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THERMOACOUSTICS David Wee Shuon Tzern Yousif Abdalla Abakr David Hann Paul Riley Optimisation of the Feedback Loop of the Thermoacoustic Travelling wave Engine
THERMOACOUSTICS
David Wee Shuon TzernYousif Abdalla Abakr
David HannPaul Riley
Optimisation of the Feedback Loop of the Thermoacoustic Travelling wave Engine
The Simplest form of a Travelling Wave Thermoacoustic Engine
Tuning Stub
Regenerator
Linear Alternator
Feed Back Loop
Limiting amplitude occurs when the amplification of the regenerator is equivalent to the power absorbed by the system
Total Power Absorbed = Power absorbed by Linear Alternator + System Losses
SCORE -StoveTM
Thermoacoustic Engine
An understanding of the Acoustic Transmission through bends is required in order to optimise the system
Efficiency
Compact
REQUIREMENT
INFLUENCING PARAMETER
Elbow Bends
MICROPHONE Decomposition Method
Decomposition Transfer Function Scattering Matrix Technique
MICROPHONE Experimental Setup
Opti
mum
Tra
velli
ng w
ave
Load
MICROPHONE Experimental SetupInvestigated Bends
Reynolds Number vs. Transmission Loss [%]
Legendr = hydraulic cross sectional radius (m)R = Radius of curvature of elbow(m)u = RMS particle velocity (ms-1)c = Speed of sound (ms-1)ω = angular frequency (s-1)ν = kinematic viscousity (m2s-1)
Legendr = hydraulic radius (m)R = radius of curvature of elbow(m)u = RMS particle velocity (ms-1)c = speed of sound (ms-1)ω = angular frequency (s-1)ρ = density (kg/m3)ν = kinematic viscousity (m2s-1)
Dean Number vs. Transmission Power Loss [%]
Linear Loss Region Non-Linear Loss Region
PIV Experimental Setup
PIV=Particle Image Velocimetry
PIV Experimental Setup
PIV Experimental Setup
Dean Number vs. Transmission Power Loss [%]
Linear Loss Region Non-Linear Loss Region
Dean Number vs. Transmission Power Loss [%]
At Higher operating Amplitude such as that of the Engine, Losses may go up to 10% or more
Linear Loss Region Non-Linear Loss Region
CONCLUSIONS•A monotonic relationship has been found between the Percentage Acoustic Transmission Loss and the Acoustic Dean Number. A critical Dean Number (≈1) above which the transmission losses increase significantly has been identified.
•Particle Image Velocimetry is being used to investigate the transition to nonlinearity by consideration of the flow field.
•Once verified this would prove an important breakthrough in the design of future feedback resonator loop for thermoacoustic systems by providing new information about the additional losses at the elbow bends.
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