Quantitative measurements of nitric oxide in high-pressure (2–5 atm), swirl-stabilized spray flames via laser-induced fluorescence

Cooper, Clayton S.; Laurendeau, Normand M.

doi:10.1016/s0010-2180(00)00165-6

Cited by 33 publications

(9 citation statements)

References 22 publications

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“…Another important hydrodynamic mode, the Precessing Vortex Core (PVC), is also be identified through DMD analysis, and appears to correspond to the high frequency content observed in the pressure power spectra. 4. The potential nonlinear coupling between the dominant acoustic modes (5L) and the PVC hydrodynamic mode may enhance intermediate frequencies around 4 kHz.…”

Section: Identification Of Instability Mechanismsmentioning

confidence: 99%

Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor

Huang

Gejji

Anderson

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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A concurrent computational and experimental study of self-excited combustion dynamics in a model configuration of a lean direct injection (LDI) gas turbine combustor are described. Incoming air temperature and equivalence ratio were varied. Simulation at low equivalence ratio compared better with measurement and thus this condition was selected for a more detailed study of the underlying combustion dynamics mechanisms. First, hydrodynamic modes are investigated by conducting the simulation with an acousticallyopen combustor so that acoustic effects on the flow field are minimized. The Vortex Breakdown Bubble (VBB) proves to be an important flow structure that can easily interact with the acoustic field to sustain instability. Second, detailed cycle studies of the acoustically closed combustor simulation reveals enhanced mixing and vaporization of the JP-8 fuel spray due to acoustic compression wave. Dynamic Mode Decomposition (DMD) analysis is used to identify the coupling between axial acoustics and the vortex breakdown bubble in the lower frequency region. Presence of another important hydrodynamic mode, the Precessing Vortex Core (PVC) is also identified from the DMD analysis. The possibility of nonlinear coupling between the acoustics and PVC modes is indicated.

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Section: Identification Of Instability Mechanismsmentioning

confidence: 99%

Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor

Huang

Gejji

Anderson

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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“…Both OH and NO formation in the early stages are therefore seen to be boosted by a rise in incylinder pressure. Several researchers [30][31][32] noted that practical combustors employing turbulent diffusion flames have largely demonstrated a P 0.5 scaling of NO emissions with pressure. At high enough equivalence ratios, the NO formation rate becomes predominantly thermal in origin and limited by the abundance of O atoms.…”

Section: Effect Of In-cylinder Pressurementioning

confidence: 99%

Laser-Induced Fluorescence Investigation of Nitric Oxide Formation and Hydroxyl Radicals in a Diesel Rapid Compression Machine

Demory

Crua

Heikal

2010

SAE Technical Paper Series

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The research presented here aims at providing a deeper understanding of the formation of nitric oxide in diesel combustion. To this end, in-cylinder distributions of nitric oxide (NO) were acquired by laser-induced fluorescence (LIF) in a rapid compression machine at conditions representative of a modern diesel passenger vehicle. In particular, the effects of injection and in-cylinder pressure on NO formation were investigated temporally and spatially to offer new insight into the formation of NO. Excitation and collection strategies were notably fine-tuned to avoid the collection of spurious signal due to oxygen (O 2) fluorescence. NO fluorescence was first recorded slightly after the onset of the diffusion flame and until late in the expansion stroke. The early low levels of NO were located on the lean side of the high density of hydroxyl radicals (OH). The absence of NO inside the flame plume could however not be investigated because of the severe attenuation of the laser light attributed to hot CO 2 molecules, intermediate species and soot. The formation rate of nitric oxide was found almost constant during the mixing-controlled combustion, the OH densities were restricted to the upstream part of the flame and moved inwards. High OH densities and high soot densities were not found to coexist. Finally, at the end of fuel injection, the spray collapsed on itself thus resulting in high densities of OH and NO throughout. Some of the NO seemed to be formed after the end of apparent combustion, when OH radicals were not detected. The observed fluorescence signal increase was linked to a rapid cooling of the flame plume and the associated freezing of the thermal NO mechanism. Injection pressure was found to influence the location and extent of regions with high densities of NO, but not the overall formation or width of the flame plume. Raising the in-cylinder pressure from 5 MPa to 7 MPa led to a shorter flame penetration and ignition delay with more NO formed early and in the upstream part of the flame. The plume and flame front width were seen to contract with rising in-cylinder pressure, and higher rates of NO formation could be observed as a result of increased air density and local temperatures.

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“…Fundamental understanding of these processes is necessary to advance combustion technologies and avoid the harmful impacts of such conditions [5][6][7]. One strategy to study these effects has been to develop laboratory-scale, gas turbine model combustors (GTMCs) that represent the flow structure, geometry, and other complexities found in systems of practical relevance [8][9][10][11][12]. As such, the Dual-Swirl GTMC (developed at the German Aerospace Center, DLR) has become a widely-used platform for detailed experimental and numerical investigations of these very important flows.…”

Section: Introductionmentioning

confidence: 99%

5 kHz thermometry in a swirl-stabilized gas turbine model combustor using chirped probe pulse femtosecond CARS. Part 2. Analysis of swirl flame dynamics

Slabaugh

Dennis

Boxx

et al. 2016

Combustion and Flame

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We have performed a detailed analysis of the temperature field in a turbulent swirl flame operating with a self-excited thermo-acoustic instability. The temperature field was measured using 5 kHz chirpedprobe-pulse (CPP) femtosecond (fs) coherent anti-Stokes Raman scattering (CARS). The measurements are described in detail in the part 1 companion article. In this paper, part 2, a detailed analysis of the time-resolved temperature measurements and simultaneous pressure measurements is performed to provide insight into the dynamics and structure of the swirl-stabilized flame. This work is the first to capture the dynamics of the flame, flow, and coupled flow-flame processes using high-fidelity, spatially-and temporallyresolved thermometry in a flame of practical relevance. The time-averaged contour plot of the temperature field indicates that the flame is very flat and stabilizes approximately 10 mm downstream of the burner face. In this region, there are very significant temperature fluctuations indicating a very high level of unsteadiness. The temperature probability distribution functions (PDFs) are clearly bimodal in this region near the injector face. A Fourier analysis of the temperature time series revealed multiple coherent oscillatory modes. The strongest oscillation was found to be coherent and in-phase with an acoustic resonance at 314 Hz, as expected from the Rayleigh criteria for the unstable flame. An analysis of the phase-conditioned average temperature fields show clearly an axial pumping of low-temperature reactants, which are consumed after a convective delay and result in a spike in the global heat-release rate. Continued analysis also revealed a 438 Hz oscillation that was found to correspond with the dynamics of convective transport by a helical precessing vortex core (PVC). The structure of the PVC, and its interaction with the flame, were studied based on the presence of this characteristic frequency in the power spectral densities computed throughout the flow. The precision and time-resolution of the CPP fsCARS measurements was also sufficient to enable computation of the integral timescales as well as the PDFs of the temporal temperature gradients. A sample of state space trajectories were used to provide insight into the nature of coupling between the narrowband acoustic resonance and the broadband spectrum of turbulent flame processes.

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Quantitative measurements of nitric oxide in high-pressure (2–5 atm), swirl-stabilized spray flames via laser-induced fluorescence

Cited by 33 publications

References 22 publications

Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor

Combustion Dynamics Behavior in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor

Laser-Induced Fluorescence Investigation of Nitric Oxide Formation and Hydroxyl Radicals in a Diesel Rapid Compression Machine

5 kHz thermometry in a swirl-stabilized gas turbine model combustor using chirped probe pulse femtosecond CARS. Part 2. Analysis of swirl flame dynamics

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