•Investigating the operating limit of the solenoid directional control valve.•Using CFD 3D ANSYS/Fluent software to calculate the flow force.•Designing the innovative valve body to extend operating ...limit by over 45%.•Verifying the new design on the test bench and confirming the computed results.
Solenoid direct operated spool type directional control valves are often used in various machines and equipment. A subject of the analysis presented in the paper is the directional control valve WE10H produced by several manufacturers. The continual development of this type of valves has allowed for significant reduction of the flow resistance through the channels and consequently for relatively high flow range. The increase of flow range causes a growth of flow forces which may change the balance of forces acting on the spool and prevent the correct operation of the valve. That is why the undertaken task is important.
The paper proposes calculation of the forces associated with the flow (pressure force and viscous force) using 3D CFD modeling. In the proposed method, first the surface affected by the forces associated with the flow through each path was defined and then, using CFD method, values of the flow forces were determined.
To confirm the obtained results of CFD calculations a device for measuring forces acting along the axis of the spool was prepared. The force values obtained in the CFD calculations were compared with those obtained on the test bench. The resulting accuracy was satisfactory. In order to reduce flow forces additional internal channels in the valve body were introduced. The innovative solution of the valve allowed for a higher flow range of about 45% without any change of spring or solenoid.
Investigating the reduction of flow resistance by hydraulic directional valve. Replacing of directional spool valve by logic type valve mounted on the same subplate. Verifying the new design by CFD ...analysis with ANSYS/FLUENT software. Allowing an example of the solution to reduce pressure loss over 35–61%. Conducting an experimental studies to verify CFD analysis.
The aim of this paper is to investigate the reduction of flow resistance in a hydraulic system. The undertaken matter is focused on a spool type directional control valve with pilot operated check valves. In the paper there is a proposition of replacing a 4-way directional control valve with pilot operated check valves by suitable unit consisting of logic valves. Therefore, a body of new directional control valve has been designed. Four logic valves are mounted on the body and closed with a cover on which electromagnetic pilot valve is assembled. The hydraulic ports of the body are in accordance with the standard ISO 4401 – 08-07-0-94, so the proposed new directional control valve can be applied alternatively to a directional spool valve. An important task given during the work is to create the systems of flow paths inside the body, which are assumed to be performed with simple technologies like: drilling, boring and milling. The system of the designed flow paths is verified by CFD analysis with the use of ANSYS/FLUENT program on three-dimensional model. Obtained results are compared with the results of the characteristics given in catalogues and coming from experimental research of the prototype. The difference in pressure loss during flow for the logic valve taken from CFD calculation and the catalogue do not exceed 5%. Presented in the paper directional control valve may operate for volumetric flow rate up to 450dm3/min and the pressure up to 42MPa. In the proposed solution, although simple technologies of making flow paths were applied, the pressure losses were reduced over 35%. The developed solution is close to a standard directional spool valve and can be assembled on an identical sub-plate.
•Research results of a 4/3 sectional proportional directional control valve.•A concept of using flow forces for pressure compensation.•Proposition of creating the appropriate spool grooves to obtain ...required jet angle.•Obtaining dependency of spool position on jet angle and thus on flow forces.•Obtaining the required valve characteristics through the spring stiffness selection.
The main subject of this article is pressure compensation in a multi-section proportional directional control valve. The undertaken compensation task was carried out without the use of neither additional compensating valves nor other correcting elements, such as sensors in a feedback control system. The proposed method consists in the appropriate adjustment of forces acting on the valve spool. It requires knowledge of the electromagnet force characteristics and the appropriately matched stiffness and initial tension of the valve spring. In order to achieve the assumed objective, a number of CFD simulations was performed on a 3-D fluid model. The CFD analysis allowed determination of the values of flow resistance through the valve and the axial component of the flow force acting on the spool. The values calculated for various spool positions and flow velocities were approximated using analytical equations. Next, the mathematical model was built and simulations in Matlab/Simulink system were carried out. In the first stage of the research, flow characteristics of a single valve section were determined. The obtained results were then verified on the test bench. In the second stage, the simulation model was used to examine the possibility of pressure compensation in a three-section control valve. In this case, the individual valve sections were loaded unevenly by applying pressure in a wide range of values. It has been demonstrated, that the appropriate shaping of the spool geometry allows usage of the flow forces for pressure compensation in multi-section proportional directional control valves.
