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离心叶轮失速涡结构演化与耦合特征研究

推进技术 2024年第4期45卷 91-99页

作者：钟云红刘正先李孝检赵明天津大学机械工程学院天津300350

为深入解析离心压气机旋转失速的涡流耦合演化机理,基于Eckardt离心叶轮全通道非定常数值模拟数据,利用涡系识别法和傅里叶频谱分析等方法研究了失速工况下叶轮中关键涡流结构的空间分布特征及非定常演化规律,发现失速流场同时存在两类... 详细信息

为深入解析离心压气机旋转失速的涡流耦合演化机理,基于Eckardt离心叶轮全通道非定常数值模拟数据,利用涡系识别法和傅里叶频谱分析等方法研究了失速工况下叶轮中关键涡流结构的空间分布特征及非定常演化规律,发现失速流场同时存在两类涡流结构:叶片前缘龙卷风涡和叶顶泄漏涡,两类流动结构交替演化、相互作用,形成了以63%叶轮转速周向传播的失速团,促使离心叶轮失速。具体体现为:叶顶泄漏涡形成并发展,裹挟、牵引叶片前缘分离涡从叶顶开始剥离,直至完全从叶片吸力面脱落。脱落后的分离涡沿周向运动,受到叶片阻挡产生溢流,该溢流流体在叶片压力面与吸力面横向压差的作用下演变为龙卷风涡,该龙卷风涡在周向运动过程中被叶片“截断”为两段而后向下游扩散并逐渐耗散消失。之后新的叶顶泄漏涡又逐渐兴起,形成下一个涡流演化周期。两种涡结构此消彼长、周而复始,共同构成了失速演化特征。

关键词：离心叶轮旋转失速龙卷风涡结构叶顶泄漏涡耦合演化

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国家建构视野下爱国主义教育的时代挑战与实践逻辑

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教育学报 2024年第1期20卷 44-55页

作者：刘争先杨岚西南大学教育学部/学校德育研究中心重庆400715 四川外国语大学国际教育学院重庆400031

在个体化时代,爱国主义的工具论和信念论等错误观念的影响日增,使爱国主义教育面临诸多挑战。基于国家建构理论,论证国家既是工具性存在,也是目的性存在,正面给出爱国主义教育的基础性理由,阐明国家实施爱国主义教育的正当性基础,进而... 详细信息

在个体化时代,爱国主义的工具论和信念论等错误观念的影响日增,使爱国主义教育面临诸多挑战。基于国家建构理论,论证国家既是工具性存在,也是目的性存在,正面给出爱国主义教育的基础性理由,阐明国家实施爱国主义教育的正当性基础,进而澄清个体自主性的限度,分析爱国主义工具论和信念论观念之谬误。对于爱国主义教育的实施而言,爱国主义教育既需要向国民证明,国家作为工具性存在,有效地实现了其使命;也需要让国民认可,国家作为目的性存在,具有支配的正当性。对于爱国主义教育的评价而言,学校既需要考虑爱国主义教育实施的效果,也需要审视爱国主义教育实施本身的正当性。

关键词：国家建构国家能力正当性自主性有效性爱国主义教育

An extended unresolved CFD-DEM coupling method for simulation of fluid and non-spherical particles

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Particuology 2022年第9期20卷 1-12页

作者： Liping He zhengxian liu Yongzhi Zhao Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin 300350China Institute of Process Equipment College of Energy EngineeringZhejiang UniversityHangzhou 310027China

This study develops an extended unresolved CFD-DEM coupling method for simulation of the fluid-solid flow with non-spherical *** limitation of fluid grid size is discussed,by simulating the settling of a cylinder in a Newtonian fluid based on the resolved and unresolved CFD-DEM coupling ***,the calculation of porosity and the fluid-particle relative velocity based on the particle shape enlarge-ment method for simulation of non-spherical particles is *** availability of the particle shape enlargement method for the simulation of non-spherical particles with different sphericity is discussed in this work,by comparing it with the results from the equivalent diameter enlargement *** lim-itation of the equivalent diameter enlargement method for non-spherical particles is revealed from the simulation *** typical cases are employed to elaborate and verify the extended unresolved CFD-DEM method based on particle shape enlargement method,by presenting a good consistency with the experimental *** proves that the extended unresolved CFD-DEM method is suitable for differ-ent CFD grid size ratios,and consolidates that it is a universal calculation method for CFD-DEM coupling simulation.

关键词： CFD-DEM Unresolved method Fluid-solid flow Non-spherical particle Rod

Influences of Leading-Edge Tubercle Amplitude on Airfoil Flow Field

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Journal of Thermal Science 2023年第4期32卷 1335-1344页

作者： ZHAO Ming WEI Tong ZHAO Yijia liu zhengxian Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin300350China Tianjin Key Laboratory of Modern Engineering Mechanics Tianjin UniversityTianjin300350China

The influences of leading-edge tubercle amplitude on airfoil flow field have been analyzed at high angle of *** accuracy of a large eddy simulation(LES)research is validated through quantitative comparisons with corresponding experimental ***,a proper orthogonal decomposition(POD)analysis has been carried out based on the unsteady flow field and the fluid mechanisms of corresponding POD modes have been ***,the influences of leading-edge tubercle amplitude have been *** the streamwise vorticity is larger than that of small amplitude cases,the momentum transfer process at peaks is more obvious for large amplitude,leading to delayed flow *** amplitude and wavelength play important roles in the generation of laminar separation bubble(LSB)at ***,the Karman vortex shedding process takes place at specific trough sections as pairs of periodic spatial structures exist in the dominant POD *** destruction of Karman vortex shedding process is strengthened along with the increase of amplitude.

