检索结果-内蒙古大学图书馆

27th Congress of the International Federation for Heat Treatment and Surface engineering, IFHTSE 2022 and European Conference on Heat Treatment 2022, ECHT 2022

作者： Narayan, Nithin Mohan Landgraf, Pierre Lampke, Thomas Fritsching, Udo Bremen Germany University of Bremen Department of Particles and Process Engineering Bremen Germany Chemnitz Germany

ISBN: (纸本)9783200085848

Heat treatment of steels intends to attain pre-determined material properties. After austenitisation in vacuum, gas quenching is a widely preferred heat treatment process, since in contrast to quenching by fluids, it is cleaner and more environment friendly process. In addition, gas quenching does not suffer from the Leidenfrost effect, so that uniform cooling can be attained. However, challenges reside with the selection of suitable heat treatment parameters which are highly depending on different criteria such as sample geometry, material composition, batch properties etc. The current study focusses to develop an autonomous prediction tool based on ANN (Artificial Neural Network) to determine optimum heat treatment parameter. The ANN is trained with the experimental and simulation results to predict the proper heat treatment parameters in order to achieve a homogeneous quenching process under consideration of the component geometry and material as well as energy efficiency. To accomplish this target, the heat treatment and flow traits during gas based cooling as well as the development of the treated material microstructure and hardness are investigated. The HTC (heat transfer coefficient) and quenching curve at several sample spatial locations within the sample volume are measured by means of contactprobe on the probe surface and thermoelements. The investigation of the flow characteristic is accomplished in gas quenching setup by means of CTA (Constant temperature anemometry) system and Pitot tube. Furthermore, a CFD-Simulation model is developed and validated with the experimental results to numerically investigate the influence of quenching parameters. © 2022 Quaker Houghton. All right reserved.

关键词： Hardness

来源：评论

学校读者我要写书评

暂无评论

Numerical investigation of capillary driven droplet breakup due to fluid dynamic instabilities 15

Numerical investigation of capillary driven droplet breakup ...

引用

15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Giefer, Patrick Fritsching, Udo Leibniz Institute for Materials Engineering-IWT Particles and Process Engineering Bremen28359 Germany University of Bremen Particles and Process Engineering Bremen28359 Germany

The membrane emulsification process obtains the advantage to formulate liquid/liquid systems in a low shear stress process. Whereas the emulsification process and the influence of the membrane structure and geometry on the final product are well investigated, the liquid deformation and liquid dispersion process inside the membrane structure are quite unknown. In the present study, the droplet breakup mechanism in the vicinity of a solid wall is numerically investigated with OpenFoam using the Volume of Fluid Method. Different wetting conditions on the membrane wall have been implemented. The results show a relation between wetting properties and fluid dynamic disturbances’ resp. instabilities that may grow to larger instabilities, resulting in droplet breakup inside the membrane. These results can be used to find the sweet spot of capillary driven droplet breakup with minimum shear force to handle shear sensitive media while keeping a defined mono disperse emulsion. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Membranes

来源：评论

学校读者我要写书评

暂无评论

Modelling polydisperse nanoparticle production in an enclosed flame spray pyrolysis reactor 15

Modelling polydisperse nanoparticle production in an enclose...

引用

15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Neto, Pedro Bianchi Buss, Lizoel Fritsching, Udo Noriler, Dirceu Department of Process Engineering - DEPro University of Campinas Brazil Leibniz Institute for Materials Engineering - IWT Bremen Germany Department of Particles and Process Engineering University of Bremen Germany

In recent years, the scientific interest in population balance models (PBM) is increasing in many research fields, from environmental studies to material production. This technique allows for a precise prediction of population characteristics and behaviour and is a precious ally in process development. Combining PBM and computational fluid dynamics (CFD) has proved very helpful for designing and improving new equipment. That also applies to the production of nanoparticles via the flame spray pyrolysis (FSP) process. The use of reactors with enclosed flames, which allows the fine control of the oxidant in the flame reaction zone, for instance, could benefit from better numerical models for nanomaterial development prediction. In this work, a previously developed model was adapted for the enclosed reactor configuration. In the model, an Eulerian framework is applied to characterize the continuous gas phase, while a Lagrangian framework represents the discrete droplets of the burning spray. A bivariate PBM describes the solid phase, and its polydisperse solution was achieved using the direct quadrature method of moments (DQMoM). Numerical results are validated through comparison with experimental data available in the literature regarding nanoparticle size, presenting good agreement. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Computational fluid dynamics

来源：评论

学校读者我要写书评

暂无评论

Investigating the performance of an airblast pressure swirl atomizer 15

Investigating the performance of an airblast pressure swirl ...

