Electrolyte Flow Rate Research Articles

High-Capacity Bio-Inspired Redox Flow Batteries with Insoluble Redox Boosters

Redox flow batteries (RFBs) are considered to be one of the key technologies for addressing the intermittency problem in renewable energy sources, due to their unique architecture that allows for unprecedented scalability and flexibility, and cost-effectiveness in long-duration storage [1]. Despite their promise, typical RFBs suffer from low energy density because of the limit imposed by the solubility of the redox active species in the electrolyte [2]. One promising approach to bypass the solubility limitation and drastically improve the energy density is the addition of insoluble charge storage materials into the electrolyte tanks. These redox active materials are reversibly oxidized/reduced in the tanks upon interaction with the redox active species dissolved in the electrolyte. Thus, the capacity is no longer dependent on the concentration of soluble species but rather the quantity of solids in the tanks [3-4]. This new concept is called redox-mediated flow battery (RMFB).In this presentation, we demonstrate a high energy density RMFB using a highly stable bio-inspired active material (vanadium(IV/V)bis-hydroxyiminodiacetate (VBH)) and a suitable solid storage material. VBH, as a high-stability active material [5], provides an ideal scaffold to investigate the complex electrochemical processes that occur during RMFB operation, which remain virtually unexplored [6]. For the solid storage material, a Prussian Blue Analogue (PBA) is synthesized and coupled with VBH mediators. Symmetric cell cycling experiments are performed with and without the solid energy booster material to provide evidence that the addition of a compatible solid material greatly improves the energy density. Compatibility between the PBA and VBH is investigated using cyclic voltammetry (CV) experiments. Optimization of the critical parameters such as the amount of solid storage material, the operating current density, and the electrolyte flow rate is presented.

Characterization of Interfacial Properties in Electrochemical Nitrate Reduction to Optimize Ammonia Production

Nitrate pollution of wastewater from agricultural runoff and industrial waste streams is common around the globe. Nitrate negatively impacts the environment through harmful algal blooms and can be dangerous for human consumption. Rather than treat nitrate as a waste, we electrochemically reduce nitrate (NO3RR) to ammonia (NO3 - + 9H+ + 8e- → NH3 + 3H2O), a commonly used fertilizer and clean fuel. Electrochemical treatment can enable on-site, modular treatment powered by renewable energy. As an inner-sphere reaction involving multiple hydrogenation and electron-transfer steps, the activity and selectivity of electrochemical NO3RR to NH3 are strongly influenced by properties at the electrode–electrolyte interface. When potential is applied, the electric double layer (EDL) forms that comprises ordered molecular layers extending up to 10 Å from the surface. This EDL is the primary environment where the heterogeneous NO3RR occurs and can impact the reaction in several ways, including blocking catalytic sites and stabilizing reactants and reaction intermediates. To understand the molecular mechanisms of these impacts, the EDL structure is studied with x-ray reflectivity (XRR), which provides atomic-level resolution of the near-surface electron density profile and reveals the number of ordered layers, the distance of each layer from the surface, the ion surface coverage, and the degree of hydration of ions in each layer. We complement these investigations with operando attenuated total reflectance–surface-enhanced infrared absorption spectroscopy (ATR–SEIRAS) under similar reaction conditions to investigate the adsorbed reactants, intermediates, and local pH. Furthermore, composition and structure of the EDL can change with varying bulk electrolyte compositions and mass transport regimes, which also provide levers to control reaction activity and selectivity. We use a continuum model (generalized modified Poisson–Nernst–Planck, GMPNP) to develop the spatial profiles of the electric field, reactant nitrate concentration, cation concentrations, and pH outside the EDL and how they change as functions of applied potential, bulk electrolyte composition, and flow rate. Taken together, our results relate 1) bulk electrolyte properties with interfacial EDL properties and 2) interfacial properties with reaction activity and selectivity, informing the choice of operating parameters such as electrolyte composition and flow rate to optimize ammonia production in electrochemical NO3RR.

