Pneumatic Valve Research Articles

Research on an Off-Chip Microvalve for Pneumatic Control in Microfluidic Chips

A compact, rapid, and portable off-chip pneumatic control valve is significant for the miniaturization and integration of external pneumatic systems for microfluidic chips. In this work, an off-chip microvalve with a high-speed electromagnetic switch actuator and a polydimethylsiloxane (PDMS) material valve body has been designed to be easily encapsulated, simulated using MATLAB/Simulink software, and tested in a micromixer. Multi-physical coupling mathematical models are developed based on the elastic deformation force of the valve membrane, the driving force of the valve core, and the fluid force in the microchannel. Two single microvalves are used to form a three-way microvalve, which can control the air pressure in a pneumatic microchannel on the microfluidic chip. The relationship between the flow–duty cycle, the flow–pressure difference of the single electromagnetic microvalve, and the load pressure of the three-way microvalve is simulated and analyzed. Sample mixing performance controlled by the proposed off-chip three-way microvalve was tested to evaluate the pneumatic control capability, and the results show that the undertaking can fully satisfy the needs of a pneumatic microfluidic chip for most applications.

Single-cell sorting using integrated pneumatic valve droplet microfluidic chip

Single-cell analysis and sorting have been increasingly prevalent in scientific study and industry in recent years. Droplet-based microfluidic systems are significant tools for single cell separation due to the advantages of high-throughput screening flux and relatively simple chip manufacturing. Herein, this work integrated single-cell droplet generation, incubation, and sorting functions into a single microfluidic chip using pneumatic microvalve for single-cell screening of hybridoma cells. The chip realized the generation, storage, incubation, and assay sorting of droplets in order by adjusting the switch of the microvalve. Numerical methods were used to simulate the effects of membrane size and pressure on valve deformation. Incubation results showed that fluorescent signals were generated in the droplets containing both hybridoma cells and microspheres under the control of pneumatic microvalves. In addition, the purity of target droplets was increased from 4.87% before sorting to 89.70% after sorting using fluorescence-activated droplet sorting platform, demonstrating the feasibility of the integrated chip with a pneumatic valve for single-cell screening. The integrated chip is proved to be operated efficiently with minimum cell loss and human labor through reducing the risk of droplet fusion and facilitating the development of automated devices. So, the present study provides an integrated design for microdroplet-based single-cell sorting with various applications, such as single-cell sequencing, antibody screening, and directed evolutionary studies.

Classification between Normal and Cancerous Human Urothelial Cells by Using Micro-Dimensional Electrochemical Impedance Spectroscopy Combined with Machine Learning.

Although the high incidence and recurrence rates of urothelial cancer of the bladder (UCB) are heavy burdens, a noninvasive tool for effectively detecting UCB as an alternative to voided urine cytology, which has low sensitivity, is yet to be reported. Herein, we propose an intelligent discrimination method between normal (SV-HUC-1) and cancerous (TCCSUP) urothelial cells by using a combination of micro-dimensional electrochemical impedance spectroscopy (µEIS) with machine learning (ML) for a noninvasive and high-accuracy UCB diagnostic tool. We developed a unique valved flow cytometry, equipped with a pneumatic valve to increase sensitivity without cell clogging. Since contact between a cell and electrodes is tight with a high volume fraction, the electric field can be effectively confined to the cell. This enables the proposed sensor to highly discriminate different cell types at frequencies of 10, 50, 100, 500 kHz, and 1 MHz. A total of 236 impedance spectra were applied to six ML models, and systematic comparisons of the ML models were carried out. The hyperparameters were estimated by conducting a grid search or Bayesian optimization. Among the ML models, random forest strongly discriminated between SV-HUC-1 and TCCSUP, with an accuracy of 91.7%, sensitivity of 92.9%, precision of 92.9%, specificity of 90%, and F1-score of 93.8%.

