Ring Profile Research Articles

Kinematics and geometrical admissibility conditions of balanced vane pumps with twin lip vanes

The present work is devoted to analyze the kinematics of twin lip vanes adopted in balanced vane pumps. The work provides the analytical description of the vane motion according to its geometrical parameters and the cam ring profile. Attention is given to the duality of the solution, an intrinsic property of twin lip vanes that may be considered as followers with two symmetrical half-circular tips. Based on the linkage kinematics, the analytical dissertation is further deepened to define the geometrical admissibility of the vane design and its mathematical domain. In order to evaluate the proposed approach, an extended parametric study is performed on the basis of the Buckingham theorem, detailing how the twin lip configuration affects the machine kinematics. Additional calculations are proposed to determine the vane design configurations that satisfy the fundamental law of cam design and to highlight how this requirement dramatically reduces the subset of available choices in presence of cam ring with a precompression profile. Finally, design guidelines are proposed in order to overcome these drawbacks and expand the admissibility domain.

Adjustable ring shaping for laser welding applications

AbstractHigh laser welding speed can be achieved by using a ring and central spot laser illumination profile, with an adjustable ratio of the ring energy to the spot enabling optimization of the process. We present a novel and simple diffractive‐based concept to achieve such adjustable shaping for standard fiber lasers. The module is rotation‐adjustable between 100 % energy in the central spot to no energy in the central spot, can work with both single‐mode and multimode lasers, is highly compact (less than 20 mm long) and has the high LDT of passive diffractive components. This concept obviates the need for special ring‐type fiber lasers, enabling simpler design of the welding laser head.

Stable propagation of cylindrical-vector vortex solitons in strongly nonlocal media.

We report the experimental observation of cylindrical-vector vortex solitons (CVVSs) in lead glass with strongly thermal nonlocal nonlinearity. The formations of radially and angularly polarized solitons with topological charge of $l = 1$ were observed. We show that the ring profiles and the polarization distributions of the two first-order CVVSs can be preserved. We numerically prove that the first-order CVVS is stable, and the higher-order CVVSs with $l \ge 2$ are unstable based on the linear stability analysis method.

Analysis of the Influence of Textured Surfaces and Lubrication Conditions on the Tribological Performance between the Compression Ring and Cylinder Liner

The objective of the present investigation is to analyze the tribological performance between the union of the cylinder liner and the compression ring under the influence of surface texturing and different lubrication boundary conditions. The analysis is carried out by developing a numerical model, which involves hydrodynamic pressure, lubrication film thickness, textured surface, dynamic forces, and lubrication boundary conditions (starved lubrication and fully flooded lubrication). MATLAB® software (The MathWorks Inc., Natick, MA, USA) is used to solve the equations developed. The results show that the application of a textured surface on the cylinder liner allows obtaining a reduction of 20% and 5% in the asperity contact force and in the total friction force. Additionally, the textured surface allows for a 4% increase in MOFT. In this way, it is possible to reduce the power loss. The implementation of a boundary condition of fully flooded lubrication produces an overestimation in the total friction force due to the greater prominence of the lubrication film. Implementing a textured surface in the ring profile is an alternative way to reduce power loss. The results show that this alternative allows an 8% reduction in power loss.

