微胶囊化肉碱的缓释性能

研究了微胶囊化肉碱的肠溶性 ,并对其在模拟肠液中的释放动力学过程进行了初步探讨 ,发现微胶囊化肉碱在释放过程的前 2 0min遵循一级反应动力学 .     

耐230℃高温海水钻井液室内实验研究

为了解决深海油气井工程和大洋科学钻探深部高温井段钻井液流变稳定性和护壁性能等变差问题,以复合粘土为造浆材料,通过优选抗温抗盐降滤失剂、防塌剂和高温稳定剂等关键处理剂及钻井液配方优化研究,研发了一套耐230℃高温海水钻井液配方。采用高温高压流变仪、六速旋转粘度计和高温高压滤失仪等仪器,开展耐230℃高温海水钻井液的综合性能评价,如热稳定性、高温流变性等。实验结果显示,密度1.5 g/cm³的钻井液在230℃老化16 h前后,表观粘度变化率为2.5%,高温高压滤失量为23 mL。研究结果表明,该海水钻井液抗温可达230℃,具有良好的抗高温稳定性、高温流变性能以及较低的高温高压滤失量,可满足深海高温硬岩钻探要求。     

CrNx梯度薄膜在不同水溶液中的腐蚀及摩擦学特性

采用增强阴极弧磁控溅射法在Si(100)片和WC硬质合金上制备了CrNx梯度薄膜。用X射线衍射仪和扫描电子显微镜分析了CrNx梯度薄膜的结构及微观形貌;在人体模拟体液及海水中分别利用CHI660D电化学工作站及球-盘摩擦磨损试验机对CrNx梯度薄膜的电化学特性及CrNx/Al2O3的摩擦学特性进行了研究。结果表明:CrNx梯度薄膜在海水中表现出更优异的耐腐蚀性,CrNx梯度薄膜在人体模拟体液中的摩擦因数随载荷的增加而增大(0.23~0.33),而在海水中的摩擦因数则是先增大后减小(0.26~0.30)。低载荷下,对摩副在人体模拟体液中的磨损程度更低,当载荷增大至12N时,2种润滑环境下的磨损程度相当。     

Simulation of thermophysical flow in axisymmetric nozzle with expansion chamber

Axisymmetric nozzle flows with a free‐jet expansion are simulated considering several substances and several flow conditions, and the thermophysical properties in the nozzle and the free‐jet region are predicted. The present numerical method is based on the preconditioning method developed by Yamamoto and the mathematical models of thermophysical properties of the substances. As numerical examples show, gas flows of carbon dioxide, water, and nitrogen under a subcritical pressure condition are first calculated. Calculated distances to the Mach disk are compared with the experimental results, and also the density distributions are compared among these three substances. Second, carbon dioxide flows while changing the pressure from subcritical to supercritical values are calculated and the effect of pressure on the flow field is investigated. Third, flows of water vapor with and without nonequilibrium condensation are calculated and the effect of condensation on the flow field is investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

The influence of solid-phase concentration on the performance of electrorheological fluids in dynamic squeeze flow

The yield stress of electrorheological (ER) fluids increases by orders of magnitude when electric field is applied across them. In the absence of the field, ER fluids behave as Newtonian fluids. This paper is concerned with an experimental investigation to determine the rheological performance of ER fluids, consisting of a dielectric liquid carrier with a range of solid-phase concentration. The ER fluid was contained in a squeeze cell, which during motion subjects the fluid to both compressive and tensile loading. The results were analysed in terms of the capacity for the transmission of imposed forces across the fluid and showed a great dependence on the applied D.C voltage and the weight fraction of the dispersed solid-phase. In addition, the implications of the results to vibration control, where the ER fluid is employed in an engine mount, are discussed.     

