Rankine cycle system

• US 20060254276A1
• Filed: 03/13/2006
• Published: 11/16/2006
• Est. Priority Date: 03/11/2005
• Status: Abandoned Application

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Fukutomi, Koji, Yamamoto, Kensaku, Sato, Akihisa
• Application Number:
  US11/373,134
• Publication Number:
  US 20060254276A1
• Time in Patent Office: Days
• US Class Current: 60/645
• CPC Class Codes: F01K 23/101 Regulating means specially adapted therefor F01K23/105, F01K23/108 take precedence

Abstract

A Rankine cycle system includes an evaporator for heating water with thermal energy of exhaust gas of an engine for generating steam with a displacement type expander for converting thermal energy into mechanical energy. A temperature controller manipulates the amount of water supplied to the evaporator so that the temperature of the steam supplied from the evaporator to the expander coincides with a target temperature. A pressure controller manipulates the rotational speed of the expander by changing a load of the expander so that the pressure of the steam supplied from the evaporator to the expander coincides with a target pressure. The temperature controller and/or the pressure controller continue to control the amount of water supplied to the evaporator and/or the rotational speed of the expander in set ranges at least in a state in which the engine has stopped and the thermal energy of the exhaust gas has disappeared.

Claims

1. A Rankine cycle system comprising:

an evaporator for heating a liquid-phase working medium with thermal energy of exhaust gas of an engine so as to generate a gas-phase working medium;

a displacement type expander for converting the thermal energy of the gas-phase working medium generated by the evaporator into mechanical energy;

temperature control means for manipulating the amount of liquid-phase working medium supplied to the evaporator so that the temperature of the gas-phase working medium supplied from the evaporator to the expander coincides with a target temperature; and

pressure control means for manipulating the rotational speed of the expander by changing a load of the expander so that the pressure of the gas-phase working medium supplied from the evaporator to the expander coincides with a target pressure,

wherein the temperature control means and/or the pressure control means continues to control the amount of liquid-phase working medium supplied to the evaporator and/or the rotational speed of the expander in set ranges at least in a state in which the engine has stopped and the thermal energy of the exhaust gas has disappeared.

2. The Rankine cycle system according to claim 1, wherein the temperature control means continues to supply the liquid-phase working medium to the evaporator until the temperature of the gas-phase working medium decreases to at least a temperature at which the expander does not generate an output.

3. The Rankine cycle system according to claim 1, wherein the pressure control means continues to control the rotational speed of the expander until the pressure of the gas-phase working medium decreases to at least a pressure at which the expander does not generate an output.

4. The Rankine cycle system according to claim 3, wherein when the rotational speed of the expander decreases to a set rotational speed, the pressure control means maintains the set rotational speed;

and when the expander attains a state in which no output is generated, the pressure control means stops controlling the rotational speed of the expander and allows the expander to rotate freely in a non-load state.

5. The Rankine cycle system according to claim 1, and further including feedforward water supply amount calculating means for calculating a feedforward water supply amount for the evaporator based on the engine rotational speed fuel injection quantity and the exhaust gas temperature of the engine.

6. The Rankine cycle system according to claim 1, and further including feedback water supply amount calculating means for calculating a feedback water supply amount based on a deviation of the steam temperature at the exit of the evaporator from a target steam temperature at the entrance of the expander by a predetermined gain.

7. The Rankine cycle system according to claim 1, and further including a water supply amount control changeover means for controlling the water supply amount for the evaporator according to the internal density of the evaporator when the ignition switch is turned OFF.

8. The Rankine cycle system according to claim 1, and further including a rotational speed calculating means for calculating a target rotational speed for a water supply pump based on a target water supply amount outputted by the water supply amount control changeover means and a steam pressure at the exit of the evaporator.

9. The Rankine cycle system according to claim 8, wherein the rotational speed of the motor is controlled for driving the water supply pump wherein the rotational speed coincides with the target rotational speed.

10. The Rankine cycle system according to claim 1, and further including a feedback term calculation means for calculating a target torque of a motor/generator based on a deviation of a rotational speed of the motor/generator from a target rotational speed outputted by a rotational speed control changeover means and a rotational speed of the expander is feedback-controlled by the target rotational speed by generating the target torque in the motor/generator.

11. A Rankine cycle system comprising:

an evaporator for heating a liquid-phase working medium with thermal energy of exhaust gas of an engine for generating a gas-phase working medium;

a displacement type expander for converting the thermal energy of the gas-phase working medium generated by the evaporator into mechanical energy;

a temperature controller for manipulating the amount of liquid-phase working medium supplied to the evaporator wherein the temperature of the gas-phase working medium supplied from the evaporator to the expander coincides with a target temperature; and

a pressure controller for manipulating the rotational speed of the expander by changing a load of the expander wherein the pressure of the gas-phase working medium supplied from the evaporator to the expander coincides with a target pressure,

wherein the temperature controller and/or the pressure controller continue to control the amount of liquid-phase working medium supplied to the evaporator and/or the rotational speed of the expander in set ranges at least in a state in which the engine has stopped and the thermal energy of the exhaust gas has disappeared.

12. The Rankine cycle system according to claim 11, wherein the temperature controller continues to supply the liquid-phase working medium to the evaporator until the temperature of the gas-phase working medium decreases to at least a temperature at which the expander does not generate an output.

13. The Rankine cycle system according to claim 11, wherein the pressure controller continues to control the rotational speed of the expander until the pressure of the gas-phase working medium decreases to at least a pressure at which the expander does not generate an output.

14. The Rankine cycle system according to claim 13, wherein when the rotational speed of the expander decreases to a set rotational speed, the pressure controller maintains the set rotational speed;

and when the expander attains a state in which no output is generated, the pressure controller stops controlling the rotational speed of the expander and allows the expander to rotate freely in a non-load state.

15. The Rankine cycle system according to claim 11, and further including a feedforward water supply amount calculator for calculating a feedforward water supply amount for the evaporator based on the engine rotational speed fuel injection quantity and the exhaust gas temperature of the engine.

16. The Rankine cycle system according to claim 11, and further including a feedback water supply amount calculator for calculating a feedback water supply amount based on a deviation of the steam temperature at the exit of the evaporator from a target steam temperature at the entrance of the expander by a predetermined gain.

17. The Rankine cycle system according to claim 11, and further including a water supply amount control changeover for controlling the water supply amount for the evaporator according to the internal density of the evaporator when the ignition switch is turned OFF.

18. The Rankine cycle system according to claim 11, and further including a rotational speed calculator for calculating a target rotational speed for a water supply pump based on a target water supply amount outputted by the water supply amount control changeover and a steam pressure at the exit of the evaporator.

19. The Rankine cycle system according to claim 18, wherein the rotational speed of the motor is controlled for driving the water supply pump wherein the rotational speed coincides with the target rotational speed.

20. The Rankine cycle system according to claim 11, and further including a feedback term calculator for calculating a target torque of a engine based on a deviation of a rotational speed of the engine from a target rotational speed outputted by a rotational speed control changeover and a rotational speed of the expander is feedback-controlled by the target rotational speed by generating the target torque in the engine.