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3D Two-way Coupled TEHD Analysis on the Lubricating Characteristics of Thrust Bearings in Pump-turbine Units by Combining CFD and FEA

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Chinese Journal of Mechanical Engineering 2016年第1期29卷 112-123页

作者： zhai liming LUO Yongyao WANG Zhengwei LIU Xin State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China Department of Thermal Engineering Tsinghua University Beijing 100084 China

The thermal elastic hydro dynamic （TEHD） lubrication analysis for the thrust bearing is usually conducted by combining Reynolds equation with finite element analysis （FEA）. But it is still a problem to conduct the computation by combining computational fluid dynamics （CFD） and FEA which can simulate the TEHD more accurately. In this paper, by using both direct and separate coupled solutions together, steady TEHD lubrication considering the viscosity-temperature effect for a bidirectional thrust bearing in a pump-turbine unit is simulated combining a 3D CFD model for the oil film with a 3D FEA model for the pad and mirror plate. Cyclic symmetry condition is used in the oil film flow as more reasonable boundary conditions which avoids the oil temperature assumption at the leading and trailing edge. Deformations of the pad and mirror plate are predicted and discussed as well as the distributions of oil film thickness, pressure, temperature. The predicted temperature shows good agreement with measurements, while the pressure shows a reasonable distribution comparing with previous studies. Further analysis of the three-coupled-field reveals the reason of the high pressure and high temperature generated in the film. Finally, the influence of rotational speed of the mirror plate on the lubrication characteristics is illustrated which shows the thrust load should be balanced against the oil film temperature and pressure in optimized designs. This research proposes a thrust bearing computation method by combining CFD and FEA which can do the TEHD analysis more accurately.

关键词： pump-turbine thrust bearing TEHD lubrication two-way coupled CFD FEA

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Nonlinear Vibration Induced by the Water-film Whirl and Whip in a Sliding Bearing Rotor System

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Chinese Journal of Mechanical Engineering 2016年第2期29卷 260-270页

作者： zhai liming LUO Yongyao WANG Zhengwei KITAUCHI Seishiro MIYAGAWA Kazuyoshi State Key Laboratory of Hydroscience and Engineering Tsinghua University Department of Thermal Engineering Tsinghua University Department of Applied Mechanics and Aerospace Engineering Waseda University

Many industrial applications and experiments have shown that sliding bearings often experience fluid film whip due to nonlinear fluid film forces which can cause rotor-stator rub-impact failures. The oil-film whips have attracted many studies while the water-film whips in the water lubricated sliding bearing have been little researched with the mechanism still an open problem. The dynamic fluid film forces in a water sliding bearing are investigated numerically with rotational, whirling and squeezing motions of the journal using a nonlinear model to identify the relationships between the three motions. Rotor speed-up and slow-down experiments are then conducted with the rotor system supported by a water lubricated sliding bearing to induce the water-film whirl/whip and verify the relationship. The experimental results show that the vibrations of the journal alternated between increasing and decreasing rather than continuously increasing as the rotational speed increased to twice the first critical speed, which can be explained well by the nonlinear model. The radial growth rate of the whirl motion greatly affects the whirl frequency of the journal and is responsible for the frequency lock in the water-film whip. Further analysis shows that increasing the lubricating water flow rate changes the water-film whirl/whip characteristics, reduces the first critical speed, advances the time when significant water-film whirling motion occurs, and also increases the vibration amplitude at the bearing center which may lead to the rotor-stator rub-impact. The study gives the insight into the water-film whirl and whip in the water lubricated sliding bearing.

