Valve Design Research Articles

Transcatheter Aortic Valve Replacement: Current Status and Future Indications.

In the past two decades, transcatheter aortic valve replacement (TAVR) has transformed the management of aortic stenosis and has become the standard of care regardless of surgical risk levels. Advances in transcatheter valve design across newer generations, improved imaging, greater operator expertise, and technical enhancements have collectively contributed to increased safety and a decline in procedural complications over this timeframe. The application of TAVR has progressively expanded to include younger patients with lower risks, who have longer life expectancies. This article offers an up-to-date review of the latest innovations in transcatheter delivery systems, devices, and its possible future indications.

Patient selection criteria for transcatheter implantation of aortic valve

The aim – to conduct a literature review, analyze and, based on our own results, present an algorithm for choosing the tactics of surgical treatment of patients with severe aortic stenosis.Materials and methods. In this prospective study, the medical records of adult patients (from 18 years of age) who underwent surgical or transcatheter aortic valve replacement at the Heart Institute of the Ministry of Health of Ukraine, between 2018 and 2023 were analyzed.Results. The algorithm for the selection of surgical treatment of patients included in the study was built based on a thorough analysis of the anamnesis, clinical, laboratory and instrumental examination data. An important stage in choosing the optimal surgical tactics is the assessment of the development of intraoperative and postoperative complications according to the EuroSCORE and STS SCORE scales, which are most widely used in cardiac surgery practice and allow predicting the complicated course of the early postoperative period in patients with acquired valvular heart defects. Although there is an increasing trend towards TAVI in younger, lower-risk patients, the more frequent possibility of residual paravalvular insufficiency and the need for permanent pacemaker implantation should be considered. As the experience of interventional cardiologists increases and new valve designs and delivery systems are developed, better clinical outcomes and lower complication rates can be expected, which will contribute to the expansion of indications for TAVI.Conclusions. Today, TAVI remains the only way to correct aortic valve defects for inoperable patients with severe symptomatic aortic stenosis. Based on the results of several randomized controlled trials, TAVI is associated with a much lower rate of postoperative complications and a faster recovery, and should be the method of choice in all high surgical risk patients and a competitive alternative to aortic valve replacement in intermediate risk patients.

Анализ основных направлений снижения интенсивности массовых потоков рабочего тела через неплотности рабочей камеры поршневой длинноходовой тихоходной компрессорной ступени

The working processes and integral characteristics of piston long-stroke low-speed compressor stages are considered. Well-known technologies for increasing the feed rate are considered as objects of comparison: selection of the main dimensions and parameters of the stage; changing the size and design of valves, using elastomeric structural materials; change in the design of the cylinder-piston seal; changing the layout of the suction valve in the working chamber. Indicator efficiency, supply coefficient and tightness coefficient, as well as discharge temperature are considered as integral indicators. The following independent parameters are considered: parameters of the state of the working fluid at suction, discharge pressure, main dimensions and parameters of the stage, distance from the suction valve to the top dead center, seat diameters of the suction and discharge valves, as well as physical and mechanical properties of structural materials. A comparative analysis of the efficiency of the working process of the stage under consideration is carried out using various technologies for reducing the intensity of mass transfer through leaks in the working chamber of a low-speed, long-stroke piston stage. An assessment is made of the achievable value of the feed coefficient with the combined use of various technologies. The features of the working processes of the object under consideration and the relationship between the intensity of mass flows of working gas through leaks in the working chamber of the stage and the technologies used have been studied. The presented results of the theoretical analysis reflect the nature of the change in the integral characteristics of the stage depending on the technologies used to reduce the intensity of mass transfer through leaks in the working chamber of the stage under consideration.

Detekcija udara i poboljšanje dizajna za pneumatski kontrolni ventil

The existence of shockwaves in pneumatic valves can greatly affect their efficiency and cause damage to important parts. This study focuses on the examination of a cost-effective pneumatic directional control valve with the aim of augmenting its output mass flow rate. Emphasis is placed on scrutinizing and modifying the critical flow area to facilitate increased flow rates under specific upstream pressures while eliminating the formation of shockwaves. To achieve these objectives, numerical simulations are harnessed to accurately capture the onset of shockwave formation and elucidate the associated conditions, allowing optimizing valve's capacity without introducing the risk of shockwave occurrence. The modified valve design demonstrated the capability to eliminate shockwave formation within the valve while concurrently increasing the mass flow rate by up to 70% within the same range of inlet pressures. This novel approach holds substantial promise for enhancing system response and represents a significant contribution to the field of pneumatic control valve design.

