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Numerical Investigation of the Effects of ITD Length on Low Pressure Nozzle

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Journal of Thermal Science 2017年第3期26卷 199-207页

作者： LIU Guang LIU Jun Liu Hongrui Wang Pei du qiang Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The advantage of high efficiency, low SFC(Specific Fuel Consumption), ultra-high bypass ratio turbofan engine attracts more and more attention in modern commercial engine. The intermediate turbine duct(ITD), which connects high pressure turbine(HPT) with low pressure turbine(LPT), has a critical impact on the overall performance of turbine by guiding flow coming from HPT to LPT without too much loss. Therefore, it becomes more and more urgent to master the technique of designing aggressive, even super-aggressive ITD. Much more concerns have been concentrated on the duct. However, in order to further improve turbine, LPT nozzle is arranged into ITD to shorten low pressure axle. With such design concept, it is obvious that LPT nozzle flow field is easily influenced by upstream duct structure, but receives much less interests on the contrary. In this paper, numerical method is used to investigate the effects of length of ITD with upstream swirl blades on LPT nozzle. Nine models with the same swirl and nozzle blades, while the length of ITD is the only parameter to be changed, will be discussed. Finally, several conclusions and advices for designers are summarized. After changing axial length of ducts, inlet and outlet flow field of nozzle differs, correspondingly. On the other hand, the shearing stress on nozzle blade(suction and pressure) surface presents individual feature under various inlet flow. In addition to that, "Clocking-like effect" is described in this paper, which will contribute much to the pressure loss and should be paid enough attention.

关键词：中间的汽轮机管长度嘴迫使损失

Effects of Rising Angle on Upstream Blades and Intermediate Turbine duct

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Journal of Thermal Science 2016年第4期25卷 293-301页

作者： LIU Jun WANG Pei du qiang LIU Guang ZHU Junqiang Institute of Engineering Thermophysics Chinese Academy of Sciences

With the improvement of requirement,design and manufacture technology,aero-engines for the future are characterized by further reduction in fuel consumption,cost,but increment in propulsion efficiency,which leads to ultra-high bypass *** intermediate turbine duct(ITD),which connects the high pressure turbine(HPT) with the low pressure turbine(LPT),has a critical impact on the overall performances of such future ***,it becomes more and more urgent to master the design technique of aggressive,even super-aggressive *** the last years,a lot of research works about the flow mechanism in the diffuser ducts were carried *** achievements were reported,but further investigation should be *** the aid of numerical method,this paper focuses on the change of performance and flow field of ITD,as well as nearby turbines,brought by rising angle(RA).Eight ITDs with the same area ratio and length,but different RAs ranges from 8 degrees to 45 degrees,are *** to the investigation,flow field,especially outlet Ma of swirl blade is influenced by RA under potential effect,which is advisable for designers to modify HPT rotor blades after changing *** addition to that,low velocity area moves towards upstream until the first bend as RA increases,while pressure loss distribution at S2 stream surface shows that hub boundary layer is more sensitive to RA,and casing layer keeps almost *** the other hand,the overall total pressure loss could keep nearly equivalent among different RA cases,which implies the importance of optimization.

关键词：旋流叶片上游升角航空发动机涡轮转子叶片设计变更制造技术低压涡轮

Effects of Nozzle-Strut Integrated Design Concepton on the Subsonic Turbine Stage Flowfield

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Journal of Thermal Science 2014年第5期23卷 494-504页

作者： LIU Jun du qiang LIU Guang WANG Pei ZHU Junqiang Institute of Engineering Thermophysics Chinese Academy of Sciences

In order to shorten aero-engine axial length,substituting the traditional long chord thick strut design accompanied with the traditional low pressure(LP) stage nozzle,LP turbine is integrated with intermediate turbine duct(ITD).In the current paper,five vanes of the first stage LP turbine nozzle is replaced with loaded struts for supporting the engine shaft,and providing oil pipes circumferentially which fulfilled the areo-engine structure ***,their bulky geometric size represents a more effective obstacle to flow from high pressure(HP) turbine *** five struts give obvious influence for not only the LP turbine nozzle but also the flowfield within the ITD,and hence cause higher *** investigation has been undertaken to observe the influence of the Nozzle-Strut integrated design concept on the flowfield within the ITD and the nearby nozzle *** to the computational results,three main conclusions are finally ***,a noticeable low speed area is formed near the strut's leading edge,which is no doubt caused by the potential flow ***,more severe radial migration of boundary layer flow adjacent to the strut's pressure side have been found near the nozzle's trailing *** boundary layer migration is obvious,especially close to the shroud ***,radial pressure gradient aggravates this ***,velocity distribution along the strut's pressure side on nozzle's suction surface differs,which means loading variation of the *** it will no doubt cause nonuniform flowfield faced by the downstream rotor blade.

关键词：集成设计涡轮机内流场喷嘴轻钢亚音速转子叶片低压涡轮

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

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