Publications
309 results found
Fredrich D, Jones WP, Marquis A, 2019, Thermo-acoustic instabilities in the PRECCINSTA combustor investigated using a compressible LES-pdf approach, 11th Mediterranean Combustion Symposium, Publisher: The Combustion Institute, Pages: 1-12
This work predicts the evolution of self-excited thermo-acoustic instabilities in a gas turbine model combustor using large eddy simulation. The developed flow solver is fully compressible and comprises a transported sub-grid probability density function approach in conjunction with the Eulerian stochastic fields method. An unstable operating condition in the PREC-CINSTA test case involving flame oscillation driven by thermo-acoustic instabilities is the chosen target configuration. Good results are obtained in a comparison of time-averaged flow statistics against experimental data. The flame’s self-excited oscillatory behaviour is successfully captured without any external forcing involved. Power spectral density analysis of the oscillation reveals a dominant thermo-acoustic mode at a frequency of 300 Hz providing remarkable agreement with experimental observations. Moreover, the predicted limit-cycle amplitude closely matches the experimental value obtained with rigid metal combustion chamber side walls. Finally, a phase-resolved study of the oscillation cycle is carried out leading to a detailed description of the physical mechanism closing the feedback loop.
Xia Y, Laera D, Jones WP, et al., 2019, Numerical prediction of the Flame Describing Function and thermoacoustic limit cycle for a pressurised gas turbine combustor, Combustion Science and Technology, Vol: 191, Pages: 979-1002, ISSN: 0010-2202
The forced flame responses in a pressurized gas turbine combustor are predicted using numerical reacting flow simulations. Two incompressible1 large eddy simulation solvers are used, applying two combustion models and two reaction schemes (4-step and 15-step) at two operating pressures (3 and 6 bar). Although the combustor flow field is little affected by these factors, the flame length and heat release rate are found to depend on combustion model, reaction scheme, and combustor pressure. The flame responses to an upstream velocity perturbation are used to construct the flame describing functions (FDFs). The FDFs exhibit smaller dependence on the combustion model and reaction chemistry than the flame shape and mean heat release rate. The FDFs are validated by predicting combustor thermoacoustic stability at 3 and 6 bar and, for the unstable 6 bar case, also by predicting the frequency and oscillation amplitude of the resulting limit cycle oscillation. All of these numerical predictions are in very good agreement with experimental measurements.
Chakraborty N, Navarro-Martinez S, Jones WP, et al., 2019, Special issue on UKCTRF workshop 2018 PREFACE, COMBUSTION SCIENCE AND TECHNOLOGY, Vol: 191, Pages: 745-746, ISSN: 0010-2202
Jones WP, Marquis AJ, Vogiatzaki K, 2019, Assessing the effect of differential diffusion for stratified lean premixed turbulent flames with the use of LES-PDF framework, Combustion Science and Technology, Vol: 191, Pages: 1003-1018, ISSN: 0010-2202
Lean premixed stratified combustion is rapidly growing in importance for modern engine designs. This paper presents large eddy simulations for a new burner design to assess the predictive capability of the probability density function (pdf) approach to flames that propagate through non-homogeneous mixtures in terms of equivalence ratio. Although various efforts have been made in the past for the simulation of the same test case the novelty of this work lies to the fact that it is the first simulation effort that differential diffusion is accounted for given the relatively low Reynolds numbers (13,800) of the configuration. First mean and root mean square velocity simulations are performed for the isothermal cases to assess the effect of the grid resolution and the overall LES flow field solver. Then instantaneous snapshots of the flame are presented to provide insight to the structure of the flame and the effect of stratification. Finally, results for velocities, temperature and mixture fraction are presented and compared with the experimental data. Overall, the results are in very good agreement with experiments.
