Decoupling Control of Fluid Catalytic Cracking Unit

This study presents a decoupling control scheme of fluid catalytic cracking unit to account for the high interaction between two temperature control loops. The feed flow rate load disturbance is introduced to test the proposed decoupling control scheme. Through simulation study shown that the decoupling is effective, stable and it presents advantage over controller without decoupler. Also, this scheme is able to offer good dynamic performance for most disturbances.

Failure analysis of corrosion cracking and simulated testing for a fluid catalytic cracking unit

The failure of a fluid catalysis and cracking unit (FCCU) in a Chinese refinery was investigated by using nondestructive detection methods, fracture surface examination, hardness measurement, chemical composition and corrosion products analysis. The results showed that the failure was caused by the dew point nitrate stress corrosion cracking. For a long operation period, the wall temperature of the regenerator in the FCCU was below the fume dew point. As a result, an acid fume NOx-SOx-H2O medium present- ed on the surface, resulting in stress corrosion cracking of the component with high residual stress. In order to confirm the relative conclusion, simulated testing was conducted in laboratory, and the results showed similar cracking characteristics. Finally, some sug- gestions have been made to prevent the stress corrosion cracking of an FCCU from re-occurring in the future.

Simulation of fluid-structure interaction in a microchannel using the lattice Boltzmann method and size-dependent beam element on a graphics processing unit

Fluid-structure interaction （FSI） problems in microchannels play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow in microchannel considering FSI. The bottom boundary of the microchannel is simulated by size-dependent beam elements for the finite element method （FEM） based on a modified cou- ple stress theory. The lattice Boltzmann method （LBM） using the D2Q13 LB model is coupled to the FEM in order to solve the fluid part of the FSI problem. Because of the fact that the LBM generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallel computing. The simulations are carried out on graphics processing units （GPUs） using computed unified device architecture （CUDA）. In the present study, the governing equations are non-dimensionalized and the set of dimensionless groups is exhibited to show their effects on micro-beam displacement. The numerical results show that the displacements of the micro-beam predicted by the size-dependent beam element are smaller than those by the classical beam element.

Influence of Surrounding Structures upon the Aerodynamic and Acoustic Performance of the Outdoor Unit of a Split Air-Conditioner

DC-inverter split air-conditioner is widely used in Chinese homes as a result of its high-efficiency and energy-saving. Recently, the researches on its outdoor unit have focused on the influence of surrounding structures upon the aerodynamic and acoustic performance, however they are only limited to the influence of a few parameters on the performance, and practical design of the unit requires more detailed parametric analysis. Three-dimensional computational fluid dynamics（CFD） and computational aerodynamic acoustics（CAA） simulation based on FLUENT solver is used to study the influence of surrounding structures upon the aforementioned properties of the unit. The flow rate and sound pressure level are predicted for different rotating speed, and agree well with the experimental results. The parametric influence of three main surrounding structures（i.e. the heat sink, the bell-mouth type shroud and the outlet grille） upon the aerodynamic performance of the unit is analyzed thoroughly. The results demonstrate that the tip vortex plays a major role in the flow fields near the blade tip and has a great effect on the flow field of the unit. The inlet ring＇s size and throat＇s depth of the bell-mouth type shroud, and the through-flow area and configuration of upwind and downwind sections of the outlet grille are the most important factors that affect the aerodynamic performance of the unit. Furthermore, two improved schemes against the existing prototype of the unit are developed, which both can significantly increase the flow rate more than 6 %（i.e. 100 m3·h～（-1）） at given rotating speeds. The inevitable increase of flow noise level when flow rate is increased and the advantage of keeping a lower rotating speed are also discussed. The presented work could be a useful guideline in designing the aerodynamic and acoustic performance of the split air-conditioner in engineering practice.

Counter-Rotating Type Horizontal-Axis Bidirectional Propellers for Tidal Stream Power Unit

Tidal stream power units with horizontal-axis propellers are one of promising technologies for generating the renewable green energy. The ebb and flow require that the power unit must operate in bidirectional tidal streams. Hence a tidal stream power unit with counter-rotating type horizontal-axis bidirectional propellers is proposed in this paper. The blades with fully-symmetrical hydrofoils were optimized numerically. The output and flow conditions predicted by the computational fluid dynamics simulations are compared with the results of the wind tunnel experiments at the higher tip speed ratios, which are of expected usual operating conditions of this unit. The numerical and experimental results show good agreements. It is also confirmed that the flow discharged from the counter-rotating type propellers has no swirling component, though the single propeller generates the unacceptable swirling component.

