Laser-diagnostic and numerical study of strongly swirling natural gas flames

Landenfeld, Tilo; Kremer, A.; Hassel, Egon; Janicka, J.; Schäfer, Th.; Kazenwadel, J.; Schulz, Christof; Wolfrum, J.

doi:10.1016/s0082-0784(98)80502-x

Cited by 49 publications

(37 citation statements)

References 10 publications

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“…The injector is moved vertically within the chamber like a piston (up to 500 mm) in order to change the axial-plane of measurement 12,13 . The axial symmetry of the flame has been previously reported as being "experimentally checked and confirmed" 14,15 .…”

Section: Descriptionmentioning

confidence: 69%

Detailed Emissions Prediction for a Turbulent Swirling Nonpremixed Flame

et al. 2014

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This paper describes validation of a previously-described CFD-CRN method (computational fluid dynamics -chemical reactor network) for emissions predictions for the laboratory benchmark TECFLAM S09c flame. It details CFD simulation, solution strategy, validation using, CRN generation, detailed emissions predictions and reaction pathway studies. Steady-state 3D CFD models of a 45° † Corresponding author. Email address: rory.monaghan@nuigalway.ie. Tel: +353(91)494-256. 2 sector of the combustor, employing standard numerical techniques; steady-state k- SST turbulence, P1 radiation, finite-rate eddy-dissipation turbulence-chemistry interaction, and three-step methane combustion mechanism, were created in ANSYS FLUENT v14. Steady-state models were used as they are of interest to industrial researchers, who are often limited to their use by extremely complex geometries. The models differ in their handling of pressure-velocity coupling and discretization of the momentum equation. The solution which uses SIMPLE coupling and second-order upwind discretization of the momentum equation was generally found to give better results. Satisfactory agreement with experimental profiles for velocity, turbulent kinetic energy, temperature, and species mass fractions has been achieved. Some errors are seen in temperature and CO mass fractions at the highest temperatures (T > 2000 K) and are due to the fact that the highly-simplified three-step kinetic mechanism employed due to practical limitations on computational resources, underestimates CO2 dissociation. The results compare satisfactorily with the state-of-the-art. Non-zero concentrations of CO are predicted in the external recirculation zone, which has not been achieved in previous modeling efforts. The validated solution was used as the basis to generate a CRN using the CFD-CRN method.The CFD-CRN method uses user-defined criteria to divide the CFD domain into a set of interconnected perfectly-stirred reactors (PSRs), i.e. a CRN. This CRN is then solved using detailed chemical kinetic mechanisms in the Kinetic Post-Processor (KPPSMOKE) solver. CRN size-independence studies are performed and it is determined that 5000+ PSRs were needed to adequately capture pollutant formation in the complex recirculating flow field. Validation of CFD-CRN predictions of major species show similar accuracy to steady-state CFD simulation, with improvements over state-of-the-art CFD in CO profile predictions. Satisfactory agreement with previously-published experimental NOx contour plots is also seen. The CFD-CRN is used to study NOx formation pathways in the swirling, turbulent environment of the S09c diffusion flame. As expected, NOx is seen to form primarily in the hightemperature internal recirculation zone (IRZ). The prompt pathway is predicted to be of greatest importance in this area. Significant NOx reburning is seen in the low temperature fuel-air jets 3 immediately adjacent to the IRZ. Overall, the prompt pathway is responsible for 77% of NOx leaving the system, with 12% due to the...

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Section: Descriptionmentioning

confidence: 69%

Detailed Emissions Prediction for a Turbulent Swirling Nonpremixed Flame

et al. 2014

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“…Meanwhile, improvement of the combustion dynamics and flame characteristics is important since the swirl-enhanced mixing of the flame components would lead to a more complete fuel combustion and cleaner energy production in jet engines, gas turbines and combustors. The results of experimental study and numerical modelling of the development of swirling flow dynamics for non-reacting and reacting flows, the formation of the flow field structure and flame stability confirm that the presence of swirl considerably increases the stability limits of most flames [9] with direct influence on the flame structure [9]- [12], mixing of the flame components and the development of chemical reactions [14]. The results of previous experimental study [9] on the development of confined isothermal swirling flow dynamics in a cylindrical tube with a swirling air inlet at the fixed distance from the bottom of the tube suggest that the formation of the swirling flow field and flow structure is highly influenced by the downstream and upstream swirling airflow formation.…”

