2009 MURI Topic #11: Chemical Energy Enhancement by Nonequilibrium Plasma Species

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1 2009 MURI Topic #11: Chemical Energy Enhancement by Nonequilibrium Plasma Species Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion Program Overview and 3 rd Year Progress W. Lempert Departments of Mechanical&Aerospace Engineering and Chemistry Columbus, OH DoD MURI Third Year Review Meeting November 6, 2012 PRINCETON University

2 MURI Principal Investigators Walter R. Lempert, Igor V. Adamovich, J. William Rich, Jeffrey Sutton. Ohio State University Program Lead Institution. Yiguang Ju, Richard B. Miles, and Mikhail Shneider, and Andrey Starikovskiy Princeton University. Richard Yetter Pennsylvania State University Vigor Yang Georgia Institute of Technology

3 Primary Scientific Issues Plasma sources have shown promise in enhancing several fundamental combustion phenomena such as: I. Reduction of ignition delay which impacts high speed (supersonic/hypersonic) propulsion. II. Increase flammability limits, particularly fuel-lean combustion (potential for decreased temperature and reduced NO x. III. Increased extinction strain rate (lower temperature turbulent combustion). Despite the progress in development of plasma-based devices (torches, filamentary discharges), there has been very little effort in developing a comprehensive understanding of the underlying non-equilibrium plasma-chemical oxidation kinetics and mechanisms. This MURI focuses on developing such a fundamental understanding, particularly plasma-chemical fuel oxidation at low ( K) temperatures.

4 Multidisciplinary Approach This MURI effort is inherently multidisciplinary, blending the following disciplines: Low Temperature Plasma Physics and Chemistry (Adamovich, Starikovskii, Schneider). Atomic and Molecular Energy Transfer (Rich, Adamovich, Miles, Lempert). Combustion Kinetics (Yetter, Ju, Sutton). Optical Diagnostics (Lempert, Miles, Sutton). Gas Dynamics (Rich, Yang) Computational Fluid Dynamics (Yang).

5 Program Principal Objective, Primary Deliverables, and Potential Breakthroughs. PRINCIPAL OBJECTIVE Develop experimentally validated kinetic mechanisms and modeling codes capable of predicting the impact of nonequilibrium plasmas on reactive processes, particularly on ignition, chemical energy release, and flameholding in combustors of flight vehicle engines. PRIMARY DELIVERABLES Extensive new experimental data sets of non-equilibrium plasma chemical energy conversion kinetics over a wide range of initial temperatures ( K) and pressures ( bar), in a variety of complementary new test facilities, specifically designed and fabricated for this program. Detailed non-equilibrium plasma chemical energy conversion kinetic mechanisms, validated over a wide range of conditions, using data from multiple facilities. Extensive experimental data sets on ignition delay, flameholding and laminar flame speed augmentation by nonequilibrium discharges, including nsec pulsed, DC/RF, and microwave. High fidelity multi-dimensional plasma combustion modeling codes, validated in a series of model flows, with emphasis on the high subsonic to supersonic flow regimes. POTENTIAL BREAKTHROUGH Development of Predictive Capability for use in Future Air Force Plasma-Based Propulsion Systems!

6 Principal Thrust Areas Thrust 1. Experimental studies of nonequilibrium air-fuel plasma kinetics using advanced non-intrusive diagnostics. Thrust 2. Kinetic model development and validation. Thrust 3. Experimental and modeling studies of fundamental nonequilibrium discharge processes. Thrust 4. Studies of diffusion and transport of active species in representative two-dimensional reacting flow geometries.

