Nonequilibrium Thermodynamics Laboratories The Ohio State University

“Fundamental Mechanisms, Predictive Modeling,

and Novel Aerospace Applications of Plasma Assisted Combustion“

Program Overview and 3rd Year Progress

W. Lempert

Departments of Mechanical&Aerospace Engineering and Chemistry

The Ohio State University

Columbus, OH

DoD MURI Third Year Review Meeting

November 6, 2012

2009 MURI Topic #11: Chemical Energy Enhancement by

Nonequilibrium Plasma Species

PRINCETON

University

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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 NOx.

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 (300 – 1000 K) temperatures.

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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).

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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 (300 – 1800 K) and pressures

(0.1 – 70 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!

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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.

Nonequilibrium Thermodynamics Laboratories The Ohio State University

MURI Thrusts: Inter-Relationships

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

Mechanisms

Studies of diffusion and transport of active species

in representative two dimensional

reacting flow geometries

Experimental and modeling studies of fundamental non-

equilibrium discharge processes

MURI : Chemical Energy Enhancement by Non-equilibrium Plasma Species

Experimental studies of non-equilibrium air-fuel

plasma kinetics usingadvanced non-intrusive

diagnostics

Kinetic model development and

validation

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.

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Facility Summary* (Designed to Span Wide T, P Range)

(*All facilities designed and fabricated specifically for this program.)

3000K

1000K

300K

0.01atm 1atm 100atm

Flames

(Ju, Sutton)

Flow Reactors

( Yetter, Adamovich)

Shock Tube

(Starikovskiy)

RCM

(Starikovskiy)

MW+laser (Miles)

JSR/Flow Reactor (Ju)

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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 H2/Air Ignition Expt.

• OSU/Penn State: OSU Supplied Pulsed Discharge for PSU

Reactor. (Collaborative OH LIF Measurements are Planned for Future).

Team Coordination and Communication

• ~Monthly Telecoms.

• AIAA Aerospace Sciences (and other) Meetings.

• Yearly Program Reviews.

Nonequilibrium Thermodynamics Laboratories The Ohio State University

A Few Year 3 Highlights

Nonequilibrium Thermodynamics Laboratories The Ohio State University

OSU Platform I: Low T Plasma Chemical

Kinetic Studies - Plane-to-Plane NS Discharge

Absolute OH (LIF) and T (CARS&LIF) – Konnov Kinetic Mechanism

CH4, C2H4/Air, To = 500 K, P = 100 Torr, 50 Pulses@40 kHz (C3H8 Data Also Obtained)

Side view: T0=500 K, ϕ=0.3, 50 nsec gate, single-shot Schematic

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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

HVE

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.

FACILITY

BURNER

CONFIGURATION

Plasma off Plasma ON

CxHy/O2/N2 Flames

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Experimental Platform III:

Point-to-point, single-pulse nsec pulse discharge

10

mm

2 mm

N2, P=100 torr, 15 mJ/pulse, Psec CARS

N2, P=100 torr, 15 mJ/pulse, 10 μs delay

Spontaneous Raman

Total Vibrational Quanta More Approximately

Double AFTER 1 μsec

Air Behaves Similarly

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Penn State Flow Reactor Studies (Ethylene/O2/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 C2H4 / 3000ppm O2 / Ar.

Vplasma = 10kV, v = 1 kHz

0

500

1000

1500

2000

700 800 900 1000 1100 1200 1300

Sp

eci

es

Mol

e F

ract

ion

[pp

m]

Temperature [K]

C2H

4CO

OSU ModelPSU Exp.

CO2

Heating Zone = 2 ft

Inlet Outlet

PSU 3 Zone Plasma Flow Reactor

Nonequilibrium Thermodynamics Laboratories The Ohio State University

P = 72 Torr, a= 250 1/s, f = 24 kHz, XO2=40%

0.00 0.02 0.04 0.06 0.08 0.10 0.12

1x105

2x105

3x105

4x105

5x105

6x105

Extinction

increase

decrease

CH

2O

PL

IF (

a.u

.)

Fuel mole fraction

Hot Ignition

LTC

HTC

P = 72 Torr, a= 250 1/s, f = 34 kHz, XO2=60%

0.00 0.02 0.04 0.06 0.08 0.10 0.12

1x105

2x105

3x105

4x105

5x105

6x105

increase

decrease

CH

2O

PL

IF (

a.u

.)

Fuel mole fraction

LTC

HTC

Smooth transition

between LTC to HTC

Increased radical

production

Princeton – Ju: NS Discharge - Counterflow diffusion flame

kinetic studies (CH3OCH3 ignition by LIF).

0.01 0.1 1 10 100 10000.0000

0.0005

0.0010

0.0015

0.0020T=650 K No O addition

1000 ppm O addition

CH

2O

mo

le f

ra

cti

on

Residence time (ms)

R+O2

CH2O+radicals

90% of total reaction

flux

1000 times faster!

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Multipath (24)

mini-Herriott cell.

Image of DBD plasma discharge at 1 kHz.

In situ multispecies and temperature

measurement.

100

150

200

250

300

350

400

450

500

1

10

100

1000

10000

100000

0 1000 2000 3000

Tem

pe

ratu

re [

K]

Mo

le F

ract

ion

[p

pm

]

Plasma Frequency [Hz]

[CH4] with O2

[C2H2] with O2

[H2O]

Temperature

Ar/O2/C2H4 25% and φ=1,

60 Torr

Princeton - Ju: Mid-infrared in-situ multi-species and

temperature measurements by TDLAS

Detector

QCL Laser

Diluents

Diluents

Oxidizer

Fuel

To Vacuum

Electrode

VacuumChamber

Nanosecond-Pulsed

Power Supply

Pulsed Signal Generator

Digital Delay Generator

Function Generator

Oscilloscope

7.03-7.72 μm

DBD – Multi-Pass TDLAS ns

Discharge Facility.

→

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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).

Expanding

Flame Kernal

(Schlieren)

Flame Speed Enhancement

2 usec pulses, 50 mJ/pulse

Extinction Extension for 1

(25 mJ), 2 (50 mJ), and 3

usec (75 mJ) pulses.

Nonequilibrium Thermodynamics Laboratories The Ohio State University

FLEET

100 fsec laser excites nitrogen.

Image UV spectrum - 2nd Positive and

1st Negative bands – T from spectrum.

18

Princeton – Miles: Temperature and NO

Diagnostics (300 – 2000 K)

FLEET and TC relative temperatures

(along a line) in a hot jet.

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

0

0.025

0.050

0.075

-5 0 5 10 15 20

FlameCold air

Time (ns)

Ra

da

r R

EM

PI

sig

na

l (V

)

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Princeton - Starikovskiy: High Pressure Facilities

(Rapid Compression Machine and Shock Tube)

P = 25-40 atm, T = 650 – 950 K, Propane-Air (Lean Conditions)

Facility

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Princeton – Starikovsky: Shock Tube - Discharge

P5 = 0.1-10 atm, T = 300 – 3000 K, time 1-2000 ms

Nonequilibrium Thermodynamics Laboratories The Ohio State University

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

Coupled Pulse

Energy

O and O3

Nonequilibrium Thermodynamics Laboratories The Ohio State University

Summary – Where We Are and Where We Are

Going in Remaining Two Years

• 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 H2, CH4, C2H4, and C3H8, 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 N2 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

Where We Are Going

• Higher pressure and temperature.

• Higher C hydrocarbons and oxygen containing fuels.