Search Results (1,871)

The cylindrical hydrocyclone can be regarded as a special-shaped hydrocyclone comprising entirely cylindrical sections without conical sections, featuring a unique flat-bottom design combined with central discharge, which promotes substantial particle circulation flow in the separation chamber, directly affecting separation performance. A validated TFM model is employed to investigate the flow field and particle motion behavior in the cylindrical hydrocyclone. The results indicate that the distributions of tangential velocity, radial velocity, pressure, and pressure gradient in the cylindrical hydrocyclone are consistent with patterns observed in the conventional hydrocyclone. The flat-bottom design combined with the central discharge configuration of the cylindrical hydrocyclone results in two distinct axial velocity transitions in the bottom region, forming downward axial velocity flow around the air core. Accordingly, particles moving toward the spigot must pass through the internal swirling flow region, facilitating the fine particles entrained by the coarse particles to enter the internal swirling flow, reducing the misplacement of fine particles in the underflow. Simultaneously, coarse particles entrained by the internal swirling flow return to the external swirling flow region under centrifugal force, forming a substantial coarse particle circulation flow. As a result, a mass of coarse particles accumulates in the separation chamber, hindering the centrifugal settling of medium particles and resulting in an enlarged cut size and severe coarse particle misplacement. Full article

This paper develops an analytical treatment of vibro-acoustic wave propagation in a cylindrical waveguide containing two clamped elastic membranes and a central flexible-shell segment. The acoustic field obeys the time-harmonic Helmholtz equation, the shell motion is described by Donnell–Mushtari thin-shell theory under axisymmetric loading, and the membrane response is governed by classical membrane theory and incorporated through a tailored Galerkin scheme. The resulting coupled fluid–structure boundary-value problem is solved by the Mode-Matching Method: the acoustic potentials are expanded in orthogonal radial eigenfunctions within each subregion, and continuity of pressure, normal velocity, and structural displacement are enforced at every interface. The mirror symmetry of the configuration is exploited by an exact decomposition into symmetric and anti-symmetric sub-problems, each of which reduces to a truncated linear algebraic system of dimension $4N+4$ for the unknown modal amplitudes. Acoustic power-balance identities provide a quantitative consistency check on the numerical implementation and diagnose convergence with respect to the truncation order; structural damping is accommodated through complex-modulus substitutions for the shell and the membrane tension without altering the algebraic structure of the system. The numerical results demonstrate that the dual-membrane configuration delivers transmission-loss values exceeding $25\mathrm{dB}$ across the low-frequency band relevant to HVAC and automotive applications, with a representative plateau near $13\mathrm{dB}$ at the reference geometry, through resonance-driven modal coupling between the acoustic field and the compliant interfaces. Parametric studies identify the excitation frequency, the inner-membrane radius, the shell radius, and the chamber length as effective design parameters for tuning the attenuation. The formulation furnishes a unified and computationally efficient analytical tool for predicting and optimising noise attenuation in flexibly coupled cylindrical duct systems. Full article

Heat pump technology can efficiently recover waste heat from oil and gas gathering, processing, and transportation. However, the energy transfer mechanism of high-speed rotating internal flow in the scroll compressor remains unclear under unbalanced load conditions, leading to low equipment energy efficiency and high operation and maintenance costs. This study adopted dynamic grid technology, finite element analysis and one-way thermal–fluid–solid coupling method to quantitatively study the flow field characteristics and mechanical response of four characteristic phases. The results showed that the internal pressure and temperature fields of the compressor presented a non-uniform distribution. The deformation of the scroll wraps was mainly concentrated in the compression chamber, and the maximum stress was concentrated at the wraps’ root. Further analysis revealed that temperature loading played a dominant role in the structural responses. At a spindle rotation angle of 0°, under temperature loading alone, the maximum deformation and maximum stress were 28.605 μm and 521.81 MPa, respectively, while the corresponding values under pressure loading alone were small. In addition, the deformation and stress under coupled loading were not a linear superposition of the individual loading effects, with a deformation deviation of 0.938 μm and a stress deviation of 7.18 MPa at a spindle rotation angle of 0°. In this study, a numerical model of the scroll compressor was established and experimentally verified, which provided a theoretical basis for optimizing scroll profile design, suppressing wrap tip wear and improving the energy efficiency of heat pump systems. Full article

