Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion AFOSR MURI Kick off meeting The Ohio State University Nov 4, 2009 Miles Shneider Group
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Personnel Team Richard Miles (PI) Mikhail Shneider (Co PI) Arthur Dogariu (Research Scientist) Sohail Zaidi (Research Scientist) t) Chairajeev Kalra (Student- Princeton Plasma Science and Technology Fellow) James Michael (Student - NDSEG Fellow) Dimitry Opaits (Student) Phil Howard (Technical Support) International Collaborators Sergey Leonov Christophe Laux Svetlana Starikovskaya Boris Potapkin Nickolay Aleksandrov, (Peter Barker)
Miles Shneider Group Primary Foci Thrust 1. Experimental studies of nonequilibrium air-fuel plasma kinetics using advanced non-intrusive diagnostics Task 2: Laminar Flow Reactor and Nanoparticle Studies at Low to Intermediate Temperatures (Radar REMPI and Filtered Rayleigh Scattering in flames) Task 7: Fundamental studies on microwave enhanced combustion at atmospheric and higher pressures (Laser designated microwave driven ignition and microwave enhanced flame propagation) Thrust 3. Experimental and modeling studies of fundamental nonequilibrium discharge processes Task 10: Characterization and Modeling of Nsec Pulsed Plasma Discharges (Modeling and Radar REMPI of nonequilibrium states) Task 11: Experimental and Modeling Study of Plasma properties using Radar REMPI (Radar REMPI measurement of electron loss mechanism and rates and local lelectron number density)
Preliminary Work Radar REMPI Atomic oxygen in a flame NO mole fractions in laboratory air to <10 ppb Limited by natural NO concentration in NJ air (~10 ppb) Electron attachment and recombination rate measurements in nitrogen, air and humid air Laser designated microwave driven ignition Point ignition with 180 μj, 200 fsec laser designator plus 50 mj, 2 μsec microwave pulse Line ignition with 600 μj, 200 fsec laser designator plus 50 mj, 2 μsec microwave pulse > 50% ignition kernel growth rate enhancement with triple pulsed microwave cowave Multiple point ignition
Radar REMPI Microwave scattering from laser-induced carriers Microwave illuminates the ionization spot. Microwave scattering is collected. Laser Microwave Beam Microwave Echo Microwave/laser measurement configuration. The focused laser creates a small region of ionization and the microwaves are scattered from that region into the microwave detector.
Microwave Experimental Setup: Homodyne and Heterodyne 100 GHz circulator 100 GHz horn 90 GHz pre-amp 10 GHz X Y Quadrature mixer 10 GHz mixers Laser Homodyne 100 GHz system. Heterodyne 100 and 90 GHz system. 100 GHz probes the plasma. 100 GHz probes the plasma, the phase shift is measured on the 10 GHz beating signal. The mixer output is proportional with the scattering amplitude, hence electron density The quadrature mixer provides the X and Y components, hence we also measure the phase. Sub-nanosecond temporal resolution!