Investigation of cavity filling in profile ring rolling process for T-shape ring

In this paper, key parameters affecting the cavity filling in single and double T-shape profile rings are comprehensively investigated via numerical and experimental analysis. A three-dimensional finite element model was developed in Abaqus\Explicit to assess the influence of crucial ring rolling process parameters, including feed speed, main roll rotational velocity, the existence and the absence of axial rolls on the cavity filling of single and T-shape rings and the main roll torque. Besides, a ring rolling machine was built to conduct practical experiments and validate the numerical evaluation, while for the first time, the role of the axial roll and the main roll torque on the quality of the cavity filling is experimentally evaluated. Power requirements and the final ring profile geometry were obtained by the simulation method, and the results were confirmed by the experiments. The results showed that axial rollers significantly reduced the cavity filling rate, and in contrast, the effect of mandrel feed speed and the main roll rotational velocity was much lower. Also, the axial forces were considerably less than the radial forces. However, the rolling operation was done in both radial and axial directions. The existence of axial rolls had an intensive effect on the process’ required power, as a result the main roll torque increased more than three times in case of applying axial rolls, compared with not considering them. Severe effects of axial rollers on increasing force and decreasing cavity filling rate can be attributed to frictional forces between the ring and axial rolls, restricted ring motion, which has to be compensated by a higher torque of the main roll. When the axial rolls are used, the material flow in the ring’s height direction is restricted. Therefore, the material cannot move easily to form the profile. All experimental and simulation results, including mandrel force, cavity filling, and ring profile geometry, were in good agreement, and in all cases, the simulation error was less than 10%.

Predicting coffee ring formation upon drying in droplets of particle suspensions

Pattern formation is a common occurrence in drying colloidal systems. The most common in droplets, is a ring distribution where the constituents have relocated to the edge, which is referred to as a coffee ring. This deposit is unfavourable in many manufacturing processes and is of fundamental interest. In this study, we present a model capable of predicting when a coffee ring will be observed in hard spherical particle systems. Ring profiles are found to be formed at low contact angles with the specific angle predicated upon the initial concentration of the suspension. Modelling results are in agreement with experiments using latex suspensions.

Limits to making L-shape ring profiles without ring growth

A novel ring rolling process is proposed to flexibly produce shaped rings without circumferential ring growth, potentially saving material and energy as well as reducing upstream and downstream processing requirements. In this paper, six circumferential constraint rolls are used constrain circumferential growth and enable L-shape profiles to be developed through axial material flow, via a compressive hoop stress. Process limits were studied in 22 experiments on lead rings and a set of axisymmetric thermally coupled simulations on a high value engineering material, Inconel 718. Profile depths of 75 % of the original wall thickness were achieved in a range of rings and operating conditions, and material savings of up to 60 % demonstrated over rectilinear rolling. There was no evidence of cracking or void formation, unlike processes where under-deformed regions are stretched circumferentially and are vulnerable to cracking. In several cases a non-circular ring shape developed, limiting the achievable profile depth especially for small wall thicknesses, large reductions in thickness per pass, or large profile heights. The constraint roll forces when this ‘collapse’ occurs was studied and an upper bound predicted by a plastic hinge model. The thermal simulations showed that in all except 4 cases reheats would be required to keep within safe temperature bounds, thus suggesting an optimum reduction in thickness per pass to avoid both excessive cooling and collapse.

Influence of dapivirine vaginal ring use on cervicovaginal immunity and functional microbiome in adolescent girls.

Objective:The antiretroviral-based dapivirine vaginal ring reduced HIV risk among women in phase III clinical trials. However, limited data exists on the impact of dapivirine on the vaginal microenvironment in adolescents.Design:A comprehensive metaproteomics approach was used to assess host proteome and microbiome changes in cervicovaginal mucus with dapivirine ring use in adolescents enrolled in the MTN-023/IPM 030 (MTN-023) trial.Methods:Participants were randomized 3 : 1 to use dapivirine or placebo vaginal rings monthly for 6 months. Cervicovaginal samples from a subset of 35 participants (8 placebo, 27 dapivirine) were analyzed.Results:Mass spectrometry analysis identified 405 human and 2467 bacterial proteins belonging to 15 unique genera. The host proteome belonged to many functional pathways primarily related to inflammation. When stratified by study treatment arm, 18 (4.4%) and 28 (6.9%) human proteins were differentially abundant (adjusted P < 0.05) between baseline and follow-up in the placebo and dapivirine arms, respectively. The vaginal microbiome was predominantly composed of Lactobacillus, Gardnerella, and Prevotella. Although bacterial taxa did not differ by arm or change significantly, Lactobacillus crispatus increased (P < 0.001) and Lactobacillus iners decreased (P < 0.001) during the 6-month follow-up. There were no significant differences in bacterial functions by arm or time in the trial. Protected vaginal sex significantly associated with decreased neutrophil inflammatory biomarkers and may be associated with changes in bacterial taxa and metabolism.Conclusion:Condom use may associate with differences to inflammation and bacterial function but dapivirine ring use does not, thereby supporting the mucosal safety profile of this vaginal ring for adolescents.