Pulsed Sound Waves in a Compressible Fluid

The propagation along oz of pulsed sound waves made of sequences of elementary unit pulses U (sin τ) where U is the unit step function and τ = kz -ωt is analyzed using the expansion of U (sin τ) and of the Dirac distribution δ (sin τ) in terms of τ-nπ where n is an integer. Their properties and how these pulsed sound waves could be generated are discussed.

A Numerical Prediction of Tip Vortices from Tandem Propellers in the Counter-Rotating Type Tidal Stream Power Unit

Ocean energy has a potential of providing a large amount of renewable energy around the world. One of the forms of ocean energy, tidal stream power is widely recognized as the continuous, predictable and eco-friendly ocean energy source. Unique tandem propellers that can counter-rotate have been designed to generate electric power effectively from a tidal stream. This type of power unit has several advantages compare to the conventional unit with a single propeller. At the design of the tidal stream power unit, it is important to investigate the structure of the tip vortex tubes shedding to predict the load of the propeller. In this research, we investigated the tip vortex shedding using the CFD method for the conventional single propeller and counter-rotating type tandem propellers and estimated the performance efficiency using RANS (Reynolds Averaged Navier-Stokes) model and we confirmed the limitation of RANS model on the calculation of the tip vortex stretching.

基于门控循环单元网络的低阻油层测井流体识别方法

研究区块低阻油层发育广泛,油层和水层的电阻率相差不大,导致测井流体识别较为困难。为了有效识别低阻油层,采用少数类过采样技术(synthetic minority oversampling technique,Smote)对油水同层,油层等少数类样本进行过采样使数据集均衡;并利用门控循环单元(gated recurrent unit,GRU)网络模型进行低阻油层的流体识别。通过相关性分析确定自然伽马(GR)、深侧向电阻率(RD)、密度(DEN)等8条测井曲线数据作为输入训练模型,应用于中实际资料中,并将GRU与传统RNN和其他3种机器学习算法对比。结果表明:序列数据模型的流体识别效果比传统机器学习模型好,且基于Smote-GRU的流体识别模型的符合率达到89.5%,相对传统循环神经网络(recurrent neural network,RNN)的81.1%,取得了较好的应用效果。通过对照试验还证实了Smote算法提高了分类器对少数类样本的识别率。所提出的方法可为样本不均衡的低阻油层的流体识别提供参考。

铜阳极板残极洗涤机组设计与多喷头清洗仿真研究

本文根据残极洗涤机组的功能和主要结构,对残极洗涤系统进行了改进,成功解决了原有设备洗涤效果差的问题,并用ANSYS Fluent软件对残极洗涤机组的核心设备残极洗涤系统进行流体力学仿真,对比9个喷头和11个喷头不同喷头下的洗涤效果。结果表明采用11个喷头的情况下残极板表面无残酸和残极泥,冲洗后残极板表面干净整洁,并且冲洗的水资源经沉淀后可以循环利用。残极洗涤机组设备自动化程度高,操作简单,可有效提高生产率,降低劳动强度,改善铜电解车间的生产工艺条件。

基于改进TOPSIS的石化装置实时状态评估

针对石化装置运行工况数据积累量有限,难以满足装置运行状态传统评估方法数据需求的问题,提出基于改进逼近理想解法(TOPSIS)的状态评估方法,避免了对装置历史运行数据的依赖。该基于改进TOPSIS的评估方法,首先根据现场专家经验和工艺卡片过程指标的控制限,确定TOPSIS的正、负理想解;然后根据装置运行参数特点,形成固定值型和固定区间型指标,并建立相应的评估标准。采用该基于改进TOPSIS的评估方法对某炼油厂催化裂化装置反应-再生系统的异常工况进行了分析,结果表明该评估方法可以实现对催化裂化装置反应-再生系统的运行状态进行量化监测。

