Experiments on Low-Temperature Combustion Combustion Development - PowerPoint PPT Presentation

Experiments on Low-Temperature Combustion Combustion Development of a Stabilized Cool Flame Platform & Faraday Rotation Spectroscopy Diagnostic for In-Situ Measurement of HOx Radicals 2nd Flame Chemistry Workshop San Francisco San Francisco 2 ‐ 3 August 2014 Sang Hee Won and Brian Brumfield (Joseph Lefkowitz) Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA PRINC E TON Mechanical and Aerospace Engineering 1

PRINC E TON Mechanical and Aerospace Introduction Engineering Take ‐ home messages from the 1 st Flame Chemistry Workshop • – What is the definition of flame chemistry? • • Chemical kinetics constrained by transport Chemical kinetics constrained by transport – Development of well ‐ defined experimental platforms • Extend ability to access low temperature chemistry (LTC) • Advanced laser diagnostic technique • R Recent advanced engines t d d i – Operate at low to intermediate temperature at higher pressure conditions – Near ‐ limit combustion behaviors tend to be correlated with LTC Temperature / K 1300 1200 1100 1000 900 800 700 50000 50000 LBO test by Med Colket (UTRC) 3 Detailed Model + Surrogate Fuels Jet-A, POSF 4658 IPK, Iso Paraffinic Kerosene S-8, Coal-to-Liquid 10000 SPK, Gas-to-Liquid e, τ / μ s Ignition delay time 1000 Temperature window for DCN (CN) measurements (CN) measurements 100 20 atm, stoichiometric fuel in air 50 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1000K / T 1) H. Wang, M. A. Oehlschlaeger, Fuel 98 (2012) 249-258. 2 2) S. H. Won, et al., “Comparative Evaluation of Global Combustion Properties of Alternative Jet Fuels,” 51th AIAA Aerospace Sciences Meeting , Grapevine, Texas (2013). 3) Med Colket, 2013 MACCCR meeting

PRINC E TON Mechanical and Aerospace Motivations Engineering 1. Experimental platform for cool flame – To stabilize LTC ‐ driven flame 2. Development of FRS technique – Quantifying the LTC related species 3

Development of a Stabilized Cool Flame Development of a Stabilized Cool Flame Platform 2nd Flame Chemistry Workshop San Francisco San Francisco 2 ‐ 3 August 2014 Sang Hee Won 1 , Bo Jiang 1 , Pascal Diévart 1 , Chae Hoon Sohn 2 , Yiguang Ju 1 1 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, USA 2 Department of Mechanical Engineering, Sejong University, Seoul 143 ‐ 747, Republic of Korea PRINC E TON Mechanical and Aerospace Engineering 4

PRINC E TON Mechanical and Aerospace Engineering Challenges to Stabilize LTC ‐ Driven Flames • Induction chemistry at low temperature is very slow – Inability to initiate the radical pool (RH + X = R + HX) – Very sensitive to molecular structure • Then, how to shorten the induction chemistry? • Cool flames; mostly observed in premixed configuration l fl l b f – Flow reactor, jet ‐ stirred reactor, etc.. • Is it possible to observe cool flames in diffusive configuration ? 10000 10000 experiment, 13.5 atm, 2nd ig. model, 13.5 atm, 2nd ig. imes [ms] model, 13.5 atm, 1st ig. 1000 Adiabatic Constant Volume Ignition model, 1.0 atm, 2nd ig. model, 1.0 atm, 1st ig. 3 100 at 700 K τ @ 2nd stage ignition nition delay t 2 10 1 atm 1 τ @ 1st stage ignition pressure 1 0 0 20 40 60 80 100 120 time [ms] time [ms] Ign 0.1 0 1 13.5 atm 13 5 770 K 850 K 0.01 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 5 1000/T [1/K] 1) H. J. Curran, P. Gaffuri, W. J. Pitz, C. K. Westbrook, Combust. Flame 114 (1998) 149-177.

PRINC E TON Mechanical and Aerospace Hints from Recent Studies Engineering Zero ‐ Gravity Experiment 1,2 • Observed cool diffusion flame • Observed cool diffusion flame in a droplet combustion • Cool flame exists in diffusive configuration! 1) V. Nayagam et al., Combust. Flame 159 (2012) 4) T. Ombrello, S. H. Won, et al., Combust. Flame 157 (2010) 2) T. I. Farouk, F. L. Dryer, Combust. Flame 161 (2014) 5) T. M. Vu, S. H. Won, et al., Combust. Flame 161 (2014) 6 3) W. Sun, S. H. Won, et al, Proc. Combust. Inst. 34 (2013)

