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| 1 | Experimental and Numerical Studies of Vitiated Air Effects on Hydrogen-fueled Supersonic Combustor Performance显示文摘This paper deals with the vitiation effects of test air on the scramjet performance in the ground combustion heated facilities. The primary goal is to evaluate the effects of H2O and CO2, the two major vitiated species generated by combustion heater, on hydrogen-fueled supersonic combustor performance with experimental and numerical approaches. The comparative experiments in the clean air and vitiated air are conducted by using the resistance heated direct-connected facility, with the typical Mach 4 flight conditions simulated. The H2O and CO2 species with accurately controlled contents are added to the high enthalpy clean air from resistance heater, to synthesize the vitiated air of a combustion-type heater. Typically, the contents of H2O species can be varied within the range of 3.5%-30% by mole, and 3.0%-10% for CO2 species. The total temperature, total pressure, Mach number and O2 mole fraction at the combustor entrance are well-matched between the clean air and vitiated air. The combustion experiments are completed at the fuel equivalence ratios of 0.53 and 0.42 respectively. Furthermore, three-dimensional (3D) reacting flow simulations of combustor flowpath are performed to provide insight into flow field structures and combustion chemistry details that cannot resolved by experimental instruments available. Finally, the experimental data, combined with computational results, are employed to analyze the effects of H2O and CO2 vitiated air on supersonic combustion characteristics and performance. It is concluded that H2O and CO2 contaminants can significantly inhibit the combustion induced pressure rise measured from combustor wall, and the pressure profile decreases with the increasing H2O and CO2 contents in nonlinear trend; simulation results agree well with experimental data and the overall vitiation effects are captured; direct extrapolation of the results from vitiated air to predict the performance of actual flight conditions could result in over-fueling the combustor, possible inlet un-start and inappropriate combustion mode transition. The detailed analysis and discussion are presented and the research conclusions are summarized. | LUO Feiteng SONG Wenyan ZHANG Zhiqiang LI Weiqiang LI Jianping | 2012 | Chinese Journal of Aeronautics2012，25，2： | 5 |
| 2 | Network traffic classification based on ensemble learning and co-training显示文摘Classification of network traffic is the essential step for many network researches. However,with the rapid evolution of Internet applications the effectiveness of the port-based or payload-based identifi-cation approaches has been greatly diminished in recent years. And many researchers begin to turn their attentions to an alternative machine learning based method. This paper presents a novel machine learning-based classification model,which combines ensemble learning paradigm with co-training tech-niques. Compared to previous approaches,most of which only employed single classifier,multiple clas-sifiers and semi-supervised learning are applied in our method and it mainly helps to overcome three shortcomings:limited flow accuracy rate,weak adaptability and huge demand of labeled training set. In this paper,statistical characteristics of IP flows are extracted from the packet level traces to establish the feature set,then the classification model is created and tested and the empirical results prove its feasibility and effectiveness. | HE HaiTao LUO XiaoNan MA FeiTeng CHE ChunHui WANG JianMin | 2009 | Science in China(Series F)2009，52，2： | 5 |
| 3 | Influences of Geometric Parameters upon Nozzle Performances in Scramjets显示文摘这篇文章调查并且介绍在它的嘴表演之上施加的一个超音速冲压式喷气发动机的几何参数的影响。这些参数包括分叉的角度,全部的长度,高度比率,在长度,和在角度。在超音速冲压式喷气发动机嘴以内的流动地被与联合含蓄的解答者和一个 RNG k- 骚乱模型联合使用 CFD softwareFLUENT 数字地模仿。 | Li Jianping Song Wenyan Xing Ying Luo Feiteng | 2008 | Chinese Journal of Aeronautics2008，21，6： | 4 |
| 4 | Effect of inlet-valve structures on thrust of airbreathing pulse detonation engines显示文摘Experimental studies were conducted in order to improve the understanding of the thrust generation and the pressure/flame reverse propagation of the air-breathing pulse detonation engines(APDEs)with self-designed inlets and valves structures.The present experimental research utilized a gasoline/air APDE(with 68 mm inner-diameter,2050 mm length and maximum operating frequency not less than 40 Hz which was as a benchmark structure)at different operating frequencies,with freestream air inflow of 1.1 atm and 0℃.The theoretical equivalence ratio of gasoline/air was 1.Two kinds of inlets with centerbody or without were considered and combined with two kinds of self-designed valves(the elastic-valve and the convergent aero-valve)specially designed for comparative experiments.During the test,the inflow parameters,the pressure along the longitudinal direction inside the engine and the thrust force were measured for the APDE operating characteristic analysis,including the detonation combustion,the aerodynamic drag,the pressure/flame reverse propagation and the thrust generation.The research results indicate that:The inlet centerbody does not increase drag but plays a positive effect on airflow stability and operation matching.The elastic-valve and the convergent aero-valve,though increase the inlet aerodynamic drag,have obvious effects on suppressing the detonation wave and pressure forward propagation,resulting in effective thrust increase.Effects of the convergent aero-valve are the best when the flow choked,while the effects of elastic-valve are better and continuously stable in a wider range of frequency.The wmaximum nondimensional thrust increases with the elastic-valve is reached about 1.12 at the frequency of 8-9 Hz,and about 0.97 with the convergent aero-valve at the frequency of 7 Hz.The maximum fuel specific impulse is 2514.6 s when using the convergent aerovalve.And this study provides technical reserve for the APDE optimization design. | Wenjuan Chen Wei Fan Feiteng Luo Gaohu Tang Yaosong Long | 2021 | Propulsion and Power Research2021，10，4： | 1 |
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