Mesh Phase Research Articles

IMPROVEMENT OF DESIGN PARAMETERS OF INERTIAL TYPE FUEL CONTINUITY SYSTEMS

Multiple restart of liquid-propellant rocket engines of spacecraft in zero gravity is one of the most difficult tasks that arise in the creation of new products of rocket technology. When performing a flight task, due to the movement of the spacecraft along the passive section of the trajectory, the components of the liquid fuel are mixed with the pressurized gas in its tanks in an arbitrary manner. There is a possibility that the gas phase will be located close to the drain hole. At the time of re-turning on the propulsion engines of the spacecraft, along with fuel, gas bubbles will enter the consumable line from the tank, which can, in turn, cause a failure of their launch.
 In order to avoid this emergency, special fuel continuity systems are used. Despite the significant diversity of these systems, all of them have significant shortcomings and limited working conditions. The main purpose of using fuel continuity systems of any type is to prevent the penetration of boost gas from the tank cavity into the flow line until the tank is completely emptied.
 The paper is devoted to the analysis of the possibilities of improving the design parameters of the two most common systems for ensuring fuel continuity by creating a combined "hybrid" system on their basis. Inertial and mesh systems for ensuring fuel continuity are considered. Theoretically, an analysis of the possibility of reducing the effect of pre-start acceleration for an inertial system for ensuring fuel continuity due to the use of a mesh phase separator in the fuel supply system is carried out. The paper considers the main design parameters of this combined system, which directly affect the level of its technical perfection, as well as the possibilities of their optimization.
 The results of the work can be useful in engineering practice in the creation of new promising products of rocket and space technology.

Експериментальне визначення зміни капілярної утримної здатності сітчастих розділювачів фаз

The subject of this study is the process of loss of capillary holding capacity (CHC) as a result of a violation of the balance of external and internal forces on the phase interface (PI) "liquid - gas" of the capillary in the cell of the mesh phase separator (MPS) of the capillary means for ensuring the integrity of the fuel (CMEIF) with a long service life in chemically aggressive fuel components (FP): nitrogen tetroxide (NT) and asymmetric dimethylhydrazine (NDMH). The goal is to improve the selection of design parameters of the CMEIF through the refinement of traditional approaches to the calculation of the CHC MPS depending on the term of their operation. Task: to determine the rate of corrosion of the main structural material of the MPS - steel nets of the twill weave type, and its effect on the structural and geometric characteristics of the nets; to perform an experimental determination of the change in the MPS CHC; to improve the mathematical model for determining the MPS CHC, considering the term of their operation as part of the fuel system of space flight vehicles (SFV). The methods used are as follows: to determine the rate of corrosion - metallographic studies and measurement of the geometric dimensions of mesh samples; to determine the change in CHC - the bubble method. The following results were obtained. The coefficient of the maximum corrosion rate was determined. A new, refined dependence of the average value of Bo cr on the temperature of the FP was obtained. Linear regressions of changes in the approximated values of CHC MPS depending on the duration of their operation were obtained. An increase in the average arithmetic value of the wetting contact angle θ in the NDMG over 31 years of MPS operation was determined. An improved mathematical model for determining the CHC of MPS was obtained, considering the period of their operation in JSC and NDMH. Conclusions. The scientific novelty of the obtained results is as follows: for the first time, comprehensive studies were carried out to determine the rate of corrosion of the main structural material of MPS after a long period of their stay (from 14 to 31 years) in FP (NT and NDMG) and under their pairs, the results of which revealed regularities of flow corrosion processes in the liquid and gas phase, established corrosion rates and deduced coefficients, the application of which improves the engineering methods of calculating the main parameters of MPS; the physical model for calculating Bo kr received further development; the physical model for calculating the CHC has been improved, which makes it possible to calculate the value of the static CHC of the MPS with greater accuracy than it was before and to make the final design of the designed CMEIF more perfect and reliable.

