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On theory and methods for advanced detonation-driven hypervelocity shock tunnels

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National Science Review 2020年第7期7卷 1198-1207页

作者： Zonglin Jiang Jinping Li Zongmin Hu yunfeng liu Hongru Yu State Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Department of Aerospace Engineering Science School of Engineering Science University of Chinese Academy of Sciences

This study describes theory and methods for developing detonation-driven shock tunnels in hypervelocity test facilities. The primary concept and equations for high-enthalpy shock tunnels are presented first to demonstrate the unique advantage of shock tubes for aerodynamic ground-based testing. Then, the difficulties in simulating flight conditions in hypervelocity shock tunnels are identified, and discussed in detail to address critical issues underlying these difficulties. Theory and methods for developing detonation drivers are proposed, and relevant progress that has advanced the state of the art in large-scale hypersonic test facilities is presented with experimental verifications. Finally, tailored conditions for detonation-driven shock tunnels are described, laying a solid foundation to achieve long test duration. This interface-matching key issue encountered in developing shock tunnels has been investigated for decades, but not solved for detonation drivers in engineering applications.

关键词： hypervelocity shock tunnel detonation driver flight condition tailored condition test facilities

An FV-EE model to predict lean blowout limits for gas turbine combustors with different structures and sprays

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Chinese Journal of Aeronautics 2023年第5期36卷 145-156页

作者： Xiwei WANG Yong HUANG yunfeng liu Yufan WU Hongyan WANG Collaborative Innovation Center of Advanced Aero-Engine School of Energy and Power EngineeringBeihang UniversityBeijing 102206China National Key Laboratory of Science and Technology School of Energy and Power EngineeringBeihang UniversityBeijing 102206China

The occurrence of Lean Blowout(LBO)is a disadvantage that endangers a stable operation of gas turbines.A determination of LBO limits is essential in the design of gas turbine combustors.A semiempirical model is one of the most widely used methods to predict LBO *** the existing semiempirical models for predicting LBO limits,Lefebvre’s LBO model and the Flame Volume(FV)model are particularly suitable for gas turbine *** the basis of Lefebvre’s and FV models,the concept of effective evaporation efficiency is introduced in this paper,and a Flame Volume-Evaporation Efficiency(FV-EE)model is derived and *** experiments are carried out in a model combustor with 23 different structures and 10 different *** prediction uncertainty of the FV-EE model is less than±13%for all of these 33 structures and sprays,compared with±50%for the FV model and±60%for Lefebvre’s ***,the prediction uncertainty of the FV-EE model is also less than±13%for other combustors from available literature.

关键词： Atomization characteristic Evaporation efficiency Gas turbine combustors Lean blowout limit Semiempirical correlation

Criteria for hypersonic airbreathing propulsion and its experimental verification

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Chinese Journal of Aeronautics 2021年第3期34卷 94-104页

作者： Zonglin JIANG Zijian ZHANG yunfeng liu Chun WANG Changtong LUO State Key Laboratory of High Temperature Gas Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Hypersonic airbreathing propulsion is one of the top techniques for future aerospace flight, but there are still no practical engines after seventy years’ development. Two critical issues are identified to be the barriers for the ramjet-based engine that has been taken as the most potential concept of the hypersonic propulsion for decades. One issue is the upstream-traveling shock wave that develops from spontaneous waves resulting from continuous heat releases in combustors and can induce unsteady combustion that may lead to engine surging during scramjet engine *** other is the scramjet combustion mode that cannot satisfy thrust needs of hypersonic vehicles since its thermos-efficiency decreases as the flight Mach number increases. The two criteria are proposed for the ramjet-based hypersonic propulsion to identify combustion modes and avoid thermal choking. A standing oblique detonation ramjet(Sodramjet) engine concept is proposed based on the criteria by replacing diffusive combustion with an oblique detonation that is a unique pressure-gain phenomenon in nature. The Sodramjet engine model is developed with several flow control techniques, and tested successfully with the hypersonic flight-duplicated shock *** experimental data show that the Sodramjet engine model works steadily, and an oblique detonation can be made stationary in the engine combustor and is controllable. This research demonstrates the Sodramjet engine is a promising concept and can be operated stably with high thermal efficiency at hypersonic flow conditions.

