaust treatment system 16 may include a means for directing the flow of exhaust gases from power source 12 to the atmosphere, and for treating the exhaust flow. For example, exhaust treatment system 16 may include a turbine 48 connected to receive exhaust from power source 12, a particulate trap 50 disposed downstream of turbine 48, and a regeneration subsystem 52 located therebetween. It is contemplated that exhaust treatment system 16 may include additional and/or different components such as, for example, NOx absorbers or other catalytic devices, attenuation devices, recirculation systems, and other means known in the art for directing exhaust flow from power source 12 and/or for treating the flow of exhaust.
Turbine 48 may be connected to drive compressor 42. In particular, as the hot exhaust gases from power source 12 expand against blades (not shown) of turbine 48, turbine 48 may rotate and drive compressor 42. It is contemplated that more than one turbine 48 may alternatively be included within exhaust treatment system 16 and disposed in a parallel or series relationship, if desired. It is also contemplated that turbine 48 may be omitted and compressor 42 driven directly by power source 12 mechanically, hydraulically, electrically, or in any other manner known in the art, if desired.
Particulate trap 50 may include one or more filtering elements 54 configured to remove particulate matter from the exhaust flow. Specifically, filtering elements 54 may embody deep bed ceramic-type elements configured to accumulate particulate matter throughout a thickness of the element, shallow bed type elements such as impingement type metallic or ceramic meshes configured to accumulate particulate matter at a surface of the element, or any other suitable type of filtering element know in the art. The size of the pore and/or mesh openings of filtering elements 54 may vary and be selected depending on a particular application. It is contemplated that filtering elements 54 may include pleats to increase a filtration area, may be catalyzed to reduce an oxidation temperature, may include an electrostatic device, and/or may be electrically conductive to facilitate a regeneration process, if desired.
Regeneration subsystem 52 may include components configured to regenerate, particulate trap 50. Specifically, regeneration subsystem 52 may include a regeneration initiation device 56, a venturi 58, and an air valve 60. It is contemplated that regeneration subsystem 52 may include additional and different components such as, for example, blocking or bypass elements, catalytic devices, or any other appropriate regeneration components. It is further contemplated that venturi 58 may be omitted, if desired.
Regeneration initiation device 56 may be configured to initiate regeneration of filtering elements 54 in response to one or more input. In one example, regeneration initiation device 56 may embody a fuel injector mechanism having a fuel valve connected to high pressure source 34 by way of an auxiliary supply line 62. In response to the one or more input, the fuel valve may direct a pressurized stream of fuel into venturi 58 and toward filtering elements 54. As the pressurized stream of fuel ignites, the temperature of the particulate matter entrained within filtering elements 54 may be elevated to combustion. The one or more input may include, for example, an elapsed time period, an exhaust temperature, a pressure differential across filtering elements 54, an exhaust back pressure, or any other suitable condition. It is contemplated that regeneration initiation device 56 may alternatively embody an electrical heating element, an engine valve timing controller, a catalyst injection device, or any other initiation device known in the art.
Venturi 58 may be configured to constrict the flow of exhaust within exhaust treatment system 16, thereby increasing a speed of the exhaust gasses passing through venturi 58 and, in turn, reducing a pressure of the flow of exhaust through the constriction. Venturi 58 may be fluidly disposed between turbine 48 and particulate trap 50 where the reduced pressure may function to draw the pressurized stream of fuel from regeneration initiation device 56 and pressurized air from air valve 60.
Air valve 60 may be configured to selectively allow pressurized air to flow from compressor 42 toward filtering elements 54 in response to an electrical input and a fluid pressure. In particular, air valve 60 may be fluidly connected to compressor 42 by way of a fluid passageway 64 and fluidly connected to pumping mechanism 22 by way a pilot passageway 65. As illustrated in FIG. 2, air valve 60 may embody a solenoid-actuated, pilot-operated valve having a solenoid mechanism 66, a pilot valve element 68, and a main poppet element 70. Solenoid mechanism 66 may electrically actuate air valve 60 to regulate a flow of pilot fluid through pilot passageway 65 such that pressurized air is allowed to flow from compressor 42 through fluid passageway 64 and air valve 60 to filtering elements 54. It is contemplated that air valve 60 may include additional components known in the art such as, for example, a common housing, sealing elements, guide elements, fasteners, check valves, relief valve elements, makeup valve elements, pressure balancing passageways, and other such components.
Solenoid mechanism 66 may be electrically connected to a controller (not shown) and include an armature 72 with a connected pin 74, both movable against the bias of a pilot return spring 76 from a neutral state to an energized state. Armature 72 and connected pin 74 may move from the neutral state to the energized state in response to an applied current.
Pilot valve element 68 may engage pin 74 to follow the movement of armature 72 and pin 74, thereby selectively causing an increase or decrease in pilot fluid pressure within air valve 60. In particular, pilot valve element 68 may include a central bore 78, a set of radial passageways 80, and a centrally-located external annular groove 82. The pilot fluid may enter air valve 60 from pilot passageway 65 via an inlet port 84, flow from annular groove 82 to central bore 78 via the set of radial passageways 80, and exit both ends of pilot valve element 68. When armature 72 and connected pin 74 are in the neutral position, pilot valve element 68 may be biased by a main return spring 86 toward a closed position at which the lubricant may be blocked from exiting air valve 60 resulting in a buildup of pressure within air valve 60. However, when armature 72 and connected pin 74 are urged toward the energized position, pilot valve element 68 may be likewise moved against the bias of main return spring 86 toward an open position at which the pilot fluid within air valve 60 is allowed to drain to sump 24 via an outlet port 83, thereby reducing the pressure within air valve 60.
Main poppet element 70 may include a nose portion 88 pivotally connected to a piston portion 90 that is movable in response to the pressure changes within air valve 60. Specifically, nose portion 88 may be connected to piston portion 90 by way of a pivot pin 92, and may be configured to selectively engage a valve seat 94. When nose portion 88 is engaged with valve seat 94, air from fluid passageway 64 may be substantially prevented from flowing toward filter elements 54 via venturi 58. However, when nose portion 88 is moved away from valve seat 94, pressurized air may freely flow through fluid passageway 64 and venturi 58 to aid in the regeneration of filtering elements 54. When the pilot fluid pressure acting on piston portion 90 exceeds the closing forces of the pressurized air acting on nose portion 88, nose portion 88 may remain engaged with valve seat 94. However, when the pilot fluid pressure within air valve 60 drops below the opening forces acting on nose portion 88, nose and piston portions 88, 90 may together be moved toward the open position to allow the pressurized air to flow from fluid passageway 64 through venturi 58 toward filtering elements 54. A sealing device 96 disposed between nose portion 88 and piston portion 90 may maintain separation between the pressurized air and the pressurized lubricant.

