FUEL SYSTEM

RELATED QUESTIONS:-

1. WHAT ARE THE MAIN COMPONENTS OF FUEL SYSTEM?
2. IN WHICH WAY FUEL IS SEPARATED FROM SEDIMENTS?
3. WHAT IS THE FUNCTION OF FUEL BOOSTER PUMP? WHAT TYPE OF FUEL BOOSTER PUMP DO YOU HAVE? DISCUSS THEIR OPERATION.
4. WHAT PURPOSE DOES THE FUEL-INJECTION PUMP SERVES?
5. WHAT IS THE FUNCTION OF FUEL INJECTOR?
6. DISCUSS THE OPERATION OF FUEL INJECTOR.
7. WHAT IS THE PRINCIPAL MALFUNCTIONS OF THE FUEL EQUIPMENT?
8. TEST AND OVERHAUL OF FUEL INJECTION VALVES.
9. REASONS FOR FUEL VALVE SEIZURE.
10. HOW FUEL INJECTOR IS BEING COOLED COMPARE BETWEEN OLDER ENGINE AND NEWER ENGINE.
11. HOW TO CHANGE THE TIMING OF FUEL INJECTION?
12. OPERATION OF VIT AND SUPER VIT?
13. REQUIREMENTS OF CRANKCASE OIL AND CYLINDER LUBRICATION OIL.
14. DIFFERENT TYPES OF TEST CARRIED OUT ON LUBE OIL?
15. HOW TO UPKEEP THE QUALITY OF LUBE OIL ONBOARD SHIP?
16. CATEGORIZE CRUDE OIL?
17. DEFINE MICROBIAL DEGRADATION OF FUEL OIL.
18. MICROBIAL DEGRADATION OF LUBE OIL , ITS CAUSE AND EFFECT AND THE METHOD OF INDICATION?
19. 
    

VARIOUS TOOLS

OPEN ENDED SPANNER

RING SPANNER

ADJUSTABLE SPANNER

RACHET SPANNER

NUT BOLT ASSEMBLY

SCREW DRIVER

PLIERS

NOSE PLIER

HAMMER

BENCH VICE

HACKSAW

HATCHET

SAW

HAND DRILL

CHISEL

SCRAPPER

DRILL BIT

L  SHAPE RIGHT ANGLE

DRILLING MACHINE

HAND DRILLING MACHINE

HAND VICE

TORQUE SPANNER

ALLEN-KEY

FILLER GAUGE

PIPE WRINCH

VERNIER CALIPER

DIAL GAUGE

SCREW GAUGE

BRIDGE GAUGE

OIL CAN

MEASURING TAPE

WIRE CUTTER

AIR CONDITIONING COPPER PIPE CUTTER

PULLER

AIR BOLLTE

AIR BOTTLE USED ON-BOARD SHIP

• IT IS A LARGE CONTAINER USED TO STORE COMPRESSED AIR.
• IS IS ALSO KNOWN AS AIR RECEIVER AS IT ACTS AS AN AIR RESERVOIR.
• PRESSURE OF COMPRESSED AIR IS AROUND 25-30 BAR.

PURPOSE

1. MAIN PURPOSE IS TO START MAIN ENGINE AND AUXILIARY ENGINE.

2. SUPPLIES CONTROL AIR TO MARINE ENGINES.

3. USED IN VARIOUS PNEUMATICALLY CONTROLLED DEVICES SUCH AS IF QUICK       CLOSING VALVE IS PNEUMATICALLY OPERATED.

4. HYDROPHORE SYSTEM TO SUPPLY WATER AT A CERTAIN PRESSURE USES                 COMPRESSED AIR.

5. SPRING AIR FOR EXHAUST VALVE IS SUPPLIED THROUGH AIR BOTTLE.

6. FOR CLEANING PURPOSES WHICH REQUIRES COMPRESSED AIR SUCH AS                 FILTERS.

SOLAS REQUIREMENTS

• THE CAPACITY OF AIR BOTTLE SHOULD BE SUCH THAT IT IS CAPABLE ENOUGH TO PROVIDE 12 CONSECUTIVE STARTS FOR REVERSIBLE ENGINE AND 6 CONSECUTIVE STARTS FOR NON-REVERSIBLE ENGINES.
• SOLAS PRESCRIBES THAT THERE MUST BE AT LEAST TWO IDENTICAL MAIN AIR BOTTLE AND ONE EMERGENCY BOTTLE ON EVERY VESSEL.

