Species-resolved non-equilibrium condensation of light hydrocarbons in a rotating compressible natural-gas flow

Light-hydrocarbon condensation in rapidly expanding natural-gas flows couples finite-rate multicomponent phase change with species-dependent supersaturation and latent-heat feedback. Its response in rotating compressible passages remains insufficiently resolved. A species-resolved non-equilibrium condensation model is formulated for a lean CH4/C2H6/C3H8/N2 mixture undergoing low-temperature expansion. The formulation combines a partial-pressure-based supersaturation criterion, real-gas equilibrium correction, species-resolved source terms, and latent-heat feedback in a three-dimensional Reynolds-averaged compressible-flow framework for a radial-inflow passage. Under the investigated conditions, propane dominates homogeneous nucleation and establishes the primary droplet population, whereas ethane condenses mainly through growth on existing droplets; at the lowest inlet temperatures, downstream ethane growth can provide the larger liquid-mass contribution. For the baseline composition, condensation is pronounced below ∼ 210 K and weakens as the inlet total temperature increases from 180 to 220 K. At 180 K, the non-condensing calculation overpredicts the isentropic and polytropic efficiencies by 2.84 and 2.74 percentage points, respectively; the differences become negligible as condensation weakens. At 220 K, increasing the propane mole fraction from 0.69 to 2.07 mol. % raises the outlet liquid mass fraction from nearly zero to about 4.31%. The condensation front is controlled by the coupled evolution of species partial pressure, saturation pressure, phase relaxation, and passage-scale aerodynamics.