Fredrich D, Jones W, Marquis A, 2019, LES-pdf simulation of combustion dynamics in a partially premixed swirl combustor, 9th European Combustion Meeting, Publisher: The Combustion Institute, Pages: 1-6
The dynamic behaviour of the partially premixed, swirl-stabilised PRECCINSTA gas turbine model combustor is studied using a fully compressible large eddy simulation solver with a 15-step and 19 species reduced methane mechanism. The solver applies a transported sub-grid probability density function approach solved by the Eulerian stochastic fields method to allow for a burning regime independent description of turbulent flames. A specific operating condition prone to self-excited thermo-acoustic and hydrodynamic instabilities is targeted to evaluate the predictive capabilities of the computational method. Excellent agreement with experimental data is obtained for the predicted thermo-acoustic mode representing a pronounced limit-cycle oscillation at the correct frequency and amplitude. Moreover, the periodic formation and suppression of a precessing vortex core is identified as well as periodic shedding of toroidal vortices at the burner nozzle rim. Both phenomena are shown to be directly coupled to the dominant thermo-acoustic mode and their respective interaction with the flame is investigated in further detail.
Fredrich D, Jones WP, Marquis AJ, 2019, Application of the Eulerian subgrid Probability Density Function method in the Large Eddy Simulation of a partially premixed swirl flame, Combustion Science and Technology, Vol: 191, Pages: 137-150, ISSN: 0010-2202
A gas turbine model combustor is studied using Large Eddy Simulation with a transported Probability Density Function approach solved by the Eulerian stochastic field method. The chemistry is represented by a reduced methane mechanism containing 15 steps and 19 species while the subgrid scale stresses and scalar fluxes are modelled, respectively, via a dynamic Smagorinsky model and a gradient diffusion approximation. The test case comprises a partially premixed swirl flame in a complex geometry. Four stochastic fields are utilised in the simulations, which are performed for two different combustor operating conditions involving a stable and an unstable flame. Good agreement between the simulation and measurement data is shown in a comparison of mean velocity, temperature and species mass fraction profiles, as well as scatter plots of the instantaneous thermochemical properties. In conclusion, the predictive capabilities of the employed Large Eddy Simulation method are successfully demonstrated in this work.
Noh D, Karlis E, Navarro-Martinez S, et al., 2019, Azimuthally-driven subharmonic thermoacoustic instabilities in a swirl-stabilised combustor, Proceedings of the Combustion Institute, Vol: 37, Pages: 5333-5341, ISSN: 0082-0784
A joint experimental and computational study of thermoacoustic instabilities in a model swirl-stabilised combustor is presented. This paper aims to deliver a better characterisation of such instabilities through the examination of measurements in conjunction with the numerical results obtained via Large Eddy Simulation (LES). The experimental configuration features a cylindrical combustion chamber where the lean premixed methane/air flame experiences self-sustained thermoacoustic oscillations. The nonlinear behaviour of the acoustically excited flame is experimentally investigated by broadband chemiluminescence and dynamic pressure measurements. In LES, the Eulerian stochastic field method is employed for the unknown turbulence/chemistry interaction of the gas-phase. Comparisons of the predicted frequency spectrum and phase-resolved flame structure with measurements are found to be in good agreement, confirming the predictive capabilities of the LES methodology. The presence of Period 2 thermoacoustic oscillations, as a consequence of period-doubling bifurcation, is also confirmed in LES. Through the application of nonlinear analysis both to the experimental and numerical acoustic fluctuations, it is highlighted that the nonlinear behaviour of combustion instabilities in the burner under investigation follows a pattern typical of Period 2 oscillations. Furthermore, the current work demonstrates a useful approach, through the use of dynamic mode decomposition (DMD), for the investigation of unstable flame modes at a specific frequency of interest. The experimental and numerical DMD reconstructions suggest that hot combustion products are convected azimuthally at a rate dictated by the subharmonic frequency.
