Tests were performed at typical engine idle conditions on a single-can JT8D combustor installed in a 24 centimeter (9.45 in.) housing to evaluate the effect of an air-assist nozzle on reducing exhaust emissions. By injecting high-pressure air through the secondary-flow passage of a standard duplex fuel nozzle, it was possible to reduce hydrocarbon emissions from 840 parts per million to 95 parts per million and carbon monoxide emissions from 873 parts per million to 258 parts per million. NOX emissions increased slightly from 18 parts per million to 22 parts per million. An air-assist differential pressure of only 20.1 newtons per square centimeter (29.1 psi) and an airflow rate of only 0.22 percent of the total combustor airflow was required

Jones, R. E.

Papathakos, L. C.

English

NASA Technical Reports Server

NASA TECHNICAL
MEMORANDUM
I
X
NASA TM X-2946
USE OF AN AIR-ASSISTED FUEL NOZZLE
TO REDUCE IDLE EMISSIONS OF
A JT8D ENGINE COMBUSTOR
by Leonidas C. Papathakos and Robert E. Jones
Lewis Research Center
Cleveland, Ohio 44135
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION • WASHINGTON, D. C. • NOVEMBER 1973
https://ntrs.nasa.gov/search.jsp?R=19740003625 2020-03-23T12:24:08+00:00Z
1. Report No.
NASA TMX -2946
2. Government Accession No.
4. Title and Subtitle
USE OF AN AIR-ASSISTED FUEL NOZZLE TO REDUCE IDLE
EMISSIONS OF A JT8D ENGINE COMBUSTOR
7. Author(s)
Leonidas C. Papathakos and Robert E. Jones
9. Performing Organization Name and Address
Lewis Research Center
National Aeronautics and Space
Cleveland, Ohio 44135
Administration
12. Sponsoring Agency Name and Address
National Aeronautics and Space Administration
Washington, D. C. 20546
3. Recipient's Catalog No.
5. Report Date
November 1973
6. Performing Organization Code
8. Performing Organization Report No.
E-7580
10. Work Unit No.
501-24
11. Contract or Grant No.
13. Type of Report and Period Covered
Technical Memorandum
14.- Sponsoring Agency Code
15. Supplementary Notes
16. Abstract
Tests were performed at typical engine idle conditions on a single-can JT8D combustor
installed in a 24 centimeter (9. 45 in.) housing to evaluate the effect of an air-assist nozzle
on reducing exhaust emissions. By injecting high-pressure air through the secondary-flow
passage of a standard duplex fuel nozzle, it was possible to reduce hydrocarbon emissions
from 840 parts per million to 95 parts per million and carbon monoxide emissions from
873 parts per million to 258 parts per million. NO emissions increased slightly from 18
parts per million to 22 parts per million. An air-assist differential pressure of only 20.1
newtons per square centimeter (29.1 psi) and an airflow rate of only 0. 22 percent of the
total combustor airflow was required.
17. Key Words (Suggested by Author(s))
JT8D engine Air pollution
Turbojet engine Spray nozzles
Combustor
Exhaust effluents
19. Security Classif. (of this report)
Unclassified
18. Distribution Statement
Unclassified - unlimited
20. Security Classif. (of this page) 21. No. o
Unclassified 9
f Pages 22. Price*
Domestic, $2.75
Foreign, $5.25
* For sale by the National Technical Information Service, Springfield, Virgiria 22151
USE OF AN AIR-ASSISTED FUEL NOZZLE TO REDUCE IDLE
EMISSIONS OF A JT8D ENGINE COMBUSTOR
by Leon Idas C. Papathakos and Robert E. Jones
Lewis Research Center
SUMMARY
Tests were performed at typical engine idle conditions on a single-can JT8D com-
bustor to evaluate the effect of an air-assisted fuel nozzle on reducing exhaust emis-
sions. The combustor was installed in a 24 centimeter (9.45 in.) housing in a connected -
duct test facility; an existing instrumentation section, not specifically designed for
JT8D combustor dimensions,' was utilized for comparative emission measurements.
By injecting high-pressure air through the secondary-flow passage of the standard du-
plex fuel nozzle, it was possible to reduce hydrocarbon emissions from 840 parts per
