Valve Parameters Research Articles

Optimization of Multi-Way Valve Structure in Digital Hydraulic System of Loader

In this paper, a digital hydraulic variable control method based on multi-way valve spool displacement feedback is proposed, which combines the advantages of low cost and high reliability of the loader fixed displacement pump hydraulic system, and the distinguished energy saving effect of the loader variable pump hydraulic system. Based on the principle of hydraulic resistance, the mathematical model of flow-pressure of multi-way valve was established. Meanwhile, the theoretical structure of a valve spool suitable for digital hydraulic system was deduced. On this basis, an improvement scheme of the valve spool was proposed in combination with machining feasibility. The simulation model of multi-way valve was established, the correctness of which was verified by experiment with the significance test method, and the valve port parameters of the multi-way valve were optimized by genetic algorithm. The simulation model before and after optimization was analyzed by AMESim software. The simulation results showed that the digital hydraulic system can basically realize the function of a variable system, and the energy consumption was significantly reduced compared with the fixed displacement pump hydraulic system. The optimized valve spool structure of the digital hydraulic system had more stable load characteristics than the fixed displacement pump system and a larger speed range. The increase range accounts for about 27% of the total stroke.

Experiment analysis of high output pressure piezoelectric pump with straight arm wheeled check valve

Piezoelectric pumps are applied in many fields, such as chemical analysis system and fluid pumping systems. Piezoelectric pumps with high output pressure can meet the needs of more fields. This article introduces the design and fabrication of a high output pressure piezoelectric pump with straight arm wheeled check valve. In this paper, the influence of straight arm wheeled check valve on the output pressure of piezoelectric pump is deeply discussed from the aspect of energy loss. This study investigated the effect of valve arm number ( N = 2, 3,4, and 5), the valve arm width ( W = 0.8, 1.0, and 1.2 mm), and the valve arm length ( L = 1.92, 2.02, and 2.12 mm) on the output pressure of piezoelectric pump. The output pressure characteristic of straight arm wheeled check valve piezoelectric pump with different valve parameters is obtained by experiment. Experimental results show that when N = 4, W = 1.0 mm, L = 2.02 mm, the output pressure of the straight arm wheeled check valve piezoelectric pump has the best output pressure of 27.41 kPa at 220 V and 85 Hz. This study provides a reference for the further application of piezoelectric pumps in fluid pumping field.

Surgical repair of ischemic mitral regurgitation: one ring does not fit all.

The review summarizes the key parameters that can aid in determining the optimal treatment of ischemic mitral regurgitation (IMR). Left ventricular (LV) and mitral valve (MV) parameters are important for surgical planning and risk stratification in IMR. Although LV dimensions is one of the main parameters used in the guidelines, volumes more accurately depict LV remodelling. Furthermore, wall motion abnormalities and wall motion score index can also be useful for surgical planning in treatment of IMR. Viability is best measured with cardiac magnetic resonance, but it is not feasible in certain centres. In contrast, measurement of strain with echocardiography is an emerging and feasible tool for estimating viability. MV leaflet tethering and pattern measured with echocardiography are also useful for MV surgery. Anterior leaflet excursion angle can identify patients in whom undersized ring annuloplasty is potentially unsuitable. Treatment of IMR relies on accurate parameters that can determine the optimal surgical approach. In some patients, lack of viable myocardium suggests inadequacy of revascularization and thus, an adjunctive left ventricular reconstruction may be necessary. Degree and pattern of MV leaflet tethering can indicate whether ring annuloplasty, which is the most common repair technique, is sufficient or an adjunctive sub-valvular intervention is beneficial.

An adjustable parameter water hammer wave hose testbench

In this paper, based on the servo valve controlled pressure cylinder, a scheme of hydraulic pipeline adjustable parameters water hammer wave test system is proposed. By changing the quality of pressure cylinder piston rod and controlling the opening of servo valve, the overshoot, pressure rise rate and oscillation of water hammer wave can be controlled. On this basis, based on AMESim simulation software, the paper studies the influence of different parameters of pressure cylinder and servo valve on water hammer wave, which provides the basis for the selection of main components. Finally, the experimental research is carried out on the designed system, and the results are consistent with the simulation results. The generated water hammer wave meets the requirements of the test standard, which proves that the hydraulic adjustable parameters water hammer test system developed in this paper is successful and feasible.

