nasa 9-point ldi code validation experiment 9-point ldi code validation experiment yolanda r. hicks,...

NASA 9-Point LDI Code Validation Experiment

Yolanda R. Hicks, Robert C. Anderson, and Randy J. Locke Abstract This presentation highlights the experimental work to date to obtain validation data using a 9-point lean direct injector (LDI) in support of the National Combustion Code. The LDI is designed to supply fuel lean, Jet-A and air directly into the combustor such that the liquid fuel atomizes and mixes rapidly to produce short flame zones and produce low levels of oxides of nitrogen and CO. We present NOx and CO emission results from gas sample data that support that aspect of the design concept. We describe this injector and show high speed movies of selected operating points. We present image-based species maps of OH, fuel, CH and NO obtained using planar laser induced fluorescence and chemiluminescence. We also present preliminary 2-component—axial and vertical—velocity vectors of the air flow obtained using particle image velocimetry and of the fuel drops in a combusting case. For the same combusting case, we show preliminary 3-component velocity vectors obtained using a phase Doppler anemometer. For the fueled, combusting cases especially, we found optical density is a technical concern that must be addressed, but that in general, these preliminary results are promising. All optical-based results confirm that this injector produces short flames, typically on the order of 5- to-7-mm long at typical cruise and high power engine cycle conditions.

https://ntrs.nasa.gov/search.jsp?R=20080005554 2018-06-16T17:56:25+00:00Z

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National Aeronautics and Space Administration

www.nasa.gov

NASA 9-Point LDI Code Validation Experiment

Yolanda R. Hicks and Robert C. AndersonNASA Glenn Research Center

Cleveland, Ohio USA

Randy J. LockeASRC Aerospace, Inc.Cleveland, Ohio USA

Fundamental Aeronautics 2007 Annual Meeting30 October – 1 November 2007

New Orleans LA

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MotivationMotivationNASA GRC has initiated efforts to develop a broad measurement database to characterize an LDI injector to facilitate understanding of the fuel vaporization, turbulent mixing and combustion processes.

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MotivationMotivation

The 9-point LDI injector will serve as a realistic test bed for validation of the NASA National Combustion Code (NCC). Advanced optical and laser diagnostic methods will be used to measure an assortment of parameters.LDI has over a 10-year history of use at NASA GRC, in several configurations. The LDI concept has been demonstrated to reduce NOx emissions (meeting 1996 Int’l Civil Aviation Organization standards) while maintaining CO and UHC’s at current levels

FAR0.018 0.020 0.022 0.024 0.026 0.028 0.030 0.032

EI N

Ox

0

2

4

6

8

10

850 F, 150 psia

650 F, 150 psia, 4 inj pt650 F, 150 psia750 F, 150 psia

(from CE-9B)

FAR0.018 0.020 0.022 0.024 0.026 0.028 0.030 0.032

EI C

O

0

20

40

60

80

100

120

850 F, 150 psia

650 F, 150 psia, 4 inj pt650 F, 150 psia750 F, 150 psia

(frop CE-9B)

NOx , CO emissions as a function of fuel/air ratio (FAR) and inlet temperature for the 9-pt LDI

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Lean Direct Injection (LDI) BasicsLean Direct Injection (LDI) Basics• Our LDI design is a multiplex fuel injector module containing

multiple fuel injection tips and multi-burning zones and is designed to replace one conventional fuel injector

• The LDI rapidly mixes jet fuel and air thereby shortening distance to complete combustion process

• Each LDI element consist of an air passage with an upstream air swirler and a converging diverging venturi section. The simplex fuel injector is inserted through the center of the swirler and the fuel tip is at the throat of the venturi.

• Axial swirlers, helical vanes generate air swirl for quick mixing and to anchor the flame near the injector exits

• LDI allows for a variety a fuel staging possibilities

Individual LDI Injector Element

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T3 = 617 K T3 = 728 K T3 = 828 K

Frames from high speed movies show a turbulent, unsteady system from which flamelets can be seen. Flow is left to right.

