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HIGH–TEMPERATURE LOW–NOX
COMBUSTOR CONCEPT DEVELOPMENT TIMOTHY C. LIEUWEN, JERRY SEITZMAN, SURESH MENON, MATTHEW D. SIRIGNANO, VEDANTH NAIR, BENJAMIN EMERSON, EDWIN GOH, ANDREAS HOFFIE
U T S R R E S E A R C H A N N U A L P R O J E C T R E V I E W M E E T I N G
O C T O B E R 3 1 S T, 2 0 1 8
D AY T O N A B E A C H , F L
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MOTIVATION
• Gas turbine combined cycle efficiency has steadily increased from 47% to 62% over the past 3 decades
• Driven by advances in materials and cooling methods
• Simultaneous reduction in NOx emissions enabled by advanced combustion technologies
• Higher flame temperatures → higher efficiencies
• New combustor paradigm is needed
• Current architectures (e.g. DLN) can’t meet current emissions standards at elevated combustor temperatures
New challenge: low NOx at high flame temperatures
1
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PROPOSED APPROACH
• Thermal NO formation dependent on temperature, residence time, and O radical concentration
• Approach: Axial Staging
• Reduce residence time @ high temperatures
• Incorporate advantages of EGR (reduced [O])
• Reactor model studies have demonstrated advantages and potential pitfalls of axial staging (Ahrens et al., 2016 & Goh et al, 2017)
• Highly sensitive to degree of mixing
(Bowman, 1992)
2
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KEY RESEARCH QUESTIONS
4
(1) For a given firing temperature and residence time, what are the minimum theoretical NOx limits?
• How much lower is this fundamental limit than the limits achievable with current architectures?
(2) What do the actual fuel and air distribution patterns look like that attempt to achieve these theoretical values?
• Then, what are the operational behaviors of such a combustion system?
(3) What do local pre- & post-flame mixing patterns look like and how is the heat release distributed?
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EXECUTIVE SUMMARY
• Theoretical NOx floor enabled by axial staging is O(1 ppm)
• Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet
• Crossflow entrainment with jet material/combustion products is critical to achieving low NOx emissions
• NOx production primarily controlled by (1) stoichiometry of the jet and (2) lift-off of the flame from the jet exit
• Vortical structures (shear layer, CVP) strongly influenced by flame lifting
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TOP LEVEL METHODOLOGY
• Multi-pronged investigation with high degree of collaboration
• Reactor modeling with theoretical and practical considerations as well as optimization
• Experimental RJICF NOx emissions characterization with flame imaging
• RJICF simulation using LES
• Results from each facet of investigation utilized to assist in interpreting results and informing next steps of the others
Reactor Modeling & Optimization
Detailed Simulation
Experimental Investigation
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DEVELOPED MODELING, EXPERIMENTAL,
AND SIMULATION TOOLS
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REACTOR NETWORK MODELS
• Independent rates for mixing as well main burner product and secondary fluid entrainment: ൗ1 𝜏𝑚𝑖𝑥𝑖𝑛𝑔 , Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 , Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐
• Finite mixing in reactor modeled using Interaction by Exchange
with the Mean (IEM): 𝜓 𝑡 + 𝑑𝑡 = 𝜓 𝑡 −𝐶𝜙
2𝜏𝑚𝑖𝑥𝜓 𝑡 − 𝜓
Secondary
Fluid
Vitiated Main
Burner
Products
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛
𝜏𝑒𝑛𝑡,𝑠𝑒𝑐
𝜏𝑚𝑖𝑥Secondary Reactor
Secondary
Fluid
Non-Reacting Mixer
Vitiated Main
Burner Products
Infinite mixing and entrainment Finite mixing and entrainment
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CURRENT OPERATIONAL CAPABILITIES
• Main burner & bypass air provides crossflow of lean, combustion products at a wide range of equivalence ratios
• Multi-layer ceramic shielded flow conditioning section enable enthalpy retention yielding high cross flow temperatures
• Highly configurable jet injector allows choice of diameter, velocity profile, and 3 species selection
• Test section with 4 sided optical access
• Quench section rapidly cools exhaust to freeze NO chemistry prior to sampling
• Facility operated at P = 1atm
NG + Air
Bypass Air
Main
Burner
Flow Conditioning
Test Section
Jet Injector
Quench Section
Residence
Time ModuleEmissions
Sample Plane
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LES DOMAIN AND SIMULATION PARAMETERS
10
• LESLIE simulation with AMR-CutCell1 method employed to reduce cost
• Scaling factor of 3.0 applied to geometry and velocity
• Flame is resolved with 3 – 4 LES cells
• Physical flow-through time of 𝑡𝑓 ≈ 1.54 𝑚𝑠 (mean)1Muralidharan, B. and Menon, S. JCP (321), 342-368, 2016
no-slip walls
VitiatedCrossflow
Outflow
Jet
• Simulation time:• ~24 hrs (512 cores) for 3-species cold flow• ~72 hrs (800 cores) for 19-species reacting flow• ~7 flow-through times (21 days) to complete one case
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THEORETICAL NOX FLOOR
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Key research questions
12
(1) For a given firing temperature and residence time, what are the minimum theoretical NOx limits?
