Fans And Dynamic Compressors Flashcards
What is combination flow or multi flow compressors?
Having 2 or more types of impellers in a compressor.
Ex: 5 stages of axial, then going into centrifugal impellers to achieve discharge pressure easier.
What does surge mean?
How is it controlled?
Compressed far rushing from discharge back to inlet.
Controlled by a recycling valve, which directs the gas back to tank. Or a surge valve, which will release the gas to atmosphere.
What does stonewalling mean?
Has has reached speed of sound. It’s maximum velocity. It can’t go faster so it slows down.
What are the 3 types of centrifugal fan blades?
Which is the most efficient?
Solid flat
Forward curved
Air foil, most efficient.
What are 2 types of axial compressor rotors?
Which is the strongest?
Drum
Solid disc, strongest
What are the 3 types of mechanical drafts?
Give examples of each.
Forced draft, fan is forcing air into furnace.
Induced draft, fan is blowing air out of the furnace.
Balanced furnace, blowing air in and sucking air out.
Large single suction fans are generally mounted on what type of bearing?
Double row spherical roller bearings.
What are 3 pressures fans develop?
How are they read?
Static pressure
Velocity pressure
Total pressure
Read by manometer
What is static pressure?
The air pressure on the inside of the duct walls or pipping.
What is velocity pressure?
Is the pressure over and above static pressure.
What happens to velocity and pressure when air is converged?
Velocity increases so pressure also increases.
What does a “hunting” fan mean?
How is hunting made?
Hunting is where the fan sounds like it’s breathing.
Back pressure is system crates the hunting effect.
Where are carbon ring seals?
Where are they located?
Used where there are low pressure differentials.
On shaft between casing and bearing housing.
What are 3 types of thrust control?
Thrust bearings
Balanced drum
Impeller arrangements
Where would you use sectional casing compressors?
Usually on units with low pressure ratios and small volumes.
What are 3 different designs of compressor casings?
Sectional
Horizontally split
Vertically split
What do diaphragms do in a compressor?
Directs discharge gas from one impeller to the eye of the next.
What do inlet guid vanes do?
Control output and efficiency
By throttling inlet gas flow
What are 3 types if impellers used in compressors?
Open
Closed
Semi closed
Single stage compressors deliver what types of air?
Large amounts if air at low pressure.
What applications are vertically split casing used for?
High pressure applications
Up to 10,000 psig
Horizontally split casings are usually limited to how many psi?
Horizontally split casing ms are usually limited to less than 1000 psig.
Dynamic compressors use impellers to impact _____ energy into the gas stream.
Kinetic energy
What are some types of cooling towers?
Atmospheric ( using natural draft)
Mechanical, forced draft and induced draft.
What do some manufactures put in a tube axial fan to reduce swirl?
A channel in discharge to reduce swirling in duct.
What are the 3 main groups for axial flow fans?
1: propeller fans
2: tube axis fans
3: vane axis fans
What application would you use radial fan blades?
High speeds, high pressure
Compare forward blade fans speed and volume to a backward inclined blade fan.
What application is a forward blade used?
Forward blade is slower speed for same amount of volume.
Low operating speeds make then quite limited to clean services, low pressures.
What is used to prevent pitting is a bearing and used to ground a build up of static electricity?
Static arrests
Ex: ground brush touching the shaft.
What is the formula for calculating the curet duct length for laminar flow?
Squat root of 4ab/ pie
A scoop tube is a type of what?
Hydraulic clutch
