Gas Turbines Flashcards
What is primary air?
Primary air is 15% and it makes up the air for initial combustion via the burner and ignitor
What is secondary air?
Secondary air is 10%, creating layer of protection around the wall of the can preventing flame impingement leading to hot spots
What is tertiary air?
Tertiary air is the working air, this is the air used to drive the turbines
What is the purpose of the 3 stage filter
The 3 stage filter provides 3 levels of filtration for the airflow into the GT. The first stage removes moisture using spray eliminators, baffle plates create a divergent pass for the air which separates the water from the air. The second stage removes particles using a knit mesh filter and the third stage repeats the first stage removing more moisture. A manometric leg is contained within the filter to prevent unfiltered air entering the GT
What does the splitter/silencer do?
It reduces noise and turbulence within the air flow
What does the stone guard do?
The stone guard removed any large coarse
particles that gain access to the intake airflow
What does the transition duct do?
It changes the airflow from square to cylindrical reducing turbulence
What does the cascade bend do?
It smoothens airflow using a long 90 degree bend
What does the intake flare do?
It seals the engine and houses the water wash ring
Describe the induction of a GT
The pre filtered air enters the GT to begin compression.
Describe the compression stage of the GT
The compression is separated into two stages, firstly it goes through an LP compressor which increases the pressure of the air using a series of rotating blades with divergent passages. It then goes through a HP compressor using a second set of rotating blades the pressure increases even more, as the airflow speed decreases the pressure increases. A 19:1 ratio of air compression can be achieved.
Describe the combustion stage of the GT
The compressed air enters a combustion chamber where combustion cans provide initial combustion using igniters at 2000v. The burners ignite atomised fuel, combined with the hot, compressed air creates combustion, the energy created is used to power the turbines.
Describe the power stage of the GT
The working fluid leaves the combustion chamber and enters a series of turbines. The hot gases drive an LP and HP turbine acting like a waterwheel being driven by water. The turbines are connected to the compressors so once they begin turning they will turn the compressors allowing the GT to become self sustaining when up to speed. 1/3rd of the energy produced is lost to the turbines. The remaining energy powers the power turbine causing it to rotate, this rotary force drives the gearbox
Describe the exhaust stage of the GT
Once the exhaust gases have passed through the turbines they are directed away via a funnel into the atmosphere
What is flame impingement?
Flame impingement is when the fire generated from combustion creates hot spots on the walls of the combustion can
