基于Hessian局部线性嵌入和MLP-Mixer的液体火箭发动机涡轮泵轻量化故障诊断框架

作为液体火箭发动机推进剂输送系统的关键部件,涡轮泵的运行状态直接影响着整个运载系统的性能,然而,现有的故障诊断方法往往面临特性参数选择片面及计算复杂度高等问题。针对上述局限,提出了面向涡轮泵的轻量化故障诊断框架。所提方法利用Hessian局部线性嵌入算法对信号时域、频域及时频特征进行降维,并引入一种轻量化的深度学习模型MLP-Mixer作为分类器,进而实现不同故障状态的辨识。采用某型号涡轮泵试车数据验证了所提方法的有效性,结果表明,该方法能够在保障诊断精度的同时有效降低计算复杂度,提高诊断效率。

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Terahertz high-sensitivity SIS mixer based on Nb–AlN–NbN hybrid superconducting tunnel junctions

The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.

Experimental and numerical investigations on micromixing performance of multi-orifice cross-flow jet mixers

Multi-orifice cross-flow jet mixers(MOCJMs)are used in various industrial applications due to their excellent mixing efficiency,but few studies have focused on the micromixing performance of MOCJMs.Herein,the flow characteristics and micromixing performance inside the MOCJM were investigated using experiments and computational fluid dynamics(CFD)simulations based on the Villermaux/Dushman system and the finite-rate/modified eddy-dissipation model.The optimal A value was correlated with the characteristic parameters of MOCJMs to develop a CFD calculation method applicable to the study of the micromixing performance of the MOCJMs.Then the micromixing efficiency was evaluated using the segregation index XS,and the effects of operational and geometric parameters such as mixing flow Reynolds number(ReM),flow ratio(RF),total jet area(ST),the number of jet orifices(n),and outlet configuration on the micromixing efficiency were investigated.It was found that the intensive turbulent region generated by interactions between jets,as well as between jets and crossflows,facilitated rapid reactions.XS decreased with increasing ReM and decreasing RF.Furthermore,MOCJMs with lower ST,four jet orifices,and the narrower outlet configuration demonstrated a better micromixing efficiency.This study contributes to a deeper understanding of the micromixing performance of MOCJMs and provides valuable guidance for their design,optimization,and industrial application.

CFD simulation of hydrodynamics and mixing performance in dual shaft eccentric mixers

This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric mixer.Fluid rheology was described by the power law rheological model.Computational fluid dynamics was employed to simulate the velocity field and shear rate inside the stirred tank.The influence mechanism of the rotational modes,height difference between impellers,impeller eccentricities,and impeller types on the flow field have been well investigated.We studied the performance of different dual-shaft eccentric mixers at the constant power input with its fluid velocity profiles,average shear strain rate,mixing time and mixing energy.The counter-rotation mode shows better mixing performance than co-rotation mode,and greater eccentricity can shorten mixing time on the basis of same stirred condition.To intensify the hydrodynamic interaction between impellers and enhance the overall mixing performance of the dual shaft eccentric mixers,it is critical to have a reasonable combination of impellers and an appropriate spatial position of impellers.

Computational and experimental investigations of a microfluidic mixer for efficient iodine extraction using carbon tetrachloride enhanced with gas bubbles

Numerous studies have been conducted on microfluidic mixers in various microanalysis systems, which elucidated the manipulation and control of small fluid volumes within microfluidic chips. These studies have demonstrated the ability to control fluids and samples precisely at the microscale. Microfluidic mixers provide high sensitivity for biochemical analysis due to their small volumes and high surface-to-volume ratios. A promising approach in drug delivery is the rapid microfluidic mixer-based extraction of elemental iodine at the micro level, demonstrating the versatility and the potential to enhance diagnostic imaging and accuracy in targeted drug delivery. Micro-mixing inside microfluidic chips plays a key role in biochemical analysis. The experimental study describes a microfluidic mixer for extraction of elemental iodine using carbon tetrachloride with a gas bubble mixing process. Gas bubbles are generated inside the microcavity to create turbulence and micro-vortices resulting in uniform mixing of samples. The bubble mixing of biochemical samples is analyzed at various pressure levels to validate the simulated results in computational fluid dynamics(CFD). The experimental setup includes a high-resolution camera and an air pump to observe the mixing process and volume at different pressure levels with time. The bubble formation is controlled by adjusting the inert gas flow inside the microfluidic chip. Microfluidic chip-based gas bubble mixing effects have been elaborated at various supplied pressures.