关键词： leading-edge tubercle airfoil flow field proper orthogonal decomposition

Mechanical properties and shape memory behavior of 4D printed functionally graded cellular structures

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Science China(Technological Sciences) 2023年第12期66卷 3522-3533页

作者： ZENG ChengJun liu LiWu ZHAO Wei liu zhengxian XIN XiaoZhou liu YanJu LENG JinSong Department of Astronautical Science and Mechanics Harbin Institute of TechnologyHarbin 150001China Center for Composite Materials and Structures Harbin Institute of TechnologyHarbin 150080China

The properties of functionally graded(FG) cellular structures vary spatially, and the varying properties can meet the requirements of different working environments. In this study, we fabricated FG cellular structures with shape memory effect by 4D printing and evaluated the compressive performance and shape memory behavior of these structures with temperature through experimental analysis and finite element simulations. The results show that the maximum energy absorption gradually decreases but the compressive modulus gradually increases with increasing gradient parameters. Moreover, the finite element simulations also show that the compressive deformation mode of the structure shifts from uniform to non-uniform deformation with increasing gradient parameters. The compressive modulus and compressive strength of 4D printed FG structures decrease with increasing temperature due to the influence of the shape memory polymer, and they exhibit outstanding shape recovery capability under high-temperature stimulus. The proposed 4D printed FG structures with such responsiveness to stimulus shed light on the design of intelligent energy-absorbing devices that meet specific functional requirements.

关键词： functionally graded structures 4D printing shape memory polymers energy absorption cellular structures

On the nature of tip clearance flow in subsonic centrifugal impellers

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Science China(Technological Sciences) 2013年第9期56卷 2170-2177页

作者： liu zhengxian PING Yan ZANGENEH Mehrdad School of Mechanical Engineering Tianjin University State Key Laboratory of Engines Tianjin University Department of Mechanical Engineering University College London

Increasing demand for downsizing of engines to improve CO2 emissions has resulted in renewed efforts to improve the efficiency and expend the stable operating range of the centrifugal compressors used in petro-chemical equipment and turbochargers. The losses in these compressors are dominated by tip clearance flow. In this paper, the tip clearance flow in the subsonic impeller is numerically investigated. The nature of the tip clearance in inducer, axial to radial bend and exducer are studied in detail at design and off-design conditions by examining the detailed flow field through the clearance and the interaction of the clearance flow with the shear effect with the endwalls. The correlation between blade loading and span wise geometry and clearance flow at different locations are presented.

关键词：叶尖间隙流离心叶轮性质亚音速二氧化碳排放量离心压缩机非设计条件石油化工设备

Exact Bayesian and Fiducial Limits for the Mean of Lognormal Distribution

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Journal of Systems Engineering and Electronics 1994年第2期5卷 41-46页

作者： Zhou, Yuanquan Weng, Zhaoxi liu, zhengxian Beijing Inst of Structure and Environment Beijing China

In this paper, the exact Bayesian limits, taking conjugate and noninformative prior distribution, and the exact fiducial limits for the mean of the lognormal distribution are presented. They can be found iteratively by one-dimension integral on a finite interval. The new algorithm is very convenient and with high accuracy. It can meet the practical engineering need excellently. However, the primitive algorithm is rather cumbersome. By the way, the very close approximate limits with a simple algorithm are derived. They can be applied immediately to engineering. Otherwise, they can also be used as a search interval to find the root of equation for the exact limits.

关键词： Algorithms Approximation theory Engineering research Failure analysis Integral equations Integration Iterative methods Materials testing Reliability theory Service life Statistical tests

Dynamic Coupling Correlation of Gas Film in Dry Gas Seal with Spiral Groove

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Chinese Journal of Mechanical Engineering 2014年第4期27卷 853-859页

作者： liu zhengxian WANG Musu ZHOU Yue WU Ningning School of Mechanical Engineering Tianjin University State Key Laboratory of Engines Tianjin University

In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.

关键词： dry gas seal spiral groove gas film dynamic data fitting method coupling function

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基于IPDG方法的嵌套网格技术

航空动力学报 2022年第6期37卷 1206-1216页

作者：赵博赵明刘伟李孝检刘正先天津大学机械工程学院力学系天津300350 电子科技大学计算机科学与工程学院成都611731

在内罚间断伽辽金(IPDG)方法框架内应用嵌套网格技术求解了二维可压缩Navier-Stokes方程。通过把黏性通量作为辅助变量实现了Navier-Stokes方程的降阶,继而用间断有限元方法进行离散得到空间半离散方程。时间推进采用Newton-Krylov隐式... 详细信息

在内罚间断伽辽金(IPDG)方法框架内应用嵌套网格技术求解了二维可压缩Navier-Stokes方程。通过把黏性通量作为辅助变量实现了Navier-Stokes方程的降阶,继而用间断有限元方法进行离散得到空间半离散方程。时间推进采用Newton-Krylov隐式方法。利用库埃特流动精确解验证了该方法的精度。在此基础上,对包括有黏NACA0012翼型绕流、定常和非定常的圆柱绕流在内的若干典型测试算例开展数值模拟,进一步验证了该方法的鲁棒性和可靠性。在嵌套网格中应用了h型网格自适应技术用于提高激波分辨率,对NACA0012翼型无黏跨声速绕流开展数值模拟,结果表明:自适应之后的单元数相比无自适应时只增加了8.4%,但是激波分辨率得到了显著提高,激波附近的计算结果也与实验值符合得更好,从而验证了该方法的有效性。

关键词：二维可压缩Navier-Stokes方程嵌套网格间断伽辽金方法内罚方法 h型网格自适应技术