Coupled evolution of piston asperity and cylinder bore contour of piston/cylinder pair in axial piston pump

The wear condition of the piston/cylinder pair is crucial to the performance and reliability of the axial piston pump.The hard piston surface,the soft cylinder bore surface,and the interface oil film affects each other during the wear process.Specifically,in the mixed lubrication region,the geometry of the hard piston surface asperity directly affects the wear of soft cylinder bore surface,while the asperities may deform or even degrade when penetrating and sliding against the cylinder bore.So far,there is no suitable method to simulate their coupled evolution.This paper proposed a wear process simulation model considering the real-time interaction between the elasto-plastic deformation of the piston surface asperity,the wear contour of the cylinder bore,and the lubrication condition of the interface.An offline library of the elasto-plastic constitutive behavior of the asperity based on the finite element method(FEM)is established as a part of the simulation model to precisely analyze the deformation and degradation of the asperity and quickly invoke them in the numerical wear process simulation.The simulation and experimental results show that the piston asperity and the cylinder bore contour converge to a steady state after running-in for about 0.5 h.The distribution of the simulated asperity degradation and wear depth is also verified by the experiment.

Analytical Solution and Simplified Formula for Added Mass of Horizontal and Vertical Motions of Truncated Cylinders Under Earthquake Action

This paper investigates the hydrodynamic characteristics of floating truncated cylinders undergoing horizontal and vertical motions due to earthquake excitations in the finite water depth.The governing equation of the hydrodynamic pressure acting on the cylinder is derived based on the radiation theory with the inviscid and incompressible assumptions.The governing equation is solved by using the method of separating variables and analytical solutions are obtained by assigning reasonable boundary conditions.The analytical result is validated by a numerical model using the exact artificial boundary simulation of the infinite water.The main variation and distribution characteristics of the hydrodynamic pressure acting on the side and bottom of the cylinder are analyzed for different combinations of wide-height and immersion ratios.The added mass coefficient of the cylinder is calculated by integrating the hydrodynamic pressure and simplified formulas are proposed for engineering applications.The calculation results show that the simplified formulas are in good agreement with the analytical solutions.

On the spreading behavior of a droplet on a circular cylinder using the lattice Boltzmann method

The study of a droplet spreading on a circular cylinder under gravity was carried out using the pseudo-potential lattice Boltzmann high-density ratios multiphase model with a non-ideal Peng–Robinson equation of state. The calculation results indicate that the motion of the droplet on the cylinder can be divided into three stages: spreading, sliding, and aggregating.The contact length and contact time of a droplet on a cylindrical surface can be affected by factors such as the wettability gradient of the cylindrical wall, the Bond number, and droplet size. Furthermore, phase diagrams showing the relationship between Bond number, cylinder wall wettability gradient, and contact time as well as maximum contact length for three different droplet sizes are given. A theoretical foundation for additional research into the heat and mass transfer process between the droplet and the cylinder can be established by comprehending the variable rules of maximum contact length and contact time.

A Review on Vibration Control of Multiple Cylinders Subjected to FlowInduced Vibrations

The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering applications.The FIV suppression is of great importance for the security of many cylindrical structures.Many active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated cylinder.Due to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV suppression.Some efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two decades.The control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control devices.The FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and summarized.The FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence factors.Further research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.

Impact of a Magnetic Dipole on Heat Transfer in Non-Conducting Magnetic Fluid Flow over a Stretching Cylinder

The thermal behavior of an electrically non-conducting magnetic liquid flowing over a stretching cylinder under the influence of a magnetic dipole is considered.The governing nonlinear differential equations are solved numerically using a finite element approach,which is properly validated through comparison with earlier results available in the literature.The results for the velocity and temperature fields are provided for different values of the Reynolds number,ferromagnetic response number,Prandtl number,and viscous dissipation parameter.The influence of some physical parameters on skin friction and heat transfer on the walls of the cylinder is also investigated.The applicability of this research to heat control in electronic devices is discussed to a certain extent.