• How much lower is this fundamental limit than the limits achievable with current architectures?
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MODELING: THEORETICAL NOX MINIMUM
• Infinite mixing for theoretical minimum limit
• CO constraint imposed:
• 125% of Equilibrium level
• General rule for NO floor:
• Main burner as lean as possible with remainder of fuel injected as late as possible
• Minimum NO levels insensitive to global 𝜏𝑟𝑒𝑠
• Konnov & UCSD mechanisms predict similar NO
AFS Theoretical Limit
LPM – 10 ms
NOx floor at high flame temperatures ~O(1ppm) !!
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MODELING: THEORETICAL NOX MINIMUM
• Theoretical limit a continuum of multiple designs
• Require a single geometric configuration for direct comparison of potential improvement over DLN architectures → Multi-point design
• Meeting CO constraint across entire turn down range → forces selection of design optimized for less that 1975K
AFS Theoretical Limit
(Single-Point Designs)
LPM – 10 ms
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MODELING: THEORETICAL NOX MINIMUM
• Theoretical limit a continuum of multiple designs
• Require a single geometric configuration for direct comparison of potential improvement over DLN architectures → Multi-point design
• Meeting CO constraint across entire turn down range → forces selection of design optimized for less that 1975K
AFS Multi-Point Design
AFS Theoretical Limit
(Single-Point Designs)
LPM – 10 ms
NOx floor still at ppm levels for multi-point optimum
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BEHAVIOR OF PRACTICAL AXIALLY
STAGED COMBUSTION SYSTEMS
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Key research questions
17
(2) What do the actual fuel and air distribution patterns look like that attempt to achieve these theoretical values?
• Then, what are the operational behaviors of such a combustion system?
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EXPERIMENTAL: RICH PREMIXED JET EMISSIONS
ΔNOx as a function 𝜙𝑗𝑒𝑡 for constant
crossflow conditions at 𝜙𝐻𝐸 = 0.525
• Preliminary work experimentally demonstrated NOx benefit of axial staging with a RJICF at high combustor temperatures.
→ Most emissions efficient way to deliver ΔT with a RJICF?
