01 Introduction to Recip Engine (Ignition)

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RECIP. ENGINE OVERHAUL

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TYPES OF ENGINE1. INTERNAL COMBUSTION ENGINE

- combustionoccurs inside the engines (cylinders)

e.g; piston engine, turbineengine, rotary engine and

stirling engine

2. EXTERNAL COMBUSTION ENGINE.

- combustion occurs outside the engine

e.g: old locomotivesand ships to run the propeller.

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GENERAL DESIGN AND CONSTRUCTION

Internal combustion engine or heat engine, convert heat

energy to mechanical energy to drive a propeller from theexpansion of gas (as result of combustion of fuel and air).

Reciprocating engines derive their name from the back-and-forth, or reciprocating movement of their pistons.

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TYPE OF RECIPROCATING ENGINE

1. CLASSIFICATION

a. Cylinder arrangement with respect to the crankshaft

b. Method of cooling (liquid cooled or air cooled)

a. Cylinder arrangement

1. Radial engines.

2. In-line engines.

3. V-type engines.

4. Opposed type engines.

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1. RADIAL ENGINE.

a. Rotary type

b. Static type

1a. Rotarytype radial engine- Cylinder mounted around the crankcase

- Cylinder and propeller rotate together and crankshaft

stationary.

- Most popular rotating engine was the Bently,

GnomeandLeRhone

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1a. Disadvantage of the rotary radial engine

- The torqueeffect produced by the large rotating mass of

the propeller and cylinders made aircraft difficult to control.- Coupled with carburetor, lubrication and exhaust

problem.

- Large frontal area

- Have some cooling problem

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1b. Static type radial engine.

- Engine is stationary and bolted to the airframe.

- Crankshaft rotates and turns the propeller.

- No. of cylinders from 3 to 28 cylinders.

- Consist of a singlerow and multiplerows, max of 4rows with 7 cylinders in a row. And total of 28 cylinders.

- Produce higher horsepower and high power to weight

ratio, mostly used on military and civilian transport

aircraft.

- Most radial engine is a single row and has an odd numberof the cylinder and connected to the single crankshaft.

- In multiple row radial engine, cylinder is staggeredbehind

the space between the frontal cylinders to increase the

amount airflow past each cylinder for cooling

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2. IN-LINE ENGINE

- Cylinder are aligned in single row parallel with crankshaft.- engine either liquid or air-cooled

- Piston either located upright or inverted.

- Invertedengine is generally employed.

- Number of cylinders limited to six only to facilitate cooling and

prevent engine overheating- Cylinder are generally even number to provide proper balance.

Advantages of in-line engine

- Small frontal area, less drag, greater propeller clearance as forinverted engine.

- Shorter main landing gear and provide better visibility

Disadvantages of in-line engine

- Relatively low power to weight ratio, the rearmost cylinderreceives less cooling air

- Low and medium horsepower output to engine fitted to light

aircraft only.

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3. V-TYPE ENGINE

- Two type : a. Inverted V-type engine

b. Upright V-type engine.

- Cylinders are arranged in two rows (bank) forming letter V

- Angle between banks 45, 60 or 90 deg.

- Cylinders are always even number in each row

- The two banks are opposite each other

- Most V-type engine has 8 or 12 cylinders

- Either air cooled or liquid cooled

- Still employed typically found on racing aircraft.

Advantages of V-type engine

- Producing higher horsepower than in-line engine

- Small frontal area with higher power to weight ratio

- Better pilot visibility as shorter/lower main landing gear.

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iv. OPPOSED TYPE ENGINE

- Most popular recip. engine used on light aircraft.

- Engine as little as 36 hp. and as much as 400 hp.

- Cylinder are always even numbers and opposes each other.

- Some engines are liquidcooled, mostly air cooled

- Horizontally installed on fixed wing aircraft.- When installed on helicopter it is mounted vertically.

- Recent development engine employs dual electronic ignitionsystem.

Advantages

- High power to weight ratio because of small and light weightcrankcase.

- Small frontal areas, more streamline and less drag

- Less vibration because the power impulses tend to canceleach other.

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MAJOR ENGINE COMPONENTS1. Basic part of reciprocating engine include:

a. Crankcase

b. Crankshaft

c. Connecting rod

d. Piston

e. Cylinders

f. Valves

g. Valve operating mechanism

2. Valves, pistons and plugs are located in the cylinder

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Opposed Engine Crankcase

- Consist of two halves of cast aluminum alloy.