Estudio numérico del efecto de perfil del primer anillo del pistón de compresión sobre el rendimiento hidrodinámico del lubricante de un motor diésel

El comportamiento del revestimiento del anillo del pistón de combustión representa una de las mayores fuentes de fricción y de potencia para diferentes condiciones de funcionamiento de un motor de combustión interna. El presente trabajo evalúa el efecto del perfil del anillo de compresión sobre el principal comportamiento tribológico del lubricante en un motor diésel de cuatro tiempos. Se desarrolló un análisis unidimensional utilizando el software GT-Suite para la lubricación hidrodinámica entre el segmento del pistón de compresión y la pared del cilindro. Se aplicó un método numérico para analizar la influencia de los diferentes diseños geométricos de anillos durante el ciclo de trabajo sobre el espesor de la película de aceite, la fuerza de fricción y la pérdida de potencia. Se utilizó el modelo de simulación de Takigushi para validar y verificar el modelo numérico utilizado. Los resultados obtenidos mostraron una compatibilidad cualitativa y cuantitativa buena entre los dos modelos aplicados. El modelo numérico utilizado permite analizar la influencia de los parámetros de diseño de anillos para mejorar el rendimiento tribológico de los motores de pistón.

Simulation of deposits effect on cylinder liner and influence on new and worn compression ring of a turbocharged DI engine

Engineers and engine manufactures have known for years that piston rings account as the main source of the friction in internal combustion engines, as much as seventy-five percent in many cases. Excessive engine wear is also, very often caused by poor vehicle operation, and subsequent momentary poor lubrication.The paper presents a numerical methodology and results regarding the wear and deposition effects on an internal combustion engine piston rings as a result of engine lubrication. The deposits can lead to increment of oil consumption and emissions, reducing engine performance and fuel economy.A 2D CFD approach was implemented in order to investigate the characteristics of the top compression ring deposit formation in a diesel engine. The developed pressures, the friction force and the minimum film thickness have been investigated. The variation of the minimum film thickness for new and worn rings at piston reversals, the insufficient minimum film thickness, the thicker films of the increment of the engine speed appeared at worn ring profile in the middle of each stroke, corresponds to a worst sealing behavior due to deposit, are some of major findings of this work.The deposits investigation and hence the paper importance is crucial in combustion engines operation as well as it can covers both axial turbines and their cooling at preliminary design phase.

Modeling of Process of CO-Extrusion of Rubber Mixtures in the Channels of Cable Dies

Results of computer modeling of the process of co-extrusion of two-layer ring profile insulation in extrusion dies by the finite-element method are presented. Design features of the 3D models are specified. Recommendations for obtaining high-quality products are presented.

Effect of the Geometric Profile of Top Ring on the Tribological Characteristics of a Low-Displacement Diesel Engine

The present study aims to analyze the influence of the geometric profile of the compression ring on the tribological properties of the lubricant. Additionally, the influence of the rotation speed and the engine load on the state of the lubricant is evaluated. For this study, a single-cylinder diesel engine is taken as the basis, from which a CAD model of the combustion chamber-piston assembly was made. In addition, the conditions in the cylinder chamber were analyzed when the engine operates at a rotation speed of 3000, 3300, 3600, and 3900 rpm, and a load of 1.5, 3.0, 4.5, and 6.0 N. The calculations were developed using the OpenFOAM® simulation software. The results obtained show that changes in the geometric profile of the ring can contribute to reducing the hydrodynamic friction force by 13% and the friction force caused by roughness by 61%. This implies a decrease in the power lost by friction. In general, the modification of the geometric profile allowed a reduction of 21% in the lost power associated with friction. Additionally, it was observed that the shape of the profile allows to reduce the pressure in the lubricant by 65% and obtain a greater thickness of the lubrication film. On average, an increase of 300 rpm and 1.5 N in the speed and load of the engine causes the friction force and power losses to increase by 45% and 10%. The above results imply that the geometric profile of the compression ring can improve tribological performance in the engine, allowing a reduction in fuel and better lubricant performance.

