WO2012102700A1

WO2012102700A1 - Rankine cycle expander bypass and orifice and method controlling same

Info

Publication number: WO2012102700A1
Application number: PCT/US2011/022331
Authority: WO
Inventors: John Zagone; Deokkyu Park; Robert L. Rowells; Chunyi XIA; Daniel Cornelius; Raul Espinosa
Original assignee: International Engine Intellectual Property Co LLC
Current assignee: International Engine Intellectual Property Co LLC
Priority date: 2011-01-25
Filing date: 2011-01-25
Publication date: 2012-08-02
Anticipated expiration: 2013-07-25

Abstract

An internal combustion engine comprises an exhaust system, an air intake system, and exhaust gas recirculation portion, a heat recovery turbine, and a fluid bypass valve. The exhaust gas recirculation portion has a first cooler, a second cooler, and an exhaust gas recirculation valve. The exhaust gas recirculation portion is in fluid communication with the exhaust system and the air intake system. The heat recovery turbine is disposed in fluid communication with coolant passing through the first cooler and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve is disposed in fluid communication with the heat recovery turbine and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve has a first position and a second position.

Description

RANKTNE CYCLE EXPANDER BYPASS AND ORIFICE AND METHOD

CONTROLLING SAME

DESCRIPTION

TECHNICAL FIELD

[0001] The present disclosure relates to a Rankine cycle waste heat recovery system and method of controlling the same on an internal combustion engine. More particularly, the present disclosure relates to a Rankine cycle heat waste recovery system utilizing coolant from an exhaust gas recirculation cooler and a method of controlling the same.

BACKGROUND

[0002] Many modern diesel engines utilize exhaust gas recirculation ("EGR") in order to reduce certain emissions in the exhaust, particularly nitrogen oxides ("ΝΟχ"). In order to maintain engine power outputs that are acceptable to users, most engines have an EGR cooler, where the exhaust gas in the EGR system is cooled before it is mixed with intake air and provided to the engine for use in combustion. The cooling fluid used in the EGR cooler receives a large amount of heat from the exhaust gas, and may vaporize the cooling fluid. Therefore, this heat within the cooling fluid may be utilized in a Rankine cycle waste heat recovery system to generate useable energy, such as electrical energy, or mechanical energy. Vaporized cooling fluid may in turn pass through a turbine where the fluid is allowed to expand, thus causing the turbine to rotate. The rotation of the turbine may typically generate electrical power. Therefore, useable energy is reclaimed from the heat of the coolant passed through the EGR cooler.

[0003] However, in certain operating conditions, such as soon after engine starting, engine operations in a cold ambient temperature, or when EGR rates are low, insufficient heat may be transferred to the coolant passing through the EGR cooler to vaporize the coolant. If the coolant in the EGR cooler does not vaporize, liquid in the coolant may damage the turbine. Therefore, a need exists for a Rankine cycle waste heat recovery system that controls a flow of EGR coolant to the turbine.

SUMMARY

[0004] According to one embodiment, an internal combustion engine comprises an exhaust system, an air intake system, and exhaust gas recirculation portion, a heat recovery turbine, and a fluid bypass valve. The exhaust gas recirculation portion has a first cooler, a second cooler, and an exhaust gas recirculation valve. The exhaust gas recirculation portion is in fluid communication with the exhaust system and the air intake system. The heat recovery turbine is disposed in fluid communication with coolant passing through the first cooler and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve is disposed in fluid communication with the heat recovery turbine and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve has a first position and a second position.

[0005] According to another embodiment, an exhaust gas recirculation system comprises an exhaust gas recirculation valve, a first exhaust gas recirculation cooler, a second exhaust gas recirculation cooler, a heat recovery turbine, and a fluid bypass valve. The exhaust gas recirculation valve is disposed in fluid communication with an exhaust system and an intake system. The first exhaust gas recirculation cooler is provided for receiving a coolant. The second exhaust gas recirculation cooler is disposed upstream of the first exhaust gas recirculation cooler, and is provided for receiving the coolant from the first exhaust gas recirculation cooler. The heat recovery turbine is selectively disposed in fluid

communication with the second exhaust gas recirculation cooler. The fluid bypass valve is disposed in fluid communication with the heat recovery turbine and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve is provided for controlling the selective fluid communication of the heat recovery turbine and the second cooler of the exhaust gas recirculation portion. The fluid bypass valve has a first position and a second position. The first position prevents coolant from the second cooler of the exhaust gas recirculation portion from entering the heat recovery turbine.

