Abstract
Supersonic expansions of a molecularly complex vapor occurring within the non-ideal thermodynamic region in the close proximity of liquid-vapor saturation curve were characterized experimentally for the first time. Results for two planar converging–diverging nozzles in the adapted regime and at different inlet conditions, from highly non-ideal to dilute gas state, are reported. Measurements of upstream total pressure and temperature are performed in the plenum ahead of the nozzle, while static pressure and supersonic Mach number measurements are carried out along the nozzle centerline. The investigated expansions are of interest for both fundamental research on non-ideal compressible flows and industrial applications, especially in the energy field. Siloxane MDM (octamethyltrisiloxane, text {C}_8text {H}_{24}text {O}_2text {Si}_3), a high molecular complexity organic compound, is used. Local pressure ratio P/P_mathrm{T} and Mach number M measurements display a dependence on the inlet total state, a typical non-ideal feature different from dilute gas conditions.
Highlights
Non-ideal compressible flows of molecularly complex vapors are of interest for diverse industrial applications such as transportation of high-pressure fuels and chemicals and for turbomachines
Expansions taking place within ORC turbine blade channels are of particular interest, since they occur in the close proximity of vapor saturation curve and critical point
Detailed experimental data are needed about Non-Ideal Compressible Fluid Dynamics (NICFD) flows, with a particular focus on ORC power systems, which are unavailable in the open literature up to date
Summary
Non-ideal compressible flows of molecularly complex vapors are of interest for diverse industrial applications such as transportation of high-pressure fuels and chemicals and for turbomachines. The latter are typically implemented in chemical processes and in energy systems, as it is the case of compressors for refrigeration industry and turbo-expanders for organic Rankine cycles (ORCs). Working fluids involved are typically organic compounds such as aliphatic and aromatic hydrocarbons, halocarbons, and siloxanes, which feature high molecular complexity and high molecular mass. Expansions taking place within ORC turbine blade channels are of particular interest, since they occur in the close proximity of vapor saturation curve and critical point
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