Waste heat utilization device for internal combustion engine

Abstract

A waste heat utilization device () for an internal combustion engine has a Rankine cycle () that recovers waste heat from an internal combustion engine (), a generator () that is rotationally driven by an expander () and converts a rotational drive force into electric power, a converter () that controls the rotational speed of the expander () through the generator (), refrigerant-condition detecting means () that detects the pressure and temperature of a refrigerant passing through the expander (), and a controller () that calculates pressure ratio Rp of the refrigerant in the immediate upstream and downstream of the expander () and specific heat ratio K of the refrigerant passing through the expander () on the basis of the pressure and temperature of the refrigerant, which have been detected by the refrigerant-condition detecting means (), calculates a preset pressure ratio Rps of the pressure ratio Rp by multiplying predetermined volume ratio Rv of the expander () by the specific heat ratio K, and specifies rotational speed N of the expander () to the converter () on the basis of the pressure ratio Rp and the preset pressure ratio Rps.