Arash Ash Supervisors Dr Djilali Dr Oshkai Institute for Integrated Energy Systems University of Victoria ICHS2011 September 12 th 2011 Safety Standards The integration of a hydrogen gas storage has not been without its challenges ID: 630914
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Slide1
QUANTITATIVE IMAGING OF MULTI-COMPONENT TURBULENT JETS
Arash AshSupervisors:Dr. DjilaliDr. OshkaiInstitute for Integrated Energy SystemsUniversity of VictoriaICHS2011 – September 12th 2011Slide2
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. Slide3
H2 – Fuel Cell ApplicationSlide4
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 Objectivesexperimentally characterize the effects of buoyancy and cross-flow in a complex flow structureprovide a quantitative database that can be used for future concentration measurements and also to validate CFD modelsSlide5
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.Slide6
Experimental Setup
Jet Apparatus:honeycomb settling chamberSharp-edged orificeNozzle Diameter = 2mmCross-flow assembly:11m/s ± 4%Laser:
Nd YAG 532 nmCCD camera: 1376 × 1040 pixels Slide7
Flow Conditions
Case
Q (lpm – H2
)
U
oc
(m/s)
Fr
Re
r164.4
318.33~1000526311.2243.4248.98
~750
4196
6.9
3
35.7
185.23
~500
3121
6.1
4
21
94.56~25015933.251218.86~503170.6Helium density and viscosity are 0.166 kg/m3 and 1.97E-05 kg/ms, respectively
Where
Fr
– Froude number, Dimensionless;
U
oc
– Jet centerline exit velocity, m/s;
g
– acceleration due to gravity, m
2
/s;
D
– Jet diameter, mm;
,
ρ
– Ambient air density, kg/m
3
and
ρ
j
– Jet exit density of helium, kg/m
3Slide8
PIV - Cross Correlation
Search Area
Original IA
Particles In image BSlide9
Results and DiscussionsSlide10
Velocity Fields
Free Jet
Jet in Cross - FlowSlide11
Jet Centerline
New coordinate systemJet CenterlineSlide12
Jet Centerline (Continue)
Free Jet
Jet in Cross-flowSlide13
Scaling Factors
Free Jet
Jet in Cross-flow
Where
first effects of buoyancy in case of Fr = 250 and 50, happens at approximately
x/L
M
= 0.16 and 0.61 which corresponds to
x/D
= 43 and 32 respectively. rD scalingscalingSlide14
Velocity Decays
Free JetJet in Cross-flow
Where:
U
oc
is mean nozzle exit velocity Slide15
Velocity Decay (Continue)
NCF = Free jetWCF = Jet in cross-flow
1. Decay rates are faster in cross- flowing jets2. In jet far-field region decay rates drop for jets in cross-flow3. Decay rate drops in Buoyancy dominated regionsSlide16
Turbulence Quantities
Free jetJet in cross-flow
Where,
Uc
is the time-averaged velocity magnitude along the jet centerlineSlide17
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.Slide18
Thank you
Questions?Slide19
Appendix
Initial Condition – Sharp-edged OrificeSlide20
Velocity Profiles
Free Jet Jet in cross-flowSlide21
Seeding - Stokes number
Seeding particles must:Match fluid propertiesNeutrally buoyantShort response time to flow motionReflectivityParticle 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.