Book 2 - Compressor Stall and Surge

Question 1

it is the ____ flow of air through the engine, and the ___________ of that mass flow, that gives thrust or power

Answer 1

it is the MASS flow of air through the engine, and the ACCELERATION of that mass flow, that gives thrust or power

Question 2

the compressor acts as a ____ to drive air through the engine and to compress it before ______ is added

Answer 2

the compressor acts as a PUMP to drive air through the engine and to compress it before ENERGY is added

Question 3

if an engine takes in a mass flow of 10lb of air per second at the front, then there must be 10lb of air per second emerging at the back. however, the 10lb coming out of the back is going to be of a much greater ______, which means the ________ must be greater

Answer 3

if an engine takes in a mass flow of 10lb of air per second at the front, then there must be 10lb of air per second emerging at the back. however, the 10lb coming out of the back is going to be of a much greater VOLUME, which means the VELOCITY must be greater

Question 4

the relationship between the RPM of the compressor and the mass flow is called the _________ line

Answer 4

the relationship between the RPM of the compressor and the mass flow is called the WORKING line

Question 5

rotors and stators are aerofoils. air flow must pass over them at the correct _____. if not, airflow becomes turbulent and _______ occurs. the angle the air strikes the blades is dependent upon the _________ speed and rate of ______ flow. therefore, an axial flow compressor can only be designed to have these correct flows at one particular ___ and ____ flow

Answer 5

rotors and stators are aerofoils. air flow must pass over them at the correct ANGLE. if not, airflow becomes turbulent and STALLING occurs. the angle the air strikes the blades is dependent upon the ROTATIONAL speed and rate of LINEAR flow. therefore, an axial flow compressor can only be designed to have these correct flows at one particular RPM and MASS flow

Question 6

working line represents the _______ parameters. there is then a _______ margin, and then the ________ area

Answer 6

working line represents the MINIMUM parameters. there is then a SAFETY margin, and then the UNSTABLE area

Question 7

a compressor stall can be recognised by the following:

• ________
• _______ noise
• inability of the engine to _________
• rapid rise in exhaust gas __________

Answer 7

a compressor stall can be recognised by the following:

• VIBRATION
• RUMBLING noise
• inability of the engine to ACCELERATE
• rapid rise in exhaust gas TEMPERATURE

Question 8

once all the stages in a compressor have stalled, they will be doing no ____ on he air. the high pressure air at the ____ of the compressor will travel to the ___ pressure at the front. it will do this rapidly, almost _________. this can be recognised by a loud ____ in the intake

Answer 8

once all the stages in a compressor have stalled, they will be doing no WORK on he air. the high pressure air at the BACK of the compressor will travel to the LOW pressure at the front. it will do this rapidly, almost EXPLOSIVELY. this can be recognised by a loud BANG in the intake