关键词： rotor system sliding bearing vibration water-film whip nonlinear

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考虑流固耦合影响的柴油机油底壳模态及振动响应数值分析

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应用科技 2024年第3期51卷 60-64页

作者：倪龑翟黎明韩旭东梁福祥李志强一汽解放动力总成事业部动力总成产品开发部江苏无锡214026

油底壳是发动机的典型薄壁件,工作时不断承受动态载荷激励,其模态振型和振动响应对整机的可靠性和噪声、振动与声振粗糙度(noise vibration harshness,NVH)有着重要影响。本文以某柴油机拼接焊油底壳为对象,对其湿模态及振动响应进行了... 详细信息

油底壳是发动机的典型薄壁件,工作时不断承受动态载荷激励,其模态振型和振动响应对整机的可靠性和噪声、振动与声振粗糙度(noise vibration harshness,NVH)有着重要影响。本文以某柴油机拼接焊油底壳为对象,对其湿模态及振动响应进行了数值分析。首先,采用有限元法进行了自由状态下的干模态分析,并实测验证了数值模型的精度。然后,采用流固耦合的方法计算了湿状态油底壳模态,分析了实际工作时润滑油对结构特性的影响。最后,基于实测的螺栓振动进行了油底壳强迫振动响应分析计算,并通过振动测试验证了计算的准确性。测试结果表明,上述数值分析方法可以预测油底壳的工作状态下的振动特性,指导发动机的可靠性和NVH优化设计。

关键词：柴油机油底壳流固耦合模态分析强迫振动有限元干模态湿模态

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Effect of trigger system on experimental dispersion characteristics of active surface wave testing

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 311-318页

作者： Lin Shibin Jeramy C.Ashlock Zhu liming Qin Zexiang Li Bo Zhu Xingji zhai Changhai State Key Laboratory of Precision Blasting Jianghan UniversityWuhan 430056China Hubei Key Laboratory of Blasting Engineering Jianghan UniversityWuhan 430056China Department of Civil Construction&Environmental EngineeringIowa State UniversityAmesIA 50010USA Wuhan Airport Road Development Co. Ltd.Wuhan 430065China School of Civil and Environmental Engineering Harbin Institute of TechnologyShenzhen 518055China Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education Harbin Institute of TechnologyHarbin 150090China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disaster of the Ministry of Industry and Information Technology Harbin Institute of TechnologyHarbin 150090China

A trigger system is typically employed in active seismic testing to trigger and synchronize multichannel surface wave data acquisition.The effect of the trigger system on the dispersion image of surface waves is empirically known to be negligible,however,theoretical explanation regarding the effect of the trigger system is insufficient.This study systematically examines the theory for surface wave dispersion analysis and proves that the effect of the trigger system on a dispersion image is negligible via a solid theoretical explanation.Subsequently,based on the new theoretical explanation,an alternative method that uses only the relative phase difference between sensors to extract dispersion characteristics with better conceptual clarity is proposed.Two active surface wave testing cases are considered to validate the theory and method.The results indicate that(1)an accurate trigger system is not necessary for surface wave data acquisition,and(2)it is unnecessary to assume that the impact point is the generation point of the surface waves for the experimental dispersion analysis.

关键词： site investigation surface waves data acquisition dispersion

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Fast Carrier Selection of JPEG Steganography Appropriate for Application

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Tsinghua Science and Technology 2020年第5期25卷 614-624页

作者： Weixiang Ren Yibo Xu liming zhai Lina Wang Ju Jia the Key Laboratory of Aerospace Information Security and Trusted Computing Ministry of EducationWuhan UniversityWuhan 430000China the School of Cyber Science and Engineering Wuhan UniversityWuhan 430000China Micropattern Co.Ltd. Wuhan 430000China

In recent years,the improvement of the security of steganography mainly involves not only carrier security but also distortion function.In the actual environment,the existing method of carrier selection is limited by its complex algorithm and slow running speed,making it not appropriate for rapid communication.This study proposes a method for selecting carriers and improving the security of steganography.JPEG images are decompressed to spatial domain.Then correlation coefficients between two adjacent pixels in the horizontal,vertical,counter diagonal,and major diagonal directions are calculated.The mean value of the four correlation coefficients is used to evaluate the security of each JPEG image.The images with low correlation coefficients are considered safe carriers and used for embedding in our scheme.The experimental results indicate that the stego images generated from the selected carriers exhibit a higher anti-steganalysis capability than those generated from the randomly selected carriers.Under the premise of the same security level,the images with low correlation coefficients have a high capacity.Our algorithm has a very fast running speed,and the running time of a 2048×2048 image is less than 1 s.

