Compressed Air Systems. References Required Introduction to Naval Engineering (Ch 18). Optional:...
-
Upload
kristian-morrison -
Category
Documents
-
view
220 -
download
1
Transcript of Compressed Air Systems. References Required Introduction to Naval Engineering (Ch 18). Optional:...
References
Required•Introduction to Naval Engineering (Ch 18). Optional:•Principles of Naval Engineering (Ch 3. Pg. 71-74).
Introduction
• Air systems are vital to ship operations– Starting diesel and gas turbine engines– Torpedo ejection– Deballasting air (EMBT Blow)– Prairie masker
• Compressed air represents stored energy - capable of doing work at a later point
• Used extensively both in high pressure and low pressure applications
Air Compressors
• Used to compress air from inlet pressure (atm) to a higher pressure (PV a RT)
• Classified according to:– Type of displacement– Staging– Type of Drive (prime mover)– Operating Pressure– Capacity
Air Compressors• Type of displacement– Positive: used for high pressures
– aka HPACs and LPACs
– Non-positive: used for lower pressures– aka fans and blowers
• Type of drive system– Classified according to prime mover (almost all
electric motors)• Staging– Number of compression steps used in
compression processNumber of Stages Pressure (psig)
One 100-150
Two 150-500
Three 500-2500
Four 2500-5000
Air Compressors• Operating (discharge) pressure– Low (150 psi max)– Medium (151-1000 psi)– High (1001-5000 psi)
• Capacity– Volume of air compressed– CFM (cubic feet per minute)
Positive Displacement
• Reciprocating Piston– Piston assembly
with valves to control flow
– Can either be single stage or multi-stage
– aka HPAC
Positive Displacement
• Rotary Compressor– Rotary sliding vane
(rare)– Rotary impeller (low
press/ high capacity applications)
– Liquid piston (old ships)
Positive Displacement
• Rotary Compressor– Rotary sliding vane
(rare)– Rotary impeller
(low press/ high CFM applications)– aka LPAC
– Liquid piston (old ships)
Positive Displacement
• Rotary Compressor– Rotary sliding vane
(rare)– Rotary impeller
(low press/ high CFM applications)
– Liquid piston (old ships)
Support Systems• Lubrication
– Force-fed compressor-driven system– Prevent metal-on-metal contact to minimize friction/heat– Transfers heat from compression to cooling system
• Cooling– Most cooled by fresh water systems– Remove heat from compression process– Intercoolers used between stages– Aftercooler used after final discharge
• Receivers– Storage tanks for reserve air capacity– Used on ALL compressors to lower pulsations
• Safety features– Auto shutdown
Specific Uses of Air
• High Pressure– Torpedo Ejection– Emergency Blow– Hydraulics– Remotely-operated valves
• Low Pressure– Prairie Masker system – Potable water– Pneumatic tools & valves