This paper explains the new methodology for post-crash fuel leakage testing of Fuel Cell Vehicles (FCVs) and other hydrogen vehicles utilizing compressed hydrogen storage systems. This methodology was incorporated into SAE J2578 that was revised and published in January, 2009.
The new methodology is based on the concept in FMVSS 303 that specifies post-crash fuel leakage test method and criteria for CNG vehicle and adopted some modifications. Specifically, the following items are addressed:
(1) Allowable leakage can be accurately evaluated in test even with large size tank that obtains only small pressure drop when a given amount of leakage occurs. A new method to deal with the influence of measurement errors was devised.
(2) Even though only one option of test gas and initial filling pressure is accepted in FMVSS 303, new methodology for hydrogen system allows helium and hydrogen at reduced pressure as alternatives in addition to hydrogen at service pressure. Test with hydrogen at service pressure is easy to perform, but two alternatives are attractive for test safety if leakage occurs during the crash test. Those alternatives are intended to provide results that are equivalent to test with hydrogen at service pressure.
In order to improve the approach used in FMVSS303, a new simulation method was developed that can estimate the pressure change in the storage system after crash based on the mass leakage that could be occurring due to crash damage. Based on this simulation results, approximation equations for calculation of test time and leakage mass criteria were derived including compensations for test gas temperature and initial filling pressure.
The purpose of this paper is to provide the details relative to the simulation procedures and approximation equations used in SAE J2578 as it is envisioned that this approach will serve as the basis for future regulation of allowable post-crash fuel loss in FCVs and hydrogen vehicles.