Section: Introductionmentioning

confidence: 72%

Control of the Development of Swirling Airflow Dynamics and Its Impact on Biomass Combustion Characteristics

Barmina

Valdmanis

Zake

2017

Latvian Journal of Physics and Technical Sciences

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The development of the swirling flame flow field and gasification/ combustion dynamics at thermo-chemical conversion of biomass pellets has experimentally been studied using a pilot device, which combines a biomass gasifier and combustor by varying the inlet conditions of the fuel-air mixture into the combustor. Experimental modelling of the formation of the cold nonreacting swirling airflow field above the inlet nozzle of the combustor and the upstream flow formation below the inlet nozzle has been carried out to assess the influence of the inlet nozzle diameter, as well primary and secondary air supply rates on the upstream flow formation and air swirl intensity, which is highly responsible for the formation of fuel-air mixture entering the combustor and the development of combustion dynamics downstream of the combustor. The research results demonstrate that at equal primary axial and secondary swirling air supply into the device a decrease in the inlet nozzle diameter enhances the upstream air swirl formation by increasing swirl intensity below the inlet nozzle of the combustor. This leads to the enhanced mixing of the combustible volatiles with the air swirl below the inlet nozzle of the combustor providing a more complete combustion of volatiles and an increase in the heat output of the device.

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“…7 shows OH LIF intensities which are phase averaged over 400 single exposures. The flame front may be assumed to be located close to the steepest OH gradient [6]. The LIF images are superimposed by phase-averaged axial velocities (ū +ũ) plots.…”

Section: High Oscillation Amplitudesmentioning

confidence: 99%

Unsteady flame and flow field interaction of a premixed model gas turbine burner

Schildmacher

Hoffmann

Selle

et al. 2007

Proceedings of the Combustion Institute

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In recent years, the NOx emissions of heavy duty gas turbines have been significantly reduced by introducing lean premixed combustion. However, these flames are known to be prone to combustion instabilities, which became the key issue of modern gas turbine combustion research. In this paper, investigations of a single model gas turbine burner are presented with special focus on thermo-acoustic eigenmodes of the combustor and the resulting interaction between periodic flow field oscillations and flame front fluctuations. A numerical analysis of the eigenmodes of the combustor rig was preformed and compared to pressure probe measurements. By the numerical analysis Helmholtz mode pressure oscillations were predicted to be present in the air plenum upstream the burner as well as in the combustion chamber. These oscillation modes could well be confirmed by the analysis of the pressure signals taken at different position within the combustor rig. By these pressure oscillations thermo-acoustic flame instabilities are triggered. Due to a phase lag between the pressure oscillations in the air plenum and those in the combustion chamber, fluctuations of air flow through the burner are induced, which in turn cause fluctuations of the equivalence ratio at the burner exit plane. As result, fluctuations of the heat release rate within the flame are established, which interfere with the acoustics of the rig and, thus, unstable combustion is maintained. The dynamics of the flow field and of the flame was studied experimentally by phase-locked LDA and OH-LIF diagnostics. The experimental results give an excellent insight into the chain of processes that are responsible for the thermo-acoustic instabilities. Interestingly, two different oscillation modes could be identified depending on the amplitude of the oscillations. At low oscillation levels only weak and locally confined velocity fluctuations in the main reaction zone were observed which do not have any significant impact on the flame. By increasing the equivalence ratio, the transition from low to high oscillation levels can be triggered. Under high oscillation levels, a pumping motion of the flow field in axial direction could be identified which causes strong periodic disturbances of the flame.

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Laser-diagnostic and numerical study of strongly swirling natural gas flames

Cited by 49 publications

References 10 publications

Detailed Emissions Prediction for a Turbulent Swirling Nonpremixed Flame

Detailed Emissions Prediction for a Turbulent Swirling Nonpremixed Flame

Control of the Development of Swirling Airflow Dynamics and Its Impact on Biomass Combustion Characteristics

Unsteady flame and flow field interaction of a premixed model gas turbine burner

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