床旁心肺超声在ICU心脏术后患者早期液体评估中的临床研究

目的:探究床旁心肺超声在心脏术后患者早期液体评估中的临床应用价值。方法:选择2020年1月~2022年12月太和县人民医院收治的82例心脏外科手术患者为研究对象,按照随机数字表法分为观察组(n=41)和对照组(n=41)。两组患者术后均给予标准化治疗,对照组根据中心静脉压指导早期补液,观察组则基于床旁心肺超声指导患者早期补液,对比两组患者术后24 h基础生命体征指标、心功能指标及补液量变化,跟踪记录两组患者的机械通气时间、血管活性药物使用时间及ICU住院时间,随访1个月对比两组患者的预后情况。结果:观察组患者术后24 h时的心率、呼吸频率及补液量均低于对照组(P<0.05),平均动脉压高于对照组(P<0.05);观察组术后机械通气时间、血管活性药物使用时间及ICU住院时间均短于对照组(P<0.05);观察组术后无二次手术病例,对照组1例二次手术,观察组术后1个月无死亡病例,对照组术后1个月1例患者死亡。结论:心肺联合超声目标导向液体管理在ICU心脏术后患者中应用效果良好,其有助于减少心脏术后患者术后输液量及缩短机械通气时间、血管活性药物使用时间及ICU住院时间。

催化裂化装置旋风分离器的锥体器壁磨损穿孔分析

某1.0 Mt/a催化裂化装置在运行过程中,再生器旋风分离器的锥体发生了器壁磨损穿孔损坏。旋风分离器器壁磨损穿孔后导致分离效率下降,出现了比较严重的催化剂跑损故障。为此,依据气固两相流的磨损模型和气固旋流流场特点分析了磨损穿孔问题发生的过程。催化剂在旋风分离器内部的离心力和重力的作用下聚集在器壁表面形成了下行的螺旋灰环。当螺旋灰环运动到锥体段时,灰环的加速旋转流动使灰环螺旋角减小,在器壁表面形成一个悬浮的旋转灰环,同时灰环的颗粒浓度也增大,对器壁的正压力增大,导致对器壁摩擦作用增强,最后造成锥体器壁的磨损穿孔。

基于注意力机制和CNN-GRU模型的脱硫系统pH值预测

针对火电厂石灰石-石膏烟气湿法脱硫系统中所面临的浆液pH值测量不准确、时间长的问题,提出了一种基于注意力机制和CNN-GRU模型来预测吸收塔内浆液pH值。首先,对火电厂监测系统(SIS)数据库中的数据进行预处理,然后使用相关性分析来确定它们之间的关联性。接下来可使用注意力机制(ATT)来自适应分配与pH值相关联的输入数据的权重,并根据权重大小来区分强弱特征变量,以此来解决预测精度低和不准确的问题。其后利用卷积神经网络(CNN)来二次提取和降维这些特征数据,并对送入门控循环神经单元网络(GRU)中的数据进行优化,可大大加快神经网络训练进程,并且能够更准确地处理复杂的动态脱硫变化。对某电厂2×350 MW机组运行数据进行测试,并通过与其他主流算法对比得出所建pH值预测模型具备更高的精确度和稳定性。最后结合模型预测控制(MPC),验证了该模型的实用性。

骨支架多孔结构设计及其流场特性研究

组织工程骨支架的结构及其内部流场的流体流动性能直接影响着营养物质的渗入和细胞的沉积。基于拓扑优化技术,以胫骨骨折实际受力为载荷设计不同孔隙率和尺度下的骨支架多孔结构单胞模型;运用计算流体动力学(CFD)方法对所得单胞及由其构建的多孔结构内部流场特性进行数值模拟,分析模型参数对各结构内部流场的流速分布和渗透率等的影响规律。结果表明各孔隙率和尺度下的单胞及多孔结构均具有良好的流场连通性,其中孔隙率是影响结构内流速的主要因素;各结构渗透率随着孔隙率和尺度的增大而增大;孔隙率和尺度较大的结构表现出更好的流体流动性能。研究成果可以为骨支架多孔结构的优化设计及应用提供支撑。

