Computational Simulations of Liquid Sprays in Crossflows with an Algorithmic Module for Primary Atomization

2020 ◽  
Author(s):  
Taewoo Lee ◽  
Benjamin Greenlee ◽  
Jung Eun Park ◽  
Hana Bellerova ◽  
Miroslav Raudensky
Keyword(s):  
Drop Size ◽  
Initial Conditions ◽  
Energy State ◽  
Integral Form ◽  
Computational Procedure ◽  
Fluid Simulation ◽  
Liquid Jets ◽  
Quadratic Formula ◽  
Initial Drop ◽  
Drop Size Distributions

Abstract For simulations of liquid jets in crossflows, the primary atomization can be treated with the quadratic formula, which has been derived from integral form of conservation equations of mass and energy in our previous work. This formula relates the drop size with the local kinetic energy state, so that local velocity data from the volume-of-fluid simulation prior to the atomization can be used to determine the initial drop size. This initial drop size, along with appropriately sampled local gas velocities, are used as the initial conditions in the dispersed-phase simulation. This procedure has been performed on a coarse-grid platform, with good validation and comparison with available experimental data at realistic Reynolds and Weber numbers, representative of gas-turbine combustor flows. The computational procedure produces all the relevant spray characteristics: spatial distributions of drop size, velocities, and volume fluxes, along with global drop size distributions. The primary atomization module is based on the conservation principles, and is generalizable and implementable to any combustor geometries for accurate and efficient computations of spray flows.

Computational Protocol for Spray Flow Simulations Including Primary Atomization

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
T.-W. Lee ◽  
B. Greenlee ◽  
J. E. Park
Keyword(s):  
Drop Size ◽  
Integral Form ◽  
Quadratic Formula ◽  
Flow Simulations ◽  
Initial Drop ◽  
Lagrangian Tracking ◽  
Droplet Liquid ◽  
Computational Protocol ◽  
Spray Flows

Abstract Primary atomization is the key element in spray flow simulations. We have, in our previous work, used and validated the integral form of the conservation equations, leading to the “quadratic formula” for determination of the drop size during spray atomization in various geometry. A computational protocol has been developed where this formulation is adapted to existing computational frameworks for continuous and dispersed (droplet) liquid phase, for simulations of pressure-atomized sprays with and without swirl. In principle, this protocol can be applied to any spray geometry, with appropriate modifications in the atomization criterion. The preatomization continuous liquid motion (e.g., liquid column or sheet) is computed using volume-of-fluid (VOF) or similar methods, then the velocity data from this computation is input to the quadratic formula for determination of the local drop size. This initial drop size, along with the local liquid velocities from VOF, is then used in a Lagrangian tracking algorithm for the postatomization dispersed droplet calculations. This protocol can be implemented on coarse-grid, time-averaged simulations of spray flows, and produces convincing results when compared with experimental data for pressure-atomized sprays with and without swirl. This approach is general, and can be adapted in any spray geometries for complete and efficient computations of spray flows.

Cubic Formula for Determination of the Drop Size During Atomization of Liquid Jets in Co- and Cross-Flow of Air

2018 ◽  
Author(s):  
T.-W. Lee ◽  
Jung Eun Park ◽  
Ryoichi Kurose
Keyword(s):  
Energy Balance ◽  
Kinetic Energy ◽  
Drop Size ◽  
Cross Flow ◽  
Liquid Jets ◽  
Initial Kinetic Energy ◽  
Practical Applications ◽  
Relevant Variables ◽  
Drop Size Distributions

Using the integral formulation of the conservation equations as in our previous work, we can determine the drop size and its distributions in liquid sprays in co- and cross flow of air. The energy balance dictates that the initial kinetic energy of the gas and injected liquid be distributed into the final surface tension energy, kinetic energy of the gas and droplets, and viscous dissipation incurred. The mass and energy balance for the spray flows render to an expression that relates the drop size to all of the relevant parameters, including the gas- and liquid-phase properties and velocities. The results agree well with experimental data and correlations for the drop size. The solution also provides for drop size-velocity cross-correlation, leading to drop size distributions based on the gas-phase velocity distributions. These aspects can be used in estimating the drop size for practical applications, in synthesizing the data as a function of relevant variables, and also in integration into CFD for atomization algorithm.

Initial Drop Size and Velocity Distributions for Airblast Coaxial Atomizers

1991 ◽  
Vol 113 (3) ◽  
pp. 453-459 ◽  
Author(s):  
H. Eroglu ◽  
N. Chigier
Keyword(s):  
Drop Size ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Mean Velocity ◽  
Supply Pressure ◽  
Double Peaks ◽  
Air Supply ◽  
Complete Disintegration ◽  
Initial Drop ◽  
And Behavior

Initial drop size and velocity distributions, after complete disintegration of coaxial liquid jets, were determined by phase Doppler measurements. The measured radial distributions of Sauter mean diameter (SMD) were compared with the photographs of the disintegrating liquid jet. The SMD distribution was found to be strongly affected by the structure and behavior of the preceding liquid intact jet. The results showed that SMD increases with increasing liquid supply pressure as well as with decreasing air supply pressure. The axial measurement stations were determined from the photographs of the coaxial liquid jet at very short distances (1–2 mm) downstream of the observed break-up locations. The droplets accelerated at these regions under the influence of the air velocity. Smaller droplets were found to reach higher velocities because of their larger drag-to-momentum ratio. In general, minimum droplet mean velocities were found at the center, and the maximum velocities were near the spray boundary. Size velocity correlations show that the velocity of larger drops did not change with drop size. Drop rms velocity distributions have double peaks whose radial positions coincide with the maximum mean velocity gradients.