Design and numerical simulation for the development of an expandable paediatric heart valve.

Current paediatric valve replacement options cannot compensate for somatic growth, leading to an obstruction of flow as the child outgrows the prosthesis. This often necessitates an increase in revision surgeries, leading to legacy issues into adulthood. An expandable valve concept was modelled with an inverse relationship between annulus size and height, to retain the leaflet geometry without requiring additional intervention. Parametric design modelling was used to define certain valve parameter aspect ratios in relation to the base radius, Rb, including commissural radius, Rc, valve height, H and coaptation height, x. Fluid-structure simulations were subsequently carried out using the Immersed Boundary method to radially compress down the fully expanded aortic valve whilst subjecting it to diastolic and systolic loading cycles. Leaflet radial displacements were analysed to determine if valve performance is likely to be compromised following compression. Work is ongoing to optimise valvular parameter design for the paediatric patient cohort.

Global Synchronous Optimization Including Intake Valves and Exhaust Valves Based on MODM Strategy

Fully variable valve actuation (FVVA) technology can improve engine performance by changing engine valve timing and valve lift in different conditions. To find the optimal valve profile parameters, engine power and emissions have to be taken into account due to the contradiction between them. Therefore, the paper presented a multi-objective decision making (MODM) strategy for valve profile parameters optimization. All profile parameters both intake valves and exhaust valves were optimized synchronously. We carried out the global synchronous MODM strategy with the Radial Basis Function (RBF) response surface method (RSM). First, a FVVA system was introduced. For the FVVA system, all valve profile parameters are variable. Second, based on GT-suite, an engine model was built and its valve sub-models were rebuilt to achieve the FVVA system. Some simulation results were used to train RSM. Third, based on the simulation results, engine valve parameters were analyzed and some response surface methods were compared. The results show that RBF method has a good agreement with simulation results. At the end, global MODM strategy which optimized both intake valves and exhaust valves synchronously for engine valve parameters was implemented at 2400 RPM based on Non-dominated Sorting Genetic Algorithm (NSGA-Ⅱ) and RBF response surfaces obtained. With the obtained response surfaces, multi-objective virtual optimization which is relied on the obtained response surfaces rather than the GT-suite model was carried out. The virtual optimization results show that engine power can be improved by 1.63%, and the engine NOX emissions can be reduced by 2.75%. To verify the virtual optimization results, we carried out the simulation with the optimized parameters, and the virtual optimization results have a good agreement with results which were obtained from the simulation of the GT-suite model. Besides, the RSM-based virtual multi-objective optimization keeps faster optimization speed.

Internal leakage analysis and experiment in hydraulic control system of steam turbine inlet valve

In this paper, the transformation of steam turbine regulating system from mechanical hydraulic regulation to electro-hydraulic regulation is realized. And the internal leakage mechanism of the hydraulic control switch valve and the electro-hydraulic proportional valve in the system is analyzed. With the use of hydraulic simulation software AMESim, the mathematical model of the electro-hydraulic control system after transforming is established. The parameters of the hydraulic control switch valve and the electro-hydraulic proportional valve in the hydraulic control system of steam turbine inlet valve are studied under different internal leakage locations and different leakage degree, such as piston regulating time, steady position of piston, oil pressure and leakage flow flux. The fault characteristic table of internal leakage is obtained. An experimental platform for simulating internal leakage is built. The experimental curves of several physical quantities under different internal leakage conditions are obtained. The experimental results prove that the internal leakage has a great impact on the performance of the electro-hydraulic control system. The results of internal leakage experiment are consistent with those of internal leakage simulation.

Investigation of the Processes of Formation of Cavitation Bubbles in a New Axial Control Valve Design Featuring a Rotary Locking Device

The article presents a mathematical description of the formation process of cavitation bubbles in a new design of axial control valve fitted with a rotary locking device. The differential distribution function of the number of cavitation bubbles by size is obtained for use in calculating the main valve parameters.

