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.

Design of Subharmonic Mixers above 100 GHz

This paper presents the design and simulation of several fixed-tuned sub-harmonic mixers cover frequencies from 110 GH to 130 GHz, 215 GH to 235 GHz, 310 GH to 350 GHz, and 400 GH to 440 GHz. Among them, 120 GHz, 225 GHz, 330 GHz subharmonic mixers are designed with flip-chipped planar schottky diode mounted onto a suspended quartz-based substrate, the 225 GHz and 425 GHz subharmonic mixers are GaAs membrane integrated, and the 115 GHz subharmonic mixer has been fabricated and tested already.

Characterization of mixing in an optimized designed T–T mixer with cylindrical elements

Passive micromixers are preferred over active mixers for many microfluidic applications due to their relative ease in integration into complex systems and operational flexibility.They also incur very low cost of manufacturing.However,the degree of mixing is comparatively low in passive mixers than active mixers due to the absence of disturbance in the flow by external forces and the inherent laminar nature of microchannel flows.Various designs of complex channel structures and three-dimensional geometries have been investigated in the past to obtain an efficient mixing in passive mixers.But the studies on mixing enhancement with simple planar geometries of passive mixers have been few and limited.The present work aims to investigate the possibility of mixing enhancement by employing simple planar type designs,such as T-mixer and T–T mixer with cylindrical elements placed in the mixing channel.The mixing performance has been evaluated in the Reynolds number range of 6 to700.Numerical results have shown that T–T mixer with cylindrical elements performed significantly well and obtained very good mixing quality over basic T-mixer for the entire range of Reynolds number(6 to 700).The device has also shown better mixing as compared to basic T–T mixer and T-mixer with cylindrical elements.A larger pair of vortices formed in the stagnation area due to the presence of a cylindrical element in the junction.Cylindrical elements downstream caused significant enhancement in mixing due to splitting and recombining action.The size of the cylindrical element in the T–T mixer has been optimized to obtain better mixing performance of the device.Remarkable improvement in mixing quality by T–T mixer with cylindrical elements has been obtained at the expense of small rise in pressure drop as compared to other passive designs considered in this study.Therefore,the current design of T–T mixer with cylindrical elements can act as an effective and simple passive mixing device for various micromixing applications.

An experimental study of immiscible liquid–liquid dispersions in a pump–mixer of mixer–settler

Drop size distribution(DSD) or mean droplet size(d32) and liquid holdup are two key parameters in a liquid–liquid extraction process. Understanding and accurately predicting those parameters are of great importance in the optimal design of extraction columns as well as mixer–settlers. In this paper, the method of built-in endoscopic probe combined with pulse laser was adopted to measure the droplet size in liquid–liquid dispersions with a pump-impeller in a rectangular mixer. The dispersion law of droplets with holdup range 1% to 24% in batch process and larger flow ratio range 1/5 to 5/1 in continuous process was studied. Under the batch operation condition, the DSD abided by log-normal distribution. With the increase of impeller speed or decrease of dispersed phase holdup, the d32 decreased. In addition, a prediction model of d32 of kerosene/deionized system was established as d32/D = 0.13(1 + 5.9φ)We-0.6. Under the continuous operation condition, the general model for droplet size prediction of kerosene/water system was presented as d32/D = C3(1 + C4φ)We-0.6. For the surfactant system and extraction system, the prediction models met a general model as d32/D = bφnWe-0.6.

CFD modeling of immiscible liquids turbulent dispersion in Kenics static mixers: Focusing on droplet behavior

The present study is concerned with the computational fluid dynamics(CFD)simulation of turbulent dispersion of immiscible liquids,namely,water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software.To study the droplet size distribution(DSD),the Eulerian formulation incorporating a population balance model(PBM)was employed.For the Eulerian–Lagrangian approach,a discrete phase model(DPM)in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution(RTD)of droplets.In both approaches,a shear stress transport(SST)k-ωturbulence model was used.For validation purposes,the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor,Sauter mean diameter and the mean residence time.The reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean diameter.In addition,the influence of important geometrical and operational parameters,including the number of mixing elements and Weber number,was studied.It was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.

Comparative analysis of different static mixers performance by CFD technique:An innovative mixer

The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160.The performance of the new mixer is compared with those of Kenics,SMX,and Komax static mixers.The pressure drop ratio(Z-factor),coefficient of variation(CoV),and extensional efficiency(α)features have been used to evaluate power consumption,distributive mixing,and dispersive mixing performances,respectively,in all mixers.The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation.CFD results are consistent with measured data and those obtained by available correlations in the literature.The new mixer shows a superior mixing performance compared to the other mixers.

The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes,high performance gas mixer is deeply needed for the injection of NH3 or O3.In this study,a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics(CFD).The results obtained using Particle Image Velocimetry(PIV)correlated well with the results obtained from simulation.The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer.Optimal process conditions and design were investigated.When L/D equaled 4,coefficient of variation(COV)was<5%.The inlet velocity did not affect the distributions of turbulent kinetic energy.In terms of both COV and pressure loss,the inner connector is important in the design of the static mixer.The nozzle length should be set at 4 cm.Taking both COV and pressure loss into consideration,the optimal oblique degree is 450.The averaged kinetic energy changed according to process conditions and design.The new static mixer resulted in improved mixing performance in a more compact design.The new static mixer is more energy efficient compared with other SV static mixers.Therefore,the double swirl static mixer is promising in gas mixing.