INDUSTRIAL APPLICABILITY

The disclosed exhaust treatment system may be applicable to any combustion-type device such as, for example, an engine, a furnace, or any other combustion device known in the art where the removal of particulate matter from an exhaust flow is desired. Exhaust treatment system 16 may be a simple, inexpensive, and efficient solution for reducing the amount of particulate matter exhausted to the environment without adversely affecting back pressure within the exhaust system. The operation of exhaust treatment system 16 will now be explained.
Atmospheric air may be drawn into air induction system 14 via compressor 42 where it may be pressurized to a predetermined level before entering the combustion chamber of power source 12. Fuel may be mixed with the pressurized air before or after entering the combustion chamber. This fuel-air mixture may then be combusted by power source 12 to produce mechanical work and an exhaust flow containing gaseous compounds and solid particulate matter. The exhaust flow may be directed via turbine 48 from power source 12 through filtering elements 54, where a substantial portion of the particulate matter entrained with the exhaust may be filtered from the exhaust flow. Over time, the particulate matter will build up within filtering elements 54 and, if left unchecked, could be significant enough to partially or even fully restrict the flow of exhaust through filtering elements 54, allowing for pressure within exhaust treatment system 16 to increase. An increase in the back pressure of power source 12 could reduce the ability to draw in fresh air, resulting in decreased performance of power source 12.
To accommodate the buildup of particulate matter within particulate trap 50, filtering elements 54 may be regenerated. Regeneration may be based on a triggering condition such as for example, a lapsed time of power source operation, a pressure differential measured across particulate trap 50, a temperature or pressure of the exhaust flow from power source 12, or any other condition known in the art.
To regenerate filtering elements 54, a stream of fuel from regeneration initiation device 56 and a flow of pressurized air from air valve 60 may be directed toward filtering elements 54. Under the high temperature environment within exhaust treatment system 16, the fuel/air mixture directed toward filtering elements 54 may ignite and increase the temperature of the entrained particulate matter to combustion.
To direct the flow of pressurized air toward filtering elements 54, a current may be applied to solenoid mechanism 66 that urges armature 72 and connected pin 74 downward toward main poppet element 70. As armature 72 and pin 74 move downward, pilot element 68 may be forced to the open position to drain the pressurized lubricant from air valve 60. As the pressure of the lubricant within air valve 60 decreases, the force exerted by the decreasing pressure on piston portion 90 may drop below the opening forces acting on nose portion 88, thereby causing nose portion 88 to move away from valve seat 94. As nose portion 88 moves away from valve seat 94, pressurized air may be allowed to flow from fluid passageway 64 toward filtering elements 54 via venturi 58.
Because air valve 60 is pilot-operated, the component and operating costs of exhaust treatment system 16 may be minimal. Specifically, because the force required to operate air valve 60 is derived from lubricant already pressurized for use within power source 12, the size of the solenoid utilized to actuate air valve 60 may be reduced, as compared to systems where the solenoid must exert the opening and closing forces. In addition, because the solenoid may be small, it may require little current to operate air valve 60. The reduced current requirements of air valve 60 may reduce the operating cost associated with exhaust treatment system 16 and, thereby, improve efficiency of work machine 10.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed exhaust treatment system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed exhaust treatment 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.

