clear exhaust from the airframe

to shield turbine disc rear face and slow gases velocity

optimize thrust at the outlet from the engine.

pressure thrust.

the basic form and the earliest type of turbojet engine

accelerate the airflow from the turbine to make thrust

at the last stage of the turbine

reduce noise, by induce cooled air to mix with hot gases.

slow down aircraft speed on ground

less than max due to structural limits (low power and low forward speed)

the turbine

pure jet and low by pass engine

to prevent inadvertent operation of thrust reversal in commercial air transport

gas flow is mach1 at the exit