Fredrich D, Jones WP, Marquis A, 2018, Large eddy simulation of an oscillating flame using the stochastic fields method, 12th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements, Pages: 1-6
Large eddy simulation (LES) of a partially pre-mixed, swirl-stabilised flame is performed using atransported Probability Density Function approachsolved by the stochastic fields method to accountfor turbulence-chemistry interaction on the sub-gridscales. The corresponding sub-grid stresses and scalarfluxes are modelled via a dynamic version of theSmagorinsky model and a gradient diffusion approx-imation, respectively.A 15-step reduced methanemechanism including 19 species is employed for thedescription of all chemical reactions. The test case in-volves a widely studied gas turbine model combustorwith complex geometry and the simulation is carriedout for a specific operating condition involving an os-cillating flame. Overall, results of the velocity, temper-ature and major species mass fractions as well as theinstantaneous thermochemical properties are shown tobe in good agreement with experimental data, demon-strating the capabilities of the applied stochastic fieldsmethod. The inclusion of wall heat transfer in the com-bustion chamber is found to improve temperature pre-dictions, especially in the near-wall regions. In sum-mary, this work showcases the LES method’s accuracyand robustness - none of the default model parametersare adjusted - for an application to complex, partiallypremixed combustion problems
Koniavitis P, Rigopoulos S, Jones W, 2018, Reduction of a detailed chemical mechanism for a kerosenesurrogate via RCCE-CSP, Combustion and Flame, Vol: 194, Pages: 85-106, ISSN: 0010-2180
Detailed mechanisms for kerosene surrogate fuels contain hundreds of species and thousands of reactions, indicating a necessity for reduced mechanisms. In this work, we employ a framework that combines Rate-Controlled Constrained Equilibrium (RCCE) with Computational Singular Perturbation (CSP) for systematic reduction based on timescale analysis, to reduce a detailed mechanism for a jet fuel surrogate with n-dodecane, methylcyclohexane and m-xylene. Laminar non-premixed flamelets are utilised for the CSP analysis for different strain rates and therefore different scalar dissipation rate, covering the flammable region of strain rates for the surrogate fuel.Two RCCE-reduced mechanisms are developed via an RCCE-CSP methodology, one with 17 and one with 42 species, and their accuracy is assessed in a range of cases that test the performance of the reduced mechanism under both non-premixed and premixed conditions and its dynamic response. These include non-premixed flamelets with varying strain rate, laminar premixed flames for a range of equivalence ratios and pressures, flamelets ignited by an artificial pilot or by hot air, and unsteady flamelets with time-dependent strain rate.The profiles of both major and minor species, as well as important combustion characteristics such as the ignition strain rate and the laminar flame speed, are investigated. The structure of non-premixed flamelets is very well predicted, while the premixed flames are overall well predicted apart from a few deviations in certain species and an underprediction in the laminar flame speed. Apart from the large reduction in dimensionality, the reduction in computational time is also considerable (up to 19 times). As the detailed mechanism comprises 367 species and 1892 reactions, this paper presents the first application of RCCE to a mechanism of this size, as well as a comprehensive validation in a set of cases that include non-premixed and premixed laminar flames, atmospheric and elevated pressur
Noh D, Gallot-Lavallée S, Jones WP, et al., 2018, Comparison of droplet evaporation models for a turbulent, non-swirling jet flame with a polydisperse droplet distribution, Combustion and Flame, Vol: 194, Pages: 135-151, ISSN: 0010-2180
The current investigation aims to present the numerical results of a turbulent spray jet flame in the framework of Large Eddy Simulation. The injection of n-heptane liquid fuel is achieved through the use of a pressure-swirl atomiser generating a lifted spray flame. The evolution of the sub-grid probability density function of relevant scalars is accounted for by the Eulerian stochastic field method. A non-reactive spray computation is conducted in a preliminary stage. The simulation allows for a stochastic breakup formulation in combination with a stochastic dispersion model to confirm their predictive capabilities. This is achieved as the liquid properties such as droplet diameter and velocity profiles are found to be in excellent agreement between the simulated results and measurements. The main target of the work is to assess the performance of the most widely accepted evaporation models in a turbulent droplet-laden flame. In this paper, a detailed comparison of the evaporation models is conducted thanks to a recent development in measurement techniques which allow to permit the spray temperature profiles. The time-averaged droplet temperature across the spray flame is therefore investigated in order to validate several droplet vaporisation models. All the models under consideration are found to capture the formation of a double reaction zone flame and the measured lift-off height is reproduced within a satisfactory level of accuracy. This good reproduction of the flame morphology additionally confirms the performance of the pdf approach as a closure for the unknown turbulence–chemistry interaction in this type of spray flames. However, the simulated wet-bulb temperature in the hot burnt gas between the two reaction zones in addition to the profile along the spr ay centreline show a large discrepancy when compared to measurements. This large difference thus requires further investigation both in the modelling of evaporation and in the accuracy of measureme
