Effects of lubricant additives on the performance of hydrodynamically lubricated journal bearings

A non-Newtonian rheological model to investigate theoretically the effects of lubricant additives on the steady state performance of hydrodynamically lubricated finite journal bearings is introduced. In this model, the non-Newtonian behavior resulting from blending the lubricant with polymer additives is simulated by Stokes couple stress fluid model. The formed boundary layer at the bearing surface is described through the use of a hypothetical porous medium layer that adheres to the bearing surface. The Brinkman-extended Darcy equations are utilized to model the flow in the porous region. A stress jump boundary condition is applied at the porous media/fluid film interface. A modified form of the Reynolds equation is derived and solved numerically using a finite difference scheme. The effects of bearing geometry, and non-Newtonian behavior of the lubricant on the steady-state performance characteristics such as pressure distribution, load carrying capacity, side leakage flow, and coefficient of friction are presented and discussed. The results showed that lubricant additives significantly increase the load carrying capacity and reduce both the coefficient of friction and the side leakage as compared to the Newtonian lubricants.     

复合织构化压裂泵柱塞密封副动压润滑性能仿真研究

为改善压裂泵柱塞密封副的摩擦磨损性能,在压裂泵柱塞密封副表面建立不同的复合表面织构(不同复合织构类型、不同分布方式、不同截面形状等),并在结合柱塞密封副几何结构特征、压力边界条件及雷诺方程的基础上,建立织构化柱塞密封副动压润滑理论模型,采用有限差分对雷诺方程进行求解,仿真分析复合织构对柱塞密封副动压润滑性能的影响规律。数值仿真研究结果表明:复合织构对动压润滑性能的影响与外织构深度有密切关系;内织构为凹坑或凸起,以及内织构为不同截面形状的复合织构,主要是通过影响织构平均深度与摩擦副间隙的大小关系,而对复合织构的动压润滑性能造成不同的影响规律;内织构分布于外织构右侧(润滑介质入口一侧)对复合织构动压润滑性能的提升最大。     

大牛地气田大12-大66井区沉积微相与储层产能关系

以大牛地气田大12—大66井区为研究对象,基于物质供给和沉积水动力条件、河道结构与特征,探讨了沉积微相纵向结构与产能分布之间的成因关系,沉积微相横向结构与产能分布之间的内在关系。研究表明,物质供给和沉积水动力条件的组合关系是影响沉积微相纵向产能分布规律,其中物质供给充分、稳定的强水动力条件下,主要为中高产气层;分流河道微相中心位置,测试产能相对稳定,中高产气层分布比较多。分流河道微相边部,测试产能有不稳定的特点。两个强水动力沉积的河道交汇处,是中、高产气层的密集发育区。另外,曲流化的固定河道,因复杂化而形状变化大、难钻遇,但潜力大。不稳定河道,储层整体产能低,但强水动力沉积区仍具挖潜价值。研究结果与大12—大66井区生产测试结果吻合。     

Effects of Load Direction on Performance of Tiliting Pad Journal Bearings

At the previous works for tilting journal pad bearings （TPJBs）, most TPJBs are designed to operate with the load either directly on-pad（LOP） or directly between-pad（LBP）. However, in practice, in some cases, the load direction can change dramatically in operation. With the current requirements for the analysis of dynamic characteristics of the rotor-bearing systems, the effects of the load direction on the bearing performance must be known. So, in this paper, the effects of load direction on the static and dynamic characteristics of TPJBs are obtained with theoretical analysis based on the hydrodynamic lubrication theory, and the influence of load direction on the performance of TPJBs in different structure and operating parameters is also analysed. The results show that the load direction has considerable effects on the static and dynamic characteristics of the TPJBs, especially for the TPJBs that are operating under heavy load and high rotor speed. And for the operating condition that load direction changed rapidly, TPJBs with more pads, smaller length to diameter ratio, larger clearance ratio and smaller perload ratio can reduce the performance fluctuation with the variation of load direction.     

