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.

Tribological Properties of Cylinder Block/Valve Plate Interface of Axial Piston Pump on the Tribometer

The tribological properties of cylinder block/valve plate is an important consideration in the design of axial piston pump.The effect of materials and heat treatment on friction and wear properties has been studied in depth.Engi-neering experiences show that the speed and load also affect the tribological properties,but these have not been systematically analyzed.The purpose of this paper is to evaluate the tribological properties of the commonly used materials(CuPb1 5Sn5 and 38CrMoAl/42CrMo)for cylinder block/valve plate with different heat treatment and con-tact pressure at different speed.During the test,tribometer is used to simulate the contact pattern between the valve plate/cylinder block in axial piston pump,the friction coefficient,wear rate and surface topography are analyzed to evaluate the tribological properties of different types of friction samples at different speed.Results indicate that:(1)contact surface of the samples at 1800 r/min is more prone to adhesive wear than those at 500 r/min;(2)in the terms of wear resistance,quench-tempered and nitrided 38CrMoAl(38CrMoAl QTN for short)is better than quench-tem-pered and nitrided 42CrMo,although they are all commonly used materials in the axial piston pump;(3)2.5 MPa is the critical contact pressure of the interface between valve plate made of 38CrMoAl QTN and cylinder block made of CuPb1 5Sn5 on the tribometer,which implies the pressure bearing area at the bottom of the cylinder block should be carefully designed;(4)the valve plate/cylinder block made of 38CrMoAl QTN/CuPb15Sn5 exhibits good tribological properties in a real axial piston pump.This research is useful for the failure analysis and structural optimization design of the valve plates/cylinder block.

The Interface Stress Field in the Elastic System Consisting of the Hollow Cylinder and Surrounding Elastic Medium Under 3D Non-Axisymmetric Forced Vibration

The paper develops and employs analytical-numerical solution method for the study of the time-harmonic dynamic stress field in the system consisting of the hollow cylinder and surrounding elastic medium under the non-axisymmetric forced vibration of this system.It is assumed that in the interior of the hollow cylinder the point-located with respect to the cylinder axis,non-axisymmetric with respect to the circumferential direction and uniformly distributed time-harmonic forces act.Corresponding boundary value problem is solved by employing of the exponential Fourier transformation with respect to the axial coordinate and by employing of the Fourier series expansion of these transformations.Numerical results on the frequency response of the interface normal stresses are presented and discussed.

Geometric shapes of the interface surface of bicomponent flows between two concentric rotating cylinders

In this paper, the shape problem of interface of bicomponent flows between two concentric rotating cylinders is investigated. With tensor analysis, the problem is reduced to an energy functional isoperimetric problem when neglecting the effects of the dissipative energy caused by viscosity. We derive the associated Euler-Lagrangian equation, which is a nonlinear elliptic boundary value problem of the second order. Moreover, by considering the effects of the dissipative energy, we propose another total energy functional to characterize the geometric shape of the interface, and obtain the corresponding Euler-Lagrangian equation, which is also a nonlinear elliptic boundary value problem of the second order. Thus, the problem of the geometric shape is converted into a nonlinear boundary value problem of the second order in both cases.

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.

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.

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.

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.

Numerical analysis on three dimensional temperature field of the gap between piston and cylinder

The three dimensional temperature field of the gap between piston and cylinder was ob- tained by numerically solving energy equation. The boundary condition of the equation was given in the form of heat transfer coefficient, instead of solving the temperature field of solid parts. The tem- perature field was calculated both under high speed high pressure condition and low speed low pres- sure condition. The numerical result was compared to experimental result under low speed low pres- sure condition and showed good agreement. It was shown that the influence of heat transfer coeffi- cient on t＇tim temperature was significant. The adiabatic condition was reasonable under low speed low pressure condition, but invalid under high speed high pressure condition. It was a good way to describe the influence of solid parts on temperature using heat transfer coefficient but avoiding sol- ving the temperature field of solids parts.

Coupling problem between the dynamical and tribological behaviors in the piston-liner systems of multi-cylinder IC engines

This paper deals with the coupling problem between the dynamic behaviors and the tribological behaviors of the piston-liner systems in multi-cylinder internal combustion engines. Firstly, based on the correction of some errors in the equation of piston secondary motion, which have been employed by many authors for several years, a detailed mathematical model for the coupling problem between the dynamical and tribological behaviors in the piston-liner systems of multi-cylinder internal combustion engines is presented. Secondly, the lubrication and friction between the liner and piston in each cylinder is included applying the average flow model of the Reynolds equation. Thirdly, the vibration of each liner is computed through the finite element model of a four-cylinder engine block, by which not only the liner motions caused by the block vibration but also the local vibration and the local static deformation of each liner can be figured out and taken into account. Through theoretical analysis and computation, some conclusions can be drawn as: 1) Both the liner vibration and piston motion are different for different cylinder in a multi-cylinder internal combustion engine, and hence different piston-liner systems will have different tribological behaviors. 2) Different liners have coincident dynamic response on the whole, especially for the lower frequency components. However, differences still exist among the vibrations of different liners, and these differences are mainly owing to the higher frequency components. 3) The impacts of liner vibrations on the tribological behaviors in piston-liner systems are primarily ascribed to its higher frequency components.

