Post on 23-Feb-2017
Roger C. Montepio
WELCOME
AGRICULTURAL MACHINERY
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Roger C. Montepio
LECTURE TOPICS
What is a diesel engine? (comparison between gasoline engine and a diesel engine)
Parts, principles and uses of diesel engineServicing and maintenance of a diesel engineFuel Injector
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Engine Dissection
You are dissecting a 3.5 HP single cylinder, 4 cycle engine, made by Briggs & Stratton in Milwaukee, WI
These engines are typically used in lawn mowers, snow blowers, go-carts, etc
(ref. 2, Used by permission of Briggs and Statton, ©1992, all rights reserved)
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• Engine Terminology• Engine Classifications
- a device which transforms the chemical energy of fuel into thermal energy and uses this energy to produce mechanical work.
What is engine?
ENGINE
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Cylinder volume, V
Clearance volume, Vc
Stroke volume, VS
Top dead center, TDC
Bottom dead center, BDCConnecting rod
Crank
Check
Crank case
Cylinder
Crank pin
Gudgeon or wrist pin
Piston
Suction valve Exhaust valve
Intake of suction manifold
Cylinder head
Exhaust manifold
Crank shaft
ENGINE
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Engine-Review
Convert fuel chemical energy into mechanical powerCombustion of the fuel causes one or more reciprocating pistons, to turn a crankshaft
Transmission of power:Crankshaft via flywheel
Connecting rod
Piston Output shaft
Desired load
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Crank Shaft Connecting Rod & Piston
Engine-Review
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Spark vs. Compression Ignition
• Spark ignition (SI) engines– a compressed, homogeneous air-fuel mixture (15:1
ratio of air to fuel by mass) is ignited using a spark• Compression ignition (CI) engines
– rapid compression of air to a high pressure raises the temperature so that fuel, when delivered into combustion chamber, spontaneously ignites without need for a spark
– often referred to as a Diesel engine
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Description SI Engine CI Engine1 Basic cycle Based or Otto cycle. Based on Diesiel cycle.
2 FuelPetrol (gasoline). Hight self-ingintion temperature desirable
Diesel oil. Low self-ignition temperature desirable
3 Introduction of fuel
Fuel and air introduced as agaseous mixture in thesuction stroke. Carburator nessesary to provide themixture. Throtle controls thequantity of mixtureintroduced.
Fuel is injected directly intocombustion chamber at highpressure at of compressionstroke. Carburator is eliminatedbut a fuel pump and injectornecessary. Quality of fuelregulated in pump.
4 IgnitionRequired an ignition system with spark plug in the combustion chamber.
Ignition due to high temperatur, caused by high compression of air, when fuel is injected. Ignition system and spark plug is eleminated.
5Compression ratio rage
6 to 10.5. Upper limit of CR fixed by anti-knock quality of fuel.
14 to 22. Upper limit of CR is limited by the rapidly increasing weight of the engine structure as the compression ratio is further increased.
6 SpeedHigher maximum revolution per minute due to lighter weight.
Maximum r.p.m lower
7 Efficiency Maximum efficiency lower Higher maximum efficiency.
8 Weight Lightrer Heavier due to higher pressures
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DIESEL ENGINE
- a type of internal combustion engine, more specifically, a compression ignition engine, in which the fuel is ignited by the high temperature of compressed gas, rather than a separate source of energy(such as a spark plug).
What is a diesel engine?
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DIESEL ENGINE
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DIESEL ENGINE
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How it works?
When gas is compressed its temperature rises. A diesel engine exploits this property in order to ignite the fuel. Air is drawn into the cylinder of a diesel engine, and compressed by the rising piston. This happens at a much higher compression rate than in a spark-ignition engine. At the top of the piston stroke diesel fuel is injected into the combustion chamber at high pressure through an atomising nozzle. It mixes with the hot, pressurised air. The resulting mixture ignites and burns very rapidly. This contained explosion causes the gas in the chamber to expand, driving the piston down with considerable force, and creating power in a vertical direction.
The connecting rod transmits this motion to the crankshaft which is forced to turn, delivering rotary power at the output end of the crankshaft. ‘Scavenging’ - pushing the exhausted gas-charge out of the cylinder and drawing in a fresh draught of air - is done through ports or valves.
