A novel two-phase quality measurement technique using vortex frequencies in fluid flows

Accurate two-phase measurement has the potential to unlock new capabilities in energy conversion and control. Measuring real-time quality remains a problem due to the complex, non-linear interaction between the phases. Conventional methods often rely on intrusive or multi-point instrumentation, limiting their suitability for compact or embedded applications. This study offers a solution by presenting a novel method for estimating steam quality using vortex shedding frequencies from a flow meter. A dedicated test facility was developed to evaluate the approach, maintaining a fixed 30 kg/hr mass flow rate, at pressures 1.2–1.6 bar, and quality 0.91–0.51. During exploratory testing, vortex frequency showed two distinct bands, suggesting the presence of two mediums. This presented a method from which four different hypotheses were assessed: (1) a midpoint threshold between distinctive vapour and liquid frequency bands, (2) a fixed frequency cut-off at the onset of the liquid peak, (3) a kurtosis-based regression model, and (4) a linear regression based on the mean vortex frequency. The first three methods demonstrated limited or inconsistent accuracy. The fourth method, demonstrating the impact of this work, yielded results that indicated a strong correlation with true vapour quality with R2 ∼ 0.97, validated against repeatable condensate mass measurements with accuracy in vapour quality of ± 0.02. These results confirm that frequency signals typically used for volumetric flow, can be uniquely repurposed as indicators of phase composition. The contribution of this approach lies in enabling real-time quality monitoring in systems requiring the measurement and control of two-phase flows.