Stability analysis of the moving interface in piston- and non-piston-like displacements

From the macroscopic point of view, expressions involving reservoir and operational parameters are established for investigating the stability of moving interface in piston- and non-piston-like displacements. In the case of axisymmetrical piston-like displacement, the stability is related to the moving interface position and water to oil mobility ratio. The capillary effect on the stability of moving interface depends on whether or not the moving interface is already stable and correlates with the wettability of the reservoir rock. In the case of non-piston-like displacement, the stability of the front is governed by both the relative permeability and the mobility ratio.

Experimental Study on Wear Performance and Oil Film Characteristics of Surface Textured Cylinder Liner in Marine Diesel Engine

It is of a vital importance to reduce the frictional losses in marine diesel engines. Advanced surface textures have provided an e ective solution to friction performance of rubbing pairs due to the rapid development of surface engineering techniques. However,the mechanisms through which textured patterns and texturing methods prove beneficial remains unclear. To address this issue,the tribological system of the cylinder liner?piston ring(CLPR) is investigated in this work. Two types of surface textures(Micro concave,Micro V?groove) are processed on the cylinder specimen using di erent processing methods. Comparative study on the friction coe cients,worn surface texture features and oil film characteristics are performed. The results demonstrate that the processing method of surface texture a ect the performance of the CLPR pairs under the specific testing conditions. In addition the micro V?groove processed by CNCPM is more favorable for improving the wear performances at the low load,while the micro?con?cave processed by CE is more favorable for improving the wear performances at the high load. These findings are in helping to understand the e ect of surface texture on wear performance of CLPR.

The Influence of the Imperfectness of Contact Conditions on the Critical Velocity of the Moving Load Acting in the Interior of the Cylinder Surrounded with Elastic Medium

The dynamics of the moving-with-constant-velocity internal pressure acting on the inner surface of the hollow circular cylinder surrounded by an infinite elastic medium is studied within the scope of the piecewise homogeneous body model by employing the exact field equations of the linear theory of elastodynamics.It is assumed that the internal pressure is point-located with respect to the cylinder axis and is axisymmetric in the circumferential direction.Moreover,it is assumed that shear-spring type imperfect contact conditions on the interface between the cylinder and surrounding elastic medium are satisfied.The focus is on the influence of the mentioned imperfectness on the critical velocity of the moving load and this is the main contribution and difference of the present paper the related other ones.The other difference of the present work from the related other ones is the study of the response of the interface stresses to the load moving velocity,distribution of these stresses with respect to the axial coordinates and to the time.At the same time,the present work contains detail analyses of the influence of problem parameters such as the ratio of modulus of elasticity,the ratio of the cylinder thickness to the cylinder radius,and the shear-spring type parameter which characterizes the degree of the contact imperfection on the values of the critical velocity and stress distribution.Corresponding numerical results are presented and discussed.In particular,it is established that the values of the critical velocity of the moving pressure decrease with the external radius of the cylinder under constant thickness of that.

航空活塞发动机气缸体多物理场耦合磨损机理研究

航空活塞发动机气缸体表面摩擦失效是滑动摩擦应力场、气缸体表面温度场和循环多变功率载荷耦合作用的结果。统计分析了航空活塞发动机在多种工况环境下的摩擦磨损润滑状态,绘制了航空活塞发动机气缸体载荷功率谱。通过多变工况确定多物理场加载参数方案,在SRM-4摩擦试验机上给定功率、温度、载荷和滑油量拟耦合摩擦环境测试废旧气缸体。通过检测气缸体表面状态参数,检验拟废旧气缸体摩擦前后的表面状态。通过拟耦合研究了气缸体应力场、温度场、载荷功率变化对气缸体摩擦系数的影响。结果表明:气缸体表面摩擦系数随温度的增加呈指数增加;低温段(92℃)和中温段(145℃)时,摩擦系数对载荷在35~38N时的变化较为敏感,摩擦系数随载荷的增加而增加,磨损形式以疲劳磨损、疲劳点蚀为主;大于38 N后,载荷对摩擦系数的影响较小;高温段(198℃),载荷对摩擦系数的影响程度减小,温度是主要影响因素,摩擦形式由磨粒磨损(两体/三体磨损)转变为粘着磨损。摩擦系数随频率的变化相对较小。

基于改进EEMD-MB1DCNN的船用柴油机缸套-活塞环故障诊断

针对船用中高速柴油机缸套-活塞环振动信号非线性非平稳性以及同类型不同损伤程度故障发生时振动信号时频域特征相似、故障难以识别等问题,利用振动信号辨识故障,提出一种基于改进集成经验模态分解方法和多模块一维卷积神经网络端到端缸套-活塞环故障诊断方法,通过设计固有模态分量IMF信息质量筛选准则对EEMD分解出的IMFs进行重新排序,获得包含更多凸显故障特征成分的重构信号,输入到上述神经网络模型,通过振动信号分析并与现有方法比较,评估所设计IMF信息质量筛选准则与所搭建模型的性能,试验结果显示该方法能准确、有效地识别缸套-活塞环故障类型。在判断该易损件同类型不同磨损程度故障诊断中有较高的准确率,能对故障状况进行有效的特征提取与故障分类。

