A Rankine cycle includes a refrigerant pump, a heat exchanger, an expander and a condenser. The Rankine cycle further includes a clutch provided in a power transmission path extending from an engine to the refrigerant pump. Prior to the operation of the Rankine cycle and during the deceleration of the vehicle, the clutch is fastened and the refrigerant pump is driven with use of the vehicle inertia force.
1. A Rankine cycle system for a vehicle driven by an engine that is cooled by refrigerant, the system comprising:
a refrigerant pump installed in the vehicle and circulating the refrigerant;
a heat exchanger collecting waste heat of the engine with the refrigerant;
an expander converting the waste heat collected with the refrigerant into driving force by expanding the refrigerant;
a condenser condensing the refrigerant expanded by the expander;
a power transmission path extending from the engine to the refrigerant pump, the power transmission path including a clutch;
a refrigerant path circulating the refrigerant among the refrigerant pump, the heat exchanger, the expander, and the condenser;
a bypass path connected to the refrigerant path to make the refrigerant bypass the expander; and
a controller configured to
determine whether a Rankine cycle operation condition is met;
perform a Rankine cycle operation of the Rankine cycle system, in which the clutch is fastened and the refrigerant pump is driven with a driving force of the engine while circulating the refrigerant through the refrigerant path without making the refrigerant bypass the expander, when the Rankine cycle operation condition is met; and
perform, prior to performing the Rankine cycle operation, a preliminary operation of the Rankine cycle system, in which the clutch is fastened and the refrigerant pump is driven with a vehicle inertia force while causing the bypass path to make the refrigerant bypass the expander, during deceleration of the vehicle.
2. The Rankine cycle system according to claim 1 , further comprising:
a bypass valve in the bypass path,
wherein the controller is further configured to open the bypass valve to cause the bypass path to make the refrigerant bypass the expander.
3. The Rankine cycle system according to claim 1 , wherein the controller is further configured to:
cause the bypass path to make the refrigerant bypass the expander to accumulate the refrigerant at an inlet of the refrigerant pump.
4. The Rankine cycle system according to claim 3 , wherein the controller is further configured to:
fasten the clutch and drive the refrigerant pump with the driving force of the engine while causing the bypass path to make the refrigerant bypass the expander, when no deceleration of the vehicle is conducted even upon a lapse of a predetermined time after the Rankine cycle operation condition is met.
5. The Rankine cycle system according to claim 3 , wherein the controller is further configured to:
keep the clutch fastened and drive the refrigerant pump with the driving force of the engine while causing the bypass path to make the refrigerant bypass the expander, when the deceleration of the vehicle is terminated before the refrigerant is accumulated at the inlet of the refrigerant pump during the preliminary operation.
6. The Rankine cycle system according to claim 1 , wherein the controller is further configured to:
perform the preliminary operation to eliminate an uneven distribution of the refrigerant in the Rankine cycle system, during the deceleration of the vehicle when the Rankine cycle operation condition is not met.
7. The Rankine cycle system according to claim 6 , wherein the controller is further configured to:
determine whether or not the uneven distribution of the refrigerant is present in the Rankine cycle system; and
release the clutch and terminate operation of the refrigerant pump, when the deceleration of the vehicle is terminated before the uneven distribution of the refrigerant in the Rankine cycle system is eliminated.
8. The Rankine cycle system according to claim 6 , wherein the controller is further configured to:
determine whether or not the uneven distribution of the refrigerant is present in the Rankine cycle system, and
when the Rankine cycle operation condition is not met and the uneven distribution of the refrigerant is present in the Rankine cycle system, perform the preliminary operation of the Rankine cycle system during the deceleration of the vehicle, to eliminate the uneven distribution of the refrigerant in the Rankine cycle system.
9. The Rankine cycle system according to claim 1 , wherein the controller is further configured to:
prevent the Rankine cycle operation from being performed in a high load zone or a high rotation speed zone of the engine; and
perform the preliminary operation only when the deceleration of the vehicle is accompanied by a fuel cut of the engine performed in the high load zone or high rotation speed zone.
10. The Rankine cycle system according to claim 1 , wherein the vehicle comprises an air conditioner associated with a freezer cycle system, and the Rankine cycle system shares the condenser and the refrigerant with the freezer cycle system.