Influence of interference between the fuselage and the propeller ring on the maximum thrust of the air pusher propeller

The geometrical parameters of ring profiles were presented and the estimation of its influence on the peak values of propeller thrust was described. The results of computational studies using software based on Reynolds-Averaged Navier-Stokes (RANS) equations to investigate the influence of the rear fuselage and the shape of the ring profile on the thrust of pusher propeller were presented. The pressure distribution and the velocity field changed depending on the shape of the rear fuselage and the ring profile, and their influence on the maximum thrust was shown.

Analytical determination of the vane radial loads in balanced vane pumps

The present study proposes an analytical methodology to estimate the variable loads applied to the vanes of balanced vane pumps. The dissertation is adopted to detail the nature of the different time-varying excitations that load the machine and to define their analytical calculation on the basis of vane geometry, cam ring profile and working conditions. In this context, a dimensional reduction is proposed in order to highlight how the pump geometrical parameters affect each single force component and how they may be used to modify the ratio between each load contribution. A comprehensive overview of the mutual interconnections between time-varying loads and the pump design is provided by means of a parametric study involving vane design parameters, pump displacement and cam ring shape. Admissibility of the pump geometry is verified throughout the entire study. The results show that, given the cam ring shape, the vane design significantly influences the radial loads, which may also reach negative values and promote the vane detachment.

The compression ring profile influence on hydrodynamic performance of the lubricant in diesel engine

For different operating conditions of an internal combustion engine, the piston–ring–liner compartment represents one of the largest sources of friction and power losses. The aim of this article is to evaluate the effect of the compression ring profile on the main tribological performance of the lubricant in a four-stroke diesel engine. A one-dimensional analysis was developed for the hydrodynamic lubrication between the compression piston ring and the cylinder wall. A numerical method was applied to analyze the influence of different ring geometrical designs during the working cycle on oil film thickness, frictional force, and power losses. Our predicted results were validated with the Takiguchi data of a previous study, and they have shown a good agreement. The results in the current analysis demonstrated that the ring geometry profile, the engine speed, and load have a remarkable effect on oil film thickness, friction force, and friction power losses between the top ring and cylinder liner. Therefore, it would help in reducing friction as well as making a contribution to the improvement of engine performance such as torque, efficiency, and fuel consumption.

Generation of Perfect Vortex Beams With Polymer-Based Phase Plate

Perfect vortex beam has the characteristics of optical orbital angular momentum and is widely studied because of its advantages of a uniform ring profile and fixed radius. However, the current method of generating perfect vortex beam is mainly based on the phase modulation of spatial light modulator. We have proposed and demonstrated the fabrication of polymer-based phase plate to generate the first and higher-order perfect vortex beams by using maskless lithography exposure technique. According to the relationship of the lithographic depth of polymer and grayscale exposure, the phase plates with different topological charges and axicon parameters are fabricated. By using such polymer-based phase plate, the radius and ring width of perfect vortex beams are analyzed theoretically and experimentally. The fabricated phase plate shows high transmittance as well as perfect vortex beam generation with high quality in the bandwidth range from 1460 nm to 1640 nm. The obtained results prove the feasibility of the attempt of polymer to generate perfect vortex beams, showing great potential in the application of highly miniaturized and integrated optical vortex applications.