High-voltage self-blast circuit breakers feature complex gas flow field dynamics during the arc interruption process due to the multiple gas chambers and valves in the interrupter. The structure of key interrupter components and the characteristics of the operating mechanism significantly influence the gas flow field behavior, thereby affecting the breaking performance. The C₄F₇N gas mixture is currently the most promising alternative to SF₆. However, the influence mechanisms of various factors on its breaking performance remain unclear, which limits the design of C₄F₇N-based self-blast interrupter chambers. This paper investigates the impact of nozzle throat length and mechanism stroke on the breaking performance of a 126 kV double-motion self-blast circuit breaker prototype by establishing a magnetohydrodynamic (MHD) arc model for C₄F₇N gas mixtures. The results indicate that a longer throat length can enhance the pressure-buildup capability in the expansion chamber to some extent, but its effect on short arcing times is limited, whereas it has a more pronounced influence on medium and long arcing times. However, it also impedes arc energy dissipation, potentially reducing the breaking capability for short and medium arcing times while improving performance for long arcing times. A larger mechanism stroke not only ensures a greater contact gap at current zero for long arcing times but also accelerates the gas flow velocity between the contacts, facilitating arc energy dissipation and enhancing the thermal interruption performance. Full article

A dusty thermal vacuum chamber (DTVAC) equipped with a regolith simulant bin is a key infrastructure to validate space equipment planned to operate in the future lunar missions. The proper setup of such infrastructure is challenging since the regolith simulant needs to be outgassed; otherwise, it might affect the validation process. This paper presents the results of experiments conducted in a dusty thermal vacuum chamber. The experiment was designed to verify if lunar regolith simulants prepared and placed in the bin may preserve atmospheric gases after the chamber depressurization process. Such hypotheses were defined after testing a drill in vacuum conditions, the performance of which was higher than expected. The obtained results show that the preparation and placement of regolith in the bin should be performed under vacuum conditions regardless of the external temperature. Full article

The SF₆ circuit breaker is an essential piece of high-voltage equipment in ensuring the safe operation of the power grid. Regarding the arc-extinguishing chamber, as the most essential component, its performance is directly related to the breaking capacity of the circuit breaker. This study applies the Double Distribution Function Lattice Boltzmann Method (DDF-LBM), combined with the Smagorinsky sub-grid scale (SGS) model, to systematically simulate the dynamic breaking process of a 252 kV SF₆ arc-extinguishing chamber under 50 kA breaking current conditions. Two independent distribution functions are employed to describe the fluid field and the temperature field, respectively, thereby simulating the physical flow–heat coupling process. A dynamic simulation framework is constructed using the D2Q9 model to describe the mechanical motion of the contacts and the fluid flow. The description of contact movement is achieved by dynamically updating the geometric mesh, thereby realizing fluid–solid transformation. The research results indicate that the proposed method can simulate the pressure variation of the fluid field during the breaking process. The value of the Smagorinsky constant (C_s) exhibits a non-negligible influence on the pressure field predictions. The optimal value of C_s = 0.10 is determined through analysis, and the peak pressures at the upstream and throat measurement points reach 1.11 MPa and 1.37 MPa, respectively. Numerical simulations are conducted on the dynamic breaking process of the arc-extinguishing chamber, revealing the evolution of the pressure field upstream of the nozzle and at the throat regions. This study provides new numerical simulation methods for the investigation of SF₆ arc-extinguishing chambers and establishes a foundation for the application of the Lattice Boltzmann Method in the field of high-voltage electrical appliances. Full article

