Low Rotational Speed Research Articles

Study of the impact of metallic components Cu, Ni, Cr, and Mo on the microstructure of Al2O3–Cu–Me composites

The study explores the microstructural design of hybrid Al2O3–Cu–Me composites formed by centrifugal slip casting into porous molds. Obtained composites are characterized by zones with different contents of metal phases. It was determined that there are two mechanisms driving thickening of slurries: capillary forces influencing smaller particles and centrifugal forces affecting larger particles. To enhance composite’s cracking toughness, a gradient distribution of metallic phase with highest metal concentration near surface is essential. This is achieved by optimizing ceramic powder size, limiting processing time, and using gel centrifugal casting to eliminate undesired zones. Zone II’s width is influenced by metallic phase proportion, mold rotation speed, and compaction rate, with heavier particles and greater metal content near outer surface. Zone III expands with lower rotational speeds and lighter metallic particles. The mutual reactivity and solubility of selected metallic elements also play a crucial role in the final microstructure. The findings highlight the potential for precise control over composite microstructures through careful selection of metallic elements, powder sizes, and casting parameters, offering valuable insights for model research and simulations.

An advanced Polynomial Chaos Expansion method for sensitivity analysis of aero-engine fuel gear pumps

Global sensitivity analysis plays an important role in robustness optimization design of aero-engine fuel gear pumps to investigate how input parameters uncertainties contribute to performances uncertainties. In this paper, inspired by the Leave-One-Out method, an advanced Polynomial Chaos Expansion (PCE) method equipped with Adaptive design of both training Points and polynomial Order, denoted as APO-PCE, is proposed to efficiently estimate the variance-based sensitivity indices. A novel active learning strategy is developed for identifying the optimal candidate sample point to adaptively design training points and simultaneously update the polynomial order. Input parameters, including rotational speed, inlet pressure, outlet pressure, and gear tip clearance, are reasonably characterized as nine convenient sampling Gaussian variables by probabilistic modeling and Karhuben–Loève expansion. The results show that the proposed APO-PCE method is superior to the classical PCE method, and the uncertainties of rotational speed, inlet pressure, and outlet pressure are the main factors for the uncertainties of supply performances and flow field characteristics, while the gear tip clearance uncertainty only affects the flow loss at lower rotational speed.

Optoelectronic Strain-Measurement System Demonstrated on Scaled-Down Flywheels.

Monitoring the strain in the rotating flywheel in a kinetic energy storage system is important for safe operation and for the investigation of long-term effects in composite materials like carbon-fiber-reinforced plastics. An optoelectronic strain-measurement system for contactless deformation and position monitoring of a flywheel was investigated. The system consists of multiple optical sensors measuring the local relative in-plane displacement of the flywheel rotor. A special reflective pattern, which is necessary to interact with the sensors, was applied to the surface of the rotor. Combining the measurements from multiple sensors makes it possible to distinguish between the deformation and in-plane displacement of the flywheel. The sensor system was evaluated using a low-speed steel rotor for single-sensor performance investigation as well as a scaled-down high-speed rotor made from PVC plastic. The PVC rotor exhibits more deformation due to centrifugal stresses than a steel or aluminum rotor of the same dimensions, which allows experimental measurements at a smaller flywheel scale as well as a lower rotation speed. Deformation measurements were compared to expected deformation from calculations. The influence of sensor distance was investigated. Deformation and position measurements as well as derived imbalance measurements were demonstrated.

Wear and thermal coupled comparative analysis of additively manufactured and machined polymer gears

This study investigates the potential use of additive manufacturing (AM)-produced gears in the polymer gear industry as an alternative to conventionally manufactured gears. The focus is on comparing the wear and thermal properties of polyamide 6 (PA6) gears, the most commonly used in industry, with those of polyetherimide (PEI) gears manufactured via AM. The research aims to determine whether AM offers any advantages over conventional methods, particularly with regard to wear resistance and thermal performance. The wear behaviour of both types of gears is examined under various operating conditions, with particular attention being paid to the initial wear rates and how they evolve. PEI and PA6 test gears were evaluated using a custom-built gear wear test rig. Throughout the wear test, polymer test gears were subjected to wear by running against a metal gear. The gears were tested at various rotational speeds for up to 1 million cycles. During this process, measurements were taken to determine surface roughness changes, operational noise levels, microstructure analyses using scanning electron microscopy (SEM), and chemical structure analyses using Fourier transform infrared spectroscopy (FTIR). Additionally, thermal properties such as temperature generation and stability are monitored with a thermal camera and infrared thermometer to understand the suitability of each gear material for different applications. PA6 gears demonstrate better wear resistance at low and medium rotational speeds, while PEI gears show superior performance at high speeds. Furthermore, PEI gears display enhanced thermal properties, with lower temperature increases during operation compared to PA6 gears; this can be attributed to the porous structure inherent in AM, which allows for better heat dissipation. The findings suggest that AM-produced PEI gears hold promise as an important alternative in high-speed applications due to their superior wear resistance and thermal performance compared to conventionally manufactured PA6 gears.

