Flat Valve Research Articles

Compressible Flow Through Flat Valve Seals at Microscale Displacements

Abstract Existing analytical flow models for predicting flow rates at microscale seal displacements are limited to two separate domains. The first assumes a small channel length to height aspect ratio at relatively large seal displacements. The second assumes a large channel length to height aspect ratio at relatively small seal displacements. A piecewise analytical model for compressible flow is developed here to enable predicting flow rates in valves with fluid pathways of any aspect ratio. The new model is validated by numerical studies and experiment. The results are applicable to flat valve seals having a cylindrical seal boss feature with fluid passage length to height aspect ratios ranging from 3.3 to 800. The new model is particularly useful for the design of microvalves and macroscale valves with small actuator displacements.

Research on Bearing Mechanism of Spherical Valve Pairs of Axial Piston Pumps

The hydraulic system drives the cutter head mechanism to realize the excavation of large tunnel boring equipment, which puts forward the technical requirements of high pressure and large flow to the pump source. The traditional small displacement axial piston pump uses a planar valve plate. However, under high flow and heavy load conditions, the planar valve plate configuration is prone to uneven wear due to the high-pressure and -velocity (PV) value and pressure shock, which ultimately affects the reliability of the system. A simulation analysis of the load-bearing characteristics of the spherical valve plate mechanism is conducted. The Computational Fluid Dynamics (CFD) method was used to construct flow field models for different valve plate oil film structures to calculate differences in their load-bearing capacities. Additionally, the reasons for variations in load-bearing characteristics based on the curvature radius of the spherical valve plate were analyzed. The simulation results demonstrate that the spherical valve plate exhibits superior leak and load-bearing performance compared to the traditional flat valve plate. Furthermore, the curvature radius of the spherical valve plate directly affects the pulsation characteristics of the piston pump. Smaller curvature radii increase the contact area of the oil film, resulting in greater fluctuation in oil film load-bearing, whereas larger curvature radii lead to increased oil film leakage. Using simulation calculations on heavy-load, high-displacement axial piston pumps, it is determined that the optimal curvature radius for stable load-bearing is 350 mm.

Reducing Automotive Cooling System Complexity through an Adaptive Biomimetic Air Control Valve.

Future automotive mobility is predominantly electric. Compared to existing systems, the requirements of subsystems change. Air flow for cooling components is needed predominantly when the car is in rest (i.e., charging) or at slow speeds. So far, actively driven fans consuming power and generating noise are used in this case. Here we propose a passive adaptive system allowing for convection-driven cooling. The developed system is a highly adaptive flat valve derived from the bordered pit. It was developed through an iterative design process including simulations, both structural and thermodynamic. In hardwoods and conifers, bordered pits enable the challenging transport of vertical fluids by locally limiting damage. Depending on the structure, these can close at sudden pressure changes and take the function of valves. The result of the biomimetic abstraction process is a system-integrative, low-profile valve that is cheap to produce, long-lasting, lightweight, maintenance-free, and noise-free. It allows for the passive switching of air flow generation at the heat exchanger of the cooling between natural convection or an active airstream without the need for complex sensing and control systems. The geometric and material design factors allow for the simple tuning of the valve to the desired switching conditions during the design process.

Transcriptional responses to salinity-induced changes in cell wall morphology of the euryhaline diatom Pleurosira laevis.

Diatoms are unicellular algae with morphologically diverse silica cell walls, which are called frustules. The mechanism of frustule morphogenesis has attracted attention in biology and nanomaterials engineering. However, the genetic regulation of the morphology remains unclear. We therefore used transcriptome sequencing to search for genes involved in frustule morphology in the centric diatom Pleurosira laevis, which exhibits morphological plasticity between flat and domed valve faces in salinity 2 and 7, respectively. We observed differential expression of transposable elements (TEs) and transporters, likely due to osmotic response. Up-regulation of mechanosensitive ion channels and down-regulation of Ca2+-ATPases in cells with flat valves suggested that cytosolic Ca2+ levels were changed between the morphologies. Calcium signaling could be a mechanism for detecting osmotic pressure changes and triggering morphological shifts. We also observed an up-regulation of ARPC1 and annexin, involved in the regulation of actin filament dynamics known to affect frustule morphology, as well as the up-regulation of genes encoding frustule-related proteins such as BacSETs and frustulin. Taken together, we propose a model in which salinity-induced morphogenetic changes are driven by upstream responses, such as the regulation of cytosolic Ca2+ levels, and downstream responses, such as Ca2+-dependent regulation of actin dynamics and frustule-related proteins. This study highlights the sensitivity of euryhaline diatoms to environmental salinity and the role of active cellular processes in controlling gross valve morphology under different osmotic pressures.

