Gas expander

A gas expander comprising:

• a casing where a swirl chamber is formed, wherein a gas to be expanded passes through the swirl chamber;
• a turbine wheel that is housed in the casing and rotationally driven by the gas, wherein the gas that rotationally drives the turbine wheel has passed through the swirl chamber and expanded;
• a diffuser that:
• is mounted to the casing in a direction of a rotating shaft of the turbine wheel, and includes a flow path where the gas, having passed through the turbine wheel, flows in the direction of the rotating shaft,
• a swirl stopper that:
• is disposed in the diffuser,
• faces a downstream front end surface of a boss of the turbine wheel that faces the flow path, and
• includes a closed swirl stopping surface that is disposed to face the downstream front end surface of the boss with a gap between the closed swirl stopping surface and the downstream front end surface;
• and
• a swirl preventing plate that circumferentially partitions the flow path,
• wherein L35≥D10×0.45 is satisfied, where L35 is an axial dimension of the swirl preventing plate and D10 is a diameter of the inlet of the flow path.

A gas expander comprising:

• a casing where a swirl chamber is formed, wherein a gas to be expanded passes through the swirl chamber;
• a turbine wheel that is housed in the casing and rotationally driven by the gas, wherein the gas that rotationally drives the turbine wheel has passed through the swirl chamber and expanded;
• a diffuser that:
• is mounted to the casing in a direction of a rotating shaft of the turbine wheel, and includes a flow path where the gas, having passed through the turbine wheel, flows in the direction of the rotating shaft,
• a swirl stopper that:
• is disposed in the diffuser,
• faces a downstream front end surface of a boss of the turbine wheel that faces the flow path, and
• includes a closed swirl stopping surface that is disposed to face the downstream front end surface of the boss with a gap between the closed swirl stopping surface and the downstream front end surface;
• and
• a swirl preventing plate that circumferentially partitions the flow path, wherein in the swirl stopper, the closed swirl stopping surface has a protruding peripheral edge and an inner side recessed from the peripheral edge, and
• the swirl stopper covers the downstream front end surface of the boss and an outer peripheral surface of the turbine wheel continuous with the downstream front end surface of the boss.