7 MURI Thrusts: Inter-Relationships Scientific approach structure for 2009 Plasma Assisted Combustion MURI program. (1) Advanced methodologies and facilities for acquisition of new experimental plasma kinetic data sets. (2) Development of advanced plasma chemical oxidation mechanisms. (3) Development of validated numerical modeling codes. MURI : Chemical Energy Enhancement by Non-equilibrium Plasma Species Experimental studies of non-equilibrium air-fuel plasma kinetics using advanced non-intrusive diagnostics Experimental and modeling studies of fundamental nonequilibrium discharge processes Studies of diffusion and transport of active species in representative two dimensional reacting flow geometries Mechanisms Kinetic model development and validation Experimentally validated kinetic mechanisms and modeling codes capable of predicting the impact of nonequilibrium plasmas on reactive processes, particularly on ignition, chemical energy release, and flameholding in combustors of flight vehicle engines

8 Facility Summary* (Designed to Span Wide T, P Range) 3000K Shock Tube (Starikovskiy) 1000K 300K Flames (Ju, Sutton) Flow Reactors ( Yetter, Adamovich) JSR/Flow Reactor (Ju) MW+laser (Miles) RCM (Starikovskiy) 0.01atm 1atm 100atm (*All facilities designed and fabricated specifically for this program.)

9 MURI Team Major Interconnections Technical Activities OSU/Princeton/GT/Penn State: OSU Plasma Kinetic Model. Princeton/Georgia Tech: Plasma Diffusion Flame Expt./Simulation. OSU/Georgia Tech: Nsec Plane-to-Plane DBD Discharge Model and H 2 /Air Ignition Expt. OSU/Penn State: OSU Supplied Pulsed Discharge for PSU Reactor. (Collaborative OH LIF Measurements are Planned for Future). ~Monthly Telecoms. Team Coordination and Communication AIAA Aerospace Sciences (and other) Meetings. Yearly Program Reviews.

10 A Few Year 3 Highlights

11 OSU Platform I: Low T Plasma Chemical Kinetic Studies - Plane-to-Plane NS Discharge Schematic Side view: T 0 =500 K, ϕ=0.3, 50 nsec gate, single-shot Absolute OH (LIF) and T (CARS&LIF) Konnov Kinetic Mechanism CH 4, C 2 H 4 /Air, T o = 500 K, P = 100 Torr, 50 Pulses@40 khz (C 3 H 8 Data Also Obtained)

12 OSU Platfrom II: Low Pressure NS Plasma-Flame Goal: Examine the effects of non-equilibrium plasma on OH radical concentration in a 1D low-pressure flame/plasma chamber FACILITY BURNER CONFIGURATION C x H y /O 2 /N 2 Flames HVE Plasma off Plasma ON Plasma effects on OH generation are the greatest in the preheat zone (closest to burner) and increase as the equivalence ratio is decreased. Planned Absorption and Temperature measurements will put relative LIF signals on an absolute scale.

13 Experimental Platform III: Point-to-point, single-pulse nsec pulse discharge N 2, P=100 torr, 15 mj/pulse, Psec CARS 2 mm 10 mm N 2, P=100 torr, 15 mj/pulse, 10 μs delay Spontaneous Raman Total Vibrational Quanta More Approximately Double AFTER 1 μsec Air Behaves Similarly

14 Species Mole Fraction [ppm] Penn State Flow Reactor Studies (Ethylene/O 2 /Argon) Strategy: Dilute Mixtures Enables Low T Kinetics to be Studied Under Isothermal Conditions. Data Obtained With/Without Plasma. Experimental Conditions: P = 1 atm, Q = 1 LPM, 800ppm C 2 H 4 / 3000ppm O 2 / Ar. V plasma = 10kV, v = 1 khz C 2 H 4 CO CO 2 OSU Model PSU Exp. PSU 3 Zone Plasma Flow Reactor 1000 Inlet Outlet 500 Heating Zone = 2 ft Temperature [K]