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Working Principles
Suction StrokeCompression Stroke,Power Stroke,Exhaust Stroke
Diesel working principles
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Fuel Characteristics
Diesel Fuel Diesel fuel is a product of crude oil, although other oils can be burned inside
an adapted engine. Good quality diesel fuel can be synthesized from vegetable fat and alcohol.
Diesel engines can work on thicker, heavier oil, or oil with higher viscosity, as long as it is heated in order to ease pumping and injection. These fuels are cheaper but dirtier than clean, refined diesel oil.
Diesel fuel is more difficult to ignite than gasoline because of its higher flash point, but once burning, a diesel fire can be extremely fierce.The use of low-grade fuels can lead to serious maintenance problems.
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Supporting Systems
Intake and Exhaust SystemStarting SystemFuel System,Cooling System,Lubricating System
Diesel Supporting Systems
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Intake System
The function of this system is to allow the purified air to the cylinder
Air Cleaner,Intake Manifold,Intake Valve,Supercharger, etc.
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Intake System
1. Wing nut2. Washer3. Air Filter cover4. Rubber Packing5. Air Filter cartridge6. Rubber packing7. Air Filter body8. Rubber packing9. Air Filter flange10. Air Filter leeve11. Intake pipe
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Faults and Remedies
Faults and remedies1) Air cleaner jammed with dirt -Change 2) Internal manifold cracked -Change 3) Cage --- and bent stem of intake valve -Repair or change 4) Super charger not working properly -Repair or change
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Exhaust System
The function of this system is to take out burnt gas from the cylinder
Silencer pipe,Silencer box andTail pipe,
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Faults and Remedies
Faults and remedies1) Exhaust manifold broken/cracked -Change2) Silencer pipe cracked -Repair or change3) Silencer box jammed due to burnt or leaked carbon -Repair or change4) Tail pipe leaked or cracked -Repair or change
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Starting System
The system starts the engine by providing initial rotations via:
Hand-starting system,Self-starting system,Rope-starting system andPedal-starting system
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Starting System
Hand-starting system is generally used in one cylinder diesel engine.There is no fault in this system, one handle is used for starting.( Water,lubricant and fuel must be checked before starting)
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Fuel System
Engine fuel system is very important through which the fuel is taken out of the fuel tank for combustion.
Fuel tank,Fuel line,Fuel filter,Low pressure feed pump,High pressure fuel pump andInjector or atomizer
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Faults and Remedies
Faults and remedies1) Fuel tank leaked/cracked -Repair or change2) Fuel line leaked/cracked -Change3) Filter jammed due to dirt -Change4) Low pressure/feed pump faulty -Repair or change after checking5) High pressure fuel pump faulty -Repair or change after checking6) Injector faulty -Repair or change after checking
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Cooling System
Engine cooling system enables the engine to maintain a constant operating temperature.
Water cooling system andAir cooling system
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Cooling System
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Lubricating System
Using lubricant, the lubrication system prevents wear and tear of moving components and enables components to move faster and more efficiently.
Three functions (Cooling, Sealing and Cleaning)Strainer,Oil pump,Oil filter,Oil pressure gaugeOil passage
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Faults and Remedies
Faults and remedies1) Strainer may be damaged -Change2) Pump may not work -Repair or change3) Oil filter jammed due to dirt -Change4) Oil pressure gauge faulty -Repair or change (after checking)5) Oil passage jammed -Clean
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Engine Faults
Five common faults are faced during engine operation :1. Over-heating2. Excessive engine vibrations3. Excessive fuel consumption4. Excessive lubrication consumption5. Excessive noise during operation
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Engine Faults
Possible reasons for over-heating of engine :1. Low water quantity in radiator or water tank2. Ignition starts after specified time3.Fan belt lose or torn4. Water jacket jammed5. Faulty water pump6.Low quantity of lubricating oil7. Faulty lube oil pump8. Broken fan blade9.Engine operates over load10. Engine operates at a high speed for a long time
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Engine Faults
Possible reasons for engine vibration :1. Vibration damper or engine counter-weight are not working2. Detonation and auto-ignition3. Main engine bearing, the smaller end bearing of connecting rod, or the thrust bearing, have become loose.