Symmetry-driven vibration behaviors in epicyclic/planetary gears: criticality of the mesh phase parameter

This work investigates the vibration properties of planetary/epicyclic gears that arise from their cyclic symmetry. All results are derived without use of a specific mathematical model; only cyclic symmetry and periodicity of the response at the mesh frequency are required. Thus, the results apply for: spur and helical gear systems, two- and three-dimensional models, systems modeled with finite elements (or similar) or analytically, systems with any combination of elastically deformable and rigid-body components, and systems with and without high-speed gyroscopic effects. Because no model is involved, the findings apply to systems in industrial applications or experiments where no model is available. The modal properties are given in a form where central component (carrier, ring, and sun) deflections are described by nodal diameter (i.e., Fourier) components. An integer-valued mesh phase parameter is the critical quantity. It depends on the mesh frequency harmonic number, number of ring gear teeth, and number of planets. For each harmonic of mesh frequency, this mesh phase parameter determines: the specific nodal diameter components of each central component that can participate in that harmonic, the specific vibration modes that contribute to the response at the given harmonic, whether a potential resonance when the given harmonic of mesh frequency is close to a natural frequency can actually occur (most resonances cannot), and the sideband frequencies near the mesh frequency harmonic as measured by a sensor rotating at an arbitrary speed. The spectral sideband frequencies and amplitudes are linked to specific nodal diameter components of the central component vibrations, and they determine the specific modes present in the response. Dynamic simulations using finite element/contact mechanics software and an analytical model confirm the findings. We discuss the significant benefits in planetary gear design and practical troubleshooting and experimental testing.

PROSPECTS FOR THE USE OF WOVEN METAL MESHES AS PHASE SEPARATORS

The constant complication of the tasks that arise before spacecraft during their flight mission puts very high demands on the fuel supply system. First of all, during orbital flight, very often there is a need to restart the main engines, or a constant supply of fuel to the engines of the control system. It is necessary to deliver fuel from tanks to engine combustion chambers in conditions of practical weightlessness. To ensure the ingress of fuel components from the tank into the drain line without gas inclusions, a fuel continuity system is added to the fuel supply system. 
 Among the various systems for ensuring fuel continuity, the most widespread over the past fifty years have been mesh phase separators, the main working element of which is woven metal mesh.
 The paper considers the basic properties of systems of this type, their main design parameters from the point of view of the possibility of their improvement and the possibility of use in future designs of spacecraft. Considerable attention is paid to the shortcomings inherent in systems of this type. Possible ways to eliminate the limitations of the use of mesh phase separators through the development of new engineering design techniques and the use of modern technologies to create analogues of woven metal meshes, which are devoid of their main drawbacks, are considered.

2-d liquid-liquid phase separation of GM130 Golgin protein bound to supported bilayer.

Golgins are long (50-400 nm) rod-like membrane proteins, enveloping the Golgi apparatus (GA). They initially capture cognate cargo vesicle, to facilitate Snare-mediated membrane fusion. Most of them can phase separate and this may result to internal organization of the GA. Golgi matrix protein 130 (GM130), is the most abundant Golgin located at the cis Golgi. In our study of recombinant GM130 on supported bilayer system, we observed that GM130 self-assembles and phase separates into two distinct phases: A Mesh phase and a Condensate phase. Here we will describe the precise nature of these phases and their hypothetical physiological roles in the GA.

Wind turbine planetary gearbox fault diagnosis using circular pitch cyclic vector and a bidirectional gated recurrent unit

A planetary gearbox with large transmission ratio is a critical component of a wind turbine (WT). When the planetary gearbox suffers from failure, the regular variation of circular pitch vibration energy contains fault pattern information. Although deep learning-based fault diagnosis models have the capability for automatic feature extraction, they rarely consider emphasizing the energy variation characteristics related to the planetary transmission structure in the data representation stage, which degrades the fault diagnosis performance. To solve this problem, this paper describes a novel data representation method, circular pitch cyclic vector (CPCV) and, on this basis, proposes a WT planetary gearbox fault diagnosis method using CPCV and a bidirectional gated recurrent unit (BGRU). Firstly, this paper utilizes root mean square value as the energy evaluation metric for calculating the CPCV. Then, the mapping relationship between circular pitch energy and the ring gear mesh phase is captured using the BGRU through its bidirectional learning capability. Finally, a fully connected layer with softmax is used for fault classification. The proposed method is evaluated by analyzing the in-service WT vibration data collected from a wind farm in eastern China. The experimental results and comparison analysis illustrate the superiority of the proposed method.

