The basic components of the screw expansion power machine body are a pair of screws and the casing. The working steam first enters into the screw slot a and drives the male and female screws to rotate in the opposite direction. With the rotation of the screw, the slot a rotates to the positions of B, C and D. the stroke gradually lengthens and the volume increases. The fluid reduces pressure and expands (flashes) to work, and finally discharges from the slot E, The power is output from the spindle male rotor.