引用

15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Kamenov, Dilyan Achelis, Lydia Uhlenwinkel, Volker Fritsching, Udo Particles and Process Engineering University of Bremen Bremen Germany Leibniz Institute for Materials Engineering IWT Bremen Germany

The current contribution investigates the atomization of a liquid with the help of a novel atomizer design. The pressure gas atomizer (PGA) consists of a combination of a pressure swirl nozzle and a concentric gas nozzle that offers advantages compared to conventional techniques when liquids with complex rheological properties, i.e. metal melts, need to be atomized. As the liquid phase exits the pressure swirl nozzle it is being spread out as a concentric film in the form of a hollow cone with a film thickness of a few hundred micrometres, depending on the liquid outlet diameter. This film already may disintegrate on its own due to instabilities, forming large ligaments or droplets. An annular gas nozzle, mounted underneath the pressure swirl nozzle, induces secondary atomization of the liquid film resp. ligaments by impinging a gas stream on the liquid phase. To be able to draw conclusions on the advantages of the new atomizer design, a conventional close coupled atomizer, which is widely used for atomizing metal melts, has been investigated in comparison. The geometrical parameters varied for both atomizers are the outlet diameter and the number of tangential inlets of the pressure swirl nozzle. The drop size distribution and the sauter mean diameter have been measured within the atomization of a model liquid (tap water) at identical gas and liquid mass flow rates in both atomizers by means of a laser diffraction spectrometer. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Atomization

来源：评论

学校读者我要写书评

暂无评论

Dynamic flowsheet simulation of re-entrainment from particle layers formed inside electrostatic precipitators

引用

Particuology 2020年第6期18卷 41-47页

作者： Soren Sander Udo Fritsching Particles and Process Engineering University of BremenBibliothekstrasse 128359 BremenGermany Process Engineering Leibniz-lnstitutfiir Werkstofforientierte Technologien-IWTBadgasteiner Strasse 328359 BremenGermany

Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial *** studies of particle separation in the size range of several 100 nm to 25μm is of particular interest for the prediction of precipitation efficiencies and *** typically cover the transport of particles towards walls of the ***,no model yet covers the possible re-entrainment of particles from layers formed at the walls back into the gas *** study presents the implementation of a new time-resolving model for electrostatic precipitation utilizing a re-entrainment *** data support the results of *** model uses a statistical approach based on properties of the particulate layer forming at the precipitator *** model is used for the analysis of the redispersion of particles in a laboratory-scale electrostatic precipitator(Sander,Gawor,&Fritsching,2018).Results show reduced precipitation efficiencies for particles larger than 5μm as particles have higher kinetic impact energies and lower bounding energy at the layer *** dynamics reveal a steady-state behavior of the separation for CaCO3(limestone,trademark"Ulmer WeissR")while Al2O3(trademark"Pural NFR")precipitation is affected by layer buildup at the walls increasing over several minutes.

关键词： Electrostatic precipitator Flow sheet model Redispersion and re-entrainment Gas cleaning Particle layer

来源：评论

学校读者我要写书评

暂无评论

Effect of Y-Jet Nozzle Geometry and Operating Conditions on Spray Characteristics and Atomizer Efficiency

SSRN

引用

SSRN 2023年

作者： Barbieri, Matheus Rover Achelis, Lydia Fritsching, Udo Particles and Process Engineering Department Faculty of Production Engineering University Bremen Bibliothekstr. 1 Bremen28359 Germany Leibniz Institute for Materials Engineering IWT Badgasteiner Str. 3 Bremen28359 Germany

