Development Of Gas Turbine Combustors Research Articles

Numerical Study of Radiation and Fuel–Air Unmixedness on the Performance of a Dry Low NOx Combustor

Abstract The development of gas turbine combustors is expected to consider the effects of radiation heat transfer in modeling. However, this is not always the case in many studies that neglect this for adiabatic conditions. The effect of radiation is substantiated here, concerning the impact on the performance, mainly the emissions. Also, the fuel–air unmixedness (mixing quality) influenced by the combustor design and operational settings has been investigated with regard to the emissions. The work was conducted with a Mitsubishi-type dry low NOx combustor developed and validated against experimental data. This 3D computational fluid dynamics study was implemented using Reynolds-averaged Navier Stokes simulation and the radiative transfer equation model. It shows that NO, CO, and combustor outlet temperature reduce when the radiative effect is considered. The reductions are 17.6% and below 1% for the others, respectively. Thus, indicating a significant effect on NO. For unmixedness across the combustor in a non-reacting simulation, the mixing quality shows a direct relationship with the turbulence kinetic energy (TKE) in the reacting case. The most significant improvements in unmixedness are shown around the main burner. Also, the baseload shows better mixing, higher TKE, and lower emissions (particularly NO) at the combustor outlet, compared to part-load.

On integrated experimentation and simulation of a counter-turning swirling mixer, part I: Experimentation

Success in developing advanced combustor concepts relies significantly on achieving rapid and uniform mixing of fuel with combustion air through a fuel/air preparation device called mixer. To guide the design and development of gas turbine combustor expeditiously, detailed understanding of the flow characteristics and performance of a mixer of interest is essential. Leveraging recent advances in computational fluid dynamics (CFD) and diagnostic techniques, a series of studies have been initiated to develop and calibrate best practices on integrated experimentation and simulation for two generic families of mixers, namely for lean-direct injection and rich-dome combustors. Here, a set of three papers have been prepared to summarize our research activities on a mixer relevant to rich-dome combustors. This Part I paper presents the method by which a high-quality Time-Resolved Particle Image Velocimetry (TR-PIV) two-dimensional velocity dataset is established for a counter-turning multi-swirlers (CTS) mixer. The non-reacting flow field characteristics at 3% pressure drop across this CTS mixer are quantified by collecting more than 10,000 image pairs captured and processed via a high-accuracy sub-pixel adaptive correlation algorithm. Mean and root-mean-square velocity profiles are presented along with quantification of critical flow structure metrics. Proper Orthogonal Deconvolution structure analysis is also presented for the dominant modes. A full description of the uncertainty analysis of the TR-PIV velocity data is further provided, as is a detailed convergence study. The dataset is determined to be of sufficient quality to be used for quantitatively anchoring CFD simulations as summarized in our two companion papers Part II (Reynolds-Averaged Navier-Stokes models) and Part III (Large Eddy Simulation).

Modeling gaseous non-reactive flow in a lean direct injection gas turbine combustor through an advanced mesh control strategy

Fuel efficiency improvement and harmful emissions reduction are the main motivations for the development of gas turbine combustors. Numerical computational fluid dynamics (CFD) simulations of these devices are usually computationally expensive since they imply a multi-scale problem. In this work, gaseous non-reactive unsteady Reynolds-Averaged Navier–Stokes and large eddy simulations of a gaseous-fueled radial-swirled lean direct injection combustor have been carried out through CONVERGE™ CFD code by solving the complete inlet flow path through the swirl vanes and the combustor. The geometry considered is the gaseous configuration of the CORIA lean direct injection combustor, for which detailed measurements are available. The emphasis of the work is placed on the demonstration of the CONVERGE™ applicability to the multi-scale gas turbine engines field and the determination of an optimal mesh strategy through several grid control tools (i.e., local refinement, adaptive mesh refinement) allowing the exploitation of its automatic mesh generation against traditional fixed mesh approaches. For this purpose, the normalized mean square error has been adopted to quantify the accuracy of turbulent numerical statistics regarding the agreement with the experimental database. Furthermore, the focus of the work is to study the behavior when coupling several large eddy simulation sub-grid scale models (i.e., Smagorinsky, Dynamic Smagorinsky, and Dynamic Structure) with the adaptive mesh refinement algorithm through the evaluation of its specific performances and predictive capabilities in resolving the spatial-temporal scales and the intrinsically unsteady flow structures generated within the combustor. This investigation on the main non-reacting swirling flow characteristics inside the combustor provides a suitable background for further studies on combustion instability mechanisms.