Correlations between 3D mitral valve parameters and left ventricular remodeling at 6 months after ST elevation myocardial infarction: pilot study

Abstract Background Mitral valve regurgitation and LV remodeling are associated with worse prognosis in acute ST elevation myocardial infarction (STEMI) patients. 3D echocardiography provides a more accurate assessment of mitral ring and leaflet remodeling thus offering a better understanding of mitral valve (MV) and LV geometrical changes in time. Purpose We aimed to assess the echocardiographic evidence of the mitral valve geometrical changes after STEMI. Methods In this prospective study we included 30 consecutive patients aged between 35 and 68 years old, with STEMI treated by primary PCI. All underwent conventional transthoracic echocardiography. In addition to conventional parameters we measured LV global longitudinal strain (GLS) and mitral valve parameters using 3D echocardiography (4D MV Assessment 2.2 software). All measuremets were performed at baseline and at 6 month follow up. LV remodeling was defined as an increase of over 15% of the LV end diastolic volume (LVEDV) at 6 months after the STEMI. Results We found significant differences in time between LVEF (39.22% vs 43.63%, p=0.00), VTDVS (116ml vs 120ml, p=0.00), LV GLS (−13.41 vs −15.52, p=0.10). LV remodeling at 6 months after STEMI has been observed in 17% of the patients. Regarding the type of the infarction, in anterior STEMI, anterior leaflet surface increased in time (from 6.44cmp vs 7.42cmp, p=0.05), while there was no significant change in posterior leaflet area. In inferior STEMI, the area of posterior mitral leaflet decreased (4.8 cmp vs 4.5 cmp, p=0.52) as well as the leaflet length (1.42 cm vs 1.19 cm p=0.003), but the anterior leaflet remained the same. At 6 months we observed significant differences between the 2 groups (with and without LV remodeling) in the following mitral valve 3D parameters: mitral annulus area (2.6 cmp vs 1.67 cmp, p=0.02), mitral circumference (2.57 cm vs 1.74 cm, p=0.021), bicomisural diameter (2.66 cm vs 2.16 cm, p=0.018), tenting area (p=0.009), anterior leaflet length (2,66 cm vs 2,015 cm p=0.018) and anterior leaflet area (3,69 cmp vs 2.49 cmp, p=0.002). Baseline LV GLS significantly correlated with the following mitral valve 3D parameters at 6 months: anterior leaflet area, posterior leaflet area, anterior leaflet length, tenting height, tenting area, mitral ring 3D area, anteroposterior and bicommissural diameters and mitral circumference (correlation coefficient >0.5). Using linear regression we proved that LV GLS can predict the shortening of the posterior MV (cut off −12.6, AUC 0.844, p=0.011) after 6 months follow up. These findings were independent of the presence and severity of mitral regurgitation. Conclusion Using 3D echocardiography, significant changes in mitral valve geometry were detected at 6 months follow up in STEMI patients. LV remodeling is associated with increased mitral annulus dimensions. Funding Acknowledgement Type of funding source: Other. Main funding source(s): This work was supported by CREDO Project - ID: 49182, financed through the SOP IEC -A2-0.2.2.1-2013-1 cofinanced by the ERDF.

Prevalence of triceps suralis lenghtening among crouch gait in cerebral palsy

Aortic interleaflet triangle reshaping (AITR) is a surgical approach to aortic valve incontinence that involves placing three stitches at half of the interleaflet triangles height. In this work, the relationship between the actual stitch height and valve functioning, and the safety margin that the surgeon can rely on in applying the stitches were systematically investigated in vitro. AITR surgery was applied to six swine aortic roots placing the stitches empirically at 50%, 60% and 75% of the triangle heights. Then the actual stitch heights were measured and the hydrodynamic performances were evaluated with a pulsatile hydrodynamic mock loop. Actual stitch heights were 45±2%, 61±4% and 79±6%. As compared to untreated conditions, the 50% configuration induced a significant variation in the effective orifice area. With stitches placed at 60%, the mean systolic pressure drop increased significantly with respect to the untreated case, but no significant changes were recorded with respect to the 50% configuration. At 75%, all the hydrodynamic parameters of systolic valve functioning worsened significantly. Summarizing, the AITR technique, when performed in a conservative manner did not induce significant alterations in the hydrodynamics of the aortic root in vitro, while more aggressive configurations did. The absence of a statistically significant difference between the 50% and 60% configurations suggests that there is a reasonably limited risk of inducing valve stenosis in the post-op scenario due to stitch misplacement.