PRINC E TON Mechanical and Aerospace Hints from Recent Studies Engineering Zero ‐ Gravity Experiment 1,2 Plasma ‐ Assisted Combustion 3 ‐ 5 • • Observed cool diffusion flame • Observed cool diffusion flame Initiation of radical pool can be Initiation of radical pool can be accelerated by Plasma in a droplet combustion • Enhancing flame ignition, • Cool flame exists in diffusive propagation speed, and stabilization • configuration! Electronically excited species and ozone , etc. Increasing fuel loading Increasing fuel loading CH CH 4 15 7x10 χ O2 =34% flame initiation flame stabilization 15 6x10 χ O2 =62% -3 ) Extinction r density (cm 15 perature 5x10 Plasma generated Smooth species: 15 4x10 Transition O, H, O 2 (a ∆ g ) … O, H, O 2 (a ∆ g ) … Extinction Extinction OH number Temp 15 3x10 the classical S ‐ curve 15 2x10 Ignition Low pressure counterflow diffusive 15 1x10 Ignition configuration with nano-second pulsed Residence time 0.05 0.10 0.15 0.20 0.25 0.30 0.35 discharge 3 discharge F Fuel mole fraction l l f ti New combustion regime 1) V. Nayagam et al., Combust. Flame 159 (2012) 4) T. Ombrello, S. H. Won, et al., Combust. Flame 157 (2010) 2) T. I. Farouk, F. L. Dryer, Combust. Flame 161 (2014) 5) T. M. Vu, S. H. Won, et al., Combust. Flame 161 (2014) 7 3) W. Sun, S. H. Won, et al, Proc. Combust. Inst. 34 (2013)

PRINC E TON Mechanical and Aerospace Experiments Engineering • A heated counterflow burner integrated with vaporization system 1 – n ‐ heptane/nitrogen vs. oxygen/ozone • Ozone generator (micro ‐ DBD) produces 2 ‐ 5 % of ozone in oxygen stream, depending on oxygen flow rate • Speciation profiles by using a micro ‐ probe sampling with a micro ‐ GC 2 GC. 2 Fuel/N 2 @ 550 K Heated N 2 @ 550 K Positioning stage Stagnation Pressure plane Micro-GC chamber N 2 @ 300 K Thermal gradient in mixing layer initiates O 2 + O 3 @ 300 K reaction of O 3 + (M) = O + O 2 + (M) O 2 @ 300 K Ozone generator 1) S. H. Won, et al., Combust. Flame 157 (2010) 8 2) J. K. Lefkowitz, S. H. Won, et al., Proc. Combust. Inst. 34 (2013)

PRINC E TON Mechanical and Aerospace Initiation of Cool Diffusion Flames Engineering • Procedure to initiate a cool diffusion flame 1) 1) Setting nitrogen (fuel side) and oxygen (oxidizer side) Setting nitrogen (fuel side) and oxygen (oxidizer side) flow rates 2) Turning on the ozone generator 3) 3) Flowing fuel (n ‐ heptane) to fuel side Flowing fuel (n heptane) to fuel side Lower fuel mole fraction: Higher fuel mole fraction: Cool diffusion flame Hot diffusion flame 9

PRINC E TON Mechanical and Aerospace Initiation of Cool Diffusion Flames Engineering • Existence of cool diffusion flames in counterflow configuration with n ‐ heptane – cool flame regime exists regardless of addition of ozone – . 2400 ] e Tmax [K] nC 7 H 16 /N 2 vs O 2 or O 2 /O 3 HF branch in counterflow burner X f = 0.05 ,T f = 550 K, and T o = 300 K 2000 Extinction limit of emperature conventional hot diffusion flame conventional hot diffusion flame (HFE) 1600 (a) Cool diffusion flame without O 3 1200 Extinction limit of Maximum te cool diffusion flame cool diffusion flame (CFE) HTI CF branch 800 (b) Hot diffusion flame M LTI LTI 400 0.1 1 10 100 1000 10000 10 Strain rate a [1/s]

PRINC E TON Mechanical and Aerospace Initiation of Cool Diffusion Flames Engineering • Existence of cool diffusion flames in counterflow configuration with n ‐ heptane – cool flame regime exists regardless of addition of ozone – Addition of ozone extends cool flame regime. 2400 e Tmax [K] ] nC 7 H 16 /N 2 vs O 2 or O 2 /O 3 HF branch in counterflow burner X f = 0.05 ,T f = 550 K, and T o = 300 K 2000 Extinction limit of emperature conventional hot diffusion flame conventional hot diffusion flame (HFE) 1600 (a) Cool diffusion flame without O 3 1200 Extinction limit of Maximum te cool diffusion flame cool diffusion flame with O 3 ith O (CFE) HTI CF branch 800 (b) Hot diffusion flame M LTI LTI 400 0.1 1 10 100 1000 10000 11 Strain rate a [1/s]

PRINC E TON Mechanical and Aerospace Speciation Profiles Engineering 900 e [K] • Temperature measurements Temperature measurements Temperature T [K] exp T [K], exp. 700 700 T [K], model – Over ‐ estimation of heat 500 (a) release in model prediction 300 0 4 8 12 16 20 24 Distance from fuel side nozzle [mm] 120000 ecies mole ction [ppm] 100000 • Failure to predict the flame 80000 nc7h16, exp. 60000 nc7h16, model position position. o2/10, exp 40000 Spe frac o2/10, model (b) 20000 – Boundary conditions were 0 0 4 8 12 16 20 24 tested previously. 1 Distance from fuel side nozzle [mm] 40000 h2o, exp. ole pm] h2o, model Species mo 30000 – Consistent even without fraction [pp co exp co, exp. co, model co2, exp. 20000 putting sampling probe or co2, model 10000 thermocouple. (c) 0 6 10 14 18 Distance from fuel side nozzle [mm] 12 1) J. K. Lefkowitz, S. H. Won, et al., Proc. Combust. Inst. 34 (2013)