This article presents a new control method for a pneumatic cushion for transporting heavy payloads. Pneumatic cushions are particularly useful for moving structural or non-structural components over ...hard, smooth floors. They can be put directly under load, lifted to a small height by applying air pressure and moved. A thin, friction-reducing air film is formed under the cushion during lifting. Currently, pressure is usually controlled manually, which causes difficulty in establishing an appropriate pressure value, especially when the load is distributed unevenly between multiple cushions. In practice, the pressure is often set higher than is necessary to move the load. Excessive pressure does not reduce friction, but increases air consumption. Hence, in this article an effort is described to obtain the minimum allowable pressure. The first part of the article includes the theoretical background, detailed models of the proposed automatic controllers and the parameters of a test bench. Experiments were carried out with a typical manual control system and two automatic controllers, with PID and fuzzy logic algorithms. The results indicate that automation of the control system significantly reduces air consumption and shortens the time needed to obtain the correct pressure. Moreover, it improves the stability of the load by allowing more accurate vertical positioning of individual cushions.
•Presenting transport platform on four pneumatic cushions.•Obtaining characteristics of the platform with manual control system.•Presenting innovative concept of automatic control system for the platform.•Proposing PID and Fuzzy Logic algorithms for the controller.•Carrying out tests of the controllers on the platform and comparing results.
•Directional valve with standard ISO 440-08 has been constructed from logic valves.•Only one innovative valve may replace whole family of the standard valves.•CFD analysis and bench tests of the ...innovative valve has been carried.•Parameters of the innovative valve are equaling or surpassing the standard ones.•The innovative valve has additional possibilities of pressure and flow control.
The paper refers to four-port solenoid pilot operated valves, which are subplate mounted in a hydraulic system in accordance with the ISO 4401 standard. Their widespread use in many machines and devices causes a continuing interest in the development of their design by both the scientific centers and the industry. This paper presents an innovative directional control valve based on the use of logic valves and a methodology followed for the design of it by using Solid Edge CAD and ANSYS/Fluent CFD software. The valve design methodology takes into account the need to seek solutions that minimize flow resistance through the valve. For this purpose, the flow paths are prepared by means of CAD software and pressure-flow curves are determined as a result of CFD analysis. The obtained curves are compared with the curves available in the catalogs of spool type directional control valves.
The new solution allows to replace the whole family of spool type four-port directional control valves by one valve built of logic valves. In addition, the innovative directional control valve provides leak-proof shutting the flow paths off and also it can control flow rate and even pressure of working liquid. A prototype of the valve designed by the presented method has been made and tested on the test bench. The results quoted in the paper confirm that the developed logic type directional control valve is able to meet all designed connection configurations, and the obtained pressure-flow curves show very good conformity with the results of CFD analysis.
The main objective of this article is to analyse flow coefficient of a proportional directional valve with integrated spool position controller. The valve geometry has been modified by creating ...additional undercuts on the spool, which provide improved flow characteristics, especially at low flow rates. The analysis consisted of two phases, including computer simulations and test bench experiments. At first, flow through the valve was simulated by the means of CFD method in ANSYS/Fluent software, assuming the fixed spool positions. Based on the results, flow coefficient values were determined. The results showed, that in the examined gap width range, the coefficient value is mainly related to the spool position, and to a lesser extent to the volumetric flow rate. Hence, a proposal to formulate the flow coefficient value as a function of spool position or spool position and flow rate was made. Three approximating functions were determined in Matlab system on the basis of the obtained CFD results: a linear curve μ=f(xg), as well as a linear polynomial surface and a quadratic polynomial surface μ=f(xg,Q). Next, the results were verified by experiments conducted at a test bench.
The best fit flow coefficient function was then used in the subsequent simulations on a multi-actuator system comprising three parallel-connected valves supplied by a single pump. In this case, each valve was set a different fixed spool position, which resulted in a different throttle gap width. Analysis of the system was carried out using an own-developed computer software for solving the analytical equations. Finally, the results were compared to those obtained by means of a CFD method, and a satisfactory compliance was achieved.
•Research of a proportional directional control valve with a spool position controller.•A concept of formulating flow coefficient as a function of spool position and flow rate.•CFD simulations in a wide range of spool positions and flow rates.•Determination of flow coefficient functions and verification by test bench experiments.•Analysis of a multi-valve system using the determined flow coefficient function.
The interest in unicompartmental knee arthroplasty (UKA) for medial osteoarthritis has increased rapidly but the long-term follow-up of the Oxford UKAs has yet to be analysed in non-designer centres. ...We have examined our ten- to 15-year clinical and radiological follow-up data for the Oxford Phase III UKAs.
Between January 1999 and January 2005 a total of 138 consecutive Oxford Phase III arthroplasties were performed by a single surgeon in 129 patients for medial compartment osteoarthritis (71 right and 67 left knees, mean age 72.0 years (47 to 91), mean body mass index 28.2 (20.7 to 52.2)). Both clinical data and radiographs were prospectively recorded and obtained at intervals. Of the 129 patients, 32 patients (32 knees) died, ten patients (12 knees) were not able to take part in the final clinical and radiological assessment due to physical and mental conditions, but via telephone interview it was confirmed that none of these ten patients (12 knees) had a revision of the knee arthroplasty. One patient (two knees) was lost to follow-up.
