Valve Design Research Articles

Impact of sex on Transcatheter aortic valve replacement outcomes: Results of a single-center study

BackgroundEarly studies on transcatheter aortic valve replacement (TAVR) outcomes showed that female sex was associated with better survival. With increased use of new-generation valves, the impact of sex on contemporary TAVR outcomes is less well known. MethodsRetrospective analysis using institutional National Cardiovascular Data Registry STS/ACC TVT data was performed on all patients undergoing TAVR at Yale New Haven Hospital from July 2012 to August 2019. New-generation valves were Evolut PRO, Evolut R, and SAPIEN 3. Old-generation valves were CoreValve, SAPIEN, and SAPIEN XT. Log-rank test and Kaplan-Meier curves were used to compare sex differences in survival up to 1 year after TAVR. Cox modeling was used to adjust for baseline and procedural characteristic differences. Results927 consecutive patients (41.4% women) underwent TAVR. Women were older (82.8 vs 80.6 years old; p < 0.001) with higher STS mortality scores compared with men (7.6% vs 6.4%; p < 0.001) despite lower prevalence of cardiovascular comorbidities including coronary artery disease, peripheral artery disease, and smoking. Most cases used transfemoral access (90.5%) and new-generation devices (72.3%). Women received smaller valves compared with men (20–26 mm: 78.0% vs 32.9%; 29–34 mm: 22.1% vs 67.1%; overall p < 0.0001). There were no statistically significant differences between sexes in both unadjusted and adjusted 1-year mortality. ConclusionOur data show no significant difference in 1-year survival between sexes using primarily new generation valves. Further studies should reassess the impact of sex on TAVR outcomes and whether newer technologies like new valve design and sizes, and CT imaging may have eliminated sex-based disparities.

The effect of valve design on the pressure losses in a high-pressure homogenizer – An improved pressure drop correlation for estimating gap height

Understanding how the design of high-pressure homogenizer valves influence pressure losses in the device is of general interest for performance optimizing, and of special importance for developing correlations for predicting gap heights and gap velocities. The traditionally used correlation is from 1975 and based on a limited experimental dataset on gaps that are longer and often of lower capacity than contemporary ones. This study uses well-validated best-practice CFD to develop an improved correlation for how homogenizing pressure depends on valve designs, extending previous investigations to also include the effect of seat and forcer incline angles. The suggested correlation differs substantially from the traditional ones, shows a marked effect on inlet and exit loss coefficients of Reynolds number and of inlet seat incline angle. For cases with Reynolds number comparable to pilot- and production-scale homogenizers, the gap height can be predicted to within 10% of the set value, using the suggested correlation.

Fluid–structure interaction modeling of bi-leaflet mechanical heart valves using smoothed particle hydrodynamics

Heart valves are essential for maintaining unidirectional blood flow, and their failure can severely affect cardiac functions. The use of artificial heart valves as replacement has proven to be a reliable and effective solution. Computational fluid dynamics has emerged as a powerful numerical tool for investigating the design, performance, and malfunctioning of mechanical heart valves without the need for invasive procedures. In this study, we employed smoothed particle hydrodynamics (SPH) in an open-source code “DualSPHysics,” to study the hemodynamics of a bi-leaflet mechanical heart valve (BMHV). The proposed SPH method was validated against the traditional finite volume method and experimental data, highlighting its suitability for simulating the heart valve function. The Lagrangian description of motion in SPH is particularly advantageous for fluid–structure interaction (FSI), making it well-suited for accurately modeling the heart valve dynamics. Furthermore, the SPH/FSI technique was applied to investigate the hemodynamic abnormalities associated with BMHV dysfunction. This work represents the first attempt to use SPH to model flow through a realistic BMHV by incorporating FSI. The normal and altered flow behavior and the movement dynamics of the BMHV under various blockage scenarios have also been investigated along with the potential risks of the blocked mechanical valve. The findings demonstrate that this SPH/FSI approach provides a unique, effective, and valuable tool for accurately capturing the transient hemodynamic behavior of bi-leaflet heart valves and its versatility enables the application to more complex patient-specific issues related to cardiovascular diseases.

