Effects of Guiding Angle on Plastic Metal Flow and Defects in Extrusion of Aluminum Alloy

To reduce defects, such as the shrinkage cavity and the surface cracks caused by non-homogeneous metal flow in extrusion process, an extrusion method was proposed by using a die with the guiding angle. Numerical simulation and experiment were conducted to investigate the metal flow in this extrusion process. It is shown that the stress state at the bottom of the die is changed. The tendency to generate the dead zone is decreased by employing the guiding angle at the die entrance. The shrinkage cavity is reduced because the non-homogeneous metal flow at the final stage of extrusion is improved. The axial stress is decreased greatly so that the surface cracks caused by additional stress are avoided.

Optimum Tilt Angle of Flow Guide in Steam Turbine Exhaust Hood Considering the Effect of Last Stage Flow Field

Abstract Heat transfer and vacuum in condenser are influenced by the aerodynamic performance of steam tur- bine exhaust hood. The current research on exhaust hood is mainly focused on analyzing flow loss and optimal design of its structure without consideration of the wet steam condensing flow and the exhaust hood coupled with the front and rear parts. To better understand the aerodynamic performance influenced by the tilt angle of flow guide inside a diffuser, taking a 600 MW steam turbine as an example, a numerical simulator CFX is adopted to solve compressible three-dimensional （3D） Reynolds time-aver- aged N-S equations and standard k-e turbulence model. And the exhaust hood flow field influenced by different tilt angles of flow guide is investigated with consideration of the wet steam condensing flow and the exhaust hood coupled with the last stage blades and the condenser throat. The result shows that the total pressure loss coefficient and the static pressure recovery coefficient of exhaust hood change regularly and monotonously with the gradual increase of tilt angle of flow guide. When the tilt angle of flow guide is within the range of 30~ to 40~, the static pressure recovery coefficient is in the range of 15.27% to 17.03% and the total pressure loss coefficient drops to approximately 51%, the aerodynamic performance of exhaust hood is significantly improved. And the effectiveenthalpy drop in steam turbine increases by 0.228% to 0.274%. It is feasible to obtain a reasonable title angle of flow guide by the method of coupling the last stage and the condenser throat to exhaust hood in combination of the wet steam model, which provides a practical guidance to flow guide transformation and optimal design in exhaust hood.

Effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump

To study the effect of guide vane outlet angle on pump performance and impeller radial force in an axial-flow heart pump, guide vane outlet angle/34 is considered to be 20°, 15°, 10°, 5° and 3° respectively. Based on ANSYS Fluent, numerical results of pump head and efficiency are validated by exper/ment results, in which Xanthan gum solutions are used with concentration of 0.06 wt. % as working fluid. Then, the effects of/34 on pump performance and impeller radial force are discussed, the errors of head and efficiency between test and simulation are within 5%. The results a/so indicate that the pump performance and efficiency are much better than those of other angles when guide vane outlet angle/34 is 10°, and the maximum variations in head and efficiency are 1.9% and 2.2%, respectively. With/34 increasing, the pulsation of radial force decreases firstly and then increases, when/34 is 10°, the minimum pulsation is 0. 0392N, which is about 80% of the maximum pulsation amplitude.