Posted by : sanjay swain 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.

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