关键词： steganography steganalysis carrier JPEG correlation coefficients

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The selective deposition of Fe species inside ZSM-5 for the oxidation of cyclohexane to cyclohexanone

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Science China Chemistry 2021年第7期64卷 1088-1095页

作者： liming zhai Bin Zhang Haojie Liang Huibin Wu Xinchun Yang Gen Luo Shichao Zhao Yong Qin State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SciencesTaiyuan 030001China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.

关键词： atomic layer deposition selective oxidation of cyclohexane iron oxide FeO_(x)/ZSM-5 Fe–O–Si species

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Impact Analysis of the Aging Silicone Oil in the Damper on the Torsional Vibration of the Crankshaft of the Heavy-duty Vehicle Diesel Engine

Impact Analysis of the Aging Silicone Oil in the Damper on t...

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2019中国汽车工程学会年会

作者： zhai liming Wang Enzhen Xu Weiguo Huang Chenghai Yang Zhenguo Engine Business Division of FAW Jiefang Automotive Co. Ltd. School of Vehicle and Mobility of Tsinghua University

The silicone-oil damper of the diesel engine has significant effects on reducing the torsional vibration and the torsional stress of the crankshaft.The nature to maintain viscosity of the silicone oilis an important indicator when we evaluate the reliability of a silicone-oil damper.With a heavy-dutyvehicle diesel engine which meets China 6 emission standards as an object of research,this paper used AVL EXCITE to establish thetorsional numerical model of the crankshaft which considers coupling effect of the non-linear stiffness and the damping of the silicon-oil damper,and discussed the impacts of the silicon oil in different viscosities on the amplitude of the torsional vibration and the dynamical tangential stress.The numerical results were also compared with the measurements in the dynamical durability test in which applying the time variable.The results indicate the measurements in which the diesel engine run 953 hours turn out to be close to the simulation and demonstrate the accuracy of thedynamical numerical model.If the viscosity of the silicone oil reduces not more than 40%,its impacts on the torsional vibration and the torsional stress of the crankshaft are limited.However,with the viscosity increasing to 70%,the 6 th-order vibration amplitude approach to the requirement limit,so that should be taken into consideration.Objectively speaking,the changes of the silicone oil viscosity will not have great impacts on the damper under normal use.For optimal performance,there should be the enhanced durability to the silicone oil in the damper and should take some effective measures to avoid the overquickdecrease of the silicone oilviscosity.

关键词： diesel engine torsional vibration silicone-oil damper silicone-oil deterioration simulation

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面向深度伪造的溯源取证方法

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清华大学学报（自然科学版） 2022年第5期62卷 959-964页

作者：王丽娜聂建思汪润翟黎明武汉大学空天信息安全与可信计算教育部重点实验室武汉430072

近年来,生成对抗网络(GAN)的迅速发展使得合成图像越来越逼真,对个人和社会造成了极大的威胁。现有的研究致力于被动地鉴别伪造产品,但在真实应用场景下通常面临通用性不足和鲁棒性差等两大难题。因此,该文提出了一种面向深度伪造的溯... 详细信息

近年来,生成对抗网络(GAN)的迅速发展使得合成图像越来越逼真,对个人和社会造成了极大的威胁。现有的研究致力于被动地鉴别伪造产品,但在真实应用场景下通常面临通用性不足和鲁棒性差等两大难题。因此,该文提出了一种面向深度伪造的溯源取证方法,将秘密信息隐藏到图像中以追踪伪造图像的源头。设计了一个端到端的深度神经网络,该网络由嵌入网络、 GAN模拟器和恢复网络等3部分组成。其中,嵌入网络和恢复网络分别用于实现秘密信息的嵌入和提取,GAN模拟器用于模拟各种GAN的图像变换。实验中在已知GAN的篡改下恢复图像的平均归一化互相关(NCC)系数高于0.9,在未知GAN的篡改下平均NCC也能达到0.8左右,具有很好的鲁棒性和通用性。此外,该方法中嵌入的秘密信息具有较好的隐蔽性,平均峰值信噪比(PSNR)在30 dB左右。

