WO2017058204A1

WO2017058204A1 - Wax motor modulated engine gas recirculation (egr) temperature control for organic rankine cycle

Info

Publication number: WO2017058204A1
Application number: PCT/US2015/053237
Authority: WO
Inventors: James A. Zigan
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2017-04-06
Anticipated expiration: 2018-03-30

Abstract

An exhaust gas recirculation (EGR) system and method. Embodiments EGR system include a source of coolant such as ORC working fluid, an EGR cooler, a mechanically actuated valve, and a thermal actuator such as a wax motor. The EGR cooler includes a recirculated exhaust gas chamber having an input to receive exhaust gas and an output to couple the exhaust gas to an engine, and a coolant chamber having an input. The coolant chamber is thermally coupled to the exhaust gas chamber. The mechanically-actuated valve is coupled between the source of coolant and the coolant chamber input. The thermal actuator actuates the valve, and includes a body positioned to be thermally coupled to exhaust gas flowing from the exhaust gas chamber.

Description

WAX MOTOR MODULATED

ENGINE GAS RECIRCULATION (EGR) TEMPERATURE CONTROL

FOR ORGANIC RANKINE CYCLE

FIELD OF THE INVENTION

[0001] Embodiments of the invention relate to engine gas recirculation (EGR) control systems. In particular, embodiments of the invention related to temperature control of EGR systems.

BACKGROUND

[0002] Engine gas recirculation (EGR) and associated control systems are generally known and disclosed, by way of example, in the following U.S. patents and published applications, all of which are incorporated herein by reference for all purposes:

Inventor Name Patent/Publication No.

Kinomura et al. 2012/0160447

Kanou et al. 2013/0199178

Nelson et al. 2013/0019847

Ernst et al. 7,958,873

Takeishi et al. 8,402,757

[0003] In EGR systems of these types, a portion of the engine exhaust gas is collected and mixed with the primary combustion gas (e.g., oxygen in air) that is inputted into the engine combustion chamber. The inert exhaust displaces some of the spare oxygen in the engine to provide nitrogen oxide NO_x emissions reduction. Some EGR systems, such as those used in some diesel engines, cool the recirculated exhaust before it is inputted to the combustion chamber. EGR coolers can include a heat exchanger and a source of coolant or working fluid such as a glycol and water mixture, ethanol or other organic rankine cycle (ORC) working fluid to cool the exhaust gas. The EGR cooler can be controlled by a computerized engine control unit (ECU) having a temperature sensor that monitors the temperature of the recirculated exhaust gas, and a valve that regulates the flow of coolant to the EGR cooler from the source. The ECU actuates the valve to control the amount of coolant flowing into the heat exchanger based on the monitored exhaust gas temperature and a desired exhaust gas temperature to maintain the exhaust gas at a desired temperature.

[0004] There remains, however, a continuing need for improved EGR systems. In particular, there is a need for robust systems that can accurately control the temperatures of exhaust gas in EGR systems. Such a system that can be efficiently implemented would be especially desirable. SUMMARY

[0005] Embodiments of the invention include an exhaust gas recirculation (EGR) system, comprising a source of working fluid, an EGR cooler, a mechanically actuated valve, and a thermal actuator. The EGR cooler includes a recirculated exhaust gas chamber having an input to receive exhaust gas and an output to couple the exhaust gas to an engine, and a coolant chamber having an input. The coolant chamber is thermally coupled to the exhaust gas chamber. The mechanically-actuated valve is coupled between the source of working fluid and the coolant chamber input. The thermal actuator actuates the valve, and includes a body positioned to be thermally coupled to exhaust gas flowing from the exhaust gas chamber. In embodiments, the actuator is a wax motor.

[0006] Embodiments of the invention also include a method for regulating a flow of working fluid to an exhaust gas recirculation cooler. The method comprises thermally coupling a thermal actuator to recirculated exhaust gas flowing from the exhaust gas recirculation cooler, and actuating a mechanically-actuated valve by the thermal actuator to control working fluid flow to the exhaust gas recirculation cooler.

DESCRIPTION OF THE DRAWINGS

[0007] The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0008] FIG. 1 is a diagrammatic illustration of an engine system and exhaust gas recirculation (EGR) system in accordance with embodiments of the invention;

[0009] FIG. 2 is a detailed isometric illustration of portions of the EGR system shown in

FIG. l; and

[0010] FIG. 3 is a detailed sectional view of portions of the EGR system shown in FIG.

1.

