Expansion machine, power generation equipment and method for reducing friction between rotor and cylinder body

The invention discloses an expansion machine, power generation equipment and a method for reducing friction between a rotor and a cylinder body, the expansion machine comprises the cylinder body, a rotor assembly is arranged in the cylinder body, an air inlet and an air outlet which are communicated with the interior of the rotor assembly are formed in the cylinder body, a working gap is formed between the rotor assembly and the cylinder body, and an air supply channel is further formed in the cylinder body. A throttler is arranged between the air supply channel and the working gap, and an air cavity is formed between the working gap and the throttler. One part of the working medium gas enters a working cavity between the inner rotor and the outer rotor to expand and do work to push the main shaft to rotate; the other part enters the cylinder body after passing through the control valve; working medium gas with certain pressure enters the gas cavity through the throttler in the cylinder body, a layer of gas f