(Invited) Optimized Operation of the Vanadium Redox Flow Batteries

The Redox Flow Battery (RFB) systems are unique chemically, mechanically, and electrically compared to other kinds of batteries. Among RFBs, the Vanadium Redox Flow Batteries (VRFBs) are the most commercialized type. VRFBs are a suitable option for large-scale energy storage with exceptional advantages like the decoupled power and energy design (scalability), long life-time, safe battery chemistry (non-toxic, and non-flammable), etc. The power and energy designs in VRFBs are decoupled, known as the scalability benefit of the VRFBs. This implies more output energy from the battery is possible only by adding more electrolytes to the reservoir tanks.There are only a few research studies in the literature about the optimized operation of the Vanadium redox flow batteries. Most of these papers are not applicable to develop in real practice. The introduced optimized operation algorithms of VRFBs in this lecture can help the participants learn how to improve the performance of the battery and operate the battery more efficiently. Different objective functions are considered in this lecture to be optimized, e.g. minimizing the time duration of battery charging (for fast charging), energy loss, voltage loss, and capacity loss of the battery. The participants can find the results of this useful in optimized operation and implementation of the VRFBs.High charging current density results in faster charging and reduces the capacity fading in Vanadium Redox Flow Batteries (VRFB). On the other hand, it leads to the reduced energy efficiency of the battery. Also, the lower electrolyte flow rate in VRFBs results in less energy consumption by the pumps leading to the higher energy efficiency of the VRFBs. However, higher flow rates have the benefit of reducing voltage loss of VRFBs. To address these trade-offs, closed-loop charge control and flow management in VRFBs are necessary. In this lecture, a multi-objective optimization is proposed in first section to optimize the charging duration and flow management of the VRFB simultaneously during its charging. An innovative method is proposed for modeling pump consumption based on affinity laws for centrifugal pumps, which leads to new electrolyte flow management. Further, three case studies are defined in charging mode on a nine-cell VRFB unit laboratory prototype to validate the proposed optimization's performance, involving the duration of charging, flow management, and energy efficiency of the VRFB. The method is compared with previously published research studies on the optimal operation of VRFBs, which shows the uniqueness and consistency of the proposed optimization method for simultaneous controlling VRFB's charging duration and flow management.Capacity fade in Vanadium Redox Flow Batteries (VRFB) relies on the loss of electrolyte volume in each of charge and discharge cycles. The loss of volume in each cycle, also known as the bulk electrolyte osmosis, is due to Vanadium ions' diffusion from the membrane. The lower electrolyte flow rate in VRFB can reduce capacity fade as the electrolyte's velocity across the membrane decreases. However, the lower electrolyte flow increases the battery’s voltage loss. A new electrolyte flow management is introduced in second section of the lecture to address this trade-off, which considers the decrease of both capacity fade and voltage loss in VRFBs simultaneously. The proposed multi-objective flow management shows a significant reduction of both capacity and voltage losses in VRFBs.Moreover, typically complex electrochemical models and equations are needed to model capacity fade in VRFBs, which are not straightforward to model. The capacity fade modeling can lead to the estimation of available capacity and the battery’s State of Health (SoH). Therefore, a new mathematical model is proposed for the VRFB’s available capacity based on the electrochemical-based capacity fade model results. The model further is developed to estimate the State of Charge (SoC) and the SoH of VRFBs per cycle of charge and discharge.

