Dynamic Compressors And fans Flashcards
Sectional casings of a dynamic compressor are used for what pressures?
Low pressures
Horizontally split casings of a dynamic compressor are used for what pressures?
Under 1000 psi
Vertically split casings of a dynamic compressor are used for what pressures?
High pressure applications
Which centrifugal fan impeller is the most efficient?
The air foil blade
Which centrifugal fan wheel discharges air at the highest velocity
Forward curved blade
Describe a perfect vacuum in PSIA
0 psia
Describe a perfect vacuum in psig
-14.7 psig
Describe a perfect vacuum in Inches HG
29.92 in/hg
Using a manometer how would you measure static pressure?
One end would be at a right angle to the duct wall and the other end would be open to atmospheric pressure
Using a manometer how would you measure velocity pressure?
One end would be at a right angle to the duct wall and the other end would be open facing the airflow within the duct.
How would you measure total pressure using a manometer?
One end would be open facing the airflow within the duct and the other end would be open to atmospheric pressure.
Total pressure= Velocity pressure+Static pressure.
Large single suction fans are usually mounted on what kind of bearings?
Double row spherical roller bearings
What kind of fan has blades shaped like aircraft or boat propellers?
Axial flow fans
Where would you mount a fan for induced draft?
Between the boiler and the chimney
How is natural draft accomplished?
By a differential pressure between the top and bottom of the cooling tower.
What kind of fan blade would be used if there where high speeds that require a stronger wheel structure?
Radial blade fan
What is the purpose of a fan casing?
It is to collect the air leaving the impeller wheel and change the velocity pressure into static pressure
What kind of axial fan requires fixed guide vanes?
Vane axial fans (tube axial fan)
What are the 2 types of mechanical draft?
Forced draft
Induced draft
What are static arrests on a fan duct system?
They ground the static electricity generated while the fan is running
What is the name of the circular collection chamber mounted around the fan wheel of a centrifugal fan?
It is called a scroll
How can control of air through fans be accomplished?
Inlet louvre, outlet dampers, varying the fan speed.
Surge point of a dynamic compressor happens when?
There is high pressure and low flow
Stone wall point or choke happens in a dynamic compressor when?
There is low pressure and maximum flow
In an axial flow compressor what blade part is mounted directly to the housing and does not spin?
The stators
What part of an axial compressor increases gas pressure? And what part increases velocity?
The rotor blades (rotating part) increase the gas velocity, which then converts into pressure as it enters the stator section and slows down.
