Experimental study of local flame structures and fuel droplet properties of a spray jet flame

Verdier, Antoine; Santiago, Javier Marrero; Vandel, Alexis; Saengkaew, Sawitree; Cabot, Gilles; Gréhan, Gérard; Renou, Bruno

doi:10.1016/j.proci.2016.07.016

Cited by 57 publications

(37 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The flames have been measured at the University of Sydney and have been modelled by many labs. Recent additions are the Rouen flame [123] and a recirculating spray flame from University of Cambridge [124], where various datasets focusing on extinction are available [125]. Here, discussions on atomisation models are necessarily prominent, so the participants to this workshop must also learn about twophase flow.…”

Section: Turbulent Premixed Flames [39]: There Is Less Strong Coordinmentioning

confidence: 99%

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Giusti

Mastorakos

2019

Flow Turbulence Combust

View full text Add to dashboard Cite

The development of better laser-based experimental methods and the fast rise in computer power has created an unprecedented shift in turbulent combustion research. The range of species and quantities measured and the advent of kHz-level planar diagnostics are now providing great insights in important phenomena and applications such as local and global extinction, pollutants, and spray combustion that were hitherto unavailable. In simulations, the shift to LES allows better representation of the turbulent flow in complex geometries, but despite the fact that the grid size is smaller than in RANS, the push towards realistic conditions and the need to include more detailed chemistry that includes very fast species and thin reaction zones emphasize the necessity of a sub-grid turbulent combustion model. The paper discusses examples from current research with experiments and modelling that focus on flame transients (self-excited oscillations, local extinction), sprays, soot emissions, and on practical applications. These demonstrate how current models are being validated by experimental data and the concerted efforts the community is taking to promote the modelling tools to industry. In addition, the various coordinated International Workshops on non-premixed, premixed, and spray flames, and on soot are discussed and some of their target flames are explored. These comprise flames that are relatively simple to describe from a fluid mechanics perspective but contain difficult-to-model combustion problems such as extinction, pollutants and multi-mode reaction zones. Recently, swirl spray flames, which are more representative of industrial devices, have been added to the target flames. Typically, good agreement is found with LES and some combustion models such as the progress variable-mixture fraction flamelet model, the Conditional Moment Closure, and the Transported PDF method, but predicting soot emissions and the condition of complete extinction in complex geometries is still elusive.

show abstract

Section: Turbulent Premixed Flames [39]: There Is Less Strong Coordinmentioning

confidence: 99%

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Giusti

Mastorakos

2019

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…The test case studied in the present work is a lifted heptane spray jet flame open to the atmosphere. The burner is described in Refs [33,34,35]. It consists Refractometry Technique (GRT) [33,34] and simultaneous high-speed OH-PLIF and high-speed Particle Image Velocimetry (PIV) [35].…”

Section: Test Casementioning

confidence: 99%

“…The LES-DCMC model is employed to simulate a spray jet flame recently studied experimentally [33,34,35]. This test flame has already been simu-65 lated using: LES with the Thickened Flame Model in the limit of a resolved flame [33], LES with the Stochastic Fields Method [36], LES with Filtered Tabulated Chemistry [37] and RANS with Flamelet Generated Manifolds [38].…”

Section: Introductionmentioning

confidence: 99%

“…Profiles of mean diameter, droplet temperature and droplet velocity from LES (blue line) compared to PDA[33] and GRT[34] measurements (symbols) for four axial locations.Error bars represent the RMS value from LES and experiment at a given location (no RMS was available for GRT measurements). Black dotted lines indicate the mean gas velocity and mean gas temperature in the respective graphs.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Large Eddy Simulation of a spray jet flame using Doubly Conditional Moment Closure