静态混合器结构优化设计与流场特性分析

为油田高能效驱油以提高原油产量,针对SK型和SX型静态混合器混合单元结构,通过创新设计和三维建模开发多重螺旋混合单元静态混合器,基于静态混合原理,利用FLUENT数值模拟软件,采用有限体积法,对所开发混合器内流体的流场进行仿真分析,研究该结构静态混合器的流动特性,结果表明,该种静态混合器使流体产生剪切和正反向涡旋作用,流体被充分扰动,混合均匀,满足油田注聚驱油要求,可为油田开发新型高效静态混合器提供一定技术支持。

从高钙富硼老卤中提硼研究

以青海某高钙富硼老卤为研究对象开展了提硼研究。结果表明,合适的萃取条件为:磺化煤油为稀释剂、异辛醇用量50%、萃取相比1.0、萃取混合时间15 min;合适的反萃条件为:反萃剂为pH=1的稀盐酸、反萃相比1.5、反萃混合时间15 min。以此条件在5级混合澄清槽中完成了连续逆流萃取—反萃运转试验,连续运转45 h,硼萃取率为95.49%,硼与钾、钠、钙、镁的分离效果较好;硼反萃率为99.59%,反萃液中硼含量达17.17 g/L。采用“溶剂萃取—反萃—高温蒸发—低温冷却结晶—重溶—冷却结晶—过滤洗涤—干燥”工艺高效分离提取硼,硼总回收率为92.33%,制备出的硼酸产品达国家标准(GB/T 538—2018)要求。

穿孔对穿孔型Kenics静态混合器混合性能的影响

为了提升传统Kenics静态混合器的混合效果,在传统螺旋插入带结构中引入穿孔结构,设计出穿孔型Kenics静态混合器。采用浓度变异系数评估穿孔内径(d)、穿孔间距(S)、混合单元长径比(Ar)对穿孔型静态混合器混合性能的影响。模拟结果表明,设置的穿孔结构会显著改变流体的流动状态,在穿孔处区域产生加速流动,进而提升混合器的混合性能;随着d的增加,流体之间的对流和交换作用逐渐增强,混合效果逐渐增强,但随着d的持续增加,导致混合器内部螺旋通道被破坏,混合效果反而减弱;仅改变S对混合效果没有明显影响;对于相同的混合器长度,Ar的减小导致混合元件数量增加,液体之间的扭转、剪切效果增强,混合器混合效果更好。

500m^(2)烧结机强化混匀技术研究与应用

针对实际生产中,当混合机填充率无法达到设计水平以及混合料中配加难制粒物料时而导致的混匀制粒效果不理想,烧结矿转鼓指数差的问题,本文在500 m^(2)烧结机工艺中配加20%FMG粉矿的条件下,结合弗鲁德准数计算,对烧结机混料系统工艺进行了研究。结果表明,当一次混合机的设计转速低于合理转速(6.94 r/min)时,烧结混料系统混匀制粒效果较差,通过采取将一次混合机加水比例由80%降低至75%并后延加水位置3 m的技术措施,增强了一次混合机混合料的混匀水平,使混合料制粒效果由39.12%提高至48.98%,解决了配加20%的FMG粉矿之后出现的烧结混合料黏结团聚、制粒效果差的问题,消除了烧结矿断面不均匀现象,最终使得烧结矿转鼓指数由76.14%提高至78.44%。

