Abstract
The process analysis of manufacturing the castings of turbine moving blades demonstrated that approximately 5% of the blade blanks from a lot are rejected to a considerable geometric distortion of the blade airfoil. The turbine moving blade casting manufactured by the casting method with directed crystallizing may differ in its geometric and dimensional-accuracy parameters from the design model. The casting geometry varies as a result of high temperature and structural shrinkage deformations which are manifested as the hindered volumetric shrinkage and contraction during crystallizing and upon the casting knockout from the ceramic mould. High-temperature deformations may result in contraction of the casting mould and ceramic core shaping the inner blade cooling channels. As a result, to obtain the blade of the geometric form as set by the designer, it becomes necessary to predict the stress-deformed state of the moving blade casting in order to consider the volumetric shrinkage and deformation in advance. Therefore, predicting and considering the total volumetric shrinkage during the manufacture of the moving blade castings ensuring the minimum contraction of the process system “ceramic mould – casting – ceramic core” is a relevant problem for the modern blank production.
Highlights
Improving the service life and reliability of gas turbine engines and units is presently conditioned by the necessity to increase the working temperature at the turbine inlet at simultaneous additional dynamic and vibration loads. This refers to the turbine blades which operate under the strength load and corrosion failure conditions during the interaction with aggressive gas flows for a long period of time
The initial casting geometry is designated in grey, the casting after shrinkage is shown in red
The computer simulation results demonstrate that the shrinkage is commonly nonuniform, the following behaviour is revealed – the turbine moving blade casting may conditionally be divided into three areas, each of which is characterized by the uniform change of geometry during the thermal shrinkage [12]
Summary
Improving the service life and reliability of gas turbine engines and units is presently conditioned by the necessity to increase the working temperature at the turbine inlet at simultaneous additional dynamic and vibration loads. First of all, this refers to the turbine blades which operate under the strength load and corrosion failure conditions during the interaction with aggressive gas flows for a long period of time. The main efforts should be aimed, among others, to improving the production technologies for the manufacture of the main engine parts such as blades [1,2,3,4].
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