GTR#13: towards inherently safer hydrogen-powered vehicles Prof Vladimir Molkov Recent advances by Hydrogen Safety Engineering and Research Centre (HySAFER) ulster.ac.uk
Outline of presentation Fire test (improved reproducibility) Pressure peaking phenomenon (new phenomenon) System storage container-tprd ( coupled approach) Concluding remarks List of relevant urgent PNR topics 2
Fire test reproducibility ulster.ac.uk
Definitions Bare container - ordinary (unprotected) container Protected container - container with thermal protection, e.g. intumescent paint, Ulster IP, etc. Heat release rate (HRR) - heat release rate in a fire [kw] Fire resistance rating (FRR) - time from burner ignition until container rupture in a fire (without TPRD) 4
Issues of GTR#13 fire test Poor reproducibility of the fire test in different laboratories. No test without TPRD (a serious first responders concern, EU HyResponse). EU FireCOMP: there is a non-zero probability of TPRD failure. No test procedure for novel thermally protected storage containers, e.g. explosion-free in a fire containers. 5
Poor reproducibility CFD: revealed dependence of FRR on HRR 6
Poor reproducibility Experimental validation of numerical study Heat release rate Fire source Fire resistance rating 79 kw [1] Premixed CH4-air burner 16 min 170 kw [1] Premixed CH4-air burner 9 min 370 kw [2, 3] Diffusion C3H8 burner 6.5 min 4100 kw [4] n-c7h16, pool fire 6 min [1] D. Makarov, Y. Kim, S. Kashkarov, V. Molkov, Thermal protection and fire resistance of high-pressure hydrogen storage, in Proceedings 8th ISFEH, Hefei, China, 2016. [2] N. Weyandt, Analysis of Induced Catastrophic Failure Of A 5000 psig Type IV Hydrogen Cylinder, Southwest Research Institute report for the MVFRI, 01.06939.01.001, 2005. [3] R. Zalosh, Blast waves and fireballs generated by hydrogen fuel tank rupture during fire exposure, in Proceedings 5th ISFEH, Edinburgh, UK, 2007. [4] L. Bustamante Valencia, P. Blanc-Vannet, L. Heudier, D. Jamois, Thermal history resulting in the failure of lightweight fully-wrapped composite pressure vessel for hydrogen in a fire experimental facility, Fire Technology, no. 52, pp. 421 442, 2016. 7
Poor reproducibility: way out Saturation of FRR at HRR>350 kw 8
Two ways to ensure reproducibility: Constant HRR above 350 kw Heat flux (input) of minimum 100 kw/m 2 HRR: saturation above 350 kw Heat flux: continuous decrease Steel? Type 4 (CFRP) 9
Two ways to ensure reproducibility: Constant HRR above 350 kw Heat flux (input) of minimum 100 kw/m 2 Parameter HRR (burner + LPG flow rate) Heat flux (input) Technical realisation Easy (as now) Complicated and questionable (suggested minimum is too high) Additional cost per test No $600 per sensor in a destructive test Location and number of sensors Provision of required control parameter level Steadiness of parameter in steady-state fire Easy (as now) Easy (as now) Yes Where and how? How many? Is it possible to provide minimum of 100 kw/m2 for type 4 No (decreases during the test) 1
ISO TC58: fire test without TPRD Right move: Fire test until rupture Right approach of ISO TC58 ( Gas Cylinders Guidance for design of composite cylinders Part 2: Bonfire test issues, ISO/TC 58/SC 3 N 1714, 2017): For cylinders tested under option B fire test until rupture 11
Engulfing fire test update Need in thermally protected tank test Current Engulfing fire test Method 1E: Bare tank Method 2E: Thermally protected tank 12
75 100 25 Method 1E: Bare tank (minor changes) New requirements: HRR 350 kw, TC location Bare tank Thermocouple 1650 Fire source 13
L2=100 L3=75 L1 Method 2E: Thermally protected tank Provide functioning of thermocouples Intumescent paint initial (unreacted) Intumescent paint (expanded) Thermally protected container (no TPRD) Fire source 1650 14
