Lab 9 - Gas Turbine Combustor
(Recommended material: Chapter 9 – Emissions)
 Video demonstrations of this lab can be found on YouTube at
http://www.youtube.com/user/FndmtlsofCombustion
The combustor investigated in this lab is typical of gas turbines systems. The
fuel is injected as a liquid and sufficient air is provided near the injector to achieve
approximately stoichiometric mixing. Because the combustion products flow directly into the turbine, additional air is added downstream of the combustion region to cool the product gases to temperatures compatible with the material of the
blades.
Fuel
Compressed
air
Combustion
products
Combustor
Cool air
Air
Exhaust
Compressor
Turbine
Work out
In this lab, the combustion characteristics of a can combustor burning liquid
heptane are explored. In the first part of the lab, the ratio of the fuel and air flow
2
rates are such that combustion is lean overall (excess of air). The flow rates of
both fuel and air are increased while keeping the equivalence ratio constant. However, as the flow rates increase, the residence time decreases. The change in emissions of CO, CO2, NOx, and hydrocarbons are monitored by gas analyzers. In the
second part of the lab, the overall equivalence ratio is varied by changing the flow
rate of air while holding the flow rate of fuel approximately constant. The change
in emissions is monitored here as well. In both parts of the lab, note the appearance of the flame including its color, shape, size and location in the combustor and
changes as the flow rate is changed.
Exercises
1. Plot the mole fractions of CO, CO2, and NOX as a function of
a. Mixture flow rate (fuel + air flow rate)
b. Equivalence ratio
Discuss the trends.