A single stage cryogenic liquid turbine is designed for a large-scale internal compression air-separation unit to replace the Joule-Thompson valve and recover energy from the liquefied air during throttling process. It includes a 3-dimensional impeller, variable geometry nozzle, and asymmetrical volute. Strength evaluation of such a liquid turbine is both essential and complicated, which involves a proper evaluation of stress acting on the components and mechanical property of the chosen materials at low temperature. For metals under low temperatures, brittle fracture of the metal may occur prior to fatigue damage. A comprehensive consideration of low-temperature mechanical properties of materials and mechanical loads (due to hydrodynamic force and centrifugal force) acting on the components is of particular importance. Aluminum alloy 2031 is used for the turbine impeller and its mechanical properties under low temperatures are analyzed. To evaluate the stress acting on the components, numerical investigation using 3-D incompressible Navier-Stokes Equation together with k-epsilon turbulence model and mixing plane approach at rotator-stator interface are carried out at design and off-design flow with different nozzle-vane settings. The obtained pressure force is transformed into hydrodynamic load acting on the solid surface by means of fluid-solid interaction technology, and then used in the FEM (Finite Element Method) structure analysis together with the centrifugal force. Stress distribution of the component is obtained and deformation of the component analyzed. Evaluation of impeller strength is conducted for the cryogenic liquid turbine by combining the foregoing two aspects, and a use of alloy 2031 for the turbine expander is validated.

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