Inlets and Diffusers Questions and Answers

Statement I: Internal compression intakes are inherently more robust than external compression ones.

Statement II: They avoid the cowl drag associated with turning the external flow.

In the light of the above statements, choose the correct answer.

Statement I: Ram compression grows more important as flight Mach number rises.

Statement II: The total to static pressure ratio increases steeply with Mach number.

In the light of the above statements, choose the correct answer.

Arrange the flow's passage through an external compression supersonic intake in order:

1. Free stream supersonic flow approaches the ramp

2. Oblique shocks turn and decelerate the flow ahead of the cowl

3. A weak normal shock at the throat completes the transition to subsonic

4. Subsonic diffusion continues in the diverging duct

5. Air reaches the compressor face at a modest axial Mach number

Select the correct sequence.

Arrange these intake types by the flight Mach number at which each becomes appropriate:

1. Subsonic pitot intake with a rounded lip

2. Normal shock intake with a sharp lip

3. External compression intake with fixed ramps

4. Mixed compression intake with variable geometry

Select the correct sequence.

Arrange these events in a supersonic intake unstart:

1. A disturbance raises the back pressure in the duct

2. The terminal shock moves forward towards the throat

3. The shock is expelled ahead of the cowl lip

4. Total pressure recovery collapses and distortion rises

5. The engine surges or flames out

Select the correct sequence.

Arrange these steps of matching an intake to an engine across the envelope:

1. Establish the engine's airflow demand at each flight condition

2. Size the intake capture area for the critical condition

3. Check spillage drag at throttled and off-design conditions

4. Add variable geometry if a fixed intake cannot cover the envelope

5. Verify recovery and distortion limits are met throughout

Select the correct sequence.

Arrange these regions of an intake duct in the order the air passes through them:

1. The cowl lip and capture plane

2. The throat, where the area is smallest

3. The subsonic diffuser section

4. The compressor face

Select the correct sequence.

Consider the following intake type and characteristic pairs:

Subsonic pitot intake - Simple duct with a rounded lip

External compression intake - Oblique shocks ahead of the cowl

Internal compression intake - Shock system entirely within the duct

Mixed compression intake - No shock waves at all

How many of the pairs given above are correctly matched?

Consider the following pairs of phenomenon and cause:

Spillage drag - Capturing less air than the approaching streamtube

Inlet buzz - Unsteady oscillation of the shock system

Unstart - Expulsion of the shock system ahead of the cowl

Spillage drag - Ingesting fuselage boundary layer air

How many of the pairs given above are correctly matched?

Consider the following pairs of quantity and definition:

Total pressure recovery - Compressor face total pressure over free stream total pressure

Capture area ratio - Streamtube area over intake area

Distortion index - A measure of non-uniformity at the compressor face

Total pressure recovery - Static pressure rise over dynamic pressure

How many of the pairs given above are correctly matched?