Analysis of elbow erosion in natural gas–hydrogen pipelines under dense and pseudo-dense phase flow: a CFD-DEM (gas–solid flow) study

In this study, the erosion behavior of elbows in natural gas–hydrogen pipelines was investigated using CFD-DEM under dense phase (DP), pseudo-dense phase (PDP), and vapor phase (VP) conditions. Three pipeline models were analyzed: model 1 with 0% hydrogen, model 2 with 2%, and model 3 with 4%. The simulations explored the effects of Reynolds numbers (2,000,000–5,000,000), particle diameters (100–300 μm), and particle mass flow rates (100–300 kg/h) on the erosion rate. The results showed that across all models, the erosion rate increased with Reynolds number, particle mass flow rate, and particle diameter. At Reynolds number 2,000,000, the erosion rate in DP was about 60% lower than in VP for model 1, 64% lower for model 2, and 60% lower for model 3. As hydrogen mole fraction increased, the erosion rate slightly decreased: in DP at Reynolds 2,000,000, the erosion for model 3 was 5% lower than model 2 and 2.5% lower than model 1. Across all particle diameters, the maximum erosion rate in DP was 63% lower than in VP and 20% lower than in PDP. At 100 μm, the DP erosion rate for model 1 was 67% and 31% lower than VP and PDP; for model 2, 70% and 19% lower; and for model 3, 65% and 16% lower. The Reynolds number had a stronger effect on erosion than particle mass flow rate or diameter. High hydrogen content slightly reduces erosion but requires higher pressure.