• ΔNOx utilized to assess emissions efficiency of jets at similar ΔT
• Higher rise in system equivalence ratio (Δφ) higher ΔNOx
• For fixed Δφ, higher jet equivalence ratio(φJet) lower ΔNOx
• Higher φJet is coupled with reduction in J
• For fixed Δφ, higher lift-off height (LO/dj) lower ΔNOx
ΔNOx can vary up to 3x at constant Δϕ
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EXPERIMENTAL: FLAME LIFTING
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EXPERIMENTAL: FLAME LIFTING
Lee-Stabilized
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“Lean Lifted”
EXPERIMENTAL: FLAME LIFTING
Lee-Stabilized
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“Lean Lifted”
EXPERIMENTAL: FLAME LIFTING
“Rich Lifted”
Lee-Stabilized
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EXPERIMENTAL: EMISSIONS
• Higher ΔT higher NO
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EXPERIMENTAL: EMISSIONS
• Higher ΔT higher NO
• Lean lifted flames:
• Very little NOx production compared to baseline
• NOx production insensitive to 𝜙𝑗𝑒𝑡
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EXPERIMENTAL: EMISSIONS
• Higher ΔT higher NO
• Lean lifted flames:
• Very little NOx production compared to baseline
• NOx production insensitive to 𝜙𝑗𝑒𝑡
• Attached flames:
• Significant increase in NOx production is observed compared to lean lifted cases
• NOx production increases with 𝜙𝑗𝑒𝑡 for attached flames until
𝜙𝑗𝑒𝑡~2.5 then plateaus
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EXPERIMENTAL: EMISSIONS
• Higher ΔT higher NO
• Lean lifted flames:
• Very little NOx production compared to baseline
• NOx production insensitive to 𝜙𝑗𝑒𝑡
• Attached flames:
• Significant increase in NOx production is observed compared to lean lifted cases
• NOx production increases with 𝜙𝑗𝑒𝑡 for attached flames until
𝜙𝑗𝑒𝑡~2.5 then plateaus
• Rich lifted flames:
• Reduction in NOx production compared to attached cases
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EXPERIMENTAL: DOPING IMPACT ON LIFTING
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
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EXPERIMENTAL: DOPING IMPACT ON LIFTING
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
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EXPERIMENTAL: DOPING IMPACT ON EMISSIONS
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
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EXPERIMENTAL: DOPING IMPACT ON EMISSIONS
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
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EXPERIMENTAL: DOPING IMPACT ON EMISSIONS
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
• 150K series shows significant reduction in NO
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EXPERIMENTAL: DOPING IMPACT ON EMISSIONS
• 150K and 225K series doped with methane until fully lifted behavior was observed for each data point
• 150K series shows significant reduction in NO
• 225K had significant reduction for low ɸjet but not for high ɸjet
• Highest ɸjet cases already fully lifted for 225K series
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EXPERIMENTAL: LIFTING IMPACT ON EMISSIONS
• Methane doping is forcing towards lean lifted behavior, but transition not always complete
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EXPERIMENTAL: LIFTING IMPACT ON EMISSIONS
• Methane doping is forcing towards lean lifted behavior, but transition not always complete
Different lifting regimes impact NO in different ways → connection to
entrainment sensitivity shown by reactor modeling
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MODELING: PRACTICAL CONSIDERATIONS
• Finite mixing and entrainment model used to isolate and analyze the impact of entrainment and mixing on theoretical NOx minimums
• Can also help de-convolute experimental results by isolating sensitivities
Secondary
Fluid
Vitiated Main
Burner
Products
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛
𝜏𝑒𝑛𝑡,𝑠𝑒𝑐
𝜏𝑚𝑖𝑥
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MODELING: PRACTICAL CONSIDERATIONS
• Finite mixing and entrainment model used to isolate and analyze the impact of entrainment and mixing on theoretical NOx minimums
• Can also help de-convolute experimental results by isolating sensitivities
Secondary
Fluid
Vitiated Main
Burner
Products
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛
𝜏𝑒𝑛𝑡,𝑠𝑒𝑐
𝜏𝑚𝑖𝑥
Secondary Fluid
Vitiated Main Burner Products
Entrainment Region
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
• With fast mixing, reduce NOx by:
• Increasing main product entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
• With fast mixing, reduce NOx by:
• Increasing main product entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛)
• Reducing secondary fluid entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
• With fast mixing, reduce NOx by:
• Increasing main product entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛)
• Reducing secondary fluid entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Threshold for NOx performance when entrainment rates are matched ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
• With fast mixing, reduce NOx by:
• Increasing main product entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛)
• Reducing secondary fluid entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Threshold for NOx performance when entrainment rates are matched ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Very rapid main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) → low
NOx regardless of secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
![Page 42: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/42.jpg)
MODELING: FINITE ENTRAINMENT RATE EFFECTS
• With fast mixing, reduce NOx by:
• Increasing main product entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛)
• Reducing secondary fluid entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Threshold for NOx performance when entrainment rates are matched ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Very rapid main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) → low
NOx regardless of secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Rapid entrainment of crossflow → lean stoichiometry of burning
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
![Page 43: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/43.jpg)
MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
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MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
![Page 45: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/45.jpg)
MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔
𝑻𝒊𝒈𝒏
𝜙𝑖𝑔𝑛
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
![Page 46: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/46.jpg)
• High main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) relative to
secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Start lean and hot → rapid autoignition
• System ramps up to 𝜙𝑔𝑙𝑜𝑏𝑎𝑙 as fuel is entrained
• Always lean!