SAFETY DEVICES FITTED ON AIR BOTTLE

1. RELIEF VALVE

2. DRAIN VALVE

3. FUSIBLE PLUG

4. ALARMkps3005@gmail.com

5. PRESSURE GAUGE

SOME OTHER MOUNTINGS ARE

1. MAIN VALVE FOR STARTING AIR TO MAIN ENGINE

2. VALVE FOR AIR START TO AUXILIARY ENGINE

3. INLET VALVE FOR MAIN AIR COMPRESSOR

4. MANHOLE DOOR FOR INSPECTION PURPOSE (ELLIPTICAL SHAPE)

PURPOSE OF ALARM

• AIR BOTTLE LOW PRESSURE ALARM IS FITTED ON THE RECEIVER.
• ACTIVATION OF THIS VALVE IMPLIES THAT THERE IS NOT ENOUGH AIR IN THE BOTTLE.
• SO MAIN ENGINE OR AUXILIARY ENGINE CAN NOT BE STARTED IN THIS CONDITION.

DURING EVERY WATCH

• MUST DRAIN THE AIR BOTTLE.
• KEEP DRAIN VALVE OPENED TILL ALL THE MOISTURE IS DRAINED.
• IF MOISTURE CARRYOVER TAKES PLACE ALONG WITH COMPRESSED AIR , IT WILL CORRODE AIR BOTTLE.
• IN ABSENCE OF DRAINING PROCEDURE OIL CARRYOVER WILL TAKE PLACE AND MAY RESULT IN FIRE.

MATERIAL

MADE UP OF CAST IRON.

INTERNAL SURFACE IS COATED WITH ANTI-CORROSIVE MATERIAL.

DIESEL CYCLE

DIESEL CYCLE (constant pressure cycle)

The cycle was first analysed by Rudolf Diesel

1-2:- isentropic compression

2-3:- heat addition at constant pressure

3:- heat supply is cut-off

3-4: isentropic expansion

4-1:- heat rejection at constant volume

Compression ratio=v1/v2

• It is an ideal cycle. 
• It must be made clear that this does not represent what actually happens inside the cylinder of a working diesel engine. 
• It was developed to be able to model engine behaviour and to analyze the effects of certain changes to the cycle without the complications of modelling an actual engine cycle.

Like an indicator diagram it is a graph of Pressure against Volume, but it makes certain assumptions:

(a) The mass of air within the cylinder remains the same: There are no inlet or exhaust valves.

(b) Fuel is not injected and burnt, but heat energy is added at constant pressure.

(c) At the end of the cycle the heat energy is rejected at constant volume.

(d) The compression and expansion of the air is adiabatic (no heat energy is added or lost) and follows the law (pv^y=c)

where c is a constant , for y air is 1.4.

NOTE:- Thermal efficiency of diesel engine is always less then otto engine for same compression ratio.(mathematically can be shown)

CENTRAL COOLING SYSTEM

•     TO PREVENT PROBLEMS ASSOCIATED WITH SALT WATER SYSTEM  FRESH WATER IS USED FOR COOLING ALL THE COMPONENTS WHICH FORMS A CLOSED SYSTEM.

• ·   SALT WATER PASSES THROUGH ONLY ONE SET OF PUMPS, VALVES, AND FILTER AND A SHORT LENGTH OF PIPING.

• ·    THE SEA WATER TAKES WATER FROM THE SUCTIONS ON EITHER SIDE OF THE MACHINERY SPACE AND AFTER PASSING THROUGH THE COOLER IT IS DISCHARGED STRAIGHT OVERBOARD.

•      THE FRESH WATER IN THE CLOSED SYSTEM IS TREATED WITH CHEMICALS TO PREVENT CORROSION OF THE PIPEWORK AND COOLERS. WITH CORRECT CHEMICAL TREATMENT, CORROSION IS ELIMINATED IN THE FRESH WATER SYSTEM, WITHOUT THE NEED FOR EXPENSIVE MATERIAL.

•       IT CAN BE DIVIDED INTO THREE SECTIONS:-                                                              

                                     1. SEA WATER CIRCUIT                       
                                      2. HIGH TEMPERATURE CIRCUIT         
                                       3. LOW TEMPERATURE CIRCUIT

            COMBINATION OF THESE IS KNOWN AS CENTRALISED COOLING SYSTEM.