关键词： Concept demonstration Hypersonic propulsion Oblique detonation engine Scramjet Shock wave Supersonic combustion Wind tunnel test

A theoretical method for solving shock relations coupled with chemical equilibrium and its applications

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Chinese Journal of Aeronautics 2022年第6期35卷 47-62页

作者： Zijian ZHANG Chihyung WEN Wenshuo ZHANG yunfeng liu Zonglin JIANG Department of Aeronautical and Aviation Engineering The Hong Kong Polytechnic UniversityHong KongChina Institute of Mechanics Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

In this study,a theoretical method is proposed to solve shock relations coupled with chemical *** only shock waves in dissociated flows but also detonation waves in combustive mixtures can be *** global iterative solving process is specially designed to mimic the physical and chemical process in reactive shock waves to ensure good stability and fast convergence in the proposed *** each global step,the single-variable equations of normal and oblique shock relations are derived and solved with the Newton iteration method to reduce the complexity of the problems,and the minimization of free energy method of NASA(National Aeronautics and Space Administration)is adopted to solve equilibrium *** is demonstrated that the convergent process is stable and very close to the real chemical-kinetic process,and high accuracy is achieved in the solutions of normal and oblique reactive shock ***,the proposed theoretical method has also been applied to many problems associated with reactive shocks,including the stability of oblique detonation wave,bow detonation over a sphere,and shock reflection in dissociated *** great importance of using chemical equilibrium to theoretically predict the theoretical range of the wedge angle for a standing oblique detonation wave(the standing window of the oblique detonation wave),the stand-off distance of bow detonation wave and the transition criterion of shock reflection in dissociated air with high accuracy have been addressed.

关键词： Chemical equilibrium Detonation Dissociated air Shock relation Theoretical solution

Nonlinear behavior of electrodynamic loudspeaker suspension at low frequencies

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1361-1365页

作者： FENG ZiXin SHEN Yong HENG Wei liu yunfeng Key Laboratory of Modern Acoustics (MoE) Institute of AcousticsNanjing University

The suspension of electrodynamic loudspeakers includes a surround of the cone and a spider, and it is characterized by the mechanic stiffness in the lumped-parameter model. By solving the nonlinear differential equation of motion which considers the nonlinearity of suspension at low frequencies numerically and measuring different kinds of surrounds and spiders, the nonlinear behavior of suspension is theoretically and experimentally studied. Since the nonlinear stiffness of spiders and surrounds can be measured and fitted respectively before assembled into loudspeakers, which spider works best with which surround is studied. The performance of loudspeakers such as harmonic distortion based on the nonlinear parameters can be predicted.

关键词： nonlinear stiffness surround spider

Aerodynamic force and moment measurement of 10°half-angle cone in JF12 shock tunnel

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Chinese Journal of Aeronautics 2017年第3期30卷 983-987页

作者： yunfeng liu Yunpeng WANG Chaokai YUAN Changtong LUO Zonglin JIANG State Key Laboratory of High Temperature Gets Dynamics Institute of MechanicsChinese Academy of SciencesBeijing 100190China