• No temperature overshoot = Low NOx
MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔
𝑻𝒊𝒈𝒏
𝜙𝑖𝑔𝑛
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
![Page 47: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/47.jpg)
• High main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) relative to
secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Start lean and hot → rapid autoignition
• System ramps up to 𝜙𝑔𝑙𝑜𝑏𝑎𝑙 as fuel is entrained
• Always lean!
• No temperature overshoot = Low NOx
• Low main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) relative to
secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Start rich (or near stoich) and cooler → delayed autoignition
• 𝝓 ≈ 1 for reaction time
• High flame temp and prompt contributions
• Temperature overshoot & time to dilute = High NO
MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔
𝑻𝒊𝒈𝒏
𝜙𝑖𝑔𝑛
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
![Page 48: HIGH TEMPERATURE LOW NOX COMBUSTOR CONCEPT … · •Measurements show NO production can vary significantly at a fixed rise in bulk average temperature (ΔT) across the jet •Crossflow](https://reader030.vdocuments.site/reader030/viewer/2022041105/5f05f18d7e708231d41580ca/html5/thumbnails/48.jpg)
• High main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) relative to
secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Start lean and hot → rapid autoignition
• System ramps up to 𝜙𝑔𝑙𝑜𝑏𝑎𝑙 as fuel is entrained
• Always lean!
• No temperature overshoot = Low NOx
• Low main entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛) relative to
secondary entrainment rate ( Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Start rich (or near stoich) and cooler → delayed autoignition
• 𝝓 ≈ 1 for reaction time
• High flame temp and prompt contributions
• Temperature overshoot & time to dilute = High NO
MODELING: FINITE ENTRAINMENT RATE EFFECTS
𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 = 𝟎. 𝟓 𝒎𝒔
𝑻𝒊𝒈𝒏
𝜙𝑖𝑔𝑛
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
Tem
pe
ratu
re (
K)
Equ
ival
en
ce R
atio
↑𝝉𝒆𝒏𝒕,𝒔𝒆𝒄 → ↑𝝉𝒓𝒆𝒔 of hot spot
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MODELING: FINITE MIXING RATE EFFECTS
• Entrainment constant, reduce Τ1 𝜏𝑚𝑖𝑥 by 30x
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
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MODELING: FINITE MIXING RATE EFFECTS
• Entrainment constant, reduce Τ1 𝜏𝑚𝑖𝑥 by 30x
• NOx reduction still present if main entrainment rate is greater than secondary ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 > Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
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MODELING: FINITE MIXING RATE EFFECTS
• Entrainment constant, reduce Τ1 𝜏𝑚𝑖𝑥 by 30x
• NOx reduction still present if main entrainment rate is greater than secondary ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 > Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Finite mixing becomes significant when secondary entrainment rate becomes greater than main
( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 < Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Mixing impact can be either beneficial or detrimental
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
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MODELING: FINITE MIXING RATE EFFECTS
• Entrainment constant, reduce Τ1 𝜏𝑚𝑖𝑥 by 30x
• NOx reduction still present if main entrainment rate is greater than secondary ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 > Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Finite mixing becomes significant when secondary entrainment rate becomes greater than main
( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 < Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐)
• Mixing impact can be either beneficial or detrimental
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 10 𝜇𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝜏𝑚𝑖𝑥 = 0.3 𝑚𝑠
𝛕𝐞𝐧𝐭,𝐬𝐞𝐜 (𝐦𝐬)