Atomic oxygen in a flame 4 2000K Methane Air flame Atomic line of oxygen in flame is narrow (34 cm -1 limited by laser bandwidth) Spectral line in cold air atomic oxygen via photolysis is 10 times broader: high temperature (50,000K) imposed by intense laser pulse. Radar REMPI can distinguish between flame and photolysis atomic oxygen. 0 3 2 1 0 2.0 1.5 1.0 0.5 Gaussian fit, = 33.5 cm -1 HW1/e 2 Cold air 88600 88625 88650 88675 88700 After subtraction of cold air signal Gaussian fit, = 3.5 cm -1 HW1/e 2 Flame, atomic oxygen line 88600 88625 88650 88675 88700 Energy (cm -1 )
Resonant signal from atomic oxygen vs. equivalence ratio Atomic Oxygen 0.0004 6 Atomic oxygen line signal Atomic Oxygen REMPI signal Calculated O mole fraction 0.0003 5 Rem mpi signal 0.0002 4 3 0.0001 2 0 1 0.60 0.75 0.90 1.05 1.20 1.35 Equivalence ratio Equilibrium model 1D chemkin
1+1 Radar REMPI in NO 1+1 Radar REMPI in NO 1+1 REMPI in NO, laser at 226nm 2.0 1.5 20 Torr NO (80Torr N 2 ) 1 Torr NO (4 Torr N 2 ) signal from NO 1.0 pure NO (50 mtorr) NO (50 mtorr) and N 2 (850 Torr) NO (50 mtorr) and dry air (850 mtorr) Signal 1.0 0.5 Normaliz zed Radar REMPI 0.5 0 4414 40 4415 50 4416 60 441 70 Energy (cm -1 ) 4418 80 4419 90 4420 00 0 0 50 100 150 200 Time (ns) Pure NO shows longer lifetime due to electron diffusion. In order to measure the recombination rate we suppress diffusion by adding N 2. In air we can measure attachment rate.
NO trace Detection (limited by background ~ 10 ppb NO in air) 0.03 0.02 air 1ppb 10ppb 100ppb 0.01 0-0.01-20 -10 0 10 20 30 Time (ns)
Direct measurement of electron attachment in atmospheric air Previous Extrapolated estimate for 850 Torr dry air (78%N 2, 21%O 2, 1% Ar):
Identifying Electron loss mechanism and rate NO at 0.13 Torr in 1atm. buffer (170ppm) NO at 0.13 Torr in 1atm. buffer (170ppm) Norm malized Signal 0.8 0.6 0.4 0.2 1 In N 2 : N( t) Air buffer, dn/dt = - n 2 - n = 9.4x10 7 s -1 0 N 2 buffer, dn/dt = - n 2 n 0 = 14x10 7 s -1 1 N0t 0 0 20 40 60 Time (ns) Norm malized Signal 0.1 0.01 0 20 40 60 80 Time (ns) N recombination only, NOT an exponential decay Attachment in air: at N e N( t) N0 at 1 1 e a N0 at N( t) e N0 1 close to close to exponential a 0,
Testing NO in buffer gases Signal 0.20 1+1 Radar REMPI in NO at 226 nm 0.15 NO 0.5Torr + N 2 2Torr NO 0.5Torr + N 2 2Torr + dry air 100Torr NO 0.5Torr + N 2 2Torr + dry air 340Torr 0.10 NO 0.5Torr + N 2 2Torr + dry air 760Torr 0.05 0 0 40 80 120 N 2 increases electron loss via recombination by suppressing diffusion Dry air faster decay due to electron Signal 0.15 0.10 0.05 NO 0.5Torr + N 2Torr 2 NO 0.5Torr + N 2 2Torr + humid air 97Torr NO 0.5Torr + N 2 2Torr + humid air 752Torr attachment to O 2 Humid air further increase of losses due to higher attachment rates in water 0 0 40 80 120 Time (ns)
Laser Designated Microwave Ignition Experimental Apparatus Camera Screen Magnetron Tuner (d) Waveguide Sliding Short Seed Ionization Laser Pulse Circulator Collimated Nd:YAG (532 nm) Microwave Field 3GHz 30kW peak power TE10 Mode λ guide = 11.2 cm E field ~ 0.1E breakdown Laminar Premixed Flow D premixed = 1.9 cm U exit = 70 cm/s 14
