Vol.11, No2, 2011, pp. 75-81
UDC 621.643.2.02:532.542

This paper presents a method of studying resonance phenomenon of hydrogen-natural gas mixtures flows in pipelines. To simulate the resonance phenomenon, an oscillatory pressure at the upstream end of the pipe is considered while the downstream end is kept closed. The oscillation frequency is taken as a multiple of the fundamental frequency of the system. The Governing equations for such problem are two coupled, non-linear, hyperbolic, partial differential equations. The fluid pressure and velocity are considered as two principal dependent variables. The fluid is a homogeneous hydrogen-natural gas mixture for which the density is defined by an expression averaging the two gas densities where an isentropic process is admitted for the two components. The hydrogen-mixture mass ratio (or quality), assumed to be constant is used in the mathematical formulation, instead of the void fraction which varies with pressure. The problem has been solved by the non-linear method of characteristics. The obtained results show that the pressure evolution is well influenced by the excitation frequencies and it builds up to a steady-oscillatory behaviour (unless failure occurs). Shock waves with resonant frequency and antiresonant frequencies are numerically obtained and the influence of different hydrogen mass fractions in the hydrogen-natural mixtures and diameters of the pipe are also analysed. Furthermore, dissolution and permeation evolutions as functions of time, of hydrogen and mixtures, are plotted. These plots have shown too, the influence of the excitation frequencies on the dissolution and permeation rate.

Keywords: hydrogen-natural gas mixtures, resonance phenomenon, method of characteristics, natural gas pipelines