Rapid entrainment of crossflow critical
for NOx reduction
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 0.2 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 1.0 𝑚𝑠
𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 = 2.0 𝑚𝑠
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MODELING: FINITE MIXING RATE EFFECTS
Rapid entrainment of crossflow is dominant compared to mixing
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MODELING & EXPERIMENT TIE INS
• Modeling of finite rate axial staging behaviors can inform experimental results
• Low NOx levels found in “lean lifted” case suggest similarities to high crossflow entrainment results
• Sufficient mixing occurs prior to combustion to drastically reduce or eliminate temperature overshoot
• For “rich lifted”
• Flame most likely occurs near stoichiometric equivalence ratio creating temperature overshoot that must be then diluted
• For lee-stabilized increase in NOx vs “rich lifted” cases potentially due to
• Impact on dilution rate of temperature overshoot from proximity of flame to jet exit
• Impact on modality of combustion of rich products (synthesis gas):diffusion vs partially premixed
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DETAILED INVESTIGATION OF LOCAL
MIXING AND HEAT RELEASE
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Key research questions
56
(3) What do local pre- & post-flame mixing patterns look like and how is the heat release distributed?
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RJICF: FLAME ATTACHMENT
Leeward Attached Lee Stabilized
(Wagner et al, 2015)
Fully Lifted
4
• Simulations conducted to investigate local structure of RJICF under a variety of attachment conditions
• ɸjet = 1.1
• Leeward attached achieved with adiabatic wall boundary condition
• Lee stabilized achieved with isothermal boundary condition
• Fully lifted achieved by additionally doubling ɸjet
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SIMULATION: ATTACHED VS LEE-STABILIZED
Attached
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y/D=0.8
SIMULATION: ATTACHED VS LEE-STABILIZED
Attached
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y/D=0.8
SIMULATION: ATTACHED VS LEE-STABILIZED
y/D=0.8
Attached Lee-Stabilized
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SIMULATION: ATTACHED VS LEE-STABILIZED
y/D=0.8 y/D=0.8
Attached Lee-Stabilized
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SIMULATION: ATTACHED VS LEE-STABILIZED
y/D=0.8 y/D=0.8
Attached Lee-Stabilized
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y/D=0.8
SIMULATION: LEE-STABILIZED VS LIFTED
y/D=0.8
Lee-Stabilized Lifted
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SIMULATION TIE INS TO MODELING & EXPERIMENT
• Single RJICF:
• Main entrainment rate less than secondary ( Τ1 𝜏𝑒𝑛𝑡,𝑚𝑎𝑖𝑛 < Τ1 𝜏𝑒𝑛𝑡,𝑠𝑒𝑐) → Not ideal for low NOx
• Lifted rich flames still initiate at near-stoichiometric equivalence ratios
• Supports hypothesis regarding rich lifted flames
• Detachment is critical for crossflow access to products of RJICF flame
• Impact on dilution of hot spots and burning of produced syngas from rich RJICF
Secondary Fluid
Vitiated Main Burner Products
Entrainment Region
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SUMMARY
• Axial staging has great potential due to a theoretical NOx floor of O(1 ppm) at high flame temperatures (>1975K)
• Entrainment rate, specifically of main burner products, is critical parameter for successful axial staging implementation
• Single RJICF does not rate well against this criteria → other configurations necessary
• Practical NO levels are highly sensitive to controlling parameters
• Regardless of specific configuration, lifting of RJICF flames from jet exit is critical in enabling the necessary entrainment and mixing to reduce NOx
• RJICF flames tend to establish themselves near stoichiometric equivalence ratios, creating hot spots
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QUESTIONS?
