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QUANTITATIVE IMAGING OF MULTI-COMPONENT TURBULENT JETS

QUANTITATIVE IMAGING OF MULTI-COMPONENT TURBULENT JETS. Arash Ash Supervisors: Dr. Djilali Dr. Oshkai Institute for Integrated Energy Systems University of Victoria ICHS2011 – September 12 th 2011. Safety Standards.

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QUANTITATIVE IMAGING OF MULTI-COMPONENT TURBULENT JETS

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  1. QUANTITATIVE IMAGING OF MULTI-COMPONENT TURBULENT JETS Arash Ash Supervisors: Dr. Djilali Dr. Oshkai Institute for Integrated Energy Systems University of Victoria ICHS2011 – September 12th 2011

  2. Safety Standards • The integration of a hydrogen gas storage has not been without its challenges. • Flammable characteristics of Hydrogen results in the requirement of more robust, high pressure storage systems that can meet modern safety standards. • Prior to the development of a hydrogen infrastructure, well-researched safety standards must be implemented to reduce the risk of uncontrolled leaks related to hydrogen storage.

  3. H2 – Fuel Cell Application

  4. Project Motivation and Objectives • Perform series of well-defined experiments to generate data to guide development of engineering turbulence model suitable for rapid discharge simulations • Objectives • experimentally characterize the effects of buoyancy and cross-flow in a complex flow structure • provide a quantitative database that can be used for future concentration measurements and also to validate CFD models

  5. Introduction • the momentum and buoyancy effects related to the rapid, uncontrolled release of hydrogen must be studied in detail to accurately determine the resultant dispersion. • In this study, dispersion of a buoyant, turbulent, round jet in a quiescent and moving ambient at a wide range of Froude numbers was investigated. • This study focuses on slow leaks which might take place in small-scaled hydrogen based systems.

  6. Experimental Setup • Jet Apparatus: • honeycomb settling chamber • Sharp-edged orifice • Nozzle Diameter = 2mm • Cross-flow assembly: • 11m/s ± 4% • Laser: Nd YAG 532 nm • CCD camera: 1376 × 1040 pixels

  7. Flow Conditions Where Fr – Froude number, Dimensionless;Uoc– Jet centerline exit velocity, m/s; g – acceleration due to gravity, m2/s; D – Jet diameter, mm; , ρ – Ambient air density, kg/m3 and ρj – Jet exit density of helium, kg/m3

  8. PIV - Cross Correlation Particles In image B Original IA Search Area

  9. Results and Discussions

  10. Velocity Fields • Free Jet • Jet in Cross - Flow

  11. Jet Centerline • New coordinate system • Jet Centerline

  12. Jet Centerline (Continue) Free Jet Jet in Cross-flow

  13. Scaling Factors Jet in Cross-flow Free Jet first effects of buoyancy in case of Fr = 250 and 50, happens at approximately x/LM = 0.16 and 0.61 which corresponds to x/D = 43 and 32 respectively. rD scaling scaling Where

  14. Velocity Decays Free Jet Jet in Cross-flow Where: Uoc is mean nozzle exit velocity

  15. Velocity Decay (Continue) 1. Decay rates are faster in cross- flowing jets 2. In jet far-field region decay rates drop for jets in cross-flow 3. Decay rate drops in Buoyancy dominated regions NCF = Free jet WCF = Jet in cross-flow

  16. Turbulence Quantities Free jet Jet in cross-flow Where,Ucis the time-averaged velocity magnitude along the jet centerline

  17. Conclusion • Effects of buoyancy and cross-flow were investigated in subsonic release of Helium, • Mean and fluctuation velocity components were quantified using PIV, • lowering the Froude number led to slower velocity decays due to the buoyancy-driven acceleration components in buoyancy dominated regions, • Increasing effects of buoyancy were observed by reducing the Froude number, • The present data can serve to validate computational models derived for investigating hydrogen safety scenarios.

  18. Thank you Questions?

  19. Appendix • Initial Condition – Sharp-edged Orifice

  20. Velocity Profiles Free Jet Jet in cross-flow

  21. Seeding - Stokes number • Seeding particles must: • Match fluid properties • Neutrally buoyant • Short response time to flow motion • Reflectivity Particle Flow is dominated by Stokes drag: For St>>1, particles will continue in a straight line regardless of fluid streamline but for St<<1, particles will follow the fluid streamlines closely.

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