检索结果-南通市图书馆

Journal of Thermal Science 2015年第5期24卷 468-477页

作者： fu Jing-Lun LIU Jian-jun Key Laboratory of Advanced Energy and Power Institute of Engineering Thermophysics

The purpose of this paper is to improve the aerodynamic performances of the last stage turbine and the exhaust hood of a 600MW steam turbine under design and off design conditions. During operation, strong flow interactions between the turbine and the exhaust hood impose influences on the flow behavior in the hood and lead to the unsatisfactory aerodynamic performance of the turbine and exhaust hood. So the exhaust hood has the potential to be improved in terms of aerodynamic efficiency. Considering the flow interactions between the turbine and the exhaust hood, the profiles of the diffuser end-wall were optimized. The coupled model turbine and model exhaust hood calculations and experiments were carried out to validate the effects of the optimization. Model experiments show that the design modifications resulted in a substantial increase in the overall pressure recovery coefficient. The flow and aerodynamic performances of the full-scale last stage turbine and full-scale exhaust hood were simulated to explore the flow physics alterations to the modification of diffuser geometry. The wet steam was selected as the flow medium. The actual flow fields trader different operation conditions were analyzed.

关键词： steam turbine exhaust hood full scale coupling flow

PRESSURE TRANSIENT ANALYSIS OF HETEROGENOUS RESERVOIRS WITH IMPERMEABILITY BARRIER USING PERTURBATION BOUNDARY ELEMENT METHOD

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2005年第1期17卷 102-109页

作者： YINHong-jun HEYing-fu fuChun-quan DepartmentofPetroleumEngineering DaqingPetroleumInstituteDaqing163318China InstituteofPorousflowandFluidMechanics ChineseAcademyofSciencesLangfang065007China

The transient flow mathematical model of arbitrary shaped heterogeneous reservoirs with impermeability barrier is proposed in this paper. In order to establish this model, the perturbation method is employed and the solution of model is expanded into a series in powers of perturbation parameter. By using the Boundary Element Method (BEM) and Duhamel principle, wellbore pressure with effects of skins and wellbore storage is obtained. The type curves are plotted and analyzed considering effects of heterogeneity, arbitrary shape and impermeable barriers. Finally, the results obtained by perturbation boundary element method is compared with the analytical solution and is available for the transient pressure analysis of arbitrary shaped reservoirs.

关键词： heterogeneous reservoirs arbitrary shape impermeable barrier perturbation equation boundary element method pressure transient analysis type curves

Simulation of the Brownian coagulation of nanoparticles with initial bimodal size distribution via moment method

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2012年第5期28卷 1227-1237页

作者： Jian-Zhong Lin fu-jun Gan China Jiliang University Department of Mechanics Zhejiang University

The Brownian coagulation of nanoparticles with initial bimodal size distribution, i.e., mode i and j, is numerically studied using the moment method. Evolutions of particle number concentration, geometric average diameter and geometric standard deviation are given in the free molecular regime, the continuum regime, the free molecular regime and transition regime, the free molecular regime and continuum regime, respectively. The results show that, both in the free molecular regime and the continuum regime, the num- ber concentration of mode i and j decreases with increasing time. The evolutions of particle geometric average diameter with different initial size distribution are quite different. Both intra-modal and inter-modal coagulation finally make the polydispersed size distribution become monodispersed. As time goes by, the size distribution with initial bimodal turns to be unimoda/and shifts to a larger particle size range. In the free molecular regime and transition regime, the inter- modal coagulation becomes dominant when the number concentrations of mode i and j are of the same order. The effects of the number concentration of mode i and mode j on the evolution of geometric average diameter of mode j are negligible, while the effects of the number concentration of mode j on the evolution of geometric average diameter of mode j is distinct. In the free molecular regime and continuum regime, the higher the initial number concentration of mode j, the more obvious the variation of the number concentration of mode i.

关键词： Nanoparticles - Brownian coagulation. Bimodalsize distribution Moment method

Optimal aeroassisted symmetric transfer between coplanar elliptical orbits

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2013年第2期24卷 261-271页

作者： jun fu Hong Cai Shifeng Zhang College of Aerospace and Material Engineering National University of Defense Technology

The problem of optimal aeroassisted symmetric transfer between elliptical orbits is *** complete trajectory is assumed as consisting of two impulsive velocity changes at the beginning and the end of an interior atmospheric subarc,where the vehicle is controlled via the lift coefficient and *** corresponding dynamic equations are built and bounded controls are *** the purpose of optimization computation,the equations are *** order to minimize the total fuel consumption,the geocentric radius of initial elliptical transfer orbital perigee and controls during atmospheric flight should all be *** is an optimal control problem which involves additional parameter *** solve the problem,a two-level optimization method denoted by ＂genetic algorithm ＋ Gauss pseudospectral method＂ is adopted：the genetic algorithm is used for parameter optimization and the Gauss pseudospectral method is used for optimal control *** flow chart of simulation is *** this basis,the issue of more realistic modeling with two finite-thrust subarcs in the nonatmospheric part of the trajectory is simultaneously *** orbital transfer problem is transformed to three continuous optimal control problems,and the constraints at different times are given,which are respectively solved by using the Gauss pseudospectral *** obtained numerical results indicate that the optimal thrust control is of bangbang *** minimum-fuel trajectory in the atmosphere consists of aeroglide,aerocruise and *** are compared with the results of pure impulsive model,and the conclusions that a significant fuel saving will be achieved by synergetic maneuver are drawn.

