High‐pressure under‐expanded hydrogen leakage model considering gas‐wall friction loss

Abstract

Abstract The integral model is used to predict the concentration field, only suitable for low‐pressure leakage, while the virtual nozzle model is widely used in high‐pressure leakage but ignores the friction between the hydrogen and the tube wall during the leakage. We modified the virtual nozzle model by adding the gas‐wall friction loss term to the momentum conservation equation. A theoretical model of a high‐pressure under‐expanded jet is proposed by combining the integral model with the improved virtual nozzle model, which was validated by a series of helium (instead of hydrogen) dispersion in an unenclosed environment. And then the high‐pressure hydrogen leakage system was set up to investigate hydrogen concentration along the centerline of the jet was measured under different pressures. Results show that the mole fractions along with the axial distance all comply with the hyperbolic decay law. Within the range of 40 cm < z < 100 cm, at other pressures of 1, 2, 4 MPa, the minimum deviations of high‐pressure under‐expanded hydrogen leakage prediction model and experiments are 1.67%, 1.37%, 1.33%, respectively. The study is adequately precise to predict high‐pressure leakage concentration and also gives ideas about the installation position of the hydrogen sensor in engineering.

Keywords

• dispersion characteristics
• hyperbolic decay
• integral model
• virtual nozzle model