The configuration optimized design method based on real-time efficiency for the application of vanadium redox flow battery in microgrid

To realize the efficient, economical and stable operation of vanadium redox flow battery (VRB) in a microgrid containing a high proportion of renewable energy, a coupling calculation model is constructed and a configuration optimized design method is proposed in this paper. First, the coupling calculation model involving the fluid mechanics model and electrochemistry model is established to obtain the real-time efficiency of VRB. Second, an economic model of VRB is constructed considering the investment costs, operation costs, economic benefits and renewable energy utilization. Finally, a configuration optimized design method based on typical load and real-time efficiency is further proposed to cope with practical application scenarios. Two different objectives, including the lowest average daily cost and the lowest renewable energy curtailment, are selected in the method. The results are presented as follows. First, the energy efficiency of the battery is increased from 76.90% to 80.45% with the increase of electrolyte flow rate. With the optimal selection of porous electrode porosity, the merit energy efficiency and system efficiency are presented. Better VRB performance can be obtained at the electrolyte flow rate of 120 ml/min and the porous electrode porosity of 0.93. Second, the novel proposed configuration design method can be implied to improve the renewable energy consumption capacity while ensuring system economics. Finally, with the lowest average daily cost as the objective, the optimal configuration of VRB is 891 kW and 7344 kWh, respectively, while the time average efficiency is 79.26%. The total amounts of renewable energy curtailment in one day decreases from 12,380 kWh to 6,281 kWh. At the same time, the power supply quality is significantly improved after accessing various distributed energy sources to the microgrid.

Prospect of modeling industrial scale flow batteries – From experimental data to accurate overpotential identification

A vast literature exists on modelling of small-scale single-cell experiments for flow batteries, but very few reports have been published on large stacks, consisting of tens of cells, each with an active area of hundred square centimeters. In this report, a large set of measurements taken on a kW-class vanadium test facility is used to develop an accurate ad-hoc physical model. Experimental data consist of polarization curves at a broad range of states of charge and electrolyte flow rates, as well as electrochemical impedance spectra. The model is capable to decouple three sources of voltage losses: activation, ohmic, and concentration overpotentials. In addition, a new numerical approach for identifying the main parameters of electrochemical kinetics and mass-transport has been proposed. To the best of our knowledge, this is the first time when a model for voltage losses analyses was developed and fitted to a data from large-scale flow battery, being validated with a sensitivity analysis study. Investigations showed that activation losses have a sophisticated nature in combination with mass-transport limitations and play an important role in a wide range of loading current densities. As a result, they must be included in a reliable model able to reflect a non-linear voltage behavior of large stacks. This work also highlights that, in the investigated case, activation losses are likely to be attributed to the positive electrode rather than to the negative one. The obtained results could facilitate the development of advanced simulation and design of large-scale flow battery stacks.

Mass Transfer Coefficient Enhancement Using Spiral Wound Rod as Turbulence P romoter in an Electrolytic Cell

Objectives: to improve efficiency of process equipment by increasing the mass transfer coefficient with a spirally wound rod as the turbulence promoter. Methods:The function of facet promoters, whirl generators, and test sections of different congruous shapes increase the mass transfer coefficients at the reaction surface. Diffusion-controlled redox (ferricyanide - ferrocyanide) reaction has been chosen for the study. Limiting current data from the reduction of ferricyanide is used for mass transfer coefficient calculation. A set of three geometric parameters such as pitch(P), height(H), and width(W) of the promoter were investigated in the current study. Findings: An increase in the mass transfer coefficient values with the increment of flow rate of electrolyte from 0.088 m/s to 0.263 m/s was observed. A rise in the promoter height from 0.03 to 0.07m enhanced the mass transfer coefficient by 25.7 fold, while the increase in the width of the promoter from 0.01 to 0.04m resulted in a rise of the mass transfer coefficient by 26.3 fold. On the contrary, the mass transfer coefficient decreased upon increase in the pitch of the promoter from 0.01 to 0.04m, but overall enhancement is 25.7 fold. The increase in the mass transfer coefficient on an average compared to a rectangular turbulence promoter was 5.71 fold. Novelty: The spiral wound rod as a promoter increased the mass transfer coefficient several folds compared to other promoters. The spiral wound rod is quite simple to manufacture, has low cost and ease of maintenance. Therefore, the promoter used in the study could be employed for heat and/or mass transfer enhancement in Industrial applications. Keywords: Limiting current; Promoter; Mass transfer Coefficient; Swirl flow; Redox reaction

Simulation Analysis of Multi-Physical Field Coupling and Parameter Optimization of ECM Miniature Bearing Outer Ring Based on the Gas-Liquid Two-Phase Turbulent Flow Model.