关键词： aeroassisted orbital transfer Gauss pseudospectral method optimal control two-level optimization genetic algorithm synergetic maneuver

Hot deformation mechanism and microstructure evolution of an ultra-high nitrogen austenitic steel containing Nb and V

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2015年第10期22卷 1043-1049页

作者： Rong-hua Zhang Ze-an zhou Ming-wei Guo Jian-jun Qi Shu-hua Sun Wan-tang fu State Key Laboratory of Metastable Materials Science and Technology Yanshan University College of Metallurgy and Energy Hebei United University

The flow curves of an ultra-high nitrogen austenitic steel containing niobium(Nb) and vanadium(V) were obtained by hot compression deformation at temperatures ranging from 1000°C to 1200°C and strain rates ranging from 0.001 s-1 to 10 s-1. The mechanical behavior during hot deformation was discussed on the basis of flow curves and hot processing maps. The microstructures were analyzed via scanning electron microscopy and electron backscatter diffraction. The relationship between deformation conditions and grain size after dynamic recrystallization was obtained. The results show that the flow stress and peak strain both increase with decreasing temperature and increasing strain rate. The hot deformation activation energy is approximately 631 k J/mol, and a hot deformation equation is proposed.(Nb,V)N precipitates with either round, square, or irregular shapes are observed at the grain boundaries and in the matrix after deformation. According to the discussion, the hot working should be processed in the temperature range of 1050°C to 1150°C and in the strain rate range of 0.01 to 1 s-1.

关键词： austenitic steels hot deformation microstructural

Real-time total system error estimation: Modeling and application in required navigation performance

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2014年第6期27卷 1544-1553页

作者： fu Li Zhang jun Li Rui National Key Laboratory of CNS/ATM School of Electronic and Information Engineering Beihang University

In required navigation performance（RNP）, total system error（TSE） is estimated to provide a timely warning in the presence of an excessive error. In this paper, by analyzing the underlying formation mechanism, the TSE estimation is modeled as the estimation fusion of a fixed bias and a Gaussian random variable. To address the challenge of high computational load induced by the accurate numerical method, two efficient methods are proposed for real-time application, which are called the circle tangent ellipse method（CTEM） and the line tangent ellipse method（LTEM）,respectively. Compared with the accurate numerical method and the traditional scalar quantity summation method（SQSM）, the computational load and accuracy of these four methods are extensively analyzed. The theoretical and experimental results both show that the computing time of the LTEM is approximately equal to that of the SQSM, while it is only about 1/30 and 1/6 of that of the numerical method and the CTEM. Moreover, the estimation result of the LTEM is parallel with that of the numerical method, but is more accurate than those of the SQSM and the CTEM. It is illustrated that the LTEM is quite appropriate for real-time TSE estimation in RNP application.

关键词： Aviation Estimation Navigation Required navigation performance Total system error

NUMERICAL INVESTIGATION OF PERFORMANCE OF AN AXIAL-FLOW PUMP WITH INDUCER

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2007年第6期19卷 705-711页

作者： LI Yao-jun WANG fu-jun College of Water Conservancy and Civil Engineering China Agricultural University Beijing 100083 China

The interaction of flow through the inducer and impeller of an axial-flow pump equipped with an inducer has significant effect on its performance. This article presents a recent numerical investigation on this topic. The studied pump has an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of the impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. A computational fluid dynamics code was used to investigate the flow characteristics and performance of the axial-flow pump. For turbulence closure, the RNG k-ε model was applied with an unstructured grid system. The rotor-stator interaction was treated with a Multiple Reference Frame （MRF） strategy. Computations were performed in different cases： 7 different relative circumferential angles （ Δθ ） between the inducer blade trailing edge and the impeller blade leading edge, and 3 different axial gaps （G） between the inducer and the impeller. The variation of the hydraulic loss in the rotator was obtained by changing Δθ . The numerical results show that the pressure generated is minimum in the case of （ G = 3%D）, which indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances were predicted and compared to the experimental measurements. Recommendations for future modifications and improvements to the pump design were also given.