Piston-Cylinder高温高压实验装置及在壳幔动力学研究中的应用

介绍了目前在国际壳幔作用及动力学研究中普遍使用的Piston-Cylinder高温高压实验技术的主要工作原理、结构、样品装置设计及主要技术指标。通过分析Piston-Cylinder高温高压实验技术在大洋和大陆板块俯冲深部过程的流体活动、基性岩石部分熔融作用、岩浆活动机制及约束条件等壳幔相互作用研究中的应用实例,认为引进该项实验技术对于我国科技工作者开展高温高压条件下壳幔动力学研究以及缩短我国实验岩石学技术手段与国际间的差距具有重要意义。

Analysis of Oil Consumption in Cylinder of Diesel Engine for Optimization of Piston Rings

The performance and particulate emission of a diesel engine are affected by the consumption of lubricating oil. Most studies on oil consumption mechanism of the cylinder have been done by using the experimental method, however they are very costly. Therefore, it is very necessary to study oil consumption mechanism of the cylinder and obtain the accurate results by the calculation method. Firstly, four main modes of lubricating oil consumption in cylinder are analyzed and then the oil consumption rate under common working conditions are calculated for the four modes based on an engine. Then, the factors that affect the lubricating oil consumption such as working conditions, the second ring closed gap, the elastic force of the piston rings are also investigated for the four modes. The calculation results show that most of the lubricating oil is consumed by evaporation on the liner surface. Besides, there are three other findings： （1） The oil evaporation from the liner is determined by the working condition of an engine; （2） The increase of the ring closed gap reduces the oil blow through the top ring end gap but increases blow-by; （3） With the increase of the elastic force of the ring, both the left oil film thickness and the oil throw-off at the top ring decrease. The oil scraping of the piston top edge is consequently reduced while the friction loss between the rings and the liner increases. A neural network prediction model of the lubricating oil consumption in cylinder is established based on the BP neural network theory, and then the model is trained and validated. The main piston rings parameters which affect the oil consumption are optimized by using the BP neural network prediction model and the prediction accuracy of this BP neural network is within 8%, which is acceptable for normal engineering applications. The oil consumption is also measured experimentally. The relative errors of the calculated and experimental values are less than 10%, verifying the validity of the simulation results. Applying the established simulation model and the validated BP network model is able to generate numerical results with sufficient accuracy, which significantly reduces experimental work and provides guidance for the optimal design of the piston rings diesel engines.

Novel mechanism for boring non-cylinder piston pinhole based on giant magnetostrictive materials

To bear more loads for heavy truck pistons, the shape of heavy truck piston pinhole is often designed as noncylinder form. Current methods cannot meet the needs for precision machining on non-cylinder piston pinhole （NCPPH）. A novel mechanism based on giant magnetostrictive materials （GMM） is presented. New models are established for the servo mechanism, GMM, and magnetizing force of the control solenoid to characterize the relationship between the control current of the solenoid and the displacement of the giant magnetostrictive actuator （GMA）. Experiments show that the novel mechanism can meet the needs to perform fine machining on NCPPH effectively.

基于多CNN的分块镜piston和tip-tilt误差同步检测方法研究

绝大多数大型望远镜采用分块镜的设计方案,为了获得优质的成像效果,需要控制分块望远镜系统的piston和tip-tilt误差。神经网络误差检测方法相较于传统的检测方法具有一定优势,但存在仅检测单一类型误差的局限性。本文提出一种基于卷积神经网络的piston和tip-tilt误差同步检测方法,通过在出瞳面设置具有离散孔的光阑,引发分段镜反射的子波发生干涉-衍射现象,构建包含丰富piston和tip-tilt误差信息的数据集。通过粗测网络和精测网络级联,满足大范围和高精度同步检测的需求。结果表明,该方法实现了对输入光源相干长度内纳米级的piston误差检测,并对10μrad范围内的tip-tilt误差实现了亚微弧度检测;对40 dB的CCD噪声表现出良好的抗干扰性,对面形误差的允差为0.05λ0RMS(λ0=600 nm),同时对六子镜系统具有可扩展性。本文方法光路简单,操作便利,具有实际意义。

