Fluid machinery, comprising: a rotating shaft; a cylinder, the axis of the rotating shaft and the axis of the cylinder being eccentric to each other and at a fixed eccentric distance; and a piston component, the piston component being provided with a variable volume cavity, the piston component being pivotally provided in the cylinder, and the rotating shaft being drivingly connected with the piston component to change the volume of the variable volume cavity; an upper flange; a lower flange, the cylinder being sandwiched between the upper flange and the lower flange, the piston component comprising: a piston sleeve, the piston sleeve being pivotally provided in the cylinder; and a piston, the piston being slidably provided in the piston sleeve to form the variable volume cavity, and the variable volume cavity being located in a sliding direction of the piston, the piston being provided with a sliding hole running through the axial direction of the rotating shaft, characterised in that the rotating shaft penetrates through the sliding hole, and the piston rotates along with the rotating shaft under the driving of the rotating shaft and slides in the piston sleeve along a direction vertical to the axial direction of the rotating shaft in a reciprocating manner, a lower end of the rotating shaft is located in the lower flange, wherein the sliding hole is a slotted hole, the rotating shaft is a one-piece structure, the rotating shaft is provided with a sliding segment in sliding fit with the piston component, the sliding segment is located between two ends of the rotating shaft, and the sliding segment is provided with sliding fit surfaces, the sliding fit surfaces are symmetrically provided on two sides of the sliding segment, the sliding fit surfaces are parallel with an axial plane of the rotating shaft, and the sliding fit surfaces are in sliding fit with an inner wall surface of the sliding hole of the piston in a direction vertical to the axial direction of the rotating shaft. a rotating shaft; a cylinder, the axis of the rotating shaft and the axis of the cylinder being eccentric to each other and at a fixed eccentric distance; and a piston component, the piston component being provided with a variable volume cavity, the piston component being pivotally provided in the cylinder, and the rotating shaft being drivingly connected with the piston component to change the volume of the variable volume cavity; an upper flange; a lower flange, the cylinder being sandwiched between the upper flange and the lower flange, the piston component comprising: a piston sleeve, the piston sleeve being pivotally provided in the cylinder; and a piston, the piston being slidably provided in the piston sleeve to form the variable volume cavity, and the variable volume cavity being located in a sliding direction of the piston, the piston being provided with a sliding hole running through the axial direction of the rotating shaft, characterised in that the rotating shaft penetrates through the sliding hole, and the piston rotates along with the rotating shaft under the driving of the rotating shaft and slides in the piston sleeve along a direction vertical to the axial direction of the rotating shaft in a reciprocating manner, a lower end of the rotating shaft is located in the lower flange, wherein the sliding hole is a slotted hole, the rotating shaft is a one-piece structure, the rotating shaft is provided with a sliding segment in sliding fit with the piston component, the sliding segment is located between two ends of the rotating shaft, and the sliding segment is provided with sliding fit surfaces, the sliding fit surfaces are symmetrically provided on two sides of the sliding segment, the sliding fit surfaces are parallel with an axial plane of the rotating shaft, and the sliding fit surfaces are in sliding fit with an inner wall surface of the sliding hole of the piston in a direction vertical to the axial direction of the rotating shaft.