Transient temperature, pressure, and flow characteristics of high-pressure hydrogen-containing mixtures during discharge from an orifice

In this article, transient flow characteristics of high-pressure hydrogen-containing mixtures during discharge are comprehensively investigated. Thermodynamic governing equations and a calculation software package are established for the transient flow of hydrogen-containing mixtures through an orifice. An experimental setup is developed for the orifice discharge processes of hydrogen-containing mixture and the software package is validated using the experimental results of (0.7H₂ + 0.3 CO₂) (mole fraction) mixture in the pressure vessel flowing through a needle valve and existing experimental data of pure hydrogen. The transient temperature-time behavior for hydrogen-containing mixtures resembled that of pure hydrogen that the temperature first decreased in the discharge and then drifted back. The heat transfer coefficient has a great effect on the transient temperature and relatively small effect on the transient pressure. The initial pressure affected the amplitude of temperature variation in the beginning of the discharge process. The composition of the hydrogen-containing mixture has an effect on the density and mass flow rate in the discharge process. Furthermore, the dependence of the characteristic flow time and initial mass flow rate on the initial operation conditions and structural parameters is investigated and a standalone desktop app containing the calculation package is shared, which is inspiring for the hydrogen energy applications involving hydrogen-containing mixtures.