No abstract

A variety of quenching, cryogenic and tempering treatments were conducted to assess the effect of cryogenic treatment on the thermal stability of retained austenite (RA) during tempering processes in highcarbon steel. Optical and electron scanning microscopes, transmission electron microscopy coupled with X-ray diffractions were employed to determine the morphology, fraction and carbon concentration of RA. It is confirmed that pre-cryogenic treatment is crucial which strongly affects the carbon concentration and dislocation density in RA and thus consequently the stability of RA. However, the carbon concentration is the most dominant one especially in relatively higher temperature tempering processes.

No abstract

Centrifugal pumps as turbine (PAT) are widely used in petrochemical and water conservancy industries. The research on the internal flow field and energy loss of PAT is of great significance to improve the performance and efficiency of PAT. In this paper, experimental and numerical simulation methods are used to study the energy loss and flow field. The results show that the numerical simulation method can accurately simulate the internal flow field of PAT. And the entropy generation theory is applied to visualize the internal energy loss of PAT through the comparison of total pressure loss and entropy generation. The highest energy loss among PAT components is the guide vane. The loss in the guide vane is mainly caused by the flow separation caused by the wake of the guide vane and the asymmetric structure of the volute. The losses in the impeller are mainly due to flow separation and wake. Besides, the unsteady simulation results show that rotor-stator interaction has a great influence on the gap between the impeller and the guide vane. The research results provide a reference for the design of the PAT. This study is beneficial to studying the dynamic and static interference and PAT vibration to improve the stability of the PAT.