GaS Turbine Exhaust System

Question 1

How does the exhaust system work?

Answer 1

~jet pipe
~a propelling nozzle
~exhaust cone

Gas trubine exits at around 370m/s this would create friction losses.
To reduce this is fitted with an exhaust cone with a divergent duct
The cone helps to keep the speed at around 290m.s (0.5 mach) unitl it reaches the propelling nozzle.
Within the propeller nozzle the spees can be increase to mach 1 ,no further increased in speed is achieved wihtout adding additoinal heat

The static pressure within the exhaust is now above atmospheric and its said is choked , pressure thrust will be increased.

Question 2

Cold air insulation

Answer 2

Tne exhaust air existing from the core is mixed with high by pass air to reduce the noise

Question 3

Scarfing

Answer 3

Creates some turbulent air to mix the cold air with the hot core air

Question 4

Reverse bucket thrust

Answer 4

Cold stream reversal is the standard method for larger engines
~to increase reverse thrust to N1 and N2 rotation need to be increased
~pressure thrust will also increase ,but reverse thurst has the greates effect
~gas flow 130 degres in direction

Question 5

Reverse thrust interlocks

Answer 5

At minimum there are three seprate locks:
~One located on the flight
~two operated and controlled by the engine (ground switch)

Question 6

Reverse mechanisms

Answer 6

Blocker doors are operated hydraulically

clamshells and buckets are all actuated pneumatically

Question 7

Temperature measurment

Answer 7

Thermocouples are used in different point of the engine such as
~EGT»exhaust gas temp (typically measured after turbine)
~TGT»turbine gas temp( between HPT-LPT)
~TET»turbine entry temp (measured ahead of the first nozzle)
~JPT»further back in the jet pipe