Decompression Behaviour of Natural Gas-Hydrogen Mixtures: Shock Tube Test and Numerical Prediction

Abstract Blending hydrogen into existing natural gas pipelines is a transition option to progressively increase the energy share of hydrogen. As part of the fracture control plan, pipelines must be capable of controlling a running ductile fracture for all blend ratios used in operations. It is important to understand the decompression characteristics of Natural Gas-Hydrogen (NGH2) mixtures at those ratios. Under the aegis of the Future Fuels Cooperative Research Centre (FFCRC), a project was initiated to investigate the implication of the use of NGH2 blends on the Australian network, under the assumption that pipe properties are not affected by hydrogen during ductile fracture propagation. In this work, a desktop study is carried out to evaluate the impact of hydrogen on the toughness requirements. The potential increase in toughness requirement with a rich gas mixture within a given range of hydrogen fraction is revealed. This provides a basis for the design of shock tube tests. Eleven shock tube tests of NGH2 mixtures were carried out at TC Energy’s Gas Dynamic Test Facility in Didsbury, Canada. The mixtures targeted concentrations of 0%, 9%, 30% and 100% hydrogen. The outcomes of the shock tube tests are reported. 1D isentropic numerical decompression wave speed predictions using the GERG-2008 equation of state are compared with experimental data.