A Magnetorheological Elastomer‐Based Proportional Valve for Soft Pneumatic Actuators

The interest in soft pneumatic actuators has been growing rapidly in robotics, owing to the contact adaptability with the material softness. However, these actuators are mostly controlled by rigid electronic pneumatic valves, which can hardly be integrated into the robot itself, limiting its mobility and adaptability. Recent advances in soft or electronics‐free valve designs provide the potential to achieve an integrated soft robotic system with reduced weight and rigidity. Nevertheless, the challenge in valve response remains open. To enable dynamic control of a soft pneumatic actuator (SPA), a fast‐response proportional valve is needed. Herein, the potential of Ecoflex‐based magnetorheological elastomer (MRE) membrane to create a proportional valve that can be used in the control of a soft robot made from the same silicone material is explored. Experimental characterization shows that the proposed MRE valve (30 mm × 30 mm × 15 mm, 30 grams) can hold pressure up to 41.3 kPa and regulate the airflow in an analog manner. The valve is used to perform closed‐loop proportional–integral–differential (PID) control with 50 Hz on a SPA and is able to control the pressure within the actuator chamber with a root‐mean‐square error of 0.05 kPa.

Selection of the Optimal Parameters of a Pneumatic Three-line Direct-acting Pressure Reducing Valve

Reducing pneumatic valves, which are part of modern pneumatic control systems, are widely used in the automation of production and technological processes in various fields of technology. The efficiency of using pressure reducing valves depends on their parameters and characteristics. To select the optimal parameters of pressure reducing valves, various methods are used based on the search for the minimum of the target (target or criteria) function.The object of study is a three-line direct-acting pressure reducing valve, which ensures the determination of its optimal parameters. To calculate the optimal parameters of the pressure reducing valve, the method of orthogonal experimental design was applied. The main advantage of this method is that in this case all variables are varied simultaneously.The article presents the design features of a three-line direct-acting pressure reducing valve.The developed mathematical model of a pressure reducing valve is presented, which is a system of equations for a three-line direct-acting pressure reducing valve, which should be used to select the optimal parameters of the pressure reducing valve.To calculate the optimal parameters of the pressure reducing valve, the method of orthogonal experimental design was used. As an optimality criterion, the integral criterion of the squared error of the transient process, the change in the pressure level in the outlet line of the valve, was chosen.The optimal parameters of the pressure reducing valve are found, and transient processes of pressure change in the outlet line of the pressure reducing valve are calculated. The main requirements for optimization and selection of the optimal parameters of pressure reducing valves are formulated. A comparison of the transient processes of the outlet pressure before and after optimization is given.Based on the results of the work, the following conclusions were drawn:From the obtained comparative results of the transient processes of the level of outlet pressure in the outlet of the pressure reducing valve before and after optimization, it was found that after optimization the pressure reducing valve has a faster response.The speed has been increased from 0.35 s to 0.27 s, that is, the speed has increased by 1.30 times.The transient overshoot is less than 5%, and the static error is reduced by 1.9% and is completely eliminated.

Design and Development of Pneumatic Sheet Metal Cutting Machine

A Pneumatic sheet metal cutting machine, is a mechanism designed to cut metal sheets at a quick pace, based on the inputs given by the operator, using a switch. The machine consists of a cutter blade system, a double acting pneumatic cylinder held over the cutter blade system, an air compressor, a pneumatic valve to regulate the air flow to the pneumatic cylinder from the compressor, and a frame to hold the machine in position. Cutting and shearing technology used nowadays, includes laser cutting, hydraulic cutters, among others. These machines are costly, with expensive maintenance. Small and medium scale industries cannot tend to afford this technology. Currently basic sheet metal cutting operations are incorporated in such industries including basic handheld sheet cutters. This is not accurate in terms of the dimensions of the final output and poses safety hazards to the operator too. Thus, the novelty of this machine is that it provides an automated system to cut aluminium sheet metal, while making sure that the system is compact and portable, which has otherwise not been implemented in industries. Pneumatic sheet metal cutters find a tremendous scope in such industries owing to their simple and easy working, low cost and ensured safety with a good degree of dimensional accuracy. The main aim of this study is to research and innovate a safe and efficient way to cut aluminium sheets at a fast and regular pace, as compared to manual cutting, using a pneumatic system.

