Combustion Chambers Questions and Answers

Answer: C

Correct answer: 8

A rise of 120 K is three intervals of 40 K, and each doubles the output, so \[ 2^3 = 8. \] The exponential dependence is why nitrogen oxide emission is so sensitive to peak flame temperature, and why every low-emission combustor design - lean premixed, staged, rich-quench-lean - works by holding that temperature down.

Answer: D

Correct answer: 5

\[ \frac{25}{5} = 5. \] The range matters because combustion behaviour changes with pressure: at the low pressure of high altitude idle the reaction rates fall, the fuel atomises less well and the weak extinction limit narrows, which is precisely why altitude relight is the demanding case rather than take-off.

Answer: A

Multiplying gives \( 8 \times 3 = 24 \) per cent of the total flow devoted to wall cooling. As turbine entry temperatures rise this share must fall, which is exactly why effusion cooling has displaced simple film slots.

Answer: B

Both quantities have risen by the same factor of four, so the ratio is unchanged at 50 to 1. Real engines do not hold it constant, and the way it varies across the range is what makes idle and take-off such different combustion problems.

Answer: C

Both statements are true and the second is the reason. Admitting all the air at the injector would give an equivalence ratio near 0.25, at which no flame could survive, so the primary zone receives only the share that makes it stoichiometric.

Answer: D

Both hold and the second explains the opposition. No single operating condition minimises every regulated emission, which is exactly why staged and lean premixed combustors exist to change the trade rather than merely to optimise within it.

Answer: A

Correct answer: Both Statement I and Statement II are correct

Both are true and the second explains why the first is worth its cost. The swirler sets up a toroidal recirculation in the primary zone that continuously carries hot combustion products back upstream to meet the incoming fuel and air, so the flame is reignited continuously rather than being blown downstream. Without it no flame would be held at combustor velocities.

Answer: B

Both statements are true and the second is the reason. Where almost all the fuel is burned the figure discriminates between nothing, so pressure loss and emissions become the parameters that actually separate good chambers from poor ones.

Answer: C

The first is correct and the second reverses the truth. Development requires testing the whole annulus, which is expensive compared with rigging a single can, and that ease of development is precisely what kept can and cannular chambers in use for so long.

Answer: D

Correct answer: Both Statement I and Statement II are correct

Both are true and the second gives the mechanism. Cutting the fuel faster than the airflow can fall leaves the primary zone too lean to sustain combustion, and once the flame is out the engine must be relit. This is why the fuel control schedules a minimum flow during deceleration, exactly as it schedules a maximum during acceleration.