Our CFD tools have been utilized for high fidelity analyses of complex valve and feed systems. Such systems include industrial valve systems as well as feed systems used in liquid rocket engines and high pressure rocket propulsion test facilities. The operating flow regimes for such analyses can vary widely from highly compressible gases to low speed incompressible liquids to cryogenic liquids undergoing cavitation with thermal effects. Our hybrid unstructured based CFD code has been used for simulations of cryogenic control valves, pressure regulator valves, globe valves, SSME (Space Shuttle Main Engine)manifolds as well as for orifice and venturi-type control elements where cavitation is prevalent. The simulations have been validated against experimental results and test data over a broad range of operating conditions.
Apart from performance maps and flow coefficient metrics, characterization of unsteady behavior in valve and feed systems has also been carried out for different types of instabilities. These include (a) hydrodynamic instabilities stemming from inherent structural causes such as sharp bends in feed ducts, structural transitions in valve housings, resonant cavities in plug designs (b) dynamic events related to valve timing and valve scheduling (c) cavitation based instabilities related to cryogenic flow in feed system and flow control elements such as venturis. Such analyses are carried out with advanced unsteady cavitation models, LES and hybrid RANS-LES type turbulence modeling procedures and automated grid motion capabilities. The grid motion procedure is tailored for complex valve systems and permits different grid topologies to be utilized during valve movement/plug motion. Dominant frequencies associated with the instability mechanisms are identified as part of the simulation process and system response is analyzed both in terms of coupling with different system components and excitation of structural modes. Different physical phenomena ranging from valve stall, valve chatter, valve response to varying plug motion as well as cavitating instabilities in valve and feed system components have been simulated.