Retracted: Design of Noise-Reducing Two-Stage Cage Control Valve and Its Fluid Characteristics and Cavitation Study

Retracted: Design of Noise-Reducing Two-Stage Cage Control Valve and Its Fluid Characteristics and Cavitation Study

Numerical analysis of fluid force on orifice structure of valve disc for nuclear globe valve

The globe valve fails to open completely sometimes due to insufficient lifting of the valve disc during the operation of the nuclear power plant. The main reason is the inadequate understanding of changes in fluid force. Therefore, conducting research on the fluid force of the globe valve is crucial. In this study, we establish a high-fidelity computational fluid dynamics (CFD) numerical model to investigate the flow characteristics of a novel balanced globe valve. Based on the analysis results, we concluded that the size of the throttle orifice is an essential factor affecting fluid force. Therefore, the impact of the throttle orifice sizes on the fluid force is studied. Meanwhile, the coupling influence of different valve disc displacements and inlet pressures on fluid force is quantitatively analyzed. This study provides a basis for the design of globe valves and has potential value for the dynamic control and energy utilization.

THE EFFECT OF BILEAFLET MECHANICAL HEART VALVE DESIGNS ON BIOMECHANICAL BEHAVIOURS – A FINITE ELEMENT ANALYSIS

Heart valve replacement is a popular treatment modality for patients with valvular heart disease. One of the prominent issues of mechanical heart valve is blood clotting around the valve that could lead to operation failure. Different valve design affects the valve structural behaviour differently which could be associated to the valve leaflet movement and its attachment to the housing. This study aimed to analyse the stress and total deformation of a fixed and expandable heart valve designs under a closed and opened leaflet conditions using three-dimensional (3-D) finite element analysis (FEA). Geometrical valve models were created in SolidWorks 2020 and then exported into Ansys 2022 R2. All models were assigned with linearly elastic, isotropic, and homogenous properties. A pressure of 16 kPa was applied on the top (closed condition) and bottom (opened condition) surfaces of the leaflets. The results exhibited that the expandable design recorded about 98% and 8.6% higher stress than the fixed design under the closed and opened conditions, respectively. The expandable valve was also observed to generate approximately 186% and 182% greater total deformation compared to the fixed valve under the closed and opened conditions, respectively. Of the valve designs evaluated, the fixed valve was found to be more satisfactory. However, the expandable valve could also be of interest with relevant modifications imposed if the adverse functionality impacts are concerned.

Study on the design of single-seat control valve with stable flow regulation and its fluid flow characteristics and thermal stress

Aiming at technical problems such as unstable flow at small openings and uneven force on the valve core, the single-seat control valve with stable flow regulation is researched and designed. The tapered surface of the outer edge of the valve core can cooperate with the valve seat when the valve core is running stably, resulting in higher flow regulation accuracy and more stable regulation. The mechanical characteristics and flow characteristics are analyzed. The fluid flow simulation analyzes the pressure, velocity, density, mass flow rate and volume flow rate of the fluid under small and large openings of the single-seat control valve. The relationship between the maximum pressure, maximum velocity, maximum density, mass flow rate and volume flow rate of the inlet and outlet with the opening are analyzed from small opening to large opening and smaller opening. The spool motion simulation analyzes the relationship between actuator driving force, unbalanced force, linear displacement, velocity and acceleration with time. The thermal stress simulation analyzes the thermal temperature, resultant heat flow, thermal stress, thermal strain and safety factor, and the material strength meets the requirements. The valve body pressure test, valve seat sealing test, full stroke and switching time test, drift and jitter test, starting deviation test, basic error and return difference test and dead zone test are carried out on the single-seat control valve. The test results all meet the requirements. The simulation results are compared and analyzed with the test results, and the simulation results are consistent with the test result.