非牛顿流体在叶片式静态混合器中的传热强化特性

非牛顿流体在化学、食品和材料等领域具有关键作用,但高表观黏度使其通常具有低传热特性。叶片式静态混合器作为一种高效的传热强化设备,在化工过程强化中具有鲜明的技术特色。本文针对非牛顿流体在Kenics静态混合器(KSM)和Lightnin静态混合器(LSM)内的流动和传热特性进行了比较研究。重点分析了体积流量、元件长径比及流体浓度等参数对羧甲基纤维素(CMC)幂律流体的流动及传热影响。结果表明,在相同工况下,随着CMC溶液的体积流量增大,管道内的换热系数和压降均增大。静态混合元件的插入使得换热系数和压降显著提高且Lightnin元件产生的影响更明显。元件长径比和CMC溶液浓度影响流体在管道内的流动和换热。随着长径比的减小,传热性能得到提高,但其增大的阻力系数影响占据主导地位,综合换热性能系数(PEC)降低。溶液浓度的增大使得管道换热能力逐步削弱,并对管道内压降的提升有显著影响,综合换热性能降低。总结得出,在体积流量为4.5×10^(-4)m^(3)/s,质量分数为0.374%、长径比为3.0时,KSM的PEC最大为2.114。

Kenics型静态混合器中幂律流体与颗粒混合过程分析

针对Kenics型静态混合器内固体颗粒在幂律流体中的孤岛现象的产生机理进行研究。运用Fluent数值模拟固相颗粒与CMC水溶液在Kenics静态混合器中的混合过程,并利用浓度变异系数(COV)对颗粒分布特性进行量化分析。研究表明:提高流体表观黏度和流体入口速度,颗粒停留时间缩短,COV值降低,混合效果提高。在第4~8个扭旋叶片中间截面上均形成了两对对称的无粒子孤岛,降低流体表观黏度和提高流体入口速度,孤岛边界更清晰。扭旋叶片诱导的内流涡旋和近壁面涡旋有较高的涡量,涡旋中心局域形成无粒子孤岛,相邻叶片交错区域,随着涡旋耗散孤岛消失。

基于CFD-DEM算法的气力输送气固两相流特性分析

超轻粉体颗粒由于质量较小,在运输过程中易受气流扰动而飘散,物料的管道气力输送过程不稳定,易发生堵塞。为了研究超轻粉体颗粒在旋流气力输送中气固两相流流动特性,采用计算流体力学与离散单元法(CFD-DEM),对Komax型静态混合器内气固两相流动特性进行数值模拟研究。研究发现,带有Komax型元件的水平管道可以改变颗粒的流动情况,改善了水平管道内颗粒堆积和分布不均匀的现象;分别从颗粒相和流体相的流动状态分析得到元件长径比Ar=3时为最优几何结构;通过正交实验极差分析得到影响气固两相流动特性的因素顺序:输送气速>颗粒质量流量>颗粒粒径。当元件Ar=3时,颗粒-颗粒和颗粒-管壁的碰撞次数与碰撞强度呈现负相关,结合出口颗粒流分散状态,优选输送气速为3~4m/s;主要考虑输送气速对管内压降的影响,提出了带有Komax型元件的水平管道气力运输过程中压降与输送气速和轴向位置的经验拟合式。

声共振混合器高黏度流体混合的功耗特性研究

声共振混合利用机械共振产生高加速度振动,从而促进流体流动,其功耗特性对于其设计及应用具有重要作用。为研究声共振混合器的功耗特性,基于CFD建立了声共振混合过程仿真模型,分析了高黏度流体声共振混合过程壁面对物料的作用力和做功功率,探究了黏度和振动参数改变对混合器功耗特性的影响,并建立了声共振混合器混合功率的预测函数。研究结果表明,在混合过程中,壁面对液相做功的瞬时功率呈现先减少后稳定波动的趋势,而有效功率呈现先增加后稳定波动的趋势,这种不同的变化趋势是由于两者的相位差发生变化所导致的。增加振幅、频率或等加速度下低频大振幅都能够增加瞬时功率和有效功率,并减少液相进入稳定流动阶段所需吸收的外界能量。

育苗基质搅拌装置的设计与仿真分析

为提高育苗基质的搅拌效率,设计了一种新型育苗基质搅拌装置。确定了搅拌机的搅拌桶容量、搅拌器形状、附属装置及电机型号,利用EDEM颗粒有限元分析软件对比人工搅拌和搅拌机搅拌的搅拌效果。结果表明:搅拌机搅拌育苗基质的均匀程度更高,效果更好,搅拌时长到3 s时,搅拌机内的颗粒已经明显分散。