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BACKUP
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WORK FLOW
68
Task 1
Task 2.1
Task 2.2
Task 2.3
Task 3.1 Task 4.1
Task 4.2
Task 3.2
• Task 1: PMP
• Task 2: Kinetic modeling & optimization– 2.1 Fundamental Kinetic Studies– 2.2 NOx Optimization Studies– 2.3 Constrained NOx Optimization Studies
• Task 3: Experimental characterization of distributed combustion concept– 3.1 Facility Development– 3.2 Experimental Characterization
• Task 4: Detailed experimental & computational investigation of mixing & heat release distributions– 4.1 Large Eddy Simulations (LES)– 4.2 Experimental Characterization using High-
Speed Laser Diagnostics
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PROJECT TIMELINE
69
Tasks Progress Interdep. Year Quarter Participants
Task-1 1 2 9 10 11 12 13
1.1 Project Management and Planning ◯ GTAE DOE Low-
NOx Research
Team1.2 Reporting ◯
Task-2 1 9 10 11 12 13
2.1 Fundamental Kinetic Studies ✔ Prof. Seitzman
Prof. German
Edwin Goh
2.2 Initial NO Optimization Studies ✔ 2.1
2.3 Constrained NO Optimization ◯ 2.2 4.1
Task-3 1 9 10 11 12 13
3.1 Experimental Facility Development ✔ 2.2 Prof. Lieuwen
Dr. Ben Emerson
Matthew Sirignano
Vedanth Nair
3.2 Initial Test Matrix & Facility Characteristics ✔ 2.1, 2.2
3.3Refined Test Matrix & Facility
Characteristics◯ 2.3
Task-4 1 9 10 11 12 13
4.1 LES Studies for Subcomponent Geometry ◯ 2.3 Prof. Menon
Prof. Lieuwen
Dr. Andreas Hoffie
4.2 LES Studies for Experimental Rig ◯ 3.1, 3.2
4.3 Experiments with High Speed Diagnostics ► 3.2, 3.2
✔ : Done◯ : In Progress
► : Future
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EXPERIMENTAL: SYSTEM EMISSIONS
• Total NOX increases with increasing 𝜙𝑔𝑙𝑜𝑏𝑎𝑙
• Δ𝜙𝑔𝑙𝑜𝑏𝑎𝑙 ≡ 𝜙𝑔𝑙𝑜𝑏𝑎𝑙 − 𝜙ℎ𝑒𝑎𝑑 which is a
measure of the axial stage contribution
• For low 𝜙𝑔𝑙𝑜𝑏𝑎𝑙: low Δ𝜙𝑔𝑙𝑜𝑏𝑎𝑙 → lower NOx
• For high 𝜙𝑔𝑙𝑜𝑏𝑎𝑙: high Δ𝜙𝑔𝑙𝑜𝑏𝑎𝑙 → lower NOx
NOx benefit from RJICF observed for
high 𝜙𝑔𝑙𝑜𝑏𝑎𝑙
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SIMULATION: ATTACHED VS LEE-STABILIZED
y/D=0.8 y/D=0.8
Attached Lee-Stabilized
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SIMULATION: LEE-STABILIZED VS LIFTED
y/D=0.8 y/D=0.8
Lee-Stabilized Lifted
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SIMULATION: LEE-STABILIZED VS LIFTED
y/D=0.8 y/D=0.8
Lee-Stabilized Lifted
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SIMULATION: LEE-STABILIZED VS LIFTED
y/D=0.8 y/D=0.8
Lee-Stabilized Lifted
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FLAME IMPACT ON SHEAR-LAYER VORTICES
Reacting cases
Reacting cases which should show globally unstable behavior based on Sand J show convectively unstable SLV structure
Non-reacting casesJ = 5, S= 1.0
J = 25, S = 1.0
Reacting cases which should show globally unstable behavior based on Sand J show convectively unstable SLV structure
Suppressed SLV behavior
J = 5, S = 1.0
J = 5, S = 0.4
Reacting cases
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FLAME IMPACT ON SHEAR-LAYER VORTICES
• Cases arranged according to decreasingly globally unstable behavior
• Between the non-reacting cases the convectively unstable case has a decreased growth rate
• Reacting cases show consistently suppressed SLV growth rate compared to non-reacting cases
Non-reacting
Reacting
Convectively unstable Globally
unstable