Self-swarming robots that exploit hydrodynamical interaction

Although numerous swarm robotic systems have already been developed, they have exhibited limited adaptability. This was partly because the previous researchers designed the control schemes on the basis of informational interaction, without considering the physical effects of the environment. To tackle this problem, we employ an unconventional approach: we design a control scheme for swarm robots based on their physical interaction in a hydrodynamic field, inspired by biological swarming. Through simulations using a smoothed particle hydrodynamics method, we show that the proposed control scheme allows agents to form an ordered swarm in response to their environment.     

Hydrodynamic behaviour of a new permeable pavement material under high rainfall conditions

Permeable pavements are among the most effective alternative solutions for sustainable stormwater management. They decrease impervious surfaces in urban areas, reduce the risk of flooding under high rainfall conditions and protect the natural environment against stormwater pollution. In a view to ensuring sustainable stormwater management, a new eco-material has been designed for producing permeable pavements. This material is a mixture of construction wastes (crushed concrete) and organic matter (compost). The crushed concrete is the structural support and the compost is used for retention and the biological treatment of stormwater pollution. The purpose of the research work presented in this paper was to evaluate the hydrodynamic behaviour of a new permeable pavement material under high rainfall conditions. The experimental approach adopted for this research study is a temporal moment analysis. Therefore, for the experimental study, we simulated high rainfall with a return period of 10 years (Torreilles in 2001, France). The rainfall data were provided by Meteo France. The rainfall was maintained at an intensity of 126 mm/h, corresponding to a flow rate of 16 l/h at laboratory apparatus scale. Then, the flow rate was increased three times, to 25 l/h, 50 l/h and finally 100 l/h to subject the material to extreme conditions.     

新型阶梯式浅吃水单立柱浮式风机平台水动力分析

常规的单立柱式(Spar)风力发电机平台,在水深较浅区域工作时,结构本身受吃水限制,工作效果较差。常规Spar重心较低,具有良好的稳定性,但是由于它往往具有超过100 m的吃水,因此使其不能应用于中近海域(水深小于100 m)。可设计研究一种适用于中国东海不超过100 m水深的中近海域新型浮式风机平台以解决此问题。针对NREL 5MW风机能应用于100 m水深的情况,对50 m吃水的新型Spar(SJTU-S4)及其系泊系统进行了概念设计研究。利用商业软件建立水动力模型,进行数值仿真,同时设计缩比模型试验,在上海交通大学海洋工程国家重点实验室(SKLOE)进行水动力性能测试。结果表明,本文研究的新阶梯式浅吃水单立柱浮式风机平台在100 m水深、多种海洋波浪环境下,通过试验和仿真验证,能够具有良好的运动响应,为风机提供较好的工作条件。     

Hydrodynamic Phonon Transport Perpendicular to Diffuse-Gray Boundaries

In this paper, we examine the application of an ideal phonon-hydrodynamic material as the heat transfer medium between two diffuse-gray boundaries with a finite temperature difference. We use the integral-equation approach to solve a modified phonon Boltzmann transport equation with the displaced Bose–Einstein distribution as the equilibrium distribution between two boundaries perpendicular to the heat transfer direction. When the distance between the boundaries is smaller than the phonon normal scattering mean free path, our solution converges to the ballistic limit as expected. In the other limit, we find that, although the local thermal conductivity in the bulk of the hydrodynamic material approaches infinity, the thermal boundary resistance at the interfaces becomes dominant. Our study provides insights into both the steady-state thermal characterization of phonon-hydrodynamic materials and the practical application of phonon-hydrodynamic materials for thermal management.     

Model of a polymer chain twisted inside a statistical segment. Poly(3‐hexylthiophene) in chloroform solutions

A set of hydrodynamic methods in extremely dilute solutions (determination of intrinsic viscosity [η ], translational diffusion D and flotation in a centrifugal field s ) was used in the studies of conformational properties, dimensions and equilibrium rigidity of individual molecules of a series of samples of poly(3‐hexylthiophene). Absolute molecular masses M _sD were determined. The Mark–Kuhn–Houwink equations for the range of M _sD from 2240 to 15 300 g mol^?1 are given. For the first time, an analysis of conformational properties and equilibrium flexibility of poly(3‐hexylthiophene) molecules was carried out using the model of a statistical segment containing a twisted polymer chain. © 2017 Society of Chemical Industry