Xia Y, Laera D, Morgans AS, et al., 2018, Thermoacoustic limit cycle predictions of a pressurised longitudinal industrial gas turbine combustor, ASME Turbo Expo 2018, Publisher: American Society of Mechanical Engineers
Xia Y, Laera D, Morgans AS, et al., 2018, Thermoacoustic limit cycle predictions of a pressurised longitudinal industrial gas turbine combustor
This article presents numerical prediction of a thermoacoustic limit cycle in an industrial gas turbine combustor. The case corresponds to an experimental high pressure test rig equipped with the full-scale Siemens SGT-100 combustor operated at two mean pressure levels of 3 bar and 6 bar. The Flame Transfer Function (FTF) characterising the global unsteady response of the flame to velocity perturbations is obtained for both operating pressures by means of incompressible Large Eddy Simulations (LES). A linear stability analysis is then performed by coupling the FTFs with a wave-based low order thermoacoustic network solver. All the thermoacoustic modes predicted at 3 bar pressure are stable; whereas one of the modes at 6 bar is found to be unstable at a frequency of 231 Hz, which agrees with the experiments. A weakly nonlinear stability analysis is carried out by combining the Flame Describing Function (FDF) predicted by LES with the low order thermoacoustic network solver. The frequency, mode shape and velocity amplitude corresponding to the predicted limit cycle at 209 Hz are used to compute the absolute pressure fluctuation amplitude in the combustor. The numerically reconstructed amplitude is found to be reasonably close to the measured dynamics.
Jones WP, 2018, Professor Dudley Brian Spalding 1923-2016, Heat Transfer Engineering, Vol: 39, Pages: 316-317, ISSN: 0145-7632
Jones WP, marquis A, Noh D, 2017, An investigation of a turbulent spray flame using Large Eddy Simulation with a stochastic breakup model, Combustion and Flame, Vol: 186, Pages: 277-298, ISSN: 0010-2180
A computational investigation of a turbulent methanol/air spray flame in which a poly-dispersed droplet distribution is achieved through the use of a pressure-swirl atomiser (also known as a simplex atomiser) is presented. A previously formulated stochastic approach towards the modelling of the breakup of droplets in the context of Large Eddy Simulation (LES) is extended to simulate methanol/air flames arising from simplex atomisers. Such atomisers are frequently used to deliver fine droplet distributions in both industrial and laboratory configurations where they often operate under low-pressure drop conditions. The paper describes improvements to the breakup model that are necessary to correctly represent spray formation from simplex atomisers operated under low-pressure drop conditions. The revised breakup model, when used together with the existing stochastic models for droplet dispersion and evaporation, is shown to yield simulated results for a non-reacting spray that agree well with the experimentally measured droplet distribution, spray dynamics and size-velocity correlation. The sub-grid scale (sgs) probability density function (pdf) approach in conjunction with the Eulerian stochastic field method are employed to represent the unknown interaction between turbulence and chemistry at the sub-filter level while a comprehensive kinetics model for methanol oxidation with 18 chemical species and 84 elementary steps is used to account for the gas-phase reaction. A qualitative comparison of the simulated OH images to those obtained from planar laser-induced fluorescence (PLIF) confirms that the essential features of this turbulent spray flame are well captured using the pdf approach. They include the location of the leading-edge combustion (or lift-off height) and the formation of a double reaction zone due to the polydisperse spray. In addition, the influence of the spray flame on the structure of the reacting spray in respect of the mean droplet diameters and sp
Jones WF, Gosman AD, 2017, In Memoriam Professor Dudley Brian Spalding (1923-2016), Combustion and Flame, Vol: 185, Pages: A1-A3, ISSN: 0010-2180
Fredrich D, Jones WP, Marquis A, 2017, Application of the Eulerian sub-grid probability density function method in the large eddy simulation of a partially premixed swirl flame, 10th Mediterranean Combustion Symposium, Publisher: The Combustion Institute, Pages: 1-12