This paper conducts numerical simulations of nozzles with different structural parameters based on fluid mechanics, computational fluid dynamics and jet theory. The structural parameters of the nozzles were optimised by analysing flow field characteristics such as the pressure distribution within the nozzle chamber, velocity distribution, curves of the outlet cross-sectional area and external axial velocity, and velocity uniformity. Combining the results of orthogonal experiments, the optimal combination of factors was determined, and the impurity removal efficiency of the optimised nozzle was tested in the field, providing a reference for subsequent optimisation design. The results indicate that adding a fillet transition to the nozzle can mitigate sudden pressure drops and suppress the generation of vortices; when the fillet transition radius is 80 mm, the flow performance approaches the optimum; the optimal combination of the three factors was determined to be a contraction angle of 13°, λ of 0.65 (corresponding to an outlet height of 27 mm and an inlet diameter of 41 mm), and a nozzle length of 15 mm; this configuration yields the best external flow field characteristics and velocity uniformity; Analysis of the orthogonal test results indicates that the contribution of each structural parameter to velocity uniformity, in descending order, is: contraction angle (77.16%), λ (outlet height/inlet diameter) (18.25%), and nozzle length (0.73%); Field tests confirmed that the removal efficiency of foreign fibres using the optimal parameter combination remained consistently above 95%, with an overall average removal rate of 96.31%. This represents an improvement of approximately 7.5 percentage points compared to the original nozzle (88.83%). The optimised nozzle reduced the number of false rejections of cotton by 57%, demonstrating excellent and highly stable overall removal performance. The influence of the nozzle’s vertical height and its angle relative to the cotton on the removal efficiency requires further investigation. Full article

Aiming to address the problems of shield chamber blockage and poor muck discharge faced by earth pressure balance shields during tunneling in sandy strata, bentonite slurry is used for muck improvement. Using a multi-scale approach combining macro-scale experiments, micro-scale analysis, and molecular dynamics simulations, this study systematically investigates the interface interactions between particles of sandy soil in shield tunneling and the improvement mechanism of sodium-based bentonite slurry additives. Through the macroscopic experiment, the sodium bentonite slurry soil–water ratio of 1:7 and injection ratio of 25% showed the best improvement effect. After improvement, the permeability coefficient decreased by 99.72%; the cohesion of the excavated soil increased from 3.055 kPa to 11.458 kPa, representing a 275.06% increase; and the angle of internal friction decreased from 42.318° to 36.985°, a decrease of 12.60%. The improvement was significant. Through SEM, XRD, and FTIR microanalysis, it is found that bentonite slurry forms a flexible film on the surface of sandy soil. By coating sand particles, filling voids in the soil, and enhancing interparticle cohesion, it improves the properties of the soil. On the nanoscale, a Na-MMT/SiO₂ system model is established based on molecular dynamics simulations to elucidate the interactions between bentonite slurry and sand particle interfaces. The results indicate the presence of van der Waals forces and hydrogen bonds between Na-MMT and SiO₂. Interlayer water molecules form a hydrogen bond network that strengthens interfacial bonding, enabling bentonite slurry to tightly adhere to soil particle surfaces. This improves the microstructure of the soil, thereby enhancing its macroscopic properties. Full article

Sweeping jet (SWJ) actuators are widely used in active flow control, but explicitly resolving actuator-scale unsteadiness in full-configuration computational fluid dynamics (CFD) remains prohibitively expensive because of the small geometric scales and high-frequency oscillations involved. Existing reduced-order boundary-condition models constructed from exit-plane data alone can reproduce the observed switching waveform, but they treat the actuator as an input–output black box and provide limited insight into the internal dynamics that generate the response. This work develops a causal state-space reduced-order modeling framework that links internal mixing-chamber dynamics to time-resolved exit-plane boundary conditions. Proper orthogonal decomposition (POD) is used to obtain a low-dimensional representation of the internal flow, and a data-driven linear evolution operator is identified in the reduced space by least-squares regression of successive snapshot pairs. A POD truncation rank of $r=60$ is selected from cumulative-energy and validation-error sensitivity analyses, capturing well above 99% of the fluctuation energy while lying within the converged performance regime. A corresponding reduced operator is identified for the exit plane, and spectral comparison reveals near-neutrally stable oscillatory modes in both regions. Using a $\pm 1\%$ relative frequency-matching tolerance, the dominant reduced-operator modes exhibit a 28.3% frequency overlap, providing operator-level evidence that exit-plane oscillations are dynamically linked to internal coherent structures. This correspondence is further supported by cross-spectral coherence analysis between representative internal and exit-plane probe signals, which shows strong coherence at dynamically relevant frequencies. A delayed causal output mapping is then formulated in which the internal reduced state drives the exit-plane response after an identified lag of 149 time steps, corresponding to $2.98\times {10}^{-3}$ s. This delay provides a physically interpretable convective transport timescale from the mixing chamber to the actuator exit. Over the validation interval, the model maintains a mean relative $L_2$ error below 0.02, with maximum normalized errors below 0.04 for most of the prediction horizon, and localized increases are confined to rapid jet-switching events. Field-level reconstructions of streamwise velocity and total pressure show that the model captures both phases of the jet-switching cycle, with errors concentrated primarily in high-gradient shear-layer regions. Compared with exit-only reduced-order models, the proposed internal-driven formulation improves amplitude and phase fidelity over extended prediction horizons. The resulting framework provides a compact, interpretable, operator-based representation of SWJ actuator dynamics suitable for use as a CFD-embeddable dynamic boundary condition. Full article

