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Simulation study of the influence of leak electrons on the discharge characteristics of a cusped field thruster

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Plasma Science and Technology 2019年第4期21卷 115-122页

作者： Hui lIU Xiang NIU Huan WU daren YU lab of Plasma Propulsion.Harbin Institute of Technology(HIT) Harbin 150001.People's Republic of China Department of Mechanical and Aerospace Engineering University of CaliforniaLos AngelesCA 90095.United States of America

Previous studies have shown that leak electro ns in cusped field thrusters can move along the channel axis to the anode after crossing the magnetic cusp on the *** this paper,a onedimensional fluid model is built along two typical electron paths to study the influence of leak electrons on the discharge characteristics of a cusped field thruster,considering the electron temperature *** is found that the frequencies of low-frequency oscillations increase with a decrease in the proportion of leak electrons,which is related to an increase in the ion speed in the *** results show that the position of the peak electron temperature is near the magnetic cusp on the exit and the position of the peak electron density is located downstream from the middle magnetic *** a decrease in the proportion of the leak electrons,the peak electron temperature and peak electron density decrease and the position of the peak electron density moves away from the exit,which is related to a decrease in the potential fall on the exit and an increase in confinement of electrons to the middle magnetic cusp.

关键词： leak electrons cusped field thruster low-frequency oscillations electron lemperature,ionization

Anomaly detection of hot components in gas turbine based on frequent pattern extraction

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Science China(Technological Sciences) 2018年第4期61卷 567-586页

作者： lIU JinFu ZHU linHai MA YuJia lIU Jiao ZHOU WeiXing YU daren School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China AVIC Electromechanical(Shenyang)Sanyo Refrigeration Equipment Co.ltd. Shenyang 110027China

Hot components operate in a high-temperature and high-pressure environment. The occurrence of a fault in hot components leads to high economic losses. In general, exhaust gas temperature(EGT) is used to monitor the performance of hot ***, during the early stages of a failure, the fault information is weak, and is simultaneously affected by various types of interference, such as the complex working conditions, ambient conditions, gradual performance degradation of the compressors and turbines, and noise. Additionally, inadequate effective information of the gas turbine also restricts the establishment of the detection model. To solve the above problems, this paper proposes an anomaly detection method based on frequent pattern extraction. A frequent pattern model(FPM) is applied to indicate the inherent regularity of change in EGT occurring from different types of interference. In this study, based on a genetic algorithm and support vector machine regression, the relationship model between the EGT and interference was tentatively built. The modeling accuracy was then further improved through the selection of the kernel function and training data. Experiments indicate that the optimal kernel function is linear and that the optimal training data should be balanced in addition to covering the appropriate range of operating conditions and ambient temperature. Furthermore, the thresholds based on the Pauta criterion that is automatically obtained during the modeling process, are used to determine whether hot components are operating abnormally. Moreover, the FPM is compared with the similarity theory, which demonstrates that the FPM can better suppress the effect of the component performance degradation and fuel heat value fluctuation. Finally, the effectiveness of the proposed method is validated on seven months of actual data obtained from a Titan130 gas turbine on an offshore oil platform. The results indicate that the proposed method can sensitively dete

关键词： frequent pattern model(FPM) support vector machine regression(SVR) genetic algorithm(GA) gas turbine hot components anomaly detection

Thermodynamic analysis for a chemically recuperated scramjet

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Science China(Technological Sciences) 2012年第11期55卷 3204-3212页

作者： QIN Jiang BAO Wen ZHANG Silong SONG YuFei YU daren Harbin Institute of Technology Harbin 150001China

Endothermic hydrocarbon fuel is regarded as an optimal fuel for a scramjet with regenerative cooling,which provides extra cooling through endothermic chemical conversion to avoid the severly limited cooling capacity when conventional fuels are adopted for *** endothermic cooling is proposed from the view point that the heat sink of a conventional fuel is insufficient,the heat-absorbing through endothermic chemical reaction is actually a chemical recuperation process because the wasted heat dissipated from the engine thermal structure is recovered through the endothermic chemical ***,the working process of a scramjet with endothermic hydrocarbon fuel cooling is a chemical recuperative *** analyze the chemical recuperative cycle of a chemically recuperated scramjet engine,we defined physical and chemical recuperation effectivenesses and heating value increment rate,and derived engine performance parameters with chemical *** heat value benefits from both physical and chemical recuperations,and it increases with the increase in recuperation *** scramjet performance parameters also increase with the increase in chemical recuperation *** increase in chemical recuperation effectiveness improves both the performances of the fuel cooling system and the combustion *** results of analysis prove that the existence of a chemical recuperation process greatly improves the performance of the whole scramjet.

