Other Engineering Fundamentals Flashcards
Who made the engines on Momsen?
General Electric LM2500 Gas Turbine Engines (GTE)
How much power do the GTEs produce?
26,000 HP
What are the four plant configurations?
- Full Power = Four GTE online
- Split Plant = One GTE on each shaft
- Trail Shaft = One GTE on one shaft, idle shaft is windmilling
- Locked shaft = MRG is locked due to a casualty
What does GTM stand for?
Gas Turbine Module
What does a GTM do?
Provides thermal and acoustic protection from the running Gas Turbine Engine for the crew
Specs of the GTM
- Fire resistant for 2000* F for 15 min
- Sits on 32 shock mounts to allow movement between the engine and the ship’s hull
What does MRG stand for?
Main Reduction Gear
What does an MRG do?
Connects the turbines and shafts. Reduces the high RPM’s of the turbines to a working, more efficient speed. Reduces the speed to allow proper RPM at the propellors
What are the six characteristics of an MRG?
- Double input - Two GTMs as prime movers input to MRG
- Double reduction - Reduction occurs over two stages to convert high speed, low torque to low speed, high torque
- Double helical - Gear teeth are machine in a “V” pattern. Reduces noise and axial thrust
- Articulated - The gears inside are connected to the pinion by a quill shaft
- Single output - Each MRG drives a single shaft
- Locked train - Refers to the gearing inside the MRG which is locked together to rotate in only one direction
Characteristics of the ship’s shafts
Port - [168ft] Consists of 1 thrust bearing and 1 line shaft bearing located in shaft alley
STBD - [228ft] Consists of 1 thrust bearing in AUX 2, 1 line shaft bearing in MER 2 and a second line shaft bearing in shaft alley
What are the Thrust Bearings?
Used to absorb the fore and aft thrust of the shaft as the torque is transmitted to the propellor. It is used to protect the gears inside of the MRG
What are the Line Shaft Bearings?
Used to keep the shaft centered and true as it rotates and to support the weight of the shaft
What are the Strut Bearings?
Mounted to the hull outside the skin of the ship. Used to support the weight of the propellor. Lubricated by seawater
What are the Bulkhead Shaft Seals?
Used around the shaft where the shaft penetrates the ship’s bulkhead. Used to keep water from flooding out an adjacent space and keep it contained in the space that is flooding
What are the Stern Tube Shaft Seals?
Located in shaft alley on port and stbd shafts. This seal is important as it prevents the ocean from flooding out shaft alley. In case of a leak, the seal can be inflated using LP air or two CO2 bottles mounted on the bulkhead. Once inflated the shaft cannot be rotated
What are the four kinds of bleed air?
SPAM
Start Air
Prairie Air
Anti-icing
Masker Air
What do each of the kinds of bleed air do?
Start Air - Used to start the GTMs and as an alternate source to start the GTGs
Prairie Air - Used to mask the noise of the propellor blades. Air travels down the shaft and exits through the small holes on the leading edge of each propeller blade creating bubbles in the water
Anti-icing - Used to warm up the intakes of the GTMs and GTGs in cold climates where the intakes may ice up by diverting warm bleed air to the intakes
Masker Air - Three emitter belts run around the hull of the ship in the vicinity of AUX 1, Main 1 and Main 2. Air exits through small holes out of the belts creating bubbles to mask the machinery noise
What does CPP stand for?
Control Pitch Propeller
What is the purpose of the CPP?
Used to vary the angle of attack of the propeller blades, otherwise known as PITCH. PITCH, when measured in feet, is the theoretical distance the ship will move through the water for each revolution of the shaft. Due to the MRG being Locked Train we are not able to go in reverse.
CPP helps us achieve reverse by rotating the propeller pitch to a negative percent resulting in a reverse movement of the ship
Characteristics of the CPP
- Maximum CPP is -61 percent astern to +120 percent ahead
- Normal CPP range is -45 percent (full astern) to +100 percent (full ahead)
- Hand pump - Used for setting emergency ahead pitch and also if the CRP pumps fail
How many blades are in each propeller?
5
Characteristics of the blades
- Counter rotating
- STBD rotates clockwise viewed from the stern
- Nickel-Aluminum-Bronze
- 6200 LBs per blade
What does HOPM stand for?
Hydraulic Oil Power Module [2]
Considered the heart of the CPP system
What two divisions does the HOPM divide oil into?
- Control Oil
2. Power Oil
What do Control Oil and Power Oil do?
Control Oil
- Used to move the auxiliary servo piston located in the oil distribution box
- Regulated to 400 psi
Power Oil
- Used to move the main or hub servo located in the propeller hub assembly
- Normal Pressure: 500-800 psig
- Can get high as 1000 psig
What is the Oil Distribution Box?
Control the position of the blades by positioning the valve rod, which in turn directs high-pressure hydraulic oil in the hub
Where are the Oil Distribution Boxes located?
- Port Shaft- located at the end of the MRG and the bulkhead
- STBD Shaft- Located between 1A and 1B GTM
