检索结果-内蒙古大学图书馆

Application of multi-leaf foil bearings in high-speed turbo-machinery

JOURNAL OF ADVANCED MECHANICAL DESIGN SYSTEMS AND MANUFACTURING 2020年第6期14卷 1-16页

作者： Guo, Yu Hou, Yu Zhao, Qi Ren, Xionghao Lai, Tianwei Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Foil bearings, featuring various advantages (such as high-speed, good operation stability, low friction, long life, strong adaptability, wide temperature range, and oil-free), are promised to have good development prospects and application in high-speed centrifugal machinery. In order to evaluate the actual performance of the multi-leaf foil bearings and promote their further application in the high-speed turbo-machinery, the experimental research of multi-leaf foil bearings with rotor diameter of 25 mm are conducted in this paper. The static and transient tests of the multi-leaf journal bearings with different foil thickness are initiated on the journal bearing test rig to analyze their characteristics, such as the load-deflection, bearing Coulomb friction, start-up and operating friction torque, which could provide guidance for the structural parameter design and exploitation of the bearing. Afterwards, two different bearing combinations are adopted as the supporting components, namely A-type: multi-leaf foil journal bearing with aerostatic thrust bearing and B-type: multi-leaf foil journal bearing with multi-leaf foil thrust bearing. They are applied in the high-speed turbo machinery with the rotor diameter of 25 mm to assess the direct application of the multi-leaf foil bearings in high-speed turbo-machinery. The transient speed-up, high speed, and speed-down experiments of the rotor-bearing system are conducted and their transient characteristics and stability are compared. The experimental results indicate that the start-up (0.6x10(-2)similar to 1.8x10(-2)N.m) and steady operation frictional torque (0.25x10(-2)similar to 0.5x10(-2)N.m) of the multi-leaf foil journal bearing is relative small;the impeller-rotor system operates steadily and smoothly with good repeatability, supported by A-type and B-type, the maximum rotor speed at about 94krpm achieved in the tests is close under the support of A-type and B-type. However, there are smaller main frequency amplit

关键词： Turbo machinery Multi-leaf Foil bearing Aerodynamic Lubrication Stability study engineering application

来源：评论

学校读者我要写书评

暂无评论

power increase potential of coal-fired power plant assisted by the heat release of the thermal energy storage system: Restrictions and thermodynamic performance

引用

ENERGY 2024年 312卷

作者： Miao, Lin Yan, Hui Liu, Ming Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The integration of a thermal energy storage (TES) system is an effective way to improve the load cycling rate of coal-fired power plants (CFPPs). To evaluate the power increase potential and thermodynamic performance of CFPP supplied by heat release of the molten salt TES system, eight discharging modes for CFPP integrated with the TES system including steam injection, heater bypass, and additional turbine schemes were comparatively evaluated. The system simulation models of the integrated systems were developed and the thermodynamic performance of the proposed system were evaluated. Results show that the mode SI-HPT (high-pressure turbine steam injection) has the largest output power increase of 25.00 % under the benchmark condition of 75%THA, but the mode HB-LPH (low-pressure heater bypass) shows a very low output power increase of 2.08 %. Moreover, the power generation efficiency is changed by the external heat source through a change in the average heat absorption temperature of the Rankine cycle and the internal irreversibility of the steam/water cycle. Under the typical benchmark discharging condition of 75%THA, the power generation efficiency of the turbine in mode SI-LPT (low-pressure turbine steam injection) can be reduced from 47.41 % to 44.15%, but it can be increased from 47.41 % to 48.86% in mode SI-HPT. When the temperature ranges of the TES system are above 600 degrees C and below 450 degrees C, the modes SI-HPT and SI-LPT obtain the optimal comprehensive performance, respectively. This study can provide the scientific guidance for retrofit for CFPP to achieve efficient and flexible design.

关键词： Coal power Thermal energy storage Operational flexibility Energy analysis Exergy analysis

来源：评论

学校读者我要写书评

暂无评论

Low pressure premixed laminar n-heptane+propane/oxygen flames studied with tunable synchrotron photoionization 7

Low pressure premixed laminar n-heptane+propane/oxygen flame...