million to 95 parts per million and carbon monoxide emissions from 873 parts per mil-
lion to 258 parts per million. NO emissions increased slightly from 18 parts per mil-
X
lion to 22 parts per million. An air-assist differential pressure of only 20.1 newtons
per square centimeter (29.1 psi) and an airflow rate of only 0.22 percent of the total
combustor airflow was required.
INTRODUCTION
An investigation was conducted to determine the feasibility of converting the con-
ventional duplex fuel nozzle of the JT8D combustor to an air-assisted fuel nozzle to pro-
vide a simple means of reducing combustion emissions at idle.
The proposed 1979 regulations of the Environmental Protection Agency limit the
levels of emissions at idle. Meeting these regulations will be a difficult task. Ulti-
mately, changes in the design of the combustor may be required.
The use of an air assist fuel nozzle has been shown to be a way of reducing com-
bustion emissions at idle. In reference 1 the conventional duplex fuel nozzles of a J-57
combustor were converted to air-assisted nozzles for engine idle operation. This was
possible because during idle only the primary nozzle is flowing fuel. The secondary
nozzle, normally used during high power operation is not active during idle operation
and air can, therefore, be injected through this nozzle. The injected air serves to
finely atomize the fuel resulting in more complete combustion, hence lower emitted
levels of CO and THC. In practice this could be accomplished by bleeding a small
quantity of air from the compressor exit, supercharging it and then injecting it through
the secondary fuel nozzle. At higher power levels, the airflow and supercharger are
valved out of the fuel system.
The amount of injected air required to cause a significant change in emissions is
very small. In reference 1, an airflow rate of less than 0. 5 percent of the total engine
airflow at a supercharged pressure ratio of 4 decreased THC emissions by 69 percent
and CO emissions by 20 percent.
These tests were conducted on a typical JT8D engine combustor can and fuel noz-
zle to determine what improvement in idle emission might be expected by using the air-
assist approach. The JT8D combustor was chosen for this investigation because a
major retrofit involving the installation of a new fan is being considered for this engine.
The air-assist nozzle conversion, if successful in substantially reducing idle emissions
could become a part of the JT8D engine retrofit. All tests were conducted at the speci-
fied engine idle operating conditions. No attempts were made to improve idle emissions
by any other means. ASTM-Jet A fuel was used for all tests.
APPARATUS AND PROCEDURE
The test facility is shown schematically in figure 1. This is a connected-duct
combustor test facility with inlet-air temperature, pressure and airflow rates all inde-
pendently variable. The JT8D combustor can was installed in a modified test housing as
shown in figure 2. The instrumentation and gas analysis sampling probe locations are
noted on this figure. This test facility, while not ideally matched to the size of the JT8D
combustor was used to expedite the test program. The facility had been used to deter-
mine odor characteristics of the exhaust gases from a J57 combustor as described in
reference 2. An insert 24 centimeters (9.45 in.) in diameter was installed to reduce the
reference area to a value typical for the JT8D combustor as installed in an engine.
Gas Sampling and Analysis
The exhaust emission sampling probe is shown in figure 3. Gases collected by
eight such probes were passed through steam-heated lines to the gas analysis instru-
ments shown in figure 4. Unburned hydrocarbon concentrations were measured with a
flame-ionization detector, CO and CO concentrations were measured with NDIR instru-
r"
L tv>
— 1
i o.
3
Q_
Section A-A