A New Positioning Strategy Based on Parameter Tuning and Optimal Control Technique for Pneumatic Control Valve

To improve the accuracy, rapidity, and versatility of pneumatic control valves, mechanism modeling, and optimization analysis on pneumatic actuators were carried out, and then a new positioning strategy based on parameter tuning and optimal control technique was proposed consequently. Firstly, a dynamic model of valve position based on optimal control under constraint conditions was established, and the characteristic parameters of valve position motion were determined. Then, the adaptive processing of switching points was introduced into the optimal control strategy to improve the versatility of the control. Finally, according to different control strategy partitions, the interactive control of the piezoelectric air switch by fully open control and PWM improves the control accuracy of the algorithm. The experimental analysis of the control effect with other brand positioners shows that the proposed control strategy shortens the system adjustment time, improves the accuracy of valve position, and avoids the overshoot.

Design of FOPID Controller for Pneumatic Control Valve Based on Improved BBO Algorithm.

Aiming at the problems of nonlinearity and inaccuracy in the model of the pneumatic control valve position in the industrial control process, a valve position control method based on a fractional-order PID controller is proposed. The working principle of the pneumatic control valve is analyzed, and its mathematical model is established. In order to improve the accuracy of the model, an improved biogeography-based optimization algorithm is proposed to tune the parameters of the fractional-order PID controller in view of the wide range and high complexity of the fractional-order PID controller. The initialization of the chaotic graph, the adjustment of the migration model, and the improvement of the migration operator and the mutation operator are introduced to improve the algorithm optimization ability, which is used for the model identification of the control valve control system. The simulation and experimental results clearly show that, compared with the integer-order PID controller, the designed fractional-order PID controller has faster response speed and control accuracy, which can better meet the requirements of pneumatic control valve position control.

Порівняння роботи підсистем прогнозування в автоматизованій системі керування випарним апаратом

Мета дослідження — обґрунтування методів регулювання тиску пари у випарному апараті з підсистемою прогнозування, що дозволить спрогнозувати поведінку системи та дослідити вплив кількості часових інтервалів алгоритму прогнозування на точність прогнозу роботи випарної станції. Розроблено систему обміну даними між рівнем технологічного процесу і рівнем виробництва. Досліджується робота випарної установки з підсистемою прогнозування регулювання тиску пари. У схемі автоматизації регулювання тиску пари як датчик використовуються перетворювачі тиску PC-28. Виконавчими механізмами служать пневматичні сідельні клапани з вбудованим дроселем та електро-пневмоперетво­рювачем. Використання нейронечітких регуляторів відбувається лише в окремих специфічних випадках інтелектуального керування процесом випаровування, відсутні дані порівняння застосування інтелектуальних регуляторів з класичними, можливості комбінування роботи кількох типів інтелектуальних регуляторів, а також чітких засобів прогнозування їх роботи. Тому у даній роботі використано метод прогнозування для порівняння методів регулювання тиску пари в апараті, що дозволило спрогнозувати поведінку системи при формуванні керування та вивести готовий прогноз на екран оператора і, таким чином, підвищити ефективність роботи випарної станції. Зібрано статистичні дані поведінки контурів системи автоматизації у різних режимах роботи з використанням інтелектуальних та класичних регуляторів і побудовано модель прогнозування роботи випарної станції методом локальної тенденції та модифіковано алгоритм прогнозування. Перевага даного методу — легка і швидка його реалізація, яка не потребує великих економічних та енергетичних затрат. Побудовано модель прогнозування роботи випарної станції методом локальної тенденції та розроблено алгоритм прогнозування. Також оцінено точність отриманої моделі прогнозування: 97 % — для ПІД-ре­гулятора, 97 % — для нейронечіткого регулятора та 96,5 % — для нейромережевого при використанні девʼяти інтервалів, що вище за точність при використанні шести інтервалів. Запропонована модель для прогнозування роботи випарної станції характеризується високою точністю в цілому, але під час коливань у перехідному процесі виникає несуттєве запізнення їх прогнозування. Точність роботи даної моделі напряму залежить від збільшення кількості часових інтервалів при розробці алгоритму прогнозування.

