The main objectives of the NASA-sponsored Aerothermal Modeling Program, Phase 2--Element C, are experimental evaluation of the air swirler interaction with a fuel injector in a simulated combustor chamber, assessment of the current two-phase models, and verification of the improved spray evaporation/dispersion models. This experimental and numerical program consists of five major tasks. Brief descriptions of the five tasks are given

Mcdonnell, V. G.

Mongia, H. C.

Mostafa, A. A.

Samuelsen, G. S.

English

NASA Technical Reports Server

N89- 12892
AEROTHERMAL MODELING PROGRAM--PHASE II*
ELEMENT C: FUEL INJECTOR-AIR SWIRL CHARACTERIZATION
A.A. Mostafa, H.C. Mongia, V.G. McDonnell_, and G.S. SamuelsenT
Allison Gas Turbine Division
General Motors Corp.
The main objectives of the NASA-sponsored Aerothermal Modeling Program, Phase II
Element C, are experimental evaluation of the air swirler interaction with a fuel
injector in a simulated combustor chamber (Figure I), assessment of the current
two-phase models, and verification of the improved spray evaporation/dispersion
models.
This experimental and numerical program consists of five major tasks. Tasks I and
2 have been completed. Brief descriptions of the five tasks are given in the fol-
lowing paragraphs.
TASK 1--EXPERIMENTAL CONFIGURATION
This task involved preliminary design of the test section, its details for fabri-
cation, and the experimental plan for data acquisition.
The aim of the experiment is to collect benchmark quality data to study the inter-
action of the fuel spray with a swirler typical of current use in aircraft turbine
engines.
The fuel nozzle and swirler combination is operated at both unconfined and confined
conditions (152 mm duct). The experimental plan covers a wide range of tests of
varying complexity, with the constituent flows measured separately and then in com-
bination. The duct is designed in such a way to enable the required measurements
to be taken at the inlet plane and at seven axial locations downstream of the
swirler-fuel injector combination. The measurements include the following quanti-
ties: the three components of mean and root mean square (rms) gas velocity as well
as Reynolds stresses, the three components of mean and rlns droplet velocity, Sauter
mean diameter, droplet size distribution, spatial distribution of droplets, cone
angle, fraction of liquid evaporated in the duct (vapor concentration), the static
pressure along the wall of the duct, and the inlet air temperature.
All the test configurations (Figure 2) are first operated free of injected par-
ticles (except for the laser anemometer seed), second with injected monodisperse
solid particles (50-micron glass beads) through a diameter jet tube, 24 mm, then
with injected solid particles of two sizes (50 and I00 _m glass beads), and
finally with a fuel spray (methanol) through an aircraft-type airblast atomizer.
*Work done under NASA Contract NAS3-24350.
1_Jniversity of California at Irvine.
125
https://ntrs.nasa.gov/search.jsp?R=19890003521 2020-03-20T04:35:52+00:00Z
TASK2--MODELINGSENSITIVITYANALYSIS
Allison had run its 2-D codes (parabolic and elliptic) to predict the distribution
of the flow field variables for all proposed flow and geometry test conditions of
the experimental test matrix. The main purpose of this task was to determine if
the planned experiment is sensitive to the significant variables and which variable
and boundary conditions had to be measured.
This effort resulted in two main modifications in the original test plan. First,
the 457.2 mm duct that is concentrically located around the nozzle/swirler assembly
to simulate the unconfined conditions was replaced by one made of screen mesh.
The reasoning was that the permeable wall would permit the entrainment of air that
would otherwise necessitate recirculation. Second, the flow rates through the fuel
nozzle and the swirler and the low velocity stream of confinement were optimized
to avoid spray impingements on the tube wall within the measurements region.
TASK 3--MEASUREMENTS
The efforts of this task have been directed to (I) the testing of the facility,
(2) the verification of the two-component laser interferometer diagnostics (see
Figure 3), and (3) the acquisition of test data in the spray chamber.
