The Influence of Geometrical and Operational Parameters on Internal Flow Characteristics of Internally Mixing Twin-Fluid Y-Jet Atomizers

Abstract

Internally mixing twin-fluid Y-jet atomizers are widely used in coal-fired thermal power plants for start-up, oil-fired thermal power plants, and industrial boilers. The flow through internally mixing Y-jet atomizers is numerically modeled using the compressible Navier-Stokes equations; wall modeled large eddy simulations (WMLES) are used to resolve the turbulence with large eddy simulations whereas the Prandtl mixing length model is used for modeling the subgrid scale structures, which are affected by geometric and operational parameters. Moreover, the volume-of-fluid (VOF) method is used to capture the development and fragmentation of the liquid-gas interface within the Y-jet atomizer. The numerical results are compared with correlations available in the open literature for the pressure drop; further results are presented for the multiphase flow regime maps available for vertical pipes. The results show that the mixing point pressure is strongly dependent on the mixing port diameter to air port diameter ratio, specifically for gas to liquid mass flow-rate ratio (GLR) in the range 0.1 < GLR < 0.4; the mixing port length moderately affects the mixing point pressure while the angle between mixing and liquid ports is found not to have an appreciable effect. Moreover, it is found that the vertical pipe multiphase flow regime maps in the literature could be applied to the flow through the mixing port of the twin-fluid Y-jet atomizer. The main flow regimes found under the studied operational conditions are annular and wispy-annular flow.

Atomization Mechanism of Internally Mixing Twin-Fluid Y-Jet Atomizer

“…The internal flow pattern far downstream of the mixing point becomes an annular-mist flow with asymmetrical film thickness along the wall of the mixing-port, as characterized by Mullinger and Chigier (Mullinger & Chigier, 1974), Andreussi et al (Andreussi, et al, 1994), (Andreussi, et al, 1992), Pacifico and Yanagihara (Pacifico & Yanagihara, 2014) Mlkvik et al (Mlkvik, et al, 2015) and Nazeer et al (Nazeer, et al, 2019). The rate of direct drop formation within the mixing port is also strongly dependent on both and .…”

“…On the same figure, the values of the gas-to-liquid mass flow rate ratio ( / ) and the liquid-to-gas momentum ratio ( ) are also shown. These parameters are already adopted in the studies (Neya, et al, 1975), (De Michele, et al, 1991), (Andreussi, et al, 1992), (Song & Lee, 1994), (Andreussi, et al, 1994), (Pacifico & Yanagihara, 2014), (Mlkvik, et al, 2015) and (Nazeer, et al, 2019). Here is defined as:…”

“…There are few studies predicting the internal flow characteristics, flow rates and energy required for There are few studies predicting the internal flow characteristics, flow rates and energy required for the atomization (Nazeer, et al, 2019), (De Michele, et al, 1991), (Andreussi, et al, 1994), (Andreussi, et al, 1992) and (Song & Lee, 1994). There also exist several studies on the atomization characteristics of twin-fluid Y-jet atomizers (Song & Lee, 1996), (Mullinger & Chigier, 1974), (Neya, et al, 1975), and (Andreussi, et al, 1994); parameters such as atomizer geometry and injection conditions were taken as "input" and the spray performance was considered as "output."…”

Investigation of Oil Droplet Breakup during Atomization of Emulsions: Comparison of Pressure Swirl and Twin-Fluid Atomizers

“…In this case, the kinetic energy of the gas is transferred to the slowly moving liquid [13]. In twin fluid nozzles the air-to-liquid mass flow ratio (ALR) is used to characterize the energy input [18,19]. In contrast to PS nozzles, the process conditions of the atomization gas can be used to control the resulting spray droplet size independently from the liquid throughput.…”

“…In the IM configuration, a high-velocity gas and the liquid are mixed inside the nozzle before the discharge orifice [16,18]. In IM atomizers, energy is transferred from the gas to the liquid in form of shear stresses, which induces instabilities in the liquid stream leading to dispersion of the liquid [18,19,21]. An example of IM atomizer is the air-core-liquid-ring (ACLR) nozzle [22], in which an air core is established, surrounded by an annular liquid ring within the exit orifice of the nozzle (Figure 1c).…”