A tool for mass transfer evaluation in packed-bed columns for chemical engineering students

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy).The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved.The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application.After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.     

Digital twin-based analysis of volumetric error mapping procedures

The evaluation of the volumetric accuracy of a machine tool is an open challenge in the industry, and a wide variety of technical solutions are available in the market and at research level. All solutions have advantages and disadvantages concerning which errors can be measured, the achievable uncertainty, the ease of implementation, possibility of machine integration and automation, the equipment cost and the machine occupation time, and it is not always straightforward which option to choose for each application. The need to ensure accuracy during the whole lifetime of the machine and the availability of monitoring systems developed following the Industry 4.0 trend are pushing the development of measurement systems that can be integrated in the machine to perform semi-automatic verification procedures that can be performed frequently by the machine user to monitor the condition of the machine. Calibrated artefact based calibration and verification solutions have an advantage in this field over laser based solutions in terms of cost and feasibility of machine integration, but they need to be optimized for each machine and customer requirements to achieve the required calibration uncertainty and minimize machine occupation time.This paper introduces a digital twin-based methodology to simulate all relevant effects in an artefact-based machine tool calibration procedure, from the machine itself with its expected error ranges, to the artefact geometry and uncertainty, artefact positions in the workspace, probe uncertainty, compensation model, etc. By parameterizing all relevant variables in the design of the calibration procedure, this simulation methodology can be used to analyse the effect of each design variable on the error mapping uncertainty, which is of great help in adapting the procedure to each specific machine and user requirements. The simulation methodology and the analysis possibilities are illustrated by applying it on a 3-axis milling machine tool.     

An integrated model for analysing the effects of ultrasonic vibration on tool torque and thermal processes in friction stir welding

An integrated model of ultrasonic vibration enhanced friction stir welding (UVeFSW) is developed by integrating the thermal-fluid model with the ultrasonic field model and tool torque model. The tool torque and the heat generation rate at tool/workpiece contact interfaces are coupled with the interfacial temperature, strain rate and ultrasonic energy density. The model is used in quantitatively analysing the effects of ultrasonic vibration on tool torque and thermal processes in friction stir welding (FSW). The results show that ultrasonic vibration reduces the flow stress, which results in a decreasing of tool torque, interfacial heat generation rate and interfacial temperature. The complicated interaction of ultrasonic energy with the thermal processes in FSW leads to a gentle thermal gradient and an enhanced plastic material flow in UVeFSW. The model is validated by a comparison of the calculated thermal cycles and tool torque at various welding parameters with the experimentally measured ones.     

密文策略属性加密中的撤销控制方案

在云环境下使用数据共享功能时，由于云环境的复杂性，需要对数据进行安全保护和访问控制，这就要求使用加密机制。基于密文策略属性的加密（CP-ABE）是当前广泛使用的加密机制，它可以根据用户的属性来设置访问权限，任何具有合格访问权限的用户都可以访问数据。然而云是一个动态环境，有时可能只允许具有访问权限用户中的一部分用户访问数据，这就需要用户权限的撤销机制。然而，在CP-ABE中，访问权撤销或用户撤销是一个冗长且代价高昂的事件。所提出方案根据对CP-ABE流程的改进，在原密文中嵌入了可灵活控制的用户个人秘密，使得用户权限撤销时既不要求使用新访问策略的用户撤销数据，也不要求对数据进行重新加密，大幅减少撤销时的计算成本。与知名CP-ABE撤销方案对比，所提出方案的计算成本更低且具有良好的安全性。     

数据驱动的机床等待过程节能方法研究

为了降低机床等待过程中的能耗，提出了一种实时数据驱动的机床等待时间预测与节能控制方法。首先，建立了射频识别驱动的生产进度评估方法，并以生产进度数据作为输入，构建了基于堆栈降噪自编码的机床等待时间预测模型；其次，依据预测的机床等待时间，提出了机床状态切换方法，以降低机床能耗；最后，通过一个电梯零部件制造车间的案例分析，表明该方法的预测误差仅为4.1%，同时将机床等待过程能耗降低了57%，实现了制造车间的节能减排。     

二层沟槽织构对机床导轨表面润滑特性的影响

通过构建二层沟槽织构模型，仿真研究沟槽织构表面的流体动力效应。结果表明：沟槽容积相同时，与单层沟槽相比，二层沟槽的平均油膜压力可以达到单层沟槽的2.31倍；保持二层沟槽的量纲一总深度[β]1、第一层沟槽量纲一宽度[α]1不变时，随着第二层量纲一深度[β]2的增大，平均油膜压力先增大后减小，[β]2为4.4时，平均油膜压力达到最大值；第二层沟槽的量纲一宽度[α]2从0.25增大到0.45时，沟槽内的旋涡区也随之增大，平均油膜压力逐渐减小。     

水力旋冲钻井工具破岩影响因素模拟及应用

常规的冲击钻井工具不能满足井眼轨迹控制要求、使用寿命有限、缓解脱压不显著等问题,影响了在定向井钻井中的推广应用。建立ø215.9 mm PDC钻头和岩石的有限元模型,分析钻井参数对破岩效率的影响规律,结果表明:冲击频率为17.5 Hz和35 Hz时,破岩效率最优; 破岩效率随钻压增大而增加,而后变化逐渐平缓; 破岩效率随钻头转速增大而增加; 破岩效率随冲击载荷的增加变化平缓。据此研制了新型水力旋冲钻井工具。现场试验表明,该工具符合定向水平井“一趟钻”工艺要求,使机械钻速提高56%,使用寿命达150 h,MWD信号正常。     

渤海油田浅层沉砂卡钻处理新技术

为防止渤海油田因井漏而造成的沉砂卡钻钻井事故再次发生,以垦利10-4A10井为例,介绍了该井的基本情况,并对该井因漏致卡过程进行了详细描述。经过分析讨可知:大量岩屑堆积在339.7 mm(133/8英寸)套管鞋附近和井壁坍塌掉块两者共同作用,造成钻具因沉砂而卡钻。提出“微扩孔工具+随钻堵漏工具”扩孔解卡新工艺,并成功解卡被卡钻具,保证了海上油气田钻井安全和钻井时效。该工艺在国内首次成功应用,为解决沉砂卡钻事故提供了新思路。     

Void region restriction for additive manufacturing via a diffusion physics approach

A longstanding challenge in additive manufacturing (AM), the presence of void regions in additively manufactured components, causes two main issues: the enclosing of build material powder in powder bed fusion techniques and limiting tool access in critical post-processing operations to remove sacrificial support structures. As topology optimization has embraced and overcome many of the obstacles of incorporating AM constraints into the underlying numerical optimization statement, there exist few solutions that directly address this fundamental void region issue. By developing computationally efficient and effective solutions to this problem, the integration of these two advanced technologies can be fully realized. Drawing on inspiration from the principles of diffusion physics, a particle diffusion void restriction (PDVR) method is presented in this work that is capable of encouraging the optimization scheme to generate final designs that are fully accessible. Additionally, this method empowers the user to choose the type of post-processing method to clear support material (eg, three-axis or five-axis milling operations, number and orientation of part set-ups) and, therefore, quantify the level of costs associated with the post-processing operation. The PDVR optimization framework is demonstrated on multiple two- and three-dimensional test problems, with physically manufactured examples depicting the real-world benefits this method admits.