• THE OUTLET OF JACKET COOLING WATER IS USED FOR THE EVAPORATION OF SEA WATER (FRESH WATER GENERATOR).
• HIGH TEMPERATURE SYSTEM(HT) IS USED FOR

               - MAIN ENGINE LINER COOLING

                  -CYLINDER HEAD COOLING

                    -EXHAUST VALVE COOLING

• ·        LOW TEMPERATURE(LT) USED FOR:-

§  FUEL VALVE COOLERS

§  AIR CONDITIONING CONDENSER

§  SHAFT BEARINGS

§  HYDRAULIC OIL COOLERS

§  MAIN AIR COMPRESSOR

. MAIN ENGINE AIR COOLER   

. LUBE OIL COOLER

FEATURES OF 4 STROKE MARINE DIESEL ENGINES

•          4 STROKE ENGINES
•          HIGHER OUTPUT
•          HIGHER MEAN EFFECTIVE PRESSURE
•           HIGH DEGREE OF TURBOCHARGING
•           LOW WEIGHT OF ENGINE AND REDUCED SPACE REQUIREMENT

                         - AS A RESULT OF TURBOCHARGER
                      - 30% SAVING IN SPACE
                       -300% SAVING IN WEIGHT 

•          comparison   W.R.T SLOW ENGINES

                                         - LOW HEAD SPACE

                                          - LOCATION OF ENGINE AS AFT AS POSSIBLE.

                                           -ENGINE SPEED AND PROPELLER SHAFT SPEED INDEPENDENT OF EACH OTHER.

                                            -LOW INSTALLATION COST.

•          HIGH LUBRICATING OIL CONSUMPTION.
•          SHORT LIFE OF EXHAUST VALVE

STUFFING BOX

STUFFING BOX

fig.:-stuffing box

FUNCTION

•                   TO PREVENT PISTON ROD TAKING OIL FROM CRANKCASE.
•                  COUNTERACT THE LEAKING OUT OF SCAVENGE AIR

              

LOCATION

•               AT THE BOTTOM OF SCAVENGE AIR BOXES   

               

          

HOW TO CHECK DURING ENGINE RUNNING

•                 BY WATCHING THE OUTLET FROM TEST COCK ON MANOUVERING    PLATFORM.
•                 LEAKAGE OF AIR INDICATES THAT SEALING RINGS ARE DEFECTED.
•                 EXCESSIVE OIL OUTLET MEANS THAT SCRAPPER RING NEED OVERHAUL.

            

CHECK POINTS DURING OVERHAUL

•               CHECK CLEARANCE OF RINGS (VERTICAL, GAP)
•               CHECK SPIRAL SPRING TENSION
•               ALL DRAIN HOLES CLEANED
•               CHECK THE FITTING BOLT. RENEW LOCKING WASHER, RENEW ‘O’ RING.

overhauling of stuffing box

TURBOCHARGER

BY TURBOCHARGING AN ENGINE, THE FOLLOWING ADVANTAGES ARE OBTAINED:

• INCREASED POWER FOR AN ENGINE OF THE SAME SIZE OR REDUCTION IN SIZE FOR AN ENGINE WITH THE SAME POWER OUTPUT.
• REDUCED SPECIFIC FUEL OIL CONSUMPTION - MECHANICAL, THERMAL AND SCAVENGE EFFICIENCIES ARE IMPROVED DUE TO LESS CYLINDERS, GREATER AIR SUPPLY AND USE OF EXHAUST GASSES.
• THERMAL LOADING IS REDUCED DUE TO SHORTER MORE EFFICIENT BURNING PERIOD FOR THE FUEL LEADING TO LESS EXACTING CYLINDER CONDITIONS.

CONSTRUCTION DETAILS:-

• THE TURBOCHARGER CONSISTS OF A SINGLE STAGE IMPULSE TURBINE CONNECTED TO A CENTRIFUGAL IMPELLER VIA A SHAFT.

• THE TURBINE IS DRIVEN BY THE ENGINE EXHAUST GAS, WHICH ENTERS VIA THE GAS INLET CASING. THE GAS EXPANDS THROUGH A NOZZLE RING WHERE THE PRESSURE ENERGY OF THE GAS IS CONVERTED TO KINETIC ENERGY. THIS HIGH VELOCITY GAS IS DIRECTED ONTO THE TURBINE BLADES WHERE IT DRIVES THE TURBINE WHEEL, AND THUS THE COMPRESSOR AT HIGH SPEEDS (10 -15000 RPM). THE EXHAUST GAS THEN PASSES THROUGH THE OUTLET CASING TO THE EXHAUST UPTAKES.