- Halves split vertically, held together by bolts and nuts

- Manufactured either by sand casting or mold (permold).

- Thinner wall, strong, denser (mold) and fewer tendencies

to crack due to fatigue.- Cylindrical in shape with smooth are machined to serve as

cylinder pad

- Cylinder padplace to mount cylinder to crankcase.

- To allow a crankcase to support a crankshaft, a series oftransverse webs are cast directly into a crankcase.

- Webs integral parts of the structure and houses thatbearings support the crankshaft and strengthen thecrankcase.

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RadialEngine Crankcase

- Radial engine crankcase separates into 4 section

a. Nose section

b. Power section

c. Supercharger

d. Accessories section

a. Nose section

- Front of the crankcase, bolted to the power section

- Made of aluminum alloy, one piece with domed/convex shape.

- Houses and support prop. governor drive shaft,prop. shaft, cam

ring and reduction gear.

- Additionalmounting for magneto and others engine accessories.

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b. Power section

- Section of the crankcase where the reciprocating motion of thepiston is converted to the rotary motion of the crankshaft.

- One or three pieces, made of aluminum or magnesium boltedtogether.

- Contain machined bosses that rigidly support the crankshaft bearingand the crankshaft.

- Cylinder are attached around the perimeter

- Inner circumference of a cylinder pad is chamfered or tapered topermit the installation of O-ring on the cylinder skirt that seal the joint

between the cylinder and cylinder pad

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c. Diffuseror Supercharger section

- Houses the gear train, bevel and spur gear to drivevarious engine components.

- Spur gear drive heavy load on accessories.

d. Accessories section

- Provide mounting for accessories such as magneto,

carb., pump, starter and generator.

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b. CRANKSHAFT

- Purpose to transform the reciprocating motion ofthe piston and connecting rod into rotary motion to

turn the propeller.- The crankshaft may have one or more throws. Twocrank cheek and crankpin is one throw

- Can withstand high stress, made of forged alloy

such as chromium-nikel molybdenum steel.

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b. CRANKSHAFT cond

- Main part of crankshaft

a. Main bearing journal (Main journal)

- Represent centerline of a crankshaft and supportthe crankshaft as it rotates in the main bearings

b. Crankpin

- Attachment points for the connecting rod.

- Forged directly into a crankshaft and offset fromthe main bearing journal.

c. Crank cheeks or crank arms

- Connect the crankpin to the crankshaft

d. Counterweightand dampershelp to balance theshaft dynamically

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b. CRANKSHAFT cond

- Types of crankshaft depend on number and arrangement ofcylinder

- The common typessingle, two, four and six throws

- Single throw crankshaft is used on single row radial engine.

Bearing

- To support and reduce friction between moving part:

a. Plain bearing - radial load onlyb. Ball bearing - high radial load

c. Roller bearing - radial load

d. Tapped - radial and thrust load.

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CRANKSHAFT BALANCE

TO REDUCE ENGINE VIBRATION WHICH CAN CAUSE FATIQUE AND

FAIL AND WEAR EXCESSIVELY

EXCESSSIVE VIBRATION IS CAUSE BY UNBALANCE CRANKSHAFT

TYPE OF BALANCE

1. STATICALLY BALANCE

2. DYNAMIC BALANCE

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DYNAMIC BALANCE

BALANCING THE CENTRIFUGAL FORCE CREATE BY THE ROTATINGCRANKSHAFT AND THE IMPACT FORCE CREATE BY ENGINE POWER

IMPULSE

CORRECTED THROUGH USING OF DYNAMIC DAMPERS

STATICALLY BALANCE

WHEN ENTIRE CRANKSHAFT IS BALANCE AROUND ITS AXIS OF ROTATION

CAN BE ACHIEVED BY PLACING IT IN KNIFE EDGE BALANCING BLOCK

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c. CONNECTING ROD

- Purpose a. To transmit exerted forces on a piston to a

crankshaft.

b. To convert reciprocating motion of piston to a

rotary motion of crankshaft.

- Small end is connected to the piston and big end

connected to the crankshaft.

