Flow field characteristics analysis of interelectrode gap in electrochemical machining of film cooling holes
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ORIGINAL ARTICLE
Flow field characteristics analysis of interelectrode gap in electrochemical machining of film cooling holes Mingxia Chai 1 & Zhiyong Li 1 & Hongjuan Yan 1 & Zhaoxia Huang 1 Received: 9 April 2020 / Accepted: 19 October 2020 # Springer-Verlag London Ltd., part of Springer Nature 2020
Abstract Electrochemical machining (ECM) is an important method to drill film cooling holes in difficult-to-machine materials such as high-temperature nickel-based alloy. However, physical field parameters of ECM, such as flow field characteristics and temperature field distribution in the interelectrode gap, cannot be directly monitored, which makes it difficult to improve the accuracy of ECM. In this paper, the effect of processing voltage, electrolyte inlet pressure, and electrode feed rate on machining accuracy was studied through experiments. According to the gas–liquid two-phase flow theory and mathematical model of convective heat transfer, the volume fraction of hydrogen and electrolyte temperature field were simulated and analyzed by COMSOL Multiphysics software. The results indicate that the electrolyte temperature plays a dominant role in all factors affecting the processing effects when only the processing voltage or electrolyte inlet pressure changes. When only the electrode feed rate changes, volume fraction of hydrogen dominates the effects. This has guiding significance for practical production, and can improve the accuracy of ECM by controlling the temperature of the electrolyte and the volume fraction of hydrogen. Keywords Film cooling hole . Electrochemical machining (ECM) . Volume fraction of hydrogen . Temperature filed . Side gap
1 Introduction Inconel 718 is a novel material introduced in the field of hard-to-machine materials. Due to its high strength to weight ratio and the ability to withstand tremendous environmental conditions, it is used in the aeronautical and aerospace industry, such as in turbine blades [1]. Nevertheless, high hardness and low thermal conductivity of the alloy pose difficulties while employing conventional machining and forming processes [2]. Electrical discharge machining (EDM) and * Zhiyong Li [email protected] Mingxia Chai [email protected] Hongjuan Yan [email protected] Zhaoxia Huang [email protected] 1
School of Mechanical Engineering, Shandong University of Technology, Zi’bo 255049, China
laser beam machining (LBM) are thermal processes, which leads to recast layer, heat-affected zone, and tensile residual stresses. Electrochemical machining (ECM) has become one of the main processing technologies for machining cooling holes in turbine blades due to its advantages without thermal damage [3, 4]. The influence of cooling hole ECM mode and process parameters on its machining accuracy and efficiency has been a research hotspot in this field. EDM/ECM in situ combined process improves the surface produced by EDM [5]; the shaped tube electrolytic drilling can realize drilling contoured holes in difficult-to-machine materials [6]. Chen et al. [7] conducted orthogon
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