Combustion Chambers Questions and Answers

Answer: A

Both are true and the second is why pattern factor matters so much. Reducing the peak excursion above the mean lengthens the life of the whole row, which is worth a great deal of development effort on the dilution jets.

Answer: B

Both statements are true and the second is the reason. Many small holes distribute the same protection using less air than a few large slots, which frees flow for the primary and dilution zones where it is increasingly needed.

Answer: C

Correct answer: 1, 2, 3, 4, 5

The sequence follows the air through the chamber. Compressor delivery air is first slowed in the diffuser, since the flame could not be held at compressor exit velocity. A fifth of it then enters the primary zone through the swirler, where the mixture is near stoichiometric and the recirculation holds the flame. Intermediate air completes the burning, and dilution air finally brings the temperature down to what the turbine will accept.

Answer: D

Only two igniters are usually fitted, so light-around through interconnectors or around the annulus is essential. A failure at that step leaves part of the chamber unlit and produces a badly distorted exit temperature pattern.

Answer: A

Each step traded ease of development for less weight, less length and a better exit temperature pattern. The last was driven by emissions rather than by performance, which is a different motivation from the three before it.

Answer: B

The gas is hottest in the primary zone and is progressively cooled by the air admitted afterwards. That is the whole purpose of the dilution zone, since the primary zone temperature would destroy any turbine blade within seconds.

Answer: C

Correct answer: 1, 2, 3, 4, 5

Each step depends on the one before. The exit traverse is measured on a rig, the hot spots are identified from it, the dilution holes are repositioned or resized to attack them, and the chamber is retested to confirm the pattern factor has improved. Only when it has can the design be released, since turbine life substantiation depends on the pattern being known and controlled.

Answer: D

Correct answer: Only three

The first three describe the three zones correctly. The fourth repeats the dilution zone’s function under the primary zone’s name, which is the reverse of the truth: the primary zone is the hottest part of the chamber, burning near stoichiometric to hold the flame, and it is the dilution zone that brings the temperature down afterwards.

Answer: A

Correct answer: Only three

The first three are right and they follow from temperature. Nitrogen oxides form fastest where the flame is hottest, which is at high power; carbon monoxide and unburnt hydrocarbons are products of incomplete combustion and are worst at idle, where the chamber runs cool. The fourth contradicts the first by placing nitrogen oxides at idle.

Answer: B

Correct answer: Only three

The first three describe the three arrangements correctly. The fourth is wrong and it is the annular chamber’s chief drawback: because there is only one continuous flame tube, a single sector cannot be tested in isolation and the whole annulus must be run, which makes development slower and far more expensive than for a can design.