Fuel cell fluid machine

A fuel cell fluid machine, comprising:

• a rotary shaft;
• an electric motor that is configured to rotate the rotary shaft;
• a compression unit that is configured to use rotation of the rotary shaft to compress air supplied to a fuel cell stack;
• and
• a rotation assist unit that is configured to assist rotation of the rotary shaft, wherein the rotation assist unit includes:
• a turbine wheel that is provided on the rotary shaft and is configured to rotate integrally with the rotary shaft, the turbine wheel including blades;
• and
• a turbine housing that defines a turbine chamber and includes a shroud surface, the turbine chamber accommodating the turbine wheel, and the shroud surface facing an outer edge of each blade across an axial distance,
• the turbine wheel is configured such that an exhaust gas, which is discharged from the fuel cell stack and introduced to the turbine chamber, is conducted in a radial direction of the rotary shaft to the turbine wheel and discharged in an axial direction of the rotary shaft to rotate the turbine wheel, and
• a diameter of the shroud surface increases continuously across the axial distance in a flowing direction of the exhaust gas, and
• a diameter of each outer edge increases continuously, in the flowing direction of the exhaust gas, from a minimum diameter of each outer edge at an upstream side thereof across the axial distance.