15 CH 2 O PLIF (a.u.) CH 2 O PLIF (a.u.) CH 2 O mole fraction Princeton Ju: NS Discharge - Counterflow diffusion flame kinetic studies (CH 3 OCH 3 ignition by LIF) No O addition 1000 ppm O addition T=650 K 1000 times faster! R+O 2 CH 2 O+radicals 90% of total reaction flux Residence time (ms) P = 72 Torr, a= 250 1/s, f = 24 khz, X O2 =40% P = 72 Torr, a= 250 1/s, f = 34 khz, X O2 =60% 6x10 5 5x10 5 4x10 5 3x10 5 2x10 5 1x10 5 increase decrease Extinction LTC HTC Hot Ignition Fuel mole fraction Smooth transition between LTC to HTC Increased radical production 6x10 5 5x10 5 4x10 5 3x10 5 2x10 5 1x10 5 LTC HTC increase decrease Fuel mole fraction

16 Mole Fraction [ppm] Temperature [K] Princeton - Ju: Mid-infrared in-situ multi-species and temperature measurements by TDLAS DBD Multi-Pass TDLAS ns Discharge Facility. Image of DBD plasma discharge at 1 khz. Diluents Detector Electrode Nanosecond- Pulsed Power Supply Oxidizer Fuel Diluents μm QCL Laser Vacuum Chamber To Vacuum Oscilloscope Pulsed Signal Generator Digital Delay Generator Function Generator In situ multispecies and temperature measurement. Ar/O 2 /C 2 H 4 25% and φ=1, 60 Torr Multipath (24) mini-herriott cell [CH4] with O2 [C2H2] with O2 [H2O] Temperature Plasma Frequency [Hz]

17 Princeton - Miles: Flame Speed and Extinction Limit Enhancement by Microwave Energy Addition Methane/Air Flame Initiated by Laser Spark (20 mj, 10 nsec, 532 nm). 3GHz, 25 kwatt, ~ usec, microwave pulses applied at 1 msec intervals. Microwave Localizes Energy Addition to Region of Ionization. Microwave Energy Addition ~ 10% of Heat of Combustion with 3 usec pulses). Flame Speed Enhancement 2 usec pulses, 50 mj/pulse Expanding Flame Kernal (Schlieren) Extinction Extension for 1 (25 mj), 2 (50 mj), and 3 usec (75 mj) pulses.

18 Radar REMPI signal (V) Princeton Miles: Temperature and NO Diagnostics ( K) FLEET 100 fsec laser excites nitrogen. Image UV spectrum - 2 nd Positive and 1 st Negative bands T from spectrum. FLEET T Image Radar REMPI Resonant NO multiphoton absorption of ps/fs laser creates ionization. Free electrons scatter microwaves, initial amplitude of which is proportional to concentration) of target species. Radar REMPI from NO FLEET and TC relative temperatures (along a line) in a hot jet Flame Cold air Time (ns) 18

19 Princeton - Starikovskiy: High Pressure Facilities (Rapid Compression Machine and Shock Tube) Facility P = atm, T = K, Propane-Air (Lean Conditions)

20 Princeton Starikovsky: Shock Tube - Discharge P 5 = atm, T = K, time ms

21 Simulation (Georgia Tech) of OSU (Adamovich) 1D NS Plane-to-Plane Dielectric Barrier Discharge Model. Model Geometry Temporal Evolution of Reduced Electric Field and Electron Density O and O 3 Coupled Pulse Energy

22 Summary Where We Are and Where We Are Going in Remaining Two Years Where We Are Wide variety of facilities have been constructed and are operational. Multiple new experimental plasma kinetic data sets have been obtained, mostly (but not exclusively) in H 2, CH 4, C 2 H 4, and C 3 H 8, and dimethyl ether. Plasma kinetic model for these fuels has been developed and disseminated. Good, but not perfect, agreement is generally found. New diagnostics (FLEET, Radar REMPI, Multi-pass Mid IR TDLAS) have been developed. Both plasma oxidation (due to O generation) and plasma reforming (due to fuel fragmentation) have been identified as being important. Potential role of N 2 vibrational excitation has been identified. High fidelity 2-D plasma chemical simulation code has been developed and initial validation against MURI team member experiments performed with good agreement. Where We Are Going Higher pressure and temperature. Higher C hydrocarbons and oxygen containing fuels.