Electrochemical machining (ECM) is an essential method for machining miniature bearing outer rings on the high-temperature-resistant nickel-based alloy GH4169. However, the influence of electrolyte temperature distribution and bubble rate distribution on electrolyte conductivity in the ECM area could not be fully considered, resulting in the simulation model not being able to accurately predict the machining accuracy of the outer ring of the miniature bearing, making it challenging to model and predict the optimal process parameters. In this paper, a multiphysics field coupled simulation model of electric, flow, and temperature fields during the ECM of the miniature bearing outer ring is established based on the gas–liquid two-phase turbulent flow model. The simulation analyzed the distribution of electrolyte temperature, bubble rate, flow rate, and current density in the machining area, and the profile change of the outer ring of the miniature bearing during the machining process. The analysis of variance and significance of machining voltage, electrolyte concentration, electrolyte inlet flow rate, and interaction on the mean error of the ECM miniature bearing outer rings was derived from the central composite design. The regression equation between the average error and the process parameters was established, and the optimal combination of process parameters for the average error was predicted, i.e., the minimum value of 0.014 mm could be achieved under the conditions of a machining voltage of 16.20 V, an electrolyte concentration of 9.29%, and an electrolyte inlet flow rate of 11.84 m/s. This is important to improve the machining accuracy of the outer ring of the ECM miniature bearing.

Electrolyte flow rate control for vanadium redox flow batteries using the linear parameter varying framework

In this article, an electrolyte flow rate control approach is developed for an all-vanadium redox flow battery (VRB) system based on the linear parameter varying (LPV) framework. The electrolyte flow rate is regulated to provide a trade-off between stack voltage efficiency and pumping energy losses, so as to achieve an energy efficient battery operation. The nonlinear process model is embedded in a linear parameter varying state–space description and a set of state feedback controllers are designed to handle fluctuations in current during both charging and discharging. Simulation studies have been conducted under different operating conditions to demonstrate the performance of the proposed approach. This control approach was further implemented on a laboratory scale VRB system.

Properties of Electric Discharge of a Jet Anode and an Electrolytic Cathode

The paper shows some results of the definite current-voltage characteristic (CVC) of interaction of electric discharge with a jet electrolytic cathode and a steady anode at different jet lengths (lc), jet diameter (dc), electrolyte flow rate (G) for various electrolyte concentrations.

Study on the effect of electrode configuration on the performance of a hydrogen/vanadium redox flow battery

All-vanadium redox flow batteries (VRFBs) are one of the potential energy storage systems for renewable energy storage. The high cost of vanadium electrolytes is one of the barriers to VRFB commercialization. To reduce the cost of the battery, the aqueous negative electrolyte is replaced with gaseous hydrogen, whereas the positive electrolyte retains vanadium ions as a hydrogen–vanadium redox flow battery (HVRFB). Hydrogen can be supplied using renewable energy sources, which enhances the kinetics of the reaction. The HVRFB is investigated in this study by examining the effects of negative electrode configuration, Pt loading, humidity conditions, and electrolyte flow rate. Pt loading and positive electrolyte flow rate are discovered to have a significant effect on electrolyte utilization. The highest battery performance is obtained when the catalyst loading is set at 0.3 mg Pt cm−2 and the positive electrolyte flow rate is around 2 L h−1. The HVRFB operates continuously for 200 cycles and demonstrates an energy efficiency of around 88% when operated at a current density of 80 mA cm−2.