- Types

a. Plain types

b. Master and articulated type

c. Fork and blade type

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a. PLAINCONNECTING ROD

USED ON INLINE AND OPPOSED ENGINE

BRONZE BUSHING ARE PRESSED AT THE PISTON PIN END

CRANNKPIN END USUALLY FITTED WITH TWO PIECESBEARING AND CAP WHICH IS HELD BY BOLT AND STUD

TO PROVIDE PROPER FIT AND BALANCE CONNECTING RODARE MATCH WITH THE PISTON

STAMP WITH NUMBERS TO IDENTIFY CYLINDER AND PISTON

ASSEMBLY

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b. MASTERAND ARTICULATED ROD

USED ON RADIAL TYPE OF PISTON ENGINE

ONE PISTON IN EACH ROW OF CYLINDER IS CONNECTED TOCRANKSHAFT BY A MASTER ROD

THE REMAINING PISTON IS CONNECTED TO A MASTER ROD THROUGH A

LINK OR ARTICULATED RODSMASTER ROD ARE MANUFACTURED FROM A STEEL ALLOY FORGINGWHILE LINK ARE MANUFACTURED FROM FORGED STEEL ALLOW

LINK ROD IS EITHER I OR H CROSS SECTIONAL PROFILE

MASTER ROD IS THE ONLY BETWEEN THE PISTON AND THE CRANKPIN

LINK ROD IS ATTACHED TO MASTER THROUGH KNUCKLE PIN

SOME KNUCKLE PIN DO NOT IN THE FLANGE HOLE BUT SOME FULLFLOATING

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FORK AND BLADE TYPE

- Used primarily on V-type engine.- Consists of fork-connecting rod and blade

connecting rod

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d. PISTON

- Two primary functions:

a. Draw fuel and air into a cylinder and compress the gases

b. To transmit the force produced by combustion to thecrankshaft

- The ring grooves are cut at outside surface of piston to hold set of pistonrings. As many as six ring grooves.

- The lower/base of the piston are called piston skirt.- Piston are often classified according to their head design.

- Type of heads:

a. Flat head

b. Flat head with valve recessed

c. Cupped head

d. Domed head

e. Truncated cone

- Flat head type is commonly used in modern aircraft

- All piston expend as they heat up. Camground piston compensate foruneven expansion of the piston.

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d. PISTON cont

Piston rings- Perform three functions

a. To prevent gas leakage from combustion chamber

b. Reduce oil leakage into combustion chamber.

c. To transfer heat from the piston to cylinder wall

- Piston ring gap

a. Butt joint

b. Angle joint

c. Step joint

- Types of piston ring

a. Compression ring

prevent gas escape past the piston during engineoperation.

- placed in the ring groove below the piston head.

- no. of ring used on piston determined by the type ofengine and design.

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d. PISTON cont

b. Oil ring

control amount of oil that applied to the cylinder wall as well asprevent oil from entering the combustion chamber.

- 2 types of oil ring

1. Oil control ring- to regulate the thickness of oil film on the cyl. wall.

- placed below compression ring

2. Oil scraper ring (oil wiper ring)

- to regulate amount of oil that passes between thepiston skirt and cylinder wall.

- usually beveled face and installed belowof thepiston skirt.

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d. PISTON cont

- Ring gap must be staggered/offset to prevent gas leak or known as blow-by

ring gaps are staggered at 120 apart for three piston rings.

- Cross section of piston ring

a. Rectangular

b. Taperedc. Wedge

Piston pin

Is to joint the piston to the connecting rod.

- Types of piston pina. Stationary (rigid) pinheld tightly in place by screw that

prevents movement.

b. Semi-floatingretained stationary in the connecting rod.

c. Full-floatingfree to rotate.

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d. PISTON cont

A piston pin must be held in place laterally to prevent it from rubbingand scoring the cylinder walls.

Three devices that are used to hold a piston pin in place are

1. circlets,

2. spring rings, and

3. metal plugs.

A circlet is similar to a snap ring that fits into a groove cut into each endof the piston boss.

A spring ring also fits into grooves cut into the ends of a piston boss butconsists of a single circular spring-steel coil. Both circlets and spring ringsare used primarily on earlier piston engines.

More current practice is to install a plug of relatively soft aluminumcalled a piston-pin plug.

These plugs are inserted into the open ends of the piston pins andprovide a good bearing surface against the cylinder walls.