An aerodynamic force and moment measurement was conducted in JF12 long-testduration detonation-driven shock tunnel of Institute of Mechanics,Chinese Academy of *** test duration of JF12 is 100–130 *** nominal Mach number is 7.0 and the exit diameter of the contoured nozzle is 2.5 *** total enthalpy is 2.5 MJ/kg which duplicates the hypersonic flight conditions of Mach number 7.0 at 35 km *** test model is the standard aerodynamic force model of 10° half-angle sharp *** length of the test model is 1500 mm and the weight is 57 *** aerodynamic forces were measured with a six-component strain *** angles of attack were set to be à5°,0°,5°,10° and 14°,*** experimental results show that in the 100–130 ms test duration,the signals of strain balance have 3–4 complete vibration ***,the aerodynamic forces and moments can be obtained directly by averaging the signals of balance without acceleration *** force measurement error of repeatability of JF12 is less than 2%.The aerodynamic force coefficients of JF12 are in good agreement with those of conventional hypersonic wind *** this test model at Mach number 7.0 and total enthalpy of 2.5 MJ/kg,the real-gas effects on aerodynamic force characteristics are not very evident.

关键词： Aerodynamic force and moment measurement 10° half-angle cone model JF12 Real-gas effects Shock tunnel

Analysis and prediction of loudspeaker large-signal symptoms

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Science China(Physics,Mechanics & Astronomy) 2013年第7期56卷 1355-1360页

作者： HENG Wei SHEN Yong XIA Jie FENG ZiXin liu yunfeng Nanjing University Institute of Acoustics

Nonlinear lumped-parameter force factor Bl(x), stiffness Kms(x) and inductance Le(x) of electrodynamic loudspeakers change frequency responses and generate some nonlinear effects for large stimulus: harmonic and intermodulation distortion, DC component in diaphragm displacement, instability of vibration and jumping effects. By modeling the nonlinear system under large-signal conditions, relationship between the nonlinear parameters and large-signal behavior can be revealed and help to provide guidance to diagnose loudspeakers. Agreement between the measured and predicted responses of a real loudspeaker validates the modeling and enables new methods for loudspeaker diagnosis.

关键词： force factor stiffness inductance large-signal behavior

Noise reduction for temperature-sensitive paint measurement contaminated by strong background radiation in a high enthalpy hypersonic tunnel

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Acta Mechanica Sinica 2021年第1期37卷 20-26,I0002页

作者： Di Peng Xu liu Lingrui Jiao Ziyan Li Xin Wen Chaokai Yuan Guilai Han yunfeng liu Yingzheng liu Zonglin Jiang Gas Turbine Research Institute/School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China Institute of Mechanics Chinese Academy of SciencesBeijing100190China

The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent *** proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint(TSP)measurement in a hypersonic flow with Ma=6.5 and T_(0)=3525 *** TSP was applied on an inlet ramp model,and the images were taken by a high-speed camera at 2 kHz under a modulated *** strong background radiation led to a low signal-to-noise ratio and significant errors for the first half of the 130-ms test ***,three noise reduction methods were developed and evaluated based on temporal reconstruction,spatial reconstruction and robust principal component analysis(RPCA),*** RPCA method showed the best performance that successfully recovered high-quality TSP data for a majority of test duration(t≥40 ms).

关键词： Temperature-sensitive paint Time-resolved measurement Hypersonic flow Background radiation

RoTFL1c of Rosa multiflora has a dual-function in suppressing reproductive growth and promoting vegetative growth of Arabidopsis

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Science China(Life Sciences) 2018年第12期61卷 1599-1601页

作者： Fang Wang Lijuan Lian yunfeng liu Yuman Zhang Rongxiang Fang Qinglin liu Department of Ornamental Horticulture and Landscape Architecture China Agriculture UniversityBeijing 100193China State Key Laboratory of Plant Genomics Institute of MicrobiologyChinese Academy of SciencesBeijing 100101China

Dear Editor, TFL1homologues play a key role in the flowering habit of *** analyze the function of the newly isolated TFL1 gene of Rosa multiflora(Chen et al.,2013),named RoTFLlc,we performed overexpression analyses in Arabidopsis *** compared with empty vector control and wild type Arabidopsis plants,RoTFLlc overexpressing transgenic plants exhibited strong phenotypes such as a clustered habit,an increased number of rosette leaves, late flowering or failure to flower.

关键词： RoTFL1c Rosa multiflora