The mean follow-up was 11.7 years (10 to 15). A total of 11 knees (8%) were revised. The survival at 15 years with revision for any reason as the endpoint was 90.6% (95% confidence interval (CI) 85.2 to 96.0) and revision related to the prosthesis was 99.3% (95% CI 97.9 to 100). The mean total Knee Society Score was 47 (0 to 80) pre-operatively and 81 (30 to 100) at latest follow-up. The mean Oxford Knee Score was 19 (12 to 40) pre-operatively and 42 (28 to 55) at final follow-up. Radiolucency beneath the tibial component occurred in 22 of 81 prostheses (27.2%) without evidence of loosening.
This study supports the use of UKA in medial compartment osteoarthritis with excellent long-term functional and radiological outcomes with an excellent 15-year survival rate. Cite this article: Bone Joint J 2016;98-B(10 Suppl B):41-7.
A selective and sensitive molecular sensor for trivalent lanthanide (Ln3+) ions based upon a malonamide-functionalized gold nanoparticle was developed for colorimetric detection in water. A new ...synthetic approach permits nanoparticle synthesis, stabilization, and incorporation of a selective lanthanide binding site in a single, direct step. The design incorporates a specifically tailored dual function precursor ligand that bears a sodium thiosulfate (Bunte salt) group that links to the gold nanoparticle core and a tetramethylmalonamide (TMMA) group that serves as a selective Ln3+ binding site. The sensor’s colorimetric response to lanthanide ions is immediate, and it is sensitive down to ∼50 nM for Eu3+ and Sm3+. This study demonstrates a general strategy for direct, convenient nanoparticle synthesis that enables the incorporation of analyte binding groups directly to the nanoparticle surface, allowing colorimetric sensors to be developed for widespread use. The one-step synthesis offers uniform surface ligand composition, reduces the volume of waste generated during nanoparticle synthesis and purification, produces functionalized gold nanoparticles that are stable in nonmodified aqueous environments, and offers colorimetric detection at ambient temperature.
Purpose
In the last decade, a major increase in the use of and interest in unicompartmental knee arthroplasty (UKA) has developed. The Oxford Phase 3 UKA is implanted with a minimally invasive ...technique using newly developed instruments. The objective of this prospective study was to evaluate the outcome of UKA in patients with medial osteoarthritis of the knee in a high-volume unit.
Methods
Two-hundred and forty-four UKAs were performed with a minimally invasive approach. The median age was 72 (43–91) years. The median follow-up was 4.2 years (range 1–10.4 years). Fourteen patients died, and nine were considered to be lost to follow-up, but all had a well-functioning prosthesis in situ until their last follow-up. Pain, function and health-related quality of life were evaluated pre- and postoperatively using patient- and assessor-based outcome scores, as well as radiographic evidence.
Results
The mean Knee Society knee and function scores, WOMAC-scores, Oxford-score and VAS pain and satisfaction all improved. Nine knees required revision. Eleven patients required an additional arthroscopic procedure due to persisting pain secondary to intra-articular pathology, and four patients required manipulation under anaesthesia because of limited range of motion. The 7-year cumulative survival rate of the arthroplasty was 94.4%. A low incidence (21%) of a radiolucent line beneath the tibial component was observed at 5 years of follow-up.
Conclusion
This study showed a high survival rate of the Oxford Phase 3 UKA. Patient satisfaction and functional performance were also very high. Major complication rate was low; in addition, the incidence of radiolucency under the tibial component, when compared to present literature, was low. When strict indication criteria are followed, excellent, durable, and in our opinion reliable, results can be expected for this procedure.
The interactions of nanoparticles with biomolecules, surfaces, or other nanostructures are dictated by the nanoparticle’s surface chemistry. Thus, far, shortcomings of syntheses of nanoparticles with ...defined ligand shell architectures have limited our ability to understand how changes in their surface composition influence reactivity and assembly. We report new synthetic approaches to systematically control the number (polyvalency), length, and steric interactions of omega-functionalized (targeting) ligands within an otherwise passivating (diluent) ligand shell. A mesofluidic reactor was used to prepare nanoparticles with the same core diameter for each of the designed ligand architectures. When the targeting ligands are malonamide groups, the nanoparticles assemble via cross-linking in the presence of trivalent lanthanides. We examined the influence of ligand composition on assembly by monitoring the differences in optical properties of the cross-linked and free nanoparticles. Infrared spectroscopy, electron microscopy, and solution small-angle X-ray scattering provided additional insight into the assembly behavior. Lower (less than 33%) malonamide ligand densities (where the binding group extends beyond the periphery of diluent ethylene glycol ligands) produce the strongest optical responses and largest assemblies. Surprisingly, nanoparticles containing a higher surface number of targeting ligand did not produce an optical response or assemble, underscoring the importance of an informed mixed ligand strategy for highest nanoparticle performance.
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