Download or read book Prediction of Soot Particles in Gas Turbine Combustors Using Large Eddy Simulation written by Lucien Gallen (docteur en physique).) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expected stringent legislation on particulate matter (PM) emission by gas turbine combustors is currently motivating considerable efforts to be better understand, model and predict soot formation. This complex phenomenon is very difficult to study in detail with experiment, and numerical simulation is an essential complementary tool. Considering that the chemistry of soot particles strongly depends on their size, the numerical prediction of soot formation requires the description of their size distribution. To do so, either Eulerian methods (sectional or moments) or stochastic Lagrangian approaches are reported in the literature. In the present work, a far more simple semi-deterministic Lagrangian approach is proposed. An accurate description of the gaseous phase including first Polycyclic Aromatic Hydrocarbons is also developed as a necessary input to detail soot model. The combination of reduced chemistries with Lagrangian soot tracking is applied to canonical laminar sooting flames, later to two complex configurations representative of an aeronautical combustors. The first one is the FIRST configuration, a gaseous confined pressurized swirled flame studied experimentally at DLR. Impact of precursors species and radiative transfers through the resolution of Radiative Transfer Equation (RTE). Good predictions are obtained compared to experiments for predicted temperature and soot volume fraction. The second target configuration is the UTIAS Jet A-1 burner and corresponds to a confined turbulent spray flame burning aviation jet fuel A-1 studied experimentally at UTIAS Toronto. LES of this configuration provides a qualitative and quantitative understanding of soot evolution in turbulent spray flames. Numerical predicted soot volume fraction using Lagrangian soot tracking and an ARC mechanism including pyrolysis method is compared to experimental measurements. Results show the ability of the proposed methodology relying on ARC chemistry for Jet A-1 including pyrolysis method and Lagrangian soot tracking, to predict accurately soot compared to available measurements.

Download or read book Large Eddy Simulation Subgrid Model for Soot Prediction written by Hossam Abd El-Raouf Mostafa El-Asrag and published by . This book was released on 2007 with total page 261 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the current study, a new soot formation subgrid model is developed and reported here. The new model is designed to be used within the context of the Large Eddy Simulation (LES) framework, combined with Linear Eddy Mixing (LEM) as a subgrid combustion model. The final model can be applied equally to premixed and non-premixed flames over any required geometry and flow conditions in the free, the transition, and the continuum regimes.

Download or read book Fundamentals of Soot Formation in Gas Turbine Combustors written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental facility for studying soot formation in high temperature, fuel-rich, laminar, premixed flames has been constructed. Diagnostics included laser absorption, thermocouple particle densitometry, and thermophoretic soot sampling with analysis by transmission electron microscopy. Single particles with diameters as small as 3-5 nanometers were observed. Larger particles (20-25 nanometers) agglomerated to form large clusters. A coflow, axisymmetric, laminar ethylene diffusion flame has been studied, both experimentally and computationally. A lifted flame has been selected to eliminate possible uncertainties caused by the burner lip. A two-dimensional, detailed soot growth model in which the equations for particle production are coupled to the flow and gaseous species conservation equations has been used to investigate soot production in the flame. Detailed transport and finite rate chemistry in the gas phase was coupled with the particle aerosol equations in the sectional representation. In comparison to measured data obtained using intrusive and non- intrusive diagnostics, the model predicted temperature, flame height, and major species very well. Peak benzene concentrations and soot volume fraction were predicted to within 20% of the experimental value. The predicted distribution of benzene was excellent, but the soot was underpredicted along the centerline. This deficit was attributed to limitations in the PAH growth model. Oxidation of particulates was dominated by reactions with hydroxyl radical at superequilibrium levels. Radiation losses significantly effected predicted temperatures.