The utility, applicability, and accuracy of phase Doppler (PD) has been tested in
a series of experiments in which the technique has been compared to visibility/
intensity validation and laser diffraction using a Malvern (see ref. 1 and 2).
The PD compared well to the visibility technique with intensity validation (VIS/
IV), and exhibits major advantages in the dynamic range of both droplet size and
droplet velocity. In trials with laser diffraction using a commercial Malvern
analyzer, the composite line-of-sight measurement of spatial-SMD deduced from the
PD measurements compares favorably to the single line-of-sight Malvern measurement
of spatial-SMD. It is noteworthy that the two measurements are best aligned for
the Model-Independent algorithm of the Malvern rather than the Rosin Rammler.
Example data for both the injection of 50 _m beads and the methanol spray are
presented in Figures 4 and 5. Although data are taken at seven axial locations,
only four are shown for clarity. The glass bead data (Figure 5a) display the axial
mean velocity of both the bead and gaseous phase velocity, as well as the bead
number density. The centerline hump in the bead number density is clearly dis-
cernable in the photograph (Figure 4a). The methanol spray data (Figure 5b) re-
flect the strong influence of the swirl in both the radial spread of the spray and
the radial profiles of both SMD and mean axial velocity.
TASK 4--RESULTS AND ANALYSIS
Experimental data of Task 3 will be reduced and presented in a format suitable to
make direct comparison with model predictions and to quantify the effects of the
flow and geometric variables in various transport processes.
TASK 5--MODEL IMPROVEMENT
A mathematical model for turbulent evaporating sprays based on the recent work in
that area (ref. 3-5) will be validated in this effort. This model will include
improved submodels for spray injection, turbulence/droplet interaction, and droplet
evaporation.
126
REFERENCES
o Jackson, T. A., and Samuelsen, G. S., "Spatially Resolved Droplet Size Measure-
ments," Journal of Engineering for Gas Turbines and Power, Vol. 108, No. I,
pp. 196-205, 1986.
2. Jackson, T. A., and Samuelsen, G. S., "Droplet Sizing Interferometry: A Com-
parison of the Visibility and Phase Doppler Techniques," Applied Optics, in
press.
, Mostafa, A. A., and Elghobashi, E. E., "A Two-Equation Turbulence Model for
Jet Flows Laden with Vaporizing Droplets," Int. J. Multiphase Flow, II, pp.
515-533, 1985.
4 o Rizk, N. K., Mostafa, A. A., and Mongia, H. C., "Modeling of Gas Turbine Fuel
Nozzles," Symposium on Calculations of Turbulent Reactive Flows, ASME 107th
Winter Annual Meeting, Nov. 30 - Dec. 5, 1986, Anaheim, California.
5. Mostafa, A. A., and Mongia, H. C., "Eulerian and Langrangian Predictions of
Turbulent Evaporating Sprays," AIAA Paper No. 86-0452, 1986.
127
Swiller
0__
0.25 -
0.375 -
0.50 -
X/D
0.75 -
1.0-
2.0-
Fuel nozzle
/
+
I
6 in. duct
Figure I. Experimental configuration for confined flow with
liquid fuel injection and swirl.
i_
injector
only
l
1
I
L_CONFI NED
injector
plus swirl
injector
only
CONFINED
injector
plus swirl
Figure 2. Experimental configurations.
128
.MALVER_
TRANSMITTERI I
SHADOWGRAPHI_ L_
CAMERA/ ""'-T ""
TRANSMITTER ' I/ I
LDA/PD ' / -, .... _- .
LASER I , " I i "
t .... -_....... "-
VlSllV " \_ /_
COLLECTION J "_[--'_- _ -;"_I
LENS _L\ / _ /
_/>VlSllV PMT
MALVERN I I
RECEIVER U
MICROFLASH---]
Figure 3. Flow facility and optical arrangement.
129
OR_C_L PAGE IS
OF POOR QUALITY
a) 50 um beads (unconfined; without swirl)
b) Methanol spray (unconfined; without swirl)
Figure 4. Representative data: photographs.
130
a)
x4/D - 0.375
x5/D • 0.500
%JD • 1,000
x_D=2.0OO
50 _m beads
(unconfined; without swirl)
I ).
-_! 1_,
_!3 "_ _,oooo
0.4
OBEA_ NUMBER
0GAS_'_ _
_,,
0.2 _ 0.2
r/D
DENSITY
0.4
b) Methanol spray (unconfined; 0 ° and 60 ° swirl)
50 _m
0° SWIRL
(3
:E
x41D- 0.375 ;
%/0 = 0,500
, %/D-1.000
xT/D • 2 000
9O
6O
3o E
o.
60 ° SWIRL
20
10
1 TEMPORAL-_PATIAL SMD
J O DROPLET
I
I
._._'x- ! _ , . -.-
0.4 0.2 CE 02 0.4 0.6
riD
Figure 5. Representative data: radial profiles.
131



Aerothermal modeling program, phase 2. Element C: Fuel injector-air swirl characterization

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