Rankine cycle system for vehicle having dual fluid circulation circuit and method of controlling the same

A method of controlling a Rankine cycle system for a vehicle having a dual fluid circulation circuit, comprising:

• A) performing a system diagnosis on the Rankine cycle system in which an HT loop having a high temperature boiler, a high temperature superheater, a high temperature expander, a high temperature condenser, a high temperature pump, a high temperature electronic expansion valve, and a high temperature fluid reservoir, and an LT loop having a low temperature boiler, a low temperature superheater, a low temperature expander, a low temperature recuperator, a low temperature condenser, a low temperature pump, a low temperature electronic expansion valve, and a low temperature fluid reservoir are connected to an engine, the step of performing the system diagnosis comprising:
• 1) initializing the HT loop and the LT loop by a Rankine controller when the engine is started,
• 2) determining, by a system error check on components of the HT loop and the LT loop, whether an error is generated,
• 3) when it is determined that an error has been generated, controlling states of the components of the HT loop and the LT loop and then repeating the system error check;
• B) when it is determined that the error is not generated after performing the system error check, determining whether or not a temperature of the high temperature superheater of the HT loop exceeds an HT upper limit;
• C) performing HT loop operation comprising maintaining an exhaust bypass valve in a turned-off state and controlling the HT loop is after it is determined that the temperature of the high temperature superheater of the HT loop does not exceed the HT upper limit;
• D) turning on the high temperature bypass valve to determine a bypass condition of a high temperature working fluid circulated in the HT loop on the high temperature expander;
• E) determining whether or not the temperature of the high temperature superheater of the HT loop exceeds an HT warm-up temperature when the high temperature bypass valve is turned on;
• F) when it is determined that the temperature of the HT superheater does not exceed the HT warm-up temperature when the HT bypass valve is turned on, determining whether or not a temperature of the low temperature superheater of the LT loop exceeds an LT upper limit;
• G) repeating the system error check when it is determined that the temperature of the low temperature superheater of the LT loop exceeds the LT upper limit
• H) when it is determined that the temperature of the LT superheater does not exceed the LT upper limit, determining whether or not a temperature of engine coolant exceeds an engine coolant temperature upper limit;
• I) performing LT loop operation comprising turning on a radiator bypass valve and then controlling the LT loop after it is determined that a temperature of engine coolant does not exceed the engine coolant temperature upper limit when the temperature of the low temperature superheater does not exceed the LT upper limit;
• J) turning on the low temperature bypass valve until a warm up condition of a low temperature working fluid circulated in the LT loop on the low temperature expander is satisfied;
• K) determining whether or not the LT superheater exceeds an LT warm-up temperature when the low temperature bypass valve is turned on;
• L) if it is determined that the LT superheater does not exceed the LT warm-up temperature when the LT bypass valve is turned on, repeating the system error check;
• and
• M) if it is determined that the LT superheater exceeds the LT warm-up temperature when the LT bypass valve is turned on, turning off the LT bypass valve and then repeating the system error check.