Download or read book Emissions Predictions in Turbulent Reacting Industrial Gas Turbine Combustor Flows Using RANS and LES Methods written by Sandeep Ebenezer Jella and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Large Eddy Simulation of Soot Evolution in Turbulent Reacting Flows written by Michael Edward Mueller and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot particles are nanoparticles consisting primarily of carbon that are formed during the combustion of fuel-rich mixtures. Due to environmental and health concerns, soot emissions from combustion systems are tightly regulated, and this regulation will only become stricter in the future. To enable the design of the next generation of low-emission combustion systems, predictive numerical simulations will be required. However, soot is a particularly difficult modeling problem due to the needs for high-fidelity models for soot itself in addition to chemistry and turbulence. This dissertation seeks to develop an integrated modeling framework based on Large Eddy Simulation (LES) for soot evolution in turbulent reacting flows. The final objective is the demonstration and evaluation of the model in an actual aircraft combustor. In order to enable these high-fidelity simulations, three component models have been developed. First, a detailed soot model is developed within the framework of the Method of Moments. New models for soot aggregation and fragmentation are proposed, and closure of the moment source terms is achieved with the Hybrid Method of Moments (HMOM), an accurate yet computationally efficient method. Second, a new turbulent combustion model is developed based on the Radiation Flamelet/Progress Variable (RFPV) model that can account for the removal of precursors from the gas-phase to form soot particles. Third, a subfilter PDF model is developed to account for the unresolved small-scale interactions between soot, turbulence, and chemistry. The subfilter PDF approach is validated a priori against a recent DNS database of soot evolution in a turbulent nonpremixed flame. The integrated modeling approach is then validated against experimental measurements in two laboratory-scale turbulent nonpremixed flames: a natural gas piloted jet flame and an ethylene bluff body flame. Differences in soot evolution due to the differences in the large-scale mixing in the two flames are discussed. The validated model is then applied to the simulation of a Pratt & Whitney aircraft combustor. Two operating points are simulated to assess the ability of the integrated model to reproduce quantitative trends in soot emissions.

Download or read book Large eddy Simulations of Combustion in Gas Turbine Combustors written by S. Menon and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling and Simulation of Turbulent Combustion written by Santanu De and published by Springer. This book was released on 2017-12-12 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of state-of-the-art models for turbulent combustion, with special emphasis on the theory, development and applications of combustion models in practical combustion systems. It simplifies the complex multi-scale and nonlinear interaction between chemistry and turbulence to allow a broader audience to understand the modeling and numerical simulations of turbulent combustion, which remains at the forefront of research due to its industrial relevance. Further, the book provides a holistic view by covering a diverse range of basic and advanced topics—from the fundamentals of turbulence–chemistry interactions, role of high-performance computing in combustion simulations, and optimization and reduction techniques for chemical kinetics, to state-of-the-art modeling strategies for turbulent premixed and nonpremixed combustion and their applications in engineering contexts.

Download or read book Large Eddy Simulations of a Reverse Flow Combustion System written by Jeffrey Spencer and published by . This book was released on 2012 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Next generation gas turbines will be required to produce low concentrations of pollutants such as oxides of nitrogen (NOx), carbon monoxide (CO), and soot. In order to design gas turbines which produce lower emissions it is essential to have computational tools to help designers. Over the past few decades, computational fluid dynamics (CFD) has played a key role in the design of turbomachinary and will be heavily relied upon for the design of future components. In order to design components with the least amount of experimental rig testing, the ensemble of submodels used in simulations must be known to accurately predict the component's performance. The present work aims to validate a CFD model used for a reverse flow, rich-burn, quick quench, lean-burn combustor being developed at Honeywell. Initially, simulations are performed to establish a baseline which will help to assess impact to combustor performance made by changing CFD models. Rig test data from Honeywell is compared to these baseline simulation results. Reynolds averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) turbulence models are both used with the presumption that the LES turbulence model will better predict combustor performance. One specific model, the fuel spray model, is evaluated next. Experimental data of the fuel spray in an isolated environment is used to evaluate models for the fuel spray and a new, simpler approach for inputting the spray boundary conditions (BC) in the combustor is developed. The combustor is simulated once more to evaluate changes from the new fuel spray boundary conditions. This CFD model is then used in a predictive simulation of eight other combustor configurations. All computer simulations in this work were preformed with the commercial CFD software ANSYS FLUENT. NOx pollutant emissions are predicted reasonably well across the range of configurations tested using the RANS turbulence model. However, in LES, significant under predictions are seen. Causes of the under prediction in NOx concentrations are investigated. Temperature metrics at the exit of the combustor, however, are seen to be better predicted with LES.

Download or read book Large Eddy Simulation for Heat Transfer Prediction in a Gas Turbine Environment written by Sanjiva Keshava Lele and published by . This book was released on 2007 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: A thorough investigation of leading edge heat transfer on a model geometry has been performed using Large-eddy simulation (LES). with support from the current and a previous AFOSR grant. The results from the leading edge study are presented as a detailed Appendix in this report. To address the problem of solving the full three-dimensional turbulent flow in a turbine passage. including the effects of free-stream turbulence from the combustor, and the unsteady interactions between various blade rows in the form of moving wakes and shocks it was necessary to extend the LES solver. A high-order overset LES code suitable for the study of turbomachinery passages has been developed. This approach is summarized in this report. Some preliminary results have been obtained using this code, mostly as cases for code validation. The code is currently being used to investigate flow in turbine passages under realistic conditions, and detailed comparisons with available experiments will be made.

