Questions tagged [combustion]

For questions specifically about the process of burning fuel.

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Would a pulsejet/turbine hybrid be efficient?

A pulsejet is an engine with a few moving parts (only the chamber shutters I think) in which fuel is injected in the combustion chamber, leading to a explosion that pushes air to the exhaust. After ...
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1 answer
111 views

Why is it that low fuel gauge is one indication of a compressor stall?

I am reading from my gas turbine engine class notes that apparently, one indication of compressor stall (besides the banging sounds, torque gauge low, N1 low, ITT gauge up, etc) is the fuel levels ...
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2 votes
1 answer
174 views

Why is a combustor in a gas turbine engine asymmetric?

As the above question stated, the upper and lower section of the combustor isn't same. Is there any reason behind it? Due to which the cooling of the combustor is also different in the upper and lower ...
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1 vote
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What is a typical fuel temperature entering the burner for different mission flight points of a civil aircraft?

Is there a target regarding the fuel temperature that enters the turbine engine's combustion chamber and if so does it change with different operation flight points in civil aircraft applications? Is ...
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1 vote
2 answers
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Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)? [closed]

Also, what is the maximum fuel:air ratio possible in a combustion chamber of a jet engine?
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4 votes
1 answer
227 views

What's the name of this part of combustion chamber and what is it for?

There are two "excrescences" Near the end of diffuser of some combustion chambers. e.g. CFM56 and F101 What's the name of this part of combustion chamber and what is it for?
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1 vote
1 answer
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What is the fuel/air ratio of the CFM56-5A1 engine (in the A320 model)?

I could find the fan-bypass ratio, which was 6:1 (on some models 5:1) but I was unable to find the fuel to air ratio used in this engine. For reference, it is a high-bypass turbofan engine.
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4 votes
3 answers
417 views

How would exhaust heat recovery into the combustion chamber affect the efficiency of a jet engine?

So, a jet engine basically sucks in air, heats it up and spits it out, right? The hotter the air gets, the faster the exhaust velocity and thus the more efficient (Higher specific impulse). Now my ...
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1 answer
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What is the air/fuel mixture ratio in a turbojet engine?

How does it relates to stoichiometry ? What are the possible extinction accidents related to air/fuel mixture ratio ?
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1 vote
0 answers
90 views

When are pressure-swirl atomizers and airblast atomizers used?

I am a little confused as to when (during T/O, cruise, etc.) and how the combined pressure-swirl atomizer and airblast atomizer is used. Lefebvre writes that "the merits of the pressure-swirl ...
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4 votes
0 answers
80 views

Does/Can combustion instabilities occur in SCRAM jet?

I was told that combustion occurs at Supersonic speeds in SCRAM jet. So acoustic disturbances/ pressure fluctuations can't travel into incoming jet stream. Does this avoids combustion instabilities in ...
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3 votes
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Is the combustion process in turbofans and turboshafts different?

According to a journal paper, for a Gnome turboshaft engine, fuel-air equivalence ratio decreases as power output increases. However, for a CFM56 turbofan engine, the opposite trend is true, and ...
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Can some one please explain to me the purpose of the combustion chamber? [duplicate]

Please, i need some one to explain to me the purpose of the combustion chamber in a jet engine, why do we need to burn the gases to get energy ? the compression does not suffice ?? is it possible to ...
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1 vote
1 answer
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What are the differences between single and double annular combustion chambers?

The combustion chamber of a jet engine may be can type or annular type. Annular type combustion chamber can be SAC (single annular combustion chamber) or DAC (double annular combustion chamber). What ...
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1 answer
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What is the difference between single and dual annular combustor?

CFM56 uses single annular and GEnX uses dual annular combustion chamber. somebody please explain with pics.
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2 votes
2 answers
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What is the Fuel-Oxygen ratio for a large turbofan at cruise conditions?

What is the Fuel-Oxygen ratio (by mass) for a large turbofan at cruise conditions? In order to be concrete, I'll just pick an engine at random. I pick the GE90-115B. Okay it's not really random, it'...
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13 votes
1 answer
3k views

How does a turbofan with afterburner continue to function in extreme humidity and rain?

From what I understand, the fan(s) collect(s) and compress(es) air into the compression chambers, where fuel is added to the air & combusted to create an even bigger pressure/thrust, right before ...
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3 votes
2 answers
2k views

What materials are used to make up a combustion chamber? [duplicate]

What type of materials are used to make up the different sections such as the linings of the combustion chambers in a gas turbine engine. Do these type of materials vary for the different types of gas ...
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5 votes
1 answer
3k views

What is the temperature of the air leaving the combustion chamber of a CFM56-5C?

What is the temperature of the air leaving the combustion chamber of a CFM56-5C? I was wondering as I could only find out that the fuel burns at around 1500 Celsius but this can't be the same as the ...
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5 votes
1 answer
667 views

Are flame holders made of a special material other than that used in combustion chamber?

Are the flame holders made of materials which have higher friction coefficients than the combustion chamber in order to create turbulence?
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5 votes
4 answers
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How is the correct air speed for fuel combustion obtained at the inlet of the combustor? [duplicate]

Many jet aircraft travel at speed of about Mach .8 which at an altitude of 11 km represents an airspeed of about 300 kt or 150 m/s. If fuel was injected into air at this speed, the mix would just ...
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7 votes
1 answer
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How is flame stabilisation carried out?

How is flame stabilization done in a jet engine combustion chamber? What are the various ways of doing this? What are the challenges/ problems faced?
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4 votes
2 answers
5k views

What is the absolute velocity change through compressor+burner?

I thought that the velocity going through a turbojet increased as it went through the compressor and the burner. Intuitively, if the pressure/enthalpy increases, so would the velocity, right? I came ...
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9 votes
3 answers
894 views

Why would a jet engine use cannular combustors if the annular design is superior?

Why are cannular type burners used in aircraft engines if annular type have more advantages over it?
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37 votes
4 answers
16k views

Why do gases in the combustion chamber only flow one direction to the gas turbine in a jet engine?

As far as I know from the working principle of jets engines, compressed air in the combustion chamber (or combustion canister) is mixed with fuel. The ignited mixture expands backwards to turn the ...
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