1. Monitoring H2 by Real Time H2 Sensor
by Nohmi Takashi & Mogi Toshio
Topics for 2 consecutive presentations
1 Mixing H2 with AIR, N2 Gases
:Before and After Diffusion to find localized H2 Clouds
2 The concentration change of H2 in msecond is topics
3 Visible Evidence of H2 Bubbles
4 Buoyancy of H2 in flow
5 Spike Head H2 in Long Tube
6 Dependency on the Diameter Effect of Tube
7 Exhaust Gas of FCV

2. GLOBAL REGISTRY Global technical regulation HYDROGEN POWERED VEHICLE
Fuel cell discharge system: [At vehicle exhaust system’s point of discharge, the hydrogen concentration level shall not exceed 4% average by volume during any moving three-second (3sec) time interval during normal operation including start-up and shutdown.]
Center line of
the exhaust gas outlet
100mm
H2 Sensor
Sampling Point

3. Sx Schematic Diagram
Sx image

4. Fig. Sx Sensor Output vs H2 Concentration Log/Log
Concentration vs Intensity
Riability test for repeated injection H2
Pulse Front
Pulse End

5. Fig. Visualization of H2 Bubble by Smoke Particles.
H2 By injection from 10ml syring
Transparent plastic tube filled
by smoke particles
Visualization by Light source
Inlet of H2
Flows Spiral structure
To cut the inertia to Z axes
As possible
The H2 comes out by buoyancy

6. Cylinder Experiment Vertical and Horizontal
Vertical Position
Procedure:
1 reduce pressure in cylinder
2 filled by N2
3 H2 introduced from bottom
４Movement of H2 clouds
Different in Vertical/ Horizontal
Horizontal Position

7. Figure Vertical mixing (right-angle mixing head)
L:12.4m, Presuure:0.2MPa N2&H2

8. Introduction of H2 1msec pulse in Air and N2
H2 introduction to N2 in pipe
All experiment is started by preset experimental condition
To reach the equilibrium concentration of H2
The front wave concentration showed differently as expected and equilibrium concentration
Ceq =27%
Cmax=44%
Depend onpreset conditions

9. H2 pulse 1-100msec Quick valve motion did not followed by 1ms demand
5msec pulse H2 showed 78% H2 compared to equilibrium concentration of 27%
As Pulse width increase, Spike width increased
But the concentration of H2 spike head decreased

10. H2 pulse 1-100msec Spike Width dependency Spike Height dependency
by given H2 pulse
Spike Height dependency
Cmax vs Ceq by given H2 pulse

11. Buoyancy Effect in Pipe
In Past Experiments the Introduction of H2 plse to N2 in various diameter of Pipes showed By AIST (National Institute of Advanced Industrial Science and Technology in Tsukuba)
1) More than 25mm -150mm diameter of Pipes H2 front comes first in the upper layer
2)At the end of pulse introduction of H2, H2 last longer in the upper layer of pipe H2 than Lower layer of pipe
3)Upper layer, the concentration of H2 is higher than lower especially in front and the end wave

12. H2 Concentration in FCV Exhaust Gas
1) H2 concentration was analyzed
In FCV exhaust gas in 2ms interval
2) Pulse H2 in 60 seconds interval
During idling condition
3) Shape of the spectra reflecting
the structure of Fuel Cell stack
2 Patterns

13. H2 Monitoring Reflect the flow pattern of H2 clouds in Exhaust Pipe Considering the delocalized concentration of H2 clouds
Fuel cell discharge system: [At vehicle exhaust system’s point of discharge, the hydrogen concentration level shall not exceed 4% average by volume during any moving three-second (3sec) time interval during normal operation including start-up and shutdown.]
Localized clouds
Center line of
the exhaust gas outlet
1) H2 Spike Head
in front wave of H2 pulse
2) H2 Buoyancy Effect in Pipe
3) Detection should be taken
Into account the clouds direction
To be sprayed
100mm
H2 Sensor
Sampling Point

14. Conclusion
A) Real time monitoring of H2 by Sx showed H2 clouds before diffusion.
B) Our actual data showed
The high concentration phase of H2 clouds survives and moves upward by buoyancy or flow forming the spike head rather than homogeneously diffusing.
C) Also when mixing proceeds, the head of H2 cloud moves straight to form the spike head as observed in millisecond monitored by Sx.
D) In the cylinder experiment and also the transparent plastic tube experiment showed H2 cloud movement upward rather than diffusing in all directions.
E) In FCV Exhaust Gas H2 Concentration Monitored showed quite similar pattern in spike experiment. High concentration of H2 appeared in every H2 purging actions depend on Fuel Cell Stack Structure.
In basic theory of Rayleigh-Taylor instability, if the two gas phases instead of the two fluids with different densities is considered, the spike head might be came out as a cloud which we observed by Sx. The instability of the plane interface between the two fluids, when it occurs, is called the Rayleigh-Taylor instability”

15. Thank you for your attention
Nohmi Takashi
nohmi.tokyo
Sx for FCV exhaust Gas Pattern Analysis