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Numerical investigation of radial inflow in the impeller rear cavity with and without baffle

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Science China(Technological Sciences) 2016年第3期59卷 456-467页

作者： LIU Guang du qiang LIU Jun WANG Pei ZHU Junqiang Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

In typical small engines, the cooling air for high pressure turbine(HPT) in a gas turbine engine is commonly bled off from the main flow at the tip of the centrifugal impeller. The pressurized air flow is drawn radially inwards through the impeller rear cavity. The centripetal air flow creates a strong vortex because of high inlet tangential velocity, which results in significant pressure losses. This not only restricts the mass flow rate, but also reduces the cooling air pressure for down-stream hot components. The present study is devoted to the numerical modeling of flow in an impeller rear cavity. The simulations are carried out with axisymmetric and 3-D sector models for various inlet swirl ratio β_0(0–0.6), turbulent flow parameter lT(0.028–0.280) with and without baffle. The baffle is a thin plate attached to the stationary wall of the cavity, and is proved to be useful in reducing the pressure loss of centripetal flow in the impeller rear cavity in the current paper. Further flow details in impeller rear cavity with and without baffle are displayed using CFD techniques. The CFD results show that for any specified geometry, the outlet pressure coefficient of impeller rear cavity with or without baffle depends only on the inlet swirl ratio and turbulent flow parameter. Meanwhile, the outlet pressure coefficient of the cavity with baffle is indeed smaller than that of cavity without baffle, especially for the cases with high inlet swirl ratio. The suppression of the effect of centrifugal pumping and the mixing beween the main air which is downstream of the baffle and the recirculating flow of the vortex in the stationary cavity, which are caused by the use of baffle, are the underlying reasons that lead to the reduction of outlet pressure loss.

关键词：离心叶轮径向流挡板数值研究计算流体力学技术燃气涡轮发动机压力系数冷却空气

Transverse relaxation characteristic and stress relaxation model considering molecular chains of HTPB coating based on pre-strained thermal aging

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Defence Technology（防务技术） 2021年第3期17卷 821-828页

作者： Yong-qiang du Jian Zheng Gui-bo Yu Jian-zhuang Zhi Shijiazhuang Campus Army Engineering UniversityShijiazhuang050003China Intelligent Manufacturing Institute Hebei College of Industry and TechnologyShijiazhuang050003China

In order to accurately describe the transverse relaxation characteristic and stress relaxation modulus of HTPB coating during pre-strain thermal aging process,a one month thermal aging test was carried out at70C with pre-strain of 0%,3%,6%and 9%,*** low-field1 H NMR and stress relaxation modulus tests were carried out for HTPB coating at different aging *** stress relaxation model considering the molecular chains was proposed according to the changes of crosslinking chain and dangling chain of HTPB coating during pre-strain *** results showed that with the increase of aging time,the decay rate of transverse relaxation curve became faster,the transverse relaxation time decreased,the value of combined parameter q Mrl increased,the proportion of crosslinking chain decreased,while the proportion of dangling chain ***,the stress relaxation modulus increased,the crosslinking network structure of HTPB coating became denser and the degree of crosslinking *** the initial aging stage,the pre-strain will destroy the crosslinking network structure of HTPB coating to a certain *** the increase of aging time,the effect of pre-strain will gradually weaken and the influence of aging on materials will gradually *** correlations between the stress relaxation model considering the molecular chains and the test results were more than 0.9950,which can accurately describe the stress relaxation modulus of HTPB coating during the pre-strain thermal aging process.

关键词： HTPB Pre-strain aging Transverse relaxation characteristic Molecular chain Stress relaxation model

MXene-derived quantum dots based photocatalysts:Synthesis,application,prospects,and challenges

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Chinese Chemical Letters 2024年第6期35卷 123-133页

作者： Hao Deng Yuxin Hui Chao Zhang Qi Zhou qiang Li Hao du Derek Hao Guoxiang Yang Qi Wang School of Environmental Science and Engineering Zhejiang Gongshang UniversityHangzhou 310018China Instrumental Analysis Center of Zhejiang Gongshang University Hangzhou 310018China Centre for Technology in Water and Wastewater(CTWW) School of Civil and Environmental EngineeringUniversity of Technology Sydney(UTS)UltimoNSW 2007Australia

