Influence of the ambient pressure on the liquid accumulation and on the primary spray in prefilming airblast atomization

Chaussonnet, Geoffroy; Gepperth, Sebastian; Holz, Simon; Koch, Rainer; Bauer, Hans‐Jörg

doi:10.1016/j.ijmultiphaseflow.2020.103229

Cited by 41 publications

(30 citation statements)

References 40 publications

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“…Obviously, the increase of u g results in smaller droplet sizes d Drop and the increase of h a results in larger d Drop compared to the baseline case. This is in good agreement with experimental investigations [29,30]. For the P = 0.01 isolines, peaks of droplet size d Drop can be observed at x Drop = 1.2 and 1.8 mm.…”

Section: Effect Of Gas Velocity and Prefilmer Geometry On The Spray Esupporting

confidence: 92%

“…The slight decrease of the probability more downstream is related to the different axial velocities of the droplets. These observations regarding the distributions of l Lig and x Drop are in good agreement with experimental results (Figure 29 in [29]). The probability of the projected heights of the ligaments h Lig as well as the vertical droplet positions y Drop are depicted in Figure 11b.…”

Section: Relations Between Ligaments and Dropletssupporting

confidence: 91%

“…In contrast, u g seems to have no significant effect on the location of the primary breakup zone. Experimental results (Figure 24 (right) in [29]) indicate that for an increase of u g from 70 to 90 m/s the ligament length will not decrease significantly. Figure 16b reflects the acceleration of the droplets due to the imposed drag force.…”

Section: Effect Of Gas Velocity and Prefilmer Geometry On The Spray Ementioning

confidence: 97%

“…A planar prefilming airblast atomizer, Figure 3 (left), which has been extensively studied experimentally [11,29,30], is investigated numerically using a 2D segment at the trailing edge, as depicted in Figure 3 (right). The trailing edge thickness h a , which has a significant influence on the generated spray [31], is set to 230 and 640 µm.…”

Section: Investigated Fuel Injectormentioning

confidence: 99%

“…This sequence will be repeated with the following film wave reaching the trailing edge (Snapshot 5). Shadowgraphy images of the liquid breakup at the tip of a prefilming airblast atomizer, as studied by Gepperth et al [11,29,30], are depicted in Figure 7. The geometry is identical to that depicted in Figure 3 (left).…”

Section: Phenomena Observed During Breakupmentioning

confidence: 99%

See 4 more Smart Citations

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

et al. 2019

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The formation of pollutant emissions in jet engines is closely related to the fuel distribution inside the combustor. Hence, the characteristics of the spray formed during primary breakup are of major importance for an accurate prediction of the pollutant emissions. Currently, an Euler–Lagrangian approach for droplet transport in combination with combustion and pollutant formation models is used to predict the pollutant emissions. The missing element for predicting these emissions more accurately is well defined starting conditions for the liquid fuel droplets as they emerge from the fuel nozzle. Recently, it was demonstrated that the primary breakup can be predicted from first principles by the Lagrangian, mesh-free, Smoothed Particle Hydrodynamics (SPH) method. In the present work, 2D Direct Numerical Simulations (DNS) of a planar prefilming airblast atomizer using the SPH method are presented, which capture most of the breakup phenomena known from experiments. Strong links between the ligament breakup and the resulting spray in terms of droplet size, trajectory and velocity are demonstrated. The SPH predictions at elevated pressure conditions resemble quite well the effects observed in experiments. Significant interdependencies between droplet diameter, position and velocity are observed. This encourages to employ such multidimensional interdependence relations as a base for the development of primary atomization models.

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Section: Effect Of Gas Velocity and Prefilmer Geometry On The Spray Esupporting

confidence: 92%

Section: Relations Between Ligaments and Dropletssupporting

confidence: 91%

Section: Effect Of Gas Velocity and Prefilmer Geometry On The Spray Ementioning

confidence: 97%

Section: Investigated Fuel Injectormentioning

confidence: 99%

Section: Phenomena Observed During Breakupmentioning

confidence: 99%

See 3 more Smart Citations

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

et al. 2019

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Air-Film Coupling in Prefilming Airblast Atomisers and the Implications for Subsequent Atomisation

Wetherell,

Garmory

2024

Flow Turbulence Combust

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Prefilming airblast atomisers are commonly used in gas turbine combustion system fuel injectors. As the film propagates across the prefilmer it interacts with the high velocity gas stream above it. In this paper a numerical investigation into this interaction is presented. A Coupled Level Set & Volume of Fluid method is used to simulate the development of the film along the KIT-ITS planar prefilmer (Gepperth et al., in: 23rd European conference on liquid atomization and spray systems (ILASS-Europe 2010), Brno, Czech Republic, September, 2010). Initial results showed the importance of correctly specifying the contact angle as too high a value leads to the formation of rivulets instead of a continuous film. An analysis of the film and air showed two-way coupling. The presence of the film increases the growth rate of the gas phase boundary layer, and the strength and size of the turbulent structures within it. Surface waves form in the film, initially driven by the turbulent fluctuations, but developing into transverse waves. These waves are shown to be independent, stochastic events instead of a periodic wave system. At the trailing edge of the prefilmer the increased turbulence level in the air, the variations in the film thickness and the associated change in fuel mass flow and momentum will have large implications for the atomisation process and subsequent fuel spray. These will also impact simulation of the atomisation, as the boundary condition complexity is much greater than commonly used, and the variations will require larger domains and longer simulation times to obtain fully converged atomisation statistics.

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Euler–Lagrangian simulation of the fuel spray of a planar prefilming airblast atomizer

et al. 2021

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The pollutant emissions of aircraft engines are strongly affected by the fuel injection into the combustion chamber. Hence, the precise description of the fuel spray is required in order to predict these emissions more reliably. The characteristics of a spray is determined during the atomization process, especially during primary breakup in the vicinity of the atomizer nozzle. Currently, Euler-Lagrangian approaches are used to predict the droplet trajectories in combustor simulations along with reaction and pollutant formation models. To be able to reliably predict pollutant emissions in the future, well-defined starting conditions of the liquid fuel droplets close to the atomizer nozzle are necessary. In the present work, Euler-Lagrangian simulations of a generic airblast atomizer are presented. The starting conditions of the droplets are varied in the simulations by means of a primary breakup model, which takes into account the local gas velocity when predicting the droplet diameter. The objective of this work is to determine the optimal parameters of the probability density functions for the starting position and the starting velocity of the droplets. Spray properties observed in the simulations are used to qualitatively evaluate the major effects of the distribution parameters on the spray and the suitability of the primary breakup model being applied. Hence, the spatial distribution of an experimental spray can be reproduced using a statistical model for the droplet starting conditions.

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Influence of the ambient pressure on the liquid accumulation and on the primary spray in prefilming airblast atomization

Cited by 41 publications

References 40 publications

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

Air-Film Coupling in Prefilming Airblast Atomisers and the Implications for Subsequent Atomisation

Euler–Lagrangian simulation of the fuel spray of a planar prefilming airblast atomizer

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