Optimization of transmission capacity of energy water pipeline networks with a tree-shaped configuration and multiple sources

The problem of pipeline network transmission capacity optimization is solved during network design, optimization, and development. It consists in determining the optimal pipeline diameters, installation sites, and parameters of pumps and valves. This study proposes a methodology for optimizing the transmission capacity of tree-shaped water pipeline networks of energy systems that serve various purposes and have multiple sources. A method for constructing a network model that ensures the versatility of its representation regardless of the purpose of the network and the composition of its equipment is proposed. A method for modeling of the branch that enables one to flexibly alter the configuration of the branch in the process of running the optimization algorithm without changing the network topology is presented. The mathematical statement of the problem is formulated as the discrete-continuous optimization problem. This statement is based on the proposed methods of representing the network model and its elements. An algorithm based on dynamic programming is proposed, which implements a new approach to setting up the computational procedure and is versatile enough for calculating networks that serve various purposes. The results obtained during real network optimization are presented.

Digital twin-driven optimization of gas exchange system of 2-stroke heavy fuel aircraft engine

Multiple parts in gas exchange system of 2-stroke heavy fuel aircraft engine with poppet valves lead to complicated manufacturing and inefficient assembly. Besides, real experimental optimization wastes lots of time and cost due to the increased valve parameters. To address the above issues, the paper proposes a digital twin (DT)-driven optimization method with several DT modules for the system to virtually simulate and optimize the parameters, performance and manufacturing with data interaction and recorded. The DT modules receive real-time feedback data from manufacturing measurements and performance tests to conduct the correction throughout the optimization process. The results demonstrate that the virtual engine model with feedback and correction is quite precise and credible compared with test results, and iterative calculation for optimal parameters is performed efficiently. With the guidance of virtual manufacturing, real manufacturing and assembly are arranged more reasonably and efficiency has been promoted. Real-world test found both power and gas exchange performance improved about 4% under various engine speeds and loads, which verified the effectiveness of DT-driven optimization. The study achieves the integration between virtual and real worlds of the system performance and manufacturing, which facilitates the development of aircraft engine smart manufacturing.

A Multivariate State Estimation Technique and Multilayer Forward Neural Network Framework on Steam Turbine Valve Flow Curve Simulation

The Multivariate State Estimation Technique (MSET) is firstly implemented as the fault detection technique for monitoring parameters of the steam turbine valve. Second, healthy operation states are remained to form a preliminary dataset for the valve curve simulation. Then, the Forward neural network (FNN) based piecewise linear fitting method is used to simulate the steam turbine valve flow curve. With a MSET-FNN framework proposed, the simulation accuracy will be enhanced by removing the unhealthy operational states. In addition, the simulation process will gain a speed up with the utilization of GPU.