Development of a pneumatic actuated low-pressure direct injection gas injector for hydrogen-fueled internal combustion engines

Mixture formation is one of the greatest challenges for the development of robust and efficient hydrogen-fueled internal combustion engines. In many reviews and research papers, authors pointed out that direct injection (DI) has noteworthy advantages over a port fuel injection (PFI), such as higher power output, higher efficiency, the possibility of mixture stratification to control NOx-formation and reduce heat losses and above all to mitigate combustion abnormalities such as back-firing and pre-ignitions. When considering pressurized gas tanks for on-vehicle hydrogen storage, a low-pressure (LP) injection system is advantageous since the tank capacity can be better exploited accordingly. The low gas density upstream of the injector requires cross-sectional areas far larger than any other injectors for direct injection in today's gasoline or diesel engines. The injector design proposed in this work consists of a flat valve seat to enable the achievement of lifetime requirements in heavy-duty applications. The gas supply pressure is used as the energy source for the actuation of the valve plate by means of a pneumatic actuator. This article describes the design and the performed tests carried out to prove the concept readiness of the new LP-DI-injector.

Aortic valve morphology and the double envelope phenomenon in continuous Doppler echocardiography of aortic stenosis: a computerized model

Abstract Introduction Visualization of a double envelope (DE) is a relatively common issue in aortic transvalvular continuous-wave Doppler (CW) traces. In 1997, Song et al proposed that velocity time integral (VTI) measured at the edge of the inner envelope (IE) might equal that of the left ventricular outflow tract (LVOT). This surrogate measurement would be especially interesting in patients with irregular heart rhythms, as both LVOT and valvular VTIs could be obtained from the same beat, thus avoiding inter-beat variability when assessing aortic valve area (AVA) with continuity equation. In contrast, based on clinical data and 3D-printed models, they raised concern that DE method in dome-shaped valves could lead to significant overestimation of LVOT velocities (about 40%). Later studies, including a Partner trial subanalysis, question the validity of this measurement. Purpose We created a computerized aortic valve model to reproduce the CW tracing, and analysed how valve morphology may lead to a valid, well defined inner envelope or, by contrast, produce overestimation of LVOT velocities. Methods The simulation code was created using Python (v3.9.6) along with NumPy and Matplotlib libraries. For each simulation, an aortic valve scheme was created (LVOT diameter: 2 cm; TSVI length: 1 cm; LVOT peak velocity 1.1 m/s; varying morphologies and lengths of the aortic cusps). The longitudinal axis between LVOT base and valve tip was divided in sections or levels (at least 300 per emulation). To recreate the CW trace, for each level, luminal diameter and peak velocity (according to continuity equation) were calculated, and an array of points was generated representing the aortic waveform during the entire systole. Slight random dispersion (standard deviation 0.05 times original values) was added to produce a more realistic image. Data points were represented as scatter plot over black background with transparency, simulating CW tracings (Figure 1) Results Figure 2 represents the plots of various aortic valve configurations (1st row AVA 1.6 cm2; 2nd: 1.2 cm2; 3rd: 0.8 cm2). Note that the innermost portion of the trace results in hollow space, as these velocities are produced in portions of ventricle and aorta which are not included in the simulation. Pink dashed line represents actual LVOT velocities. In a short-length flat valve (A), the IE is well defined and shows good correlation with LVOT velocity. In a cone-shaped 6mm length valve (B), there is a progressive brightness reduction, with no recognizable contour. With long (6 mm) dome-shaped valves, an ill-defined IE is produced at higher velocities than LVOT, which could result in overestimation. Conclusion DE method could accurately assess LVOT velocities when a sharp-defined IE is present and a dome-shaped valve can be excluded (e.g. rheumatic or some bicuspid valves). Measurements in a blurred DE or in a dome-shaped valve would produce overestimation of LVOT velocities and AVA. Funding Acknowledgement Type of funding sources: None.