In recent years,the emerging two-dimensional material-MXenes has attracted widespread attention in the field of photocatalysis due to its high conductivity,suitable Fermi level,tunable elemental composition,and excellent photoelectric *** zero-dimensional quantum dots(MQDs)derived from 2D MXenes not only inherit the characteristics of MXenes but also exhibit better performance due to the quantum size *** on the above excellent physical and chemical properties,MQDs are often used as co-catalysts of photocatalysts,and show excellent co-catalytic *** the same time,compared with other cocatalysts(precious metals,metal oxides,metal sulfides),it has the advantages of low cost and high ***,understanding the status of MQDs in the field of photocatalysis is crucial for their further *** this review,we summarized the synthesis and modification methods of MQDs in recent years,as well as their photocatalytic applications in H_(2) production,CO_(2) reduction,N_(2) fixation,pollutant degradation,and other *** addition,the challenges and prospects faced by MQDs are also proposed,providing theoretical guidance for the further development of MQD-based photocatalysts.

关键词： MXenes Quantum dots Photocatalysis Composites Environment purification

Simultaneous Prediction of Morphologies of a Critical Nucleus and an Equilibrium Precipitate in Solids

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Communications in Computational Physics 2010年第4期7卷 674-682页

作者： Lei Zhang Long-Qing Chen qiang du Department of Mathematics Penn State UniversityPA 16802USA Department of Materials Science and Engineering Penn State UniversityPA 16802USA

We investigate the critical nucleus and equilibrium morphologies duringprecipitation of a second-phase particle in a solid. We show that a combination ofdiffuse-interface description and a constrained string method is able to predict boththe critical nucleus and equilibrium precipitate morphologies simultaneously without a priori assumptions. Using the cubic to cubic transformation as an example, it isdemonstrated that the maximum composition within a critical nucleus can be eitherhigher or lower than that of equilibrium precipitate while the morphology of an equilibrium precipitate may exhibit lower symmetry than the critical nucleus resulted fromelastic interactions.

关键词： Phase field diffuse interface nucleation critical nucleus constrained string method elasticity

Fabrication and Testing of Carbon Fiber Reinforced Truss Core Sandwich Panels

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Journal of Materials Science & Technology 2009年第4期25卷 547-550页

作者： Bing Wang Linzhi Wu Li Ma qiang Wang Shanyi du Center for Composite Materials Harbin Institute of Technology Harbin 150001 China

Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores. The top and bottom facesheets were interconnected with truss cores. Both ends of the truss cores were embedded into four layers of top and bottom facesheets. The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels. Experimental results indicated that the mechanical behavior of sandwich structure under in-plane loading is dominated by the buckling and debonding of facesheets.

关键词： Sandwich panel Truss core Carbon fiber

Numerical Analysis of PRISM-PY Calculations for Hard-and Soft-Core Generic Polymer Models

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Chinese Journal of Polymer Science 2024年第4期42卷 532-543页

作者： qiang Wang Department of Chemical and Biological Engineering Colorado State University1370 Campus DeliveryFort CollinsCO80523-1370USA

Generic polymer models capturing the chain connectivity and excluded-volume interactions between polymer segments can be classified, according to whether or not the 3D integral of the latter diverges, into hard- and soft-core models. Taking homogeneous systems of compressible homopolymer melts (or equivalently homopolymer solutions in an implicit, good solvent) in the continuum as an example, we recently compared the correlation effects on the structural and thermodynamic properties of the hard- and soft-core models given by the polymer reference interaction site model (PRISM) theory with the Percus-Yevick (PY) closure (Polymers 2023, 15, 1180). Here we analyzed in detail the numerical errors and behavior of the interchain pair correlation functions (PCFs) given by the PRISM-PY calculations of these models using an efficient numerical approach that we proposed. Our numerical approach has the least number of independent variables to be iteratively solved, analytically treats the discontinuities caused by the non-bonded pair potential (such as that of the hard spheres) and takes only the inverse Fourier transform of the interchain indirect PCF between polymer segments (which is continuous and decays towards 0 with increasing wavenumber much faster than both the interchain direct and total PCFs), and is essential for us to accurately solve the PRISM-PY theory for chain length N as large as 106. To capture the correlation-hole effect, the real-space cut-off in the PRISM calculations should be proportional to the square root of N.