      · ON THE AIR SIDE AIR IS DRAWN IN THROUGH   FILTERS, AND ENTERS THE     COMPRESSOR WHEEL AXIALLY WHERE IT IS ACCELERATED TO HIGH VELOCITY. THE AIR EXITS THE IMPELLER RADIALLY AND PASSES THROUGH A DIFFUSER, WHERE SOME OF THE KINETIC ENERGY GETS CONVERTED TO PRESSURE ENERGY. THE AIR PASSES TO THE VOLUTE CASING WHERE A FURTHER ENERGY CONVERSION TAKES PLACE. THE AIR IS COOLED BEFORE PASSING TO THE ENGINE INLET MANIFOLD OR SCAVENGE AIR RECEIVER.

     ·THE NOZZLE RING IS WHERE THE ENERGY IN THE EXHAUST GAS IS CONVERTED INTO KINETIC ENERGY. IT IS FABRICATED FROM A CREEP RESISTANT CHROMIUM NICKEL ALLOY, HEAT RESISTING MOLY-CHROME NICKEL STEEL OR A NIMONIC ALLOY WHICH WILL WITHSTAND THE HIGH TEMPERATURES AND BE RESISTANT TO CORROSION.

•  LABYRINTH SEALS OR GLANDS ARE FITTED TO THE SHAFT AND CASING TO PREVENT THE LEAKAGE OF EXHAUST GAS INTO THE TURBINE END BEARING, OR TO PREVENT OIL BEING DRAWN INTO THE COMPRESSOR.

      

     

• A LABYRINTH ARRANGEMENT IS ALSO FITTED TO THE BACK OF THE COMPRESSOR IMPELLER TO RESTRICT THE LEAKAGE OF AIR TO THE GAS SIDE

           

• DISCOLORING OF THE OIL ON A ROTOR FITTED WITH A ROLLER BEARING WILL ALSO INDICATE A FAILURE IN THE TURBINE END GLAND.

TURBOCHARGER TYPES

(A) AXIAL FLOW :-

•     SINGLE STAGE IMPULSE REACTION TURBINE IS USED.
•     TURBINE DRIVES A CENTRIFUGAL COMPRESSOR.
•     EXHAUST FLOW IN AND OUT OF TURBINE BLADE IS ALONG THE AXIS OF THE SHAFT.
•     MOST COMMONLY USED IN MARINE APPLICATION

(B) RADIAL FLOW

·         EXHAUST FLOW INTO THE TURBINE BLADE IS ALONG THE RADIAL DIRECTION.
·         OUTLET OF TURBINE IN ALONG THE AXIX OF ROTOR.
·         USED IN SMALL HIGH SPEED ENGINES.  

MATERIALS USED IN T/C

TURBINE WHEEL, NOZZLE RING, ROTOR SHAFT AND BLADES:

·  NICKEL-CHROME ALLOY (NI 75%, CO 18%, TI 3%, AL 2%, CR 2%)

TURBINE CASING:

• CAST IRON WITH CORROSION PREVENTIVE PLASTIC COATINGS IN CASE OF WATER COLED T/C.

COMPRESSOR IMPELLER, VOLUTE CASING, DIFFUSER, & INDUCER:

• ALUMINIUM ALLOY FOR LIGHT WEIGHT AND STRENGTH OR MORE EXPENSIVE TITANIUM 

TURBOCHARGER SURGING

·     WHEN THE DISCHARGE PRESSURE EXCEED THE PRESSURE BUILD UP IN THE DIFFUSER AND IMPELLER.

·     IT PRODUCES A BACK FLOW OF AIR FROM DISCHARGE TO SUCTION.

·     BACK FLOW FROM SCAVENGE AIR MANIFOLD TO THE T/C DIFFUSER.

·     CHARACTERISED BY NOISE AND VIBRATION.

RASONS FOR T/C SURGING

• ·     SCAVENGE SPACE FIRE
• ·         DIRTY NOZZLE AND BLADE
• ·         INDIVIDUAL CYLINDER MISFIRE
• ·         CHOCKED SCAVENGE/EXHAUST PORT
• ·         INCORRECT MATCHING OF T/C TO ENGINE
• ·         POOR SCAVENGING OR LEAKY EXHAUST VALVE
• ·         SUDDEN LOAD CHANGE BY BAD WEATHER
• ·         POOR POWER BALANCE

SURGING REMEDY AND ACTION

• REDUCE ENGINE SPEED

              -IT WILL REDUCE SCAVENGE AIR PRESSURE

              -HENCE LESS TENDENCY OF REVERSE FLOW

SCAVENGING AND ITS TYPES

                            SCAVENGING

·     IT IS A PROCESS OF REMOVING EXHAUST GAS IN THE ENGINE CYLINDER BY MEANS OF INCOMING CHARGE AIR.

·     AS A RESULT CYLINDER IS FILLED WITH FRESH PRESSURIZED AIR FOR NEXT COMPRESSION STROKE.    