Large Eddy Simulations (LES) of a partially premixed, swirl-stabilised flame are performedusing a transported Probability Density Function (PDF) approach in combination with the Eu-lerian stochastic field method to account for turbulence-chemistry interaction. The correspond-ing subgrid scale (sgs) stresses and scalar fluxes are modelled using a dynamic version of theSmagorinsky model and a gradient diffusion approximation, respectively. A 15-step reducedmethane (CH4) mechanism containing 19 species is employed for the description of all chem-ical reactions. The test case involves a widely studied gas turbine model combustor with com-plex geometry. Simulations are carried out for two combustor operating conditions utilisingboth one and four stochastic fields. The overall velocity, temperature and major species massfraction results as well as the instantaneous thermochemical properties are shown to be in goodagreement with experimental measurement data demonstrating the capabilities of the employedLES method
Koniavitis P, Rigopoulos S, Jones WP, 2017, A methodology for derivation of RCCE-reduced mechanisms via CSP, Combustion and Flame, Vol: 183, Pages: 126-143, ISSN: 0010-2180
The development of reduced chemical mechanisms in a systematic way has emerged as a potential solution to the problem of incorporating the increasingly large chemical mechanisms into turbulent combustion CFD codes. In this work, a methodology is proposed for developing reduced mechanisms with Rate-Controlled Constrained Equilibrium (RCCE) via a Computational Singular Perturbation (CSP) analysis of counterflow non-premixed flamelets. An ordering of species for variable strain rates is derived by integrating over mixture fraction space a modified CSP pointer that depends on the timescale and mass fraction of each chemical species. Subsequently, a global set of kinetically controlled species is identified from weighting the local ordering for each strain rate. RCCE simulations with the derived reduced mechanisms for methane with 16 species and for propane with 27 species are compared with the integration of the detailed mechanisms GRI 1.2 and USC-Mech-II respectively. The applicability of the methodology is demonstrated in non-premixed flames for several strain rates, in non-premixed flames ignited with a pilot in order to test the dynamics and ignition of the reduced schemes, in premixed flames for different equivalence ratios and subsequently in perfectly stirred reactors for ignition delay times for varying temperature, pressure and equivalence ratio. Overall very good agreement is obtained, indicating that the methodology can produce reliable mechanisms for different fuels and for a wide range of conditions, including dynamical behaviour and conditions different from those employed for the derivation of the mechanism.
XIA Y, Morgans AS, Jones WP, et al., 2017, Predicting thermoacoustic instability in an industrial gas turbine combustor: combining a low-order network model with flame LES, ASME TURBO EXPO 2017, Publisher: ASME
The thermoacoustic modes of a full scale industrial gas turbine combustor have been predicted numerically. The predictive approach combines low order network modelling of the acoustic waves in a simplified geometry, with a weakly nonlinear flame describing function, obtained from incompressible large eddy simulations of the flame region under upstream forced velocity perturbations, incorporating reduced chemistry mechanisms. Two incompressible solvers, each employing different numbers of reduced chemistry mechanism steps, are used to simulate the turbulent reacting flowfield to predict the flame describing functions. The predictions differ slightly between reduced chemistry approximations, indicating the need for more involved chemistry. These are then incorporated into a low order thermoacoustic solver to predict thermoacoustic modes. For the combustor operating at two different pressures, most thermoacoustic modes are predicted to be stable, in agreement with the experiments. The predicted modal frequencies are in good agreement with the measurements, although some mismatches in the predicted modal growth rates and hence modal stabilities are observed. Overall, these findings lend confidence in this coupled approach for real industrial gas turbine combustors.
Noh D, Gallot Lavallee S, Jones WP, et al., 2017, Validation of droplet evaporation models for a polydisperse spray in a non-swirling jet flame, European Combustion Meeting 2017, Publisher: Combustion Institute
The present work aims to deliver a numerical investigation of the turbulent spray jet flame in the context of LargeEddy Simulation. Several droplet evaporation models are studied in order to confirm their predictive capabilities interms of the time-averaged droplet temperature in the two-phase reactive flow. All the models under considerationare found to capture the formation of a double reaction zone flame and the measured lift-off height within a goodlevel of accuracy. However, the simulated wet-bulb temperature in the hot burnt gas between the two reaction zonesis considerably higher in comparison to measurements. This large discrepancy thus requires a further investigation inthe evaporation modelling.