The investigation and optimization of the atomizer nozzle design are paramount for an efficient atomization performance. Motivated by internal mixing atomizers used in FCC-reactors in the oil industry, the present work aims to improve the gas-liquid mixing process promoted by a specific design of the Y-jet nozzle by investigating the impact of key geometric parameters. The performance assessment is conducted by investigating the internal mixing chamber pressure, high-speed images of the spray, and the analysis of droplet size and velocity spatial distributions. The investigation considers industrially representative operating conditions as opposed to the lower mass flow rates typically employed in lab-scale investigations. The geometry variation considers the length and opening angle of the internal mixing chamber, as well as the impingement angle between the gas and the liquid jets inside the atomizer nozzle. A particular geometric characteristic of the utilized nozzles is the mixing-chamber conical geometry, distinguishing them from conventional cylindrical geometries. The impact of the nozzle geometry and operation parameters on atomization efficiency and spray homogeneity are the main outcomes of this approach. Overall, nozzles with shorter mixing chambers promote more efficient atomization combined with small droplet sizes and a more homogeneous spray. © 2023, The Authors. All rights reserved.

关键词： Atomization

来源：评论

学校读者我要写书评

暂无评论

Acoustic Signatures of Single Disrupting FSP Droplets in a Heated Oxygen Atmosphere

SSRN

引用

SSRN 2024年

作者： Witte, Arne Tse, Stephen D. Mädler, Lutz Particles and Process Engineering Faculty of Production Engineering University of Bremen Badgasteiner Str. 1 Bremen28359 Germany Department of Mechanical and Aerospace Engineering Rutgers University – New Brunswick PiscatawayNJ08854 United States Leibniz Institute for Materials Engineering IWT Badgasteiner Str. 3 Bremen28359 Germany

Droplet disruptions such as puffing (weak disruptions) and µ-explosions (strong disruptions) play an important role in the synthesis of nanoparticles via flame spray pyrolysis (FSP), as they increase the mass transport of the liquid precursor-solvent system into the gas phase, thus contributing to the formation of homogeneous nanoparticles. Therefore, the targeted experimental study of droplet breakup using single droplet experiments is an essential step in gaining fundamental knowledge about time- and concentration-dependent mechanisms of these disruptions. Here, we study the disruptive combustion of single droplets containing a commonly applied Tin-based precursor with initial Sn molar concentrations ranging from 0.05 mol/L to 1 mol/L. High-speed imaging techniques have been combined with high sample-rate acoustic measurements to detect, distinguish, and quantify droplet disruption phenomena. It has been demonstrated that precursor concentrations up to 0.25 mol/L are more prone to µ-explosions, whereas higher Sn molar concentrations show puffing. The boundary between these disruption modes is identified acoustically by quantifying the strength of a disruption using a calculated disruption strength index. Droplet size and the associated liquid mass, which has to be moved by a growing bubble inside the droplet, are suggested to play a central role in causing the different droplet breakup characteristics. Puffing is detected at the instant of disruption for droplet sizes above 55 µm, whereas µ-explosions occur for smaller droplets. High-speed measurements reveal size-dependent effects on the disruption mode for the same precursor concentration. © 2024, The Authors. All rights reserved.

关键词： Explosions

来源：评论

学校读者我要写书评

暂无评论

Tailoring Crystal Structure and Morphology of Mnox Nanoparticles Via Electrospray-Assisted Flame Spray Pyrolysis

SSRN

引用

SSRN 2023年

作者： Mohammadi, Shahram Poostforooshan, Jalal Stodt, Malte F.B. Olszok, Vinzent Kiefer, Johannes Fritsching, Udo Weber, Alfred P. Institute of Particle Technology Clausthal University of Technology Clausthal-Zellerfeld Germany Technische Thermodynamik Universität Bremen Bremen Germany Leibniz Institute for Materials Engineering IWT Bremen Germany Particles and Process Engineering University Bremen Bremen Germany