Effect of pore size and electrolyte flow rate on the bubble removal efficiency of 3D pure Ni foam electrodes during alkaline water electrolysis

To further reduce the capital expenditure of alkaline water electrolyzers, an improvement in power density can still be achieved through process intensification. The change from traditional gap-cells to zero-gap cells has already been proven to be very promising in this respect. In the zero-gap design, macro-porous 3D structures are typically being used as electrodes. Here, pure nickel foams with different pore sizes in the range 450 – 3000 µm have been studied under well-controlled electrolyte flow conditions. To this end, a dedicated flow cell has first been constructed that allows for imposing the same relatively high flow rates on the order of 1 L/min that are typically encountered under industrial conditions. Our specific cell design was shown by computational fluid dynamic simulations to be able to homogenize the flow field before entering the electrodes. This is absolutely mandatory to reliably evaluate the intrinsic bubble removal efficiency of the differently sized foams. We then demonstrate that the effect of pore size and the electrochemical performance can be rationalized by considering the cell voltage as a function of electrochemical current density, i.e. the current divided by the theoretically available electrochemical surface area (ECSA) rather than by the projected electrode area. Based on this analysis, we were also able to quantify the bubble removal efficiency by estimating the effective fraction of the ECSA that is not impeded by bubble coverage.

A hybrid system for lead removal of simulated battery industry Wastewater using electrocoagulation/electroflotation

ABSTRACT This study is on removing toxic lead ions pollutants from battery industry wastewater by utilizing a hybrid electrocoagulation/electroflotation (EC/EF) system with a continuous bipolar reactor. Simulated wastewater with a Pb initial concentration of 100 mg/L is used in all key experiments. The objective of this study is to investigate the lead removal efficiency with various independent parameters, such as solution pH (3, 7, 9), applied current density (5, 7.5, 10) mA/cm2, and electrolyte flow rate (0.0166, 0.025, 0.05) l/min at a cell voltage of 6 V and operating period (10–60) minutes. At a current density of 5 mA/cm2 and a flow rate of 0.166 liters per minute, It was able to remove 99.5% of Lead from wastewater at pH 9.0 for 60 minutes. According to the results of this research, the reactor can be employed to effectively remove lead ions from wastewater of the battery industry.

Simulation Analysis and Process Evaluation of Cooling Hole Forming Precision in Mask Assisted Electrochemical Machining Based on GH4169.

Good heat dissipation performance of aero-engine an effectively improve the service performance and service life of aero-engine. Therefore, this paper studies the machining method of cooling holes of high-temperature existent material GH 4169 for aero-engine innovatively puts forward the mask electrochemical machining method of cooling holes and explores the entrance morphology and taper formation law of the hole structure of high-temperature resistant material GH 4169. The mathematical model of anode dissolution of cooling holes in ECM is established, and the influence of voltage and electrolyte flow rate on cooling holes in ECM is analyzed. Compared with the mask-less electrochemical machining, the inlet radius of cooling holes in mask electrochemical machining is reduced by about 16.0% and the taper is reduced by 52.8% under the same machining parameters, which indicates that the electrochemical machining efficiency of mask is higher and the machining accuracy is better. Experiments show that the diameter of the mask structure improves the accuracy of the inlet profile of the cooling hole in the ECM. The diameter of the mask increases from 2 mm to 2.8 mm, and the inlet radius of the cooling hole increased from 1.257 mm to 1.451 mm When the diameter of the mask is 2.2 mm, the taper of the cooling hole decreased by 53.4%. The improvement effect is best, and the thickness of the mask has little influence on the forming accuracy of the cooling hole.