Redundant Robot with Pneumatic Artificial Muscles for Rehabilitation Works Using Iterative Learning Control

This study aims to develop a multi-functional robotic arm with a multi-degree of freedom using a pneumatic artificial muscle cylinder as the main actuator, with a wearable function. While wearing the robotic arm, it has four degrees of freedom and can be used as an upper limb rehabilitation aid to perform rehabilitation exercise tasks. The rotating axes are driven by pneumatic artificial muscle cylinders to ensure the safety and flexibility of the robot interaction. By integrating multiple pneumatic control valves and sensors with embedded interface cards, the control of pneumatic artificial muscle cylinders is performed, and the rehabilitation trajectory commands are planned through the kinematics of the robotic arm, and a closed-loop control system is established to enable the robotic arm to achieve the task of rehabilitation trajectory tracking. In the single-axis robotic arm controller experiment, it was found that the LMS-PID is superior to the conventional PID control method. In the control experiment of the robotic arm under the multi-axis recovery trajectory, the result showed that the training of drawing a circle on the wall could be successfully planned. In the multi-axis robotic tracking experiment under the rehabilitation trajectory, the result showed that the RMSE of the tracking trajectory decreased to 0.2444 and 0.2853. In the robotic arm joining/loading experiment, it was shown that the method of this study can withstand some loading effects. Moreover, this study introduces iterative learning control to improve the non-linear compensation and phase lag problems of the PID controller so that the robot arm can have a certain tracking accuracy under the round-trip robust trajectory.

Multi-Resin Masked Stereolithography (MSLA) 3D Printing for Rapid and Inexpensive Prototyping of Microfluidic Chips with Integrated Functional Components.

Stereolithography based 3D printing of microfluidics for prototyping has gained a lot of attention due to several advantages such as fast production, cost-effectiveness, and versatility over traditional photolithography-based microfabrication techniques. However, existing consumer focused SLA 3D printers struggle to fabricate functional microfluidic devices due to several challenges associated with micron-scale 3D printing. Here, we explore the origins and mechanism of the associated failure modes followed by presenting guidelines to overcome these challenges. The prescribed method works completely with existing consumer class inexpensive SLA printers without any modifications to reliably print PDMS cast microfluidic channels with channel sizes as low as ~75 μm and embedded channels with channel sizes as low ~200 μm. We developed a custom multi-resin formulation by incorporating Polyethylene glycol diacrylate (PEGDA) and Ethylene glycol polyether acrylate (EGPEA) as the monomer units to achieve micron sized printed features with tunable mechanical and optical properties. By incorporating multiple resins with different mechanical properties, we were able to achieve spatial control over the stiffness of the cured resin enabling us to incorporate both flexible and rigid components within a single 3D printed microfluidic chip. We demonstrate the utility of this technique by 3D printing an integrated pressure-actuated pneumatic valve (with flexible cured resin) in an otherwise rigid and clear microfluidic device that can be fabricated in a one-step process from a single CAD file. We also demonstrate the utility of this technique by integrating a fully functional finger-actuated microfluidic pump. The versatility and accessibility of the demonstrated fabrication method have the potential to reduce our reliance on expensive and time-consuming photolithographic techniques for microfluidic chip fabrication and thus drastically lowering our barrier to entry in microfluidics research.