Mesh scheme for a phase transition problem with time-fractional derivative

Abstract The time-fractional phase transition problem, formulated in enthalpy form, is studied. This nonlinear problem with an unknown moving boundary includes, as an example, a mathematical model of one-phase Stefan problem with the latent heat accumulation memory. The posed problem is approximated by the backward Euler mesh scheme. The unique solvability of the mesh scheme is proved and a priori estimates for the solution are obtained. The properties of the mesh problem are studied, in particular, an estimate of movement rate for the mesh phase transition boundary is established. The proved estimate make it possible to localize the phase transition boundary and split the mesh scheme into the sum of a nonlinear problem of small algebraic dimension and a larger linear problem. This information can be used for further construction of efficient algorithms for implementing the mesh scheme. Several algorithms for implementing mesh scheme are briefly discussed.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ВЗАЄМОДІЇ СІТЧАСТИХ РОЗДІЛЮВАЧІВ ФАЗ С ГАЗОВИМИ ПУЗИРЯМИ В УМОВАХ ЗМІННОГО ПОЛЯ МАСОВИХ СИЛ

Modern multi-purpose spacecraft for several years must perform complex and diverse tasks in outer space. At the same time, it is necessary to turn on jet engines dozens of times in conditions of practical weightlessness. At the time of starting the engine, the liquid fuel is mixed randomly with the boost gas. In this case, it is impossible to guarantee the contact of the drainage hole with the gas phase, and the drain hole with the fuel. To solve this problem, it is proposed to use various, so-called means of ensuring the continuity of fuel (MECF). The effectiveness of monitoring the position of the liquid in the flight conditions of the aircraft in the passive section of the trajectory is determined by the ability of the MECF to ensure the discharge of fuel from the tank without gas inclusions at any required time with a given flow rate and in the required amount with a minimum volume of unselected residues.
 The article deals with the features of the functioning of the SOST of the inertial type, which includes mesh phase separators (MPS). The need to use the MPS is due to the possibility of the gas phase entering the drain line, both in the passive section of the trajectory and at the stage of switching on the main engines, which can lead to a disruption of their launch. When fuel moves into the drain line, bubbles remain on the mesh surface and prevent the passage of liquid. 
 The article builds a mathematical model of the behavior of gas bubbles on the surface of the MPS in the flow of a viscous liquid. On the basis of the constructed mathematical model, the corresponding numerical calculations were carried out. The proposed method of engineering calculation makes it possible to determine such a MECF design that excludes the possibility of "contamination" of the surface of the MPS by gas bubbles and the disruption as a result of this normal functioning of the fuel supply system to the engines of spacecraft.

Shear-Induced Ordering of Nanopores and Instabilities in Concentrated Surfactant Mesh Phases.

Mixed surfactant systems with strongly bound counterions show many interesting phases such as the random mesh phase consisting of a disordered array of defects (water-filled nanopores in the bilayers). The present study addresses the non-equilibrium phase transition of the random mesh phase under shear to an ordered mesh phase with a high degree of coherence between nanopores in three dimensions. In situ small-angle synchrotron X-ray study under different shear stress conditions shows sharp Bragg peaks in the X-ray diffraction, successfully indexed to the rhombohedral lattice with R3̅m space group symmetry. The ordered mesh phase shows isomorphic twinning and buckling at higher shear stress. Our experimental studies bring out rich non-equilibrium phase transitions in concentrated cationic surfactant systems with strongly bound counterions hitherto not well explored and provide motivation for a quantitative understanding.

Numerical calculation and experimental measurement for gear mesh force of planetary gear transmissions

In this paper, we propose a numerical method to calculate the dynamic mesh forces of planetary gear transmissions (PGTs). In this model, the effects of addendum modification are included in the time-varying mesh stiffness (TVMS) and then the influence of TVMS and relative mesh phase on the dynamic mesh forces are considered in the proposed model. To verify the proposed model, an experimental method is proposed to measure the dynamic ring-planet mesh forces by using gear tooth root-fillet strain signals. Static mesh experiments and dynamic mesh experiments are carried out to obtain the strain signals. To measure the dynamic mesh force, the loaded tooth contact analysis (LTCA) method and quasi-static experiments are carried to determine the coefficient matrix which is used to descript the relationship between the mesh force and tooth root-fillet strain. Finally, calculated mesh forces and measured forces are compared and discussed. Results indicate that the proposed experimental method can effectively measure the dynamic ring-planet mesh forces, and the numerical mesh forces agree well with the measured mesh forces.

Tuneable interfacial surfactant aggregates mimic lyotropic phases and facilitate large scale nanopatterning.

It is shown that the air-liquid interface can be made to display the same rich curvature phenomena as common lyotropic liquid crystal systems. Through mixing an insoluble, naturally occurring, branched fatty acid, with an unbranched fatty acid of the same length, systematic variation in the packing constraints at the air-water interface could be obtained. The combination of atomic force microscopy and neutron reflectometry is used to demonstrate that the water surface exhibits significant tuneable topography. By systematic variation of the two fatty acid proportions, ordered arrays of monodisperse spherical caps, cylindrical sections, and a mesh phase are all observed, as well as the expected lamellar structure. The tuneable deformability of the air-water interface permits this hitherto unexplored topological diversity, which is analogous to the phase elaboration displayed by amphiphiles in solution. It offers a wealth of novel possibilities for the tailoring of nanostructure.

