Papers by Keyword: Blade

Abstract: The integrity of coatings used on the surface of blades of gas turbines determines the reliability of the blades. Coatings life usually dictates blades refurbishment intervals. The failure investigation and life assessment of coatings are essential for the effective management of blades. In this paper, coatings failure mechanisms are investigated by examination of service-exposed blades, and a methodology of coatings life assessment is described.

Abstract: The influence of centrifugal prestress on the foreign object damage of engine blades was analyzed by numerical simulation. A nonlinear dynamic model for foreign object damage of blade with centrifugal prestress was established. And the dynamic relaxation method was used to obtain the initial stress and displacement field of blade in the beginning of the dynamic analysis of impact. Numerical simulations of foreign objects impacting on the leading edges of the blades under different centrifugal preloads were carried out. The results indicate that the local plastic deformation on the impact location of blade with centrifugal preload, which is produced at the moment of impact, is decreasing with the increase of the preload. The growth of crack produced on the lead edge of blade is accelerated with the preload increasing.

Abstract: The purpose of the study described in this paper was to investigate the impact of shroud curvature on the performance of a centrifugal impeller or stage. The paper discusses a computational fluid dynamics (CFD) study done to assess the influence of shroud curvature on impeller performance. The computational fluid dynamics (CFD) and finite element analyses (FEA) methods were used to describe the various designs of the impeller. Aerodynamic and mechanical analysis results are presented for four impellers of varying cover curvature and axial length. The aerodynamic results showed there were clear aerodynamic benefits to decreasing the curvature along the impeller shroud. The mechanical analytical results showed that the impeller with the lowest curvature or longest axial length provided the highest performance; it also yielded the lowest Von Mises stress level. In closing, there are clear aerodynamic benefits to decreasing the curvature along the impeller shroud but these benefits must be weighed against the impact on the rotordynamic considerations Comments are offered regarding the rotordynamic issues that must be considered when increasing the length of impellers.

Abstract: This paper made an analysis on the process of turbine blade, and completed the three-dimensional design of milling and cutting fixture used in the process on the UG software. After the stress analysis of the workpiece is completed, the author made a finite element analysis on both the blades and the main parts of the fixture with the help of ANSYS software, the results of the research provide theoretical basis for the development of reasonable processing technology and reliable workpiece assembly.

Abstract: In order to predict the microstructure evolution and grain size of GH4169 alloy blade in finish forging process and optimize the parameters, a coupled simulation between thermal mechanical and microstructure evolution was realized through embedding the developed user subroutines into the DEFORM-3D software. The temperature, equivalent strain, dynamic recrystallization fraction, average grain size and grain size distribution were predicted and discussed. The experimental results of microstructure under the same forging condition were investigated. The average grain degree in the blade rabbet and body are 8 and 10 respectively. The calculated results of microstructure have a good agreement with the measured value from experimental data and the prediction error of average grain size is less than 6.7%. The developed program is reliable and the accuracy is satisfying. The distribution of grain size along the blade body is decreased from the middle to the leading and back edge. The shape and microstructure after finish forging under the condition of technology parameters meet the user’s requirement. Keywords: Blade, GH4169 alloy, Numerical simulation, Microstructure, Forging

Abstract: In order to solve the problem of crack appeared in Francis turbine runner, the welding residual stress of Francis turbine runner is regulated and controlled by means of numerical simulation from the view of subsection welding, local heating and local peening. The results show that the length of welding section of blade outlet and the welding direction in the subsection welding process influence the residual stress of the turbine blade. For the local heating technology, the decreasing effect on residual stress increases with the increase of heating time, heating temperature and heating area. The welding residual stress of dangerous region decreases and then increases with the increase of heating distance. Moreover, the peening effect is very clear when the temperature of material in the peening region reaches its own plastic temperature.

Abstract: The flow field distribution in burnt lime hydrator has been investigated by a software FLUENT, with k-ε turbulence model and MRF method. The simulation result shows that when four blades deflect 30°, the whole velocity gradient of flow reduces and the recirculation zones also diminish; when the rotational speed is 75r/min, the turbulence kinetic energy of stir zone between two axes becomes larger, which can raise stirring effect and reduce fugitive dust, so it is easy to achieve the purpose of improving the environment of work condition.

Abstract: Blades are key components in aircraft engines, and flight safety is directly impacted by the repair quality of blades. Digital modeling for the surfaces of high pressure blades is conducted in this study based on the cloud data collected with scan. Boundary points of blades are obtained with the method of varied step lengths according to curvature, and then the envelope curves are plotted from the approximation of these boundary points with a third power B spline. 3-D digital models of blades in aero-engines are established with the envelope curves and the condensed data cloud. Results illustrate the smoothness and accuracy of the proposed engine blade repair model.

Abstract: RT（X-Radiography Testing） is a very import inspection method for detecting engine blade crack, and the defect is identified by person distinguishing the film for traditional RT. The traditional method is involved in high mistake and missed examining rate and low efficiency. It is great significance to blade integrity and flight safety that the crack can be quickly distinguished. In the paper, adopting a adaptive segmenting algorithm based on OTSU to quickly distinguish the crack on the blade image, and it can definite the threshold facing different gray image, and can reliably inspect the cracks which detection rate was 98%. The recognition accuracy for crack can reach 0.16mm Simulation result verify that the method is very effective on adaptively segmenting the blade image according to the threshold for crack inspection

Abstract: An orthogonal cutting model for investigating indentation type cutting of soft tissue was established, and the cutting force model was constructed theoretically based on fracture mechanics. A planar biological soft tissue cutting experimental setup was designed and developed to realize soft tissue cutting. Cutting experiments using orthogonal cutting blades were performed on fresh porcine liver at different cutting speeds. It was experimentally shown that the cutting speeds and the blade rake angles have significant effects on the penetration force and cutting force. Finally, a regression equation was obtained to explain the relationship among cutting force, cutting speed, and rake angle. These findings provide new insight into the biological soft tissue cutting.