Effect of the physical properties of liquid and ALR on the spray characteristics of a pre-filming airblast nozzle

Abstact The atomization and combustion characteristics of fuels injected in aviation gas turbine engines are very important in the research and development of gas turbine combustors and have a significant impact on engine efficiency and pollutant emissions. In this study, spray atomization characteristics of pre-filming airblast nozzles developed for use in aviation gas turbine combustors were experimentally investigated for different air to liquid ratios (ALR) and air pressure differences (ΔP (%)). Pure water and Jet A-1, which have different viscosities and surface tensions that greatly affect the atomization characteristics, were used as the working fluid. Spray atomization characteristics were investigated by simultaneous measurement of droplet sizes and velocities using PDA (phase Doppler anemometry) and spray visualization using a CCD camera coupled with a Nd:YAG laser as a light source. The atomization characteristics of water and Jet A-1 showed significant differences in spray angle, velocity distribution and mean droplet size. Jet A-1 spray with lower surface tension showed a smaller mean drop size (WMSMD) than water spray did. As the ALR increased, the mean droplet size of the two liquids decreased. From the analysis of the spray flow characteristics, the surface tension associated with aerodynamic instability was the dominant variable in the atomization process with liquid sheet disintegration. The experimental constants included in the previously proposed empirical formulas for predicting the mean droplet size of the pre-filming airblast nozzle spray were presented for the two liquids used in the experiment.

Measurements of the reactivity of premixed, stagnation, methane-air flames at gas turbine relevant pressures

The adiabatic, unstrained, laminar flame speed, SL, is a fundamental combustion property, and a premier target for the development and validation of thermochemical mechanisms. It is one of the leading parameters determining the turbulent flame speed, the flame position in burners and combustors, and the occurrence of transient phenomena, such as flashback and blowout. At pressures relevant to gas turbine engines, SL is generally extracted from the continuous expansion of a spherical reaction front in a combustion bomb. However, independent measurements obtained in different types of apparatuses are required to fully constrain thermochemical mechanisms. Here, a jet-wall, stagnation burner designed for operation at gas turbine relevant conditions is presented, and used to assess the reactivity of premixed, lean-to-rich, methane–air flames at pressures up to 16 atm. One-dimensional (1D) profiles of axial velocity are obtained on the centerline axis of the burner using particle tracking velocimetry, and compared to quasi-1D flame simulations performed with a selection of thermochemical mechanisms available in the literature. Significant discrepancies are observed between the numerical and experimental data, and among the predictions of the mechanisms. This motivates further chemical modeling efforts, and implies that designers in industry must carefully select the mechanisms employed for the development of gas turbine combustors.

Practical Application of Combustion Simulation to Development of Gas Turbine Combustor

Practical Application of Combustion Simulation to Development of Gas Turbine Combustor

RANS NUMERICAL SIMULATION OF LEAN PREMIXED BLUFF BODY STABILIZED COMBUSTOR: COMPARISON OF TURBULENCE MODELS

Many gas turbine combustors use bluff-body flameholders to enhance mixing and maintain flame stabilization inside the combustor. Computational Fluid Dynamics (CFD) can greatly help in the design and development of gas turbine combustors. In this regard, CFD analyses using k-e and Reynold Stress Model (RSM) approaches are being evaluated through simulating the combustion processes inside a bluff body stabilized gas turbine combustor where a mixture of lean premixed methane-air are burnt. The numerical study is performed under a steady state condition utilizing the commercial software ANSYS-FLUENT. The simulated results are compared with available experimental data as well as published simulation results found in the literature. The results are presented and compared in terms of velocity fields, temperature profiles and species distributions. The results show that both adopted turbulence models k-e and RSM reasonably made a well predictions of the combustion process with such kind of combustor, especially k-e turbulence model.

Subgrid Model Influence in Large Eddy Simulations of Non-reacting Flow in a Gas Turbine Combustor

Fuel efficiency improvement and harmful emission reduction are the paramount driving forces for development of gas turbine combustors. Lean-burn combustors can accomplish these goals, but require specific flow topologies to overcome their sensitivity to combustion instabilities. Large Eddy Simulations (LES) can accurately capture these complex and intrinsically unsteady flow fields, but estimating the appropriate numerical resolution and subgrid model(s) still remain challenges. This paper discusses the prediction of non-reacting flow fields in the DLR gas turbine model combustor using LES. Several important features of modern gas turbine combustors are present in this model combustor: multiple air swirlers and recirculation zones for flame stabilisation. Good overall agreement is obtained between LES outcomes and experimental results, both in terms of time-averaged and temporal RMS values. Findings of this study include a strong dependence of the opening angle of the swirling jet inside the combustion chamber on the subgrid viscosity, which acts mainly through the air mass flow split between the two swirlers in the DLR model combustor. This paper illustrates the ability of LES to obtain accurate flow field predictions in complex gas turbine combustors making use of open-source software and computational resources available to industry.