Download or read book Large Eddy Simulation of Gas Turbine Combustors Using Flamelet Manifold Methods written by Christopher Fernandez Lietz and published by . This book was released on 2015 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objective of this work was to develop a large-eddy simulation (LES) based computational tool for application to both premixed and non- premixed combustion of low-Mach number flows in gas turbines. In the recent past, LES methodology has emerged as a viable tool for modeling turbulent combustion. LES is particularly well-suited for the compu- tation of large scale mixing, which provides a firm starting point for the small scale models which describe the reaction processes. Even models developed in the context of Reynolds averaged Navier-Stokes (RANS) exhibit superior results in the LES framework. Although LES is a widespread topic of research, in industrial applications it is often seen as a less attractive option than RANS, which is computationally inexpensive and often returns sufficiently accurate results. However, there are many commonly encountered problems for which RANS is unsuitable. This work is geared towards such instances, with a solver developed for use in unsteady reacting flows on unstructured grids. The work is divided into two sections. First, a robust CFD solver for a generalized incompressible, reacting flow configuration is developed. The computational algorithm, which com- bines elements of the low-Mach number approximation and pressure projection methods with other techniques, is described. Coupled to the flow solver is a combustion model based on the flamelet progress variable approach (FPVA), adapted to current applications. Modifications which promote stability and accuracy in the context of unstructured meshes are also implemented. Second, the LES methodology is used to study three specific problems. The first is a channel geometry with a lean premixed hydrogen mixture, in which the unsteady flashback phenomenon is induced. DNS run in tandem is used for establishing the validity of the LES. The second problem is a swirling gas turbine combustor, which extends the channel flashback study to a more practical application with stratified premixed methane and hydrogen/methane mixtures. Experimental results are used for comparison. Finally, the third problem tests the solver's abilities further, using a more complex fuel JP-8, Lagrangian fuel droplets, and a complicated geometry. In this last configu- ration, experimental results validate early simulations while later simulations examine the physics of reacting sprays under high centripetal loading.

Download or read book Large Eddy Simulation of Combustion Inside a Tubular Gas Turbine Combustor written by Ziyang Liew and published by . This book was released on 2007 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Massively parallel Spectral Element Large Eddy Simulation of a Ring type Gas Turbine Combustor written by Joshua Lane Camp and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The average and fluctuating components in a model ring-type gas turbine combustor are characterized using a Large Eddy Simulation at a Reynolds number of 11,000, based on the bulk velocity and the mean channel height. A spatial filter is applied to the incompressible Navier-Stokes equations, and a high pass filtered Smagorinsky model is used to model the sub-grid scales. Two cases are studied: one with only the swirler inlet active, and one with a single row of dilution jets activated, operating at a momentum flux ratio J of 100. The goal of both of these studies is to validate the capabilities of the solver NEK5000 to resolve important flow features inherent to gas turbine combustors by comparing qualitatively to the work of Jakirlic. Both cases show strong evidence of the Precessing Vortex Core, an essential flow feature in gas turbine combustors. Each case captures other important flow characteristics, such as corner eddies, and in general predicts bulk flow movements well. However, the simulations performed quite poorly in terms of predicting turbulence shear stress quantities. Difficulties in properly emulating the turbulent velocity entering the combustor for the swirl, as well as mesh quality concerns, may have skewed the results. Overall, though small length scale quantities were not accurately captured, the large scale quantities were, and this stress test on the HPF LES model will be built upon in future work that looks at more complex combustors.