Soft modular grippers play a significant role in multiple fields due to their excellent adaptability and flexibility. This paper proposes a modular soft modular gripper driven by pneumatically actuated multi-chambers. The designed soft modular gripper features three operational modes, with its modular fingers employing independently controlled dual chambers. The distal and proximal dual-chamber structure enhances the fingertip force of the modular fingers. Based on classical laminated plate theory and incorporating the large deformation characteristics of soft materials, a relationship between the bending centerline of the fingers and the driving pressure is established, providing a theoretical foundation for grasping tasks executed by the soft modular gripper. The Denavit-Hartenberg (D-H) parameter method is utilized to develop the coordinate system of the soft modular gripper, thereby defining its operational workspace. Visual sensing technology is introduced, incorporating improvements to the YOLOv8-based object recognition and localization framework, which enhances recognition accuracy for target objects and ensures grasping stability. Full article

Different from isothermal amplification, for polymerase chain reaction (PCR), highly reliable valving for PCR chamber, significantly shortened thermal cycling time, and concise multiplexed detection are always challenges for microfluidic-based devices. Here, we present a real-time, centrifugal, plastic microfluidic chip for multiplexed PCR detection specifically based on the mechanism of cooperating valving. To achieve consistent amplification, a concise dual-valving strategy was developed. Instantly melted wax is centrifuged and completely filled into the narrow channel and hole to act as the compact wax valve. Meanwhile, an elastic and sticky membrane is depressed to seal the hole to act as the membrane valve. The wax valve is protected by the membrane valve from being damaged by both mechanical deformation and thermal corroding caused by the hot vapor with high pressure from the PCR chamber. A double-sided heating strategy is adopted to reduce the thermal cycling time; meanwhile, a balanced mechanism is used to achieve real-time amplification by rotating the centrifugal chip between the heating and detection positions in turn. As a proof-of-concept, the performance of the centrifugal chip with four parallel units is demonstrated by successfully detecting purified DNA templates or the extracted DNA templates from cells as well within 20 min. Full article

This study investigates the explosion suppression of N₂ and CO₂ on NH₃/H₂/air mixtures (NH₃:H₂ = 4:6, φ = 0.6–1.5) in a 5 L constant volume chamber. Results show that CO₂ exhibits superior efficacy compared to N₂. At φ = 1.0, the addition of 25% CO₂ reduces the maximum explosion overpressure and maximum pressure rise rate by 59.28% and 91.00%, respectively, whereas the corresponding reductions caused by 25% N₂ are 29.28% and 83.85%. The laminar burning velocity decreases continuously with increasing inhibitor concentration under all investigated conditions, and the reduction caused by CO₂ is markedly greater than that caused by N₂. Kinetic analysis indicates that the stronger suppression effect of CO₂ is mainly associated with its stronger dilution and heat-absorption effects, together with its stronger influence on radical evolution, as reflected by the more pronounced reduction in key radical concentrations. To compare the suppression behaviours of N₂ and CO₂ under different conditions, three indices—the experimental maximum explosion overpressure suppression efficiency (S_T), the theoretical maximum explosion overpressure suppression efficiency (S_E), and the operating-condition suppression efficiency (η)—were introduced as comparative parameters. These results provide useful insight into the different suppression behaviours of N₂ and CO₂ in NH₃/H₂/air explosions. Full article