Additive friction stir deposition of Al 6061-B4C composites: Process parameters, microstructure and property correlation

Al 6061-B4C metal matrix composites were fabricated using a novel solid state additive manufacturing technique of additive friction stir deposition (AFSD). Incorporation of B4C particles into the deposit was achieved by employing hollow Al 6061 feed stock filled with B4C powder and three different AFSD tool rotational speeds (200, 300 and 400 rpm). Fabricated deposits exhibited remarkable metallurgical bonding across the substrate/deposit interface and interlayer interfaces for all tool rotational speeds, indicating a wider fabrication window. A physics based pseudo-thermo mechanical model was employed to evaluate the thermo-kinetic conditions experienced by the depositing material to correlate with the microstructural observations. Deposited layers exhibited refinement of grains to ∼10 μm from the corresponding coarse grain structure of feedstock (136 μm). The regions near the B4C particles were observed to have finer grains (<2 μm) signifying particle stimulated nucleation. Although considerable loss in the tensile properties (60 % drop in yield strength) was observed in the AFSD deposits due to the associated dissolution of β’’ precipitates, subsequent heat treatment restored the tensile properties to the level of as received material (∼290 MPa). The thermo-kinetic conditions (temperature in excess of 500 °C and strain rates in excess of 250 s−1) experienced by the builds under higher AFSD tool rotational speeds (300 and 400 rpm) appeared to result in refinement of Al–Fe–Si based secondary intermetallic precipitates/dispersoids leading to the observed higher stability of their microstructure during the subsequent post AFSD heat treatment. Samples AFSD fabricated with a lower tool rotational speed of 200 rpm, however, exhibited significant grain growth on account of relatively larger secondary precipitates/dispersoids.

Mechanical and microstructural characterisation on the effect of increasing tool rotational speed of friction stir welded AZ31-B magnesium alloy

ABSTRACT This article intends to deliver the mechanical and microstructural characterisation of the impact of increasing the tool rotational speed on friction stir-welded similar AZ31-B magnesium alloy. The variable tool rotational speeds of 1000, 1200, 1400, and 1600 rpm with a fixed tool traverse speed of 30 mm/min were chosen based on the trail welding method. The macrostructural examination reveals that the lower tool rotational speed of 1000 rpm produced micro tunnel defects due to insufficient heat input, which causes less material intermixing. The microstructural examination shows finer grain size values when increasing the tool's rotational speed for 1000 rpm (12.5μm), 1200 rpm (9μm), 1400 rpm (7μm), and 1600 rpm (7.6μm). The tool rotational speed of 1400 rpm produced a defect-free welded joint with a higher tensile strength value of 215 MPa and a higher hardness value of 74 HV. Fractography analysis reveals all four welded samples were ductile fractured at an angle of 450. The higher welded joint efficiency of 78% was attained at the 1400 rpm welded parameters and the lower efficiency of 48% was achieved at the tool rotational speed of 1000 rpm.

Effect of solid lubricant reinforcing on drilling performance of castamide and thermal analysis

AbstractThis study addresses the pressing need for enhancing the machining performance and hole quality of castamide by investigating the effects of solid lubricant addition and drilling parameters. Castamide, a highly crystalline polyamide synthesized via anionic ring‐opening polymerization, offers superior mechanical, physical, and chemical properties compared to conventional polyamide 6. However, its machining process, particularly drilling, remains a critical challenge due to its viscoelastic nature and sensitivity to heat generation. Using experimental investigations, thrust forces, drilling temperatures, hole geometry, and quality parameters are systematically analyzed and discussed. Notably, the study introduces Kestlub, a modified version of castamide with solid lubricant, and evaluates its drilling performance, a previously unexplored area in the literature. The research employs response surface methodology to model experimental data, considering both linear and quadratic effects of drilling parameters. Additionally, the significance of each parameter is assessed using ANOVA tables and Pareto charts, offering valuable insights into optimizing the drilling process for enhanced hole quality in castamide. It found that optimal drilling conditions occur at low rotational speeds and high feed rates, but thermal damage, influenced by factors like thermal conductivity and transition temperature, affects hole geometry and burr formation.Highlights Drilling performances of solid lubricant reinforced castamides were investigated. Drilling temperatures were recorded with a thermal camera and differential scanning calorimeter and thermal gravimetric analyses were performed. Drilling properties were analyzed statistically according to the response surface method. It found that optimal drilling conditions occur at low rotational speeds and high feed rates.