(Combustion inlet)
Section B-B Section C-C
(Thermocouple (Gas sample
location) Probe location)
(a) Instrumentation stations.
O Total temperature
a Gas sample probe
A Static pressure
8 Probes
-Insert
Airflow O30.3 cm(11.94 in.
_ 69.3 cm
(27.3 in . )
24.7 cm
(9.74 in. I
10.2 cm
(4 i n . )
\ ^-Insulation
\
\-Liner
(b) Location of instrumentation at each station.
Figure 2. - Combustor test duct.
C-73-2411
Figure 3. - Five-point steam-cooled exhaust emission
probe.
Control cluster A(un-
burned hydrocarbons)-* control
• -analyzer
x
- Control cluster C
CO control
analyzer
Control clus-
ter D (C02)
, Filters:
Bypass flow
indicator
and control
NOX converter switch
I-NO pump switch
C-71-3941
Figure 4. - Gas analysis equipment.
ments and NO and NO with a chemiluminescence instrument equipped with a thermal
X
converter (ref. 3).
Test Conditions
The test conditions for all testing are listed in table I. These test conditions are
representative of the actual installed engine conditions during ground idle.
RESULTS AND DISCUSSION
The test data obtained are summarized in table II. The variations of the concentra-
tions of CO, THC, and NO with increasing atomizing air pressure are shown in figure 5.
A.
No significant reduction in emissions occurs until the air-assist differential pressure
exceeds about 7 newtons per square centimeter (10.2 psi). Beyond that value, there is
a rapid decrease in the concentration of unburned hydrocarbons and carbon monoxide.
At a differential pressure of 20.1 newtons per square centimeter (29.1 psi) the concen-
tration of unburned hydrocarbons has been reduced approximately 88 percent and the con-
centration of CO approximately 70 percent. There was a slight increase in the level of
NO emissions, from 17 to 22 parts per million.
Ji
Some further reduction in emissions levels of THC and CO might be expected at
still greater atomizing air pressures. However, it seems apparent that these changes
might be small and are probably not justifiable when weighed against the increased pres-
sure ratio required of the supercharger. No differential pressures greater than those
shown were used in this effort; reference 1 clearly indicates that the gains achieved by
increasing supercharger pressure ratios above a value of four are insignificant.
The air-assisted flow rate at a pressure differential of 20.1 newtons per square
centimeter (29.1 psi) was calculated to be 0.0030 kilogram per second (0.0066 Ib/sec) or
approximately 0.22 percent of the combustor airflow rate.
Because the exhaust instrumentation section was not designed specifically for the
JT8D geometry, no attempt was made to compute emission index values or to relate these
measured changes in emissions to actual changes in combustion efficiency. However,
these tests do indicate that this air-assisted nozzle conversion has the potential to make
a significant reduction in JT8D engine idle emissions.
TABLE I. - JT8D IDLE OPERATING CONDITIONS
Airflow rate, kg/sec (Ib/sec) 1.35 (2.98)
Inlet air temperature, K (°F) 382(228)
o
Inlet air pressure, N/cm (psi) 24.0(34.8)
Fuel-air ratio 0.0112
TABLE II. - TEST RESULTS
iCombustor inlet temperature, 382 K (228° F); combustor inlet pressure, 24.2 N/cm
(35.1 psi); airflow, 1. 37 kg/sec (3.01 lb/sec).l
Fuel-
air
ratio
0.0115
.0112
.0114
.0113
.0112
.0112
.0112
Combustor exit
temperature
K
782
796
790
797
778
780
780
°F
948
973
963
975
941
944
944
Exhaust emissions,
ppm
Hydro-
carbons
840
95
289
124
763
785
785
Carbon
monoxide
873
258
455
307
886
869
871
Oxides
of
nitrogen
NOX
17.9
22.3
19.3
21.5
16.7
16.6
16.6
Primary nozzle
(fuel)
pressure
differential
2
N/cm
110. 1
107.6
106.1
104.7
103.9
103.4
103.0
psi
159.7
156.1
153.9
151.9
150.7
149.9
149.4
Secondary nozzle
(air)
pressure
differential
9
N/crn
0
20.1
11.7
15.6
5.8
0
0
psi
0
29.1
16.9
22.7
8.4
0
0
X
o
O1—
Air-assist differential pressure, N/cm'
10 15 20 25