Two new Staurosirella species (Staurosiraceae, Bacillariophyta) observed in an historic Rabenhorst sample

During a survey of some exsiccata samples from Rabenhorst’s Die Algen Sachen’s und Europa’s, two Staurosirella taxa that could not be identified using the currently available literature were observed in a sample from the Swiss Alps, collected in 1863 CE. The two taxa occurred together with a large population of S. neopinnata and were studied using detailed light and scanning electron microscopy. Based on the obtained observations on their morphology, and after comparing both taxa with all currently known Staurosirella and some Staurosira species, both are described as new. Staurosirella coutelasiana Van de Vijver sp. nov. is characterized in having a linear-lanceolate to lanceolate, isopolar valve outline with small apical pore fields on both apices. The second new species, S. minutissima Van de Vijver sp. nov., is a small-celled Staurosirella species and possesses short lineolae, an almost flat valve surface and small apical pore fields. Both species are extensively illustrated and discussed. Their ecological preferences are derived from the associated diatom flora in the sample and point to oligotrophic, calcium-carbonate rich, oligosaprobic conditions.

Scaling of Droplet Breakup in High-Pressure Homogenizer Orifices. Part I: Comparison of Velocity Profiles in Scaled Coaxial Orifices

Properties of emulsions such as stability, viscosity or color can be influenced by the droplet size distribution. High-pressure homogenization (HPH) is the method of choice for emulsions with a low to medium viscosity with a target mean droplet diameter of less than 1 µm. During HPH, the droplets of the emulsion are exposed to shear and extensional stresses, which cause them to break up. Ongoing work is focused on better understanding the mechanisms of droplet breakup and relevant parameters. Since the gap dimensions of the disruption unit (e.g., flat valve or orifice) are small (usually below 500 µm) and the droplet breakup also takes place on small spatial and time scales, the resolution limit of current measuring systems is reached. In addition, the high velocities impede time resolved measurements. Therefore, a five-fold and fifty-fold magnified optically accessible coaxial orifice were used in this study while maintaining the dimensionless numbers characteristic for the droplet breakup (Reynolds and Weber number, viscosity and density ratio). Three matching material systems are presented. In order to verify their similarity, the local velocity profiles of the emerging free jet were measured using both a microparticle image velocimetry (µ-PIV) and a particle image velocimetry (PIV) system. Furthermore, the influence of the outlet geometry on the velocity profiles is investigated. Similar relationships were found on all investigated scales. The areas with the highest velocity fluctuations were identified where droplets are exposed to the highest turbulent forces. The Reynolds number had no influence on the normalized velocity fluctuation field. The confinement of the jet started to influence the velocity field if the outlet channel diameter is smaller than 10 times the diameter of the orifice. In conclusion, the scaling approach offers advantages to study very fast processes on very small spatial scales in detail. The presented scaling approach also offers chances in the optimization of the geometry of the disruption unit. However, the results also show challenges of each size scale, which can come from the respective production, measurement technology or experimental design. Depending on the problem to be investigated, we recommend conducting experimental studies at different scales.

New fossil genus and new extant species of diatoms (Stephanodiscaceae, Bacillariophyceae) from Pleistocene sediments in the Neotropics (Guatemala, Central America): adaptation to a changing environment?

Several taxa of Stephanodiscaceae were found in the upper section of Pleistocene sediments from Lake Petén-Itzá (Guatemala). A new fossil genus Cyclocostis Paillès gen. nov. and new extant species Discostella gabinii Paillès & Sylvestre sp. nov. are described. Cyclocostis gen. nov. is characterized by a strongly tangentially undulated valve surface, coarse unequal striation reaching a central punctum in the valve center, an absence of central lamina and domed criba, widely open alveoli with one median recessed costa bearing marginal fultoportulae and a single rimoportula all within a ring. A single valve face fultoportula is present on the raised part of the valve opposite the rimoportula. Differences relative to similar genera and the delimitation of a new genus are discussed. Discostella gabinii sp. nov. is distinguished by circular and flat valves, a small central area bearing 5 to > 30 scattered large areolae giving a colliculate appearance, medium-sized alveoli, marginal fultoportulae on every 4–5th costa, a single rimoportula and internally smooth valve center. Differences to similar taxa in the genus Discostella are discussed. The succession of the species of Cyclotella, Discostella and Cyclocostis gen. nov. in our record could represent eco-phenotypic responses to particular environmental stress / change.

