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[Display omitted] • Single and twin-fluid atomizers in spray column conditions were investigated. • Link between spray properties, entrained fraction and pressure loss was established. • ΔP is controlled mainly by liquid velocity at the atomizer exit orifice. • Entrainment model was adjusted to twin-fluid atomizers and empirical correlation was provided. • ΔP model was developed considering both droplet size and droplet distribution shape. The interaction of spray with counter-flowing flue gas causes pressure loss (ΔP) and influences droplet entrainment and sorbent loss in gas–liquid scrubbers. As these phenomena were usually investigated separately and not linked with atomizer characteristics, it is difficult to obtain insight into the scrubber operation and select an atomization device proper to particular process. Atomizers typically used in a spray column, together with pressure-swirl and twin fluid effervescent types, were tested in column-like conditions. All the atomizers were tested at the same liquid flow rate of 140 kg/h, with inlet pressure (p in) from 0.025 to 0.2 MPa under the counter–flow velocity (u cf) ranging from 0 to 1 m/s. A small-scale low-speed wind tunnel was specially designed to simulate spray column flow conditions. The ΔP and droplet entrainment were correlated with atomizer operating regimes. Empirical and analytical models of ΔP were compared with experimental results for different atomizers. Limitations of both models are discussed. The ΔP is influenced by the spray velocity at the discharge orifice (u L) and correlates well with the liquid kinetic energy (E k) and Reynolds number at the discharge orifice. The atomizers working on higher p in , provide a larger interfacial area, but yield higher E k at the discharge orifice, causing larger ΔP and a greater risk of sorbent loss due to presence of smaller droplets. [ABSTRACT FROM AUTHOR]

Sprays are exposed to ambient flow in most of their applications, which alters the spray behaviour. The understanding of spray performance in realistic conditions allows for nozzle improvements, process intensification, or emission reductions. The present paper investigates the pressure-swirl atomizer operating at three Reynolds numbers in the inlet ports (Re p) 960, 1330 and 1880, subjected to low-turbulence cross-flow with aerodynamic Weber number (We) from 0 to 7.1. High-speed visualization and phase Doppler anemometry (PDA) captured the characteristic shape and trajectory of the spray, droplet dynamics, droplet collisions, and spatial droplet distributions. An empirical correlation for a mean spray trajectory prediction was developed for a wide range of flow parameters. An analytical model of the droplet trajectory was assembled and validated using PDA data. The model accurately predicts trajectories for droplets larger than 40 μ m. A mutual interaction of droplets was investigated. Elevated cross-flow velocity (v) increased the impact Weber number and the total droplet collision rate and enhanced the droplet mixing. A bag breakup regime was observed for the liquid to the air momentum ratio (q) lower than 300. The bag breakup modified the initial droplet velocity. The experiments imply the formation of a complicated vortex structure around the pressure swirl spray in cross-flow. [ABSTRACT FROM AUTHOR]

Numerical prediction of discharge parameters allows design of a pressure-swirl atomizer in a fast and cheap manner, yet it must provide reliable results for a wide range of geometries and operating regimes. Many authors have used different numerical setups for similar cases and often concluded opposite suggestions on numerical setup. This paper compares 2D (two-dimensional) axisymmetric, 3D (three-dimensional) periodic and full 3D numerical models used for estimation of the internal flow characteristics of a pressure-swirl atomizer. The computed results are compared with experimental data in terms of spray cone angle, discharge coefficient (CD), internal air-core dimensions, and velocity profiles. The three-component velocity was experimentally measured using a Laser Doppler Anemometry in a scaled transparent model of the atomizer. The internal air-core was visualized by a high-speed camera with backlit illumination. Tested conditions covered a wide range of the Reynolds numbers within the inlet ports, Re = 1000, 2000, 4000. The flow was treated as both steady and transient flow. The numerical solver used laminar and several turbulence models, represented by k-ε and k-ω models, Reynolds Stress model (RSM) and Large Eddy Simulation (LES). The laminar solver was capable of closely predicting the CD, air-core dimensions and velocity profiles compared with the experimental results in both 2D and 3D simulations. The LES performed similarly to the laminar solver for low Re and was slightly superior for Re = 4000. The two-equation models were sensitive to proper solving of the near wall flow and were not accurate for low Re. Surprisingly, the RSM produced the worst results. [ABSTRACT FROM AUTHOR]

• The internal flows in transparent spill-return atomizers were investigated experimentally. • The modified inviscid analysis was applied for discharge coefficient and air-core size prediction. • Turn-down ratio decreases with increasing radius on which the spill-line orifices are located. • Three modes of liquid sheet dynamics were identified under identical operating conditions. • The air-core fluctuations determine the liquid sheet stability. The sprays produced by spill-return pressure-swirl atomizers are strongly dependent on the nature of the internal fluid dynamics. Several spill-return atomizers were compared in terms of the spatial and temporal behaviour of the internal air-core, liquid sheet thickness and its perturbations. The only difference amongst the test configurations was the geometrical arrangement of the spill-line (SL) orifice through which the liquid was spilled away. The flow field inside the swirl chamber was examined using high-speed imaging with image post processing using an in-house Matlab code and three orthogonal velocity components acquired using Laser Doppler Anemometry. The dimensions of the production atomizers did not allow direct visualization of their internal flow, so a scaled, modular, transparent plexiglass model was used. Its flow characteristics were equivalent to the original atomizer. The refractive index of the atomizer body was matched to the test liquid using a solution of 1-Bromonaphthalene and kerosene fuel type JET A-1. The test conditions were derived from the original atomizer and were limited to inlet port Reynolds numbers, from 700 to 2000 and spill-to-feed ratios, SFR , from 0 to 0.75. An inviscid analysis, originally derived for Simplex atomizers, was modified and applied to the spill-return version. This approach allows a theoretical prediction of the discharge coefficient and air-core diameter dependent solely on SFR. An axially located SL orifice inhibits any internal air-core forming in the swirl chamber. Off-axial SL orifices generate and stabilize the air-core, which leads to the regular formation of a liquid sheet and a high-quality spray. Nevertheless, some configurations changed the breakup nature of the liquid sheet and consequently the spray quality. Moreover, the turn-down ratio of the liquid supply rate and spray stability depend on the distance of the SL orifices from the swirl chamber centreline. The flow energy losses increase with SFR. The outcomes from this analysis allow the optimization of the SL configuration for specific application and extend the classical inviscid analysis. [ABSTRACT FROM AUTHOR]