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EXPERIMENTAL STUDY OF HYDROGEN RELEASES IN THE PASSENGER COMPARTMENT OF A PIAGGIO PORTER VAN

EXPERIMENTAL STUDY OF HYDROGEN RELEASES IN THE PASSENGER COMPARTMENT OF A PIAGGIO PORTER VAN M. Schiavetti, V. Mattoli, G. Lutzemberger, P. Dario and M. Carcassi. Università di Pisa. Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP), University of Pisa.

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EXPERIMENTAL STUDY OF HYDROGEN RELEASES IN THE PASSENGER COMPARTMENT OF A PIAGGIO PORTER VAN

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  1. EXPERIMENTAL STUDY OF HYDROGEN RELEASES IN THE PASSENGER COMPARTMENT OF A PIAGGIO PORTER VAN M. Schiavetti, V.Mattoli, G. Lutzemberger, P. Dario and M. Carcassi Università di Pisa Dipartimento di Ingegneria Meccanica, Nucleare e della Produzione (DIMNP), University of Pisa ICHS 2011 - San Francisco, USA - September 12 -14

  2. “FILIERA IDROGENO” PROJECT SPONSORS: The project promotes the development and testing of mobility systems powered with H2 Italian Ministry of University MIUR One of the objectives of the project was to replace the electric powered system of a Piaggio porter with a H2 system and perform driving tests ICHS 2011 - San Francisco, USA - September 12 -14

  3. PIAGGIO PORTER VAN MAIN FEATURES ICHS 2011 - San Francisco, USA - September 12 -14

  4. HYDROGEN SYSTEM DESIGN ICHS 2011 - San Francisco, USA - September 12 -14

  5. SAFETY CONSIDERATIONS (Additional risks for the passengers due to the installation of the H2 system) • Vehicle was not designed to host the H2 system • Body kit could promote the accumulation of H2 under the vehicle • Air ventilation openings directly connect the passenger compartment with the external air under the vehicle • The ventilation air intake openings were located in front of the fuel cell ICHS 2011 - San Francisco, USA - September 12 -14

  6. Three main scenarios were identified Scenario 1: H2 may accumulate inside the passenger compartment during long term stops of the vehicle (diffusive leak) Scenario 2: H2 may enter inside the passenger compartment during the stops of the vehicle as a consequence of a major leak from the pipelines Scenario 3: During brief stops with the ventilation system on, the released H2 may be sucked inside the passenger compartment by the ventilation system ICHS 2011 - San Francisco, USA - September 12 -14

  7. EXPERIMENTAL SET-UP ICHS 2011 - San Francisco, USA - September 12 -14

  8. EXPERIMENTAL SET UP: RELEASE POSITIONS • Scenario 1: Releases inside the vehicle • H2 produced by a small electrolyzer • Release flow rate: 3 10-5 g/s • Release duration: 3 h • Scenario 2: Releases under the vehicle • Flow rate: 0.215 g/s • Pressure: 5 bar • Total H2 released:1.3 – 2.8 g • Scenario 3: Releases inside the ventilation fan • Flow rate: 0.05 - 0.215 g/s • Total H2 released: 1.3 – 15 g ICHS 2011 - San Francisco, USA - September 12 -14

  9. EXPERIMENTAL SET UP: Sensors Position • Under the vehicle 5 sensors MSA 9010 Range: 0-20% H2 vol. • Inside the vehicle 8 sensors coupled in 4 positions - KHS-200 MEMS micro- pellistor Range: 0-4% H2 vol. - Synkera trace hydrogen sensors P/N701 Range: 10-1000 ppm ICHS 2011 - San Francisco, USA - September 12 -14

  10. SCENARIO 1: Diffusive leaks Tests where conducted to check if H2 would accumulate inside the vehicle Hydrogen release rate: 3 10-5 g/s Release duration: 3 h H2 was released close to the right ventilation opening which directly connects the passenger compartment with the external air under vehicle Release position ICHS 2011 - San Francisco, USA - September 12 -14

  11. Almost steady state conditions were reached (H2 concentration close to 400 ppm) • No accumulation inside the vehicle H2 exits the vehicle through the gasket of the rear door on top of the canopy ICHS 2011 - San Francisco, USA - September 12 -14