Ps Laser-MW Evolution in Air Laser spot evolution Laser + MW evolution MW on
Laser Ignition: Kernel growth comparison Single and multiple pulse microwave 0.0 ms 1.0ms 1.1 ms 1.9 ms 2.0ms 2.1 ms 2.9 ms Single pulse 6 mm IGNITION Micro- wave PULSE 1 Microwave PULSE 1 PULSE 2 triple pulse 1 msec intervals PULSE 3 6 mm
Multi-point Multi point ignition 6 mm uexit 70 cm/s Two 7mJ seed laser spots 75 mj MW pulse φ = 0.7; Uexit = 70 cm/s 3 ms after initial seed laser pulse Flame kernel indicates ignition
200 Femtosecond Seed 180 μj 10 us 100 us 500 us 1000 us 6 mm
200 Femtosecond Seed 600 μj 10 us 100 us 500 us 1000 us 6 mm
Ignition of Methane/Air Mixtures Seed ionization pulse 7mJ; 200 ps, 780 nm MW heating pulse 50mJ; 2 μs, 3GHz Observed Minimum Seed Laser Energies λ seed [nm] φ f [m] E laser [mj] *E MW [mj]* 800 (200 fs) 0.8 0.06 0.2 50 780 0.8 0.06 3 50 780 0.8 0.10 7 50 780 0.7 0.10 7, 7 75 390 0.8 0.10 1.5 50
Fundamental Mechanisms, Predictive Modeling, and dnovel laerospace Applications of Plasma Assisted Combustion Team members: Collaborators: Yiguang Ju AFOSR MURI Kick off meeting The Ohio State University Nov 4, 2009 Wenting Sun, Sanghee Won, Mruthunjaya Uddi Interactional: Fei Qi, University of Science and Tech. China AFRL collaborators: Campbell Carter, Timothy Ombrello, Skip Williams
Ju s Group Primary Research Focus Thrust 1. The effects of kinetic and transport of plasma assisted ignition Task 1: Experimental measurements of minimum ignition energies using a spherical bomb with different electrode geometries Task 2: Experimental measurements of ignition/extinction limits by using counterflow flames Thrust 2. Intermediate Species Measurements at Elevated Pressures by Using a Plasma Assisted Jet Stirred Reactor with Molecular Beam Sampling Task 1: Development of plasma assisted a jet stirred reactor Task 2: Measurements of intermediate species of fuel oxidation Thrust 3. Mechanism Reduction and Dynamic Multi-time Scale Modeling of Detailed Plasma-Flame Chemistry Task 1: Development of dynamic multi-timescale modeling Task 2: Simulations of unsteady ignition and extinction of plasma discharge with detailed kinetic mechanisms
Research Task Description, Methods, and Preliminary Results
Thrust 1. The effects of kinetic and transport of plasma assisted ignition Task 1: Experimental measurements of minimum ignition energies using a spherical bomb with different electrode geometries Q? Q min Minim mun ignitio on power, Q 2 1.5 1 2.5 2.4 2.3 2.2 1.9 Le = 2.1 1.8 = Le 2.0 1.9 1.7 1.8 1.7 1.6 0.5 Z=10 1.6 1.5 1.5 1.4 Z=13 1.4 0 0 500 1000 1500 2000 2500 3 Cube of critical flame radius, R C 2.0
Experimental methods (a) (b) (c) (a) (b) (c) Igniter configurations
Thrust 1. The effects of kinetic and transport of plasma assisted ignition Task 2: Experimental measurements of ignition/extinction limits by using counterflow flame w/wo non-equilibrium plasma discharge 2200 2000 Plasma+CH4/air 1800 x, K Tmax 1600 1400 1200 1000 800 Thermal ignitioniti Kinetic ignition 850 K 900 K 1100 K 1050 K 1025 K 950 K 1000 K 1400 K 1300 K 1200 K 1 10 100 1000 10000 Strain, s -1