[0006] According to one process, a method of controlling coolant flow to a heat recovery turbine in an exhaust gas recirculation system that comprises an exhaust gas recirculation cooler, an exhaust gas recirculation valve, a heat recovery turbine, and a fluid bypass valve is provided. A temperature of a fluid exiting an exhaust gas recirculation cooler is determined. The temperature of the fluid exiting the exhaust gas recirculation cooler is compared to a stored predefined temperature. The fluid bypass valve opens when the temperature of the fluid exiting the exhaust gas recirculation cooler is below the stored predefined temperature preventing fluid flow to the heat recovery turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a schematic diagram showing an engine having a waste heat recovery system according to one embodiment [0008] FIG. 2 is a schematic diagram showing an engine having a waste heat recovery system according to another embodiment.

DETAILED DESCRIPTION

[0009] FIG. 1 shows an engine 10 connected to an electric motor and generator 12 and a transmission 14. The engine 10 has an exhaust system 16. The exhaust system 16 has an exhaust gas recirculation ("EGR") portion 18. The EGR portion 18 has a first EGR cooler 20, a second EGR cooler 22 and an EGR valve 24. The first and second EGR coolers 20, 22 reduce the temperature of exhaust gas within the EGR portion 18. The exhaust system 16 additionally is shown as having a high pressure turbocharger turbine 26 and a low pressure turbocharger turbine 28. The EGR valve 24 controls the flow of exhaust gas within the EGR portion 18.

[0010] The engine 10 additionally has an air intake system 30. The air intake system 30 has a low pressure turbocharger compressor 32 and a high pressure turbocharger compressor 34. A low pressure charge air cooler 36 is provided to cool intake air within the air intake system 30 following the low pressure turbocharger compressor 32, and a high pressure charge air cooler 38 is provided after the high pressure turbocharger compressor 34. A throttle valve 40 is also disposed within the air intake system 30. The low pressure turbocharger turbine 28 and the low pressure turbocharger compressor 32 form a first turbocharger and the high pressure turbocharger turbine 26 and the high pressure turbocharger compressor 34 form a second turbocharger. It is contemplated that the first turbocharger and the second turbocharger may be variable geometry turbochargers.

[0011] Coolant from the second EGR cooler 22 flows to a heat recovery turbine 42. The heat recovery turbine uses the Rankine cycle in order to allow the heat recovery turbine to rotate and generate torque used to turn a heat recovery generator 44 that generates electrical energy. An inverter and voltage controller 46 control the output of the heat recovery generator 44 and allow the electrical energy to be passed to a high voltage bus 48 of a vehicle containing the engine 10.

[0012] A bypass valve 50 is provided between the second EGR cooler 22 and the heat recovery turbine 42. The bypass valve 50 allows at least a portion of the coolant from the second EGR cooler 22 to bypass the heat recovery turbine 42 when the bypass valve 50 is positioned in at least a partially open position. When the bypass valve 50 is in a fully open position, all of the coolant from the second EGR cooler 22 bypasses the heat recovery turbine 42, and when the bypass valve 50 is in a fully closed position, all of the coolant from the second EGR cooler 22 flows through the heat recovery turbine 42. It is contemplated that the bypass valve 50 may include an orifice to reduce the pressure of flow through the bypass valve 50.

[0013] Coolant that has passed through the heat recovery turbine 42 or the bypass valve 50 is delivered to a recuperator 52. The recuperator 52 allows coolant to be pre-heated before being provided to the first EGR cooler 20, depending on operating conditions of the engine 10.

[0014] Coolant exiting the recuperator 52 is provided to a heat exchanger assembly 54. The heat exchanger assembly 54 ay include a condenser and a radiator in order to lower the temperature of the coolant. Next, coolant is delivered to an accumulator 56. The

accumulator is in fluid communication with a low pressure pump 58. The low pressure pump 58 is contemplated to raise the pressure of the coolant to a range from about one bar to about four bar (1-4 bar). The low pressure pump 58 is in fluid communication with a filter 60 that removes foreign materials from the coolant. A high pressure pump 62 receives coolant from the filter 60. The high pressure pump 62 is contemplated to raise the pressure of the coolant to a range from about fifteen bar to about twenty five bar (15-25 bar). Coolant exiting the high pressure pump 62 flows through a check valve 64 and to a distributor 66. The check valve 64 prevents backflow within the coolant system.

[0015] The distributor 66 has a plurality of outlets that allow coolant to flow to various components. For example, coolant may be provided to the first EGR cooler 20, to the low pressure charge air cooler 36, or to the recuperator 52. A charge air cooler valve 68 controls the flow of coolant from the distributor 66 to the low pressure charge air cooler 36.