关键词： axial-flow pump inducer CFD numerical simulation of flow

Evaluation of hydraulic fracturing of horizontal wells in tight reservoirs based on the deep neural network with physical constraints

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2023年第2期20卷 1129-1141页

作者： Hong-Yan Qu Jian-Long Zhang fu-Jian zhou Yan Peng Zhe-jun Pan Xin-Yao Wu State Key Laboratory of Petroleum Resources and Prospecting China University of PetroleumBeijing102249China School of Artificial Intelligence China University of PetroleumBeijing102249China Unconventional Oil and Gas Institute China University of PetroleumBeijing102249China School of Petroleum Engineering China University of PetroleumBeijing102249China Key Laboratory of Continental Shale Hydrocarbon Accumulation and Efficient Development Ministry of EducationNortheast Petroleum UniversityDaqingHeilongjiang163318China Engineering Technology Research Institute PetroChina Xinjiang Oilfield CompanyKaramayXinjiang834000China

Accurate diagnosis of fracture geometry and conductivity is of great challenge due to the complex morphology of volumetric fracture network. In this study, a DNN (deep neural network) model was proposed to predict fracture parameters for the evaluation of the fracturing effects. Field experience and the law of fracture volume conservation were incorporated as physical constraints to improve the prediction accuracy due to small amount of data. A combined neural network was adopted to input both static geological and dynamic fracturing data. The structure of the DNN was optimized and the model was validated through k-fold cross-validation. Results indicate that this DNN model is capable of predicting the fracture parameters accurately with a low relative error of under 10% and good generalization ability. The adoptions of the combined neural network, physical constraints, and k-fold cross-validation improve the model performance. Specifically, the root-mean-square error (RMSE) of the model decreases by 71.9% and 56% respectively with the combined neural network as the input model and the consideration of physical constraints. The mean square error (MRE) of fracture parameters reduces by 75% because the k-fold cross-validation improves the rationality of data set dividing. The model based on the DNN with physical constraints proposed in this study provides foundations for the optimization of fracturing design and improves the efficiency of fracture diagnosis in tight oil and gas reservoirs.

关键词： Evaluation of fracturing effects Tight reservoirs Physical constraints Deep neural network Horizontal wells Combined neural network

Constitutive equation and hot processing maps of Al-5Ti-1B master alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2018年第8期37卷 668-674页

作者： fu-Wei Kang Jie zhou Zhi-Wei Wang Xue-Min Zhang Yi-Cheng Feng Er-jun Guo School of Materials Science and Engineering Harbin Universityof Science and Technology Harbin 150040 China Harbin Dong An Engine Group Corporation Ltd. Aviation Industry Corporation of China Harbin 150066 China

The isothermal compression tests of A1-5Ti- 1B master alloy were conducted on the thermal mechanical simulator Gleeble-1500D at the deformation temperature range of 300-450 ℃,the strain rate range of 0.01- 10.00 s^-l, and the engineering strain of 50 %. The effects of deformation temperatures and strain rates on the flow stress were analyzed by the true stress-true strain curves. The result indicates that the flow stress increases with the increase of strain rate, while it decreases with the increase of temperature. The hot deformation activation energy of A1-5Ti-IB master alloy is calculated to be 250.9 ***^-1, and the constitutive equation is established as ε=1.97 x lO^19[sinh（O.O15δ）^11.14exp（-250.9/RT）, and the validity of this constitutive equation is verified. Based on dynamic material model （DMM） criterion, the hot processing map of AI-5Ti-1B master alloy is obtained. The optimum hot extrusion conditions are determined as deformation temperature of 400℃ and strain rate of 1.00 s^-1, and the flow instability only appears at the temperature range of 300-340℃ at the base of the hot processing map.

关键词： Al-5Ti-1B master alloy Flow stress Constitutive equation Hot processing map

Preparation of Inoculants Used in Superalloy and Analysis of the Atomic Matching Models

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2013年第4期29卷 387-392页

作者： fu Wang jun Zhang Taiwen Huang Lin Liu Hengzhi fu State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The mechanisms of grain refinement were investigated on two kinds of grain refiners used in Ni-Fe based superalloys and complete atomic matching modes were constructed in this study. It is found that there are at least three matching crystal planes having the small lattice disregistry between the refiner and the nucleated phase, which can lead to grain refinement of γ matrix. The results indicate that the （0001）, （01-10） planes of CrFeNb have a fine crystallographic matching relationship with the （111）, （110） planes of γ matrix. The disregistry of （0001）CrFeNb//（111 ）γ, （011-0）CrFeNb//（111）γ and （0110）CrFeNb//（110）γ is 3.34%, 6.60% and 5.90%, respectively. The （0001）, （0110） planes of Co3FeNb2 and （111）, （110） planes of γ matrix also have this relationship. The disregistry of （0001）Co3FeNb2//（111）γ, （0001）Co3FeNb2//（110）γ, （0110）Co3FeNb2//（111）γ and （0110）Co3FeNb2//（110）γ, is 4.45%, 9.35%, 8.38% and 6.12%, respectively.

关键词： Grain refinement Growth mechanism Superalloy Solidification