Fredrich D, Gallot-Lavallée S, Jones WP, et al., 2017, Large eddy simulation of a gas turbine model combustor using the Eulerian subgrid probability density function method, 8th European Combustion Meeting, Publisher: The Combustion Institute, Pages: 1803-1808
The Eulerian stochastic field method is applied to solve the subgrid Probability Density Function (PDF) accounting for turbulence-chemistry interaction in the Large Eddy Simulation (LES) of a swirl stabilised gas turbine model combustor. A dynamic version of the Smagorinsky model for the subgrid scale stresses and a gradient diffusion approximation for the scalar fluxes complete the formulation. The chemical reaction is described by a 15-step reduced CH4 mechanism involving 19 species. Velocity, temperature and species results as well as basic thermochemical properties are shown to be in good agreement with experimental data validating the capabilities of the employed LES method.
Gallot Lavallee S, Noh D, Jones WP, et al., 2017, Experimental and numerical study of turbulent flame structures of a spray jet flame, European Combustion Meeting, Publisher: Combustion Institute
The flame structure of a laboratory scale n-heptane spray flame is investigated experimentally and numerically. Theexperimental burner is an open chamber with an ambient temperature co-flow surrounding a hollow cone simplexatomiser. OH-PLIF measurements are performed to study the interaction between turbulence, droplets, and chemistry.The simulation is performed using a Large Eddy Simulation with combustion modelling included by means of thesolution of the transport of the joint-sgsprobability density function using the stochastic fields method with promisingresults.
Gong Y, Gallot Lavallee S, Jones WP, 2017, Large eddy simulation of an opposed jet turbulent flame, European Combustion Meeting 2017, Publisher: Combustion Institute
A Large Eddy Simulation (LES) of a turbulent premixed flame in a counter-flow configuration is performed.This burner is a benchmark for the analysis of turbulent flames with particularly the turbulence-chemistryinteraction. In the simulations combustion is modelled by means of the evolution of the joint sub-grid-scale(sgs) probability density function. The solution of the transport equation for the scalars is obtained by thestochastic field method. The results presented are a comparison with the experimental data for a reactingand non reacting case and they include axial and radial velocities as well as OH plots.
Xia Y, Morgans A, Jones W, et al., 2017, SIMULATING FLAME RESPONSE TO ACOUSTIC EXCITATION FOR AN INDUSTRIAL GAS TURBINE COMBUSTOR, The 24th International Congress on Sound & Vibration (ICSV24)
Xia Y, Morgans AS, Jones WP, et al., 2017, Predicting thermoacoustic instability in an industrial gas turbine combustor: Combining a low order network model with flame LES, ASME Turbo Expo 2017
Copyright © 2017 ASME and Siemens AG. The thermoacoustic modes of a full scale industrial gas turbine combustor have been predicted numerically. The predictive approach combines low order network modelling of the acoustic waves in a simplified geometry, with a weakly nonlinear flame describing function, obtained from incompressible large eddy simulations of the flame region under upstream forced velocity perturbations, incorporating reduced chemistry mechanisms. Two incompressible solvers, each employing different numbers of reduced chemistry mechanism steps, are used to simulate the turbulent reacting flowfield to predict the flame describing functions. The predictions differ slightly between reduced chemistry approximations, indicating the need for more involved chemistry. These are then incorporated into a low order thermoacoustic solver to predict thermoacoustic modes. For the combustor operating at two different pressures, most thermoacoustic modes are predicted to be stable, in agreement with the experiments. The predicted modal frequencies are in good agreement with the measurements, although some mismatches in the predicted modal growth rates and hence modal stabilities are observed. Overall, these findings lend confidence in this coupled approach for real industrial gas turbine combustors.