НАСОС-ФОРСУНКА ДИЗЕЛЯ С КОЛЬЦЕВЫМ УПРАВЛЯЮЩИМ КЛАПАНОМ

The studies were carried out with the aim of modernizing the pump injector with a hydraulic actuator of the HEUI system plunger with the development of a control valve model based on a split elastic ring that provides fast fuel injection control. The upgraded device differs from the existing ones in that instead of a control freely floating valve (ball) or a poppet valve with springs, a valve in the form of a split elastic ring is installed in the valve assembly. One end of this ring is fixed rigidly, the other is freely movable to block the drain channel of the liquid. The canal overlaps the free edge of the ring when the electromagnet is turned on (installed with a gap inside the ring), and also (in the absence or malfunction of the electromagnet) from the valve itself running under the pressure of the supplied fluid. When upgrading the pump injector by the proposed method and using an annular control valve with electronic control (with optimal ring parameters), a new technical effect is achieved - reducing the response time of the control valve. This is due to the fact that the free edge of the split elastic ring, like a mechanical multiplier, blocks the drain canal π times faster than the valve stroke when it rises from the pressure of the fluid flow or signal when the electromagnet is on. The ring valve simultaneously acts as a spring to return to its original position, simplifying the design as much as possible. In the course of research, a new mathematical expression was derived for calculating the valve stroke depending on its design parameters. Using this formula, the optimal parameters of the control ring valve of the pump injector were established, which affect the quality of fuel injection in a wide range of diesel operation: diameter - 20 mm, ring width - 12 mm, thickness - 0.46 mm, diameter of the control fluid supply canal - 3 mm.

НАСОС-ФОРСУНКА ДИЗЕЛЯ С КОЛЬЦЕВЫМ УПРАВЛЯЮЩИМ КЛАПАНОМ

The studies were carried out with the aim of modernizing the pump injector with a hydraulic actuator of the HEUI system plunger with the development of a control valve model based on a split elastic ring that provides fast fuel injection control. The upgraded device differs from the existing ones in that instead of a control freely floating valve (ball) or a poppet valve with springs, a valve in the form of a split elastic ring is installed in the valve assembly. One end of this ring is fixed rigidly, the other is freely movable to block the drain channel of the liquid. The canal overlaps the free edge of the ring when the electromagnet is turned on (installed with a gap inside the ring), and also (in the absence or malfunction of the electromagnet) from the valve itself running under the pressure of the supplied fluid. When upgrading the pump injector by the proposed method and using an annular control valve with electronic control (with optimal ring parameters), a new technical effect is achieved - reducing the response time of the control valve. This is due to the fact that the free edge of the split elastic ring, like a mechanical multiplier, blocks the drain canal π times faster than the valve stroke when it rises from the pressure of the fluid flow or signal when the electromagnet is on. The ring valve simultaneously acts as a spring to return to its original position, simplifying the design as much as possible. In the course of research, a new mathematical expression was derived for calculating the valve stroke depending on its design parameters. Using this formula, the optimal parameters of the control ring valve of the pump injector were established, which affect the quality of fuel injection in a wide range of diesel operation: diameter - 20 mm, ring width - 12 mm, thickness - 0.46 mm, diameter of the control fluid supply canal - 3 mm.

Continued follow-up of the free margin running suture technique for mitral repair.

The free margin running suture (FMRS) technique was recently proposed to treat complex degenerative mitral lesions. Limited follow-up data are available. We evaluated the midterm reliability of this technique and the associated mitral valve parameters using rest/stress echocardiography. One-hundred-eight consecutive patients at 2 European centres were included. Prospective follow-up was performed (266.1 patient-years, average duration 2.5 ± 2.5 years). Echocardiographic scans at rest were obtained for all patients at hospital discharge and at follow-up. Stress echocardiography was also performed in 17 patients. There were no operative deaths. FMRS was performed through a right minithoracotomy in 86.1% of patients, with a robotic-assisted technique in 5.6% and through a sternotomy in 8.3%. Bileaflet disease was noted in 31.4%. One patient (0.9%) presented a 2+/4+ residual mitral regurgitation at discharge; lower-degree or no residual regurgitation was noted in the remaining patients. At the follow-up examination, 1 patient (0.9%) presented with a 2+/4+ mitral regurgitation. Coaptation length at discharge versus that at follow-up was 1.3 ± 0.2 vs 1.3 ± 0.1 cm (P = 0.13); the average transmitral gradient was 4.8 ± 1.5 vs 3.5 ± 0.9 mmHg (P < 0.001). In a subpopulation, follow-up echocardiography indicated that the average transmitral gradient at rest versus that at peak effort was 3.2 ± 0.7 vs 5.1 ± 1.3 mmHg (P < 0.001), with no appearance of significant mitral regurgitation and marginally significant increases in pulmonary artery systolic pressures (P = 0.049). Data indicate effectiveness and reproducibility of FMRS, with stability of valve function at midterm. FMRS was also associated with promising outcomes in diastolic performance both at rest and during exercise.