Claims

1. An exhaust treatment system for a power source, comprising:

an inlet configured to receive an exhaust flow from the power source;

a filtering medium configured to remove particulate matter from the exhaust flow;

an outlet configured to direct the exhaust flow from the filtering medium to the atmosphere;

a heating device configured to raise the temperature of the particulate matter entrained within the filtering medium;

a supply of pressurized air; and

a pilot-operated valve configured to selectively direct the pressurized air to the heated particulate matter.

2. The exhaust treatment system of claim 1, further including a supply of pilot fluid, wherein the pilot operated valve includes a valve element movable by the pilot fluid.

3. The exhaust treatment system of claim 2, wherein the pilot fluid includes a lubricant of the power source.

4. The exhaust treatment system of claim 2, wherein the pilot fluid includes a fuel of the power source.

5. The exhaust treatment system of claim 1, wherein the pilot-operated valve is solenoid-actuated.

6. The exhaust treatment system of claim 1, wherein the heating device is a fuel-powered burner.

7. The exhaust treatment system of claim 5, further including a single power source controller in communication with the power source and a solenoid of the pilot operated valve, the single power source controller configured to control operation of the power source and the pilot-operated valve.

8. A method of treating an exhaust flow of a power source, comprising:

directing the exhaust flow from the power source to a filtering medium to remove particulate matter from the exhaust flow;

directing the exhaust flow from the filtering medium to the atmosphere;

raising the temperature of the particulate matter entrained within the filtering medium; and

regulating a flow of pilot fluid to an air valve to selectively pass pressurized air to the heated particulate matter.

9. The method of claim 8, wherein the pilot fluid includes a lubricant of the power source.

10. The method of claim 8, wherein the pilot fluid includes a fuel of the power source.

11. The method of claim 8, wherein regulating a flow of pilot fluid includes pressurizing the pilot fluid and supplying the pilot fluid to a first valve element to move the first valve element.

12. The method of claim 11, wherein regulating further includes directing a current to a solenoid mechanism to move a second valve element.

13. The method of claim 8, further including heating the entrained particulate matter.

14. A work machine, comprising:

a power source configured to produce a power output and an exhaust flow; and

an exhaust treatment system configured to remove particulate matter from the exhaust flow, the exhaust treatment system including:

an inlet configured to receive the exhaust flow;

a supply of pressurized air; and

15. The work machine of claim 14, further including a supply of pilot fluid, wherein the pilot operated valve includes a valve element movable by the pilot fluid.

16. The work machine of claim 15, wherein the pilot fluid includes a lubricant of the power source.

17. The work machine of claim 15, wherein the pilot fluid includes a fuel of the power source.

18. The work machine of claim 14, wherein the pilot-operated valve is solenoid-actuated.

19. The work machine of claim 14, wherein the heating device is a fuel-powered burner.

20. The work machine of claim 19, further including a single power source controller in communication with the power source and a solenoid of the pilot operated valve, the single power source controller configured to control operation of the power source and the pilot-operated valve.