Design & Simulation of a Superimposed Hydraulic Back Pressure Valve with Adaptive Back Pressure

A superimposed hydraulic back pressure valve with adaptive back pressure was designed. The back pressure of the valve changes as the diving depth of underwater vehicles changes, and is always higher than outboard environmental pressure by an adjustable value, preferred 0.5MPa, to avoid leakage of environmental medium to the inboard hydraulic system. The valve was designed in a pilot-operated style with a flat valve port of main valve. Variable damping plugs were used to easily regulate the dynamic performance of the valve. And an isolation device was adopted to isolate the contact between the inboard and outboard media. The static mathematic models of the valve were established and simulations were carried out. The simulation results show the valve has good pressure stability and flow adaptability, and its back pressure changes with the change of outboard pressure well.

Re-examination of Cyclotella lacunarum Hustedt (Bacillariophyta) from lakes in the Pamir Mountains, western China, and description of two similar Lindavia taxa collected from Tajikistan and Nepal

Originally described from a sample collected in the Pamir Mountains at the end of the nineteenth century, Cyclotella lacunarum Hustedt is a centric diatom species that is not-well defined and seldom reported in the scientific literature. Our investigations revealed that the type locality of this taxon, now referred to as Lindavia lacunarum (Hustedt) Nakov et al., is actually in western China and not in Tajikistan, as wrongly assumed previously. Light microscope (LM) and scanning electron microscope (SEM) observations of the type material and of modern material collected at the type locality allowed us to emend the description of this species. Its most remarkable character is that it possesses central fultoportulae with only two satellite pores instead of three as generally reported for similar species of Lindavia. Lindavia lacunarum was then compared to two similar populations of Lindavia collected from high elevation lakes in Tajikistan and Nepal. These two populations were originally identified as Cyclotella/Lindavia lacunarum and represent the only reported occurrences of this taxon outside its type locality. The population from Tajikistan differs from L. lacunarum by having cells of smaller size, with an almost flat valve face and has been described as a new variety Lindavia lacunarum var. karakulensis var. nov. The Nepalese population is more clearly differentiated from L. lacunarum by having a different type of colliculate pattern in the central area and significantly lower density of central fultoportulae and is therefore described as a new species, Lindavia nepalensis sp. nov.

Design & Simulation of a Hydraulic Back Pressure Valve with a Large Flow Range

A hydraulic back pressure valve with a large flow range up to not less than 100L/min was designed. In order to meet the requirements of low cracking pressure and large applicable flow range, the valve was designed in a pilot operated style with a flat valve port of main valve. Area difference between the front and rear of main spool was adopted to keep the valve port self-sealing and adjustable damping plugs were used to easily regulate the dynamic performance of the valve. The mathematic models of the valve were established and simulations were carried out. Then, the influences of some major structural parameters such as volume before main throttle, volume of main spring chamber, dimensions of slender holes of damping plugs and the main throttle were obtained. The simulation results show that the valve has good flow adaptability, and the pressure shock can be cut down remarkably by reasonably setting the parameters.

The Erosion-Corrosion Behaviors of the Full-Scale PFF78-70 Flat Valve and P110SS Tubing

In the present work, a self-built device called “full scale tubular goods erosion-corrosion test system” was used to test the P110SS tubing with a total length of 10 m and a full scale PFF78-70 flat valve to study their erosion-corrosion behaviors in the acceleration simulation operating condition of a well in Sichuang oil field of China. The erosion-corrosion performance of the specimen was investigated by KH-7700 digital microscope, scanning electron microscopy (SEM), X-ray power diffraction (XRD) and energy-dispersive spectroscopy (EDS). The results indicated that the P110SS tubing suffered catastrophic erosion-corrosion; the maximum pitting corrosion rate of the P110SS in the gas phase fluid was 5.29mm/a; while that in the liquid phase fluid was 11.13mm/a; A double-layer corrosion products scale, inner FeCO3 layer and outer mixture layer mainly dominated by FeO, Fe3O4, Fe2O3 and FeO(OH), formed on the P110SS tubing. Erosion-corrosion only occurred in the stress concentration area of the valve plate hole of the PFF78-70 plate valve, and the size of the corrosion pits is about 0.5mm.