Experiment and Modelling of Triangular Holes Array by Non-traditional Machining Process

Triangular holes array is a common structure of the specially shaped holes that can be used for various products in aerospace vehicles. These are commonly produced in the electrochemical machining (ECM) process. The high-quality and accuracy of a triangular grid are closely related to the processing parameters of cathode structure and sidewall insulation sleeve, power supply, electrolyte flow rate, feed speed, and machining gap. Simulations have been carried out to consider the influence of parameters including structure and dimension of the cathode, initial machining gap, feed speed, and current on the homogeneity of the flow field in the machining gap. Consequently, the modeling can support the design of the cathode. The paper is divided into two parts. Firstly, the tool cathode is simulated and fabricated. Secondly, the triangular holes array is produced by using the designed cathode tool. It was found that higher feed speed and lower machining gap increase the stability, accuracy, and efficiency of the machining process and the quality of the triangular holes array.

Study on the effect of hydrogen evolution reaction in the zinc-nickel single flow battery

Considering the conservation laws of mass, momentum, and charge, and further coupling the global reaction kinetics equation and bubble kinetics equation, a two-dimensional transient two-phase flow model of zinc-nickel single flow battery considering hydrogen evolution parasitic reaction is established, which is used to investigate the influence of bubble flow formed by hydrogen bubbles and electrolyte on the battery performance. The accuracy of the model is verified by experimental data, and then the changes of hydrogen volume fraction, hydrogen evolution reaction current density, and negative electrode main reaction current density in the battery with time and space are investigated. Based on further analyzing the influence mechanism of bubble flow on ion transfer at the negative electrode interface, the effects of electrolyte flow rate, applied current density, hydroxide ion concentration, and bubble diameter on hydrogen volume fraction and polarization loss are also studied. The results show that the extra disturbance caused by bubble flow can effectively promote the ion transfer at the negative electrode interface and reduce the concentration polarization and activation polarization loss; On the other hand, it also causes the uneven distribution of ion concentration at the negative electrode interface, which leads to the uneven distribution of current density of hydrogen evolution reaction and negative electrode main reaction at the negative electrode interface. In addition, decreasing electrolyte flow rate, increasing applied current density, increasing hydroxide ion concentration, and increasing bubble diameter can enhance the disturbance effect of bubble flow. For the zinc-nickel single flow battery, this work provides a mechanistic explanation for the influence of the two-phase flow phenomenon caused by hydrogen evolution reaction on battery performance for the first time and lays a theoretical foundation for improving battery cycle life through side reaction management.

Electrochemical degradation of antibiotics using flow-through graphene sponge electrodes

Graphene sponge electrodes doped with atomic boron and nitrogen were employed for electrochemical degradation of antibiotics sulfamethoxazole, trimethoprim, ofloxacin, and erythromycin. The removal of antibiotics that displayed strong π-π interactions (i.e., ofloxacin) with reduced graphene oxide (RGO) coating was less limited by the mass transfer and removal efficiencies > 80% were observed for the investigated range of electrolyte flowrates. At the highest applied flowrate (700 LMH), increase in the anodic current significantly worsened the removal of trimethoprim and erythromycin due to the detrimental impact of the evolving gas bubbles. Increase in current at 700 LMH led to a stepwise increase in the removal efficiency of sulfamethoxazole due to its enhanced electrosorption. Electrochemical degradation was achieved via ozone, hydrogen peroxide and hydroxyl radical (•OH). Extraction of the employed graphene sponges confirmed the degradation of the strongly adsorbing antibiotics. Identified electrochemical transformation products of erythromycin confirmed the participation of •OH, through N-demethylation of the dimethylamine group. In real tap water, removal efficiencies were lower for all target antibiotics. Lower electric conductivity of tap water and thus increased thickness of the electric double layer likely limited their interaction with the graphene sponge surface, in addition to the presence of low amounts of organic matter.

Solid Electrolyte Interphase Growth in Lithium Metal Cells With Normal Electrolyte Flow

In high energy density lithium metal batteries (LMBs), dendrite and solid electrolyte interphase (SEI) growth reduce safety and longevity, respectively. A stable SEI layer enables high efficiency cycling but continued SEI growth can lead to reduced capacity and coulombic efficiency. In this paper, we develop a steady-state model that predicts the effect of small advective electrolyte flow towards the lithium metal electrode on SEI growth during charging. For a fixed current density, increasing the electrolyte flow rate improves the coulombic efficiency and decreases SEI layer growth rate. Decreasing the charging current density at a constant flow rate also decreases the SEI layer growth rate. Low flow rates (μm/s) can increase coulombic efficiency by up to 6%. The sensitivity of the coulombic efficiency to plating and SEI layer reaction rates is also explored.

