validation of predicted path of thermally deflected ultrasonic waves (phd work on acoustic...
TRANSCRIPT
Validation of predicted path of thermally deflected ultrasonic waves
(phD work on acoustic thermometry in SFR)
Nicolas Massacret
(PhD Student )Directors: Joseph Moysan*, Marie-Aude Ploix*
CEA tutor: Jean-Philippe Jeannot**
* LMA-LCND -FRANCE-(Laboratory of Mechanics and Acoustics -
Non Destructive Characterization Laboratory)** CEA (Atomic Energy Commission)
Cadarache -FRANCE-DEN/DTN/STPA/LIET
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Outline
I- Context
II- Ultrasonic measurement advantages and issues
III- Acoustic model and implementation for simulation
IV- Experimental validation
V- Further experimentation
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French option for the 4th generation of nuclear reactor:
SFR project: Sodium-cooled Fast Reactor
In the past: Rapsodie – Phénix – Superphénix (French SFR)
In the future (plan to be built in 2023): ASTRID prototype
Need to develop several innovative and specific instrumentations
based on feedbacks:
For this kind of reactor,
To diversify and enhance current instrumentation,
For the liquid sodium, an opaque fluid banning optical technique.
I- Context
Rapsodie
Phénix
Superphénix
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ASTRID
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METHOD PATENTED IN 1989 BY UKAEA An Ultrasonic Technique for the Remote Measurement of Breeder Subassembly Outlet
Temperature, Instrumentation for the Supervision of Core Cooling in LMFBR's. [Macleod and al. 1989].
THERMOMETRY ISSUES USING THERMOCOUPLE:
(possible influence of neighboring subassemblies, long response time, important volume of instrumentation,…)
Thermometry at the subassemblies outlet:
turbulent area.
I- Context
Context: Thermometry of sodium at the subassemblies outlet :
≈350 thimbles, each one containing
2 thermocouples.
Acoustic instrumentation advantages :
Opacity of sodium is not an issue any more.
It is non-invasive: Acoustic transducer can be away from the measured area.
There is no more thermal inertia of thimble containing thermocouples : so response-time is improved for thermometry.
It is possible to realize a measurement in different areas with only one transducer.
Temperature: Inhomogeneities of sodium temperature
above the core (ΔTmax=50°C)
Speed flow field at the subassemblies outlet: Turbulent flow (Re=60 000),
High speed flow (about. 4 m.s-1) ,Important speed gradient (1.5m.s-1.cm-1).
Deflection and diffusion of ultrasonic waves
However, ultrasonic propagation depends on:
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II- Ultrasonic measurement advantages and issues
Objective : Define an appropriate model for ultrasonic propagation in turbulent fluid, dealing with influence of temperature and flow speed.
Considering the thermo-hydraulics characteristics of the medium (characteristic length of the inhomogeneities, Mach number, …) and thanks to the application of the frozen fluid hypothesis:
Model using the acoustic ray theory and a refractive index based on temperature and flow speed field.
Numerical simulation of transit-time ultrasonic flowmeters: uncertainties due to flow profile and fluid.
[B. Iooss and al. 2000]
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II- Acoustic model and implementation
Numerical Calculation
Acoustic ray equation:
Prediction of ray deflections and delays
Gaussian beam approach
(in development)
Thermo-hydraulics data(from experiment,
simulation, …)
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II- Acoustic model and implementation
Where :r(x,z) is the 2D ray position vector,s is the arc length,t(r) is the unit vector tangent to the ray,(r) is the travel time of the wave on the ray,c(r) is the acoustic celerity,v(r) the fluid velocity vector,S = t/(c+ t.v) is the acoustic slowness vector,= 1-v.S
Principle of the experiment UPSilon (Ultrasonic Path in Silicone oil):
Creation of thermal inhomogeneities in fluid
Propagation of ultrasonic waves across thermal
inhomogeneities
Observation of delays and deflections of ultrasonic waves
Comparison with acoustic ray simulation
Fluid properties : Silicone Oil Very viscous fluid (viscosity : 10 000 cSt) to
avoid convection movement. High dependence of ultrasonic celerity with
the temperature in this medium. As the sodium (and unlike water), this
dependence is linear and the celerity decreases with the temperature.
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III- Experimental validation
Silicon oil:
Sodium:
Experimental setup:
Vertical cross-section views
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III- Experimental validation
Y
XX
Y
2.25 MHz 2.25 MHz
Acoustic scan along 5 cm.Step : 0.2 mm.Temperature : 20.5 °C.Ultrasonic celerity ≈ 1000 m.s-1.
Experimental result: « B-Scan » without heating.
Planar wavefront. Weak influence of wires.
Amplitude (Volt)
III- Experimental validation
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Bscan: local extrema
Experimental result: « B-Scan » with heating.
Delayed wavefront Deflected wavefront Non disturbed wavefront
Amplitude (Volt)
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III- Experimental validation
Thermal map for simulation
X
Y
Simulation: definition of the UPSilon thermal map
Temperature (°C)
Strioscopic view of the experimental thermal gradient
Determination of thermal gradient area with strioscopy
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III- Experimental validation
Measurement of the thermal gradient amplitude
with 4 thermocouples at different depths
Simulation : Propagation of acoustic rays
Temperature (°C)
Propagation of 52 acoustic rays through the thermal inhomogeneities
Selection of one time => Determination of the corresponding wavefront
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III- Experimental validation
Delayed wavefront
Deflected wavefrontNon disturbed wavefront
Comparison between experiment and simulation
For delayed waves:Relative difference < 1%Very good agreement.
For delayed and deflected waves:Relative difference < 3%
Good agreement
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III- Experimental validation
Comparison of experimental and numerical wavefront
● experimental wavefront+ numerical wavefront
Rescaling of data.
Effect of speed flow inhomogeneities on acoustic waves propagation.
Coming experimentation for validation: IKHAR (in June 2013).
IKHAR: Instabilities of Kelvin-Helmholtz for Acoustic Research
Kelvin-Helmholtz Instabilities:- well-known- periodic
Ultrasonic transducer
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IV- Further works
Overview of IKHAR
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IV- Conclusion and perspectives
Simulation of acoustic rays through thermal inhomogeneities.
Validation with experiment UPSiIon (in silicon oil at 20-30°C).
Simulation of acoustic rays through speed flow inhomogeneities.
Coming experiment: IKHAR.
Full term perspectives:
Utilization of this simulation code as a tool to define possibilities and limits of acoustic technique in reactor.
Simulation code will allow us to:
Estimate influence of thermal inhomogeneities and speed flows on ultrasonic propagation,
Design optimal transducers for applications in reactor,
Help to analyze different configurations of acoustic instrumentation.
Optimize the signal processing methods.