Large-Eddy Simulation of a Reacting Jet in Cross Flow With NOx Prediction

The reduction of full and part load emissions and the increase of the turndown ratio are important goals for gas turbine combustor development. Combustion techniques, which generate lower NOx emissions than unstaged premixed combustion in the full load range, and which have the potential of reducing minimum load while complying with emission legislation, are of high technical interest. Therefore, axial-staged combustion systems have been designed, either with or without expansion in a turbine stage between both stages. In its simpler form without intermediate expansion stage, a flow of hot combustion products is generated in the first stage of the premixed combustor, which interacts with the jets of premixed gas injected into the second stage. The level of NOx formation during combustion of the premixed jets in the hot cross flow determines the advantage of axially staged combustion regarding full load NOx emission reduction. Employing large-eddy simulation in openfoam, a tool has been developed, which allows to investigate staged combustion systems including not only temperature distribution but also NOx emissions under engine conditions. To be able to compute NOx formation correctly, the combustion process has to be captured with sufficient level of accuracy. This is achieved by the partially stirred reactor model. It is combined with a newly developed NOx model, which is a combination of a tabulation technique for the NOx source term based on mixture fraction and progress variable and a partial equilibrium approach. The NOx model is successfully validated with generic burner stabilized flame data and with measurements from a large-scale reacting jet in cross flow experiment. The new NOx model is finally used to compute a reacting jet in cross flow under engine conditions to investigate the NOx formation of staged combustion in detail. The comparison between the atmospheric and the pressurized configuration gives valuable insight in the NOx formation process. It can be shown that the NOx formation within a reacting jet in cross flow configuration is reduced and not only diluted.

On the Use of Thermoacoustic Analysis for Robust Burner Design

Advanced thermoacoustic analysis is now routinely used in gas turbine combustor development. A thermoacoustic approach based on a combination of numerical analysis (CFD and three-dimensional acoustics), acoustic network models, and dedicated measurements of acoustic flame response is well accepted across the industry. However, its application to specific combustor upgrade or development programs in “prediction mode” as opposed to “analysis mode” remains a challenge. This is mainly due to the large sensitivity of the complex methodology to key inputs, such as flame transfer functions, that can be only predicted in the burner design phase. This paper discusses an example where we made an effort to apply the thermoacoustic approach in predictive mode. The example refers to the upgrade of a first generation diffusion burner with a partially premix burner to achieve low emissions. Thermoacoustic instabilities were predicted as a limiting factor for combustor operation and thus a design parameter was identified to perform the thermoacoustic combustor tuning at engine level. A particular challenge of this development program was that no test rig was available. Therefore, the new premix burner was directly installed into a field engine where it was successfully tested.

Development of Gas Turbine Combustor for Each Gasified Fuel and prospect of high-efficiency generation of various resources

Development of Gas Turbine Combustor for Each Gasified Fuel and prospect of high-efficiency generation of various resources

Development of Gas Turbine Combustor for Utilizing Various Gasified Fuels with High-Efficiency and Minimal Pollutant Emissions

Development of Gas Turbine Combustor for Utilizing Various Gasified Fuels with High-Efficiency and Minimal Pollutant Emissions

Gas Turbine Combustor Development for Gasified Fuels and Environmental High-efficiency Utilization of Unused Resources

わが国では一次エネルギー資源の約8割を海外からの輸入に依存している。将来にわたるエネルギーの安定供給ならびに地球環境負荷低減の観点から，新たな未利用エネルギー資源の開拓および高効率利用技術の開発が今後ますます重要となる。 未利用一次エネルギーのうちビチューメン，オイルシェール等の超重質油資源の究極可採埋蔵量は約5.8兆バレルと言われており，現在市場で取引される原油の可採埋蔵量の数倍に相当する。しかも，その貯留層は比較的政情の安定した中南米および北米に分布しており，発電用燃料としての有効活用はエネルギー資源の発掘，電力の安定供給力確保の観点から重要である。わが国の電気事業では，超重質油等を高効率ガスタービンで利用する技術として，ガス化•ガス精製技術の開発に取り組むとともに，ガスタービン燃焼器技術の開発を実施してきた。特に，ガスタービンに供給されるガス化燃料は，ガス化方式によって大幅に異なり，それぞれに適した燃焼器技術が必要になる。 本論文では，ガス化燃料用ガスタービン燃焼器技術について，開発の背景および海外における研究および開発の動向を概説するとともに，電気事業において開発された各種ガス化燃料用ガスタービン燃焼器技術について詳説する。

ガス化燃料用ガスタービン燃焼器の技術開発と 様々な未利用資源の高効率利用

ガス化燃料用ガスタービン燃焼器の技術開発と 様々な未利用資源の高効率利用

Application of Turbulent Reacting Flow Analysis in Gas Turbine Combustor Development

Developing a low NOX gas turbine combustor usually requires many experiments on flow and combustion. Computational prediction technology in the field of combustion has progressed with advances in computer technology and turbulent combustion models. This report covers applications of CFD for the development of the gas turbine combustor and some discrepancies between CFD and test results as well as improved methods for resolving such discrepancies.