Design and Analysis of New Hydrogen Oxygen Pneumatic Proportional Reducing Pressure Valve

The pneumatic proportional pressure reducing valve is the main pressure control component in the fuel cell gas supply system, which directly affects the performance of the entire fuel cell system. Based on the research background of the hydrogen oxygen fuel cell gas supply system, a set of pneumatic proportional pressure reducing valves suitable for hydrogen oxygen gas environments was designed. Through structural design and multi-parameter analysis, the structural parameter design optimization and characteristic analysis of the proportional valve were proposed. It can provide high-precision and high stability gas control capabilities for fuel cell systems, and provide support for engineering applications.

Приготовление растворов различной концентрации

When preparing treatment solutions of fertilizers and pesticides for technological processes, one should mix liquids taking into account the precise dosing of components. However, the existing designs of dosing and mixing devices do not provide qualitative dosing. Moreover, a sharp increase of fraction quantity may result in a hydraulic impact. To eliminate these disadvantages, based on analytical research of available designs and patent search results, the authors worked out a mixer for preparing solutions of various concentrations. The device is also capable of changing the ratio of components in the process of operation. The device provides smooth change of preparation concentrations due to the design of dosing valves forming square-shaped ports with a changing configuration. The port plates move relative to each other both horizontally and vertically. The proposed device smoothly changes the concentration of the solution, thereby providing for more accurate dosing. It was experimentally found that a smoother change in the flow rate of treatment liquid according to the solution concentration is observed at a distance from the axes of symmetry of the dosing device disks to the rotation axis of the distribution ports, equal to 0.04 to 0.1 m. The deviation of the actual treatment liquid flow rate from the calculated one does not exceed 5%. The integration of the developed mixer into the systems of fertigation units, sprayers and other specialized machines will ensure better quality of the fine irrigation of plants, seeds, and soil.

Design, manufacturing and testing of a green non-isocyanate polyurethane prosthetic heart valve.

The sole effective treatment for most patients with heart valve disease is valve replacement by implantation of mechanical or biological prostheses. However, mechanical valves represent high risk of thromboembolism, and biological prostheses are prone to early degeneration. In this work, we aim to determine the potential of novel environmentally-friendly non-isocyanate polyurethanes (NIPUs) for manufacturing synthetic prosthetic heart valves. Polyhydroxyurethane (PHU) NIPUs are synthesized via an isocyanate-free route, tested in vitro, and used to produce aortic valves. PHU elastomers reinforced with a polyester mesh show mechanical properties similar to native valve leaflets. These NIPUs do not cause hemolysis. Interestingly, both platelet adhesion and contact activation-induced coagulation are strongly reduced on NIPU surfaces, indicating low thrombogenicity. Fibroblasts and endothelial cells maintain normal growth and shape after indirect contact with NIPUs. Fluid-structure interaction (FSI) allows modeling of the ideal valve design, with minimal shear stress on the leaflets. Injection-molded valves are tested in a pulse duplicator and show ISO-compliant hydrodynamic performance, comparable to clinically-used bioprostheses. Poly(tetrahydrofuran) (PTHF)-NIPU patches do not show any evidence of calcification over a period of 8 weeks. NIPUs are promising sustainable biomaterials for the manufacturing of improved prosthetic valves with low thrombogenicity.

A Novel Design and Simulation of a Nano Prosthetic Artificial Heart Valves

A Novel Design and Simulation of a Nano Prosthetic Artificial Heart Valves

High-pressure homogenizer valve design modifications allowing intensified drop breakup without increasing power consumption. I. Optimization of current design-principle

This study uses a model-based design approach (CFD coupled to well-established emulsification correlations) to investigate how to choose the valve dimensions of a high-pressure homogenizer so as to achieve intensified drop breakup without increasing the power consumption. Results show how design modifications influence the thermodynamic efficiency of the homogenizer via two effects, a friction factor and a factor related to how high a dissipation rate of turbulent kinetic energy that the design delivers in the centre of the jet. By simple design modifications, thermodynamic efficiency can be increased by 4 % (compared to a representative contemporary valve design) by decreasing the inlet chamber angle, and an additional 5 % by carefully adjusting the outlet chamber angles so as to ensure that the jet exits the gap free of the wall, but then bends and re-attaches to the wall further downstream. The modifications are predicted to allow for achieving the same resulting drop size but with a 17 % lower power draw, compared to a standard contemporary valve, or alternatively a smaller resulting drop diameter at constant power draw.

Remote-Controlled Affordable Solenoid Valve Design and a Web-Based Approach to Its Implementation

Irrigating agricultural lands remotely using automated irrigation systems can mitigate water and energy wastage, reducing it to a minimum. This study aims to design an agricultural irrigation system that operates by remotely opening and closing solenoid valves. The envisioned solenoid valve comprises a wireless microcontroller, a power circuit, and a basic valve mechanism. The remote and automated irrigation system can monitor and receive commands for the connected solenoid valves through web services and a web interface. After every operation executed by the system, interfaces displaying the real-time status or historical operational states of the controlled solenoid valves are presented to the users. This system is orchestrated using a web server operating on a cloud server, serving as the system control center. Solenoid valves positioned at ten different points are integrated, facilitating real-time and programmable use based on user requests. The system uses a secured website, accessed via user passwords, as a communication interface to receive irrigation control requests. It offers the capability for multiple users to control the system simultaneously through the same interface. Ultimately, this research seeks to establish a secure, remote, and automated irrigation system based on the control and scheduling of low-cost solenoid valves via a web page.