关键词： scramjet endothermic hydrocarbon fuel chemical recuperation regenerative cooling chemical reaction

Recent research progress on airbreathing aero-engine control algorithm

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Propulsion and Power Research 2022年第1期11卷 1-57页

作者： Chengkun lv Juntao Chang Wen Bao daren Yu Harbin Institute of Technology Heilongjiang150001China

Airbreathing aero-engines are regarded as excellent propulsion devices from ground takeoff to hypersonic flight,and require control systems to ensure their efficient and safe ***,the present paper aims to provide a summary report of recent research progress on airbreathing aero-engine control to help researchers working on this ***,five control problems of airbreathing aero-engines are classified:uncertainty problem,multiobjective and multivariable control,fault-tolerant control,distributed control system,and airframe/propulsion integrated control ***,the research progress of aircraft gas turbine engine modelling,linear control,nonlinear control,and intelligent control is reviewed,and the advantages and disadvantages of various advanced control algorithms in aircraft gas turbine engines is ***,several typical hypersonic flight tests are investigated,and the modelling and control issues of dual-mode scramjet are ***,modelling,mode transition control and thrust pinch control for turbine-based combined cycle engines are ***,significant hypersonic airframe/propulsion integrated system control is ***,the study provides specific control research topics that require attention on airbreathing aero-engines.

关键词： Airbreathing aeroengine Control Aircraft gas turbine engine Dual-mode scramjet Combined cycle engine Hypersonic airframe/propulsion integrated system

Application of cloud multi-spectral radiances in revealing cloud physical structures

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Earth and Planetary Physics 2019年第2期3卷 126-135页

作者： Juan Huo daren lu WenJing Xu Key laboratory for Atmosphere and Global Environment Observation Chinese Academy of Sciences

The radiances scattered or emitted by clouds demonstrate diverse features at different wavelengths due to different cloud physical structures. This paper presents a method(the smallest-radiance-distance method, SRaDM) of revealing the physical structures of clouds. The method is based on multi-spectral radiances measured by the Moderate Resolution Imaging Spectroradiometer(MODIS)onboard Aqua. The principle and methodology of SRaDM is deduced and provided in this paper. Correlation analysis based on data from MODIS and Cloud Profiling Radar(onboard CloudSat), collected from January 2007 to December 2010 over an ocean area(15°N–45°N,145°E–165°E), led to selection of radiances at 13 wavebands of MODIS that demonstrated high sensitivity to cloud physical structures;radiances at the selected wavebands were subjected to SRaDM. The Standardized Euclidean distance is introduced to quantify the degree of changes in multi-spectral radiances(termed D_(rd)) and in physical structures(termed D_(st)) between cloud profiles. Statistics based on numerous cloud profiles show that D_(rd) decreases monotonically with a decrease in D_(st), which implies that small D_(rd) always accompanies small D_(st). According to the law of D_(rd) and D_(st), the new method, SRaDM, for revealing physical structures of clouds from the collocation of cloud profiles of similar multi-spectral radiances, is presented. Then, two successful experiments are presented in which cloud physical structures are captured using multi-spectral radiances. SRaDM provides a way to obtain knowledge of the physical structures of clouds over relatively larger areas, and is a new approach to obtaining 3D cloud fields.

关键词： cloud physical structure radiance radar

Nonlinearity of initiating and extinguishing boundaries of DBDs with airflows

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Plasma Science and Technology 2021年第6期23卷 41-47页

作者： Miao TANG Jingfeng TANG Desheng ZHOU daren YU Harbin Institute of Technology Harbin 150001People's Republic of China

Various applications of volume dielectric barrier discharges(DBDs)with airflows have attracted significant attention such as in the fields of plasma medicine,surface modification,ozone synthesis,*** this work,the nonlinearity characteristics of DBDs in initiating and extinguishing boundaries with airflows are experimentally *** is found that the difference between initiating pulse repetition frequencies(PRFs)and extinguishing PRFs is affected by the addition of airflows.A hysteresis region is produced between these two PRFs.A topological rule of Thom's classification theorem is proposed to investigate the hysteresis phenomenon of discharges with *** is concluded that the discharge state is dependent on the operation *** discharge state would transit from initiating to extinguishing,or in the opposite direction,while passing along a specific operation *** on the topological method,two nonlinear laws of discharge structure transition under the typical operation routes are predicted and verified in the discharge experiments.