Download or read book Soot Production in a Tubular Gas Turbine Combustor written by and published by . This book was released on 1901 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Soot production in gas turbine combustors is not desirable since it is the major source of exhaust smoke emission and its thermal radiation to the combustor liner deteriorates the liner durability. Soot formation involves comparatively slow chemistry and equilibrium can not be applied to soot modelling in the combustor flow field. . The exact sooting process in the combustor is poorly understood given both the complexity and the limited experimental data available. The work reported in this thesis seeks to first develop in-situ techniques for retrieving spatially-resolved soot properties, mainly soot particle volume fraction, from within the combustor and also to apply the measured results to comparisons with predicted soot concentrations. Two probing methods have been demonstrated which also incorporate a laser absorption technique. The sight probe proves to be more reliable in the present measurements. The evaluation of the physical probing techniques in sooty laboratory flames reveals that the flame structure will not be substantially distorted by the probe. The disturbance caused by the probe is localised, a feature which is evident in the reported water flow visualization test. The necessary inert gas purge can be minimised to reduce the local aerodynamic perturbation. The measured soot volume fraction distributions are comparable with sooting levels reported in flame studies in the literature. The peak soot volume fractions are located off-axis, characteristic of the fuel atornization. The measurementsin the primary zone are restricted by the multi-phase character of the flow, where soot absorption can not be readily discriminated from fuel droplet scattering. Measurements are reported over a range of air-fuel ratios, inlet pressures and temperatures. Time-averageds calard istributionsa t the nominald ilution sectionh ave beeno btained in addition to the soot measuremenut sing probe sampling and standard gas analysis. Correlationso f carbond ioxide with mixtur.

Download or read book Large Eddy Simulations of Bluff Body Stabilized Turbulent Flames and Gas Turbine Combustors written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper presents applications of the large eddy simulation (LES) methodology on the Sandia/Sydney turbulent bluf)body burner and gas turbine combustors. LES of the bluffbody flame is performed using the filtered density function (FDF) submodel and a comprehensive augmented chemical mechanism for the first time. The FDF submodel is a sophisticated turbulent-combustion submodel that directly computes the joint probability density function (PDF) of scalars and is therefore considered to be more accurate than conventional assumed-PDF type models. The chemical kinetics mechanism involves 19 species and 15 reaction-steps. The mechanism contains both C1 and C2 species and also involves NO formation steps. Owing to the complexity of the mechanism, numerical integration of the kinetics equations is peiformed using the in situ adaptive tabulation (ISAT) scheme. Mean velocity and species/temperature fields are presented and compared to experimental data. Results show that the computations are in good agreement with data. The paper also presents LES of a gas turbine combustor. LES is performed using an assumed FDF turbulent-combustion model in conjunction with the flamelet-generated manifold method. The advantage of this approach is that the chemical reaction is parameterized by only two variables, mixture fraction and progress variable. Thus calculations are signzficantlv faster than those with the transport FDF model. Circumftrentially averaged combustor exit fuel-air ratio profiles are compared to measurement data for two liner port patterns. It is shown that the LES calculations are in reasonable agreement with data and superior to Reynolds averaged Navier-Stokes calculations. These calculations indicate that LES of practical combustion systems are feasible economically and can be used for design analyses more routinely.

Download or read book Determination of Primary zone Smoke Concentrations from Spectral Radiance Measurements in Gas Turbine Combustors written by Carl T. Norgren and published by . This book was released on 1971 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The smoke concentration within the primary zone of an experimental combustor operating at pressures up to 20 atmospheres was determined with a technique using spectral radiance measurements. Exhaust smoke concentration was obtained from reflectance readings of stained filter paper. The primary zone smoke concentration was of the order of 100 to 1000 times greater than at the exhaust. The smoke oxidation rate obtained is compared with reported values for coal particles and seeded laboratory flames. Primary zone smoke concentration was shown to be related to exhaust smoke number and total radiance.

Download or read book Large eddy Simulation of Single cup Gas turbine Combustor Flows written by V. Sankaran and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Predicton of Combustion Driven Dynamic Instability for High Performance Gas Turbine Combustors written by B. Sekar and published by . This book was released on 2001 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes the development and application of a combined detailed three-dimensional large eddy simulation (LES) and one-dimensional analysis tool to predict and actively control combustion-driven dynamic instabilities in gas turbine combustors. The integration of detailed finite-rate kinetics into LES and use of In-situ Adaptive Tabulation (ISAT) to efficiently calculate multi-species finite-rate kinetics in LES along with the use of global kinetics in the one-dimensional analysis tool was demonstrated. The results showed that LES can be effectively used to simulate complex reacting flows in gas turbine combustors and to identify regions of combustion instabilities. The results also showed that the one-dimensional combustor analysis with global kinetics can then be used both to capture the combustor unstable modes of the predicted regions of instabilities and to actively control these instabilities. In particular, the results demonstrated that by modulating the primary fuel injection rates and the time-lag between the instant of fuel-air mixture injection and heat release, damping out the instabilities may be achieved.