Temperature, C Method 2E: Thermally protected tank 590 Not less than 590 C HRR at least 350 kw 2 hours Till end of test 0 5 Time, min Maximum recorded duration of car fire is 2 hours (e.g. K. Okamoto, et al., Burning behaviour of minivan passenger cars, Fire Safety Journal, vol. 62, pp. 272 280, 2013). 15
Pressure peaking phenomenon ulster.ac.uk
Pressure peaking phenomenon Physics V vent Overpressure limit for structures (10-15 kpa) Example Garage 4.5x2.6x2.6 m, brick vent. Car (350 bar, D=5.08 mm): mass flow rate from TPRD 390 g/s. 2 1 2 P S PS PS CA 1 encl Pencl Pencl Solution: decrease TPRD diameter + increase fire resistance rating of onboard storage tank! 17 1 2
Overpressure, kpa Pressure peaking phenomenon Validation: air (no pressure peaking) Air release 2.8 g/s (enclosure 1 m 3, vent D=11 mm). Only gases lighter than air can generate pressure peaking. 0.7 0.6 0.5 Steady-state pressure without peak 0.4 0.3 0.2 0.1 0 HIWP4-044 Model prediction, CD=0.72 0 10 20 30 40 50 60 70 80 90 100 Time, s 18
Overpressure, kpa Pressure peaking phenomenon Validation: helium Helium release 0.99 g/s (enclosure 1 m 3, vent D=11 mm) 3 Pressure peak 2.5 2 1.5 1 0.5 0 HIWP4-046 MOdel prediction, CD=0.85 0 25 50 75 100 125 150 175 200 225 250 275 Time, s 19
Overpressure, kpa Pressure peaking phenomenon Validation: hydrogen Hydrogen release 0.55 g/s (enclosure 1 m 3, vent D=11 mm) 3.5 Pressure peak 3 2.5 2 1.5 1 0.5 0 HIWP4-049 Model prediction, CD=0.85 0 10 20 30 40 50 60 70 80 90 100 Time, s 20
Overpressure, kpa Overpressure, kpa Pressure peaking phenomenon Case 1 14 12 10 8 6 4 2 0 Unignited release in the garage: TPRD D=2.0 mm, P=70 MPa (107 g/s). 1 brick vent 2 bricks vent 3 bricks vent 4 bricks vent 0 10 20 30 40 50 60 Time, s Ignited release in the garage: TPRD D=2.0 mm, P=70 MPa (107 g/s). 220 200 180 160 140 120 100 80 60 40 20 0 1 brick vent 2 bricks vent 3 bricks vent 4 bricks vent 0 10 20 30 40 50 60 Time, s
Pressure peaking phenomenon Case 2 Ignited release from TPRD with D=0.3 mm in a garage 2.6x2.6x4.5 m with vent 1 brick (left) or 0.5 brick (right). Onboard tank storage pressure 700 bar. Garage can withstand overpressure 10 kpa. 22
System tank-tprd ulster.ac.uk
ISO/TC 58: decoupled tank-tprd test Could we model coupled functioning (reality)? ISO, Gas Cylinders Guidance for design of composite cylinders Part 2: Bonfire test issues, ISO/TC 58/SC 3 N 1714, 2017 24
Initiating time Wall thickness (mm) Pressure (bar) Simulation of tank-tprd system Initial model development 25 20 15 10 5 0 750 bar No TPRD 0.3 mm TPRD 0.5 mm TPRD Decomposed front of the wall Load bearing front of the wall Pressure 180 bar 15 bar 50 0 0 100 200 300 400 500 600 700 800 900 1000 Time (s) 800 750 700 650 600 550 500 450 400 350 300 250 200 150 100 25
Concluding remarks Improvement of GTR#13 fire test reproducibility is suggested through requirements of a burner to have heat release rate above 350 kw. Development of a burner requires additional PNR. Pressure peaking phenomenon could be practically eliminated using TPRD diameter of 0.3-0.5 mm. This would require increase of fire resistance rating (time to rupture in test without TPRD). The use of TPRD diameter 0.3-0.5 mm increases fire resistance (to let first responders more time to control and eliminate hazards ) yet doesn t exclude the tank rupture (preliminary result). Explosion-free in a fire tanks could be a solution. 26
List of relevant urgent PNR topics Burner design to provide GTR#13 fire test reproducibility, including effects of wind Testing pressure peaking phenomenon at realistic garage-like enclosures. Inherently safer tank-tprd system with minimised TPRD diameter (to exclude pressure peaking phenomenon and yet to avoid tank rupture) TPRD reliability data for risk assessment Development of explosion-free in a fire tanks Vehicles in tunnels, underground parking In-situ dumping of compressed gas potential energy 27
Thank you