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The Hardware

9 pt LDI “top hat”

Optically-accessible flame tube

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Experimental ConditionsExperimental Conditions

• Inlet Pressure: 1.03 MPa (150 psia) – 1.72 MPa (250 psia)

• Inlet Temperature: 505 K (450 °F) – 827 K (1030 °F)

• ΔP/P: 3-5 %• Wair : 0.40 kg/s – 0.78 kg/s (0.89 – 1.71 lbm/s)• Φ : 0.33 – 0.55• Fuel staging of primary (four injection elements )

and secondary (five elements G) fuel circuits

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Optical Diagnostics Measurement SuiteSpecies, temp using PLIF, light scatter or Raman scatter• 2D, 3D mapping of: OH, NO, fuel liquid and vapor

CH, C2, profile and pattern factor• 1D mapping of major combustion species:

CO2, O2, N2, hydrocarbons, H2OSpecies via chemiluminescence Imaging of C2, CH, OH, NO

Velocity• 2 component mapping via images—PIV• 3 component pointwise—LDV

Drop Sizing• 3 component pointwise—PDI• shadowgraph-based, long range microscope

Flow/flame visualizationsmovies: video, high speed photography, schlieren, compilations of single-shot species, or of averaged data

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Data acquisition and analysis

• PLIF, PLS: 10 Hz repetition rate, 100 or 200-gate on-chip avgTraverse in 1-mm increments from -23 to +23

• Chemiluminescence images: on-chip 200 or 600 gates• Laser-based images subtract the appropriate background

signal. Chemiluminescence images subtract minimum signal• High Speed video photography, 16 - 19 kHz frame rate• Air velocity: Axial-vertical maps via PIV• Fuel drop velocity: Axial-vertical maps via PIV and 3D maps

via Laser Doppler Anemometry

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Imaging SetupImaging Setup

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CameraCamera

Field of view and camera arrangement for PLIF, PLS, and PIVField of view and camera arrangement for PLIF, PLS, and PIVLaser Sheet

76mm x 76 mmflow path

46 mm

+23 mm-23 mm

46 mm

Data obtained in vertical-axial plane: side views

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Side View Images End View Images

High

Low

Laser-Induced Fluorescence or Scattering Data

0 mm

-11 mm

+11 mm 3 mm

5 mm

7 mm

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End View Composites 7.5 mm from the Injector Exit

Inlet conditions: T = 617K, P = 1030 kPa, φ = 0.38, equal fuel split. “low” power

Total Fuel OH Liquid Fuel

Inlet conditions: T = 822K, P = 1723 kPa, φ = 0.41, equal fuel split. “high” power

Total Fuel OH Liquid Fuel

Scaled per species for entire set of inlet conditions tested

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End view3.6 mm downstream

Side view in center positionWhite bar denotes position of end on view

φpry = 0.38φ 2ndry = 0.38

Fuel Split differences observed using fuel (via naphthalenes) PLIFPreliminary results-uncorrected data

Tin= 650 F, Pin=150 psia

φpry = 0.65φ 2ndry = 0.22

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OH* NO* CH*T3

Chemiluminescence images: P3 = 150 psia, φ = 0.45, even split, fuel flow normalizedUseful for assessing overall symmetry

650°

F75

0°F

850°

F

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Distance from injector exit, mm

0 5 10 15 20 25 30

Sign

al, a

.u.

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0 5 10 15 20 25 30Si

gnal

, a.u

.0

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0 5 10 15 20 25 30

Sign

al, a

.u.

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0 5 10 15 20 25 30

Sign

al, a

.u.

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60

80

a. OH PLIF

d. CH* c. OH*

b. Fuel PLIF

CH*, Fuel PLIF similar

OH* strong in primary reaction zone

OH PLIF: both primary/secondary rxns

Total signal within 0.3-mm-long “probe” of data block vs. axial position

617 1034 0.45617 1034 0.38728 1034 0.45728 1034 0.35728 1034 0.35728 1724 0.45728 1724 0.35828 1034 0.45828 1034 0.35828 1379 0.45828 1379 0.35828 1724 0.41828 1724 0.35

T3 P3 φ K kPa

Short flame zones ~ 3-8 mm from dome (except lowest inlet temperature)

Fuel flow normalized

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Velocity Example 1. Air only preliminary results

• Served to test of our powder seeder for elevated pressure• Air seeded with 0.3-μm alumina particles to scatter laser• Air velocity for axial and vertical components• Average velocity field resultant from 200 instantaneous

velocity fields• Traverse in ~ 3-mm increments• Experiment inlet: Tin = 617 K, Pin = 1030 kPa• Note: Flow and model conditions are different. Physical

model is slightly different than actual hardware.

distance from injector exit, mm

verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15 20 25 30 35

-25

-20

-15

-10

-5

0

5

10

15

20 4644424038363432302826242220181614121086420

V, m/s

Axial and Vertical Velocity Components in the Central Vertical Plane

Recirc zones directlyDwnstream of injectors

Black bands—location of zero velocity

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Iso-surface of zero axial velocity showing the recirculation zones

From NCC, using Reynolds-Averaged Navier Stokes Simulation

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Comparison of Experimental and Computational Axial AirVelocities 6 mm Downstream of the Injector Exit Plane