[0011 ] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. DETAILED DESCRIPTION

[0012] FIG. 1 is an illustration of an engine system 8 including an exhaust gas recirculation (EGR) system 10 in accordance with embodiments of the disclosure. As shown, the engine system 8 includes an engine 12 having one or more combustion chambers 14. Engine 12 can, for example, be a diesel or gasoline engine. Embodiments of EGR system 10 include an EGR cooler 16, working fluid or coolant source 18 and thermo-mechanical control 20 for regulating the flow of coolant from the source to the cooler. EGR cooler 16 functions as a heat exchanger and includes an EGR chamber 22 and a coolant chamber 24 in a thermal, heat- exchanging relationship (e.g., in physical contact) with one another. An input port of EGR chamber 22 is coupled to receive exhaust gas from engine 12. Coolant or other working fluid (e.g., ORC working fluid) from source 18 flows through the coolant chamber 24, and transfers heat away from the EGR chamber 22 to cool the exhaust gas flowing through the EGR chamber.

[0013] Thermo-mechanical control 20 includes a thermal actuator 26 and a

mechanically-actuated valve 28. As shown diagrammatically in FIG. 1, the thermal actuator 20 is positioned to be thermally coupled to the exhaust gas flowing through the EGR chamber 22. Thermal actuator 20 is responsive to the temperature of the exhaust gas flowing from the EGR chamber 22, and includes an actuator portion such as a piston (described in greater detail below) that moves in response to changes in the temperature of the exhaust gas. The actuator portion of thermal actuator 20 is mechanically coupled to valve 28, and mechanically drives the valve to control the flow of coolant from the source 18 to the coolant chamber 16. In embodiments, thermal actuator 26 and valve 28 cooperate to continuously proportionally modulate the flow of coolant over a range such as no flow to a maximum flow to maintain the temperature of the exhaust gas flowing from the EGR chamber 22 within a desired temperature range. In embodiments, for example, EGR system operates to maintain the temperature of exhaust gas within a range of about 180° F. The cooled exhaust gas from EGR cooler 16 is recirculated back to the engine 12, where it is mixed by conventional or otherwise knows structures (e.g., with a primary combustion gas such as oxygen in air) before being injected into the combustion chambers 14.

[0014] Thermal actuator 26 can be a wax motor, and in particular a linear actuator, in embodiments of the disclosure. Wax motors of these types are known and commercially available. Briefly, they include an actuator, such as a piston, mounted within a body. Wax compositions within the body expand and contract in response to changes in temperatures to which the body is exposed, and the wax expansion and contraction is coupled to the piston that is driven or otherwise moves accordingly (e.g., extends from and retracts into the body).

Characteristics of the wax motor, including the volume and nature of the wax composition and the size of the piston, are configured to cause the piston to move over its range of motion over predetermined temperature ranges. Other types of thermal actuators can be used in other embodiments. For example, embodiments can include bimetallic members that expand and contract in response to temperature changes.

[0015] FIGs. 2 and 3 illustrate embodiments of portions of EGR system 10 in greater detail. As shown, thermal actuator 26, in the form of a wax motor, is mounted by a housing 32 to a manifold 34 having a port 36 at the outlet end of EGR chamber 22. Mechanically actuated valve 28 is mounted to the housing 32 for mechanical actuation by the wax motor thermal actuator 26. Also shown is the coolant chamber 24 and its input and output ports 38 and 40, respectively. The body 42 of actuator 26 extends into the housing, and includes fins 44 that extend into the manifold 34 and into direct contact with the recirculated exhaust gas flowing from the EGR cooler 16. In other embodiments (not shown), the body of the actuator 26 is indirectly thermally coupled to the recirculated exhaust gas, for example by being mounted to the exterior of the EGR chamber 22, its manifold 34, or other structure that is heated by the recirculated exhaust gas. Positioning the actuator 26 in direct contact with the exhaust gas can result in relatively fast and accurate control of coolant flow.

[0016] Valve 28 includes a body 45 that is attached to the housing 32, for example by fasteners 46. The body 45 has an inlet port 48, outlet port 50 and a seat 54 defining a channel between the inlet and outlet ports. A chamber 56 defined by a lip 57 in the valve body 45 communicates with the piston 43 extending from the body 42 of the actuator 26. Inlet port 48 of the valve body 45 is coupled to receive coolant from source 18, and outlet port 50 is coupled to the inlet port 38 of the of the coolant chamber 24. Valve head 60 is located in the channel defined by seat 54. A stem 62 extends from the valve head 60 into engagement with the piston 43 of actuator 26. In the embodiment shown, the channel defined by seat 54 is conically shaped and has an increasing diameter in the direction from the inlet port 48 to the outlet port 50. Valve head 60 has a conical shape that is complimentary to the shape of the channel between the ports 48 and 50. The valve head 60 is urged toward a closed position in the seat 54 by a biasing or return mechanism such as spring 66. In this embodiment, the wax motor actuator 26 is isolated from the coolant by a seal formed by lip 57, thereby allowing replacement of the actuator without the need to discharge coolant from the EGR system 10.

