State quantity estimating device

A state quantity estimating device that estimates a state quantity of air compressed by a compressor comprising an impeller that compresses air and a housing that accommodates the impeller, the housing including a diffuser into which the air compressed by the impeller flows and a scroll into which the air flows through an outlet surface of the diffuser, wherein the state quantity estimating device is configured to:

• calculate a total enthalpy, which is energy based on an impeller outlet flow speed, which is a flow speed of air discharged by the impeller to the diffuser, and given to the air by the impeller, an adiabatic compression efficiency of the compressor, and a diffuser outlet flow speed, which is a flow speed of air in the outlet surface of the diffuser;
• allocate, to an internal energy and a pressure energy, a value obtained by subtracting a kinetic energy based on the diffuser outlet flow speed from the total enthalpy, based on the adiabatic compression efficiency;
• and
• calculate a compression temperature, which is a temperature of air flowing into the outlet surface, using an operational equation that includes, as variables, the internal energy and an inlet temperature, which is a temperature of air prior to being compressed by the impeller, and calculate a compression pressure, which is pressure of the air flowing into the outlet surface, using an operational equation that includes, as variables, the pressure energy and an inlet pressure, which is pressure of the air prior to being compressed by the impeller.