A transmissibility-based approach to identifying the dynamic behavior of a seawater hydraulic piston pump under pressure excitation

An investigation into the dynamic behavior of the piston pump is an important method to reduce its vibration and noise. In this paper, an approach to predict the dynamics of a seawater hydraulic piston pump (SWHPP) from output-only transmissibility measurements is introduced. In order to eliminate the harmonic interference generated by spindle rotation, the excitation in this method is the pressure which caused by the SWHPP operating at a constant speed and under different loading conditions. The first four modes of the SWHPP were estimated utilizing the method proposed in this paper, and the influence of the pressure on the dynamics of the SWHPP structure was further studied. The experimental results indicated that peak occurred around the frequency of 20 Hz, and the reason is that the estimated second-order natural frequency (19.8 Hz) is near to the frequency of 20 Hz which is the excitation frequency of the swash plate and the flat valve of the SWHPP. In addition, this method can identify modal parameters of the piston pump structure in the working state, so it can effectively predict the dynamic behaviors of the piston pump.

DEVELOPMENT AND OPTIMIZATION OF A LINEAR-MOTOR-DRIVEN WATER HYDRAULIC PISTON PUMP

This research develops a new piston pump driven by four double-action linear motors (abbr. FDLMP). The working principle of FDLMP is introduced, and the theoretical models of flow rates, effects of motion planning, and hysteresis of flat valve on pulsation ratio of combination flow rate of the piston pump are investigated systematically. The simulation and test results showed that the key design parameters such as the clearance of piston sector, spring preloading and stiffness of suction valve play important roles in the improvement of volumetric efficiency and flow pulsation rate of FDLMP. These research works lay the foundation for the further development of FDLMP.

Gerontic Intraspecific Variation in the Antarctic BivalveRetrotapes antarcticus

Abstract. The bivalve Retrotapes antarcticus, from the Eocene of Antarctica, includes two different morphotypes of which one presents flat valves while the other one exhibits globoid valves. Previous authors have identified the same two morphotypes in the extant species Retrotapes exalbidus. This paper assesses the flat versus globoid morphotypes via comparing the two species by analyzing Elliptic Fourier Contours of 17 valves of R. antarcticus and 40 valves of R. exalbidus. A principal component analysis was performed and the age of both morphotypes was estimated by way of counting growth lines. Several authors have argued that genetic differences between the two forms of R. exalbidus are not sufficient to separate them into two distinct species and suspected that the globoid morphotype may correspond to gerontic specimens. Our results demonstrate that the morphological transformation detected in R. antarcticus is similar to that observed in R. exalbidus. The analysis of growth lines confirms that the gl...

Two new Platessa (Bacillariophyceae) from Amazonia: Platessa guianensis spec. nov., and P. itoupensis spec. nov.

Recent investigations in the deep rainforest of Amazonia in French Guiana and in the north of Brazil revealed the presence of two new Platessa species. Detailed light (LM) and scanning electron microscope (SEM) observations were used to describe the morphology and the ultrastructure of these new monoraphid diatoms, Platessa guianensis and P. itoupensis. They display the taxonomic features characteristic of the genus Platessa, namely almost flat valves, straight raphe fissures and uni- to multiseriate striae with specific features such as the ornementation of the striae and the morphology of the groove surrounding the raphe endings. These two Platessa are the first ones described from Amazonia. They are compared with the two types of two similar species described originally from Indonesia (i.e. Platessa brevicostata and Platessa cataractarum) whose original materials are also here re-illustrated in LM and SEM. The taxonomical diagnosis is completed with comments on ecology issues. In addition, we proposed the recombination of three Achnanthes into Platessa based on published literature.

