RANKINE CYCLE LOAD LIMITING THROUGH USE OF A RECUPERATOR BYPASS

• US 20090241543A1
• Filed: 03/31/2008
• Published: 10/01/2009
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Ernst, Timothy C.
• Granted Patent: US 7,997,076 B2
• Time in Patent Office: Days
• US Class Current: 60/645
• CPC Class Codes: F01K 13/02 Controlling, e.g. stopping or starting
• CPC Class Codes: F01K 25/08 using special vapours
• CPC Class Codes: F01K 9/04 with dump valves to by-pass stages

Abstract

A system for converting heat from an engine into work includes a boiler coupled to a heat source for transferring heat to a working fluid, a turbine that transforms the heat into work, a condenser that transforms the working fluid into liquid, a recuperator with one flow path that routes working fluid from the turbine to the condenser, and another flow path that routes liquid working fluid from the condenser to the boiler, the recuperator being configured to transfer heat to the liquid working fluid, and a bypass valve in parallel with the second flow path. The bypass valve is movable between a closed position, permitting flow through the second flow path and an opened position, under high engine load conditions, bypassing the second flow path.

Claims

1. A system for converting waste heat from an engine into work, including:

a boiler coupled to a waste heat source for transferring heat to a working fluid;

a turbine configured to receive the working fluid from the boiler and to transform heat in the working fluid into motive work;

a condenser coupled to a low temperature source for transforming working fluid in a gaseous state into working fluid in a liquid state;

a recuperator having a first flow path that routes gaseous working fluid from the turbine to the condenser, and a second flow path that routes liquid working fluid from the condenser to the boiler, the recuperator being configured to transfer heat from the gaseous working fluid to the liquid working fluid; and

a bypass valve coupled between the condenser and the boiler in parallel with the second flow path, the bypass valve being movable between a closed position under normal engine load conditions, thereby permitting working fluid to flow through the second flow path instead of the bypass valve and an opened position under high engine load conditions, thereby permitting at least a portion of the working fluid to flow from the condenser to the boiler without flowing through the second flow path.

2. The system of claim 1 wherein the bypass valve is moved to the opened position to maintain a temperature of the waste heat below a predetermined maximum temperature.

3. The system of claim 1 wherein the waste heat source is one of an EGR loop, engine coolant and charge air.

4. The system of claim 1, further including a pump coupled to an output of the condenser and configured to increase the pressure of the liquid working fluid provided to the bypass valve and the recuperator.

5. The system of claim 1, further including a sensor configured to sense a temperature of waste heat exiting the boiler, wherein the waste heat temperature is indicative of the engine load conditions.

6. The system of claim 5, further including a controller coupled to the sensor and the bypass valve, the controller causing the bypass valve to move to the closed position when an output signal from the sensor indicates normal engine load conditions and causing the bypass valve to move toward the opened position when the sensor the output signal indicates high engine load conditions.

7. A waste heat recovery system, including:

a recuperator configured to cool gas provided though a first flow path of the recuperator from a turbine to a condenser and to heat liquid provided through a second flow path of the recuperator from the condenser to a boiler;

a valve connected in parallel with the second flow path and having an opened position for bypassing the second flow path; and

a controller being configured to place the valve in the opened position under high load operating conditions.

8. The system of claim 7 wherein the turbine is configured to convert high temperature gas from the boiler into motive work.

9. The system of claim 7 wherein the boiler extracts heat from a waste heat source of a diesel engine.

10. The system of claim 9 wherein the valve is moved to the opened position to maintain a temperature of waste heat from the waste heat source below a predetermined maximum temperature.

11. The system of claim 10 wherein the waste heat source is exhaust gas circulating in an EGR loop.

12. The system of claim 7 wherein the valve is in a closed position under normal load operating conditions, thereby causing the liquid to flow through the second flow path.

13. The system of claim 7, further including a pump coupled to an output of the condenser and configured to increase the pressure of the liquid leaving the condenser.

14. The system of claim 7, further including a sensor to determine whether the system is operating under high load operating conditions or normal load operating conditions.

15. The system of claim 14, further including a controller coupled to the sensor and the valve, the controller causing the valve to move toward the opened position when the sensor determines that the system is operating under high load operating conditions.

16. A waste heat recovery system for converting waste heat from a waste heat source of an engine into usable work while maintaining a temperature of the waste heat below a predetermined maximum value, the system including:

a recuperator configured to add heat to the low pressure side of a Rankine cycle including a turbine, a condenser, a pump, and a boiler; and

means for bypassing the recuperator when the engine is operating under high load conditions to maintain the waste heat temperature below the predetermined maximum value.

17. The system of claim 16, further including means for controlling the bypassing means in response to an output from means for sensing the high load conditions.

18. The system of claim 16 wherein the bypassing means includes a valve coupled between an outlet of the pump and an inlet of the boiler in parallel with the recuperator.

19. The system of claim 16 wherein the waste heat source is an EGR loop.

20. The system of claim 16 wherein a maximum power of the turbine corresponds to normal load conditions of the engine.