Determination of the Drop Size During Air-Blast Atomization

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
T.-W. Lee ◽  
J. E. Park
Keyword(s):  
Kinetic Energy ◽  
Viscous Dissipation ◽  
High Speed ◽  
Drop Size ◽  
Integral Form ◽  
Initial Kinetic Energy ◽  
Air Blast ◽  
Dissipation Term ◽  
Wide Range ◽  
Drop Size Distributions

We have used the integral form of the conservation equations, to find a cubic formula for the drop size during in liquid sprays in coflow of air (air-blast atomization). Similar to our previous work, the energy balance dictates that the initial kinetic energy of the gas and injected liquid will be distributed into the final surface tension energy, kinetic energy of the gas and droplets, and viscous dissipation. Using this approach, the drop size can be determined based on the basic injection and fluid parameters for “air-blast” atomization, where the injected liquid is atomized by high-speed coflow of air. The viscous dissipation term is estimated using appropriate velocity and length scales of liquid–air coflow breakup. The mass and energy balances for the spray flows render to an expression that relates the drop size to all of the relevant parameters, including the gas- and liquid-phase velocities and fluid properties. The results agree well with experimental data and correlations for the drop size. The solution also provides for drop size–velocity cross-correlation, leading to computed drop size distributions based on the gas-phase velocity distribution. This approach can be used in the estimation of the drop size for practical sprays and also as a primary atomization module in computational simulations of air-blast atomization over a wide range of injection and fluid conditions, the only caveat being that a parameter to account for the viscous dissipation needs to be calibrated with a minimal set of observational data.

Break-up dynamics and drop size distributions created from spiralling liquid jets

2004 ◽  
Vol 30 (5) ◽  
pp. 499-520 ◽  
Author(s):  
D.C.Y. Wong ◽  
M.J.H. Simmons ◽  
S.P. Decent ◽  
E.I. Parau ◽  
A.C. King
Keyword(s):  
Drop Size ◽  
Liquid Jets ◽  
Size Distributions ◽  
Break Up ◽  
Drop Size Distributions

Capillary Breakup of a Liquid Jet With a Random Initial Perturbation

1977 ◽  
Vol 44 (3) ◽  
pp. 385-388 ◽  
Author(s):  
P. Lafrance ◽  
R. C. Ritter
Keyword(s):  
Drop Size ◽  
Random Noise ◽  
Initial Perturbation ◽  
Liquid Jets ◽  
Size Distributions ◽  
Capillary Breakup ◽  
Perturbation Mode ◽  
Mean Size ◽  
Drop Size Distributions ◽  
Two Peaks

Experiments were performed to measure the size of drops resulting from the capillary breakup of laminar liquid jets. Random noise was used to perturb the jet and an electro-optical instrument was used to measure drop sizes. Drop size distributions show two peaks as predicted by nonlinear theory. The large group has a mean size as predicted by the most unstable perturbation mode, in agreement with the commonly accepted but previously untested assumption.

scholarly journals The breakup of levitating water drops observed with a high speed camera

2011 ◽  
Vol 11 (19) ◽  
pp. 10205-10218 ◽  
Author(s):  
C. Emersic ◽  
P. J. Connolly
Keyword(s):  
Size Distribution ◽  
High Speed ◽  
Drop Size ◽  
Initial Conditions ◽  
Water Drop ◽  
Liquid Water Content ◽  
Drop Size Distribution ◽  
High Speed Camera ◽  
Size Distributions ◽  
Drop Size Distributions

Abstract. Collision-induced water drop breakup in a vertical wind tunnel was observed using a high speed camera for interactions between larger drop sizes (up to 7 mm diameter) than have previously been experimentally observed. Three distinct collisional breakup types were observed and the drop size distributions from each were analysed for comparison with predictions of fragment distributions from larger drops by two sets of established breakup parameterisations. The observations showed some similarities with both parameterisations but also some marked differences for the breakup types that could be compared, particularly for fragments 1 mm and smaller. Modifications to the parameterisations are suggested and examined. Presented is also currently the largest dataset of bag breakup distributions observed. Differences between this and other experimental research studies and modelling parameterisations, and the associated implications for interpreting results are discussed. Additionally, the stochastic coalescence and breakup equation was solved computationally using a breakup parameterisation, and the evolving drop-size distribution for a range of initial conditions was examined. Initial cloud liquid water content was found to have the greatest influence on the resulting distribution, whereas initial drop number was found to have relatively little influence. This may have implications when considering the effect of aerosol on cloud evolution, raindrop formation and resulting drop size distributions. Calculations presented show that, using an ideal initial cloud drop-size distribution, ~1–3% of the total fragments are contributed from collisional breakup between drops of 4 and 6 mm.

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