Numerical study of dense powder flow in a rotating drum: Comparison of CFD to experimental measurements

Designing chemical reactor equipment requires a thorough understanding of powder flow. Solid rheology modelling offers various models for this purpose. A comparative study of two different CFD models, the Kinetic Theory of Granular Flow (KTGF) and the dense granular flow (μI law), is proposed. Both models were confronted with experimental results obtained on a rotating drum for different rotation speeds and powder flowabilities. Image processing was used to compare the experimental gas/solid interfaces with those obtained from CFD. The KTGF model did not represent the powder rheology at low rotation speeds, regardless of the powder, whereas it was closer to experiments at higher speeds. The dense granular flow model was more appropriate for this system as it described the powder shape inside a rotating drum relatively well for each experiment. The latter model is recommended for modelling dense granular flows, while the KTGF is better suited to gas-solid flows.

Vibration of Variable Speed Pump-Turbine in Turbine Operating Range: Simulation by CFD+FEM

Abstract Variable speed pumped-storage unit can operate efficiently and stably in wide range of power and head through the coordinated control of the rotational speed and guide vanes. The regulation in rotational speed brings about frequency and amplitude changes of pressure pulsations, which further influence the avoidance margin of vibration and the dynamic response of the runner. The vibration characteristics of the variable-speed pump-turbine need to be studied when it runs in the wider operating region. Selecting an actual pumped-storage unit as the subject and using the CFD+FEM coupled simulation method as a tool, we conducted three-dimensional pump-turbine vibration simulations and analyse the flow patterns, pressure pulsations, and runner vibration characteristics of several typical operating points in turbine mode. The study focused on the variation laws of pressure pulsations and dynamic stresses when rotational speed is regulated. Comparison with the results for the constant speed unit under the corresponding working conditions was conducted. It is shown that the variable speed operation can effectively avoid the severe vibration conditions that the constant speed unit encounters; the amplitudes of pressure pulsations and dynamic stresses of the runner are small at low rotational speed; in the condition of high speed, low head, and small load, the vibration is the most obvious. This study can provide a reference for the design and operation of variable speed pump-turbine.

On the transitional wake past a streamwise rotating prolate spheroid

Direct numerical simulations are performed to study the behavior of the wake behind a 5:2 streamwise rotating prolate spheroid. The Reynolds number Re = 1000 under different rotational speeds over a large range of 0≤Ω≤3 is considered, where Ω is the non-dimensional rotational speed based on the freestream velocity and the volume-equivalent diameter of the prolate spheroid. By successively increasing the rotational speed, seven distinct flow regimes were identified and explored: steady state, low-speed steady rotation state, axisymmetric state, high-speed steady rotation state, twofold rotational symmetrical state (TFRS), quasi-periodic vortex shedding state (QVS), and weakly chaotic state. Among these wake regimes, the TFRS regime is reported for the first time, and it can be interpreted as an outcome of the stabilizing influence of the spheroid's rotation acting to restore the wake structure to an axisymmetric state. It is found that the rotation of the prolate spheroid has a stabilizing effect under low rotational speeds. Furthermore, the coupling mechanism between the rotational double helical structure and vortex shedding in the QVS regime has been revealed. The results of this study contribute to closing the knowledge gap regarding the wake dynamics of a streamwise rotating prolate spheroid.

Evaluating the Microhardness Profiles in Friction Stir Welding of Dissimilar Alloys

Abstract: Friction stir Welding (FSW) advancement is used generally in the utilization of present-day flying and vehicle industry for predominant fundamental mentioning. Such a joining technique is displayed to avoid serious twists and the made excess weights are exhibited as low when it is stood out from the traditional welding structure. In this research, focus on to identify the parameters that will provide the dissimiliar alloys of aluminium AA6061 and AA8011 with good microhardness properties. From the current study microhardness strength of dissimiliar alloys of aluminium varies with the rpm, feed rate and shoulder diameter of the tool. At 2000 rpm and 15mm/min welding speed strength of joints is low and at high rpm 2400 and welding speed 20mm/min micro hardness strength is always low but at a rotation speed of 2200 rpm and welding speed 20 mm/min maximum strength of the weld joint . Hence at high rotational speed rise in the temperature occurs and cause dissolution of precipitates which lowers the hardness and at low rotational speed less heat generation at the tool workpiece interface causing less refinement of grains which lower the hardness value. During tensile strength test fracture and cracks occurs at weld center line.

