Search Results (495)

To enhance the passing capacity of the Bailongtan Ship Lock on the Hongshui River, this study focused on the design scheme of its water conveyance system reconstruction and expansion project. A three-dimensional mathematical model meeting the experimental accuracy requirements was established based on the RNG k-ε turbulence model and the Volume of Fluid (VOF) free-surface tracking method. A 1:30 scale ship lock water conveyance system physical model was built and used the independently developed system for hydraulic test monitoring, acquisition, and control. Experimental research on the hydraulic characteristics and shape optimization of the water conveyance system was carried out. The experimental results show that, under the condition of a maximum head difference of 16.0 m between the upstream and downstream of the ship lock, in the design scheme, the flow in the corridor after the filling valve fails to diffuse adequately, forming a high-velocity zone and a significant pressure difference between the inner and outer sides, which poses an operational risk. By optimizing the shape of the corridor after the valve (deepening the bottom end by 2.0 m and adjusting the turning angle from 75° to 70°), the range of the high-velocity zone can be shortened from 3.0 m to 1.5 m. The pressure difference between the inner and outer sides of the corridor at the horizontal turning section is reduced by 19.2% from 5.35 m to 4.32 m of the pressure head at the moment of maximum flow rate, and the velocity in the horizontal section is less than 15 m/s. Physical model tests confirmed these improvements, with mooring forces within safety limits (longitudinal ≤ 32 kN, transverse ≤ 16 kN). The research findings indicate that integrating numerical simulation with physical model testing can effectively mitigate risks in the original design of the ship lock water conveyance system. This approach notably enhances the reliability and safety of the design scheme, as demonstrated by the significant reduction in high-velocity zones and pressure differentials. Moreover, it offers a robust scientific basis and practical technical reference for in-depth hydraulic research and targeted optimization of ship lock water conveyance systems. Full article

End-tidal breath gases originate deep within the lungs, and their composition is an especially accurate reflection of the body’s metabolism and health status. Therefore, accurate collection of end-tidal breath gases is crucial to enhance electronic noses’ performance in breath detection. Regarding this issue, this study proposes a novel electronic nose system and employs a threshold control method based on exhaled gas flow characteristics to design a gas collection module. The module monitors real-time gas flow with a flow meter and integrates solenoid valves to regulate the gas path, enabling automatic collection of end-tidal breath gas. In this way, the design reduces dead space gas contamination and the impact of individual breathing pattern differences. The sensor array is designed to detect the collected gas, and the response chamber is optimized to improve the detection stability. At the same time, the control module realizes automation of the experiment process, including control of the gas path state, signal transmission, and data storage. Finally, the system is used for breath detection. We employ classical machine learning algorithms to classify breath samples from different health conditions with a classification accuracy of more than 90%, which is better than the accuracy achieved in other studies of this type. This is due to the improved quality of the gas we extracted, demonstrating the superiority of our proposed electronic nose system. Full article

As the global demand for sustainable energy grows, hydrogen fuel has become a promising alternative to fossil fuels, particularly in the drone industry. Drones, known for their high mobility and low operational costs, are increasingly utilized in sectors like defense, agriculture, and logistics. However, traditional battery-powered drones are limited by flight duration and recharging times. Hydrogen fuel cells present a viable solution, with effective hydrogen pressure regulation being the key to ensuring their stable operation. This paper presents an innovative valve design for drones, developed to regulate the pressure reduction of high-pressure hydrogen gas from the storage tank to the fuel cell system. The valve incorporates a multi-stage pressure reduction mechanism, optimized to minimize the adverse effects of gas flow. Using a combination of experimental tests and numerical simulations, the study examines hydrogen flow characteristics at various valve openings, focusing on pressure, velocity distribution, and energy consumption. The results demonstrate that narrowing the valve opening improves pressure reduction, effectively controlling hydrogen flow and stabilizing pressure, thereby ensuring proper fuel cell operation. Further analysis reveals that smaller valve openings help reduce turbulence and energy loss, improving flow stability and system efficiency. This research provides valuable insights into hydrogen pressure regulation in drone fuel delivery systems, especially under extreme conditions such as high pressures and large pressure ratios. The findings offer both theoretical and practical guidance for optimizing hydrogen fuel delivery systems in fuel cell-powered drones, contributing to improve energy management and enhance performance in future drone applications. Full article

