2015 Vol. 29, No. 4

Display Method:
Research progress on ignition and flame propagation in highly turbulent flows
Li Minglei, Wu Ning, Hou Lingyun, Ren Zhuyin
2015, (4): 1-11. doi: 10.11729/syltlx20150060
Abstract(155) PDF(11)
Abstract:
The ignition and flame propagation of premixed mixture are commonly recognized as the key processes for reliable engine operations.Spark ignition,the most common ignition mode in engine combustion,effectively converts the electrical energy into a small heat deposit with the formation of radicals.The ignition process is constituted of two main phases,that are the ignition kernel formation and the kernel propagation.The forced ignition phenomena ob-served are highly transient in nature with various factors influencing the development of spark kernels from the moment of spark deposit until complete flame establishment.The most favora-ble ignition spots for sparking in engine combustors are influenced not just by the local equiva-lence ratio,but also by the time history of the velocity fluctuations,which would transport the flame kernel away from the ignition spot.To date,some fundamental physico-chemical processes of the ignition process are still unclear in highly turbulent flows which are commonly found under engine operating conditions.The problems urgent to be studied include the turbulence promo-tion/suppression mechanism for the ignition process,the effect of turbulence on flame propaga-tion and the scaling law for turbulent flame speed over a wide range of pressures and turbulent in-tensity,the effect of heat release and flame instability on turbulent fluctuating velocity (e.g., the flame generated turbulence)and flame propagation,the transition from a laminar flame to a turbulent flame resulting from propagation acceleration due to flame instability,and the effect of combustion process on the transport of reactive scalars.In this paper,recent theoretical,experi-mental and numerical studies of the ignition and flame propagation in turbulent flows are re-viewed together with discussions on the spark ignition in turbulent nonpremixed flames and the challenges for high-fidelity simulations of the ignition process.The needs of experimental techniques and turbulent combustion modelling for the study of the ignition process in highly tur-bulent flows especially under engine operating condition are also discussed.
Progress of continuously rotating detonation engine research
Wang Jianping, Zhou Rui, Wu Dan
2015, (4): 12-25. doi: 10.11729/syltlx20150048
Abstract(256) PDF(24)
Abstract:
Continuously Rotating Detonation Engine (CRDE)is one kind of new-concept deto-nation-based engines.It has several advantages,including one-initiation,fast combustion veloci-ty,high thermal efficiency and simple structure.Due to these characteristics,it is expected to bring revolutionary advancements to aerospace propulsion systems and has already drawn much attention throughout the world.In this paper,an overall review of the development of CRDE is given from several aspects:basic concepts,applications,experimental studies,numerical simula-tions,and so on.Representative results and outstanding contributions are summarized,and the unresolved issues for further engineering applications of CRDE are discussed.
Off-design performance of osculating curved cone inlet
Wu Yingchuan, Yao Lei, Yang Dawei, Wang Tiejun, He Yuanyuan
2015, (4): 26-31. doi: 10.11729/syltlx20150072
Abstract(189) PDF(7)
Abstract:
It is difficult to maintain high performance over a wide range of Mach numbers for a hypersonic inlet.An osculating curved cone waverider inlet is designed and the design point of the inlet is optimized to obtain high performance with Mach numbers ranging from 4.5 to 6.From the numerical simulation and experiment results,it is found that the inlet mass flow capture ratio and the engine thrust can be efficiently improved by adjusting shock on lip Mach Number from 6 to 5.5,while the inlet can be guaranteed to be self-started by optimizing the inlet sweepback an-gle of the sidewalls.The experiment shows that the designed scramjet engine performance is im-proved under off-design conditions.