Short- and Long-term Clinical Outcomes of Balloon-expandable Versus Self-expanding Valves in Patients Undergoing Transcatheter Aortic Valve Replacement: A Meta-analysis

Background: Distinct clinical differences exist between balloon-expandable valves (BEVs) and self-expanding valves (SEVs) used in transcatheter aortic valve replacement (TAVR) for aortic stenosis. However, randomised data on comparative outcomes are limited. The aim of this meta-analysis was to analyse the differences in short- and longer-term clinical outcomes between the two valve designs. Methods: A comprehensive literature search for all studies up to and including April 2020 on the clinical outcomes of BEVs versus SEVs was performed. Study outcomes were divided into short term (in-hospital or 30 days), intermediate term (1 year) and long term (3 years). The primary outcome was all-cause mortality. Secondary endpoints were stroke or transient ischaemic attack (TIA), life-threatening or major bleeding, at least moderate paravalvular leak (PVL), permanent pacemaker (PPM) implantation, aortic valve area (AVA) and aortic valve mean pressure gradient (AV MPG). Results: A total of 41 studies (BEV, n=23,892; SEV, n=22,055) were included. At in-hospital/30 days, all-cause mortality favoured BEV (OR 0.85; 95% CI [0.75–0.96]). BEV had lower rates of PVL (OR 0.42; 95% CI [0.35–0.51]) and PPM (OR 0.56; 95% CI [0.44–0.72]), but smaller AVA (mean −0.09 cm2; 95% CI [−0.17, 0.00]) and higher AV MPG (mean 2.54 mmHg; 95% CI [1.84–3.23]). There were no significant differences in the incidence of stroke/TIA or bleeding between the two valve designs. At 1 year a lower PPM implantation rate (OR 0.44; 95% CI [0.37–0.52]), fewer PVLs (OR 0.26; 95% CI [0.09–0.77]), smaller AVA (mean −0.23 cm2; 95% CI [−0.35, −0.10]) and higher AV MPG (mean 6.05 mmHg; 95% CI [1.74–10.36]) were observed with BEV. No significant differences were observed in mortality, stroke/TIA or bleeding. There was no significant difference in mortality at 3 years between the two valve designs. Conclusion: In the short–intermediate term, SEVs had better valve haemodynamics but had higher PVL and PPM implantation rates than BEVs. However, there were no differences in intermediate–long-term mortality, stroke or TIA, or bleeding complications. A better understanding of these differences will enable TAVR operators to tailor their valve choice based on individual patient profile.

Redo-TAVI with a balloon-expandable valve and the impact of index transcatheter aortic valve design.

Redo-TAVI with a balloon-expandable valve and the impact of index transcatheter aortic valve design.

Virtual Reality-Enhanced Fluid Dynamics for Thermodynamic and Hydrodynamic Evaluation in Valve Design

Virtual Reality-Enhanced Fluid Dynamics for Thermodynamic and Hydrodynamic Evaluation in Valve Design

Effect of spool posture on control valve performance considering outlet shape and large fit clearance

The control valve serves as a crucial component of the downhole integrated water distributor in water injection oilfields, enabling waterflooding into oil reservoirs. However, the control valve opening cannot be adjusted in the practical environment, resulting in ineffective injection, which means that the spool is stuck. Furthermore, it is difficult to observe the details of the spool sticking and reproduce this phenomenon during testing. To reveal the mechanism of sticking, this paper establishes a CFD model, which considers the spool posture, large fit clearance and outlet shape, to study the spool performance. Additionally, the proposed model is demonstrated experimentally and theoretically. It is found that larger fit clearances result in significant distortion of the flow characteristic curve, with a flow regulation rate of only 90.87% observed when the fit clearance is 0.25 mm. Furthermore, the lateral outlet causes a reduction of 77.27% and 69.15% in radial forces for eccentricity or inclination angles changed from 0° to 180°, respectively. Sticking is strongly correlated with radial forces, the axial force is contingent upon the spool end face area. These findings provide crucial theoretical guidance for the design of control valves.

Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries (LIBs). However, the effect of safety valve type on the thermal runaway (TR) and gas venting behavior of LIBs, as well as the TR hazard severity of LIBs, are not known. In this paper, the TR and gas venting behavior of three 100 A h lithium iron phosphate (LFP) batteries with different safety valves are investigated under overheating. Compared to previous studies, the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types. Two significant results are obtained: (I) the safety valve type dominates over gas venting pressure of battery during safety venting, the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa, which is one order of magnitude higher than other batteries with oval or cavity safety valve; (II) the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process. This study reveals the effect of safety valve type on TR and gas venting, providing a clear direction for the safety valve design.

Digital Manufacturing of Functional Ready-to-Use Microfluidic Systems.

Digital manufacturing (DM) holds great potential for microfluidics, but requirements for embedded conduits and high resolution beyond the capability of common manufacturing equipment, and microfluidic systems' dependence on peripheralshave limited its adoption. Capillaric circuits (CCs) are structurally encoded, self-contained microfluidic systems that operate and self-fill via precisely tailored hydrophilicity. CCs are heretofore hydrophilized in a plasma chamber, but which offers only transient hydrophilicity, lacks reproducibility, and limits CC design to open surface channels subsequently sealed with tape. Here, the additive DM of monolithic, fully functional, and intrinsically hydrophilic CCs is reported. CCs are 3D printed with commonly available light-engine-based 3D printers using poly(ethylene glycol)diacrylate-based ink co-polymerized with hydrophilic acrylic acid crosslinkers and optimized for hydrophilicity and printability. A new, robust capillary valve design and embedded conduits with circular cross-sections that prevent bubble trapping are presented, interwoven circuit architectures created, and CC use illustrated with an immunoassay. Finally, the external paper capillary pumps are eliminated by directly embedding the capillary pump in the chip as a porous gyroid structure, realizing fully functional, monolithic CCs. Thence, a digital file can be made into a CC by commonly available 3D printers in less than 30min enabling low-cost, distributed DM of fully functional ready-to-use microfluidic systems.

Evolving technology: the TRIFLO tri-leaflet mechanical valve without oral anticoagulation: a potential major innovation in valve surgery.

The aortic valve is the most frequently diseased valve and aortic stenosis (AS) is the most prevalent valvular heart disease in developed countries. The diseased native aortic valve can be replaced by either a biological or mechanical valve prosthesis. The main concerns relate to durability, the need for oral anticoagulants and the incidence of complications related to this medication. Experimental, computational and biomolecular blood flow studies have demonstrated that the systolic forward flow but also the reverse flow phase at the end of the systole and leakage during the diastolic phase is mainly responsible for platelet activation and thrombosis. Better design of mechanical prosthetic heart valves must ensure smooth closing during flow deceleration and must eliminate high-shear hinge flow during diastole to prevent life-threatening thrombosis. A novel tri-leaflet valve should combine the favorable hemodynamics and the durability of existing mechanical heart valves and eliminate the less favorable characteristics, including the extremely rapid closing. In this paper, we discuss some issues of current mechanical heart valve prostheses and present a new valve design with the potential for significant innovation in the field. The TRIFLO Heart Valve, is a rigid, three-leaflet central flow heart valve prosthesis consisting of an alloyed titanium housing, and three rigid polymer (PEEK) cusps. This valve has a physiological operating mode. During the forward flow phase, the intraventricular pressure opens the leaflets so that blood can freely flow through with little obstruction, and with the deceleration of the blood flow, the leaflets close early and smoothly, minimizing blood flow regurgitation, blood cell damage, and activation of the coagulation cascade. Pre-clinical studies have shown pretty favorable results and a first-in-man study should start very soon.