This study investigates the flow dynamics and damage characteristics of liquid level control valves in direct coal liquefaction processes. The primary failure mechanisms are identified as eccentric jet-induced unilateral wall damage, cavitation erosion, and solid particle erosive wear. A numerical simulation framework was developed to analyze the effects of varying spool angles (72°, 90°, 98°, 105°, and 120°) on flow stability, cavitation dynamics, and erosion patterns. The key findings include the following: A spool angle of 90° achieves the most uniform pressure distribution and minimizes eccentric jet phenomena. Spool geometry modifications exhibit a negligible influence on cavitation characteristics. Reduced wear rates are observed at smaller spool angles (72° and 90°), with the lowest particle-induced erosion occurring at 90°. There is a certain correlation between the particle residence time and the wear of the valve core wall, which is illustrated in the shorter residence times that are correlated with accelerated material degradation. The optimal spool angle of 90° simultaneously mitigates eccentric jet effects, cavitation, and erosive wear. This research provides novel insights for predictive failure analysis and the structural optimization of control valves in high-pressure multi-phase flow systems. Full article

An increasing demand can be observed in ship-to-ship (STS) liquefied natural gas (LNG) bunkering operations, and the failures involved may lead to considerable casualties or environmental damage. For this purpose, a comprehensive methodology is proposed in this study to identify and assess these failure modes. In detail, the STS LNG bunkering process is first decomposed to develop a hierarchical structure according to systems-theoretic process analysis (STPA), the results of which serve to identify potential failure modes and their causes. Then, all the failure modes are evaluated by experts in terms of occurrence, severity, and detectability to develop a fuzzy confidential matrix, which is then transferred as an explicit confidential matrix to be weighted and normalized. Finally, the risk levels of these failure modes are analyzed by relative closeness obtained from the technique for order preference by similarity to an ideal solution (TOPSIS). This study determines nine failure modes, all of which are ranked in terms of risk level. “High pressure in vapor return line”, and “High flow rate and leakage of LNG” are determined as the top two failure modes, with risk closeness values of 0.5791 and 0.5728, respectively. “Power failure for emergency valves” is ranked as the last one, with the risk closeness value being 0.5444. Finally, suggestions are proposed according to bunkering operation guidelines to prevent or control these failure modes. Full article

Laver fluffy is an indispensable link in the processing of laver products. After fluffing, the laver acquires an appealing color, which is conducive to better marketability. During the primary mechanical processing of laver, a valve capable of rapid opening and closing is required to ensure that the laver’s surface becomes fluffy and lustrous post-processing. However, valve products that can meet the specific requirements of laver fluffing are scarce. This study proposes a novel principle for a high-speed switching control valve. This valve can quickly turn on or cut off the high-pressure gas path during laver processing while also taking into account the response speed and service life. The structure and principle of the new control valve were introduced. Different flow field models in the valve were designed, and their flow characteristics and flow field performance under various schemes were compared and discussed by using Fluent. Subsequently, an optimized control valve structure model was proposed. Based on this, a strength analysis of the control valve was conducted via fluid–structure interaction, revealing the response characteristics of the valve under the working state. The results indicate that, when different cone angles and bell shapes were selected for the upper chamber inlet of the control valve, the number and intensity of vortices in the upper chamber can be reduced. The height of the upper chamber affected the formation of the throttle between the top and bottom surfaces of the upper chamber. When the height of the upper chamber was 32 mm, the energy loss in the upper chamber remains basically stable. Simultaneously changing the inlet shape and height of the upper chamber can effectively prevent the throttle formed by the height of the upper chamber, which was conducive to increasing the valve outlet flow rate. Through the analysis of the flow field with different valve chamber structures, the improved control valve adopted the bell-shaped inlet, with an upper chamber height of 32 mm and curved transition for the internal flow channel. Compared to the original fluid domain, when the opening was 100%, the outlet flow rate of the 10° conical tube and bell-shaped inlet increased by 12.77% and 12.59%, respectively. The outlet flow rate at the curved transition position rose by 15.35%, and the outlet flow of the improved control valve increased by 32.70%. When the control valve was operating under a preload pressure of 1 MPa, at 20% opening, the maximum equivalent stress of the valve body was 52.51 MPa, and the total deformation was 12.56 microns. When the preload pressure exceeded 1.5 MPa, the equivalent stress and total deformation of the control valve body and T-shaped valve stem exhibited an upward trend with further increases in the preload pressure. Full article