关键词：图像合成与篡改深度伪造溯源取证

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考虑确定性表面形貌的O形圈密封性能分析

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西安交通大学学报 2022年第12期56卷 46-55页

作者：和建森翟黎明饶聪黄毅杰郭飞中国民航大学航空工程学院天津300300 清华大学摩擦学国家重点实验室北京100084 一汽解放汽车有限公司发动机事业部江苏无锡214000

为测量O形密封圈应用在负压油介质环境中的密封泄漏率,构建了一套求解O形密封圈泄漏率的数值仿真算法,并辅以实验进行验证。利用真实表面形貌进行分区处理用于匹配接触压力分布,进而利用接触状态矩阵生成泄漏通道来模拟真实泄漏状况,通... 详细信息

为测量O形密封圈应用在负压油介质环境中的密封泄漏率,构建了一套求解O形密封圈泄漏率的数值仿真算法,并辅以实验进行验证。利用真实表面形貌进行分区处理用于匹配接触压力分布,进而利用接触状态矩阵生成泄漏通道来模拟真实泄漏状况,通过观察泄漏通道的有无来判定密封是否泄漏,同时对平行平板泄漏模型进行改进使其适用于不同通道截面形状的泄漏率计算。对不同油压下的O形圈密封泄漏率进行计算,结果表明:当流体介质压力为0.07 MPa时,仿真所得密封泄漏率为1.717×10^(-12)m^(3)/s;当介质压力增大至0.09 MPa时,仿真所得密封泄漏率下降为1.525×10^(-12)m^(3)/s。比较不同介质压力下的接触应力分布,结果表明:随流体介质压力增加,密封接触区域接触应力分布增大,形成贯穿密封接触区域的泄漏通道范围减小,泄漏率减小。为验证仿真结果的合理性,将仿真结果与实验结果进行对比,结果表明:两者相对误差在10%左右,实验结果与仿真结果相符程度较好。

关键词： O形圈泄漏率确定性模型端面密封

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Distance Effect of Ni-Pt Dual Sites for Active Hydrogen Transfer in Tandem Reaction

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The Innovation 2020年第2期1卷 29-35,28页

作者： Huibin Wu Bin Zhang Haojie Liang liming zhai Guofu Wang Yong Qin State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SciencesTaiyuan 030001PR China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Unveiling the distance effect between different sites in multifunctional catalysts remains a major challenge.Herein,we investigate the distance effect by constructing a dual-site distance-controlled tandem catalyst with a five-layered TiO2/Pt/TiO2/Ni/TiO2 tubular nanostructure by template-assisted atomic layer deposition.In this catalyst,the Ni and Pt sites are separated by a porous TiO2 interlayer,and the distance between them can be precisely controlled on the subnanometer scale by altering the thickness of the interlayer,while the inner and outer porous TiO2 layers are designed for structural stability.The catalyst exhibits superior performance for the tandem hydrazine hydrate decomposition to hydrogen and subsequent nitrobenzene hydrogenation when the Ni and Pt site distance is on the subnanometer level.The performance increases with the decrease of the distance and is better than the catalyst without the TiO2 interlayer.Isotopic and kinetic experiments reveal that the distance effect controls the transfer of active hydrogen,which is the rate-determining step of the tandem reaction in a water solvent.Reduced Ti species with oxygen vacancies on the TiO2 interlayer provide the active sites for hydrogen transfer with-Ti-OH surface intermediates via the continuous chemisorption/desorption of water.A smaller distance induces the generation of more active sites for hydrogen transfer and thus higher efficiency in the synergy of Ni and Pt sites.Our work provides new insight for the distance effect of different active sites and the mechanism of intermediate transfer in tandem reactions.

关键词： DISTANCE EFFECT DUAL SITES HYDROGEN TRANSFER INTERLAYER TANDEM CATALYST

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