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Thermal characterisation of an ethanol flashing jet using differential infrared thermography

Eucass 2011, St Petersburg. Thermal characterisation of an ethanol flashing jet using differential infrared thermography.

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Thermal characterisation of an ethanol flashing jet using differential infrared thermography

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  1. Eucass 2011, St Petersburg Thermal characterisation of an ethanol flashing jet using differential infraredthermography H. Kamoun, G. Lamanna, B. WeigandInstitute of Aerospace Thermodynamics, Universität Stuttgart 70569 Stuttgart Germany J. SteelantESTEC-ESA, 2200 AG Noordwijk, The Netherlands

  2. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  3. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  4. Motivation & Objectives • Flashing: Sudden exposure of a superheated pressurized liquid to a low pressure environment  Fast phase transition • Relevant in many technical application • Accidental release of flammable and toxic pressure-liquefied gases in nuclear and chemical industry. • Benefit in propulsion system  enhanced atomisation P Liquid Pinj Vapor Psat(Tinj) Rp P∞ ΔT Tsat(P∞) Tinj T

  5. Motivation & Objectives • Flash-atomisation/vaporisation model  Temperature data for validation • Non-intrusive methods are needed • New method  Differential Infrared Thermography (DIT)

  6. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  7. Differential Infrared Thermography • Problem: • Spray emissivity: ε unknown • For a liquid or a gas ε = f (T, λ, density) DIT

  8. Differential Thermography - TBack = 286 K TBack = 366 K Liquid: ethanol, Tinj = 389K, pam = 0.2bar, pinj = 10bar

  9. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  10. Experimental Setup High-pressure liquid supply system Liquid tank Vacuum chamber Vacuum Pump Optical setup

  11. Experimental Setup • Heated modified diesel injector with D=150 μm andL/D= 6.6 • Short injection and transient times → Constant backpressure • Constant injection conditions (i.e. pressure & temperature) • Reproducible test conditions Courtesy of Bosch GmbH

  12. Experimental Setup Heated background 303 K<TBack <389 K Cooled background 280 K<TBack <290 K

  13. Differential Infrared Thermography

  14. IR Kamera • Resolution: 640x512 pixel • Detector: InSb • Detector cooling: Stirling Cooler • Spectral range: 1.5 - 5µm • Integrationmode: Snapshot • Calibration range: 5°C – 300°C FLIR Orion SC7000 Series

  15. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  16. Uncertainty analysis • The choice of the background temperatures • If Ispray < IBackground1,2and for the spray dilute region (εspray<<1) A calculation of the spray temperature is impossible Key point: the selection of the background temperature should enhance the contrast between spray and surroundings

  17. Uncertainty analysis • The sensitivity to measurement errors in e.g. the temperature recorded by the infrared camera TCam1 • For a given TsprayandTback1,2 ,the temperature recorded by the camera and the spray temperature error can be computed as a function of εspray

  18. Uncertainty analysis Liquid: ethanol, Tinj = 389K, pam = 0.2bar, pinj = 10bar The best results are obtained when the spray temperature distribution is intermediate between the two background values

  19. Uncertainty analysis Tback1=337K, Tback1=366 K Max error: 25K Tback1=286 K, Tback1=366 K Max error: 4K

  20. Uncertainty analysis (Outlook) • Influence of multiple scattering inside the spray: • Neglecting infrared scattering may lead to an overestimation of the emitted spray radiation • Further investigation are needed to evaluate this effect on the temperature results • Comparison of the temperature results with Global Rainbow Thermometry data to validate the assumption made here.

  21. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  22. Results (Validation) • the window does not affect the temperature results • good agreement with the temperature measured by the thermocouples • Despite the good agreement a validation of the DIT can be accomplished only upon • comparison with other non-intrusive thermographic technique (e.g. GRT) • estimation of infrared scattering from a cloud of finely atomised droplets. Liquid: ethanol, Tinj = 403K, pam = 1 bar, pinj = 10bar

  23. Results r x Example of flash a atomising spray. Liquid: Ethanol, Tinj = 389 K, pam = 0.2 bar, p inj = 10 bar • Near the nozzle exit: narrow temperature profile • Downstream: flatter temperature profile • Rapidly decay of the temperature downstream the nozzle

  24. Results (Axial Profile) Liquid: ethanol, Tinj = 342 K, pinj = 10bar • Superheating Rp↑ → Cooling rate ↑

  25. Contents • Motivation & Objectives • Differential Infrared Thermography • Experimental Setup • Uncertainty analysis • Results • Summary

  26. Summary and Outlook • The potential of the differential infrared thermography (DIT) for the characterisation of the temperature evolution in am flashing jet has been explored • Experiments were carried out under vacuum condition employing ethanol as test fluid. • The best results are obtained when the spray temperature is intermediate between the two background values • The temperature showed a decay along the spray centreline • With increasing superheat level, the cooling rate increases • Results with a good agreement with the thermocouple measurement. Outlook • further investigation are needed to evaluate the effect of radiative, infrared scattering on the temperature measurement

  27. Thank You

  28. Backup

  29. Experimental Setup • Requirements: • Reproducible test conditions • P∞: from 0.02 bar to 0.4 bar • T∞=20°C • Tinj: from 35 °C to 140°C • Pinj= 10 bar • Good Vacuum (P∞=390 Pa) • Possibility to vary independently injection pressure and temperature • Problem: • Maintaining a constant backpressure • Solution: • Fast response injection

  30. Injector • Requirements: • Short injection and transient times → Constant backpressure • Constant injection conditions (i.e. pressure & temperature) • Reproducible test conditions  heated, modified diesel injector Courtesy of Bosch GmbH

  31. Results (Axial Profile) Liquid: ethanol, pam = 0.1 bar, pinj = 10bar

  32. Results (Axial Profile) Liquid: ethanol, Tinj = 389 K, pinj = 10bar

  33. Vacuum Chamber • Watercooling→ topreventtemperaturegradients in thetestchamber • Chambertemperaturecontrolledthrough 3 thermocouples

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