To predict the variation in the displacement position of hydraulic cylinder piston rods, a neural network model is proposed to enhance the displacement control accuracy of hydraulic cylinders. The innovation of this paper is that by calculating the compressibility-induced flow loss of hydraulic fluid, mathematical models for both the internal and external leakage of hydraulic cylinders are established, identifying seven primary factors influencing piston rod displacement. Because there are many influencing factors and complex parameters different from traditional backpropagation (BP) neural network used in previous studies, this paper innovatively proposes a three-layer BP neural network ensemble model for predicting input–output characteristic curves of hydraulic cylinders. In the process of model improvement, a nonlinear adaptive decreasing weight mechanism is introduced to improve the optimization accuracy of the algorithm, facilitating the search for optimal solutions. The most reasonable weight and bias parameters are determined via the iterative training and testing of each BP neural network layer. This model enables the real-time prediction of piston rod displacement output curves after a specified time interval based on external input parameters. The predicted time is utilized to compensate for the response delays caused by directional valve switching and hydraulic fluid buffering, thereby enabling proactive displacement prediction. Validation results demonstrate that the maximum predicted displacement error is reduced to 0.5491 µm, with the model’s maximum runtime being 27.82 ms. The maximum allowable time allocated for directional valve switching and fluid buffering in the hydraulic system is extended to 74.57 ms, achieving the objective of enhancing both displacement control accuracy and operational efficiency. Full article

Through hydraulic control principles, numerical simulation and indoor testing, the opening principle of a toe-end sliding sleeve with a time delay mechanism is explained. Conventional toe-end sliding sleeve in shale oil wells have problems with premature opening and a failure to open, which means they cannot ensure the whole-well pressure test process and can cause serious economic losses to the oil and gas industry. In order to solve the above problems, a new type of optimal design for toe-end sliding sleeve with a 30 min delayed opening is proposed. In this paper, based on the principle of hydraulic flow, ABAQUS 2022 numerical simulation software was used to study the influence of different states and the same hydraulic pressure on its internal stress–strain value. A qualitative study of the delayed-opening function was carried out using a pressurized pump unit. In addition, principle tests under different operating parameters were designed to quantitatively analyze the pin shear situation and the delayed opening time of the toe-end sliding sleeve when the tool was fitted with different numbers of pins and when the delay valve was fitted. In addition, the simulation results of the hydraulic fluid’s flow inside the time delay mechanism with different nozzle diameters were compared with the theoretical values, which showed that the hydraulic fluid’s flow rate inside the mechanism increased with the enlargement of the nozzle diameter, and the optimal nozzle diameter was 0.56 mm. The indoor test showed that when the tool was retrofitted with a time delay mechanism, installing six pins was the optimal combination. The field application of the slip-on was able to satisfy an opening time delay of 28.3 with a relative error of only 5.67%. These results complement the research on toe-end sliding sleeve and provide ideas for the optimization of toe-end slipcovers incorporating a time delay mechanism. Full article

The elastic valve plate and guide flow disc are key components that influence parameters such as opening and pressure difference of pilot-relief valve, which are also the core components enabling continuous damping adjustment in valve-controlled continuously variable dampers. Based on deformation characteristics of elastic valve plate and various structural types of guide flow disc, this paper reveals the impact of structural types of guide flow disc and design parameters of elastic valve plate on the performance of pilot-relief valve and obtains the relationship curves between opening pressure, pressure difference and opening of relief valve versus structural types and the angle, width and the number of arc plates of elastic valve plate. It shows that the pressure difference of the relief valve reaches maximum with min angle, max width, most arc plates and irregular-shaped type, and the opening reaches maximum with max angle, min width, fewest plates and round hole type. By adjusting structural types of guide flow disc and design parameters of elastic valve plate, the pressure difference and opening of the relief valve can be precisely controlled, providing theoretical support for the precise design of pilot-relief valve and the optimization of damping characteristics. Full article