  12. SCENARIO 2: Releases under the vehicle ICHS 2011 - San Francisco, USA - September 12 -14

  13. H2 released at the front (release position R1) reaches the passenger compartment easier Release time • Total H2 released: 2,4 g • (pipe H2 content of 1,4 g • + • 5 s of H2 release with 0,2 g/s flow rate) The pipe rupture with the correct closure of the bottles (5 s) does not release enough H2 to create a flammable atmosphere inside the vehicle ICHS 2011 - San Francisco, USA - September 12 -14

  14. Ventilation fan activated Decrease of H2 concentration under the vehicle H2 is sucked in the compartment by the ventilation Release position R1 H2under the vehicle Tests affected by the presence of wind Release position R1 H2inside the vehicle Wind does not affect H2 concentration measurements inside the vehicle Part of the released H2 is sucked in by the ventilation fan and mixes with the intake air. H2 exits the compartment from the ventilation openings. Ventilation fan de-activated H2 enters the compartment from the ventilation openings ICHS 2011 - San Francisco, USA - September 12 -14

  15. Effect of ventilation system • Test 7 (ventilation system off) • Test 11 (ventilation system on 170 m3/h) • Test 12 (ventilation system on 250 m3/h) Release position R1 Total H2 released: 2,4 g Release time H2 measurements at sensor 1 ICHS 2011 - San Francisco, USA - September 12 -14

  16. Scenario 3: Releases inside the ventilation system (from the right “defrost” ventilation opening) Air – hydrogen mixture Pure air ICHS 2011 - San Francisco, USA - September 12 -14

  17. Scenario 3: Releases inside the ventilation system – General behaviour The ratio hydrogen/air flow rates determines the hydrogen steady state concentration inside the vehicle ICHS 2011 - San Francisco, USA - September 12 -14

  18. TEST 23 and TEST 24 Test 23 H2 flow rate: 0.05 g/s Release time: 61.5 s Time to reach nearly steady state conditions inside the compartment is approximately 5 min Test 24 H2 flow rate: 0.05 g/s Release time: 301.5 s ICHS 2011 - San Francisco, USA - September 12 -14

  19. CONCLUSIONS (1/2) • Scenario 1: Releases inside the vehicle (diffusive leaks) • - Concentration inside the vehicle reached an asymptotic value of 400 ppm and further increase was found no possible in this kind of scenario. • Scenario 2:Releases under the vehicle • Concentration inside the vehicle was always lower than the 50%LEL when up to 2,4g of H2 was released. • - Hydrogen was sucked in the passenger compartment when the release took place in the position closest to the suction opening, however the concentration inside the vehicle was one order of magnitude lower as compared to the cases with the ventilation deactivated. • Scenario 3:Releases inside the ventilation system • - The ratio hydrogen/air flow rates determines the hydrogen steady state concentration inside the vehicle. • - H2 flow rate of 0.2g/s produce a flammable atmosphere inside the passenger compartment. -Time needed to reach stady state inside the passenger compartment is approximately 300 s. ICHS 2011 - San Francisco, USA - September 12 -14

  20. CONCLUSIONS (2/2) • No harm to the passenger of the vehicle is possible if the unintended leak • is the only undesirable event • If the release takes place while an independent event is undergoing (i.e. if • valves don’t isolate the storage bottles during the stops of the vehicle or when • the flow rate exceeds 120% of the maximum or decreases to 0 while the fuel cell is in • use) a bigger release can take place and the biuld up of a flammable atmosphere • inside the passenger compartment is possible • Overpressurization of the passenger compartment could prevent the build up of a • flammable atmsphere inside the vehicle but care should be taken in the design of • the position of the air intake ACKNOLEDGMENTS The authors would like to thank Italian Ministry of University MIUR and “Regione Toscana” for funding the “Filiera Idrogeno” project, whose funds have been used for this study ICHS 2011 - San Francisco, USA - September 12 -14

  21. THANK YOU. Contact Author: Martino Schiavetti (UNIPI-ITALY) martino.schiavetti@ing.unipi.it ICHS 2011 - San Francisco, USA - September 12 -14

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