Thrust 1. The effects of kinetic and transport of plasma assisted ignition Task 2: Experimental measurements of ignition/extinction limits by using counterflow flame w/wo non-equilibrium plasma discharge LIF: OH, NO, CH2O TALIF: O, H Nanosecond pulser: Carter
Thrust 2: High pressure JSR and MBMS experimental methods of intermediate species measurements High pressure, high temperature chamber Laser beam Preheated air Fuel MBMS analysis Mixing DBD discharge Jet stirred reactor Reactor exit Reaction products Quartz nozzle 0.1-5 atm nd 1 st 2 Turbo Turbo pump pump Mass analyzer Skimmer 10-4 Torr Molecular beam Charged ion separation 10-6 Torr
Three stage molecular beaming sample for high pressure
Equipment installation (EFRC program) Comstock Time of flight (TOF) MB system: RTOF210: Mass resolution up to 5000 m/z Li and Qi, ACR, 2009
Thrust 3. Mechanism Reduction and Dynamic Multi-time Scale Modeling of Detailed Plasma-Flame Chemistry Task 1: Development of dynamic multi-timescale modeling approach Task 2: Simulations of unsteady ignition and extinction of plasma discharge with detailed kinetic mechanisms Total computation time K 3 t 80% t Chem t total C. K. Law and T. Lu, Energy and Combustion,2009
Multi Time Scale Method (MTS) The Basic Idea of Multi-Time Scale Method: timescale changes! Y k K k e t k Fastest Group Medial Groups Δt F Δt M Number of spe ecies 40 35 30 25 20 15 10 t = 0.1 ms t = 0.2 ms t = 0.3 ms 5 Slowest Group 0 Δt S -1-2 -3-4 -5-6 -7-8 -9-10 -11-12 -13 Log 10 (characteristic time / s) 0 1 2 Δt Time Diagram of multi time scale scheme Δt F is the time step of fthe fastest t group, Δt M is the time step of fthe medial group, and Δt S is the time step of the slowest group
n-decane/air Validation by homogeneous ignition 121 species (M. Chaos, IJCK,2007) Ignition in homogeneous mixture Mass s fraction 2.8 temperature 10 5 CO2 2.6 24 2.4 10 0 OH 2.2 10-5 10-10 10-15 ODE MTS HMTS 2.0 18 1.8 1.6 1.4 C10H22 10-20 12 1.2 0 1 2 3 4 5 Time (0.1 ms) Tempera ature (1000K K) delay time (ms) Ignition 2.0 VODE 1.5 MTS HMTS 1atm 1.0 0.5 20atm 0.0-0.5 05 0.5 06 0.6 07 0.7 08 0.8 09 0.9 1000/Initial temperature (1/K) Temperature and species profiles Ignition delay time for n-decane-air
Computation efficiency vs. Mechanism size Base No. Mechanism Time Step(s) Initial Pressure (atm) Initial CPU Time(s) CPU Temperature RTOL ATOL VODE MTS Time (K) Saving a1 H 2 1.0E-6 1 1200 1.0E-4 1.0E-13 0.28 0.13 53.6% a2 H 2 1.0E-7 1 1200 1.0E-4 1.0E-13 13 2.58 1.31 49.2% a3 H 2 1.0E-8 1 1200 1.0E-4 1.0E-13 24.9 7.56 69.6% a4 H 2 1.0E-9 1 1200 1.0E-4 1.0E-13 260 18.4 92.9% b1 CH 4 1.0E-6 1 1400 1.0E-4 1.0E-13 13 123 25 79.7% 7% b2 CH 4 1.0E-7 1 1400 1.0E-4 1.0E-13 1269 181 85.7% b3 CH 4 1.0E-8 1 1400 1.0E-4 1.0E-13 14639 1029 93.0% c1 C 10 H 22 1.0E-6 1 1400 1.0E-4 1.0E-13 86 14 83.7% c2 C 10 H 22 1.0E-7 1 1400 1.0E-4 1.0E-13 773 125 83.8% c3 C 10 H 22 1.0E-8 1 1400 1.0E-4 1.0E-13 7609 1049 86.2%
A path flux analysis method for model reduction T 0 =1200 K ig (s) 0.01 detail DRG PFA 1E-3 1 atm 50 60 70 80 90 ig (s) 1E-3 1E-4 20 atm 50 60 70 80 90 Number of species in skeletal lmechnism 15
Modeling of flame front trajectories of spherical propagating flames using MTS p p p g g g