Aero Chapter 05/06 (TS) and 05 (ADV & IUT), Thrust and Thrust Curve Review
T-45 Aerodynamics Student Workbook
consumption, and a lower specific weight. The turbojet came first because it was simpler technology.
The turbofan engine is preferred in most modern applications.
The afterburner is a section added to some jet engines, which can provide a large thrust increase with
little weight. The afterburner section consists of another set of fuel spray nozzles, flame holders behind
the turbines, and variable exhaust nozzles. Since there are no highly stressed engine components
(turbine blades) behind the afterburner, a large amount of fuel can be burned there. Afterburners are a
very inefficient use of the fuel; however, as fuel flow will typically triple or quadruple in afterburner
operation for a 50% increase in thrust.
A single Rolls-Royce
turbofan engine that
installed static sea
level thrust of 5,527
thrust in the T-45.
Referring to Figure
79, air enters the
engine directly at the
first stage of N1.
components and N2
is typical of turbofan
airflow is divided into
two paths, one of
which enters the N2
and the other enters
Figure 79: T-45 TURBOFAN ENGINE
the annular bypass
duct. The airflow
from the N2 section then enters the combustion section where eighteen fuel spray nozzles provide fuel for
combustion. From the combustion section, the heated and accelerated airflow enters and flows through
the turbine section.
The N2 turbine turns the shaft, which drives the N2 compressor and engine accessory gearbox. The N1
turbine drives the N1 compressor (the engine fan) via the N1 shaft. There is no direct mechanical
connection between the N1 and N2 sections.
Airflow from the turbine section then moves into the exhaust section. The heated and accelerated airflow
is mixed with the airflow from the annular bypass duct. The mixed airflow then is discharged through a
fixed geometry, converging exhaust nozzle, the shape of which increases the thrust.