with Heat Exchanger Naseh Hosseini The 3 rd TANGO Meeting and - PowerPoint PPT Presentation

Numerical and Experimental Study of Thermoacoustics of Domestic Burner with Heat Exchanger Naseh Hosseini The 3 rd TANGO Meeting and Workshop KTH Royal Institute of Technology, Stockholm, Sweden 19-23 May, 2014

Introduction - Started PhD on August 15, 2013 • Eindhoven University of Technology (TU/e), Eindhoven, the Netherlands - Started in TANGO on November 1, 2013 • Bekaert Combustion Technology B.V. (BCT), Assen, the Netherlands • R&D researcher thermoacoustics - Task 3.5 – Numerical and experimental study of domestic burner with heat exchanger 2

My Research - Previous Works • Development of a model for the interaction between acoustic waves and different types of premixed conical flames • Acoustic response of the flame in open environment For industrial burners with large perforations (2 mm diameter) • 3

My Research - Interactions of burner with heat exchanger • Effects on flame shape (hydrodynamic or impingement) • Changes in the temperature of different surfaces • Can the heat exchanger itself have TF and cause time delay? Structures and performances of laminar impinging multiple premixed LPG – air flames U. Makmoola et al. (2013) 4

Outline - Inclusion of heat exchanger and investigation of its hydrodynamic and thermoacoustic effects - Solving the problems associated with modeling combustion in small perforations (around 0.8mm) - More sophisticated modeling of thermoacoustics and terminations methods (e.g. DNS of anechoic terminations) 5

Numerical - Geometrical challenges in modeling 2D axisymmetric 2D plane Full 3D 6

Numerical - Computational domain • Slit burner, plane 2D • One tube per one row of slits • Based on future experiments 7

Numerical - Computational grid 164689 cells of 20  m size • • Proper size achieved through pseudo-1D simulations 8

Numerical - Model specifications – combustion • Laminar premixed methane-air at 0.8 equivalence ratio Time step size 10  s • • Single step modified chemistry for proper flame speed calculation        • The global reaction CH 2 O 3.76 N CO 2 H O 7.52 N 4 2 2 2 2 2    E RT o k AT e r r Reaction rate r r A r = 2.29  10 19 (consistent units), pre-exponential factor o  r = 2.8 and 1.2 (dimensionless) for CH 4 and O 2 , temperature exponent o E r = 1.38  10 8 (J/kmol), activation energy o o R = 8314.34 (J/kmol-K), universal gas constant 9

Numerical - Model specifications – transfer function • Definition    q f q    TF f    u f u • Excitation: step profile for velocity with 5% increase at the domain inlet • For TF calculations, velocity above burner deck was considered • Response: sum of heat of reaction in the whole domain 10

Numerical – Pseudo-1D - Finding suitable flame speed through pseudo-1D simulations 0.02  35mm computational domain • • Same boundary conditions as 2D • Defining a proper inlet velocity • Observing flame (maximum reaction rate) movement – must remain constant time 11

Numerical – Pseudo-1D - Finding suitable flame speed through pseudo-1D simulations • Flame speed dependency to grid size was checked • Coarse grid fluctuations due to temporal and special resolution mismatch Cell size 20  m 12

Numerical – Pseudo-1D - Finding suitable flame speed through pseudo-1D simulations • Equivalence ratio sensitivity 40 This Study 35 Lange (1992) 30 Dyakov (2001) Kishore (2008) 25 Sl (cm/s) 20 15 10 5 0 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 Equivalence Ratio 13

Numerical – Pseudo-1D - Finding suitable flame speed through pseudo-1D simulations • Unburned temperature sensitivity 90 80 This Study Sharma (1981) 70 Brown (2003) 60 Sl (cm/s) 50 40 30 20 10 0 150 200 250 300 350 400 450 500 550 Unburnt Temperature (K) 14

Numerical – 2D - Case studies Inlet Velocity (cm/s) 25 50 Heat Exchanger Distance (mm) Burner Deck – 5 Hex05-V25 Hex05-V50 10 Hex10-V25 Hex10-V50 15 Hex15-V25 Hex15-V50 N/A NoHex-V25 NoHex-V50 15