Gallot Lavallee S, Jones WP, Biagioli F, et al., 2016, Stochastic fields method applied to turbulent swirling flames with acoustic perturbations, 11th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements
Jones WP, Marquis AJ, Noh D, 2016, A stochastic breakup model for Large Eddy Simulation of a turbulent two-phase reactive flow, Proceedings of the Combustion Institute, Vol: 36, Pages: 2559-2566, ISSN: 1873-2704
The current work presents numerical investigations of model burner in which a non-swirling air-assisted methanol spray is injected using a pressure-swirl atomiser. A stochastic breakup model is formulated in the context of Large Eddy Simulation (LES) and validated by detailed comparisons of the results with measurements. An excellent agreement is achieved for the non-reactive case in terms of the dispersion of the spray, the mean droplet distributions and the time-averaged spray velocities. The transported probability density function (pdf) equation/Eulerian stochastic field method are used to represent the interaction of turbulence and chemistry while the gas phase reaction of the methanol/air spray flame is described by a reduced reaction mechanism involving 18 chemical species and 84 elementary steps. The sub-grid scale (sgs) chemistry model in conjunction with the formulated breakup model are found to capture the influence of the flame on droplet dynamics together with the formation of a double reaction zone typically resulting from a polydisperse spray to a good accuracy.
Gallot-Lavallee S, Jones WP, Marquis AJ, 2016, Large Eddy Simulation of an ethanol spray flame under MILD combustion with the stochastic fields method, Proceedings of the Combustion Institute, Vol: 36, Pages: 2577-2584, ISSN: 1540-7489
A combustion device operating in Moderate or Intense Low-oxygen Dilution (MILD) condition is numerically simulated. The burner consists of a cylindrical hot co-flow generator with an injector installed on the central axis. The hot co-flow is obtained by the lean combustion of Dutch Natural Gas (DNG). The spray is injected through an industrial pressure swirl atomiser using liquid ethanol as fuel. MILD combustion consists in burning the fuel in a high temperature environment so that the temperature gradients are limited and the production of pollutants such as NOx reduced. MILD combustion has been investigated for furnace applications and for various gaseous fuels, recently it has also been explored for spray combustion. The simulation is performed in the context of Large Eddy Simulation (LES) and the transported pdf equation for the scalars is solved using the stochastic fields approach. The validation of the results is based on the comparison with experimental data. The characteristics of the injector are obtained a posteriori by the use of the measurements at downstream location. The simulation correctly reproduces the velocity profiles of the particles within their size classes and the integral particle size distribution which is represented by the Sauter Mean Diameter (SMD). The gas phase temperature and velocity are also in good agreement with the measurements, however, some discrepancies are observed, presumably because of the lack of modelling of primary atomisation. The model employed appears to reliably reproduce the behaviour of the spray combustion system under MILD conditions.
Cheng H, Xie Z, Jones WP, et al., 2016, Preclinical Pharmacokinetics Study of R- and S-Enantiomers of the Histone Deacetylase Inhibitor, AR-42 (NSC 731438), in Rodents, AAPS JOURNAL, Vol: 18, Pages: 737-745, ISSN: 1550-7416
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Xia Y, Morgans A, Jones WP, et al., 2016, Combining low order network modelling with incompressible flame LES for thermoacoustic instability in an industrial gas turbine combustor, Joint meeting of the British, Portuguese and Spanish Sections of the Combustion Institute
Brauner T, Jones WP, Marquis AJ, 2016, LES of the Cambridge Stratified Swirl Burner using a Sub-grid pdf Approach, 9th Mediterranean Combustion Symposium, Publisher: Springer Verlag, Pages: 965-985, ISSN: 1573-1987
The sub-grid scale probability density function equation is rearranged in order to separate the resolved and sub-grid-scale (sgs) contributions to the sgs mixing term. This allows modelling that is consistent with the limiting case of negligible sub-grid scale variations, a property required for applications to laboratory premixed flames. The new method is applied to the Cambridge Stratified Swirl Burner for 6 operating conditions, 2 isothermal and 4 burning, with varying degrees of swirl and mixture stratification. The simulations are performed with the Large Eddy Simulation (LES) code BOFFIN in which the modelled pdf transport equation is solved using the Eulerian stochastic field method. Eight stochastic fields are used to account for the influence of the sub-grid fluctuations and the chemistry is modelled with a reduced version of the GRI 3.0 mechanism for methane involving 19 species and 15 reaction steps. The simulated velocities for both the isothermal and burning cases show good agreement with the experimental data. The measured temperature and major species profiles are also reproduced to a good accuracy.
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