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e. CYLINDER- Provide a combustion chamber where the burning and expansion of

gases takes place to produce power.

- Houses of piston and connecting rod assembly as well as the valves

and spark plugs.

- Cylinder must be strong, lightweight and good heat-conductingproperties.

- Air cooled cyl. consist of : i. Barrel

ii. Cylinder heads

iii. Mounting flange

iv. Skirtv. Cooling fins

vi. Valve assembly.

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e. CYLINDER cond

Cylinder barrels- Construction for cylinder barrel must be as light as possible.

- Material usedchromium molybdenum steel

- nickel chromium molybdenum steel

- Cylinder barrels are machined with a skirt that project into the

crankcase and mounting flange, used to attach the cylinder to thecrankcase.

- Exterior cylinder barrel consist of several thin cooling fins.

- Threaded at the top part of the barrel so cylinder head can be

screwed into it.

- Cylinder borechoke bore cylinder- smaller at the top for

expansions cause by operating temperature.

- The amount of choke is between .003 and .005 inches.

- Internal surface of the barrel is treated with chrome

plating/electroplating and nitriding to form of case hardening on the

surface.

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e. CYLINDER cond

- Identification for nitrided cylinder by applying blue band around cyl.base or cooling fin, and orange paint for the electroplating cylinders.

- chromium is too smooth that it could not retain enough oil to lubricatethe piston ring

- overcome through process called chromechanneling- chrome channeling is a process where by a reverse current is through acylinder for controlled period of time after chromium is applied

- microscopic crack will occur on the surface that help holding lubricatingoil

- Advantages over nitrided cylinder

1- less susceptible to rust and corrosion

2- once it wear beyond its usable limit it may be chromeplated back to original size

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Cylinder headscond

- Provide an enclosed chamber for combustion

- Heads contain intake and exhaust ports, spark plug,valve actuating mechanism and also conduct heat awayfrom cylinder barrels.

- Made of forged or die-cast aluminum alloy because ofgood heat conductor, lightweight and durable

- Inner surface maybe flat, semi-spherical or peaked.

- The semi-spherical type proved to be the mostsatisfactory and stronger and provide more rapid and

thorough scavenging of exhaust gas.

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e. CYLINDER cond

Cylinder Numbering

- Left or right of an engine always viewing form the rear.

- The crankshaft rotation is also referenced from the rear of the

engine is specified as either clockwise or counterclockwise.

- All cylinders are numbered, odd numbered are on the right and

even numbered on the left.

- Continental engine start its cylinder numbering with the most

rearward cylinder.

- Lycomingengine start with the most forward

- Radialengine cylinders are numbered consecutively starting fromthe top cylinder and progressing clockwise as viewed from the rear of

the engine.

- Double row radial engine, all odd numbered cylinders are in the

rear row and the even numbered cylinders are in the front row

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f. VALVES

1. Purpose is to regulate flow of gases into and out of cylinder byopening and closing valves port at predetermine times.

2. Types of valve:

i. Intake valve (chromium, nickel or tungsten steel)

ii. Exhaust valveexhaust valve stems are hollowed and

partially filled with metallic sodium. (inconel, silicon- chromium or cobalt-chromium alloys)

3. Classified by shape of head

i. Flat head

ii. Semi tulip

iii. Tulipiv. Mushroom

4. Valve springs are hold valve face against valve seat

5. Valve springs are held in place by spring retainer and split key

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g. VALVE OPERATING MECHANISM

- To open and close each valve at correct time

- Consist of :

i. Camshaft or cam rings

ii. Valve lifter or tapped

iii. Pushrod

iv. Rocker arm

- Camshaft is used in opposed engine while cam ring is used in radial

engine

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HYDRAULICLIFTERS

1. MOST OPPOSED ENGINE USED HYDRAULIC LIFTERS2. USED OIL PRESSURE TO CUSHION THE IMPACT OF THE

CAMLOBES STRIKING THE LIFTER AND REMOVES ANY PLAY

WITHIN THE VALVES OPERATING MECHENISM

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OPPOSED ENGINE VALVE OPERATING

MECHANISM

1. Valve operation begins with the camshaft

2. Consists of round shaft with a series of cams or lobes.

3. To transform a circular motion of the crankshaft to a linear motionneeded to actuate valve.

4. The shape of the cam lobes determines valve left (distance a valvelifted off its seat and valve duration)

5. Each valve must open and close for every two rotations of thecrankshaft. (speed of camshaft is one-half that of the crankshaft.

