Vented Hydrogen DDTs

Baker Engineering and Risk Consultants, Inc. (BakerRisk^®) and Daewoo Engineering and Construction Co. Ltd. (Daewoo) performed partially-confined vapor cloud explosion (VCE) tests with both propane and lean hydrogen mixtures. BakerRisk’s Deflagration Load Generator (DLG) test rig was used to perform the tests. The DLG test rig was designed primarily to produce centrally-peaked blast waves that are representative of VCEs suitable for blast loading test articles, but has also been used for vented deflagration testing. The DLG test rig is a steel box with one open side, measuring 48 ft long by 24 ft deep by 12 ft high (14.6 m by 7.3 m by 3.7 m). The DLG test rig is outfitted with congestion, filled with the desired fuel-air mixture, and then ignited near the center of the rear wall.

Two test series were performed. The first series of tests used a uniform very low congestion pattern with a near-stoichiometric propane-air mixture (4.33% propane). The average internal peak overpressures was 5.9 psig (0.4 bar). The second test series used the same congestion pattern, but tested lean hydrogen mixtures at increasing hydrogen concentrations. The first test was performed at 20% hydrogen and resulted in average internal peak overpressure of 8.6 psig (0.6 bar). The hydrogen concentration was increased to 22.5% in the second test, and a deflagration-to-detonation transition (DDT) occurred as the flame front exited near the central portion of the open face of the rig. Average internal peak overpressures for this second hydrogen test were approximately 89 psig (6.1 bar). The external peak pressures were also measured for both test series. High speed video recordings were made of all tests.

This paper describes the tests performed and discusses the implications with regards to predicting the blast loads resulting from vented VCEs.