Numerical and experimental investigation on droplet dynamics and dispersion of a jet engine injector

Keller, J.; Gebretsadik, Mulubrhan; Habisreuther, Peter; Turrini, Fabio; Zarzalis, Nikolaos; Trimis, D.

doi:10.1016/j.ijmultiphaseflow.2015.05.004

Cited by 19 publications

(12 citation statements)

References 32 publications

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“…This leads to the conclusion that reaction takes place in this area, which is influenced by the motion of the PVC. This is in agreement with the calculations of Keller et al 43 who investigated the interaction of the spray and the PVC by Large Eddy Simulation (LES). A clear difference exists between the spectra of OH* radiation and the ion current.…”

Section: Ion Current and Fast Temperature Measurementssupporting

confidence: 92%

“…The maxima marked by f PVC are the frequencies of the PVC as observed by velocity measurements by laser-Doppler anemometry (LDA) performed by Marinov et al 42 LES calculations by Keller et al are consistent with the experimental findings relating to the PVC. 43 In Figure 7 Figure 7(a) and (b) vanishes for the combined measurement and the first eigenfrequency around 340 Hz is coupled with the flow field, which in return causes a dependency of velocity. Figure 7(d) displays the spectra for the case of stable combustion.…”

Section: Frequency Analysismentioning

confidence: 98%

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Experimental investigations of ion current in liquid-fuelled gas turbine combustors

Wollgarten

Zarzalis

Turrini³

et al. 2017

International Journal of Spray and Combustion Dynamics

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This work covers investigations of the static and dynamic behaviour of a confined, co-swirled and liquid-fuelled airblast injection system. The focus lies on the application of ion current sensors for the qualitative measurement of the heat release rate or for flame monitoring purposes in complex technical combustion processes. The ion current sensor is to operate in a feedback control loop in order to react on combustion dynamics in real time. The first part of the work analyses experimental data, which were obtained with different techniques, e.g. dynamic pressure, chemiluminescence, fine-wire thermocouples and ion current. The results show that the thermo-acoustic instability and the precessing vortex core generate an interaction mode. The frequency of this interaction mode is the difference of the other two modes. This has not yet been observed for partially premixed and liquid-fuelled injection systems before and also was not detected by the chemiluminescence of the flame. The ion current measurement technique is able to detect the helical mode of the precessing vortex core as well as the interaction frequency, leading to the conclusion that the chemical reactions are influenced by this helical structure. Contour maps of the frequencies reveal this influence in the outer shear layer. The second part of the study focused on the ion current probe as a method to predict static combustion instabilities, such as lean blowout. According to the results, the ion current is a fast responding method to detect lean blowout, provided that the detector is mounted at a suitable position. Measurements at different positions in the flame were compared with phase-locked chemiluminescence measurements. Precursors in the ion current signal for lean-blowout prediction were found using a statistical approach, which is based on ion peak distance. The precursor events allow for the use of this approach with a feedback control loop in future applications.

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Section: Ion Current and Fast Temperature Measurementssupporting

confidence: 92%

Section: Frequency Analysismentioning

confidence: 98%

Experimental investigations of ion current in liquid-fuelled gas turbine combustors

Wollgarten

Zarzalis

Turrini³

et al. 2017

International Journal of Spray and Combustion Dynamics

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“…In recent Euler-Lagrangian simulations of aero-engine combustion chambers, different methodologies have been used to set the droplet starting conditions. The initial droplet diameters are usually computed using drop size distributions [3][4][5][6][7][8][9], which are derived by primary atomization models. Those correlations are mostly derived from measurements downstream from the injection location.…”

Section: Introductionmentioning

confidence: 99%

“…Those correlations are mostly derived from measurements downstream from the injection location. Due to the annular shape of the injector nozzle, the droplets are assumed to be injected at multiple discrete injection points equally distributed on a circle [6,8]. The position of the circle downstream from the injector nozzle is selected to fit experimental data.…”

Section: Introductionmentioning

confidence: 99%

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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“…Kvasnak et al [8] included the effect of droplet deformation and breakup to their models. Recent advances for using Eulerian-Lagrangian approach for spray modelling was reported by Kolakaluri et al [9], Keller et al [10], and Doisneau et al [11], among others. Hoyas et al [12] performed two-dimensional Eulerian-Lagrangian spray simulations in the near-nozzle region.…”

Section: Introductionmentioning

confidence: 99%

A Model for Fuel Spray Formation with Atomizing Air

Schmidt

Kvasnak

Ahmadi

2019

Fluids

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The formation of a liquid spray emanating from a nozzle in the presence of atomizing air was studied using a computational model approach that accounted for the deformation and break up of droplets. Particular attention was given to the formation of sprays under non-swirling flow conditions. The instantaneous fluctuating fluid velocity and velocity gradient components were evaluated with the use of a probability density function (PDF)-based Langevin equation. Motions of atomized fuel droplets were analyzed, and ensemble and time averaging were used for evaluating the statistical properties of the spray. Effects of shape change of droplets, and their breakup, as well as evaporation, were included in the model. The simulation results showed that the mean-square fluctuation velocities of the droplets vary significantly with their size and shape. Furthermore, the mean-square fluctuation velocities of the evaporating droplet differed somewhat from non-evaporating droplets. Droplet turbulence diffusivities, however, were found to be close to the diffusivity of fluid point particles. The droplet velocity, concentration, and size of the simulated spray were compared with the experimental data and reasonable agreement was found. Fluids 2019, 4, 20 2 of 17 Earlier, McDonell and Samuelsen [22] provided experimental data on droplet size and velocity distributions in a simplex atomizer. Kvasnak et al. [8] examined the formation of liquid sprays in the absence of atomizing air. Their analysis included effects of primary breakup for liquid ellipsoidal droplets based on the Taylor Analogy Breakup (TAB) model developed by O'Rourke and Amsden [23], and later modified by Ibrahim [24], and Kvasnak and Ahmadi [25]. Recent reviews of the spray simulation and breakup methods were presented by Jenny et al. [5].This work was concerned with understanding the effects of droplet deformation, breakup, and evaporation on the dispersion of deforming ellipsoidal spray droplets in turbulent fuel injector flow fields with atomizing air, with a focus towards practical applications. The other goal was to develop a computational tool for the simulation of practical liquid spray fuel injectors. Kvasnak et al. [8] described a detailed numerical procedure for generating ensembles of simultaneous sample particle trajectories for estimating particle velocity and dispersion statistics. The presented study showed that, in many cases of practical importance to fuel injectors with atomizing air, the deformation time scale of the fuel droplets was comparable with their evaporation time scale. The droplet nonsphericity was also found to be an important factor for modeling the fuel injector performance. The simulation results were compared with the experimental data of McDonell and Samuelsen [22] for a simplex atomizer with atomizing air, where qualitative agreement was found.

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Numerical and experimental investigation on droplet dynamics and dispersion of a jet engine injector

Cited by 19 publications

References 32 publications

Experimental investigations of ion current in liquid-fuelled gas turbine combustors

Experimental investigations of ion current in liquid-fuelled gas turbine combustors

Close Nozzle Spray Characteristics of a Prefilming Airblast Atomizer

A Model for Fuel Spray Formation with Atomizing Air

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