Piston-ring and Cylinder-liner Lubrication in Internal Combustion Engines Based on Thermo-hydrodynamic

Currently the extruded effect,roughness to the lubricant shear thinning,temperature changes and other factors or some combination of a single factor mainly considered in the lubrication study of piston ring-cylinder.In the study of the energy equation,the oil viscosity-temperature properties,adsorption layer characteristics are usually not considered.So the theoretical research is different from the actual situation of engineering.The lubrication of piston ring-cylinder liner system in internal combustion(IC) engines is studied here based on the theory of thermal flow.An unsteady and compressible hydrodynamic lubrication model with an equivalent viscosity based on shear and extruded flow factor is derived by employing the viscosity-temperature relationship,meanwhile,characteristics such as lubricating oil’s density varying with pressure and temperature,thickness of adsorbent layer and oil film’s geometry are also considered in this model.While setting up the energy equation,the effect of lubricating oil’s volume expansion and viscous dissipation on temperature,the heat conduction along oil film’s thickness direction are considered.Finite difference equation is formed by using a first-order difference scheme in time scale and second-order difference scheme in space scale.A common diesel engine is introduced as an instance to predict the distribution of the minimum oil film thickness in the piston ring-cylinder liner system.The results of simulation calculation show that the minimum oil film thickness will decrease especially around the top dead center when the oil’s volume expansion,viscous dissipation and heat conduction are considered,which implies that:it is essential to take the thermal flow idea into account during investigating piston ring-cylinder liner system’s lubrication.A more complete piston ring-cylinder liner lubrication theory was established according to thermal fluids from the perspective of research.It is more helpful to guide the practical application of engineering to improve the accuracy of forecasting the minimum film thickness.On the other hand,distribution of the minimum oil film thickness shows a nonlinear property if the thickness of piston rings and cylinder liner adsorbent layer are involved in the analysis.It may be feasible to increase the minimum oil film thickness by varying surface roughness and material properties of piston rings and cylinder liner.

Theoretical Analysis of Noise of Piston Knocking Cylinder Wall in Automotive Engines

Based on the loading conditions of engine, applying difference method to solve the hydrodynamic lubrication equation of piston skirt movement, the force acting on piston skirt and the moment on wrist pin were obtained. A computer program for simulating the piston second order motion was conducted to calculate the lateral motion of the upper part and the bottom part of piston skirts of the engine of automotive model CA1091. From the simulated result, the maximal impacting phase and the maximal impacting region of the piston were obtained. The result can be used for designing engine, diagnosing the noise of piston knocking cylinder wall and explaining many practical fault phenomena in theory.

Cavitation of a Submerged Jet at the Spherical Valve Plate/Cylinder Block Interface for Axial Piston Pump

The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate,resulting in special cavitation phenomenon on the spherical port plate pair.In order to study cavitation characteristics of spherical port plate pair,a dynamic CFD model of the piston pump including turbulence model,cavitation model and fluid compressibility is established.A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh,which makes up for the lack of research on the meshing of the spherical oil film.In this paper,using CFD simulation tools,from the perspectives of pressure field,velocity field and gas volume fraction change,a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out.The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point.The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface.These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair.The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate,but also cause strong impact and denudation on the lower surface of the cylinder body.Finally,the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.

Theoretical model of radiation heat wave in two-dimensional cylinder with sleeve

A semi-analytical model is constructed to investigate two-dimensional radiation heat waves(Marshak waves)in a low-Z foam cylinder with a sleeve made of high-Z material.In this model,the energy loss to the high-Z wall is regarded as the primary two-dimensional effect and is taken into account via an indirect approach in which the energy loss is subtracted from the drive source and the wall loss is ignored.The interdependent Marshak waves in the low-Z foam and high-Z wall are used to estimate the energy loss.The energies and the heat front position calculated using the model under typical inertial confinement fusion conditions are verified by simulations.The validated model provides a theoretical tool for studying two-dimensional Marshak waves and should be helpful in providing further understanding of radiation transport.

