The document summarizes an experimental study on the effects of elevated fuel temperatures on gas turbine combustion. Key findings include: 1) Combustion efficiency increased with higher fuel temperatures due to improved vaporization and flow enthalpy. 2) Emissions of carbon monoxide and unburned hydrocarbons decreased with higher combustion efficiency. However, oxides of nitrogen emissions increased due to higher flame temperatures. 3) A modified fuel injector design led to higher oxides of nitrogen production but better combustion efficiency compared to the legacy design, especially at higher fuel temperatures.

1. Experimental Study of Gas
Turbine Combustion with
Elevated Fuel Temperatures
Heather Wiest
Region H – Purdue University
Lightning Talk – Thursday, October 24, 2013
WE13 – The Annual Conference for Women Engineers
Baltimore, MD

2. How Does a Gas Turbine Engine Work?
Thrust - for every action there is an equal and opposite reaction!
My Research Area

3. Types of Combustors
Can Cannular Annular

4. Design Considerations for Gas Turbine Engines
o Lower primary emissions.
o NOx – Oxides of Nitrogen
o CO – Carbon Monoxide
o UHC – Unburned Hydrocarbons
o Increase combustion efficiency.
o Minimize pressure fluctuations.

5. Benefits of Using Heated Fuels
o Thermal Management – increased
operating speeds lower the amount of heat
that can be dissipated to the surrounding air!
o Fuel Savings – less fuel is need to reach a
certain level of thrust!
o Emissions Reduction – can reduce the
amounts of carbon monoxide and unburned
hydrocarbons in the engine exhaust!

6. Issues with Heated Fuels
o Fuel Flashing – can negatively affect the
spatial and temporal uniformity of fuel
injection.
o Combustion Instabilities – can arise from
wide range of fuel properties during heated
process.
o Autoxidative Coking – can lead to
blockages in fuel lines and injectors from the
formation of solid deposits in fuel.

7. Research Project Objectives
o Characterize the burner performance and
emissions of a Rolls-Royce 501K combustor
with a newly modified fuel injector at
elevated fuel temperatures up to 600ºF.
o Compare the results with previously
collected data from testing with the legacy
501K fuel injector at fuel temperatures up to
450ºF.

8. Combustion Rig
Pressure
Vessel

9. Schematic of Experimental Setup
Air Flow
Fuel Flow
Water Flow
Exhaust Flow
Emissions
Probe
Nitrogen Flow
Pressure
Vessel
Fuel Heaters
Pressure
Control
Valve

10. Experimental Setup

11. Experimental Setup
Fuel Heaters Emissions Probe

12. Test Conditions
0
50
100
150
200
250
300
0 200 400 600 800
CombustorPressure[psia]
Fuel Temperature [°F]
Fuel Vapor Pressure
Test PointsSet fuel flow rates, air flow
rate, combustor pressure, and
temperatures to simulate engine
conditions:
o Max
o Ground Idle
o Cruise
o Flight Idle
Fuel Flashing
Region

13. Results – Combustion Efficiency
0.9983
0.9984
0.9985
0.9986
0.9987
0.9988
0.9989
0.9990
0.9991
0.9992
0.9993
0.9994
0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00
CombustionEfficiency
Fuel Temperature [°F]
R1
R2
o Combustion efficiency increases as fuel temperature was increased due
to increased flow enthalpy and improved fuel vaporization.
o Emissions results follow the trends in combustion efficiency:
o Increase in NOx as combustion efficiency increases due to higher
flame temperatures.
o Decrease in CO and UHC as combustion efficiency increases due to
more complete combustion.

14. Emissions Tradeoff
0
2
4
6
8
10
12
1 10 100
OxidesofNitrogenEmissionsIndex[g/kg]
Carbon Monoxide Emissions Index [g/kg]
Modified Fuel Injector - Ambient Fuel Temperature
Legacy Fuel Injector - Ambient Fuel Temperature
Modified Fuel Injector - 250°F Fuel Temperature
Legacy Fuel Injector - 250°F Fuel Temperature
Modified Fuel Injector - 450°F Fuel Temperature
Legacy Fuel Injector - 450°F Fuel Temperature

15. Conclusions
o Increased combustion efficiency as a result
of increasing fuel temperatures.
o Reduction in combustion efficiency for test
cases with low combustion pressures and
600ºF fuel temperatures.
o Modified fuel injector design led to an
increase in NOx production.
o Future studies include running laser
diagnostics on flow around fuel injector.

16. Questions?

17. Heated Fuel Applications - Scramjets
Lander, H. and Nixon, A.C. Endothermic fuels for hypersonic vehicles. J. Aircraft, 8(4), 200, 1971.
o Use fuel for regenerative
cooling of engine, similar
to rocket thrust chamber
cooling.
o Mach 8 Scramjet engine
could require a fuel heat
sink level of 1500 BTU/lb,
equivalent to fuel
temperatures on the order
of 1300ºF!

18. Data Reduction
η = 1 −
𝑌𝐶𝑂 𝑄 𝐻𝑉 𝐶𝑂
+ 𝑌𝑈𝐻𝐶 𝑄 𝐻𝑉 𝑈𝐻𝐶
1
1 +
1
𝐹𝐴𝑅
𝑄 𝐻𝑉 𝑓
Combustion Efficiency
o Compares the heat generation of the
fuel to the exhaust stream.
o Based on emissions measurements.
o Assumed CH1.92 ratio.
𝐸𝐼 𝑝 =
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑝 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 𝑖𝑛 𝑔
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑓𝑢𝑒𝑙 𝑢𝑠𝑒𝑑 𝑖𝑛 𝑘𝑔
Emissions Index
o Computes for major pollutants: NOx,
CO, and UHC.
o Normalizes pollutant measure by fuel
flow rate.
o ICAO Annex 16 Volume 2.

19. Gas Turbine Combustor Requirements
o High Combustion Efficiency
o Reliable Smooth Ignition
o Wide Stability Limits for Operation
o Low Emissions of Smoke and Gaseous Pollutants
o Minimum Cost and Ease of Manufacturing
o No Pressure Fluctuations or Combustion Instabilities