Study of the correlation between the measured wind field and wind pressure on a high-rise building
Li Zhengnong, Li Hongyi, Luo Diefeng, Pan Yueyue
2015, (4): 32-40. doi: 10.11729/syltlx20140125
Abstract(127) PDF(4)
Abstract:
Based on the field measurement and wind pressure measurement on the surface of a super-tall building on the coast of the Xiamen city during the passage of typhoon Usagi in Sep-tember 2013,the wind field was measured by a propeller anemometer placed at the roof of the test building,and the wind pressure was measured by 18 pressure sensors stuck on the glass wall on the refuge floor at the height of about 70m.This paper presents selected measurement data (such as the mean wind direction,mean wind speed,turbulence intensity,mean pressure,and soon).Through in-depth analysis it is shown that the 10min wind direction and wind speed are relatively stable,the filed turbulence intensity of typhoon Usagi is normal,and with the increase of wind velocity the turbulence intersity varies steadily.The wind pressure coefficient shows the following characteristics:the wind pressure coefficient of each measuring point on the windward side shows a relatively large value in the middlepoint and smaller values from the middle to each end point,but the gap is not great.Meanwhile,the correlation between the measured wind field (the mean and RMS wind velocity,the turbulence intensity)and wind pressure (mean and RMS wind pressure)on the windward side is analyzed from two aspects.One is to investigate the corre-lation in 8 selected different time intervals:1s,2s,3s,10s,30s,1min,3min,10min,and the results of the research clearly reveal that:when the average time interval is taken as 3s,there is a relatively high correlation between the measured wind field and wind pressure.The other one is to evaluate the correlation under different wind directions:30.8°,33.2°,36.7°,39.4°,42.1°, 45.3°,47.6°,49.5°,and as the wind direction is roughly perpendicular to the windward wall (when the wind direction is 39.4°),the correlation between the wind field and the wind pressure is relatively large.
Experimental research of electroosmotic flow in rough microchannels based on current-monitoring method
Xu Tao, Yang Dayong
2015, (4): 41-46. doi: 10.11729/syltlx20140112
Abstract(177) PDF(2)
Abstract:
Two kinds of PMMA microfluidic chips were manufactured,and the surface param-eters of the microchannels were tested.A electroosmotic flow (EOF)experimental system with the microfluidic chip was designed based on the current-monitoring method.Firstly,the EOF ve-locity in smooth microchannels was measured,which validated the feasibility of the experimental method.The method can predict the microchannel surface potential.Secondly,the EOF velocity in rough microchannels was measured.Finally,the influence of the electric strength and ionic concentration on the EOF in smooth and rough microchannels was analyzed .The results show that:(1 )The EOF velocity in smooth and rough microchannels is proportional to the electric strength;the EOF velocity decreases with the increase of ionic concentration both in smooth and rough microchannels.(2)The EOF velocity in rough microchannels is significantly decreased. The velocity is decreased by 23%,when the relative roughness is 5%.(3)The gap between the EOF velocities in smooth and rough microchannels increases with the increase of electric strength or solution concentration.The experimental method possesses the advantage of being intuitive, convenient and low cost.
Experimental study of turbulent Rayleigh-Bénard convection under non-uniform heating boundary conditions
Zhan Jinghua, Zhou Quan
2015, (4): 47-51,57. doi: 10.11729/syltlx20140141
Abstract(136) PDF(4)
Abstract:
We present an experimental investigation of heat transport by turbulent Rayleigh-Bénard (RB)convection under non-uniform heating boundary conditions.During the measure-ments,the Rayleigh number Ra varies from 9×10 8 to 7×10 9 and the Prandtl number Pr is fixed at Pr=5.4.By adjusting the spatial distribution of the heating power in the lower plate,we ob-served an enhancement in the Nusselt number Nu by 13%.Therefore,our results reveal that the non-uniform heating can enhance the global heat transport efficiency of the system.
Flutter stability selection study of a long-span steel truss suspension bridge with a combined deck plate
Xu Aijun, Wang Kai, Li Mingshui, Liao Haili
2015, (4): 52-57. doi: 10.11729/syltlx20150051
Abstract(159) PDF(4)
Abstract:
Comparing with the traditional beam-plate separation system,the aerodynamic per-formance of the steel truss with a combined deck plate is significantly different.By taking a sus-pension bridge with a combined deck plate as the engineering background,the aerodynamic per-formance of the bridge and aerodynamic optimizations of the deck configuration are studied in de-tail using the section model testing technique.To improve the flutter stability of the bridge,a se-ries of wind tunnel tests are conducted to investigate the effects of the upper central stabilized plate,the lower central stabilized plate and the horizontal stabilized plate on the flutter perform-ance of the main girder.According to the test results,the optimal aerodynamic measure is pro-posed to meet the requirements of the bridge wind resistance with consideration of structural safety,economy and aesthetic.The result can be taken as a reference for the design of aerody-namic performance of similar steel truss girder suspension bridges.