DYNAMICS OF PNEUMATIC DRIVE. LECTURE CYCLE.MATHEMATICAL MODEL OF THE SERVO PNEUMATIC ACTUATOR

The paper considers the basic concepts of a mathematical model. The connection between the model and reality and its place and relevance in the modern world is shown. The developed mathematical model of a servo pneumatic device, which includes an actuator and a proportional or discrete pneumatic valve, is presented. The basic equations describing the dynamics of the servo pneumatic device, boundary and initial conditions are given, which make it possible to analyze the stability of the drive. A non-linear object-oriented computer model of a pneumatic servo device is presented. The model is built in the form of block diagrams of equations that describe the relationship between the original physical quantities. The influence of the nature of the inductance of the electromagnet coil on the dynamic properties of the system is shown. The developed method for identifying the transfer function of pneumatic devices and its application in the preparation of mathematical models is presented. A technique for studying the stability of pneumatic systems has been created, based on establishing an unambiguous relationship between the experimentally obtained frequency characteristics of the pneumatic apparatus included in the system and the type of its transfer function. The form of transfer functions for the pneumatic devices under consideration is obtained. For the proportional pneumatic valves presented in the work, the quality indicators of transient processes in the time domain are formulated and determined, and the phase and amplitude margins are found. The criteria for the performance of pneumatic systems are formulated. The ratios for determining the described criteria are given. The boundaries of the operability of systems with a pneumatic drive have been established. The scientific novelty of the results presented in the work is that a non-linear object-oriented computer model of a servo pneumatic device has been created, unlike the existing ones, it is built in the form of block diagrams of equations that describe the relationship between the initial physical quantities, and has the principle of modularity. The model includes the transfer function of the control devices obtained using the developed method for identifying the parameters of the transfer function. This work is based and is implemented as a course of lectures of the course “Dynamics of Pneumatic drive”, is red by the author at the Bauman Moscow State Technical University at the Department of “Hydromechanics, Hydraulic Machines and Hydropneumoautomatics” (E10), as part of the preparation of masters in the specialty 05.04.13 – Hydraulic machines and hydropneumatic drives.

Development and evaluation of an automated solvent-assisted flavour evaporation (aSAFE)

Artefact-avoiding isolation of the volatiles from foods is a crucial step before analysis of odour-active compounds by gas chromatography (GC). In the past 20 years, solvent extraction followed by solvent-assisted flavour evaporation (SAFE) has become the standard approach, particularly prior to GC–olfactometry. The manual valve of the SAFE equipment, however, leads to suboptimal yields and the risk of a contamination of the volatile isolate with non-volatiles. We thus developed an automated SAFE (aSAFE) approach by replacing the manual valve with an electronically controlled pneumatic valve. The aSAFE provides clearly higher yields than the manual SAFE (mSAFE), notably from extracts high in lipids and for odorants with comparably high boiling points. Additionally, aSAFE substantially reduces the risk of non-volatiles being transferred to the volatile isolate. Full automatisation is possible by combining the aSAFE approach with an automated liquid nitrogen refill system as well as an endpoint recognition and shut-off system.

DYNAMICS OF PNEUMATIC DRIVE. LECTURE CYCLE.MATHEMATICAL MODEL OF THE SERVO PNEUMATIC ACTUATOR

The paper considers the basic concepts of a mathematical model. The connection between the model and reality and its place and relevance in the modern world is shown. The developed mathematical model of a servo pneumatic device, which includes an actuator and a proportional or discrete pneumatic valve, is presented. The basic equations describing the dynamics of the servo pneumatic device, boundary and initial conditions are given, which make it possible to analyze the stability of the drive. A non-linear object-oriented computer model of a pneumatic servo device is presented. The model is built in the form of block diagrams of equations that describe the relationship between the original physical quantities. The influence of the nature of the inductance of the electromagnet coil on the dynamic properties of the system is shown. The developed method for identifying the transfer function of pneumatic devices and its application in the preparation of mathematical models is presented. A technique for studying the stability of pneumatic systems has been created, based on establishing an unambiguous relationship between the experimentally obtained frequency characteristics of the pneumatic apparatus included in the system and the type of its transfer function. The form of transfer functions for the pneumatic devices under consideration is obtained. For the proportional pneumatic valves presented in the work, the quality indicators of transient processes in the time domain are formulated and determined, and the phase and amplitude margins are found. The criteria for the performance of pneumatic systems are formulated. The ratios for determining the described criteria are given. The boundaries of the operability of systems with a pneumatic drive have been established. The scientific novelty of the results presented in the work is that a non-linear object-oriented computer model of a servo pneumatic device has been created, unlike the existing ones, it is built in the form of block diagrams of equations that describe the elationship between the initial physical quantities, and has the principle of modularity. The model includes the transfer function of the control devices obtained using the developed method for identifying the parameters of the transfer function. This work is based and is implemented as a course of lectures of the course “Dynamics of Pneumatic drive”, is red by the author at the Bauman Moscow State Technical University at the Department of “Hydromechanics, Hydraulic Machines and Hydropneumoautomatics” (E10), as part of the preparation of masters in the specialty 05.04.13 – Hydraulic machines and hydropneumatic drives.

