⚡ electrical engineering

Configuration Design and Experimental Verification of Flow Field in Electrochemical Machining of Blisk Profiles

This paper presents the design, simulation, and experimental verification of four three-dimensional flow field configurations for electrochemical machining of blisk profiles, identifying an optimized model with a 12 mm additional electrolyte inlet that ensures stable machining and high surface quality.

Original authors: Jianwei Guo, Erhao Jiao, Long Chao, Yueqin Zhang

Published 2026-09-22

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CC BY 4.0

Original authors: Jianwei Guo, Erhao Jiao, Long Chao, Yueqin Zhang

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

In the heart of a modern jet engine lies a component that looks like a wheel of blades, yet it is carved from a single solid block of metal. This part, known as a blisk, combines the rotating disk and the air-moving blades into one seamless structure, making the engine lighter and more reliable. However, shaping these blades is a formidable challenge. They are twisted, made from superalloys that resist cutting, and packed so tightly that traditional tools cannot reach inside without breaking. To solve this, engineers turn to a process called electrochemical machining. Instead of a sharp blade grinding away metal, this method uses a stream of electrically charged liquid, called an electrolyte, to dissolve the metal atom by atom. The liquid must flow perfectly fast and evenly through the tiny gaps between the tool and the workpiece. If the flow slows down or stirs up bubbles, the delicate balance is broken, leading to a rough surface or even a short circuit that ruins the part.

A team of researchers set out to master this flow for the complex surfaces of blisk blades. They focused on the leading and trailing edges of the blades, the front and back curves where the liquid enters and exits the machining zone. Their goal was to design a system where the electrolyte could be fed into these edges from separate channels, giving them precise control over the pressure and speed of the liquid right where it was needed most. They built four different three-dimensional models of how this liquid could move, changing only the length of the inlet channels at the edges while keeping the width constant. Using powerful computer simulations, they watched how the liquid behaved in each design, looking for the one that created the smoothest, most consistent stream without any dead zones where the liquid might stall.

The simulations revealed a clear winner. When the inlet channels were six millimeters long, the liquid struggled to mix properly, creating large areas of slow movement near the base of the blade. This sluggish flow risked leaving behind the dissolved metal particles, which could cause sparks or damage the part. When the channels were made longer, at eighteen or twenty-five point six millimeters, the flow improved, but new problems emerged with sudden changes in speed. However, when the researchers tested a channel length of twelve millimeters, the results were different. The liquid moved with a steady, uniform speed throughout the entire blade, from the root to the tip. The computer models showed that this specific length eliminated the slow zones entirely, ensuring that the dissolved metal was swept away instantly and the electrical current remained stable.

To confirm that the computer models matched reality, the team built a physical experiment. They constructed a custom machine tool and fabricated small plugs to fit inside the inlet channels, allowing them to switch between the four different lengths during actual machining. They used a piece of superalloy shaped like a fan blade section and ran the electrochemical process with a twenty-volt current and a sodium nitrate solution. The results were striking. When they used the six-millimeter plugs, the finished blade surface was covered in visible streaks and marks, proof that the flow had been uneven. The longer plugs reduced these marks, but the twelve-millimeter configuration produced a surface that was completely free of flow lines. When they measured the roughness of this perfect surface, the numbers were remarkably low, indicating a finish that was smooth to the touch and ready for the high-stress environment of an engine.

Beyond the surface quality, the researchers also checked if the force of the flowing liquid would bend the thin metal tool used to shape the blade. In electrochemical machining, the tool is a delicate sheet of metal, and if the pressure from the liquid pushes it too hard, the shape of the blade will be distorted. The simulations showed that with the twelve-millimeter design, the tool bent by less than one-hundredth of a millimeter, a change so small it would have no effect on the final product. This confirmed that the design was not only effective at cleaning the surface but also gentle enough to protect the tool itself. By finding this specific balance in the channel length, the researchers demonstrated a way to make the flow of the dissolving liquid predictable and reliable, turning a difficult manufacturing process into a stable and precise operation.

