The effect of water hammer on pressure oscillation of hydrogen natural gas transient flow

Abstract

The unexpected closing of a control valve or pumping, which can be planned or accidental could lead to pressure oscillation commonly known as water hammer. Pressure waves oscillation in the fluid flow interaction leads to unsteady state phenomenon. Numerical computation on transient flow model of hydrogen natural gas mixture (HCNG) in a pipeline where different types of valves are considered for effective delivery and safety. Reduced order modeling (ROM) technique is employed in the transient analysis of high pressured HCNG in a short pipe. The flow is governed by a system of Euler equations that are discretized using the implicit Steger-Warming flux vector splitting method (FSM). Eigenmode analysis and the subsequent construction of ROM use only a few dominant flow eigenmodes. The boundary conditions are imposed using the closure law at the upstream and downstream of the pipeline. The effect of closure function is analyzed and the results are presented on different mass ratios and HCNG flow parameters. The transient pressure oscillations of HCNG at different closure functions are compared so as to test the best type of valve for HCNG transportation. The highest and lowest value of transient pressure wave occurs when instantaneous and convex closure law is considered, respectively.