A slip with entrained liquid fraction approach to compressible two-phase flow in nozzles

Abstract

Ideal flow theory adequately predicts pressure drops, critical mass flowrates and critical pressure ratios for single-phase gas flows in nozzles. A model based on these principles has been developed for two-phase, gas-liquid flows using a slip with entrained liquid fraction approach. The method relies on being able to establish the momentum flux of the fluid in the upstream supply pipe and therefore allows pipe flow correlations for slip ratios and entrained liquid fractions to be used at the nozzle inlet. Choking conditions are established from an isentropic pressure pulse approach. This produces a speed of sound for the two-phase mixture that gives choking conditions that are compatible with the end-limits of the momentum and energy equations used to estimate the pressure drops for non-choked compressible flows. This allows a consistency in approach between non-choked compressible and choked flows. The model predictions of pressure drops, critical pressure ratios and critical mass flowrates compare well with data sources and are an improvement on those made by other models available in the open literature.