Technical Summary: Configuration Design and Experimental Verification of Flow Field in Electrochemical Machining of Blisk Profiles

Problem Statement
Blisk (bladed disk) components are critical to aero-engine performance, yet their manufacturing faces significant challenges due to complex twisted geometries and the use of difficult-to-machine materials like nickel-based superalloys. Electrochemical machining (ECM) is a primary solution for blisk production due to its lack of tool wear and independence from material hardness. However, the stability of the electrolyte flow field is a decisive factor in ECM success. Non-uniform flow leads to stochastic fluctuations in electrical conductivity, the accumulation of electrolytic by-products, and flow anomalies such as starvation, vortex formation, and cavitation. These issues can result in catastrophic process failures, including short-circuiting and poor surface quality. Specifically, the narrow cascade channels of blisks and the pressure differentials across thin-sheet cathodes necessitate a flow field design that ensures uniform velocity and timely removal of by-products, particularly at the leading and trailing edges where flow interactions are complex.

Methodology
This study addresses the flow field optimization for the finish machining stage of blisk profiles using a combined approach of finite element simulation and experimental verification.

Model Establishment: Four three-dimensional flow field configurations were designed. All configurations utilized auxiliary electrolyte supply structures at the leading and trailing edges of the blade blank, in addition to standard inlets at the blade roots of the suction and pressure sides. The key variable was the cross-sectional length ( $L$ ) of the leading and trailing edge inlets, with four levels tested: 6 mm, 12 mm, 18 mm, and 25.6 mm (width fixed at 3 mm).
Simulation Analysis: The RNG $k-\varepsilon$ two-equation turbulent flow model was employed to simulate the incompressible, turbulent electrolyte flow within the inter-electrode gap. Boundary conditions included specific pressure inputs (1.0 MPa for root inlets, 0.6 MPa for leading/trailing edge inlets, and 0.15 MPa for the outlet). The simulations analyzed velocity distributions at three cross-sections (root, mid-span, and tip) and evaluated cathode deformation under hydraulic pressure.
Experimental Verification: Comparative experiments were conducted on a six-axis four-linkage ECM machine tool using GH4169 superalloy workpieces and a 20% sodium nitrate electrolyte. Configuration plugs were fabricated to physically realize the four inlet length variations. Surface roughness was measured using a profilometer, and metallographic analysis was performed to check for intergranular corrosion.

Key Contributions

Design of Auxiliary Inlet Configurations: The paper proposes and evaluates a specific design strategy involving independent electrolyte supply at the leading and trailing edges to actively control flow parameters in these critical zones.
Quantitative Flow Field Optimization: By varying the inlet length ( $L$ ), the study identifies the specific geometric parameter that minimizes low-velocity regions and variance in flow velocity.
Coupled Deformation Analysis: The study integrates flow field simulation with cathode deformation analysis, demonstrating that the optimal flow configuration also minimizes tool deformation, thereby preserving machining accuracy.
Experimental Validation: The research provides empirical evidence linking specific flow field parameters to surface finish quality and process stability, confirming the simulation predictions.

Results

Flow Velocity and Uniformity: Simulation results indicated that the configuration with $L = 6$ mm suffered from large low-velocity areas and high variance ( $\sigma^2 = 107.20$ m $^2$ /s $^2$ ), leading to potential flow starvation. The configuration with $L = 12$ mm achieved the optimal performance, characterized by a mean velocity of 19.28 m/s, a variance of 61.36 m $^2$ /s $^2$ , and a 0% percentage of low-velocity points ( $p_p$ ). Configurations with $L = 18$ mm and $L = 25.6$ mm showed improved flow over the 6 mm case but were inferior to the 12 mm case in terms of uniformity.
Cathode Deformation: Under the optimal $L = 12$ mm configuration, the maximum cathode deformation was calculated to be 0.0084 mm, a negligible amount that ensures high machining accuracy compared to other configurations.
Surface Quality: Experimental results aligned with simulations. The $L = 6$ mm configuration produced visible flow marks on the blade surface. The $L = 12$ mm configuration yielded a surface free of flow marks, with surface roughness values of $R_a = 0.397$ $\mu$ m for the blade back and $R_a = 0.404$ $\mu$ m for the blade basin.
Surface Integrity: Metallographic examination revealed no intergranular corrosion or microcracks in the machined regions, confirming favorable surface integrity.

Significance
The paper claims that the proposed flow field configuration design method is reasonable and effective for the electrochemical machining of blisk profiles. By optimizing the cross-sectional length of the leading and trailing edge inlets to 12 mm, the study demonstrates a significant improvement in flow field stability and uniformity. This optimization directly translates to a stable machining process and the achievement of high surface quality without tool wear or surface defects. The work validates that active control of electrolyte supply at critical blade edges is a viable strategy for overcoming the manufacturing challenges associated with complex blisk geometries.

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