Reduction in unburned hydrocarbons from jet engine by use of air assist fuel nozzle is discussed. Operation of nozzle for improving combustion efficiency by improving fuel atomization is analyzed. Advantages to be achieved by air assist fuel nozzle are analyzed

Briehl, D.

Papathakos, L. C.

English

NASA Technical Reports Server

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July 1972 B72-10434 
NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Air Assist Fuel Nozzle Reduces Aircraft

Gas Turbine Engine Emissions at Idle Operation 
(For Takeoff
And Cruise)
Secondary
Fuel 
Supercharger 
IT L_Compressor	 I	 f Bleed Air	 I	 Primary (For Idle)	 Fuel 
The use of an air assist fuel nozzle has been shown 
to reduce the relatively large concentrations of carbon 
monoxide and unburned hydrocarbons from the com-
bustor of a conventional jet engine during idle operation. 
During idle and taxi of jet aircraft, the combustion 
efficiency is much lower than that at takeoff, landing, 
and cruise. Exhaust emissions of unburned hydrocarbons 
and carbon monoxide are therefore much higher during 
idle and taxi operation. The off-design conditions en-
countered at idle and taxi operations cause the com-
bustion efficiency to be at times well below 90 percent, 
while at take-off, landing, and cruise, the combustion 
efficiency is 98-100 percent. 
The conventional pressure atomizing fuel nozzles that 
are used in gas turbine combustors are unable to fully 
atomize the fuel spray at the low nozzle pressure differ-
entials that occur during idle fuel flow. The combustion
An air assist fuel nozzle has been evaluated (see the 
figure) that consisted of a system whereby a source of 
high pressure air was connected to the secondary 
chambers of conventional dual-orifice fuel nozzles. Fuel 
flow was introduced into the combustor through the 
primary chambers of the fuel nozzles. Using this system, 
idle efficiency increased from 90.3 percent to 96.5 
percent. The total unburned hydrocarbon and carbon 
monoxide emissions were decreased from 26 to 3.3 and 
from 51 to 40 grams per kilogram of fuel burned, 
respectively. 
In the application of air-assist fuel nozzles to a gas 
turbine engine, compressor bleed air, supercharged by a 
small compressor, could be supplied to the secondary 
side of the fuel nozzle during idle operation. During off-
idle operation the air assist flow would be valved off and 
fuel introduced into the combustor through the primary 
and secondary chambers of the fuel nozzles as required 
by the engine operating schedule. 
• efficiency may be improved by improving fuel atomiza-
tion. One way of doing this is by means of an air-assist 
fuel nozzle.
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000433 2020-03-17T03:39:58+00:00Z
•1 Notes: 
1. Substantial increases in combustion efficiencies and 
reductions of total unburned hydrocarbon and carbon 
monoxide emissions were accomplished at air assist 
pressure differential as low as 70 N/cm2 (102 psi). At 
this pressure differential, less than 0.5 percent of the 
combustor airflow is passed through the secondary 
side of the fuel nozzle. 
2. Application of this system to turbojet engines could 
also reduce fuel consumption at idle and taxi 
operation. 
3. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95)
Reference: NASA TN-D-6404 (N71.31456), 
Use of an Air Assist Fuel Nozzle to Reduce 
Exhaust Emission from a Gas Turbine Com-
bustor at Simulated Idle Conditions 
4. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10434 
Patent status: 
No patent action is contemplated by NASA. 
Source: D. Briehl and L. C. Papathakos
Lewis Research Center

(LEW-1 1512)
.. 
•S 
B72-10434	 Category 07


Air assist fuel nozzle reduces aircraft gas turbine engine emissions at idle operation

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