Low turbulence intensity and spectrum measurement research in aeroacoustic wind tunnel
Zhu Bo, Tang Gengsheng
2015, (4): 58-64. doi: 10.11729/syltlx20140118
Abstract(143) PDF(10)
Abstract:
The 5.5m×4m low turbulence aeroacoustic wind tunnel is a low speed single-re-turn wind tunnel,capable of performing aeroacoustic,low turbulence and general low speed tests.The flow of this tunnel presents the important quality of low turbulence intensity,which needs to be measured accurately.The band pass filter and signal noise separation are the two main methods to process the low turbulence intensity data.However,the parameters of the two methods are different,and thus there is no direct comparison between their results.In this paper the low turbulence intensity of the flow field is measured in the closed test section of the 5.5m× 4m low turbulence aeroacoustic wind tunnel with the hot wire anemometry.A 0.5Hz high pass inertia attenuation filter is adopted to process the data according to the noise analysis,and the re-sults are compared with other two methods,that the 0.5Hz~5kHz band pass filter and the sig-nal noise separation.Noises in the flow field fluctuation are analyzed based on the power spec-trum and the Strouhal numbers.The electromagnetic noise and support disturbing noise are found in spectrum domain of 40Hz~10kHz.Using a 0.5Hz high pass inertia attenuation filter, the flow field turbulence intensity is measured and found to be less than 0.05% at the speed of 30~100m/s.Experimental results show that,the high pass inertia attenuation filter method can be used to control the disturbance to the results induced by noises,which is a practical method for processing the low turbulence intensity digital signal.
Application of quantitative schlieren method in flame temperature measurement
Meng Sheng, Yang Zangjian, Wang Mingxiao, Shen Zhongliang, Deng Kai, Zhong Yingjie
2015, (4): 65-69. doi: 10.11729/syltlx20140117
Abstract(253) PDF(30)
Abstract:
The frame temperature is measured using ‘Z’type schlieren by standard photomet-ric method.The relationship between the grayscale value of flame schlieren image and the deflec-tion angle is established through a calibration lens.The refraction index is obtained by using axi-symmetric assumption.Then by using the Gladstone-Dale relationship and the ideal gas law,the flame temperature is obtained.The comparison of involved inversion algorithms shows that,the direct integral method and the Abel inversion method can both achieve the least error,however, the Radon inversion strongly depends on the filter function and the algebraic reconstruction de-pends on the numbers of discrete points.The temperature reconstructed by the quantitative schlieren technique is compared to thermocouple measurements.The results prove the validation of this quantitative technique.
Low speed and turbulence measurements based on composite hot-film technology
Song Weiwei, Han Jie, Chen Tianyi, Zhou Ping
2015, (4): 70-74. doi: 10.11729/syltlx20140134
Abstract(100) PDF(7)
Abstract:
The paper studies the composite hot-film test method used to measure the air veloc-ity and turbulence at low speed.The output sensitivity of the air velocity measurement is general-ly low in wind tunnel tests.In order to improve the sensitivity of the hot-film sensitive probe when the velocity is very slow,the temperature difference between the hot-film and the airflow is enhanced.The velocity and turbulence of the low speed airflow can be accurately measured even when it is under 2m/s.In order to correct the output of the hot-film sensitive probe influenced by the gas temperature,the methods of temperature compensation and compensation circuit are studied.A special circuit is designed to obtain the accurate control of temperature difference.By matching the structune,size and components of the hot film reasonably,the hot film sensitive probe is miniaturized.Using the MEMS technology,good frequency response of the probe is achieved by reducing the size of the thermal resistances and measurement resistances.Test results show that the composite hot-film sensitive probe can satisfy the requirement of the low speed and turbulence measurement.
Research on flutter test technique in hypersonic wind tunnel
Ji Chen, Li Feng, Liu Ziqiang
2015, (4): 75-80. doi: 10.11729/syltlx20150005
Abstract(187) PDF(8)
Abstract:
In order to conduct flutter test research in hypersonic wind tunnels,a hypersonic wind tunnel flutter test apparatus and a model protection device in the form of protective cover were designed.Wind tunnel tests show that the apparatus can be used to carry out the hypersonic wind tunnel flutter test research and to prevent the test model from being interfered by the wind tunnel vibration.The protection device can work in high dynamic pressure situations and protect the model effectively.The results also validate the two ways of driving the wind tunnel with the dynamic pressure changing step by step or continuously at a fixed Mach number.In order to veri-fy the hypersonic wind tunnel flutter testing technique,flat wings flutter tests were conducted on in the hypersonic wind tunnel at Mach 5.0 and 6.0.The stochastic subspace method was used to identify structural model parameters,and the Zimmerman-Weissenburger method was used for predicting the critical flutter dynamic pressure.The results of this prediction were 12.7% larger than the calculated values using the piston theory.