In this work, MnOx nanoparticles were produced by a continuous electrospray-assisted flame spray pyrolysis (EAFSP) method. In this regard, the precursor solutions containing manganese (II) nitrate hydrate (MnN) dissolved in 1-propanol precursor solutions are initially atomized into charged droplets by electrospray in the microdripping mode. Then, the electrically charged precursor droplets enter the flame in a controlled manner without requiring a dispersion gas. The synthesis was carried out with varying horizontal injection locations from different heights above the burner (HAB) to control the high-temperature residence times of the charged droplets without changing the flame conditions for producing MnOx nanoparticles with tunable particle properties. Various diagnostics such as TEM, SMPS, BET, and XRD were applied for analyzing the formation of primary and agglomerate MnOx nanoparticles as well as their crystal phases with varying temperature histories. Furthermore, phase-Doppler anemometry (PDA) experiments have been conducted to track the evolution of droplet size and droplet axial velocity in the electrospray flame, allowing for the study of combustion of electrosprayed MnN droplets and the presence of µ-explosions in the flame. © 2023, The Authors. All rights reserved.

关键词： Morphology

来源：评论

学校读者我要写书评

暂无评论

Temperature distribution in open and enclosed flame spray reactor 14

Temperature distribution in open and enclosed flame spray re...

引用

14th International Conference on Liquid Atomization and Spray Systems, ICLASS 2018

作者： Buss, L. Bianchi Neto, P. Meier, H.F. Noriler, D. Fritsching, U. Leibniz Institute for Materials Engineering IWT Process and Chemical Engineering Division Bremen Germany Department of Chemical Engineering DEQ University of Blumenau Brazil Department of Process Engineering DEPro University of Campinas Brazil Department of Particles and Process Engineering University of Bremen Germany

Spray synthesis processes involving combustion reactions can be found in several industrial applications. By flame spray pyrolysis (FSP), nanoparticles from metals and metal oxides can be synthesized. In the present work, numerical investigations are performed, in order to understand the influence of geometrical setups (open and enclosed reactor) at different operating conditions on the flame temperature and spray behavior as well as on the temperature and temperature residence time distribution of the gas and the particles. From the open reactor results, the natural mass flow of gas entrainment into the flame is estimated. By supplying an appropriate co-flow rate as "artificial entrainment" in the enclosed reactor setup results in a quite similar flame behavior as found for the open reactor. By reducing the co-flow gas, strong recirculation zones are observed in the reactor, and the temperature increases considerably, resulting in larger nanoparticle sizes. © 2018 Solar Turbines Incorporated.

关键词： Metal nanoparticles

来源：评论

学校读者我要写书评

暂无评论

Image Analysis of the Atomization process in a Molten Metal Close-Coupled Atomizer for Different Gas Pressures and Temperatures 15

Image Analysis of the Atomization Process in a Molten Metal ...

引用

15th Triennial International Conference on Liquid Atomization and Spray Systems, ICLASS 2021

作者： Zerwas, Alexander Ariyoshi Avila, Kerstin de Paiva, José Luís Guardani, Roberto Achelis, Lydia Fritsching, Udo Chemical Engineering Department University of São Paulo São Paulo Brazil Leibniz Institute for Materials Engineering IWT Badgasteiner Straße 3 Bremen28359 Germany University of Bremen Faculty of Production Engineering Particles and Process Engineering Badgasteiner Straße 1 Bremen28359 Germany

Sprays of molten metal are known to exhibit rich spatio-temporal dynamics, such as a pulsating metal mass flux, or a precession motion of the melt plume. Powerful tools for their investigation are high-speed recordings combined with digital image processing. In this work, we present a method to generate spatio-temporal diagrams from the recordings. These diagrams are ideally suited to quantify spray fluctuations in space and time. Experiments were conducted in an annular close-coupled atomizer using a copper alloy (CuSn6) as base material with varying atomization gas pressures ([0.8, 1.2, 1.6, 2.0] MPa) and temperatures ([293, 423, 523] K). The region of the primary atomization was monitored with a high-speed camera recording 21,800 frames per second. At the parameters investigated we observe an oscillation of the spray boundaries below 100 Hz indicating a slow precession motion. The analysis of the statistically steady spray shape surprisingly reveals a breakdown of the axial symmetry at large gas pressures, whose origin is currently unknown. © 2021 ICLASS 2021 - 15th Triennial International Conference on Liquid Atomization and Spray Systems. All Rights Reserved.

关键词： Powder metals

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：