Оценка нестабильности последовательных впрыскиваний топливной аппаратуры дизелей

The issues of uneven cyclic feed in sequential injections by diesel fuel equipment are considered, which is directly related to solving the problem of ensuring the quality of operation of engines of various types and purposes when operating at low loads and rotational speeds. The special importance of solving these problems from the standpoint of ensuring fuel efficiency, environmental pollution, solving issues of engine reliability and improving their operational properties was noted. The features of the formation of residual fuel pressure in the high-pressure pipeline are revealed. The periodic fluctuations of the cyclic feed and injection parameters from cycle to cycle are estimated. A study of possible options for the operation of fuel equipment in low fuel supply modes has been carried out. Based on the analysis, a criterion for evaluating the instability of successive injection cycles for diesel fuel equipment during its operation in various modes has been introduced. By studying numerical examples, the conditions of unstable fuel supply processes in successive injections of various characteristic modes are determined. The criterion determines the quality of the fuel equipment of marine diesel engines and diesel generators in terms of ensuring a minimum stable idle speed and the possibility of ensuring stable reduced fuel supplies. The variability of fuel supply processes in sequential feeds is the cause of increased exchange processes of electric power flow during parallel operation of diesel alternators and reduces the performance characteristics of diesels for various purposes when operating in partial modes. In the process of carrying out development work, scientific research and during the refinement of diesels, the instability criterion allows us to assess the quality of the fuel equipment precisely in partial modes. This is of particular importance for diesel engines of fishing vessels operating for a long time at shared loading modes and low idle speeds, as well as for engines of the tugboat fleet and auxiliary diesel generator sets of all types of facilities used.

Control for Wind Turbine System using PMSG when Wind Speed Changes

This paper presents the proposed model to control grid-connected wind turbine by permanent magnet synchronous generator (PMSG). With the wind speed changing continuously, the rotor system needs to be able to self-regulate according to wind speed and direction to ensure efficient operation of the turbine. The PMSG was chosen because the magnetic flux is always available thanks to the permanent magnet system glued to the rotor surface. The generator provides power with low rotational speed but high efficiency. These are the important advantages of using PMSG for wind turbine. Matlab - Simulink software was used to design the controllers and the survey results proved that this control system meets the power quality requirements when connecting to the grid and optimizing the energy conversion process for turbine wind.

Extraction and characterization of Cucumis melon seeds (Muskmelon seed oil) biodiesel and studying its blends impact on performance, combustion, and emission characteristics in an internal combustion engine

This study examines the performance, combustion, and emissions characteristics of a single-cylinder internal combustion diesel engine when fueled with a blend of diesel and biodiesel derived from muskmelon seeds. The kinematic viscosity of the extracted muskmelon seed oil was 6.1 cSt at 40 °C, which is higher than the kinematic viscosity of petroleum diesel of 2.6 cSt. Muskmelon biodiesel was further analyzed using thin-layer chromatography (TLC) and high-voltage separator tests. A comparison of the fuel properties of muskmelon biodiesel with conventional diesel fuel revealed that muskmelon biodiesel could be used alone or in a diesel–biodiesel blend to fuel compression diesel engines. In this study, muskmelon seed biodiesel was blended with diesel fuel at proportions of 10 %, 20 %, and 50 % (BD10, BD20, and BD50, respectively). At a relatively low rotational speed of 1200 rpm, the brake thermal efficiency (BTE) of the engine operated with BD10 and BD20 blends were 36.1 % and 36.0 %, respectively, while the brake-specific fuel consumption (BSFC) of the two blends were 0.260 kg/kWh, and 0.262 kg/kWh, respectively. These values closely resemble those typically observed in diesel fuel engines. Indeed, the average BTE of the BD20 blend was only 3.24 % less than the average BTE of diesel fuel. Diesel fuel generates less NOx and SO2 emissions compared to biodiesel blends: BD100 emitted the most NOx pollution of all fuels tested. In addition, BD10 released significantly more SO2 emissions compared to the other fuels tested. However, the BD20 blend outperformed all other blends in terms of CO, NOx, and SO2 emissions at high engine speeds. The only exception was H2S emissions, which were higher than BD50 and BD100. BD20 also exhibited significantly reduced CO emissions compared to diesel fuel, while BD10 emitted significantly more CO emissions than the other biodiesel blends. Our findings revealed that BD20 exhibited the best engine performance and lower emissions among all fuels tested. In other words, BD20 is the ideal fuel blend for use in diesel engines and does not require any alterations to the engine. Muskmelon waste seeds represent a non-edible waste stream that can be exploited in the production of biodiesel fuel, allowing for the upcycling of a potentially problematic thermochemical conversion feedstock. This potentially valuable use for waste muskmelon seeds in the energy sector could address the wastefulness associated with this particular waste stream.