Investigation of ordered mesh phases using their detailed reconstructed electron density maps

We presently studied the ordered mesh phases observed in the aqueous solution of cationic surfactant cetylpyridinium chloride (CPC) in the presence of strongly binding counterion 2-sodium-3-hydroxy naphthoate (SHN). Reconstructed electron maps of the ordered mesh phases which were lacking in the previous studies are now the prime focus of this present report. The Reconstructed electron maps in 3D and 2D have been reconstructed from X-ray diffraction patterns of the ordered mesh phases, Rh and T, using information of the intensities and indexing of the diffraction peaks. The 3D reconstructed electron density maps indicate the layered structure of the Rh and T phases whereas 2D reconstructed electron density maps exhibit well organized pore like structure in each layer of the Rh and T phases. Our results show that the size of amphiphile, CPC, in Rh and T phases is 22.39 ± 0.37 Å and 20.79 ± 0.34 Å, respectively. And also exhibit that about 89.68 ± 3.66% of water volume is in the pores of the T phase whereas only 69.97 ± 2.85% of water volume is in the pores of Rh phase.

Influence of long-term stay of elements of capillary intake devices in liquid propellant components on their parameters

In this paper, we consider the results of a long-term study of the effect of prolonged stay (more than 30 years) of elements of capillary intake devices - mesh phase separators in the liquid propellant components (and under vapors) on the change in their working parameters (characteristics). In the process of research, the following types of work were carried out: extracting mesh phase separators from the propellant tanks of the missile stages to be detected after they were neutralized; analyzing the chemical composition of the substances located on the grids of mesh phase separators; determining the capillary holding capacity of the mesh, measuring the geometric dimensions of the mesh by the optical method; and performing metallographic studies of the mesh patterns. As a result, the authors determined the decrease in the capillary holding capacity of the screen of mesh phase separators for 31 years of their stay in the liquid propellant components and under their vapor. The analysis of the main factors was made that influenced the change in the design parameters of the capillary intake device: uniform corrosion damage and local changes in the microstructure of the structural material of the meshes, as well as a change in the value of the contact angle of the propellant with the mesh material.

Mesh Phase Analysis of Encased Differential Gear Train for Coaxial Twin-Rotor Helicopter

Dynamic excitation caused by time-varying meshing stiffness is one of the most important excitation forms in gear meshing process. The mesh phase relations between each gear pair are an important factor affecting the meshing stiffness. In this paper, the mesh phase relations between gear pairs in an encased differential gear train widely used in coaxial twin-rotor helicopters are discussed. Taking the meshing starting point where the gear tooth enters contact as the reference point, the mesh phase difference between adjacent gear pairs is analyzed and calculated, the system reference gear pair is selected, and the mesh phase difference of each gear pair relative to the system reference gear pair is obtained. The derivation process takes into account the modification of the teeth, the processing, and assembly of the duplicate gears, which makes the calculation method and conclusion more versatile. This work lays a foundation for considering the time-varying meshing stiffness in the study of system dynamics, load distribution, and fault diagnosis of compound planetary gears.

Model-based analysis and fault diagnosis of a compound planetary gear set with damaged sun gear

The vibration properties of compound planetary gears are more complicated than that of simple ones. This paper aims to investigate the fault properties of a compound planetary gear set in chipped sun gear conditions using model-based method. A three-dimensional lumped-parameter nonlinear dynamic model for the compound planetary gear set is established. This model considers the time-varying mesh stiffness (TVMS), the mesh phase relations, and gear chipping defects. The analytical equations are derived to quantify the TVMS reduction induced by the chipped gear based on the improved potential energy method. Further, the simulations are performed to demonstrate the fault features of sun gears with single or multiple chipped teeth in different gear stages. Moreover, the theoretical derivations are validated through the experimental signals analysis.

Removal of line artifacts on mesh boundary in computer generated hologram by mesh phase matching.

Mesh-based computer generated hologram enables realistic and efficient representation of three-dimensional scene. However, the dark line artifacts on the boundary between neighboring meshes are frequently observed, degrading the quality of the reconstruction. In this paper, we propose a simple technique to remove the dark line artifacts by matching the phase on the boundary of neighboring meshes. The feasibility of the proposed method is confirmed by the numerical and optical reconstruction of the generated hologram.

