Simultaneous visualization of density and pressure in hydrogen leakage based on self-imaging via dual-channel interference

Risk assessment of hydrogen energy technologies is a necessary condition for the arrival of a hydrogen energy economy society. Currently, most methods for detecting hydrogen leaks use a single concentration or pressure sensor. Structural visualization and parametric diagnosis of complex flow fields cannot be solved simultaneously by a single detection method. The main objective of this work is to propose an advanced optical detection method to simultaneously monitor the outlet pressure and density field distribution during hydrogen leakage. For the detection of the density field distribution, we use double propagation of the laser beam in the hydrogen jet to improve the phase sensitivity and relay imaging of the object between each pass to maintain spatial resolution. Error analysis shows that the error of our proposed method is 2.47 %, which is within the error tolerance. The sensitivity analysis shows that our detection sensitivity is twice that of the conventional Mach-Zehnder interferometer. For the detection of outlet pressure, we propose a mathematical model in which the half-length axis of the laser spot is linearly related to the outlet pressure and use the deformation of the laser beam in the hydrogen jet to detect the outlet pressure. The results show that the hydrogen jet can be regarded as a gas-phase lens when detecting the outlet pressure, and the deformation of the laser beam profile in the horizontal direction increases linearly with the increase of the jet pressure. The results of the study can provide a reference for the detection of accidental hydrogen leakage and the improvement of hydrogen safety regulations.