Research on control method for machining non-cylinder pin hole of piston

The control method for machining non-cylinder pin hole of piston was studied systematically. A new method was presented by embedding giant magnetostrictive material (GMM) into the tool bar proper position. The model is established to characterize the relation between control current of coil and deformation of tool rod. A series of tests on deformation of giant magnetostrictive tool bar were done and the results validated the feasibility of the principle. The methods of measuring magne- tostrictive coefficient of rare earth GMM were analyzed. The measuring device with the bias field and prestress was designed. A series of experiments were done to test magnetostrictive coefficient. Experimental results supplied accurate characteristic pa- rameter for designing application device of GMM. The constitution of the developed control system made up of displacement detection and temperature detection for thermal deformation compensation was also introduced. The developed machine tool for boring the non-cylinder pin hole of piston has the micron order accuracy. This control method can be applied to other areas for machining precision or complex parts.

SPH Modelling of the Vortex-Induced Vibration of A Near-Wall Cylinder

The frequency-locked phenomenon commonly occurs in the vortex-induced vibration(VIV)of bluff bodies.Numerical simulation of this lock-in behavior is challenging,especially when the structure is positioned in close proximity to a solid boundary.To establish a robust simulator,an enhanced smoothed particle hydrodynamic(SPH)model is developed.The SPH model incorporates a particle shifting algorithm and a pressure correction algorithm to prevent cavity formation in the structure's wake area.A damping zone is also established near the outlet boundary to dissipate the vortices that shed from the structure.Additionally,GPU parallel technology is implemented to enhance the SPH model's computational efficiency.To validate the mo del,the predicted results are compared with the available refere nce data for flow past both stationary and oscillating cylinders.The verified SPH model is then employed to comparatively investigate the motion re sponse,lift characteristic,and vortex shedding mode of cylinders with and without accounting for the effect of boundary layers.Numerical analyses demonstrate that the developed SPH model is a proficient tool for efficiently simulating the vibration of near-wall bluff bodies at low Reynolds number.

Poroelastodynamic responses and elastic moduli of a transversely isotropic porous cylinder under forced deformation test

Existing transversely isotropic poroelastodynamics solutions are limited to infinite domains and without experimental validation. Furthermore, there is a lack of analytical simulations for the elastic moduli dispersion of fluid-saturated porous cylinders. To address these three limitations and investigate the mechanisms of moduli dispersion, we present the analytical solutions of the poromechanical responses and the elastic moduli dispersion of a transversely isotropic, fluid-saturated, finite porous cylinder subjected to a forced deformation test. Through an example, we demonstrate the effects of loading frequency, boundary conditions, and material's anisotropy, dimension, and permeability on the responses of pore pressure,force, displacement, and dynamic elastic moduli of the cylinder. The specimen's responses are significantly influenced by the frequency of the applied load, resulting in a drained state at low frequencies and an undrained state at high frequencies. At high frequencies, the sample behaves identically for an open or a closed lateral boundary, and permeability has insignificant effects. The dynamic elastic moduli are mainly controlled by the loading frequency and the ratio of the sample's radius to its height. Lastly,we show excellent matches between the newly derived analytical solution and laboratory measurements on one clay and two shale samples from Mont Terri.

Vector fiber Bragg gratings accelerometer based on silicone compliant cylinder for low frequency vibration monitoring

Vector accelerometer has attracted much attention for its great application potential in underground seismic signal measurement. We propose and demonstrate a novel vector accelerometer based on the three fiber Bragg gratings(FBGs)embedded in a silicone rubber compliant cylinder at 120° distributed uniformly. The accelerometer is capable of detecting the orientation of vibration with a range of 0°–360° and the acceleration through monitoring the central wavelength shifts of three FBGs simultaneously. The experimental results show that the natural frequency of the accelerometer is about 85 Hz, and the sensitivity is 84.21 pm/g in the flat range of 20 Hz–60 Hz. Through experimental calibration, the designed accelerometer can accurately obtain vibration vector information, including vibration orientation and acceleration. In addition, the range of resonant frequency and sensitivity can be expanded by adjusting the hardness of the silicone rubber materials. Due to the characteristics of small size and orientation recognition, the accelerometer can be applied to low-frequency vibration acceleration vector measurement in narrow spaces.