引用

7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Yu, W. Wei, L.X. Ma, Z.H. Huang, Z.H. Yuan, T. Tian, Z.Y. Li, Y.Y. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Low pressure premixed laminar n-heptane/propane/O2/N2 flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed experimental data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic model. © 2009 Combustion Institute. All rights reserved.

关键词： Combustion

来源：评论

学校读者我要写书评

暂无评论

Prediction of cavity length: Dimensionless group identification through neural network and active subspace method

引用

PHYSICS OF FLUIDS 2024年第7期36卷 073321-073321页

作者： Xu, Bo Yang, Kuang Hu, Hongfei Wang, Haijun Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The prediction of cavity length is very important for identifying cavitation state. This paper introduces a sophisticated framework aimed at predicting cavity length, leveraging the combination of neural network architecture with the active subspace method. The model identifies the dominant dimensionless group influencing cavity length in hydrofoil and venturi. For hydrofoil, a linear, negatively correlated relationship is found between cavity length and its dominant dimensionless number. Conversely, for venturi, an exponential, positively correlated relationship is identified. Using the found dominant dimensionless number to predict the dimensionless cavity length, the average relative errors are 0.146 and 0.136, respectively. The expression of the dominant dimensionless number, combined with the input parameters, is simplified into structural and physical functions, thereby significantly reducing the dimensionality of input while increasing the average relative error to 0.338. This study enhances the understanding of data-driven cavitation features and offers guidance for cavitation control and prevention.

关键词： Cavitation

来源：评论

学校读者我要写书评

暂无评论

Features selection for recognition of severe slugging in a long pipeline with an S-shaped riser by decision tree

引用

flow MEASUREMENT AND INSTRUMENTATION 2024年 96卷

作者： Xu, Qiang Li, Xiangyu Jiang, Shuaizhi Wang, Xinyu Liu, Chenying Wang, Chan Chang, Qiuxiang Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

In deep -sea oil and gas, S-shaped riser is the key equipment to transport the multiphase working substance produced underwater to the surface platform. The occurrence of severe slugging will seriously threaten the safe production of offshore oil and gas fields. Therefore, accurate and rapid recognition of hazardous flow patterns such as severe slugging is an urgent need to ensure the safety of multiphase flow in deep -sea long -distance pipelines. This paper has built a set of long S-shaped riser with industrial parameters, including 1687 m horizontal and downward inclined pipelines and 16.7 m S-shaped riser. The gas-liquid two-phase flow patterns, including severe slugging, oscillating flow and stable flow, are studied in this system. The pressure and differential pressure features of different signals are extracted from different positions along the pipeline, and a more comprehensive and reasonable evaluation criterion of signal performance is established. Making use of the advantages of visualization of the structure of decision tree, a new method to evaluate the recognition effect of features is proposed based on its classification principle. The original signal is decomposed into components of different scales through wavelet multi-scale analysis, and then the statistical features with good flow pattern differentiation ability are calculated. It is found that the mean of wavelet approximate component has the best recognition effect among all features. On the basis of feature correlation analysis, 7 features with high recognition rate applicable to 22 signals along the pipeline are optimally selected from 13 original features. For the water differential pressure signal DP13, the recognition rate obtained by using its 4 optimal features is 91.4 %, and the error between the recognition rate obtained by using all features is only 0.2 %. The overall recognition rate of the signal is the highest and the practicability is the best. When the sample duration is 6.2s, t

关键词： flow pattern Severe slugging Feature selection Correlation analysis Pipeline -riser Decision tree

来源：评论

学校读者我要写书评

暂无评论

Scale Effect on Producing Gaseous and Liquid Chemical Fuels via CO2 Reduction

引用

ENERGIES 2022年第1期15卷 335-335页

作者： Liu, Ya Lei, Dan Guo, Xiaoqi Ma, Tengfei Wang, Feng Chen, Yubin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Producing chemical fuels from sunlight is a sustainable way to utilize solar energy and reduce carbon emissions. Within the current photovoltaic-electrolysis or photoelectrochemical-based solar fuel generation system, electrochemical CO2 reduction is the key step. Although there has been important progress in developing new materials and devices, scaling up electrochemical CO2 reduction is essential to promote the industrial application of this technology. In this work, we use Ag and In as the representative electrocatalyst for producing gas and liquid products in both small and big electrochemical cells. We find that gas production is blocked more easily than liquid products when scaling up the electrochemical cell. Simulation results show that the generated gas product, CO, forms bubbles on the surface of the electrocatalyst, thus blocking the transport of CO2, while there is no such trouble for producing the liquid product such as formate. This work provides methods for studying the mass transfer of CO, and it is also an important reference for scaling up solar fuel generation devices that are constructed based on electrochemical CO2 reduction.

