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1、Measurement Method and Technology in ThermophysicsAdvanced laser-based measurement techniques for multiphase flows 多相流先进激光测量技术Xuecheng Wu 吴学成 State Key Laboratory of Clean Energy Utilization, Department of Energy Engineering, Zhejiang University Tel.: 057187952805; MP: 13867104140(661140) Email: Mul
2、tiphase flows(多相流多相流) frequently found in the field of Energy and Environmental Engineering Gas particle flow in Circulating Fluidized Bed boiler gas particle flow in pipe (coal powder transportation) Gas particle flow jet (combustor) Spray Bubble in water 2015/9/232State Key Lab Clean Energy Utiliz
3、ation, Zhejiang Univ.Coal powder power plant2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.3Coal powder transportation in pipeCoal powder in combustorCoal powder flameGas solid flow in the furnaceFly ash flow in pipeBubble-water flow in water screen tubeSteam in heat transferSteam in
4、 turbineCFB(循环流化床循环流化床)2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.4Velocity distribution? particle size distribution? Concentration?Spray(喷雾喷雾)2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.5Velocity distribution? Droplet size? Concentration? Turbulence?Heat trans
5、fer2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.6Velocity distribution? Bubble size? Concentration?ConvectionMicro thermotubeGas turbine2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.7Why measure? Related to efficiency, pollutant emission and safety eg. size of coal
6、 powder (from coal mill) 2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.8Why measure? For industrial purpose Process in-situ monitoring and optimizing Investigate technique problems (know why) and find solutions For research on flow mechanism Obtain accurate flow parameters (Know exa
7、ctly what happen) Develop new techniques For theoretical fluid mechanism verify theoretical predictions develop, extend, refine models2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.92015/9/2310State Key Lab Clean Energy Utilization, Zhejiang Univ.VelocitySizeConcentrationHot-wire Ane
8、mometry Multiphase flows Gas-solid Gas-liquid Liquid-solid Gas-liquid-solid Laser Two Focus VelocimetryLaser Doppler Anemometry LDA/PDA/SDA/GDA Particle image velocimetry Stereoscopic PIV Micro-PIV Holographic PIV Capacitance transducers Ultrasonic wave sensors Radiometric sensors Electrostatic sens
9、ors Electdcal Low-Pressure Impactor(ELPI) Light extinction Technique Diffraction Technique (Malvern Sizer) Pitot-tubesVorticity Turbulence How to measure?NOTE: All the measurement techniques have their own advantages and disadvantages, as well as limitations in application. They can never be almight
10、y! Contents1. Laser Doppler Anemometry (including PDA) Measurement principle Measurement system (hardware and software) Typical applications 2. Particle Image Velocimetry (including SPIV and Micro PIV) Measurement principle Measurement system (hardware and software) Typical application 3. Holographi
11、c Particle Image Measurement System Measurement principle Technical characteristics and current developing status2015/9/2311State Key Lab Clean Energy Utilization, Zhejiang Univ.Contents1. Laser Doppler Anemometry (including PDA) Measurement principle Measurement system (hardware and software) Typic
12、al applications 2. Particle Image Velocimetry (including SPIV and Micro PIV) Measurement principle Measurement system (hardware and software) Typical application 3. Holographic Particle Image Measurement System Measurement principle Technical characteristics and current developing status2015/9/2312S
13、tate Key Lab Clean Energy Utilization, Zhejiang Univ.Characteristics of LDA Invented by Yeh and Cummins in 1964 Up to 3 velocity components measurements in Fluid Dynamics (gas, liquid, solid particle) Non-intrusive measurements (optical technique) Absolute measurement technique (no calibration requi
14、red) Very high accuracy (comparable to wavelength) Very high spatial resolution due to small measurement volume (xm-xxm) Tracer particles are required2015/9/2313State Key Lab Clean Energy Utilization, Zhejiang Univ.Doppler Effect(多普勒效应多普勒效应)Source moving toward observer Wavelength decreasing, Freque
15、ncy increasing Observer experiencing BLUE shiftSource moving away from observer Wavelength increasing, Frequency decreasing Observer experiencing RED shiftS P u A cu cu cucos1cos1cos12015/9/2314State Key Lab Clean Energy Utilization, Zhejiang Univ.General relativity theory by EinsteinProblem to record frequency shiftFrequency of laser light up to 1012 Hz, no detector available now can follow (response time of the fastest detector, PM, 10-8-10-9s)2015/9/23State Key Lab Clean Energy Utilization, Zhejiang Univ.15Relation between particle velocity and frequency difference S2 P u A