关键词： Generic polymer models Soft potentials Polymer reference interaction site model theory

A Discontinuous Galerkin Method with Penalty for One-Dimensional Nonlocal Diffusion Problems

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Communications on Applied Mathematics and Computation 2020年第1期2卷 31-55页

作者： qiang du Lili Ju Jianfang Lu Xiaochuan Tian Department of Applied Physics and Applied Mathematics Columbia UniversityNew YorkNY 10027USA Department of Mathematics University of South CarolinaColumbiaSC 29208USA South China Research Center for Applied Mathematics and Interdisciplinary Studies South China Normal UniversityGuangzhou 510631China Department of Mathematics University of Texas at AustinAustinTX 78712USA

There have been many theoretical studies and numerical investigations of nonlocal diffusion(ND)problems in recent *** this paper,we propose and analyze a new discontinuous Galerkin method for solving one-dimensional steady-state and time-dependent ND problems,based on a formulation that directly penalizes the jumps across the element interfaces in the nonlocal *** show that the proposed discontinuous Galerkin scheme is stable and ***,the local limit of such DG scheme recovers classical DG scheme for the corresponding local diff usion problem,which is a distinct feature of the new formulation and assures the asymptotic compatibility of the *** tests are also presented to demonstrate the eff ectiveness and the robustness of the proposed method.

关键词： Nonlocal diff usion Discontinuous Galerkin method Interior penalty Asymptotic compatibility Strong stability preserving

Single-port laparoscopy-assisted vaginal repair of a cesarean scar defect: a single-center retrospective study

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Chinese Medical Journal 2020年第3期133卷 285-291页

作者： Yong-Li Zhang Guo-Cheng Wang Jun-Jie Qu Gui-qiang du Wei-qiang Zhou Department of Obstetrics and Gynecology Shanghai First Maternity and Infant HospitalTongji University School of MedicineShanghai 201204China.

Background:The incidence of uterine cesarean scar defect(niche)is high,and some patients require ***-port laparoscopy can reduce post-operative pain,and provide better cosmetic *** study was performed to evaluate the safety and superiority of single-port laparoscopy-assisted vaginal repair of uterine cesarean scar defect(niche)in women after cesarean ***:This study included 74 patients who were diagnosed with uterine cesarean niche at the Shanghai First Maternity and Infant Hospital from January 2013 to June ***-seven patients underwent single-port laparoscopy-assisted vaginal surgery as the case group,and the remaining patients underwent vaginal repair surgery as the control *** collected data from the inpatient and follow-up medical *** clinical characteristics of these two groups were *** odds ratios and 95%confidential intervals were calculated for each variable by univariate and multivariate ***:Patients who underwent single-port laparoscopy-assisted vaginal repair had a significantly longer operation time(2.3[2.0-2.7]vs.2.0[1.6-2.3]h,P=0.015),shorter gas passage time(1.2[1.0-1.5]vs.1.7[1.0-2.0]days,P=0.012),shorter hospital stay(3.1[3.0-4.0]vs.4.5[4.0-6.0]days,P=0.019),and fewer complications(0 vs.4 cases).Univariate analysis showed that depth of the niche(P=0.021)the mild adhesiolysis score(P=0.035)and moderate adhesiolysis score(P=0.013)were associated with the bladder *** analysis showed that the moderate adhesiolysis score(P=0.029;95%confidence interval,1.318-3.526)was the strongest independent predictor of bladder ***:This study confirmed the safety and superiority of single-port laparoscopy-assisted vaginal repair of uterine cesarean scars.

关键词： Single-port laparoscopy Uterine cesarean scar defect(niche) Adhesion

Influence of Secondary Sealing Flow on Performance of Turbine Axial Rim Seals

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Journal of Thermal Science 2020年第3期29卷 840-851页

作者： WANG Ruonan du qiang LIU Guang LIAN Zengyan XIE Lei ZHU Junqiang Key Lab of Light-duty Gas-turbine Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

Purge flow is of great importance in cooling turbine disks and sealing rotor-stator disc cavity to reduce hot gas ingestion in gas *** amount of cooling air extracted from the compressor is crucial to engine *** sealing air will cause not only a reduction in work transfer but also an increase in aerodynamic losses caused by the mixing of main and sealing *** order to simplify rim seal structure while ensuring high sealing efficiency,the current paper optimizes the flow path of the secondary air system and presents a new rim seal structure with auxiliary sealing holes transporting a certain amount of secondary sealing *** new structure was compared with the conventional counterpart using validated CFD methods,showing that the additional secondary sealing flow is possible to improve sealing efficiency in disk *** current paper investigates the secondary sealing flow with and without swirl(the angle of auxiliary sealing hole inclination is 0°and 45°respectively),while maintaining the total amount of the sealing flow,flowrate ratio of sealing air(main sealing flow rate versus secondary sealing flow rate=1:1,2:1,3:1,4:1),found that both two parameters have essential impacts on sealing *** relationship between these two parameters and sealing efficiency was obtained,and it provides a new philosophy for the design of rim seal in gas turbines.

关键词： rim seal sealing efficiency secondary sealing flow sealing flowrate ratio swirled flow