Circular Dammann gratings for enhanced control of the ring profile of perfect optical vortices

Perfect optical vortices (POVs) provide a solution to address the challenge induced by strong dependence of classical optical vortices on their carried topological charges. However, traditional POVs are all shaped into bright rings with a single main lobe along the radial direction. Here we propose a method for enhanced control on the ring profile (the radial intensity profile of circular rings) of POVs based on modulated circular sine/cosine radial functions, which is realized by a circular Dammann grating embedded with a spiral phase. Specifically, a type of “absolute” dark POVs surrounded by two bright lobe rings in each side is presented, which provides a perfect annular potential well along those dark impulse rings for trapping low-index particles, cells, or quantum gases. In addition, several POVs with different ring profiles, including conventional POVs with bright rings, the dark POVs mentioned above, and also POVs with tunable ring profiles, are demonstrated. This work opens up new possibilities to controllably tune the ring profile of perfect vortices, and this type of generalized POVs will enrich the content of singular optics and expand the application scope of perfect vortices in a range of areas including optical manipulation, both quantum and classical optical communications, enhanced optical imaging, and also novel structured pumping lasers.

Biomonitoring and Source Identification of Polycyclic Aromatic Hydrocarbons (PAHs) Using Pine Tree Components from Three Different Sites in Bursa, Turkey.

Pine trees are used as biomonitoring agents to evaluate atmospheric polycyclic aromatic hydrocarbons (PAHs). Due to industrialization, urban construction, and rapid population growth, the city of Bursa is experiencing air pollution. In this study, PAHs were measured in pine tree branches and needles at a wastewater treatment plant site, an industrial site, and semirural site in Bursa for 12months. The concentrations fluctuated depending on the characteristics of the areas. The lowest concentration value was measured in the semirural site while the highest value was determined in the wastewater treatment plant site. The PAH concentrations in pine needles ranged from 24 to 2565ng/g dry weight (DW) and in pine branches from 163 to 2871ng/g DW for 16 PAHs. Naphthalene, phenanthrene, fluorene, and fluoranthene were determined as dominant species in both tree components. Diagnostic ratios, ring profile, principal component analysis, the coefficient of divergence, and the Pearson correlation coefficient methods were used in the definition of sources of PAHs in the sampling sites, although all source identification methods have advantages and disadvantages. According to the results, the PAHs mainly originated from biomass and coal burning, traffic, and mixed sources. It also was concluded that three sampling sites showed higher PAH concentrations during winter, and the main PAH sources were similar.

Self-assembly of diphenylalanine peptides on graphene via detailed atomistic simulations.

The self-assembly of diphenylalanine peptides (FF) on a graphene layer, in aqueous solution, is investigated, through all atom molecular dynamics simulations. Two interfacial systems are studied, with different concentrations of dipeptides and the results are compared with an aqueous solution of FF at room temperature. Corresponding length and time scales of the formed structures are quantified providing important insight into the adsorption mechanism of FF onto the graphene surface. A hierarchical formation of FF structures is observed involving two sequential processes: first, a stabilized interfacial layer of dipeptides onto the graphene surface is formulated, which next is followed by the development of a structure of self-aggregated dipeptides on top of this layer. The whole procedure is completed in almost 200 ns, whereas self-assembly in the system without graphene is accomplished much faster; in less than 50 ns cylindrical structures, the microscopic signal of the macroscopic fibrillar ones, are formed. Strong π-π* interactions between FF and the graphene lead to a parallel orientation to the graphene layer of the phenyl rings within a characteristic time of 80 ns, similar to the one indicated by the time evolution of the number of adsorbed FF atoms at the surface. Reduction in the number of hydrogen bonds between FF peptides is observed because of the graphene layer, since it disturbs their self-assembly propensity. The self-assembly of dipeptides and their adsorption onto the graphene surface destruct the hydrogen bond network of water, in the vicinity of FF, however, the total number of hydrogen bonds in all systems increases, promoting the formed structures.

Напряженно-деформированное состояние в зоне увода сварного шва котла цистерны с учетом переменной толщины обечайки

The article presents the results of theoretical studies of the strain-stress state in the breakaway zone of boiler shell ring. According to the developed analytical method, the refined results of the strain-stress state in the breakaway zone of tank boiler welded seam are obtained, taking into account the local thickening of the cross profile of the boiler shell ring.