Pore-scale modeling of mass transport in the air-breathing cathode of membraneless microfluidic fuel cells

The air-breathing cathode of membraneless microfluidic fuel cells (MMFCs) is in direct contact with flowing aqueous electrolyte rather than a solid polymer membrane, suggesting the mass transport characteristics can be different from the air-cathode in conventional membrane-based fuel cells. To investigate the mass transfer and reaction, pore-scale Lattice Boltzmann (LB) models were developed for the air-breathing cathode, including the gas diffusion layer (GDL), the catalyst layer and the electrolyte microchannel. A modified multi-relaxation-time LB model was developed to handle the very large diffusivity ratio (104) between gaseous and dissolved oxygen. The GDLs were numerically reconstructed to mimic the real microstructure. The effect of GDL property (porosity, isotropy) and operation conditions (overpotential, electrolyte flow rate) were investigated and discussed. The results indicated that the GDL microstructure played an important role for the oxygen transport and reaction in the air-breathing cathode. Oxygen was found to penetrate the electrolyte microchannel and could form a thin layer of dissolved oxygen covering the catalyst layer, which in-turn affected oxygen transfer in the GDL. The electrolyte flow can also affect local oxygen transport but only showed minimum impacts.

Modeling of gas evolution processes in porous electrodes of zero-gap alkaline water electrolysis cells

A three-dimensional two-phase model of an alkaline water electrolysis (AWE) cell containing potassium hydroxide solution was developed by meticulously considering gas evolution reactions, the dissolution of the evolved gas in the electrolyte, bubble formation above the critical oversaturation limit, blockage effects of electrochemical reactions, and charge transport by bubbles. A numerical two-phase model based on the Euler–Euler approach was adopted to describe bubbly two-phase flow during the cell’s operation. The numerical model was first validated against experimental data obtained for a wide range of current densities (up to 2.0 A/cm2). Subsequently, the effect of two-phase flow on the AWE performance was determined by conducting a comparative study in which various cell scales and operating conditions were considered. In particular, the initiation of two-phase flow and the effect of bubble coverage of the electrodes were examined for various electrolyte flow rates, operating current densities, and cell sizes. Simulation results showed that the nucleation of bubbles and the subsequent development of two-phase flow occurred at low electrolyte flow rates and/or for large-sized cells and that they increased the ohmic and activation overpotentials.

Simulation and experiment research on liquid channel of diffuser blade by electrochemical machining

Aiming to solve the problems of the low electrolyte flow rate at leading edge and trailing edge and poor uniformity of the end clearance flow field during the electrochemical machining (ECM) of diffuser blades, a gap flow field simulation model was established by designing three liquid-increasing channels at the leading edge and the trailing edge of the cathode. The simulation results indicate that the liquid-increasing hole channel (LIHC) with an outlet area S of 1.5 mm2 and a distance L from channel center to edge point of 3.2 mm achieves optimal performance. In addition, the experiment results show that the optimized cathode with liquid-increasing hole channel (LIHC) significantly improves the machining efficiency, accuracy, and surface quality. Specifically, the feed speed increased from 0.25 mm/min to 0.43 mm/min, the taper decreased from 4.02° to 2.45°, the surface roughness value of the blade back reduced from 1.146 to 0.802 µm. Moreover, the roughness of the blade basin decreased from 0.961 to 0.708 µm, and the roughness of the hub reduced from 0.179 to 0.119 µm. The results prove the effectiveness of the proposed method and can be used for ECM of other complex structures with poor flow field uniformity.