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently, Fischer-Tropsch synthesis （FTS） has become an interesting technology because of its potential role in producing biofuels via Biomass- to-Liquids （BTL） processes. In Fischer-Tropsch （FT） section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide （CO） and hydrogen （H2）, is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2 ： 1 molar ratio that was fed at the rate of 30 mL（STP）·min^- 1 （GHSV ≈ 136 mL·gcat^-1 ·h^-1） into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 ℃ and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions （in terms of time on stream） were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products （α） for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.

Numerical investigation of granular mixing in an intensive mixer:Effect of process and structural parameters on mixing performance and power consumption

Discrete element method(DEM)simulations of particle mixing process in an intensive mixer were conducted to study the influence of structural and process parameters on the mixing performance and power consumption.The DEM model was verified by comparing the impeller torque obtained from simulation with that from experiment.Impeller and vessel torque,coordination number(CN)and mixing index(Relative standard deviation)were adopted to qualify the particle dynamics and mixing performance with different parameters.A method based on cubic polynomial fitting was proposed to determine the critical mixing time and critical specific input work during the mixing process.It is found that the mixing performance and energy efficiency increases with the decrease of impeller offset.The mixing performance is improved slightly with the increase of blade number and the impeller with 3 blades has the highest energy efficiency due to its low input torque.Results indicate that the energy efficiency and the mixing performance increase with the decrease of filling level when the height of granular bed is higher than that of blade.

A Study on a Gas Agitated Extractor with Static Mixer

1 INTRODUCTIONMany chemical engineering operations involve the mass and heat transfer between two liquidphases in reactions.Mechanically agitated liquid-liquid extractor can be one of the examples forsuch operations.It has been well developed and used in the nuclear energy,petrochemical andother chemical industries.However,not much attention has been paid to the gas agitated liquid-

A Broadband 630-720 GHz Schottky Based Sub-Harmonic Mixer Using Intrinsic Resonances of Hammer-Head Filter

An room temperature low noise anti-parallel Schottky diode based 630-720 GHz sub-harmonic mixer(SHM) is designed, built and measured. Intrinsic resonances in lowpass hammer-head filter have been adopted to prevent the LO and RF power leak from the IF channel, while greatly minimizing the transmission line size. The mixer consists of 15 um quartz terahertz circuit and 127 um Al2 O3 IF transformer circuit. An improved lumped element equivalent noise model of SBDs guarantees the accuracy of simulation. The measurement indicates that with local oscillating(LO)signal of 2-8 mW, the lowest double sideband(DSB) conversion loss is 8.2 dB at 645 GHz,and the best DSB noise temperature is 2800 K at 657 GHz. The 3 dB bandwidth of conversion loss is 75 GHz from 638 to 715 GHz. The work IF frequency band is above 20 GHz ranging from 1 to 20 GHz with-10 dB return loss.

Recycle use of phosphorous mixer extractant to extract indium

The stripping and regeneration of the loaded organic phase of phosphorousmixer extractant (PPD) were studied. The mixed solutions (3 mol/L HCl +2 mol/L ZnC1_2) were used asthe stripping agent and more than 99 percent of indium can be stripped after three-stage strippingwhen the volume ratio of organic phase to stripping agent is 1:1. The organic phase can he recycledto use alter regeneration with HCl. The parallel contrast experiments with D_2EHPA (di-2-ethyl hexylphosphoric acid) were carried out under the same conditions. The results show that the mixerextractant has good reusability and the stripping and regeneration of PPD are superior to those ofD_2EHPA.

基于Mixer Layer的人脸表情识别

目前人脸表情识别研究多数采用卷积神经网络(CNN)提取人脸特征并分类,CNN的缺点是网络结构复杂,消耗计算资源.针对以上缺点,本文采用基于多层感知机(MLP)的Mixer Layer网络结构用于人脸表情识别.采用数据增强和迁移学习方法解决数据集样本不足的问题,搭建了不同层数的Mixer Layer网络.经过实验比较,4层Mixer Layer网络在CK+和JAFFE数据集上的识别准确率分别达到了98.71%和95.93%,8层Mixer Layer网络在Fer2013数据集上的识别准确率达到了63.06%.实验结果表明,无卷积结构的Mixer Layer网络在人脸表情识别任务上表现出良好的学习能力和泛化能力.

Effect of Rotation and Revolution on Performance of Blade-Free Planetary Mixer

In this study, flow structures and mixing performance in a blade-free planetary mixer, which combines rotation and revolution motions inside a cylindrical vessel, are numerically investigated. Flow fields in the mixer vessel are simulated in a single rotating reference frame with various revolution speeds and a fixed rotation speed. The mixing process is investigated by a Lagrangian particle tracking method and the mixing performance is evaluated based on particle concentration. The results of the numerical simulations show that a vortical flow with an axis inclined with respect to the rotation axis of the vessel is generated by the combined influence of the rotation and revolution motions. The flow structure and vortical flow intensity vary as a function of the precession rate, which is the ratio of the revolution speed to rotation speed. The mixing performance of the blade-free planetary mixer is found to be maximum at aspecific precession rate.

Phase-Locking of a Gunn Oscillator at 3mm Waveband Using High Temperature Superconducting Josephson Junction Harmonic Mixer

A Gunn oscillator at 3mm waveband has been phase-locked to a synthesizer local oscillator using a high T_(c)YBa_(2)Cu_(3)O_(7-δ) Josephson junction operated at 77K as the harmonic mixer,with harmonic numbers up to 52.The observed spectrum of the phase-locked output at the intermediate frequency(IF)shows clearly that the quality of the phase-locking is very good.To drive the analogue phase locking loop successfully,it is essential to have IF output and signal-to-noise ratio both as high as possible.