The thrust system, an important subsystem of a tunnel boring machine (TBM), primarily provides thrust force and adjusts TBM’s attitude in real time. In the tunneling process, only controlling the thrust speed causes pressure oscillations, increases soil deformation, and leads to surface subsidence or upheaval. Conversely, solely relying on pressure control causes fluctuations in speed, making it difficult to ensure that the deviation between the designed tunneling axis (DTA) and the actual tunneling axis (ATA) remains within the permissible range. Due to the increase in geological complexity and higher construction quality standards, primarily relying on single-mode speed or pressure control has become inadequate to meet operational demands. Therefore, to realize higher safety and precise trajectory tracking, it is necessary to ensure speed and pressure compound control for thrust systems. This paper proposes a novel adaptive sliding mode control (ASMC) strategy for thrust systems, which is composed of a proportional pressure relief valve (PPRV) and a proportional flow control valve (PFCV). Firstly, PPRV and PFCV are modeled as a second-order system and an ASMC is employed to control the pressure and speed. Next, to assess the performance of the ASMC controller, simulation experiments were conducted under various conditions, including speed regulation, sudden changed load, and disturbed load. The simulation results indicate that compared to the Proportion–Integral–Differential (PID) controller, the ASMC controller shows almost no overshoot in speed and pressure control during the initial stages, with the response time reduced by approximately 70%. During speed regulation process and sudden changed load process, the response time for both speed and pressure control is shortened by about 80%. In the disturbed load process, the ASMC controller maintains pressure stability. In conclusion, the ASMC controller significantly improves the response speed and stability of the thrust system, exhibiting better control performance under various operating conditions. Full article

Microfluidics is a technology that manipulates liquids on the scales ranging from microliters to femtoliters. Such low volumes require precise control over pressures that drive their flow into the microfluidic chips. This article describes a custom-built pressure controller for driving microfluidic chips. The pressure controller features piezoelectrically controlled pressure regulation valves. As an open-source system, it offers high customizability and allows users to modify almost every aspect. The cost is roughly a third of what similar, alternative, commercially available piezoelectrically controlled pressure regulators could be purchased for. The measured output pressure values of the device vary less than 0.7% from the device’s reported pressure values when the requested pressure is between −380 and 380 mbar. Importantly, the output pressure the device creates fluctuates only ±0.2 mbar when the pressure is cycled between 10 and 500 mbar. The pressure reading accuracy and stability validation suggest that the device is highly feasible for many advanced (low-pressure) microfluidic applications. Here, we compare the main features of our device to commercially and non-commercially available alternatives and further demonstrate the device’s performance and accessibility in successful microfluidic hydrodynamic focusing (MHF)-based synthesis of large unilamellar vesicles (LUVs). Full article

In agricultural plant protection, pressure fluctuations during targeted spraying are a key factor affecting spray quality. To address the issue of pressure fluctuations in the system pipeline caused by the inconsistent opening and closing of nozzles during targeted spraying, this study proposes a pressure-stabilizing device based on programmable logic control (PLC). To verify the feasibility of the system, experimental tests were conducted to assess pressure fluctuations, spraying volume, and droplet characteristics. The tests were performed at three different pressure settings: 0.3 MPa, 0.4 MPa, and 0.5 MPa, and the effects of opening and closing between one and five nozzles on system performance were examined. The results revealed that as the Δn (defined as the change in nozzle number) increased during target application, the pressure fluctuation also increased, reaching up to −0.008 MPa. Conversely, as the number of closed nozzles increased, the pressure fluctuation grew, reaching up to +0.006 MPa. Due to the frequent opening and closing of the solenoid valve, pressure fluctuations occur in the pipeline, with the duration of these fluctuations closely matching the solenoid valve’s response time of 60 ms. A model correlating the Δn with the nozzle flow rate was developed, showing a strong fit. This indicates a significant correlation between the Δn and flow rate, while the nozzle flow rate is minimally affected by pressure fluctuations in the system. An analysis using a laser particle size analyzer revealed that the droplet characteristics of the targeted spraying exhibited good stability. In conclusion, the system demonstrated excellent spraying performance during targeted spraying operations. The results of this study offer valuable insights for the design and optimization of targeted spraying and provide support for advancements in precision spraying. Full article