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Engine Faults
Possible reasons for excessive fuel consumption :1. Frequent starting and stopping uses a lot of fuel2. Leak in fuel delivery line3. Leak in fuel tank4. Air cleaner jammed5. Engine left in operation unneccessarily6. Improper valve timing7. Over loaded engine
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Engine Faults
Possible reasons of excessive lubrication consumption :1. Piston wrongly fitted 2. Piston and connecting rod misaligned3. Oil ring not placed exactly in oil ring grove4. Too large a gap between piston and cylinder5. Low tension of oil ring6. Excessive wear of big-end bearing7. Main oil seal cracked or damaged8. Intake valve guide wrongly fitted9. Excessive wear of cylinder taper and out / round10. Engine head gasket cracked and damaged
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Engine Faults
Possible reasons for excessive noise during operation :1. Wear and improper adjustment of engine parts2. Abnormal condition due to detonation and auto-ignition3. Poor quality fuel4. Loose connecting rod
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Engine Faults
Wearable and breakable parts of a fuel pump :• Wear of plunger• Wear of plunger bush• Plunger retaining spring can lose tension• Plunger-retaining spring can break• Wear of bush and ball bearing• Wear above tappet and bottom of plunger• Wear of roller and fan
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Others
COMPLAINT POSSIBLE CAUSE REMEDYEngine Lacks Power * Incorrect grade of oil * Use recommended type and
SAE number of oil* Wrong type of fuel * Change* Insufficient air * Clean or change element* Engine overcooled * Use radiator cover, replace
parts* Valve clearance incorrect * Readjust* Injection pump defective * Readjust or replace* Injection nozzles defective * Readjust or replace* Injection timing incorrect * Readjust* Compression pressure low * Disassemble and replace
parts
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Others
COMPLAINT POSSIBLE CAUSE REMEDYWhite or blue exhaust smoke * Too much oil in crankcase * Fill only to correct level on
gauge* Oil viscosity too low * Refill with correct viscosity
of oil* Engine overcooled * Use radiator cover, or
clean, test and replace thermostat
* Injection timing incorrect * readjust* Compression pressure low * Diassemble and replace
parts* Poor fuel spray from injection nozzles
* Readjust or replace
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Others
COMPLAINT POSSIBLE CAUSE REMEDYBlack or gray exhaust * Wrong type of fuel * Refill with correct type of
fuel* Valve clearance incorrect * Readjust* Injection pump defective * Readjust or replace* Compression pressure low * Disassemble and replace
parts* Insufficient air * Clean or change element
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Others
COMPLAINT POSSIBLE CAUSES REMEDYHigh fuel consumption * Injection pump defective * Readjust or replace
* Injection nozzles defective * Readjust or replace* Wrong type of fuel * Refill with correct type of
fuel* Compression pressure low * Disassemble and replace
parts* Insufficient air * Clean or change air
cleaner element. Check turbocharger
* Injection timing incorrect * readjust
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Others
COMPLAINT POSSIBLE CAUSES REMEDYHigh oil consumption * Too high oil level in
crankcase* Maintain oil level in operating range on gauge
* Incorrect grade of oil * Use recommended type and SAE number of oil
* Oil leaks * Retighten or replace
* Cylinders and piston rings worn
* Disassemble and replace parts
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Others
COMPLAIN POSSIBLE CAUSE REMEDYEngine overheats * Fan belt house * readjust
* Lack of coolant * refill* Too low oil level * Maintain oil level in
operating range on gauge* Water pump defective * Replace* Thermostat defective * Replace
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Others
COMPLAINT POSSIBLE CAUSE REMEDYLow oil pressure * Lack of oil * Refill up to level
* Oil viscosity too low * Refill with correct viscosity of oil
* Oil filter clogged * Replace element* Oil pump defective * Readjust or replace* Oil pressure regulating valve defective
* Readjust or replace
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Nozzle Servicing
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Nozzle Servicing
• Open faulty nozzle and clean away soot (carbon); then check whether nozzlemoves freely.• Check delicate parts.• Check nozzle valve and body.• Immerse nozzle valve and body in clear diesel oil in order to remove carbon.• Use copper wire brush - not a steel brush – to clean off soot (carbon).• Fuel bore should be cleaned with a fine drill.
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Air Bleeding
The correct method of air bleeding the fuel system :• Fill up the fuel tank with new diesel oil.• Open valve of the tank.• Loosen bleeding plug of the fuel filter and pump till fuel flow is continuous.• Tighten the plug.• Loosen injection line nut and crank the engine till fuel is flowing without foam.• Close the injection line and check for leaks.