140MPa压裂泵液缸强度及寿命预测分析

针对某厂新设计的140 MPa高压压裂泵液缸,用ANSYS/ANSYS FE-SAFE有限元分析软件计算出了静力强度及疲劳寿命分布。计算结果显示,液缸在140 MPa内压工作载荷下产生的最大Von Mises应力为630 MPa,位于缸腔与柱塞腔相贯部位拐角处,内腔平均应力〈350MPa,液缸整体静强度满足要求。但是在循环载荷冲击作用下,相贯部位拐角处疲劳寿命低,疲劳安全系数不够,短时间内会发生破坏。提出增大相贯部位倒圆角半径,采用自增强等强化处理,可提高液缸使用寿命。     

Recent progress in smart polymer composite particles in electric and magnetic fields

Electrorheological (ER) and magnetorheological (MR) fluids based on electro‐ and magneto‐responsive particles, respectively, are smart suspensions with the ability to undergo phase transitions from a liquid‐like to a solid‐like state as a result of stimuli of an electric or magnetic field. The application of polymer composite materials rather than pure polymeric or inorganic materials is aiming to solve the problems in the use of both ER and MR materials, such as low activity, physical and chemical stability, and production cost. Various fabrication methods of polymer composite materials with electro‐activity or magneto‐activity developed and effectively applied in this field to boost the wide commercialization of both ER and MR fluids are briefly reviewed in this perspective. © 2012 Society of Chemical Industry     

Thermodynamic analysis of high-temperature regenerative organic Rankine cycles using siloxanes as working fluids

A recent novel adjustment of the Span-Wagner equation of state for siloxanes, used as working fluids in high-temperature organic Rankine cycles, is applied in a mathematical model to solve cycles under several working conditions. The proposed scheme includes a thermo-oil intermediate heat circuit between the heat source and the organic Rankine cycle. Linear and cyclic siloxanes are assayed in saturated, superheated and supercritical cycles. The cycle includes an internal heat exchanger (regenerative cycle), although a non-regenerative scheme is also solved. In the first part of the study, a current of combustion gases cooled to close to their dew point temperature is taken as the reference heat source. In the second part, the outlet temperature of the heat source is varied over a wide range, determining appropriate fluids and schemes for each thermal level. Simple linear (MM, MDM) siloxanes in saturated regenerative schemes show good efficiencies and ensure thermal stability of the working fluid.     

Numerical prediction of three-dimensional time-dependent viscoelastic extrudate swell using differential and algebraic models

The dynamic behavior of a droplet on a solid surface is simulated by the lattice Boltzmann method (LBM) for two-phase fluids with large density differences; the wetting boundary condition on solid walls is incorporated in this simulation. By using the method, the dynamic behavior of a droplet impinging on a horizontal wall is investigated in terms of various Weber numbers. The dynamic contact angle, the contact line velocity, and the wet length are calculated, and found to be in good agreement with available experimental data. In addition, the method is applied to simulations of the collision of a falling droplet with a stationary droplet on a solid surface. The behavior of the droplets and the mixing process during their collision are simulated in terms of various impact velocities and several static contact angles on the solid surface. It is seen that mixing occurs around the rim of the coalescent droplet due to the circular flows. Also, the relationship between the mixing rate of the primary coalescent droplet and Weber number is investigated.     

Fluid flow characterization with tube viscometer data

Pressure gradients and the corresponding mass flow rates of five different non-Newtonian fluid foods: 1% solutions of sodium alginate and CMC, 1.5% CMC solution, two different tomato ketchups, oyster sauce, in four different diameter stainless steel tubes ranging from 7.51 to 16.34 mm i.d. were recorded using a tube viscometer capable of operating in both transient and continuous flow modes. The flow was confined to the laminar flow regime and appreciable slippage occurred in all cases. Power law parameters for the tube flow obtained from the plots of wall shear stress versus apparent wall shear rate are presented for various time-independent fluids in different diameter tubes in original and slip-corrected forms. Such experimental data should prove useful in developing an understanding of flow characterization of non-Newtonian fluids.