A versatile and modular microfluidic system for cell co-culture has been developed. Microfluidic chips, each featuring dual compartments separated by a porous membrane, have been fabricated and assembled within the system to facilitate fluidic interconnection and cell–cell communication through the chip assembly. A set of fluidic valves has been successfully integrated to regulate the flow through the chip assembly. The system allows for chip assembly in various arrangements, including in parallel, in series, and complex connections. Individual chips can be interconnected or disconnected within the system at any time. Moreover, the spatial order and orientation of the chips can be adjusted as needed, enabling the study of different cell–cell arrangements and the impact of the presence or absence of specific cell types. The utility of the system has been evaluated by culturing and interconnecting multi-monolayers of intestinal epithelial cells as a model of the complex cellular system. Epithelial monolayers were grown in multiple chips and interconnected in various configurations. The transepithelial electrical resistance and permeability profiles were investigated in detail for these configurations upon treatment of the cells with dextran sulfate sodium. Immune cells were stimulated through the epithelial layers and the expression of inflammatory cytokines was detected. This miniaturized platform offers controlled conditions for co-culturing key cellular components and assessing potential therapeutic agents in a physiologically relevant setting. Full article

Fluid dynamic noise produced by eddy disturbances and friction along pipe walls poses a significant challenge in natural gas transmission and distribution stations. (K)TS control valves are widely used in natural gas transmission and distribution stations across Southwest China and are among the primary sources of noise in these facilities. In this study, a 3D geometric model of the (K)TS valve was developed, and the gas flow characteristics were simulated to analyze the gas flow field and sound field within the valve under varying pipeline flow velocities, outlet pressures, and valve openings. The results demonstrate that accurate calculations of the 3D valve model can be achieved with a grid cell size of 3.6 mm and a boundary layer set to 3. The noise-generating regions of the valve are concentrated around the throttle port, valve chamber, and valve inlet. The primary factors contributing to the aerodynamic noise include high gas flow velocity gradients, intense turbulence, rapid turbulent energy dissipation, and vortex formation and shedding within the valve. An increase in inlet flow velocity intensifies turbulence and energy dissipation inside the valve, while valve opening primarily influences the size of vortex rings in the valve chamber and throttle outlet. In contrast, outlet pressure exerts a relatively weak effect on the flow field characteristics within the valve. Under varying operating conditions, the noise directivity distribution remains consistent, exhibiting symmetrical patterns along the central axis of the flow channel and forming six-leaf or four-leaf flower shapes. As the distance from the monitoring point to the valve increases, noise propagation becomes more concentrated in the vertical direction of the valve. These findings provide a theoretical basis for understanding the mechanisms of aerodynamic noise generation within (K)TS control valves during natural gas transmission, and can also offer guidance for designing noise reduction solutions for valves. Full article

The article is devoted to designing novel multivariable robust μ-control of an open-circuit axial piston pump. In contrast with classical solutions of displacement volume control, in our case, the hydro-mechanical controller (by pressure, flow rate, or power) is replaced by an electro-hydraulic proportional valve which receives a control signal from an industrial microcontroller. The valve is used as the actuator of the pump swash plate. The pump swash plate swivel angle determines the displacement volume and the flow rate of the pump. The μ-controller design is performed on the basis of a one-input, two-output model with multiplicative output uncertainty. This model is estimated and validated from experimental data at various loads by multivariable identification. The designed control system achieves robust stability and robust performance for the wide working mode of an axial piston pump. To conduct this experimental study, the authors have developed a laboratory test bench, enabling a real-time function of the control system via USB/CAN communication. The designed controller is implemented in a rapid prototyping system, and real-time experiments are performed. They show the advantages of μ-control and confirm the possibility of its implementation in the case of the real-time control of an axial piston pump. Full article