Review of cylinder block/valve plate interface in axial piston pumps: Theoretical models,experimental investigations, and optimal design

Axial piston pumps have been widely used in aircraft hydraulic systems to supply the system with pressurized fluid. The continuous improvement of the aircraft performance has put forward the demand on aviation piston pumps for high power density, safety, and reliability. The lubricating interfaces in axial piston machines are the key design issue that greatly determines the pump performance and service life. The cylinder block/valve plate interface is one of these critical lubricating interfaces and has received considerable attention from many researchers in the last half century. This study aims to review the state-of-the-art literature on the cylinder block/valve plate interface comprehensively and systematically. First, we introduce various theoretical models developed to investigate the lubrication behaviors of the interface and compare them in terms of their assumptions and limitations. Second, the experimental studies on the cylinder block/valve plate interface are presented comprehensively, where the involved test rigs are divided into three types according to their fidelity levels and measurement functionality. Third, we summarize some typical approaches of structure optimization, surface shaping, and surface strengthening, which help improve the load-carrying and anti-wear capacities of the interface under severe operating conditions. Finally, the challenges and future trends of the cylinder block/valve plate interface research are discussed briefly.

合金灰口铸铁气缸套组织形貌与耐磨性研究

针对5种成分和组织的灰口铸铁气缸套,包括2种贝氏体铸铁气缸套和3种珠光体铸铁气缸套,全面分析了其成分、相组成及硬度等材料特性,将喷钼活塞环与5种合金灰口铸铁气缸套对磨,通过比较各配对副的摩擦磨损性能,获得了喷钼活塞环与5种合金灰口铸铁气缸套的匹配规律。研究结果表明:5种气缸套材料均为由硬质相、基体和石墨构成的复合耐磨结构,各组分的性能、分布及其配比,是决定耐磨性的关键因素。珠光体基体气缸套的磨损量相对稳定,气缸套与活塞环的相对磨损量正常;铸态贝氏体气缸套磨损较轻,配对活塞环的磨损量比珠光体气缸套大;贝氏体气缸套和活塞环的磨损均量很小。

水压驱动两级提拉式水下发射装置内弹道建模

针对大深度环境水下发射技术需求,提出一种利用水压驱动两级提拉式水下新型发射方案。利用大深度环境高压水驱动两级活塞实现武器快速发射。建立武器出管过程动力学模型,开展高压水驱动方案原理验证试验,并与高压气体驱动方案进行了对比分析。研究结果表明:水压驱动与气体驱动方案的内弹道结果基本一致,高压水发射方案在大深度环境具有显著优势;加速度峰值出现在发射瞬时和级间转换过程,级间转换过程武器加速度存在显著的陡变现象;水下发射武器出管过程弹道预报结果得出,在发射水深100~500 m条件下,武器出管过程最大速度范围为7.4~15.3 m/s,最大加速度小于100 m/s 2;研究结果验证了水压驱动两级活塞式发射方案的可行性,为装置的进一步研制开发提供了设计依据。

基于激光熔覆的缸套表面梯度材料制备及其摩擦学性能研究

目的研究功能梯度材料对缸套表面的抗磨减摩作用,提升缸套-活塞环配副的摩擦学性能。方法通过激光打标机在缸套表面制备具有30°角规则纹理排布的凹槽,在凹槽内采用同轴送粉的方式熔覆镍含量不同的铁基粉末,分析熔覆合金层的金相组织,并利用往复式摩擦磨损试验机研究在一定载荷压力下功能梯度材料缸套的摩擦学性能。结果熔覆层金相组织呈现梯度排布,熔覆层与基体材料分子原子交互扩散形成良好的冶金结合。牌号为350、镍质量分数为4.2%、铁质量分数80%的粉末所制备的功能梯度材料,减摩效果最为明显,相比未经处理的对照组,平均摩擦因数降幅为25.4%,且该组在试验中接触电阻的平均值最大,相比对照组提升了63.45%。牌号为330、镍质量分数为9%、铁质量分数为70%的粉末制备的缸套,表面支撑指数最高为0.78,相比于未处理的对照组,增幅达到35%,且试验组活塞环经摩擦后,磨损量均小于对照组。结论制备了30°角分布的功能梯度材料,能使得缸套-活塞环摩擦学系统在工作过程中摩擦副的润滑油膜厚度更厚,且在运行过程中更稳定,以减少摩擦力和降低摩擦因数。同时,增强其支撑能力和储存润滑油的能力,使所制备的缸套摩擦因数显著降低。牌号为350的材料,改善摩擦学性能的效果最优。