Experimental Study of Gas Turbine Combustion with Elevated Fuel Temperatures

Heather WiestRegion H – Purdue University

Lightning Talk – Thursday, October 24, 2013

WE13 – The Annual Conference for Women EngineersBaltimore, MD

How Does a Gas Turbine Engine Work?

Thrust - for every action there is an equal and opposite reaction!

My Research Area

Types of Combustors

Can Cannular Annular

Design Considerations for Gas Turbine Engines

o Lower primary emissions.o NOx – Oxides of Nitrogeno CO – Carbon Monoxideo UHC – Unburned Hydrocarbons

o Increase combustion efficiency.o Minimize pressure fluctuations.

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!

Issues with Heated Fuelso 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.

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.

Combustion Rig

Pressure Vessel

Schematic of Experimental Setup

Air Flow

Fuel Flow

Water Flow

Exhaust Flow

Emissions Probe

Nitrogen Flow

Pressure Vessel

Fuel Heaters

PressureControlValve

Experimental Setup

Experimental Setup

Fuel Heaters Emissions Probe

Test Conditions

0 100 200 300 400 500 600 700 8000

50

100

150

200

250

300Fuel Vapor PressureTest Points

Fuel Temperature [°F]

Com

bu

stor

Pre

ssu

re [

psi

a]Set fuel flow rates, air flow rate, combustor pressure, and temperatures to simulate engine conditions:

o Maxo Ground Idleo Cruiseo Flight Idle

Fuel Flashing Region

Results – Combustion Efficiency

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.000.9980

0.9982

0.9984

0.9986

0.9988

0.9990

0.9992

0.9994

R1

Fuel Temperature [°F]

Com

bu

stio

n E

ffic

ien

cy

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.

Emissions Tradeoff

1 10 1000

2

4

6

8

10

12Modified Fuel Injector - Ambient Fuel Tempera-tureLegacy Fuel Injector - Ambient Fuel TemperatureModified Fuel Injector - 250°F Fuel TemperatureLegacy Fuel Injector - 250°F Fuel TemperatureModified Fuel Injector - 450°F Fuel Temperature

Carbon Monoxide Emissions Index [g/kg]

Oxi

des

of

Nit

roge

n E

mis

sion

s In

dex

[g/

kg]

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.

Questions?

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!

Data Reduction

η=1−𝑌 𝐶𝑂𝑄𝐻𝑉 𝐶𝑂

+𝑌 𝑈𝐻𝐶𝑄𝐻𝑉𝑈𝐻𝐶

1

1+1

𝐹𝐴𝑅𝑄𝐻𝑉 𝑓

Combustion Efficiencyo Compares the heat generation of the

fuel to the exhaust stream.o Based on emissions measurements.o Assumed CH1.92 ratio.

𝐸𝐼𝑝=𝑚𝑎𝑠𝑠𝑜𝑓 𝑝𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 𝑖𝑛𝑔𝑚𝑎𝑠𝑠𝑜𝑓 𝑓𝑢𝑒𝑙𝑢𝑠𝑒𝑑𝑖𝑛𝑘𝑔

Emissions Indexo Computes for major pollutants: NOx,

CO, and UHC.o Normalizes pollutant measure by fuel

flow rate.o ICAO Annex 16 Volume 2.

Gas Turbine Combustor Requirements

o High Combustion Efficiencyo Reliable Smooth Ignitiono Wide Stability Limits for Operationo Low Emissions of Smoke and Gaseous Pollutantso Minimum Cost and Ease of Manufacturingo No Pressure Fluctuations or Combustion Instabilities