СТІЙКІСТЬ РОБОЧИХ РЕЖИМІВ АВТОНОМНИХ АСИНХРОННИХ ГЕНЕРАТОРІВ ІЗ САМОЗБУДЖЕННЯМ

The paper presents the results of investigation the stability conditions of self-excited induction generators. A mathematical model of the generating system with an analytical description of the dependence of the magnetization inductance on the current is used. It allows to avoid the iterative procedure and to scale the dependence to determine the magnetization inductance for induction machines of different types and power. The influence of the load inductance on the stability of the generating system at different rotational speeds is investigated. It is shown that an increase in the inductance value increases the system stability margins in the self-excitation zone. Also this article deals with the issues of system stability within the self-excitation zone of an induction generator at different rotational speeds depending on the value of the capacitance of self-excitation capacitors. It is depicted that at low rotational speeds there may not exist a stable operation mode in the self-excitation zone regardless of the value of the capacitance in the motor stator circuit. This method of determination the stability of the operation modes of the generation system will be useful both for the design of new systems and for the modification and adjustment of existing ones. References 9, figures 4.

Global flattening realization and kinematic analysis of UV-assisted low-speed 3D dynamic friction-polished diamonds

Diamond has attracted extensive attention from many scholars because of its unique properties. However, there are still bottlenecks in how to achieve high efficiency polishing and global flattening of diamond which restrict its application. The aim of this study is to obtain a globally homogeneous flattened diamond surface in macro dimension by introducing a compound motion of the polished workpiece. It is shown that ultra-smooth diamond surface machining with global flattening can be realized by UV-assisted low-speed dynamic friction polishing technique, and the typical roughness is 0.175 nm as measured by 3D optical surface profiler. These experimental results demonstrate that the catalytic phase transition process of UV light is the underlying mechanism to realize the diamond surface polishing under low rotational speed conditions. Additionally, the composite motion of the diamond sample with the metal disk brings large enhancement to the effect of polishing global flattening on the sample surface. The theoretical and experimental studies in this paper provide novel ideas for achieving efficient and polished global flattening of diamond.

Eliminating Cu-rich intermetallic compound layer in dissimilar friction stir welding of 304 stainless steel and 2219 Al alloy via ultralow rotation speed

The formation of the Cu-rich intermetallic compound (IMC) layer at the interface has always been the critical bottleneck of welding steel to 2xxx series Al alloys with high Cu content. In this study, we successfully eliminated the Cu-rich IMC layer by using a modified friction stir welding (FSW) method under an extremely low rotation speed of 200 rpm. At an appropriate thickness difference of the welded plates, defect-free FSW joint of 304 stainless steel to 2219Al alloy with high tensile strength of 210 MPa was obtained, and the sample failed in the 2219Al side rather than at the interface. It is found that a continuous Al-Fe-O amorphous layer of ∼10 nm in thickness formed at the steel-Al interface, and only few Al2Cu IMC particles existed at the interface. The Al2Cu particles were blocked by the amorphous layer and cannot directly contact the steel, consequently realizing the excellent metallurgical bonding between the steel and 2219Al alloy. It is anticipated that this work will provide a feasible strategy for fabrication high-quality dissimilar joints between steel and 2xxx series Al alloys, which can broaden the application of steel-Al joints in the industries.