Testing of combustor chamber material in arc jet flow mixing with transverse injected water
Tu Jianqiang, Chen Lianzhong, Xu Kao
2015, (4): 81-87. doi: 10.11729/syltlx20140121
Abstract(141) PDF(2)
Abstract:
In the combustor inner flow thermal environment,the oxidation reaction of com-bustor inner surface thermal protection material,such as C/SiC and Ultra High Temperature Ce-ramic (UHTC),is more rapid in water vapor as a product of combustion than in oxygen.The water vapor also reacts with silica glass,formed in the combustor inner surface to prevent oxida-tion,to destroy the protective layer by volatilization.It has a serious impact on the combustor thermal protection performance.In the paper,the combustor inner flow thermal environment has been simulated by plasma arc heating supersonic rectangular Turbulent Flow Duct (TFD).At the same time,the ambient-temperature water,whose mass flow rate is 4%~5% of the flow, has been transversely injected into the mixing chamber,located at the end of the arc heater and before the nozzle,in order to mix with the high-temperature air and simulate the component, mass flow rate and temperature of water vapor coming from hydrocarbon combustion.The mix-ing quality between the water and the high-temperature air in the mixing chamber has been ana-lyzed by numerical calculation.The total enthalpy calculation method of the mixing gas has also been discussed.
Investigation on dynamic simulation technology of internal weapons bay’s doors opening and closing
Wu Jifei, Xu Laiwu, Guo Hongtao, Tang Linwei, Gao Peng
2015, (4): 88-94. doi: 10.11729/syltlx20140131
Abstract(254) PDF(17)
Abstract:
An investigation on the dynamic simulation technology of internal weapons bay’s doors opening and closing was conducted in a high speed wind tunnel.The ratio of internal weap-ons bay length to depth is 6.5.The doors opening and closing dynamic test simulation criteria is analyzed in depth in this paper.The cylinder driven and motor driven institutions were developed to realize the motion of internal weapons bay’s doors.Measurement techniques and data process-ing methods of this dynamic test were investigated,so that the motion characteristics of the doors and the dynamic loads of internal weapons bay system can be recorded and analyzed well and tru-ly.This paper presents the test results for Mach number of 0.6 and the Reynolds number of 1.28 × 10 7/m.The results show that the designs of the motion institutions are reasonable and both the cylinder driven and the motor driven institutions can achieve rapid opening and closing motion of the doors.The motion velocity can be adjusted over a large scale by using motor driven devices.The measurement system is reliable which can obtain dynamic loads and motion characteristics of the doors accurately under subsonic,transonic and supersonic conditions.Data processing method is feasible,the energy distribution characteristics and spectral characteristics were obtained by using this method and the flow field and the bay doors dynamic load characteristics were studied.
Development of measurement and control system for CTS in 2m×2m supersonic wind tunnel
Li Ping, Huang Xuhui, Zhou Run, Zhang Zhengyu, Gao Rongzhao
2015, (4): 95-100. doi: 10.11729/syltlx20140082
Abstract(124) PDF(10)
Abstract:
In order to meet the requirement of Captive Trajectory Simulation tests in 2m-scale supersonic wind tunnel,the CTS facility and the corresponding measurement and control system are developed in the 2m×2m supersonic wind tunnel.In order to realize the closed-loop velocity control mode,a multi-layer distributed structure with a centralized control test technique is selected for the construction of the measurement and control system which must meet the high demands of real-time processing and information interaction tasks.The system consists of three subsystems,namely,the signal measurement and motion equation solver subsystem,the 6-DOF motion control subsystem ,and the safety supervising subsystem.The softwares of monitoring and management,data acquisition and trajectory generation,and security monitoring are devel-oped by LabVIEW.The motion control execution software is developed by IndraWorks.The information interaction among subsystems is implemented through TCP/IP,PSP and Profibus DP.The key technical problems such as shock resistance and velocity control are solved.Static accuracy of the 6-DOF rig is measured by T3-40 laser tracker which shows that the positioning accuracy of linear displacement X ,Y and Z achieves 0.021mm,0.046mm and 0.094mm respec-tively,the positioning accuracy of angular displacement α,β and γ achieves 0.05°,0.047° and 0.022°,respectively.The accuracy is better than that of design index(±0.1mm,±0.1mm, ±0.1mm,0.05°,0.05°,0.05°).The debugging and wind tunnel tests show that the system is sta-ble,reliable,and easy to use and maintain;the test results are reasonable,and the data obtained are reliable.