Sitte

Mastorakos

2019

Combustion and Flame

View full text Add to dashboard Cite

A spray jet flame is modelled using Large Eddy Simulation (LES) with Doubly Conditional Moment Closure (DCMC). Since turbulent spray flames may include multiple combustion modes, the DCMC model uses both mixture fraction and reaction progress variable as conditioning variables. Conditional spray terms were included in the DCMC model to consider the coupling between evaporation and the flame structure. In the case of spatial homogeneity and in the limit of negligible mixture fraction scalar dissipation rate (SDR), the DCMC equation is shown to reproduce the flame structure of freely propagating laminar flames. For the spray jet flame, a good agreement between the simulation results and the experiments is achieved, in terms of the spray statistics, as well as the instantaneous and mean flame shape. The simulation shows important differences in the flame structure between the turbulent inner and the quasilaminar outer flame branch. The doubly-conditional parametrisation appears to be advantageous for resolving small scale effects related to droplet evaporation. Analysis of the DCMC equation suggests that the behaviour of the flame at its anchoring point is strongly influenced by non-premixed burning modes. The solution appears to be weakly affected by terms of convective transport in the DCMC equation, but significant spatial variations and temporal fluctuations of the conditional reaction rate, around 10 % of the time-based mean, persist. the effect of temperature inhomogeneity on ignition [24] and have so far demonstrated a great potential of the modelling approach for predicting complex, transient combustion phenomena. To the knowledge of the authors, the only simulation of a lab-scale flame using DCMC, coupled with a Reynolds-Averaged Navier Stokes (RANS) computation, has been performed by Sitte and Mas-50 torakos [25]. From a broader perspective, the strategy of double-conditioning has also been recently employed in the CMC-related modelling approach of Conditional Source-term Estimation (CSE) [26].In this work, we present an application of the LES-DCMC approach, based on mixture fraction and reaction progress variable as conditioning variables. 55This allows parametrisation of the whole range from non-premixed to fully premixed flames. Moreover, the effect of liquid droplet evaporation on the flame structure is considered by modelling the spray terms in conditional space. Inclusion of conditional evaporation terms in the model equation is challenging and

show abstract

“…Experiments are carried out in a swirled version of the CORIA Rouen Spray Burner [10,11], confined with quartz windows in order to allow full optical access (Fig.1). The system is composed of a simplex pressure atomizer (Danfoss, 1.46 kgh -1 , 80° hollow cone) and an external annular swirling air co-flow with an inner and outer diameter of 10 and 20 mm respectively.…”

Section: Facilitymentioning

confidence: 99%

Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

Santiago

Verdier

Vandel³

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

Self Cite

View full text Add to dashboard Cite

Laser ignition was investigated in the swirled, confined CORIA Rouen Spray Burner under ultra-lean conditions (=0.61) with n-heptane as the liquid fuel. Ignition probability was calculated for different spark locations and compared to the non-ignited local flow properties. Mean velocity components of the carrier flow were measured by PDA under spray presence and without spray, and are compared to mean values from PIV. PIV measurements provide information on the instantaneous airflow and the total strain rate. Fuel droplet size-velocity data was measured by PDA. Toluene-PLIF images were acquired to provide information on the local equivalence ratio and the flammability factor. Results show that the outer recirculation zone (ORZ) has a flammability factor close to 1 and the highest ignition probability (~80%). These results have a high correlation with the air velocity field and turbulent kinetic energy. Instantaneous equivalence ratio images and shear rate-velocity fields give important information on local segregation of the flow properties that help to understand the ignition process. The present work provides a useful database for numerical simulations and industry, plus new insight on spray ignition. KeywordsSpray ignition, PDA, PIV, Toluene PLIF, Ignition probability, Local flow properties. IntroductionThe ignition process in gas turbines involves a wide range of parameters which makes it a multi-physical complex problem. New aeronautical burner designs demand a better knowledge of the mechanisms here involved to assure, for instance, re-ignition in high altitude of lean-combustion engines. Real combustors work with two-phase flows with strongly varying local properties. Indeed, turbulence, flow velocity, droplet size and velocity, and fuel vapour repartition are parameters governing the ignition mechanisms. Several studies on spray ignition [1-3] have been carried out. Studies on spray ignition in industrial configurations are still scarce although some pioneer experiments and simulations in linear [4,5] and annular combustors [6,7] have been done. Investigations on the influence of parameters such as turbulence [8, 9] also exist. The knowledge is still not sufficient to identify and understand the real mechanisms of ignition. More experiments are also needed to validate numerical simulations. Ignition in aeronautical engines can be divided into four steps: (i) energy deposition through a spark and its evolution into a flame kernel; (ii) kernel propagation; (iii) flame stabilisation on one injector; (iv) injector-to-injector propagation of the flame. Sometimes one of these phases is not successful and leads to a missed ignition. Even with a sufficient energy supply at phase (i), phase (ii) appears to be a critical step, namely in lean conditions. During its propagation in the chamber, the flame kernel will be exposed to varying local properties of the flow that may be adverse for its survival. This depends on both, the initial location of the kernel (spark location) and on its subsequent trajectory...

show abstract

Experimental study of local flame structures and fuel droplet properties of a spray jet flame

Cited by 57 publications

References 21 publications

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Turbulent Combustion Modelling and Experiments: Recent Trends and Developments

Large Eddy Simulation of a spray jet flame using Doubly Conditional Moment Closure

Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis

Contact Info

Product

Resources

About