Design and grindability assessment with cup shaped electroplated CBN wheel grinding turbine disc slots of powder metallurgy superalloy FGH96

The machining surface integrity of aero-engine turbine disc slots has a significant impact on their fatigue life and service performance,and achieving efficiency and high-precision machining is still a great challenge.The high machining requirements of future aeroengine turbine disc slots will be difficult to satisfy using the broaching method.In addition,existing methods of slot machin-ing face difficulties in ensuring surface integrity.This study explored a cup shaped electroplated Cubic Boron Nitride(CBN)abrasive wheel for profile grinding the turbine disc slots of FGH96 powder metallurgy superalloy.The matrix structure of the cup shaped abrasive wheel was designed and verified.A profile grinding experiment was conducted for fir-tree slots on a five-axis machining center.The accuracy and the surface integrity were analyzed.Results show that the key dimension detection results of the slots were within the allowable tolerance range.Meanwhile,an average sur-face roughness Ra of 0.55μm was achieved,the residual stress was compressive,the plastic defor-mation layer thickness was less than 5μm,and the hardening layer thickness was less than 20μm.The research findings provide a new approach to machining the slots of aviation engine turbine discs and guidance for the high-quality processing of complex components.

Stress and deformation of rocket gas turbine disc under different loads using finite element modelling

Gas turbine discs have numerous applications in the aerospace industry,such as in liquid rocket engines.In this study,the stresses and deformations of a turbine disc were studied.The goal was to highlight the stress and deformation distribution to assist in the design of a disc as well as to demonstrate the importance of using finite element(FE)analysis in simulating an actual design case.Then,to present the real model,a twodimensional(2D)axisymmetric model for a non-uniform disc was analysed using FE analysis.The stresses and deformations developed as a result of the disc operating conditions at high rotational speeds and thermal gradients were evaluated using two types of heat transfer modes-conduction and convection,taking into consideration the material behaviour at elevated temperatures.The FE model revealed that the weight of the disc should be reduced optimally by using a non-uniform thickness because this results in a huge increase in the applied stresses.The greatest stresses in the disc result from the thermal load caused by conduction,and they are located at the centre of the disc.In addition,an analytical method was used to evaluate and predict the stresses along the disc,and it gave a good estimate of the stress values compared to the FE model.Based on this estimate,a parametric study was conducted for a range of rotational velocities under high temperature loads for a series of disc radii.Finally,it was found that this method can be used for the preliminary design of different turbines.

Effects of the Blade Shape on the Trailing Vortices in Liquid Flow Generated by Disc Turbines

Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their rela-tionship with turbulence properties in a stirred tank of 0.48 m diameter,agitated by four different disc turbines,in-cluding Rushton turbine,concaved blade disk turbine,half elliptical blade disk turbine,and parabolic blade disk turbine.Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail.The location,size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics.The larger curvature resulted in longer residence time of the vortex at the impeller tip,bigger distance between the upper and lower vortices and longer vortex life,also leads to smaller and stronger vortices.In addition,the turbulent ki-netic energy and turbulent energy dissipation in the discharge flow were determined and discussed.High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them.Although restricted to single phase flow,the presented results are essential for reliable de-sign and scale-up of stirred tank with disc turbines.