34 votes
Accepted

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

It is actually not that simple to ensure the proper gas speed in a gas turbine. In the compressor you want to limit the flow speed over the compressor vanes to the high subsonic range, so the inlet ...
26 votes
Accepted

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

The air is compressed in the compressor section of the engine and heats up. Hot air is able to hold disproportionally more water in gaseous form than cold air, so all that water will vaporize and ...
20 votes

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

The air in the compressor is both compressed and moving downstream towards the combustion section. The combustion does not create enough pressure to overcome all of that, and there is lower pressure ...
  • 70.1k
14 votes

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

Disclaimer: I may have spent several hours on Wikipedia at one point trying to answer this question for myself! Jet engines use the Brayton cycle, which is a "isobaric" process during combustion, ...
12 votes

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

Single combustor cans are simpler to develop. To get the ignition and combustion process right in an annular combustor is quite a challenge. When the first jet engines were developed, Junkers decided ...
9 votes
Accepted

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

Quick answer: At the design point considered, which is assumed to be takeoff conditions, a CFM56-5C combustor raises gas temperature to 1360°C (the share of the compressor in this raise is about 600 °...
  • 68.3k
8 votes

Can some one please explain to me the purpose of the combustion chamber?

OK, this answer will definitely be trumped by better ones, and Google will serve you better, but until then.... Thrust is basically throwing a mass of stuff in the opposite direction you want to ...
  • 1,262
7 votes
Accepted

What is the difference between single and dual annular combustor?

Here's an engine with old combustor cans: Here's a single annular combustor: And in cross section: And now here's a dual annular combustor (DAC) (pic from here) in cross section: See how it's ...
  • 4,383
6 votes
Accepted

How is the correct air speed for fuel combustion obtained at the inlet of the combustor?

In general, aircraft jet engines have diffuser section(s), that reduce the velocity of the incoming air before it enters the combustion chamber. Sample velocity profile in jet engine; image from ...
  • 99k
6 votes

How is the correct air speed for fuel combustion obtained at the inlet of the combustor?

Combustors usually feature recirculation zones in which the combustion takes place either completely or which at least anchor the flame. This can be done by several designs Sudden jump in cross-...
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6 votes

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

The first operational jet engine contract was awarded to GE/Allison as the J35 and was later upgraded to the J47. When I was at tech school for the J47 we were told GE was given the contract because ...
  • 11.2k
6 votes
Accepted

How is flame stabilisation carried out?

As usual, it is a combination of measures: Flow speed at the start of the combustion chamber is the lowest in the whole engine, in the order of 30 m/s. High fuel pressure and many small fuel injector ...
6 votes

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

Modern jet engines do not use can or cannular combustors. GE made the switch to annular combustors by at least the J85, which had a first engine to test in the 1950s. The TF39 (1964) engine formed the ...
  • 2,599
5 votes

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

I happened upon this question, and thought I could add some information, as I recognized the powerplant right away. This is not another full answer, but only a response to @albin and @PeterKampf as ...
4 votes
Accepted

Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)?

Edit: to honor my original answer, I shall keep it as it is. The question was edited so much I think it would have constituted a whole new question. In it's original form, the Q presented jet engine f/...
  • 23.5k
4 votes

What is the absolute velocity change through compressor+burner?

This image that TomMcW posted in the comments is a much better representation of what is going on. First, looking at axial velocity only is only half of the story, through the compressor and ...
  • 2,599
4 votes
Accepted

What is the absolute velocity change through compressor+burner?

The flow enters the compressor at approximately Mach 0.4 to 0.6 in order to ensure a high mass flow with still subsonic compressor blade speeds. Compressing the air allows to reduce flow speed, and ...
3 votes

How is the correct air speed for fuel combustion obtained at the inlet of the combustor?

How engineers are able to slow air without decompressing it Flow speed is energy, so slowing down the flow will increase its pressure. At subsonic speeds the first part happens already ahead of the ...
3 votes

What materials are used to make up a combustion chamber?

If you are asking about combustor liners specifically (as opposed to the hot section in general), the ones I am familiar with are cobalt-based superalloys.
  • 5,258
3 votes
Accepted

Would a pulsejet/turbine hybrid be efficient?

Some good thinking here but let's start with the basics: Pulse jets require a tuned pipe for adequate compression. The design sends a shockwave back from the exhaust pipe towards the combustion area. ...
2 votes

What materials are used to make up a combustion chamber?

This is more of an engineering question than an aviation question, but since some aviators may be interested in knowing exactly what is in those turbines I will answer. There are three main types of ...
2 votes

What are the differences between single and double annular combustion chambers?

See this answer for the difference between a SAC and DAC combustor. The EASA type certificate for the CFM56-7 also identifies which engines have the DAC and which have the SAC. The answer depends on ...
  • 4,383
2 votes

What is the Fuel-Oxygen ratio for a large turbofan at cruise conditions?

I chose the GE90-115B because it is the largest turbofan in terms of thrust. Unfortunately, it was hard to come by specific fuel consumption figures for cruise conditions, maybe because the -115B is a ...
  • 17.3k
2 votes

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

Extracting heat from the exhaust will cool and compress it, slowing it down and reducing thrust. Recirculating the heat back into or downstream of combustion will raise the temperature at that point ...
  • 6,852
2 votes

Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)?

We have to remember air is only 20% oxygen. When you write the stoichimetric formula for the chemical reaction (using oxygen) on a molar basis, you get the combustion ratio by converting the fuel and ...
2 votes

Would a pulsejet/turbine hybrid be efficient?

Would a pulsejet/turbine hybrid be efficient? Well, how do you define "efficient"? Do you have a specific absolute number in mind? Greater 30% thermal efficiency? Greater than 50% ...
  • 5,258

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