Application of Turbulent Reacting Flow Analysis for Gas Turbine Combustor Development.

Application of Turbulent Reacting Flow Analysis for Gas Turbine Combustor Development.

2309 ガスタービン用燃焼器開発における CFD の有効性

2309 ガスタービン用燃焼器開発における CFD の有効性

97/03092 Development of gas turbine combustor fed with bio-fuel oil

Gas turbine combined-cycle systems burning natural gas represent a reliable and efficient power generation technology that is widely used. A critical factor in their development was the rapid adaptation of aero-engine technology (single crystal airfoils, sophisticated cooling techniques, and thermal barrier coatings) in order to operate at the high rotor-inlet temperatures required for high efficiency generation. Early reliability problems have been largely overcome, so that this type of power generation system is now considered to be a mature technology capable of achieving high levels of availability. Current interest in replacing natural gas with gas derived from coal (syngas or hydrogen) in these gas turbine systems focuses attention on implications for the critical turbine components. In this paper, the development requirements for materials for critical hot gas-path parts in large gas turbines burning coal-derived syngas fuels are briefly considered in the context of the state-of-the-art in materials for engines burning natural gas. It is shown that, despite some difficult design issues, many of the materials used in current engines will be applicable to units burning syngas. However, there is the potential that the durability of some components may be prejudiced because of differences in the combustion environment (especially in terms of water vapor content, and possibly sulfur compounds and particulates). Consequently, effort to develop improved coatings to resist erosion and also attack by S-containing compounds may be necessary.

Model for airblast atomization

The objective of fuel injection modeling activities is generally to give support to the atomizer design effort to achieve improved spray quality. In gas turbine combustors, enhanced atomization is essential for satisfactory performance because droplet sizes can have direct impact on almost all key aspects of combustion. A model that includes the integration of the submodels of airflow, fuel injection and atomization, and droplets turbulent dispersion has been formulated. The model was applied to an airblast atomizer that incorporated a short prefilming device. The predictions were validated against two-component phase Doppler interferometry data of that atomizer. The results of the present investigation demonstrate the capability of the developed model to predict satisfactorily the airflow field and spray characteristics. The results also indicate the need for detailed measurements in the near field of the atomizer in order to quantitatively verify the modeling of the initial atomization processes in this region. CD d FN g P t U u V P a Nomenclature = drag coefficient = droplet diameter, m = atomizer flow number, m2 = gravitational acceleration, m/s2 = kinetic energy of turbulence, m2/s2 = static pressure, Pa = film thickness, m = velocity of carrier phase, m/s = fluctuation velocity of carrier phase, m/s = velocity of droplets, m/s = axial distance, m = dynamic viscosity, kg/ms = density, kg/m3 = surface tension, N/m I. Introduction T HE development of gas turbine combustors depends largely upon understanding the flow and combustion processes within the combustor. In order to accurately simulate the combustor flowfield, analytical approaches are required to account for various flow processes in addition to the details of the combustor configuration. It is equally important to establish a wide base of benchmark quality data needed for model validation. Most of the combustor performance parameters are directly related to the quality of the spray produced by the fuel injector.l The initial drop sizes formed at the injector exit and their trajectories coupled with the combustor primary zone aerodynamics significantly influence the evaporation and combustion characteristics of the spray. Fuel injection calculation concepts currently in use include empirical methods that readily provide a global picture of the whole spray as well as more complex models that account for the detailed spray dynamics.2'3 Spray correlations provide a convenient means of calculating such parameters as mean drop size and spray angle. However, it is difficult to develop a design method based only on empirical data because each correlation was derived for a certain application and may not

Modeling Parameter Influences in Gas Turbine Combustor Design

Complementary to the lengthy and costly experimental approach to gas turbine combustor development is the theoretical approach. In order to advance the combustor design process, a computer program is needed which starts from hypotheses about the fundamental processes and predicts the distributions of velocity, concentrations, and temperature. Consideration is given in this paper to recent work in the development and application of a primitive-variable finite-differ ence solution procedure for turbulent, reacting, swirling, recirculating flows in axisymmetric combustors. The principal interest is on application of the analysis to gas turbine combustors and on demonstration of the utility and predictive capability of the code as an aid in combustor design.