6. OPERATION: camshaft rotates, the lobe raise the valve lifter (tappet),transmits the lifting force of the cam to the push rod

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PUSH ROD

Transmit lifter action to the rocker arm

Hole on each end to allow oil flow from lifter to valve

component

Enclose by thin metal shroud that run from cylinder head to

crankcase

These provide return path for oil that is pump up to cylinder

head

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ROCKER ARM

PURPOSE

Change lifting movement of the pushrod

into downward motion needed to open

the valve

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RADIALENGINE VALVE OPERATING

MECHANISM1. VALVE OPERATING MECHANISM ON RADIAL USED ONE OR TWO

DEPENDING ON THE NO. OF ROWS

2. THE CAMRING IS A CIRCULAR PIECE OF STEEL WITH A SERIES OF CAM

LOBES.3. THE SMOOTH AREA BETWEEN THE LOBES IS CALLED CAM TRACK

4. CAM RING IS DRIVEN BY CRANKSHAFT THROUGH A SERIES OF GEAR.

5. THE SPEED OF THE CAMRING IS CAN BE DETERMINED BY USING THE

FORMULA

1

2 X NUMBER OF LOBES

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VALVE CLEARANCE

SPACE OR CLEARANCE BETWEEN VALVE TIP AND ROCKER ARM FACE

VALVE CLEARANCE

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VALVE CLEARANCE1. To maintain engine running smoothly

2. To set up the valve clearances, refer engine MM specifieseither cold or hot valve clearance.

3. During normal engine operating temperature, the cylinderassemblies expand and force the cylinder along with itvalve operating component further away from thecrankcase.

4. Due to mass the push rod expand less than the cylinderresulting increases in valve clearance.

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PROPELLER REDUCTION GEAR

- Purpose of the reduction gear, permits a propeller to turn slower than

the engine speed.

- Mostly used by the high powered engine.

- Utilize spur gears, planetary gears or a combination of two.

- Whenever reduction gear is used that does not aligned with thecrankshaft, vibration will be created to the engine.

- To minimize the vibration a quill shaft and planetary reduction gear is

used

- Type of propeller shaft

1- Taperedpropeller shaft2- Splinedpropeller shaft

3- Flangedpropeller shaft

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ENGINE IDENTIFICATION- Almost recip. engine are identified by a series of letters and numbers.- Most manufacturers use the same identification code consists of letter or

series of letters followed by number and model designation.

- Ohorizontally opposed engine

Rradial engine

Iinline engine

Vv-type engine

Tturbocharged

Ifuel injected

SsuperchargedGgeared nose section

LLH rotation for multi engine

Hhorizontal mounting for helicopters

Vvertical mounting for helicopter

Amodified for aerobatics

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ENGINE IDENTIFICATION cond

1- e.g ; O-320 indicate horizontally opposed engine with a

displacement of 320 cubic inch.

2- e.g ; LIO-360-C indicate left-hand rotation, fuel injected,horizontally opposed engine, displacement of 320 cubic inch

and C model.

3- e.g : GTSIO-520-F indicate engine is geared, turbocharged

engine, fuel injected, horizontally opposed engine, displaces520 cubic inch and F model

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FINISH FOR THE DESIGN AND CONSTRUCTIONOF RECIP ENGINE

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RECIPROCATING ENGINEOPERATING PRINCIPLES

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ENERGY TRANSFORMATION

- AN ENGINE IS A DEVICE THAT CONVERTCHEMICAL ENERGY OF THE FUEL INTO HEAT

ENERGY

- ONCE CONVERTED, THE HEAT CUASES AN

INCREASE OF GAS PRESSURE IN THE CYLINDERTHAT CONVERT IT INTO MECHANICAL ENERGY

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BASIC OPERATING PRINCIPLES cond

TERM:

1. Type of operating cycle :

a. Four stroke

b. Two strokeThose operating cycles are developed by August Otto, sometimes

referred as OTTO CYCLE.

