Fluid machine and refrigeration cycle apparatus having the same

A fluid machine comprising:

• a closed casing having, in its bottom portion, an oil reservoir for containing oil;
• a main compression mechanism for compressing a working fluid, the main compression mechanism being disposed in the closed casing and supplied with oil contained in an upper portion of the oil reservoir;
• a rotation motor disposed above the oil reservoir in the closed casing and including a rotor and a stator;
• a main compression mechanism side shaft for coupling the main compression mechanism and the rotation motor so that the main compression mechanism is driven by the rotation motor;
• a mechanical power recovery mechanism for recovering mechanical power from the working fluid by carrying out at least a suction process in which the working fluid is drawn and a discharge process in which the drawn working fluid is discharged, the mechanical power recovery mechanism being disposed below the upper portion in the oil reservoir;
• a sub-compression mechanism for compressing the working fluid and discharging the compressed working fluid toward the main compression mechanism, the sub-compression mechanism being disposed below the upper portion in the oil reservoir;
• a mechanical power recovery shaft for coupling the mechanical power recovery mechanism and the sub-compression mechanism so that the sub-compression mechanism is driven by the mechanical power recovered by the mechanical power recovery mechanism;
• and
• at least one heat-insulating structure located between the upper portion and the mechanical power recovery mechanism so as to restrict flow of oil between the upper portion of the oil reservoir and a lower portion of the oil reservoir in which the mechanical power recovery mechanism is provided.