Air-assist differential pressure, psi
30 35
Figure 5. - Variation of idle emissions with air-assisted nozzle differential pressure.
Combustor inlet temperature, 382 K (228° F); combustor inlet pressure, 24.2 new-
tons per square centimeter (35.1 psi); airflow, 1.37 kilograms per second (3.01
Ib/sec); fuel-air ratio, 0.0113.
SUMMARY OF RESULTS
A test program to evaluate the potential of an air-assist fuel nozzle conversion for
reduction of idle emissions of a JT8D combustor produced the following results:
At an air-assisted nozzle pressure differential of 20.1 newtons per square centi-
meter (29.1 psi) unburned hydrocarbon levels in the exhaust were reduced by 88 percent
and CO levels were reduced by 70 percent of the values with no air-assisted fuel atomi-
zation. An airflow rate of only 0.22 percent of the total combustor air flow was required
to achieve these levels of emissions reduction.
Lewis Research Center
National Aeronautics and Space Administration,
Cleveland, Ohio, August 21, 1973,
501-24.
REFERENCES
1. Briehl, Daniel; and Papathakos, Leonidas: Use of an Air-Assist Fuel Nozzle to Re-
duce Exhuast Emissions from a Gas-Turbine Combustor at Simulated Idle Conditions.
NASATND-6404, 1971.
2. Kendall, David A.; and Levins, Philip L.: Odor Intensity and Characterization of
Jet Exhaust and Chemical Analytical Measurements. Rep. ADL-74443, A. D. Little,
Inc. (NASA CR-121159), Mar. 1973.
3. Anon.: Procedure for the Continuous Sampling and Measurement of Gaseous Emis-
sions from Aircraft Turbine Engines. Aerospace Recommended Practice 1256,
SAE, Oct. 1971.
NASA-Langley, 1973 33 E-7580
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 2O546
OFFICIAL BUSINESS
PENALTV FOR PRIVATE USE S3OO SPECIAL FOURTH-CLASS RATE
BOOK
POSTAGE AND FEES PAID
NATIONAL AERONAUTICS AND
SPACE ADMINISTRATION
451
POSTMASTER : If Undeliverable (Section 158Postal Manual) Do Not Return
"The aeronautical and space activities of the United States shall be
conducted so as to contribute . . . to the expansion of human knowl-
edge of phenomena in the atmosphere and space. The Administration
shall provide for the widest practicable and appropriate dissemination
of information concerning its activities and the results thereof."
—NATIONAL AERONAUTICS AND SPACE ACT OF 1958
NASA SCIENTIFIC AND TECHNICAL PUBLICATIONS
TECHNICAL REPORTS: Scientific and
technical information considered important,
complete, and a lasting contribution to existing
knowledge.
TECHNICAL NOTES: Information less broad
in scope but nevertheless of importance as a
contribution to existing knowledge.
TECHNICAL MEMORANDUMS:
Information receiving limited distribution
because of preliminary data, security classifica-
tion, or other reasons. Also includes conference
proceedings with either limited or unlimited
distribution.
CONTRACTOR REPORTS: Scientific and
technical information generated under a NASA
contract or grant and considered an important
contribution to existing knowledge.
TECHNICAL TRANSLATIONS: Information
published in a foreign language considered
to merit NASA distribution in English.
SPECIAL PUBLICATIONS: Information
derived from or of value to NASA activities.
Publications include final reports of major
projects, monographs, data compilations,
handbooks, sourcebooks, and special
bibliographies.
TECHNOLOGY UTILIZATION
PUBLICATIONS: Information on technology
used by NASA that may be of particular
interest in commercial and other non-aerospace
applications. Publications include Tech Briefs,
Technology Utilization Reports and
Technology Surveys.
Details on the availability of these publications may be obtained from:
SCIENTIFIC AND TECHNICAL INFORMATION OFFICE
NATIONAL A E R O N A U T I C S A N D S P A C E A D M I N I S T R A T I O N
Washington, D.C. 20546


Use of an air-assisted fuel nozzle to reduce idle emissions of a jt8d engine combustor

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server