关键词： nonlinearity topological rules initiating and extinguishing boundaries DBDs

昌波水电站引水式电站水轮发电机组防飞逸保护措施方案研究

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四川水力发电 2024年第4期43卷 91-94页

作者：卢修迪莫春霞邓达人中国电建集团贵阳勘测设计研究院有限公司贵州贵阳550081

针对昌波水电站引水式电站引水距离长、设置上游调压室、蜗壳前进水管直径较大等特点,列出三种水轮发电机组防飞逸保护措施进行分析比选,经综合比选分析后,推荐采用调压室快速闸门作为水轮发电机组的防飞逸保护措施,并详细描述了调压室... 详细信息

针对昌波水电站引水式电站引水距离长、设置上游调压室、蜗壳前进水管直径较大等特点,列出三种水轮发电机组防飞逸保护措施进行分析比选,经综合比选分析后,推荐采用调压室快速闸门作为水轮发电机组的防飞逸保护措施,并详细描述了调压室快速闸门方案。该研究为类似条件的水电站机组防飞逸保护措施方案选择提供参考。

关键词：防飞逸保护措施水轮发电机组调压室快速闸门

Novel methylxanthine derivative-mediated anti-inflammatory effects in inflammatory bowel disease

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World Journal of Gastroenterology 2014年第5期20卷 1127-1138页

作者： In-Ah lee Alan Kamba daren low Emiko Mizoguchi Gastrointestinal Unit Department of Medicine Harvard Medical School Center for the Study of Inflammatory Bowel Disease Massachusetts General Hospital Harvard Medical School

Family 18 chitinases have a binding capacity with chitin, a polymer of N-acetylglucosamine. Recent studies strongly suggested that chitinase 3-like 1(CHI3l1, also known as YKl-40) and acidic mammalian chitinase, the two major members of family 18 chitinases, play a pivotal role in the pathogenesis of inflammatory bowel disease(IBD), bronchial asthma and several other inflammatory disorders. Based on the data from highthroughput screening, it has been found that three methylxanthine derivatives, caffeine, theophylline, and pentoxifylline, have competitive inhibitory effects against a fungal family 18 chitinase by specifically interacting with conserved tryptophans in the active site of this protein. Methylxanthine derivatives are also known as adenosine receptor antagonists, phosphodiesterase inhibitors and histone deacetylase inducers. Anti-in-flammatory effects of methylxanthine derivatives have been well-documented in the literature. For example, a beneficial link between coffee or caffeine consumption and type 2 diabetes as well as liver cirrhosis has been reported. Furthermore, theophylline has a long history of being used as a bronchodilator in asthma therapy, and pentoxifylline has an immuno-modulating effect for peripheral vascular disease. However, it is still largely unknown whether these methylxanthine derivativemediated anti-inflammatory effects are associated with the inhibition of CHI3l1-induced cytoplasmic signaling cascades in epithelial cells. In this review article we will examine the above possibility and summarize the biological significance of methylxanthine derivatives in intestinal epithelial cells. We hope that this study will provide a rationale for the development of methylxanthine derivatives, in particular caffeine,-based antiinflammatory therapeutics in the field of IBD and IBDassociated carcinogenesis.

关键词： Adherent-invasive Escherichia coli Chitinase 3-like 1 Chitinase inhibitors Intestinal epithelial cells Host-microbial interactions Inflammatory bowel disease

Power generation and heat sink improvement characteristics of recooling cycle for thermal cracked hydrocarbon fueled scramjet

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Science China(Technological Sciences) 2011年第4期54卷 955-963页

作者： BAO Wen QIN Jiang ZHOU WeiXing ZHANG Duo YU daren Harbin Institute of Technology Harbin 150001China

In order to further investigate how much fuel heat sink could be increased and how much power generation could be obtained by using recooling cycle for a regeneratively cooled scramjet,the energy conversion from heat to electricity and the fuel heat sink increase in recooling cycle are experimentally investigated for fuel conversion rate and components of gas cracked fuel products at different fuel *** results indicate that the total fuel heat sink(i.e.,physical+chemical+recooling) of a recooling cycle is obviously higher than the heat sink of fuel itself,and the maximum heat sink increment is as high as 0.4 MJ/kg throughout the recooling ***,the cracked fuel mixture has a significant capacity of doing *** thermodynamic power generation scheme,which adopts the cracked fuel gas mixture as the working fluid,is a potential power generation cycle,and the maximum specific power generation is about 500 kW/***-pump scheme using cracked fuel gas mixture is also a potential fuel feeding cycle.

关键词： recooling cycle scramjet heat sink power generation thermal cracking