A stress-dependent sliding wear model for bileaflet mechanical heart valves

Pyrolytic carbon (PyC) is a common material used in mechanical heart valves. This investigation studies the effects of surface finish on the the sliding wear between two PyC surfaces. The primary application being, the prediction of wear at articulating surfaces within bileaflet mechanical heart valves. An experimental apparatus is designed which allows a cylinder to rotate on a flat plate at a constant frequency and load. The cylinder is harder (greater modulus of elasticity) than the flat surface. Two surface finishes of a single (hard) cylinder and two flat surfaces of different hardnesses (single surface finish) are investigated, for a total of four cases. These four cases are studied at four sliding distances. The exerimental data is used to develop theoretical load and stress-dependent models for sliding abrasive wear. For the boron alloyed PyC material used in this investigation, the load-dependent wear model is most applicable for unpolished cylinders and the stress-dependent model is most applicable for polished cylinders. These two models are used to make theoretical predictions of pivot wear in a bileaflet mechanical valve of the same material. The predictions from the stress-dependent wear model was found to be quite accurate with actual wear measurements. The methods developed in this paper are generalized and applied to other valve designs and materials.

Perfect prosthetic heart valve: generative design with machine learning, modeling, and optimization.

Majority of modern techniques for creating and optimizing the geometry of medical devices are based on a combination of computer-aided designs and the utility of the finite element method This approach, however, is limited by the number of geometries that can be investigated and by the time required for design optimization. To address this issue, we propose a generative design approach that combines machine learning (ML) methods and optimization algorithms. We evaluate eight different machine learning methods, including decision tree-based and boosting algorithms, neural networks, and ensembles. For optimal design, we investigate six state-of-the-art optimization algorithms, including Random Search, Tree-structured Parzen Estimator, CMA-ES-based algorithm, Nondominated Sorting Genetic Algorithm, Multiobjective Tree-structured Parzen Estimator, and Quasi-Monte Carlo Algorithm. In our study, we apply the proposed approach to study the generative design of a prosthetic heart valve (PHV). The design constraints of the prosthetic heart valve, including spatial requirements, materials, and manufacturing methods, are used as inputs, and the proposed approach produces a final design and a corresponding score to determine if the design is effective. Extensive testing leads to the conclusion that utilizing a combination of ensemble methods in conjunction with a Tree-structured Parzen Estimator or a Nondominated Sorting Genetic Algorithm is the most effective method in generating new designs with a relatively low error rate. Specifically, the Mean Absolute Percentage Error was found to be 11.8% and 10.2% for lumen and peak stress prediction respectively. Furthermore, it was observed that both optimization techniques result in design scores of approximately 95%. From both a scientific and applied perspective, this approach aims to select the most efficient geometry with given input parameters, which can then be prototyped and used for subsequent in vitro experiments. By proposing this approach, we believe it will replace or complement CAD-FEM-based modeling, thereby accelerating the design process and finding better designs within given constraints. The repository, which contains the essential components of the study, including curated source code, dataset, and trained models, is publicly available at https://github.com/ViacheslavDanilov/generative_design.

Research on thermal-structural coupling and structural optimization of switching valve in booster system

Turbocharging technology is the second milestone in the development of internal combustion engine, which has become an inseparable part of engine technology and has a significant impact on the power and economy of internal combustion engine. The switching valve is a key component in the sequential turbocharging system, which plays a key role in realizing the energy distribution of the parallel turbocharger, the pressure ratio with different engine conditions, the flow regulation and the matching of the full working conditions. In order to explore the influence of different driving torque, gas pressure and temperature on the switching valve of the pressurization system, the steady-state statics and thermal-structural coupling simulation of the switching valve at room temperature were carried out by ANSYS Workbench software. Based on the central composite design method and Kriging method, the size combination and multi-objective response surface optimization model of 15 groups of switching valve design variables are obtained. Under the same conditions, the multi-objective genetic algorithm is used for simulation calculation. The results show that the deformation of the switching valve mainly occurs on the valve plate and the valve shaft under different driving torque and temperature, and it is symmetrically distributed. The distribution of deformation, stress, contact pressure and friction stress of the switching valve under different driving torques are the same. With the increase of driving torque and temperature, the deformation, stress, contact pressure and friction stress of the switching valve increase gradually, and the temperature effect is the most obvious. Compared with the original design size, the optimized structure size can effectively reduce the contact pressure of the switching valve and significantly improve the service life of the switching valve.