·     THE PASSAGE OF SCAVENGE AIR WILL ALSO ASSIST COOLING OF THE CYLINDER, PISTON AND VALVES.

·     TIME AVAILABLE FOR SCAVENGING PROCESS IN 2 STROKE ENGINE IS LESS THAN 4 STROKE ENGINES.

SATISFACTORY SCAVENGING DEPENDS ON-

•   EFFICIENT EVACUATION OF EXHAUST GASES
•   EXHAUST PORTS OR VALVES OPEN BEFORE SCAVENGE PORTS
•   SCAVENGE PORTS CLOSE AFTER THE PROCESS OF GAS EXCHANGE
•    LOSS OF FRESH AIR THROUGH EXHAUST PASSAGE TO BE MINIMUM

IMPORTANCE OF SCAVENGING

SCAVENGING AFFECTS –

•         OVERALL EFFICIENCY
•         POWER OUTPUT PER UNIT WEIGHT
•         FUEL CONSUMPTION PER UNIT POWER
•         INCOMPLETE SCAVENGING RESULTS IN POOR COMBUSTION
•         LUBRICATING OIL CONTAMINATION
•         WEAR PISTON RINGS AND LINER
•         MEAN TEMPERATURE OF CYLINDER HIGH         

           TYPES OF SCAVENGING

1.          CROSS SCAVENGING
2.          LOOP SCAVENGING
3.          UNIFLOW SCAVENGING

        UNIFLOW SCAVENGING

      

1.       THE AIR INLET AND EXHAUST FLOW IN THE SAME DIRECTION.
2. ·      IT IS THE BEST SCAVENGING PROCESS BECAUSE OF HIGH SCAVENGING           EFFICIENCY (MORE THEN .9)
3. ·      INTERMIXING IS MINIMUM BECAUSE THERE IS NO DIRECTION CHANGE    IN THE FLOW (INLET AND OUTLET).

ADVANTAGES

• HIGHEST SCAVENGE EFFICIENCY AT ALL SCAVENGE RATIOS
• DROP IN SCAVENGE EFFICIENCY LOWEST WITH HIGH SCAVENGE PRESSURE
• MOST SUITABLE FOR PRESSURE CHARGING
• GREATER AREA FOR AIR AND GAS FLOW
• POSSIBILITY OF SHORT CIRCUITING AND MIXING LESS

DISADVANTAGES

• COMPLICATED CYLINDER HEAD AND INCREASED MAINTENANCE                                       

LOOP SCAVENGING

• LOOP SCAVENGING IS THE GAS EXCHANGE PROCESS IN WHICH THE CHARGE AIR PASSES OVER THE PISTON CROWN AND RISES TO FORM A LOOP WITHIN THE CYLINDER, EXPELLING EXHAUST GASES THROUGH EXHAUST PORTS CUT IN THE SAME SIDE OF THE LINER ABOVE THE SCAVENGE PORTS. 

MAJOR REQUIREMENT FOR THE LOOP SYSTEM

• THE INLET AIR PORTS ARE ANGLED TO GIVE ROTARY SWIRLING EFFECT TO THE  INCOMING AIR.
• IT ALSO REQUIRE LONG PISTON SKIRT OR EXHAUST TIMING V/V TO PREVENT  SCAVENGING AIR LEAK INTO EXHAUST WHILE THE PISTON IS AT TOP OF IT’S  STROKE.

ADVANTAGES

• SIMPLICITY, RELIABILITY AND CYLINDER COVER IS SIMPLIFIED.

DISADVANTAGES

• TEMPERATURE GRADIENT EXHAUST TO SCAVENGE PORTS IS HIGH
• EXHAUST BACK PRESSURE HIGHER WITH DEPOSITS
• POSSIBILITY OF INTERMIXING AIR AND GASES
• PISTON AND LINER DISTORTION AND UNEVEN PISTON RING WEAR DUE TO PORTS
• SCAVENGE EFFICIENCY IS LOWER THAN UNIFLOW SCAVENGE EFFICIENCY AT ALL SCAVENGE RATIOS

CROSS SCAVENGING

·       1.  CROSS FLOW SCAVENGING IS THE GAS EXCHANGE PROCESS IN WHICH THE    2. CHARGE AIR PASSES IS DIRECTED UPWARDS, PASSING UNDER THE CYLINDER    3. COVER AND DOWN THE OPPOSITE SIDE, EXPELLING EXHAUST GAS THROUGH  4.  EXHAUST PORTS ON THAT SIDE.
        THIS SYSTEM IS OBSOLETE NOW.