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.

Optimal Design and Experimental Study of Tightly Coupled SCR Mixers for Diesel Engines

Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.

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.

Fuzzy Comprehensive Analysis of Static Mixers Used for Selective Catalytic Reduction in Diesel Engines

The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.

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.

Pico–nano bubble column flotation using static mixer-venturi tube for Pittsburgh No.8 coal seam

The flotation process is a particle-hydrophobic surface-based separation technique. To improve the essential flotation steps of collision and attachment probabilities, and reduce the step of detachment probabilities between air bubbles and hydrophobic particles, a selectively designed cavitation venturi tube combined with a static mixer can be used to generate very high numbers of pico and nano bubbles in a flotation column. Fully embraced by those high numbers of tiny bubbles, hydrophobic particles readily attract the tiny bubbles to their surfaces. The results of column flotation of Pittsburgh No. 8 seam coal are obtained in a 5.08 cm ID and 162 cm height flotation column equipped with a static mixer and cavitation venturi tube, using kerosene as collector and MIBC as frother. Design of the experimental procedure is combined with a statistical two-stepwise analysis to determine the optimal operating conditions for maximum recovery at a specified grade. The effect of independent variables on the responses has been explained. Combustible material recovery of 85–90% at clean coal product of 10–11% ash is obtained from feed of 29.6% ash, with a much-reduced amount of frother and collector than that used in conventional column flotation. The column flotation process utilizing pico and nano bubbles can also be extended to the lower limit and upper limit of particle size ranges, minus 75 lm and 300–600 lm, respectively, for better recovery.

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.

Experimental Analysis of the Flow Characteristics of an Adjustable Critical-Flow Venturi Nozzle

The response of an adjustable critical-flow Venturi nozzle is investigated through a set indoor experiments aimed to determine the related critical flow rate,critical pressure ratio,and discharge coefficient.The effect of a variation in the cone displacement and liquid content on the critical flow characteristics is examined in detail and it is shown that the former can be used to effectively adjust the critical flow rate.The critical pressure ratio of the considered nozzle is above 0.85,and the critical flow control deviation of the gas flow is within±3%.Liquid flow can reduce the gas critical mass flow rate accordingly,especially for the cases with larger liquid volume and lower inlet pressure.The set of results and conclusions provided are intended to support the optimization of steam injection techniques in the context of heavy oil recovery processes.

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。

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。

大直径偏心型文丘里施肥器优化设计与试验

为改善现有大直径文丘里施肥器的吸肥性能,对其进行结构优化设计.基于大直径对称型文丘里施肥器(M型),对其改造设计为偏心型文丘里施肥器(P型).采用正交设计方法,应用数值模拟技术,以吸肥效率为评价指标确定P型文丘里施肥器最优结构参数组合,并对2种施肥器进行试验测试和数值模拟对比分析.结果表明最优结构参数组合为喉管进口直径17 mm、扩散角3°、喉管出口直径20 mm、喉管凹槽宽度4 mm、喉管直线段长度16.6 mm、喉管凹槽直径27 mm、收缩角23.5°.通过试验测试对比分析,经结构优化后的P型施肥器较M型施肥器的最大吸肥流量提高了21.4%;在进口压力为0.25 MPa时,最大吸肥浓度提升了约30.7%,最大吸肥效率提升了约13.9%.流场分析表明,相较于M型施肥器,在相同的压差条件下,P型施肥器更不容易产生空化,并且P型文丘里施肥器流态更加稳定,能量损失更小.可见优化后的偏心型文丘里施肥器能提高吸肥性能.

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。

搅拌混合设备结构及应用研究

搅拌混合机是一种常见机械设备,文章主要进行混合机设备结构及应用技术的探索。文章研究对象为双螺旋锥形混合机、卧式螺带混合机、犁刀式混料机、桨叶式混合机、无重力混合机五种结构的搅拌混合机,主要针对设备性能、工作原理、结构配置、设备特点等方面进行研究。

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%。

结构参数对气液下喷式喷射器性能的影响研究

喷射环流反应器是一种新型的气液或气液固接触反应装置,其中的喷射器结构会对反应器性能产生重要影响。文章采用计算流体力学方法,建立了文丘里型喷射器的数学模型,分析了吸气室、喉部和扩散段等结构对喷射器吸气量的影响规律。模拟结果表明:吸气室直径和气相入口方式对吸气量影响不大;喷嘴与喉部之间距离越小,喉部长度越短,吸气量越高;扩散段扩散角度在2~4°之间时吸气量存在最大值。

基于全型面补偿的叶片弯曲回弹控制研究

为了研究高强度钢板在弯曲成形后的回弹变形,以某搅拌机叶片为研究对象,采用全型面迭代补偿法对叶片弯曲回弹进行数值模拟与实验研究。首先利用CAE软件对叶片弯曲成形进行数值模拟,并得到其型面关键点的回弹量;然后通过弯曲实验测其型面上对应关键点的实际回弹量;再将模拟回弹量与实测回弹量进行对比,来验证数值模拟的可靠性;最后将模拟回弹量对叶片模具型面先后进行两次全型面迭代补偿,最终将其弯曲后的回弹量控制在所允许的公差范围内。研究结果表明:模拟结果与试验结果在型面关键点的回弹量基本一致,全型面迭代补偿法能有效地控制制件的最终回弹量。

新型内藏式文丘里管空化发生器空化特性

为解决工业实际应用中串联文丘里管只有单级发挥作用,而并联文丘里管空间占用大且空化性能不佳的问题。提出了一种新型内藏式文丘里管,并采用数值模拟的方法针对该结构的空化特性进行研究,研究了入口压力、内部小型文丘里管入口角度、出口角度、喉径与管径比、喉径与喉长比等参数对其空化性能的影响,研究结果表明:随着入口压力的升高,管内空化发生面积逐渐增大,当压力达到0.7 MPa时,文丘里管内的空化性能达到最大;通过对内部小型文丘里管的不同结构参数研究确定,当入口角度为40°,出口角度为18°,喉径与管径比为0.6,喉径与喉长比为2时,新型内藏式文丘里管的空化性能达到最大。该研究可为新型内藏式文丘里管设计及其应用提供一定参考。