[0017] In operation, when the temperature of the recirculated exhaust gas is below the temperature range at which it needs to be cooled (e.g., upon start-up and warm-up of the engine 12), the piston 43 in actuator 26 will be retracted, and spring 66 will bias the valve head 60 to a closed position within the valve seat 54. No coolant from source 18 flows to the coolant chamber 16 during these engine 12 operating states when the valve 28 is closed. As the temperature of the recirculated exhaust reaches the temperature at which it requires cooling (e.g., about 180° F in embodiments), the piston 43 of actuator 26 is driven outwardly from the actuator body 42 and acts on the valve stem 62 to push head 60 out of the seat 54, thereby opening the channel defined by the seat and enabling coolant to flow to the coolant chamber 24 through the valve 28. The flow of coolant through the chamber 24 will cool the recirculated exhaust gas. As described above, actuator 26, in combination with the valve 28 (i.e., by continued extension and retraction of the actuator piston), operate to proportionally control and modulate the flow of coolant to the chamber 24 so as to maintain the temperature of the recirculated exhaust gas within the desire temperature range during operation of the engine 12. When the engine cools down and the temperature of the recirculated exhaust gas drops below the temperature at which cooling is needed (e.g., after the engine is stopped), the piston 43 of the actuator retracts a sufficient degree as to enable the spring 66 to cause the valve head 60 to close the valve 28.

[0018] Embodiments of the disclosure may offer important advantages. In particular they are efficient to manufacture and enable robust, accurate control of the recirculated exhaust gas temperature. While this invention has been described as having exemplary designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

CLAIMS What is claimed is:

1. An exhaust gas recirculation (EGR) system, comprising:

a source of working fluid;

an EGR cooler including:

a recirculated exhaust gas chamber having an input to receive exhaust gas and an output to couple the exhaust gas to an engine; and

a coolant chamber having an input and thermally coupled to the exhaust gas

chamber;

a mechanically-actuated valve coupled between the source of working fluid and the

coolant chamber input; and

a thermal actuator to actuate the valve, the thermal actuator including a body positioned to be thermally coupled to exhaust gas flowing from the exhaust gas chamber.

2. The EGR system of claim 1 wherein the thermal actuator is a wax motor.

3. The EGR system of claim 2 wherein the wax motor includes a piston in the body, and wherein the piston is mechanically coupled to the valve.

4. The EGR system of claim 3 wherein the wax motor is a linear actuator.

5. The EGR system of claim 4 wherein the body of the wax motor is positioned to be in direct contact with exhaust gas flowing from the exhaust gas outlet.

6. The EGR system of claim 5 wherein the valve includes:

a valve body comprising:

an inlet port configured to be coupled to the source of working fluid; an outlet port; and

a seat defining channel between the inlet and outlet ports; and

a valve head movably mounted with respect to the seat in the valve body, and wherein the head is mechanically engaged and driven by the piston of the wax motor to regulate working fluid flow through the channel.

7. The EGR system of claim 6 wherein the valve is configured to provide continuous proportional control of working fluid flow over a range of flow rates.

8. The EGR system of claim 1 wherein the thermal actuator includes a bimetallic member.

9. The EGR system of claim 1 , wherein the body of the thermal actuator is positioned to be in direct contact with exhaust gas flowing from the exhaust gas outlet.

10. The EGR system of claim 1 wherein the valve includes:

a valve body comprising:

a seat defining channel between the inlet and outlet ports; and

a valve head movably mounted with respect to the seat in the valve body, and wherein the head is mechanically coupled to and driven by the thermal actuator to regulate working fluid flow through the channel.

11. The EGR system of claim 10 wherein the valve is configured to provide continuous proportional control of working fluid flow over a range of flow rates.

12. The EGR system of claim 10 and further including a spring to bias the valve head to a closed position with respect to the seat.

13. The EGR system of claim 12 wherein:

the thermal actuator comprises a wax motor having a piston, and

the valve includes a stem extending from the valve head, and wherein the valve stem is mechanically coupled to the piston of the wax motor.

14. The EGR system of claim 1 wherein the valve is configured to provide continuous proportional control of working fluid flow over a range of flow rates.

15. A method for regulating a flow of working fluid to an exhaust gas recirculation cooler, comprising: thermally coupling a thermal actuator to recirculated exhaust gas flowing from the exhaust gas recirculation cooler; and

actuating a mechanically-actuated valve by the thermal actuator to control working fluid flow to the exhaust gas recirculation cooler.

16. The method of claim 15 wherein thermally coupling the thermal actuator to recirculated exhaust gas includes directly contacting the thermal actuator with the recirculated exhaust gas.

17. The method of claim 16 and further including continuously modulating the working fluid flow over a range of flow rates.