Similarly, a recuperator valve 70 controls the flow of coolant from the distributor 66 to the recuperator 52. Coolant that flows to the recuperator 52 is heated by the coolant that has left the heat recovery turbine 42 or passed through the bypass valve 50, before being provided to the first EGR cooler 20. Thus, the recuperator 52 allows the coolant entering the first EGR cooler 20 to be at a higher temperature than coolant that does not pass through the recuperator 52. Therefore, in certain operating conditions, the recuperator 52 allows the heat recovery turbine 42 to be used when it otherwise would not, as the coolant is at a sufficient temperature to be in a vapor state.

[0016] Turning now to FIG. 2, a flow chart for a control system for the bypass valve 50 is shown. A temperature of coolant exiting the second EGR cooler 22 is measured at block 100. The measured temperature of the coolant is compared to a predetermined threshold temperature at block 102 to determine if the coolant temperature is above the threshold temperature, If the coolant temperature is not above the threshold temperature, the bypass valve 50 is opened at block 104. It is contemplated that the bypass valve 50 is placed in a fully open position at block 104, as the predetermined temperature is selected to ensure that the coolant is fully vaporized. Therefore, if the coolant is not fully vaporized, a risk of allowing liquid coolant to flow through the heat recovery turbine 42 is present, and the liquid may damage the heat recovery turbine 42.

[0017] If the temperature of the coolant exiting the second EGR cooler 22 is above the predetermined threshold at block 102, the pressure of the coolant exiting the second EGR cooler 22 is measured at block 106. The measured coolant pressure is compared to a predetermined coolant pressure threshold at block 108. If the measured coolant pressure is above the predetermined coolant pressure threshold, the bypass valve 50 is opened as shown at block 110. The opening of the bypass valve 50 in response to the pressure being above the predetermined threshold reduces the pressure of coolant passing through the heat recovery turbine 42, reducing the likelihood of damage to the heat recovery turbine 42. It is contemplated that an amount of opening of the bypass valve 50 may vary depending on the difference between the measured pressure and the predetermined pressure threshold. For instance, if the measured pressure greatly exceeds the predetermined threshold, the bypass valve 50 may be fully opened, however, if the measured pressure is close to the

predetermined threshold, the bypass valve 50 may only be partially opened, thereby relieving pressure in the coolant, while also allowing some coolant to flow to the heat recovery turbine 42. Therefore, it is contemplated that a plurality of predetermined pressure thresholds exist, a first predetermined threshold that results in a fully open bypass valve 50, and a second threshold that results in a partially open bypass valve 50, the second threshold being a lower pressure than the first threshold.

[0018] If the pressure of the coolant exiting the second EGR cooler 22 is below the predetermined threshold, the turbine speed is compared to a predetermined maximum turbine speed, as shown at block 112. If the turbine speed is above the predetermined threshold, the bypass valve 50 is opened, to reduce an amount of coolant passing through the heat recovery turbine 42. Reducing the amount of coolant passing through the heat recovery turbine 42 reduces the speed of the heat recovery turbine 42.

[0019] It will be understood that a control system may be implemented in hardware to effectuate the method. The control system can be implemented with any or a combination of the following technologies, which are each well known in the art: a discrete logic circuit(s) having logic gates for implementing logic functions upon data signals, an application specific integrated circuit (ASIC) having appropriate combinational logic gates, a programmable gate array(s) (PGA), a field programmable gate array (FPGA), etc.

[0020] When the control system is implemented in software, it should be noted that the control system can be stored on any computer readable medium for use by or in connection with any computer related system or method. In the context of this document, a "computer- readable medium" can be any medium that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic) having one or more wires, a portable computer diskette (magnetic), a random access memory (RAM) (electronic), a read-only memory (ROM) (electronic), an erasable programmable read-only memory (EPROM, EEPROM, or Flash memory) (electronic), an optical fiber (optical) and a portable compact disc read-only memory (CDROM) (optical). The control system can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions.

Claims

CLAIMS What is claimed is:

1. An internal combustion engine comprising:

an exhaust system;

an air intake system;

an exhaust gas recirculation portion having a first cooler, a second cooler, and an exhaust gas recirculation valve, the exhaust gas recirculation portion being in fluid communication with the exhaust system and the air intake system;

a heat recovery turbine disposed in fluid communication with coolant passing through the first cooler and the second cooler of the exhaust gas recirculation portion; and

a fluid bypass valve disposed in fluid communication with the heat recovery turbine and the second cooler of the exhaust gas recirculation portion, the fluid bypass valve having a first position and a second position.

2. The internal combustion engine of claim 1, wherein the first position of the fluid bypass valve allows fluid flow to the heat recovery turbine.

3. The internal combustion engine of claim 1, wherein the second position of the fluid bypass valve prevents fluid flow to the heat recovery turbine.