关键词： electrochemical CO2 CO formate fuel

来源：评论

学校读者我要写书评

暂无评论

High-performance aerodynamic design of supercritical CO2 centrifugal compressor for the Megawatt-class nuclear microreactor (MSC-GFR)

引用

NUCLEAR engineering AND DESIGN 2023年 413卷

作者： Li, Yuzhe Ma, Qixiang Zhang, Enbo Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Design of the SCO2 centrifugal compressor is critical for the fuel economy and power output of the nuclear microreactors. In this study, we developed a high-performance aerodynamic design & analysis platform (XJHPCCD) for real-gas centrifugal compressors. Based on the single-zone method, the platform realizes efficient and fast solution to the direct and inverse problems of centrifugal stages in real gases. Using the XJHPCCD platform, we performed a principal component analysis on the performance prediction errors in different combinations of the multiply expressed loss mechanisms. On the results of composite analysis, an optimal loss model was proposed regarding the hundred-kW SCO2 compressor in Megawatt-class microreactors. By coupling the optimal loss model in performance prediction, the errors of pressure rises were reduced from 5-10% to 3% for the Sandia's verified model, greatly promoting the reliability of aerodynamic analyses. To demonstrate the engineering values of the specifically optimized toolkit, we numerically conducted a design research on the main compressor of a 1 MWt SCO2-cooled fast breeder microreactor (MSC-GFR). Results showed the XJHPCCD platform (coupled with the optimal loss model) has well satisfied the technical demands with high-performance aerodynamic design and low prediction errors. Thereby, it is proved that we have successfully proposed a specifically optimized aerodynamic toolkit for the component design of Megawatt-class microreactors.

关键词： Megawatt microreactor Supercritical carbon dioxide Centrifugal compressor Aerodynamic design & analysis The single-zone method Loss model

来源：评论

学校读者我要写书评

暂无评论

flow measurement based on the combination of swirler and differential pressure under slug flow

引用

flow MEASUREMENT AND INSTRUMENTATION 2022年 88卷

作者： Zhang, Xuemei Wang, Haocun Xu, Qiang Ma, Xiaojun Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The alternating appearance of elongated bubbles and liquid slugs of slug flow in the pipe causes severe pressure fluctuation. As a result, measuring the flow rate of the slug flow with the throttling unit based differential pressure method is difficult. This paper investigates a new swirler-based flow measurement method in slug flow. The swirler converts the slug flow into a swirling annular flow, and the differential pressure method is used to measure the flow rate. The influences of gas and liquid flow rates on the differential pressure dPX across the swirler as well as its downstream axial differential pressure dPZ are investigated. dPX0.5 increases linearly as the liquid mass flow rate increases, and the slope of the curve increases as the gas mass flow rate increases. The influence of gas mass flow rate on dPX0.5 is comparable to that of liquid mass flow rate on dPX0.5. dPZ0.5 increases linearly with increasing gas/liquid mass flow rate, and the slope of the curve of dPZ0.5 with ml differs slightly from the slope of the curve in single-phase water conditions. Based on the research presented above, new empirical correlations of mass flow rate based on dPX and dPZ are established respectively. The superficial liquid velocity ranges from 0.6 to 2 m per second, while the superficial gas velocity ranges from 2 to 6 m per second. If the gas mass flow rate and dPX are known, the relative error of liquid mass flow is less than 3%. The relative error of the gas mass flow rate is less than 10% if the liquid mass flow rate and dPX are given. The calculation accuracy of the flow measurement model using dPX is better than the calculation accuracy of the flow measurement model using dPZ.