Long-Term Survival Benefits of Porcine versus Pericardial Bioprostheses in Elderly Patients Undergoing Isolated Aortic Valve Replacement: A 32-Year Study.

The elderly population is growing at an unprecedented rate. Aortic valve disease increases with age. Bioprostheses are the valves of choice for older patients; however, the optimal tissue valve remains undetermined. The purpose of this investigation was to perform a life-of-patient survival comparison of the prototypical porcine and pericardial prostheses in elderly patients. The study population (N = 1480) consisted of patients 65 years of age and older who underwent isolated aortic valve replacement from 1990 through 2005 with a Carpentier-Edwards Porcine (n = 650) or Pericardial (n = 830) bioprosthesis. Propensity score-matched groups were created. Valve selection was not associated with operative mortality. Survival estimates at 10 years were better for Pericardial (41.8%; 95% CI: 37.9 to 45.7) than Porcine (32.6%; 95% CI: 28.8 to 36.3); and 5.2% (95% CI: 3.2 to 7.1) versus 2.0%; (95% CI: 0.8 to 3.2) at 20 years (p < 0.001). E-value analysis found minimal influence of unknown study confounders. Factors associated with long-term mortality were porcine valve (p < 0.001), age (p < 0.001), diabetes mellitus (p < 0.001), preop renal insufficiency (p < 0.001), peripheral artery disease (p = 0.011), congestive heart failure (p = 0.003), New York Heart Association Class III or IV (p = 0.004), surgical history-reoperation (p = 0.012), transient ischemic attack (p = 0.009), prolonged ventilation (p = 0.010), postop renal insufficiency (p < 0.001), and atrial fibrillation (p = 0.009). The indexed Effective Orifice Area (EOAi) was assessed and did not influence observed long-term survival differences. This unusual lifetime study provided substantial evidence for the superiority of the pericardial over the porcine bioprosthesis in the aortic position in elderly patients. It demonstrated enhanced long-term survival benefits for elderly patients without any increase in perioperative mortality. It is intended to inform future investigation into aortic valve design.

An embedded microfluidic valve for dynamic control of cellular communication.

The communication between different cell populations is an important aspect of many natural phenomena that can be studied with microfluidics. Using microfluidic valves, these complex interactions can be studied with a higher level of control by placing a valve between physically separated populations. However, most current valve designs do not display the properties necessary for this type of system, such as providing variable flow rate when embedded inside a microfluidic device. While some valves have been shown to have such tunable behavior, they have not been used for dynamic, real-time outputs. We present an electric solenoid valve that can be fabricated completely outside of a cleanroom and placed into any microfluidic device to offer control of dynamic fluid flow rates and profiles. After characterizing the behavior of this valve under controlled test conditions, we developed a regression model to determine the required input electrical signal to provide the solenoid the ability to create a desired flow profile. With this model, we demonstrated that the valve could be controlled to replicate a desired, time-varying pattern for the interface position of a co-laminar fluid stream. Our approach can be performed by other investigators with their microfluidic devices to produce predictable, dynamic fluidic behavior. In addition to modulating fluid flows, this work will be impactful for controlling cellular communication between distinct populations or even chemical reactions occurring in microfluidic channels.

Automated multi-functional system for the characterization of plate valves in reciprocating compressors

At present, there are two independent technologies and equipment for the test of the reciprocating compressor plate valve: the sealing test and blowing test. This method has single function and complicated test operation and may rely on theoretical calculations, which reduces the reliability of the test conclusion because the motion law of valve disk during opening and closing is extremely complicated. The existing test methods cannot meet the needs of more in-depth and accurate research, development and improvement of the plate valve. This study proposes a test device and method that can not only quantitatively test the performance of the plate valve but also qualitatively test the dynamic process of the suction valve plate, which can greatly reduce the testing time provide more intuitive and accurate valve plate motion tracks and valve paths. This paper takes the primary plate suction valve as the test object and adopts the automated multi-functional system to accurately obtain the valve’s sealing property, effective flow area, thrust coefficient, flow coefficient, drag drop, valve gap Mach number, initial opening pressure difference, maximum opening, and residence time of the valve plate on the valve lift guard to provide necessary data for valve design and performance evaluation. The test results of valve opening time are verified by industrial reciprocating compressor, which proves the accuracy and practicability of the system.

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.