4. The internal combustion engine of claim 1, further comprising a turbocharger, the turbocharger having a turbine in fluid communication with the exhaust system and a compressor disposed in fluid communication with the air intake system.

5. The internal combustion engine of claim 1, wherein the bypass valve further comprises a pressure reducing orifice.

6. The internal combustion engine of claim 1 , further comprising a recuperator disposed in fluid communication with the heat recovery turbine and the fluid bypass valve and disposed downstream of both the heat recovery turbine and the fluid bypass valve.

7. The internal combustion engine of claim 1, further comprising an accumulator disposed in fluid communication with the heat recovery turbine and the fluid bypass valve and disposed downstream of both the heat recovery turbine and the fluid bypass valve.

8. The internal combustion engine of claim 1, further comprising a high pressure pump disposed in fluid communication with the first cooler, the high pressure pump pressurizing fluid to a high pressure fluid state.

9. An exhaust gas recirculation system comprising:

an exhaust gas recirculation valve disposed in fluid communication with an exhaust system and an intake system; a first exhaust gas recirculation cooler being provided for receiving a coolant;

a second exhaust gas recirculation cooler, the second exhaust gas recirculation cooler being disposed upstream of the first exhaust gas recirculation cooler, and being provided for receiving the coolant from the first exhaust gas recirculation cooler;

a heat recovery turbine selectively in fluid communication with the second exhaust gas recirculation cooler; and

a fluid bypass valve disposed in fluid communication with the heat recovery turbine and the second cooler of the exhaust gas recirculation portion, the fluid bypass valve being provided for controlling the selective fluid communication of the heat recovery turbine and the second cooler of the exhaust gas recirculation portion, the fluid bypass valve having a first position and a second position, the first position preventing coolant from the second cooler of the exhaust gas recirculation portion from entering the heat recovery turbine.

10. The exhaust gas recirculation system of claim 9, wherein the second position of the fluid bypass valve directs all the coolant from the second cooler of the exhaust gas recirculation portion to the heat recovery turbine.

11. The exhaust gas recirculation system of claim 10, wherein the fluid bypass valve having a third position, the fluid bypass valve preventing a portion of coolant from entering the heat recovery turbine in the third position.

12. The exhaust gas recirculation system of claim 9, wherein the bypass valve additionally has a pressure reducing orifice.

13. The exhaust gas recirculation system of claim 9, further comprising a recuperator disposed in fluid communication with the heat recovery turbine and the fluid bypass valve and disposed downstream of both the heat recovery turbine and the fluid bypass valve.

14. The exhaust gas recirculation system of claim 9, further comprising an accumulator disposed in fluid communication with the heat recovery turbine and the fluid bypass valve and disposed downstream of both the heat recovery turbine and the fluid bypass valve.

15. The exhaust gas recirculation system of claim 9, further comprising a high pressure pump disposed in fluid communication the first cooler, the high pressure pump pressurizing fluid to a high pressure fluid state.

16. The exhaust gas recirculation system of claim 9, further comprising a heat exchanger assembly disposed in fluid communication with the heat recovery turbine and the fluid bypass valve and disposed downstream of both the heat recovery turbine and the fluid bypass valve.

17. The exhaust gas recirculation system of claim 9, wherein exhaust entering the second exhaust gas recirculation cooler has a higher temperature than exhaust entering the first exhaust gas recirculation cooler.

18. A method of controlling coolant flow to a heat recovery turbine in an exhaust gas recirculation system comprising an exhaust gas recirculation cooler; an exhaust gas recirculation valve; a heat recovery turbine, and a fluid bypass valve, the method comprising: determining a temperature of a fluid exiting an exhaust gas recirculation cooler; comparing the temperature of the fluid exiting the exhaust gas recirculation cooler to a stored predefined temperature;

opening the fluid bypass valve when the temperature of the fluid exiting the exhaust gas recirculation cooler is below the stored predefined temperature preventing fluid flow to the heat recovery turbine.

19. The method of claim 18 further comprising:

determining a pressure of a fluid exiting an exhaust gas recirculation cooler;

comparing the pressure of the fluid exiting the exhaust gas recirculation cooler to a first stored predefined pressure;

opening the fluid bypass valve a first amount when the pressure of the fluid exiting the exhaust gas recirculation cooler is above the first stored predefined temperature.

20. The method of claim 18 further comprising:

comparing the pressure of the fluid exiting the exhaust gas recirculation cooler to a second stored predefined pressure, the second stored predefined pressure being higher than the first predefined pressure;

opening the fluid bypass valve a second amount when the pressure of the fluid exiting the exhaust gas recirculation cooler is above the first stored predefined temperature, the second amount being greater than the first amount.