Chelonicola and Poulinea, two new gomphonemoid diatom genera (Bacillariophyta) living on marine turtles from Costa Rica

Marine mammals such as whales and dolphins have been known for a long time to host a very specific epizoic community on their skin. Less known however is the presence of a similar community on the carapaces of sea turtles. The present study is the first describing new taxa inhabiting sea turtle carapaces. Samples, collected from nesting olive ridley sea turtles (Lepidochelys olivacea) on Ostional Beach (Costa Rica), were studied using light and scanning electron microscopy. Two unknown small-celled gomphonemoid taxa were analysed in more detail and are described as two new genera, closely related to other gomphonemoid genera with septate girdle bands, such as Tripterion, Cuneolus and Gomphoseptatum. Chelonicola Majewska, De Stefano & Van de Vijver gen. nov. has a flat valve face, uniseriate striae composed of more than three areolae, simple external raphe endings, internally a siliceous flap over the proximal raphe endings and lives on mucilaginous stalks. Poulinea Majewska, De Stefano & Van de Vijver gen. nov. has at least one concave valve, uniseriate striae composed of only two elongated areolae, external distal raphe endings covered by thickened siliceous flaps and lives attached to the substrate by a mucilaginous pad. Chelonicola costaricensis Majewska, De Stefano & Van de Vijver sp. nov. and Poulinea lepidochelicola Majewska, De Stefano & Van de Vijver sp. nov. can be separated based on stria structure, girdle structure composed of more than 10 copulae, raphe structure and general valve outline. A cladistics analysis of putative members of the Rhoicospheniaceae indicates that the family is polyphyletic. Chelonicola and Poulinea are sister taxa, and form a monophyletic group with Cuneolus and Tripterion, but are not closely related to Rhoicosphenia, or other genera previously assigned to this family. Features used to help diagnose the family such as symmetry and presence of septa and pseudosepta are homoplastic across the raphid diatom tree of life.

Simultaneous in- and out-of-plane Mitral Valve Annular Force Measurements.

Mitral valve repair with annuloplasty is often favoured over total valve replacement. In order to develop and optimize new annuloplasty ring designs, it is important to study the complex biomechanical behaviour of the valve annulus and the subvalvular apparatus with simultaneous in- and out-of-plane restraining force measurements. A new flat D-shaped mitral valve annular force transducer was developed. The transducer was mounted with strain gauges to measure strain and calibrated to provide simultaneous restraining forces in- and out of the mitral annular plane. The force transducer was implanted and evaluated in an 80kg porcine experimental model. Accumulation of out-of-plane restraining forces, creating strain in the anterior segment were 0.7±0.0N (towards apex) and an average force accumulation of 1.5±0.3N, creating strain in the commissural segments (away from apex). The accumulations of in-plane restraining forces, creating strain on the inner side of the ring were 1.7±0.2N (away from ring center). A new mitral annular force transducer was successfully developed and evaluated in vivo. The transducer was able to measure forces simultaneously in different planes. Initial indications point towards overall agreement with previous individual force measurements in- and out-of the mitral annular plane. This can provide more detailed insight into the annular force distribution, and could potentially improve the level of evidence based mitral valve repair and support the development of future mitral annuloplasty devices.

PARADOX OF DRILLED DEVIL'S TOENAILS: TAPHONOMIC MIXING OBSCURES CRETACEOUS DRILLING PREDATION IN UTAH OYSTERS

ABSTRACT Pycnodonte newberryi oysters accumulated in voluminous shell beds of Late Cretaceous (late Cenomanian) age in shale deposits of the Western Interior Seaway. Analysis of triplicate grid samples from six shell beds in southern Utah shows that the reclining valves of the oyster are disproportionately represented by the inflated left valve, eight times more often than the smaller, flat right valve, and whole valves are rare. The shells nearly always fragment from the commissure toward the thick umbonal half of the shell. These fragmented shells make up more than half of grid samples, and only 0.5% contain predatory drillholes. By contrast, complete shells are drilled nearly 5% of the time, particularly near the umbo. Fragmentation cannot account for this discrepancy because the preponderance of drillholes occurs in the umbonal part of the shell, the part that is always preserved. To understand this paradox, drilled Pycnodonte were collected from a separate site in Utah and drillhole position on the s...