A deep learning based system for real-time detection and sorting of earthworm cocoons

Vermicompost, created by earthworms after eating and digesting organic waste, plays an important role as an organic fertiliser in sustainable agriculture. In this study, a deep learning-based smart system was developed to separate earthworm cocoons used in the production of vermicompost from the compost and return it to production. In the first stage of the study, a dataset containing 1000 images of cocoons was created. The cocoons in each image were labeled and training was performed using a deep learning architecture, one-stage and two-stage models. The models were trained over 2000 epochs with a learning rate of 0.01. From the experimental results, faster R-CNN with ResNet50-FPN model detected the earthworm cocoons better compared to other models. The best performance was obtained by this model with an average precision (AP) of 0.89. In the other stage of the study, the cocoons detected by the software were separated from the compost using a specially designed conveyor belt system. In this process, the detected cocoons are separated from the compost using 10 pneumatic valves that spray air at the separation point. The study is the first of its kind that enables earthworm cocoons to be returned to production with the use of a real-time intelligent system. It also contributes to the literature on small object detection using deep learning.

Mechanical anti-lock braking system using pneumatic system and solenoid valve with low cost manufacturing

PurposeThe Purpose of this study is to prove the possibility of developing low cost mechanical anti – lock braking system (ABS) for the passenger’s safety.Design/methodology/approachThe design methodology of the proposed newer mechanical ABS comprises of two units, namely, the braking unit and wheel lock prevention unit. The braking unit actuates the wheel stopping as and when the driver applies the brake, whereas the wheel lock prevention unit initiates wheel release to prevent locking and subsequent slip/skidding. The brake pedal with master cylinder assembly and double-arm cylinder forms the braking unit, brake pad cylinder, movable brake pad, solenoid valve and dynamo forms the wheel lock prevention unit. The dynamo coupled with the rotor energises/de-energises the solenoid values to direct airflow for applying brake and release it, which makes the system less energy-dependent.FindingsThe braking unit aids in vehicle stops, by locking the disc with the brake pad actuated by a double-arm cylinder. The dynamo energises the solenoid valve to activate the brake pad cylinder piston for applying the brake on the disc. Instantaneously, on applying the brake the dynamo de-energises the solenoid to divert the pneumatic flow for retracting the brake pad thereby minimizing the braking torque. The baking torque reduction revives the wheel rotating and prevents slip/skidding.Originality/valueMechanical ABS preventing wheel lock by torque reduction principle is a novel method that has not been evolved so far. The system was designed with repair/replacement of the parts and subcomponents to support higher affordability on safety grounds.