ステップドピニオン式遊星歯車装置の振動挙動

It is well known that the characteristics of exiting force of planetary gear mesh are varied with gear mesh phase between pinions in single pinion type planetary gear set and that the sideband phenomenon occurs in the sequentially phased planetary gear set. This sideband phenomenon is one in which the (Z-1) or (Z+1) order component level is higher than the mesh order (Z) component level. The notation (Z-1) or (Z+1) means the mesh order (Z) minus or plus one carrier revolution. In this study, the relationship between gear mesh phase and vibration behavior is investigated in the stepped pinion type planetary gear set which has two mesh order component and is operated at wide frequency range. The formulae of mesh force of 6 degrees of freedom acting in sun gear, carrier and ring gear respectively are derived for stepped type planetary gear set. From the experimental and calculated results, the same side band phenomena were also observed in the stepped type planetary set. By taking into account the side band order component of gear mesh, it was revealed that the influence of gear mesh phase on the characteristics of unit case vibration is varied by frequency range. It is considered that the dominant direction component of exiting force for the case vibration of applied unit moves from transverse direction at low- frequency range to rotation direction at high-frequency range.

Model-Based Fault Diagnosis of a Planetary Gear Using Transmission Error


 
 
 A Planetary gear can transmit high torque ratio stably and, therefore, the gear is widely used in industrial applications, i.e., wind turbines, automobiles, helicopters. Unexpected failure of the planetary gear results in substantial economic loss and human casualties. Extensive efforts have been made to develop the fault diagnostic techniques of gears; however, the techniques are mostly concerned about spur gears. This is mainly because understanding of complex dynamic behaviors of a planetary gear is lacking, such as multiple gear contacts, non-stationary axis of rotation, etc. This study thus proposes model-based fault diagnostics for a planetary gear that is based upon its dynamic analysis. Instead of vibration signals, this study uses transmission error (TE) signals for fault diagnostics of the planetary gear because TE signals (a) are directly related to the dynamic behaviors of gear mesh stiffness and (b) increase as damages on a gear mesh reduce the gear mesh stiffness. A lumped parameter model was used for modeling dynamic behaviors of the planetary gear. For more precise modeling, mesh phase difference–between sun, ring, and planet gear– and contact ratio were taken into account in the lumped parameter model. After acquiring transmission error signals from the model, order analysis and data processing were executed to generate health related data for the planetary gear. Consequently, it is concluded that the use of transmission error signals helps gain understanding of complex dynamic behaviors of the planetary gear and diagnose its potential faults.
 
 

Self-Assembly of Didodecyldimethylammonium Surfactants Modulated by Multivalent, Hydrolyzable Counterions

The self-assembly behavior of double-chained didodecyldimethylammonium (DDA(+)) surfactants with hydrolyzable phosphate (PO4(3-), HPO4(2-), and H2PO4(-)), oxalate (HC2O4(-) and C2O4(2-)), and carbonate (HCO3(-)/CO3(2-)) counterions was found to depend on both the counterion and its hydrolysis state, as determined by the pH of the system. Carbonate and phosphate ions at all hydrolysis states successfully stabilize an extended isotropic micellar solution region. These micelles are well-described as prolate ellipsoids which vary in size and aspect ratio depending on the surfactant concentration and hydrolysis state of the counterion. Both oxalate counterions form bilayer structures in dilute solution. The structures found with divalent oxalate, C2O4(2-), ions possessed very limited swelling capacity compared to the bilayer structures formed with monovalent oxalate, HC2O4(-), ions. The lamellar (Lα) phase was universally formed at sufficiently high surfactant concentrations for all hydrolyzable counterions. Two intermediate structures corresponding to a disordered mesh (Lα(D)) and tetragonal ordered mesh (T) phase were found to form with DDA2HPO4 prior to the Lα phase but not with other phosphate counterions.

Parametric vibration of split gears induced by time-varying mesh stiffness

Time-varying mesh stiffness is a significant excitation source within gear systems. Split gear (or laminated gear, phase gear) is an interesting design using equally phased gear-slices, which can remarkably reduce the mesh stiffness fluctuation like helical gears but completely avoid the axial force. This work examines a split gear pair to address the suppression of the mesh stiffness fluctuation and rotational vibration thereof, especially the relationship between the key design parameters including the number of slice, contact ratio, and damping, and the parametric vibration. For these aims, this work develops a purely rotational model, based on which the multi-scale method is employed to determine stability boundaries. The results imply that the unstable zones are related to the mesh phase determined by the number of slices and contact ratio, and these zones can be diminished by the damping. The analytical predictions are numerically verified by Floquet theory.