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PDF/CFD - Based methods: development and validation for low emissions combustor technology

Objectif

This Focused Fundamental Research project is aimed at developing and validating PDF/CFD based methods for low emission combustors. Combustion sub-models currently in use by the gas-turbine manufacturer CFD codes do not incorporate finite rate chemical kinetics effects. While these codes yield good results for high power near-stoichiometric combustion they are unsuitable for predicting CO and unburnt hydrocarbon emissions at idle conditions and NOx formation in lean premixed high pressure ratio systems. PDF transport methods, integrated within a conventional CFD flow solver, are a rational framework to study these processes. Detailed chemical kinetics for higher hydrocarbons will be systematically reduced to a few significant steps and reactive species as the required input to the PDF methodology. PDF Monte-Carlo CFD solutions will be validated by comparison with both intrusive and non-intrusive measurements.

The objectives of the project are:

- To devise strategies integrating PDF and CFD based methods for accurate prediction of emission levels of CO, unburnt hydrocarbons and nitrogen oxides for Gas Turbine (GT) combustion chambers.
- To provide detailed and systematically reduced chemical kinetics mechanisms for higher hydrocarbon combustion at conditions typical of GT operation.
- To demonstrate and supply advanced scalar molecular mixing models.
- To develop efficient Monte-Carlo (MC) solution algorithms and implement them on massively parallel machines.
- To obtain experimental data for code validation with intrusive and laser-based combustion diagnostic techniques.
Detailed chemical kinetics mechanisms for n-heptane, n-decane, n-dodecane and n-cetane have been automatically generated with a computer code and validated for autoignition delay times. The hydrocarbon mechanisms have been modified to correctly predict CHi (i = 1, 2, 3) radicals, to be included in the NO reduction reburning process. The intrinsic low-dimensional manifold (ILDM) method has been used to reduce detailed chemical schemes to two and three-step chemistry involving only a few significant thermochemical variable; predictions, with detailed and reduced chemistries, of species evolutions is well reproduced with a few variables.

Molecular mixing models (LMSE, Curl's, Langevin and mapping closures, linear eddy model) have been demonstrated for statistically homogeneous incompressible turbulent reacting flows and applied in the Monte Carlo simulation of turbulent jet premixed and nonpremixed flames. This PDF Monte Carlo solution has been coupled with conventional CFD flow solvers to predict the velocity field. Kappa - Epsilon and second-order closure turbulence models have been tested. Efficient lookup table interpolation schemes have been developed for the treatment of the chemistry with particle methods. The feasibility and quantification of algorithm parallelization has also been explored.

Experimental data for code validation have been obtained for simple turbulent jet methane/air and propane/air nonpremixed flames with conventional diagnostic techniques. A model sector combustor has also been studied. Planar LIF measurements have been conducted in a quartz-sided combustor and in a methane/air counterflow jet partially-premixed flame; PFF (parent fuel fraction), OH, NO, and CO have been diagnosed.
The project is structured in six principal research tasks:

- Chemical kinetics studies on detailed and systematically-reduced mechanisms for the combustion of higher hydrocarbons, including NOx formation, at atmospheric pressure, at idle conditions and at high pressure ratios typical of gas turbine operation.
- Development and demonstration of molecular mixing models capable of taking the existence of thin reaction zones into account and capable of correctly predicting ignition/extinction phenomena and yielding the correct asymptotic behaviour when compared with DNS (Direct Numerical Simulation) results.
- Development and validation of efficient Monte-Carlo simulation algorithms including look up table interpolation schemes, implementation on conventional von Newman computers and on massively parallel machines and predictions for simple combustion flows.
- Integration of a PDF/Monte-Carlo method suitable for pollutant formation/emission predictions in gas turbine combustors into a conventional 3-D finite-volume boundary-fitted-coordinate CFD code, PDF/CFD solver validation by comparison with experimental data for model combustion chambers and PDF/LES coupling preliminary studies.
- Experimental data for code validation including measurements in gaseous turbulent jet premixed and diffusion flames using LDV, thin digitally-compensated thermocouples, Rayleigh and forms of Mie scattering and in a quartz-sided single sector combustor using planar LIF.
- Development and extension of planar LIF diagnostics including simultaneous parent fuel fraction/OH measurements and NO and CO evaluation.

Thème(s)

Data not available

Appel à propositions

Data not available

Régime de financement

CSC - Cost-sharing contracts

Coordinateur

Universidad de Zaragoza
Contribution de l’UE
Aucune donnée
Adresse
Maria de Luna 3
50015 ZARAGOZA
Espagne

Voir sur la carte

Coût total
Aucune donnée

Participants (6)