Modelling of an electro-hydraulic variable valve actuator for camless engines aimed at controlling valve lift parameters

This paper presents the mathematical modelling of an Electro-Hydraulic Valve Actuator (EHVA) prototype and its application to the design of cycle-by-cycle Valve Lift Control(VLC). EHVA is rated in the technical literature as an apparatus enabling Variable Valve Actuation (VVA) and implementation of advanced combustion concepts in future camless engines. It is, therefore, a first step towards the development of camless engines in which valve lift and timing can be freely adjusted valve-by-valve and cycle-by-cycle. Particular attention is paid to parameter identification aimed at obtaining a predictive simulation model of valve lift trajectories and valve parameters (e.g. lift, duration, area) for a wide range of system inputs. An energy loss assessment of a valvetrain based on EHVAs is described, and the results are compared with those obtained with a traditional cam-based valvetrain. The validated model is then used to build detailed numerical maps of valve parameters that are fundamental for setting up cycle-by-cycle controllers of valve parameters. Hence, the authors present the design of a cycle-by-cycle controller of maximum valve lift, the performance of which is tuned by simulations and then verified experimentally.

Flow Field Analysis of Hydraulic Multi-way Valve Based on CFD

Referring to the structure and parameters of the actual multi-way valve, the CAD software SOLIDWORKS was used to establish the three-dimensional geometric model of the internal flow passage of the hydraulic multi-way valve, and the model was calculated and analyzed by CFD software Star CCM+. By studying the flow field distribution in the valve chamber, the pressure distribution at each monitoring point in the chamber and the change of the overall flow rate were obtained, and the steady-state hydrodynamic force of the valve core was calculated. The effects of flow rate and the opening of the valve core on the pressure distribution and steady-state hydrodynamic force in the valve chamber were analyzed under various working conditions. The results show that the steady-state hydraulic force on the valve core increases with the increase of flow rate and decreases with the increase of valve opening. The pressure loss at the inlet and outlet of the slide valve is mainly caused by the throttling characteristics of the oil at the throttle port. The smaller the opening, the greater the inlet pressure and the greater the pressure at all points in the valve chamber.

Improving the Stability of Blood Flow through Mechanical Artificial Tricuspid Valves of the Heart

Hemodynamic characteristics of two models of mechanical artificial tricuspid valves of the heart were compared: Tricardix (RF Patent No. 2325874) and MAHV (RF Patent No. 181544). 3D models of the artificial heart valves under study were created. The operational environment conditions were simulated using SolidWorks. SolidWorks Flow Simulation was used for hemodynamic calculations. The efficiency criteria were determined on the basis of the hemodynamic parameters of a native aortic heart valve.

Modeling and Simulation Analysis of Wet Multi-Disk Service Braking System for Heavy Vehicles

A new type of charging valve with electro-hydraulic closed-loop feedback is designed, and a wet multi-disc dual-circuit service brake is built based on AMEsim. The charging and discharging characteristics of the accumulator are studied. The results show that under the condition of a medium-flow constant current source, the dual-circuit accumulator responds quickly, and a single charging can smoothly provide multiple stable discharge output. The response to the pressure output caused by the static structural parameters of the tandem braking valve and the pedal signal is studied. The results show that: the pedal signal can significantly change the brake pressure output, but the preload of the return spring is not apparent; the change of the cross-sectional diameter of the rear axle spool will cause the spool opening lags, and the difference in the spool diameter will cause the spool closing lags. The time response performance of single-axle braking and dual-axle braking is studied. The response from environmental factors such as road adhesion coefficient, slope, load, and brake cool modes to braking distance, braking deceleration, and braking temperature is studied. We establish a parameter ranges of braking safety zone and braking safety comfort zone. This study provides a comparison and reference to the design of a new charging valve and the performance test of the service braking system of heavy vehicles.