Experimental inlet conditionsTin = 617K, Pin = 1030 kPa

Computational inlet conditionsTin = 822K, Pin = 2740 kPa

-20 -10 0 10 20

-20

-10

0

10

20Vaxial

454035302520151050

-5-10-15-20-25-30-35-40-45

Horizontal Position (mm)

Ver

tical

Pos

ition

(mm

)

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20 mm 25 mm15 mm

3 mm 9 mm6 mm

horizontal position, mm

verti

calp

ositi

on,m

m

-20 -10 0 10 20

-20

-10

0

10

20

horizontal position, mm-20 -10 0 10 20

-20

-10

0

10

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-20

-10

0

10

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-20

-10

0

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-20

-10

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horizontal position, mm

verti

calp

ositi

on,m

m

-20 -10 0 10 20

-20

-10

0

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20

End view axial velocity contours from 3mm End view axial velocity contours from 3mm -- 25 mm downstream from25 mm downstream fromthe injector exit plane. Inlet conditions: Tthe injector exit plane. Inlet conditions: Tinin = 617K, P= 617K, Pinin = 1030 = 1030 kPakPa. .

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Velocity Examples 2. Fuel drops only(highly preliminary results)

• Unseeded system, combusting environment

• P3 = 150 psia, T3 = 650°F, φ = 0.45, even fuel split

• Our first PIV measurements in a combusting systemallowed us to assess shutter and timing

• Implementation issues must be resolved for PIV and LDV measurement techniques

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axial distance from injector exit, mm

verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15

-10

-5

0

5

10


verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15

-10

-5

0

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10

p q


verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15

-10

-5

0

5

10

p , , qaxial distance from injector exit, mm

verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15

-10

-5

0

5

10


verti

cald

ista

nce

from

cent

erlin

e,m

m

0 5 10 15

-10

-5

0

5

10

p q

30028026024022020018016014012010080604020

V, m/s Within-plane velocity vectors near injection sites (top row) and between sites (bottom row)

Inlet:150 psia, 650°F, φ = 0.45

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Fuel Fuel axialaxial velocity contours from 0 velocity contours from 0 -- 16 mm downstream from16 mm downstream fromthe injector exit plane. Inlet conditions: Tthe injector exit plane. Inlet conditions: Tinin = 617K, P= 617K, Pinin = 1030 = 1030 kPakPa, , φφ = = 0.45 0.45

0 mm 0.5 mm 0.7 mm 1mm

2 mm 5 mm 8 mm 10 mm

12 mm 13 mm 16 mm

Camera

Results are preliminaryPlanes nearest the injector exhibit symptoms of an opticaly thick field

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Because the optical implementation is different, the PDA system accessesA somewhat different volume than the imaging work

From transceiver:Beams are 15° relativeto horizontal

ApproximatePDA probe volume(Note the shift wrtimaging probe volume)

PIV small region

LDA region

PLIF/PLS/PIV large region

Window full aperture =1.5” (axial) x 2”

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Horizontal distance from centerline, mm

Ver

tical

dist

ance

from

cent

erlin

e,m

m

-20 -10 0 10 20

-20

-10

0

10

300m/s

33--D Velocity distribution within axial plane 5D Velocity distribution within axial plane 5--mm from exit. mm from exit. Inlet conditions: TInlet conditions: Tinin = 617K, P= 617K, Pinin = 1030 = 1030 kPakPa, , φφ = = 0.45 0.45

As with the PIV result above, the velocity distribution shown here is uncorrected for optical thickness.

Axial V:contour

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SummarySummary

We performed the first of a series experiments to obtain baseline data for validating the NASA National Combustor Code using a 9-point LDI.

Species measurements• PLIF images of fuel and OH were acquired and compared to similar PLS images

from liquid fuel. Optical thickness/absorption are the primary issues to address.• Image results show that this LDI atomizes and vaporizes fuel quickly.

Chemiluminescence images are useful for determining the overall symmetry of the system.

Velocity meas—promising preliminary results despite tech issues • Our first velocity/sizing measurements provide allow us to assess technique

implementation determine how to improve. In general, we were successful• PIV results show the presence of recirculation zones immediately downstream of

the injector as predicted.• A qualitative comparison of the axial air velocity from experiment and NCC code

indicates a strong general agreement. • Future velocity/turbulence/drop sizing, etc. measurements will need to address

probable optical density/optical access issues, particularly for Phase Doppler

nasa 9-point ldi code validation experiment 9-point ldi code validation experiment yolanda r. hicks,...

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