大单元视域下学习情境创设的教学策略——以“人体的体液调节”为例

从核心素养角度阐述“人体的体液调节”单元教学设计思路,围绕单元教学目标,从实验探究、案例分析、模型建构、实例分析等方面创设学习情境,培养学科核心素养。

基于ROMeo平台实时优化技术在重油催化裂化装置的应用

在整个炼油化工装置中,重油催化裂化装置(RFCC)占据核心地位。工业过程自动化和实时优化(RTO)技术是实现重油催化裂化装置经济效益最大化的有力措施。为此,介绍了基于严格在线实时优化解决方案(ROMeo)平台实时优化技术在重油催化裂化装置的建设思路,通过ROMeo实时优化系统和先进过程控制系统(APC)的实施,实时跟踪生产过程,持续不断进行在线优化,使装置在最佳操作点操作以达到最佳的经济效益。实时优化系统通过对生产原材料、最终产品和系统公用工程等的价格进行控制,并通过APC系统控制装置操作条件向RTO设定的目标靠近。应用结果表明,该系统有效实现了重油催化裂化装置产能增加且能耗较低,可使炼油企业增加经济效益。

钻井液冷却装置技术发展现状及展望

随着国内油气钻井向着万米深井开发,钻井过程中井底温度越来越高,因此需要对钻井液降温冷却以保护井下工具仪器。而国内钻井液冷却装置普遍存在设备超大、超高以及设备冷却降温幅度不大的现状。本文从介绍国外钻井液冷却装置技术现状出发,阐述了国外钻井液冷却装置技术现状;同时结合国内钻井工况,重点分析了国内自然冷却、开式冷却、闭式冷却和强制冷却4种钻井液冷却装置的工作原理、优缺点和适应范围。结合国内钻井技术发展现状,为保障冷却装置降温效果,结合道路运输和环保要求,分析了冷却装置降温机理研究、工程适应性、应用局限性和装置可靠性等关键技术难题,提出了冷却装置技术研发思路,为开发研制适应性强、可靠性高和冷却效果显著的装置提供参考。

天然气净化厂文丘里组合式急冷塔流场模拟与优化

康索夫尾气处理装置应用于天然气净化厂处理高温含硫烟气时,文丘里组合式急冷塔文丘里段(以下简称文丘里段)设备内部喷淋水线上方约30 cm处出现环状腐蚀环。针对设备腐蚀问题,利用计算流体力学软件模拟文丘里段气液流体流动及传热传质过程,研究腐蚀机理并提出优化方案。设备腐蚀原因是高温含硫烟气中的酸性组分被喷淋冷却时,与水蒸汽反应产生硫酸,当气体温度降至酸露点以下时产生高浓度硫酸,致使254SMo合金钢设备内壁发生严重酸腐蚀。文丘里段内部腐蚀无法完全解决,经模拟计算,改变喷淋雾化效果及喷嘴的喷淋夹角可大幅改变气液界面位置,改善设备腐蚀情况。研究成果可为类似文丘里组合式急冷塔在设计及运维方面提供参考。

基于粗糙集理论的联合站能效分析与评价

为降低联合站的综合能耗,采用粗糙集理论对影响联合站能效的指标进行离散化处理,并通过属性约简去除冗余信息,得到指标权重,将数据代入SVM模型实现综合能效值的预测。得到如下结论:单位液量综合能耗对联合站综合能效等级的影响最大;属性约简可以有效去除数据集中的冗余信息,起到了数据清洗和处理的作用;4号、5号、6号、10号和22号联合站的综合能效等级最高,用能效果较差。从优化站内工艺布局、提高设备负荷率、去除二段脱水负荷等方面降低联合站的能效等级,单月耗电量可减少1072 kWh,单月耗气量可减少472 m^(3),达到了节能减排、节能降耗的目的。

可调频超结构充液管道的振动抑制

提出了一种附加可调频局域共振单元的超结构充液管道,通过调整局域共振单元的质量块在弹簧片上的安装位置,实现局域共振单元固有频率的可调性,进而实现充液管道在多个频率下的振动抑制。首先建立了附加可调频局域共振单元的超结构充液管道的结构动力学模型,采用伽辽金法推导了超结构充液管道的运动方程,然后利用模态分析方法建立了多频带隙的解析表达式。建立了相应的有限元模型,对其多频减振特性进行数值仿真,并开展了相应的验证试验。计算和试验结果验证了所提出的超结构充液管道存在多个带隙,在带隙范围内充液管道的弯曲振动被显著抑制。研究工作表明,使用可调频局域共振单元能够有效抑制充液管道多个频率下的振动,为其在多目标频段下充液管道的减振应用提供参考。