关键词： Gas-liquid two-phase flow Swirler flow measurement Differential pressure

来源：评论

学校读者我要写书评

暂无评论

Numerical study on the evolution characteristics of phase interface of subsonic and sonic steam jets in transverse subcooled flow

引用

NUCLEAR engineering AND DESIGN 2023年第1期411卷

作者： Xu, Qiang Liu, Qimeng Li, Xiangyu Wang, Hanxuan Liu, Chenying Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The cooling process of high-temperature steam ejecting into subcooled liquid widely exists in industrial pro-duction, with high mass and heat transfer efficiency. This paper establishes an unsteady numerical simulation method for jet condensation based on the two-fluid model and the thermal phase change model, focusing on the phase interface evolution and pressure fluctuation characteristics of steam jets in the crossflow of subcooled water under different mass fluxes. With the increase of mass flux, the ability of the jet plume to resist water flow is enhanced;thus, the heat and mass transfer at the two-phase interface becomes more stable;the length of the plume increases, and the range of oscillation of the plume length in the axial direction and the radial direction decreases. The pressure vortex that generated by the two-phase region and the subcooled water is more stable with reduced total pressure fluctuations. Under subsonic conditions, bubbles are shed on the leeward side, and the ranges of axial oscillation, radial oscillation and total pressure oscillation are 1.57de-3.41de, 0.21de-0.37de, and 0.17de-0.32de, respectively. The steam plume becomes progressively longer in the axial direction as the steam velocity increases from subsonic to sonic and supersonic speeds, and the range of interfacial oscillations and total pressure fluctuations along the radial direction are further reduced. Under the same working condition, with the increase of axial distance, the momentum of the steam jet decreases, the ability to resist the impact of water flow decreases, and the windward side is greatly affected;the axial and radial amplitude fluctuations of the pressure increases, with the amplitude on the windward side being significantly larger than that on the leeward side, and the maximum difference between the fluctuations on both sides increases continuously. The momentum change of the two-phase interface is intense, which is the main factor of pressure fluctuation. Th

关键词： Jet condensation Steam plume Interface morphology Interface fluctuations Pressure oscillations Correlation analysis

来源：评论

学校读者我要写书评

暂无评论

Effects of mixed sacrificial reagents on hydrogen evolution over typical photocatalysts

引用

JOURNAL OF PHOTONICS FOR ENERGY 2020年第2期10卷

作者： Jiang, Yuzhou Mao, Liuhao Shi, Jinwen Zheng, Botong Guan, Xiangjiu Liu, Fei Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian Peoples R China Xi An Jiao Tong Univ Suzhou Acad Suzhou Peoples R China Xidian Univ Sch Adv Mat & Nanotechnol Xian Peoples R China

Sacrificial reagents (SRs) are widely used in photocatalytic H-2-evolution systems, and the physical/chemical properties of SRs may be changed after mixing. In our study, triethanolamine, methanol, and lactic acid were selected as three kinds of typical organic SRs, which were of alkaline amine, neutral alcohol, and acidic carboxylic acids, respectively. Graphic carbon nitride (g-C3N4) and titanium dioxide (TiO2), which are of metal-free polymerized-organic and metal-oxide inorganic semiconductors, respectively, were selected as two kinds of typical photocatalysts. By measuring and comparing the photocatalytic H-2-evolution performance of g-C3N4 and TiO2 in single-sacrificial-reagent systems, corresponding binary-sacrificial-reagent systems, and trinary-sacrificial-reagent (TSR) systems, the effects of mixed-sacrificial-reagents (MSRs) on H-2 evolution over these two typical photocatalysts were investigated. It was found that the photocatalytic H-2-evolution rates could be enhanced by mixing appropriate SRs to corresponding photocatalysts, for instance, TiO2 showed the best photocatalytic performance in 20% TSR system. However, g-C3N4 showed the best photocatalytic performance in 20% triethanolamine compared with MSR systems. The effects of MSRs on H-2 evolution over typical photocatalysts could be explained by the adsorptivity between SRs and photocatalysts. Functional groups of SRs that are concerned with the adsorption between SRs and photocatalysts might change in the MSR systems. The weakening of adsorption between SRs and photocatalysts led to the decreased photocatalytic H-2 evolution rates over photocatalysts. We provide useful guidance to the design of MSR systems in order to promote the photocatalytic H-2 evolution. (C) 2019 Society of Photo Optical Instrumentation Engineers (SPIE)

关键词： adsorption hydrogen photocatalysis sacrificial reagent solar energy

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：