Dielectrophoretic separation/classification/focusing of microparticles using electrified lab-on-a-disc platforms

BackgroundSeparation, classification, and focusing of microparticles are essential issues in microfluidic devices that can be implemented in two categories: using labeling and label-free methods. Label-free methods differentiate microparticles based on their inherent properties, including size, density, shape, electrical conductivity/permittivity, and magnetic susceptibility. Dielectrophoresis is an advantageous label-free technique for this objective. Besides, centrifugal microfluidic devices exploit centrifugal forces to move liquid and particles. The simultaneous combination of dielectrophoretic and centrifugal forces exerted on microparticles still needs to be scrutinized more to predict their trajectories in such devices. ResultsAn integrated system utilizing two categories in microfluidics is proposed: dielectrophoretic manipulation of microparticles and centrifugal-driven microfluidics, followed by a numerical analysis. In this regard, we assumed a rectangular microchannel with internal unilateral planar electrodes equipped with three equal-sized outlets placed radially on a centrifugal platform where microparticles flow toward the disc's outer edge. The effect of different coordinate-based parameters, including radial and lateral distances (X and Y offsets)/tilting angles toward the radius direction (α), on the particles' movement was investigated. Additionally, the effect of operational parameters, including applied voltage, the microchannel width, the number of enabled electrodes, the diameter of particles, and the configuration of electrodes, were analyzed, and the distributions of particles toward the outlets were monitored. It was found that enhanced particle focusing becomes possible at lower rotation speeds and higher electric field values. Furthermore, the proposed centrifugal-DEP system's efficiency for classifying red blood cells/platelets and Live/Dead yeast cells systems was evaluated. SignificanceOur integrated system is introduced as a novel method for focusing and classifying various microparticles with no need for sheath flows, having the ability to conduct particles at desired routes and focusing width. Furthermore, the system effectively separates various bioparticles and offers ease of operation and high-efficiency throughput over conventional dielectrophoretic devices.

Dynamic damage and fracture mechanism of curved ripper cutting reinforced concrete composites: Numerical simulation combined with engineering practice

Shield tunnels inevitably cross existing structures like reinforced concrete pile foundations and concrete walls due to the spatial interlocking of underground structures in the construction process. The objective of minimizing cutter damage during the cutting of reinforced concrete pile foundations is widely pursued in engineering. In this study, a numerical model of curved ripper cutting reinforced concrete composites was established, with the engineering background of Nanjing Metro Line 10 shield tunnel crossing the pile foundation of Youth River Bridge. The dynamic damage and fracture of reinforced concrete composites under the cutting of single, double, and multiple rippers were comprehensively investigated. The effects of the operating parameters and geometric parameters on the cutting performance were discussed. Finally, a statistical analysis was carried out to evaluate the damage of 148 rippers and the fracture of rebar in an actual engineering project. The simulation results reveal that coordinated cutting of five rippers has optimized the fracture mechanism of the rebar, weakening the compression effect between the ripper and the rebar, and highlighting the tensile fracture of the rebar. It is appropriate to set the alloy blade angle at 90° and the blade width at 10 mm for practical engineering applications. The penetration has a significantly greater influence compared to cutting speed. In practical engineering, adopting a low penetration and high rotation speed grinding mode is advantageous for reducing blade fractures. The central fishtail cutter and the rippers in the outer area of the cutterhead are more prone to damage during the pile cutting process and warrant additional reinforcement measures. The findings provide comprehensive and innovative insights into shield cutting reinforced concrete pile foundations.

Optimizing mixing efficiency of anaerobic digesters with high total solids concentrations using validated CFD simulations

In this article, viscosity dependent mixing in anaerobic digestion (AD) towers is analysed using finite volume based computational fluid dynamics (CFD) simulations validated with ultrasound particle image velocimetry (uPIV). The study focuses on improving mixing characteristics for enhanced biogas production resulting from increased organic loading. Mixing of fluids with viscosity ranges found in real-life AD is investigated using the multiple reference frame (MRF) method. The aim is to increase the energetic efficiency of AD by reducing the energy demand required for sufficient mixing such that microorganisms and organic substrates are homogeneously distributed. The distinguishing feature of this work is the implementation of less power-consuming helical ribbon stirring devices (HRSD) for enhanced mixing in different reactor designs. It is demonstrated that HRSD become progressively effective for increasing total solids concentrations (% TS) ranging from 2.5 % TS to 12.1 % TS, particularly in cylindrical reactors. In comparison with conventional propeller-based mixers, innovative HRSD operation reduces dead volume (DV) by up to 22 %. Additionally, HRSD cause less shear forces and require less power due to lower rotational speed. The most energy-efficient mode of operation reduces the power demand by 9.29 % at 12 rpm, while still providing decreased DV of 13.38 % for the most viscous fluid investigated. The outcome is a more efficient and cost-effective mixing approach, which holds strong potential for mixing applications involving highly viscous fluids.