Seminar: Pressure Relief Valve Stability - from CFD to Spreadsheet
Csaba Hos (Budapest University of Technology and Economics)
Faculty Boardroom, Queen's School of Engineering, University Walk
As part of the Autumn term seminar series, the Fluid & Aerodynamics Research Group invite guest speaker Csaba Hos, Associate Professor from the Department of Hydrodynamic Systems at Budapest University of Technology and Economics to give a seminar.
Title: "Pressure Relief Valve Stability - from CFD to Spreadsheet"
When protecting industrial facilities against excess pressure, pressure relief valves (PRV) are the last line of defence. Although theses devices themselves are simple they exhibit surprisingly rich dynamics, especially when connected to upstream and/or downstream piping. These instability issues not only prevent the valves from fulfilling their original task but also induce severe system-wide vibrations and might lead to catastrophic failures.
The talk concentrates on the mathematical modelling of these valves together with the pipeline and reservoir dynamics. Starting from dynamic CFD computations, we regularly reduce the model until we find reduced-order models describing the core dynamics qualitatively. Various different notions of stability and mechanisms for instability are revealed both in the case of gas and liquid service. For each mechanism, a simple design formula is presented and explained for predicting the onset. Among these various mechanisms, oscillatory instability due to the interaction with a quarter-wave acoustic mode in the inlet piping is argued to be the most important to mitigate. It is also stressed that it is not the valve itself that is stable or unstable, rather that harmful vibrations arise through interactions between the valve and its surroundings: the inlet piping, the reservoir, and any outlet piping.