Airplane Engines - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 150

Fig. 10.3 Emissions of
pollutants from a gas turbine

100

NO x

10

CO

1.0

CH m
n

0.1

300 400 600 800 1 000

temperature [K]

low pressure and the low temperature in the combustion chamber which leads to
the production of unburned substances (see Fig. 10.3 )[ 19 ].
The Bypass Pressure Ratio (BPR) means the rate of air mass flow between the
engine bypass and the engine core. Increasing the BPR has limits in turbofans
because higher temperatures at the turbine rotor and compressor inlet produce
material problems [ 20 ]. In this section, improved vane and blade cooling and high
efficient compressors with heat resistant materials, e.g., plasma spray ceramic
protective layers and thermal barrier coatings on the surface (ZrO 2 Y 2 O 3 ), are still
needed [ 21 ].

10.5 Measurement in Turbofan Engines

Turbofans contain two mechanically independent rotors, one inside the other. The
fan, the low pressure compressor and the low pressure turbine are installed on the
inner rotor, called the N1 rotor. The outer rotor, called N2, holds the high pressure
compressor and turbine. It includes an intake valve to pass fuel to the engine, a
pump to increase fuel pressure, coolers, heaters and filters for the fuel, a second
pump to further raise the fuel pressure, a shut-off valve in front of the combustion
chamber and a fuel flow meter providing flow information to FMS.
Turbofans contain tubes for analyzing rotation speeds N1 and N2, Exhaust Gas
Temperature (EGT), fuel pressure, fuel temperature and fuel flow in the pipes, fuel
quantity in the tanks and filter saturation. The electronic engine control senses the
position of the thrust lever, compares the actual with the target N1. According to
the aircraft configuration and altitude, it automatically sets the engine thrust by
adjusting the fuel flow to achieve the target N1, commanded by the auto throttle
system or by the pilot.
Measuring points in the combustion and exhaust gas system are presented in
Fig. 10.4 .