This paper presents a conceptual design for a technological installation aimed at mitigating ventilation air methane (VAM) from coal mine exhaust shafts, offering combined heat and power generation. It addresses the challenge posed by low methane concentrations (below 0.7%), which preclude direct combustion. To overcome this, the proposed concept involves diverting a portion of the VAM to a combustion chamber of the power boiler dedicated to co-combustion with flotation concentrate suspension, which is properly prepared for feeding into the combustion chamber. The heat generated in the power boiler produces steam to drive a turbine generator for electricity production. Back-pressure steam from the turbine can be utilized for district heating or as a thermal energy source for various industrial processes, optimizing the plant’s energy efficiency and reducing its environmental footprint. The feasibility of this technology hinges on its cost-effectiveness and energy efficiency. This aspect of efficiency has been outlined. An energy balance analysis, based on real emission data from a selected mine, is provided to determine power boiler efficiency, fuel consumption, and a VAM reduction rate. The forecast of the amount of energy produced was presented for a single installation with a grate boiler capable of co-firing fuels with a VAM flow participation of 25 m³/s. Such installations can be scaled to meet mine requirements, enabling the neutralization of VAM at a total capacity of up to 300 m³/s, which corresponds to emissions from a large ventilation shaft. Full article

The structural and electrical transport properties of brucite [Mg(OH)₂] were investigated by virtue of in situ Raman spectroscopy and alternating-current impedance spectroscopy under conditions of 0.5–20.2 GPa, 298–873 K, and different hydrostatic environments using a diamond anvil cell (DAC). Under the non-hydrostatic condition, the emergence of new Raman peaks and discontinuities in Raman shifts, FWHMs, as well as electrical conductivity well disclosed a hydrogen-disordering structural phase transition in brucite from the ordered ($P\overline{3}m1$ symmetry)–disordered ($P\overline{3}$ symmetry) structure at 5.7 GPa. Under hydrostatic condition, this transformation occurs at a lower pressure of 3.6 GPa using the 4:1 methanol–ethanol mixture (ME) as the pressure-transmitting medium (PTM), which can be attributed to the influence of deviatoric stress within the sample chamber. The reversibility of this transformation is confirmed by the recovery of Raman peaks and electrical conductivity upon decompression. Furthermore, the high-temperature and high-pressure electrical conductivity results clearly revealed a negative Clapeyron slope for the hydrogen-disordering transformation in brucite, and the corresponding high P–T phase diagram was established for the first time at pressures up to 7.0 GPa and temperatures up to 873 K, which can be expressed as $P \left(\mathrm{GPa}\right) = 8.664 (\pm 1.511) - 0.008 (\pm 0.002) T \left(\mathrm{K}\right)$. These results provide direct experimental constraints on the high-pressure phase stability and structural phase transition of brucite and offer an important reference for understanding the behavior of other hydroxide minerals under extreme conditions. Full article

Plunger pumps are widely used in high-pressure and high-flow applications and exhibit strong adaptability to different fluid media. In addition to the interaction between the valve and the fluid, a potential coupling effect may exist between the flow characteristics of the pump and the electromagnetic characteristics of the motor. To investigate the electromagnetic–mechanical–hydraulic coupling effect in a motor–pump system, a transient coupled dynamics model integrating electromagnetic fields (EMF), multi-body dynamics (MBD), and computational fluid dynamics (CFD) is developed. The motion of the valve is incorporated into the model through dynamic mesh and user-defined function (UDF) techniques. The different physical models are coupled through torque, speed, force, and displacement. Based on the proposed model, the coupling characteristics of the system are analyzed. The results show that pulsating components associated with the reciprocating frequency appear in both the rotational speed and torque of the motor, resulting in fluctuations of approximately 2.11% in speed and 29.57% in torque. These pulsations are also reflected in the stator current spectrum. In addition, the valve motion at different crank angles and the flow patterns in the pump chamber are analyzed. The electromagnetic characteristics of the motor have a limited influence on the internal flow behavior of the pump. Full article