Numerical – 2D - Reaction rate (kmol/m 3 s) - V = 25cm/s 16

Numerical – 2D - Temperature (K) - V = 25cm/s 17

Numerical – 2D - Temperature (K) - V = 50cm/s 18

Numerical – 2D - Reaction rate (kmol/m 3 s) - V = 50cm/s 19

Numerical – 2D - Flow through flame front - Wake behind the tube cylinder 20

Numerical – 2D - Periodic step (square) - Slight increase just before the decrease 1.06 1.05 Normalized Heat Release 1.04 1.03 1.02 1.01 1.00 0.99 0 5 10 15 20 25 30 35 40 Time (ms) 21

Numerical – TF – V25-QReac NoHex Hex15 Hex10 Hex05 NoHex Hex15 Hex10 Hex05 1.06 0.0 1.05 Heat Release Rate (kW) -0.5 Phase/  (rad) 1.04 -1.0 1.03 -1.5 1.02 -2.0 1.01 -2.5 1.00 -3.0 0.99 0 100 200 300 400 500 600 700 800 900 1000 0 5 10 15 20 25 30 35 40 Frequency (Hz) Flow Time (ms) NoHex Hex15 Hex10 Hex05 NoHex Hex15 Hex10 Hex05 1.2 1 1.0 0.1 0.8 Gain Gain 0.6 0.01 0.4 0.001 0.2 0.0 0.0001 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 Frequency (Hz) Frequency (Hz) 22  

Numerical – TF – V25-QHex Hex15 Hex10 Hex05 Hex15 Hex10 Hex05 1.04 0.0 Normalized Heat Exchanger Heat Flux 1.04 -0.2 1.03 Normalized Gain Phase/  (rad) 1.03 -0.4 1.02 -0.6 1.02 1.01 -0.8 1.01 1.00 -1.0 0 100 200 300 400 500 600 700 800 900 1000 1.00 0 5 10 15 20 25 30 35 40 Frequency (Hz) Time (ms) Hex15 Hex10 Hex05 Hex15 Hex10 Hex05 1 1.0 0.8 Gain 0.6 Gain 0.1 0.4 0.2 0.01 0.0 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 Frequency (Hz) Frequency (Hz) 23  

Numerical – TF – V50-QReac NoHex Hex15 Hex10 Hex05 NoHex Hex15 Hex10 Hex05 1.07 0.0 1.06 Normalized Heat Release -1.0 1.05 Phase/  (rad) -2.0 1.04 -3.0 1.03 -4.0 1.02 -5.0 1.01 -6.0 1.00 0.99 -7.0 0 5 10 15 20 25 30 35 40 0 100 200 300 400 500 600 700 800 900 1000 Time (ms) Frequency (Hz) NoHex Hex15 Hex10 Hex05 NoHex Hex15 Hex10 Hex05 1.6 1 1.4 1.2 1.0 Gain Gain 0.1 0.8 0.6 0.01 0.4 0.2 0.0 0.001 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 Frequency (Hz) Frequency (Hz) 24  

Numerical – TF – V50-QHex Hex15 Hex10 Hex05 Hex15 Hex10 Hex05 1.04 0.0 Normalized Heat Exchanger Heat Flux 1.03 -1.0 1.02 Phase/  (rad) 1.01 -2.0 1.00 -3.0 0.99 -4.0 0.98 0.97 -5.0 0.96 0 100 200 300 400 500 600 700 800 900 1000 0 5 10 15 20 25 30 35 40 Frequency (Hz) Time (ms) Hex15 Hex10 Hex05 Hex15 Hex10 Hex05 1.2 1 1.0 0.8 Gain Gain 0.6 0.1 0.4 0.2 0.0 0.01 0 100 200 300 400 500 600 700 800 900 1000 0 100 200 300 400 500 600 700 800 900 1000 Frequency (Hz) Frequency (Hz) 25  

Numerical – TF – Gains at Zero Frequency 1.4 - QReac Calculated via FFT 1.2 all Hex & and steady state NoHex 1 1− 𝑟2 TF Calculated Gain at 0Hz 𝑟1 values 0.8 1− 𝑣2 𝑣1 QHex QHex 0.6 H10V50 H05V25 H15V50 H10V25 0.4 H15V25 0.2 0 -0.2 QHex -0.4 H05V50 -0.6 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Physical Gain at 0Hz 26

Experimental - Rigidity issues in small dimensions - Portability Version 1.0 Version 2.0 Version 3.0 27 27

Future Works - Further investigations on the available results (better boundary conditions, transfer matrix, etc.) - Starting the experimental part and making required modifications - Starting modeling of smaller perforations 28 28

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