Saturday, August 10, 2013
THE ELEMENTS INVOLVED IN
THE CONTROL OF DIESEL PROPULSION ENGINES:
1. THE
REVERSING MECHANISM
2. THE
STARTING MECHANISM
3. THE
GOVERNOR SPEED SETTING AND OR FUEL PUMP CONTROL RODS.
· CAPABLE
OF BEING RUN AT SPEEDS BETWEEN IDLING AND FULL SPEED BY APPROPRIATE ADJUSTMENT
OF THE FUEL INPUT.
· CAPABLE
OF BEING EASILY STOPPED AND STARTED IN EITHER DIRECTION OF ROTATION.
· IN
ORDER TO VARY THE POWER OF THE ENGINE IT IS NECESSARY TO CONTROL ONLY THE FUEL INPUT. THIS MAY BE DONE DIRECTLY BY MANIPULATION OF THE FUEL PUMP CONTROL RODS,
OR MORE COMMONLY INDIRECTLY, BY VARYING THE SPEED SETTING OF A GOVERNOR WHICH
IN TURN CONTROLS THE FUEL PUMPS TO MAINTAIN THE REQUIRED SPEED.
· THE
SEQUENCE IN WHICH STARTING AIR IS ADMITTED TO THE CYLINDERS DETERMINES THE
DIRECTION IN WHICH THE ENGINE ROTATES AND IS CONTROLLED BY DISTRIBUTORS, ONE
FOR AHEAD ROTATION AND ANOTHER FOR ASTERN ROTATION.
· THE
APPROPRIATE SEQUENCE AND PHASING OF FUEL PUMP CAMS , VALVE GEAR, ETC., WHICH IS
NORMALLY ACHIEVED BY ROTATING THE CAMSHAFT RELATIVE TO THE CRANKSHAFT ON A TWO
STROKE ENGINE AND IN CASE OF FOUR STROKE ENGINES, BY SLIDING THE CAMSHAFT
AXIALLY RELATIVE TO THE VALVE AND FUEL PUMP MECHANISM.
CHOICE
OF OPERATING MEDIUM
1. COMPRESSED
AIR
2. HYDRAULIC
OIL
3. ELECTRICS
THE
APPLICATION OF AUTOMATION TO DIESEL ENGINE PROPULSION SYSTEMS
IT
SHOULD MAKE SOME CONTRIBUTION IN THE FOLLOWING DIRECTIONS:
1. IMPROVEMENT
IN PLANT OPERATION
2. INCREASE
IN SAFETY BY REDUCING THE POSSIBILITY HUMAN ERROR OR NEGLIGENCE
3. REDUCTION
IN THE NUMBER OF TEDIOUS AND SOMETIMES UNPLEASANT, TASKS REQUIRED TO BE DONE BY
THE ENGINEER
4. ELIMINATION
OF TIME SPENT WASTEFULLY
5. BETTER
UTILIZATION OF THE ENGINEER’S SKILL AND TRAINING.
REMOTE
AND AUTOMATIC CONTROLS FOR MANOEUVRING PROPULSION MACHINERY
THE
CONTROL SYSTEMS FOR MOST TYPE OF ENGINES AND ENGINE INSTALLATION CAN BE DIVIDED
INTO SEVERAL SECTIONS. IT
IS USUALLY POSSIBLE TO DISTINGUISHED THE COMPONENTS ASSOCIATED WITH THE
FOLLOWING FOUR FUNCTIONS:
1. CHANGE
OF MODE OF CONTROL
· MANUAL
CONTROL
· CONTROL
BY THE AUTOMATIC SYSTEM FROM THE BRIDGE
· CONTROL
BY THE AUTOMATIC SYSTEM FROM THE ENGINE ROOM.
2. OPERATION
OF REVERSING MECHANISM
· INTERLOCKS,
TO ENSURE THAT EVENTS OCCUR IN THE CORRECT AND SAFE ORDER,
· REVERSING
MUST NOT BE INITIATED WITHOUT STOPPING THE ENGINE FIRST OR CONVERSELY IF
REVERSING IS INITIATED WHILE THE ENGINE IS RUNNING THE FUEL SUPPLY MUST BE
CUTOFF UNTIL AND HELD OFF UNTIL THE REVERSING SEQUENCE IS COMPLETED.
· INITIATION
OF THE REVERSING SEQUENCE WHILE THE ENGINE IS RUNNING WILL CAUSE THE FUEL TO BE
CUT OFF AND PERHAPS SOME BRAKING DEVICE TO COME INTO ACTION, BUT WILL DELAY THE
START OF THE REVERSING SEQUENCE EITHER FOR A PRESET TIME OR, MORE USUALLY,
UNTIL THE ENGINE SPEED FALLS TO A PREDETERMINED VALUE.
3. OPERATION
OF STARTING MECHANISM, INCLUDING FUEL CONTROL DURING STARTING
· THE OPERATION OF STARTING A DIRECT
REVERSING ENGINE CONSISTS ESSENTIALLY OF APPLYING STARTING AIR, AFTER SETTING
THE REVERSING GEAR IN THE APPROPRIATE DIRECTION, AND MAINTAINING THE SUPPLY
LONG ENOUGH TO ACCELERATE THE ENGINE UP TO A SPEED AT WHICH IT WILL FIRE ON
FUEL.
· IN MOST CASES A PRE-SET AND CONSTANT RATE
OF FUEL ADMISSION IS ALLOWED DURING THE STARTING SEQUENCE.
· IN CASE OF FAILURE REPEATED START (3–4)
AFTER THAT MANUAL INTERVENTION IS NECESSARY.
4. CONTROL
OF ENGINE SPEED DURING RUNNING.
· MOST MODERN ENGINES ARE FITTED WITH
VARIABLE SPEED GOVERNOR WHICH, FOR A GIVEN SPEED SETTING, MAINTAIN CONSTANT
ENGINE REVOLUTIONS BY VARYING THE FUEL ADMISSION AS REQUIRED.
