M15.05 Combustion Flashcards
What is the main function of the combustion chamber?
Produce hot stream of gas for turbines and jet nozzles
Briefly How does it produce the stream of hot gas?
By continuous combustion of fuel and air mixture
What 3 things ensure a safe and efficient combustion?
. Safe ignition
. No un burned fuel - combustion complete
. Stable combustion
What are the two main components of the combustion chamber?
. Combustion chamber casing - outer
. Flame tube - inside casing
The hosing of the combustion also does what??
Supports the flame tube, fuel nozzles and igniter plugs
What is the purpose of the flame tube??
Controls and guides the flame
It’s made of many segments with lots of holes and slots
What’s the basic combustion process?
. Compressed air into combustion chamber
. Fuel nozzles spray fuel into centre of airflow
. Fuel vaporises and mixes with airflow
. Then fuel/air is electrically ignited by igniter plug
. After combustion started the igniter is switched off
. Then it’s a continuous cycle
What is needed for safe and correct combustion?
. Ratio of air to fuel mist be correct
. Air velocity must be slow enough to ensure combustion is done in chamber
What’s the ratio of ketosene: air mixture??
15:1
Airflow form the compressor is split into what two parts?
. Primary airflow
. Secondary airflow
What is primary airflow used for and what % is used??
. Used for the combustion oricess
. 20 - 30%
What is secondary airflow used for and what % is used??
. Used for cooling (bypasses primary combustion zone, and mixes with hot gas in dilution zone)
. keeping the flame away from flame walls
. 70-80%
What is the other name for secondary airflow?
Bypass airflow
Why does the secondary air needs to keep the flame away from the flame walls?
Because the temperature in the centre if the flame reaches 2000 degrees
What are the 3 types of combustion chambers??
. Can-type combustion chamber
. Can - annular combustion chamber
. Annular combustion chamber
What temperature can the flame centre reach?
2000 degrees c
How does secondary airflow reach the dilation zone?
Through dilution air holes
Where are can- type combustion chambers found?
On old gas turbine engines with centrifugal compressors
How does a can- type combustion chamber work?
Multiple installed around the engine and connect to each other by interconnection tubes which allow ignition from each other
What’s the main advatange of the can- type combustion chamber?
Very simple deign
What’s the main negative of a can- type combustion chamber?
Heavy and need a lot of space
How does a can -annular type combustion chamber works?
Has a set of flame tubes installed around the combustion section. With all the flame tubes having a common inner and outer casing
What are a few advatanges of a can annular combustion chambers.
. Smaller and lighter
. Not complicated
What are 2 disadvantages of a can annular type combustion chamber?
. Difficult ignition
. Aerodynamic loss