Cavitating Venturi as a Mass Flow Controller in a Deep Throttling Liquid Rocket Engine

Abstract The most common solutions for rocket engines are the single operation point (thrust level) units. Oxidiser and fuel mass flow rates and the oxidiser-to-fuel mass flow rate ratio (OFR) are some of the determinants of the thrust level. Based on these, planetary ascent and descent; space rendezvous; orbital manoeuvring, including orientation and stabilisation in space; hovering, hazard avoidance during planetary landing; and ballistic missile trajectory control propulsion systems could use throttleable liquid engines. Several engine throttling methods, such as supply pressure variation and variable injector area, can be applied. Among others, a cavitating venturi propellant regulatory valve is one of the most promising throttling method. This type of valve can provide steady mass flow, despite the downstream pressure disturbance (i.e. from the combustion chamber), which sustains a stable engine thrust as the mass flow is kept. The article presents the valve sizing method, design and prototype test results of the cavitating venturi valve that has potential for utilisation in a deep throttling rocket engine. Mass flow stability and repeatability are presented for valve operating points in the 10%–110% nominal mass flow range. Valve design optimisation, based on CFD, to sustain cavitation for a higher downstream-to-upstream pressure ratio is shown.

Optimization of Oligomer Stamping Technique for Normally Closed Elastomeric Valves on Glass Substrate.

Microscale elastomeric valves are an integral part of many lab-on-chip applications. Normally closed valves require lower actuation pressures to form tight seals, making them ideal for portable devices. However, fabrication of normally closed valves is typically more difficult because the valve structure must be selectively bonded to its substrate. In this work, an oligomer stamping technique for selective bonding of normally closed valves is optimized for bonding of PDMS devices on glass substrates. Contact angle and blister bursting testing measurements are used to quantitatively characterize the oligomer stamping process for the first time, and recommendations are made for plasma treatment conditions, microstamping technique, and valve construction. Glass-PDMS devices are ideal for lab-on-chip systems that integrate electrodes on the rigid glass substrate. Here, integrated electrodes are used to assess valve performance, demonstrating electrical isolation in excess of 8 MΩ over the biologically relevant frequency range in the closed state. Further, electrical measurement is used to demonstrate that the valve design can operate under a pulsed actuation scheme, sealing to withstand fluid pressures in excess of 200 mbar.

Improving efficiency and optimizing heat transfer in a novel tesla valve through multi-layer perceptron models

Over the past few years, the distinctive design and versatile applications of Tesla valves have captured considerable interest across diverse industries. In contrast to conventional check valves, Tesla valves employ interconnected channels, establishing a highly efficient and reliable fluid flow control mechanism. This research delves into an investigation of the optimum geometric parameters that significantly influence the performance of a novel Tesla valve. The study focuses on three key geometric characteristics: the valve angle (α), the distance between consecutive stages (D), and the distance between the divider wall in the second stage of each step group and the wall of the straight channel (H). The authors carried out a numerical study using computational fluid dynamics to acquire the results. Four multi-layer perceptron models, each with a structure of 3-2-2-1, were applied to predict the selected responses of Nusselt numbers in the forward (Nuf) and reverse (Nur) directions, as well as pressure drops in the forward (ΔPf) and reverse (ΔPr) directions. The findings revealed that among all the variables examined, the parameter H exerted the most substantial influence on all measured responses. It was concluded that by incorporating specific values of α = 34.065°, D = 9 mm, and H = 5.624 mm during the manufacturing process of the valve and altering the flow direction from forward to reverse, a remarkable improvement of approximately 271.7% in pressure diodicity was achieved.