Application of Optical Visualization Method in Observing Flow Field Around a Cylinder

In this paper, a free-surface synthetic schlieren(FS-SS) method was performed to detect the free surface disturbances. It is a purely optical method that uses refraction of light to reconstruct the height changes of water surface. The theory was developed based on Moisy's research, but has mainly been used in small-scale applications like painting and coating industry. Based on the methods and theories of the literature review, an in-depth investigation was conducted to optimize the FS-SS method and verify its feasibility on a relatively large-scale(e.g., wake region of shallow flow). The experimental setup was simplified which is approachable in most laboratories. Through proper experimental setting and an optimized post-processing routine, the quality of image was highly improved and ensured the accuracy of results. A drop test was performed proving the continuity of FS-SS method in the time domain. Also, a comparison test with flow around a cylinder at two speeds showed the ability of FS-SS method to reconstruct the irregular water surface in relative large-scale flow structures.

Three-Dimensional Direct Numerical Simulation of Flow past A Near-Wall Circular Cylinder:Combined Effects of Gap Ratio and Boundary Layer Thickness on Flow Profiles and Pressure Distribution

Three-dimensional direct numerical simulations of the wake flow downstream of a near-wall circular cylinder at different gap ratios and boundary layer thicknesses are carried out by using the iterative immersed boundary method.The non-dimensional gap between the cylinder and the wall,G/D=0.2,0.6 and 1.0,the non-dimensional boundary layer thickness,δ/D=0.0,0.7 and 1.6,the Reynolds number,Re=350,and the aspect ratio of the cylinder,L/D=25are adopted.High-resolution visualizations of the complex vortex structures at differentδ/D and G/D are presented.The transition of the streamwise vortex mode,the combined effects ofδ/D and G/D on the flow statistics,the pressure and shear stress distribution and the hydrodynamic forces are analyzed.Results show that with decreasing G/D and increasingδ/D,the gap flow and its vortex-shedding are significantly weakened,together with an elongated wake and an enlarged low-velocity area near the wall,leading to the wake mode transition from the two-sided to one-sided vortex-shedding.Different relative positions of the cylinder regarding the boundary layer alter the flow features of the shear layers.With an increase inδ/D,the front stagnation point shifts to the upper surface,and the distance between the flow divergence point and the maximum pressure position increases.The mean drag coefficient and r.m.s.values of drag and lift coefficients decrease with a decrease in G/D and an increase inδ/D,while the mean lift coefficient increases with decreasing G/D but decreases with increasingδ/D.

Significance of Nanoparticles Aggregation with Cattaneo-Christov Heat Flux on the Water and Ethylene Glycol Mixture Based MWCNTs-Nanofluid Flow over a Stretching Cylinder

This work aims to analyze the flow of electrically conducting MWCNTs-nanofluid over a stretching cylinder with the aggregation and non-aggregation effects of nanoparticles. The working fluid comprised a combination of water and ethylene glycol, with volumetric proportions of (50:50) considered. Convective boundary constraints and modified Fourier law are implemented in heat transmission assessment. The mathematical flow model is formulated in the form of PDEs and is transformed into ODEs via similarity transformation. Numerical outcomes will be obtained with the use of the bvp4c technique and will be displayed with the help of graphs and tables. The results show that the surface drag coefficient is enhanced in the case of aggregation of nanoparticles whereas heat transfer rate is enhanced in the non-aggregation effect of nanoparticles. Furthermore, the temperature distribution enhances the increasing values of particle volume fraction in the case of aggregation effects of nanoparticles whereas temperature distribution lowers in the case of non-aggregation effect of nanoparticles. .