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; a target pressure setter for setting a target pressure for the gas-phase working medium based on actual flow rate and temperature of the gas-phase working medium supplied to the expander; an estimated flow rate calculator for calculating an estimated flow rate of the gas-phase working medium supplied to the expander based on an output and a rotational speed of the engine; and a target rotational speed calculator for calculating a target rotational speed for the expander based on the estimated flow rate calculated by the estimated flow rate calculator and the target pressure set by the target pressure setter.

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;    target pressure setting means for setting a target pressure for the gas-phase working medium based on actual flow rate and temperature of the gas-phase working medium supplied to the expander;    estimated flow rate calculation means for calculating an estimated flow rate of the gas-phase working medium supplied to the expander, based on an output and a rotational speed of the engine; and    target rotational speed calculation means for calculating a target rotational speed for the expander based on the estimated flow rate calculated by the estimated flow rate calculation means and the target pressure set by the target pressure setting means.    
   
   
       2 . 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;    target pressure setting means for setting a target pressure for the gas-phase working medium based on actual flow rate and temperature of the gas-phase working medium supplied to the expander;    estimated flow rate calculation means for calculating an estimated flow rate of the gas-phase working medium supplied to the expander, based on a throttle opening degree or an accelerator opening degree of the engine, and a rotational speed of the engine; and    target rotational speed calculation means for calculating a target rotational speed for the expander based on the estimated flow rate calculated by the estimated flow rate calculation means and the target pressure set by the target pressure setting means.    
   
   
       3 . The Rankine cycle system according to  claim 1 , wherein the target rotational speed calculation means calculates a target rotational speed for the expander based on the estimated flow rate calculated by the estimated flow rate calculation means, the target pressure set by the target pressure setting means, and the temperature of the gas-phase working medium supplied to the expander.  
   
   
       4 . The Rankine cycle system according to  claim 3 , wherein the estimated flow rate calculation means calculates an exhaust gas flow rate based on the throttle opening degree and the rotational speed of the engine, calculates an exhaust gas energy from the exhaust gas flow rate and an exhaust gas temperature, and calculates the estimated flow rate from the exhaust gas energy and a target temperature of the gas-phase working medium supplied to the expander.  
   
   
       5 . The Rankine cycle system according to  claim 3 , wherein the estimated flow rate calculation means calculates an exhaust gas energy based on the throttle opening degree and the rotational speed of the engine, and calculates the estimated flow rate from the exhaust gas energy and a target temperature of the gas-phase working medium supplied to the expander.  
   
   
       6 . The Rankine cycle system according to  claim 2 , wherein the target rotational speed calculation means calculates a target rotational speed for the expander based on the estimated flow rate calculated by the estimated flow rate calculation means, the target pressure set by the target pressure setting means, and the temperature of the gas-phase working medium supplied to the expander.