Development of Flexible Deformation Mobile Robot Composed of Multiple Units and Pneumatic Self-Excited Valve

In this study, we developed new bending modules and pneumatic self-excited valves. In a previous study, we developed a planar flexible-deformation mobile robot that combines multiple bending modules. The robot moves by a traveling wave, which is periodically generated by pressurizing air to the bending modules. Further, it can move in every direction by simultaneously combining the two directional traveling waves. However, problems such as air leakage from the bending module that constitutes the moving object and the influence of the moving operation owing to the tubes comprising the flow path were identified. To address these problems, new bending modules have been developed. To address air leak issues, we verified the materials used in the bending modules and developed an injection mechanism. To reduce the number of externally connected tubes, we developed new bending modules that could include multiple internal flow paths. In addition, because the mobile robot moves owing to the generation of traveling waves, it is a low-grade operation. However, this requires multiple solenoid valves and electronic circuits. This is useful if traveling waves can be generated by simply supplying air using a pneumatic self-excited valve. In this study, we developed bending modules with multiple internal channels and a pneumatic self-excited valve that utilizes the snap buckling of leaf springs used in the mobile robot.

A small-volume microcapillary rheometer.

We demonstrate a capillary device used to measure the shear rate-dependent viscosity of microliter scale volumes. Liquid samples are driven pneumatically through a microcapillary and partially fill a larger glass capillary. The glass capillary is mounted on an optical linear sensor to track the air-liquid meniscus in real time and trigger the reversal of flow direction by switching a pneumatic valve. Each transit provides a volumetric flow rate measurement, which is used with the pressure drop to determine viscosity as a function of shear rate. A given sample of at least 50 μL can be measured over at least 2 to 3 decades in shear rate, in the range of 10 to 105 s-1, and be essentially fully recovered. Validation by comparison to reference measurements is performed using samples of Newtonian and non-Newtonian fluid, with viscosity ranging from 1 to 100 mPa s. The range of operation and uncertainty arising from instrumentation, meniscus effects, and inertial effects are discussed. The performance of this rheometer is advantageous, especially for use and reuse of small volumes.

Numerical and Experimental Investigation of the Conjugate Heat Transfer for a High-Pressure Pneumatic Control Valve Assembly.

This paper uses heat transfer experiments and computational fluid dynamics (CFD) simulations to investigate the conjugate heat transfer (CHT) in a high-pressure pneumatic control valve assembly. A heat transfer test rig was constructed, and time–temperature histories of five test points placed on the valve assembly’s outer surface were recorded for study validation. The Unsteady Reynolds-Averaged Navier–Stokes (URANS) CFD methods with the standard k-ε turbulence closure equations were adopted in the numerical computations. Polyhedral grids were used; time step and mesh convergence studies were conducted. Simulated and measured temperatures profile comparisons revealed a good agreement. The CHT results obtained from CFD showed huge velocity fields downstream of the valve throat and the vent hole. The airflow through the valve was icy, mainly in the supersonic flow areas. Low temperatures below 273.15 K were recorded on the internal and external walls of the valve assembly. The consistency of the measured data with the numerical results demonstrates the effectiveness of polyhedral grids in exploring the CHT using CFD methods. The local entropy production rate analysis revealed that irreversibility is mainly due to viscous dissipation. The current CHT investigation provides a potential basis for thermostress analysis and optimization.

Measurement of the mass-flow-rate characterization parameters of high-pressure pneumatic servo slide valves

The mass-flow-rate characteristics of high-pressure pneumatic servo valves (HPSVs) have an important effect on the dynamic performance of high-pressure servo systems. However, these characteristics are difficult to obtain by theoretical calculations and flowmeter measurements owing to the compressibility of high-pressure gas. In this paper, a new measurement method of the mass-flow-rate characterization parameters of HPSVs is proposed based on the principle of the series connection sonic discharge of valve orifices. The effective cross-sectional area and critical pressure ratio of the servo valve orifices can be accurately and efficiently determined by connecting two valve orifices in series and exchanging the flow sequence of the two valve orifices. The two assumptions including the sonic and adiabatic discharge of the proposed measurement method were verified. A comparison between the test and simulation data showed that the accuracy of the measured effective cross-sectional area and critical pressure ratio of the HPSV was high. The measured critical pressure ratio ranged from 0.46 to 0.50, and the flow coefficient represented by the effective cross-sectional area variation decreased with increasing valve opening. These findings have general implications for the accurate design, analysis, and control of high-pressure pneumatic servo systems.