基于Creo Parametric软件对密炼机啮合型转子的冷却结构优化分析

采用Creo Parametric软件建立密炼机啮合型转子的热分析模型,对转子的冷却结构进行优化分析。结果表明:“分体式+螺旋管道”冷却结构对转子有很好的冷却效果,分体式冷却结构可使转子的主体及凸棱冷却更均匀,螺旋管道冷却结构可以增大冷却水流面积和流速,冷却效果较好;与单螺旋冷却结构转子相比,双螺旋冷却结构转子的凸棱壁厚度和温度场分布更均匀,凸棱顶部最高温度较低。

薄板式静态混合器混合性能数值模拟

薄板式静态混合器内构件简单、通量高、压降低,可以有效降低稀释水掺混能耗。文中以不均匀系数ψ和管路压降Δp作为评价指标,利用CFD(计算流体动力学),对比分析单直管、单顺流羽状管、单逆流羽状管和双顺流羽状管等4种注水方式的混合效果和压降。研究发现,在注水管安装在L/D=5.3处,单管注入时,注水两侧形成的径向二次流强度Se变化缓慢,稳定的涡旋流在混合器内产生混合“死区”,降低了静态混合器的油水混合速度;当ψ降至0.05时,混合距离超过18D。此混合死区解释了单管注入时分散相注入点附近易出现局部高浓度区。双顺流羽状管注入时,对撞水相产生较高径向二次流强度Se,且迅速降低。快速变化的流场显著减少混合距离,与单管注入相比,ψ降至0.05时混合距离减少76.9%,Δp增加1.5%。

基于高速ADC的数字双混频时差测量系统

使用双混频时差法进行时间和频率测量时,模拟部分引入的噪声会干扰信号过零点的判断,降低测量精度,而使用数字信号处理技术后不再需要判断过零点,量化噪声成为系统内的主要噪声来源,可以通过数字滤波器对其进行抑制。同时有利于设计结构紧凑的系统,更易于小型化,测量速度也可以进行灵活配置。通过引入高速模数转换器、数控振荡器、低通抽取滤波器、数字鉴相器等,设计了数字双混频时差测量系统,并研制了4通道的原理样机。测试结果表明,当频率源为10 MHz的信号时,原理样机中属于同片ADC(analog-to-digital converter)的两个通道间的本底噪声约为5×10^(-14)@1 s,属于不同片ADC的两个通道间的本底噪声约为8×10^(-14)@1 s,满足原子振荡器的测量要求。并以主动型氢钟VCH-1003M为参考,使用原理样机分别对Microchip的5071A铯原子钟和SRS的FS725铷原子钟的稳定度进行测量,测量结果与Microchip的相噪分析仪53100A和5120A无显著差异。

基于Compactlogix5000的大型串联密炼机控制系统的设计

大型串联式密炼机具有节约厂房及设备投资、降低炼胶段数、减少用工数量,降低能源损耗、提高炼胶品质等优点。本文介绍了串联密炼机的基本结构组成、炼胶特点、基于罗克韦尔PLC使用智能网关实现高压变频器通讯控制的电气控制系统设计。

基于电流模结构的超宽带无源混频器设计

采用SMIC 55 nm CMOS工艺,提出基于电流模结构的2~8 GHz超宽带高线性度直接下变频无源混频器结构.本设计主要结构为低噪声跨导放大器(low noise transconductance amplifier,LNTA)驱动I/Q两路电流模无源混频器,负载为低输入阻抗的跨阻放大器(trans-impedance amplifier,TIA),即LNTA-Passive Mixer-TIA结构.LNTA采用电容交叉耦合以及双端正反馈结构,解决阻抗匹配以及噪声等关键参数的折中问题.整个接收机链路获得较好的线性度及噪声性能,对于电源电压以及衬底噪声的鲁棒性也有所提升.后仿结果表明,在电源电压1.2 V情况下,射频输入信号频率为2~8 GHz,1 dB压缩点为−5.5 dBm,带内输入三阶交调点为−1 dBm,整体噪声系数为4 dB,核心版图面积为0.12 mm^(2).