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
Where are annular combustion chambers most used??
. On modern gas turbine engines
How does an annular combustion chamber work?
Only has one annular flame tube which is supported by and inner and outer combustion chamber casing
What are three main parts of combustion chamber?
. The dome
. Inner lining
. Outer lining
The flame tubes on an annular are often called what?
Combustion chamber
What are the advantages of an annular combustion chamber?
. Smaller and lighter
. Better efficiency
. Better thermal load distribution
. Very long service life
What are some disadvantages of the annular type annular combustion chamber?
. Expensive
. Removal is very hard
What is the purpose of the of a flame tube?
It stabilises the flame during combustion
What are the external components of a combustion chamber?
. Fuel nozzles
. Igniter plugs
2hat are the 3 main parts of the combustion case??
. Inner wall
. Outer wall
. Diffuser
What is the last stator valve of HP compressor??
Exit guide vanes
Stator vanes of the last stage of the HP compressor are known as??
Guide vanes
The outer wall of the combustion chamber case has opening for?
. Bleed air from HP compressor for pneumatics
The openings for fuel nozzles and igniter plugs used for?
Used for borescope inspections of flame tube
What are the main components of the flame tube assembly?
. Outer and inner liner
. Outer and inner cowl
. Dome
What else does the dome house?
Swirl vanes
How is the flame tube fixed?
Fixed in all three dimensions at the aft end
Another type of flame tube is made by?
Two pieces
How does primary airflow enter the flame tube??
Through swirl vanes
How does secondary airflow enter the flame tube??
Passes the cowl and enters the flame tube through liners
What is the cooling method of secondary airflow called??
Film cooling method
Why do we have film cooling?
To protect the liners inside from the intense heat of combustion gases
What are the three types of film cooling methods??
. Corrugated station cooling
. Machined cooling ring
. Splash cooling strip
What is the newest/ most sophisticated method of cooling?
. Transpiration
Which requires less aid for cooling the flame tube lines
What is another method to protect materials against heat??
. Thin coating of ceramic materials on the inner surface if the flame tube
