Flow regime maps are essential to gas-liquid flow applications in many industrial processes to accurately identify the flow regimes before estimating multiphase features. Flow regime classifications were originally based on visual observations of two-phase flow experiments. The observations were mapped on two-dimensional plots (called “flow regime maps”) and the boundaries between regimes determined. Over the years, different coordinates have been proposed for the maps (e.g., superficial velocities and momentum fluxes), in search for parameters that are independent of the given experimental set-up. This paper reports a study on developing new flow regime maps with a broader range of applications by using dimensionless parameter groups as the map coordinates. Various flow regime maps were developed with the use of different combinations of these parameter groups, then they were examined and assessed using datasets from published experimental research and the MultiFlowMet II project for validation. This initial feasibility study develops proof-of-concept flow regime maps that demonstrate the potential of dimensionless parameter groups to more accurately characterise multiphase flow in horizontal pipes, with the optimisation of these maps being considered in future works. The analysis revealed that combinations of the mixture Froude number (Frm) versus the ratio of gas superficial velocity to liquid superficial velocity (vSG/vSL), with the liquid phase Froude number (FrL) versus the gas phase Froude number (FrG) show potential for unambiguous identification and mapping of flow regimes, even for datasets with a wider range of operating conditions.

Spraying high viscous liquids is generally considered to be difficult, and a method for efficiently generating fine mists with high-viscosity liquids is required. In the present study, the performance of three types of twin-fluid mist generators, small orifice (SO) type, swirl type A, and swirl type B, which were developed in our laboratory, was examined in order to spray highly viscous liquids finely and efficiently. Then the performance, i.e., mass flow ratio, mist size, and generation power, of those three mist generators was measured. Sucrose fatty acid ester was used as a high-viscosity liquid sample. As a result of the comparison of performance among three kinds of mist generators, it was found that swirl type B can spray the smallest sized mists with the lowest mass flow ratio.

Reuse of produced water to create stable oil-in-water dispersions (O/W) has sustainable environmental and economic EOR flooding benefits. Droplet size is a decisive characteristic as it can modify both stability and rheological behaviors of the dispersions. Presently, there are numerous techniques to determine emulsion stability and droplet size distribution (DSD). In this study, synthetic and crude oil are used to prepare different O/W emulsions with low oil concentrations similar to the oil-content in produced water (φ ≤ 5%). Water-soluble surfactant was dissolved in synthetic-formation-water and homogenized with the oil phase under optimized process conditions. High shear-rates with different oil and surfactant concentrations are applied. Coulter counter multisizer (CCM) and optical microscopy are employed to characterize the emulsions and measure DSD. Results showed that generated dispersed-oil-droplets are in size range similar to pore-size-distribution (PSD) of variety of sandstone core-plugs. Potentially, the formed O/W emulsions are relatively stable and can reach the target zone during injection without separating into oil and water phases individually. CCM was able to accurately detect the droplet size distribution. Emulsion stability and DSD are documented.

To accurately model the subsea distribution of accidentally released crude oil as a result of deep-sea oil well blowouts, the initial droplet size distribution is one of the most important input parameters. To date, only a very limited number of datasets contain results from large-scale experiments. Hence, a vast extrapolation to the field scale is often required, causing uncertainty when applying model correlations for the prediction of the ensuing droplet sizes, which have been tuned by means of lab-scale experimental results, to the field scale. In this paper, we present two-phase oil-in-water jet experiments conducted in two differently sized facilities with optical access. Lab-scale experiments with nozzle pipe diameters of 1-7.5 mm are compared to pilot-plant-scale experiments with nozzle pipe diameters of 32-74 mm. For the 32 mm nozzle pipe, additional cases with built-ins upstream of the nozzle exit are run for comparison, in order to simulate the influence of irregular blowout geometries. Endoscopic imaging is employed for the investigation of the droplet sizes. For the validation of the expected velocities and levels of the turbulent kinetic energy dissipation rate, particle image velocimetry is used. The resulting droplet size distributions are approximately log-normal. A model correlation for the prediction of droplet sizes based on existing literature correlations using the energy dissipation rate is deduced. Scale-up from lab to large scale is carried out on the basis of this correlation. The large-scale experimental results deviate significantly from the model correlation tuned by means of the small-scale results, which is referable to an upper limit of droplet stability. Considering the respective equation for this limit, in conjunction with the presented model correlation, provides a reasonable prediction of expectable droplet sizes for any scale of experiments.

Experimental data of two-phase pressure drops in horizontally-aligned 180deg; return bends (U-bends) were obtained to examine the applicability of bend pressure drop correlations. The pipe diameters were 8 and 16 mm and the dimensionless bend radii of curvature were 3 and 6. Glycerol-water solutions were used for the liquid phase and the glycerol concentration was varied to change the liquid viscosity. The ratio of the kinematic viscosity of the liquid phase to that of water was from 1 to 4.4. Air was used for the gas phase. The gas and liquid volumetric fluxes were varied so as to form bubbly, plug, slug, and annular flows. The data showed that the Lockhart-Martinelli method for bends proposed by Chisholm is applicable to the present experimental range and a correlation of the bend two-phase multiplier proposed in our previous study gives reasonable evaluations of the data. We also examined the applicability of the bend two-phase multiplier to data of single-component two-phase flows obtained by Padilla et al., confirming that the data are well correlated in the same form as in the present experiment.

GE Power Sweden AB developed an advanced mixing technology to cope with the demand for increased mixing in air quality control system applications. The recent technology is patented and trademarked under the name of a patented swirling technology mixer and is now applied in different products. Lately, the demand for high removal efficiency of NOx and simplification of selective catalytic reduction (SCR) systems has resulted in the need to implement the patented swirling technology with an ammonia direct injection system (ADIS). The combination of the two systems can reduce the number of injection nozzles and take advantage of the mixing capacity to even out NOx and temperature stratifications from the boiler and improve the NH3 distribution injected in the liquid or gas phase from a traditional ammonia injection grid (AIG) or ADIS system. In this paper, we demonstrate the efficiency of the patented swirling technology system together with the ADIS system in coping with different SCR applications and boiler loads, NOx, and temperature profiles. The patented swirling technology is applied in either tail-end SCR or high-dust applications. The design of the patented swirling technology mixer and ADIS system is confirmed by using computational fluid dynamics with the Euler-Lagrange Multiphase modeling approach to ensure complete evaporation of liquid ammonia droplets after injection from two-media nozzles. It is critical to evaporate all ammonia liquid droplets before reaching the patented swirling technology mixer area and to confirm the capacity of the mixer in order to uniformly distribute the gas phase components, such as NH3 and NOx, and consequently minimize the NH3/NOx stoichiometric ratio variation. A full-scale implementation of this system in a 330 MW coal-fired boiler with a high-dust SCR system showed that the capacity of the patented swirling technology mixer fulfilled the performance criteria upstream of the SCR catalyst and achieved the requested NOx removal efficiency and low NH3 slip at different loads.

This article is a personal tribute to the late Professor Geoff Hewitt, one of the founders of this journal and a towering figure in Multiphase Flow. It tells about how his passion for science, professional dedication and kind personality contributed to forging my identity as a scholar and academic advisor.