Rankine cycle system

Abstract

A Rankine cycle system includes: 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; and a Rankine controller for manipulating an 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 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. Simultaneously with operating conditions of the engine shifting to a fuel supply suspension state or a low load state, the Rankine controller suspends supply of the liquid-phase working medium to the evaporator, and decreases the rotational speed of the expander as quickly as possible within a range in which the pressure of the gas-phase working medium does not exceed the target pressure.

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 an 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, simultaneously with operating conditions of the engine shifting to a fuel supply suspension state or a low load state, the temperature control means suspends supply of the liquid-phase working medium to the evaporator, and the pressure control means decreases the rotational speed of the expander as quickly as possible within a range in which the pressure of the gas-phase working medium does not exceed the target pressure.    
   
   
       2 . The Rankine cycle system according to  claim 1  wherein, simultaneously with recovery of the operating conditions of the engine from the fuel supply suspension state or the low load state, the temperature control means increases supply of the liquid-phase working medium to the evaporator, and the pressure control means increases the rotational speed of the expander.