2. Stroke is a total distance travel of piston most outward and inward.

3. Most outward travel is called top dead center (TDC)

4. Most inward travel is called bottom dead center (BDC)

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ys s u e o v o ec o ogy

BASIC OPERATING PRINCIPLES cond

FOUR STROKE CYCLE

1. The four stroke cycles consists of :

a. Intake stroke

b. Compression stroke

c. Power stroke

d. Exhaust stroke

2. To complete four stroke cycle requires two revolutionsof the crankshaft.

3. Ignition takes place during compression stroke.Therefore in one complete cycle there are four strokeand five events.

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y gy

OPERATING PRINCIPLES

1. The sequences of events of reciprocating engine are :

i. Intake

ii. Compression

iii. Ignition

iv. Power

v. Exhaust

i. Intake

- Piston travels from top dead center to bottom dead center.

- Intake valve opens and exhaust valve closes.

- Fuel and air mixture drawn into cylinder

ii. Compression

- Piston travels from top dead center to bottom dead center.

- Both valves are closed

- Mixture fuel and air compressed

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iii.. Ignition

- Compressed mixture is ignited by spark plug.

- Both valves are still closed

- Piston near top/top dead center

iv. Power- Expanded burning gases forces piston downward

- Crankshaft rotates to produces work.

- Both valves are still closed

v. Exhaust

- Exhaust valve opens and intake valve still close.

- Piston travels from bottom to top dead center.

- Burned gases scavenged out of cylinder.

2. All five events are considered one cycle.

BASIC OPERATING PRINCIPLES cond

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VALVE TIMING OR MODIFIED OTTOCYCLE

TERM USED TO DESCRIBES THE POINT ATWHICH THE INTAKE AND EXHAUST BEGIN

TO OPEN AND CLOSED DURING THE FOUR

STROKE CYCLE

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VALVE TIMING- To increase engine performance and more efficient.

- The no. of crankshaft degrees that the intake valve opens early

before the piston reaches TDC (valve lead).

- To ensure sufficient charge (mixture) enter the cylinder.

- The no. of degrees the exhaust valve remain open after TDC. (valve

lag).

- To ensure fully scavenge of hot gases from the cylinder.

- Combination of the valve lead and valve lag is called VALVE

OVERLAP.

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- Purpose of valve overlap is to allow the charge (mixture) toenter the cylinder as early as possible to increase engine

performance and aid in cylinder cooling and also to ensurefully scavenge of hot gases from the cylinder.

- Therefore, e.g. if the amount of intake valve open, will be 15degrees to reach TBC, 180 degrees to reach BDC then 45

degrees past BC and the total of 240 degrees of rotation.(duration of intake valve open).

VALVE TIMING

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FIRING ORDER

Define as

- the sequence in which ignition occurs in different

cylinder

- Each engine is designed with a specific firing order tomaintain balance and reduce vibration.

Example

- continental0-200a= 1324

- lycoming0-320-E3D = same order but cylinder arenumbered differently

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FIRING ORDER ON RADIAL ENGINE

THE ODDCYLINDER FIRE FIRST FOLLOWED BY THE EVEN NOCYLINDER.

14 CYLINDER = +9 -5, MEANS IF NO 1 IS FIRING THE NEXTCYLINDER TO FIRE IS 1 + 9 = 10 CYLINDER, THE NEXT CLINDER TOFIRE IS 105 = 5 AND SO O N

18 CYLINDER +117, IF NO 1 CYLINDER IS FIRING THE NEXTCYLINDER TO FIRE IS 1 + 11= 12 NEXT WILL BE 127 = 5

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BASIC OPERATING PRINCIPLES cond

TWO STROKE CYCLE

1. Has the same five events and only two piston strokes rather than fourstrokes in only one crankshaft revolution to complete the cycle.

2. Each stroke two events take place.

3. When piston moves up induction and compression takes place.4. Ignition occurs when piston moves up a few degrees before top dead

center.

5. When piston moves down power and exhaust occur

6. During downward movement of pistoncompression also takes place

in crankcase not in cylinder.

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WORK-POWER CONSIDERATIONS

ALL AIRCRAFT ENGINE ARE TESTED AND RATED ACCORDING

TO THEIR ABILITY TO DO WORK AND PRODUCE POWER.

ENGINE DESIGNS AND CONSTRUCTION DETERMINES HOW

EFFECTIVE IN CONVERTING FUELS CHEMICAL ENERGY TO

WORK AND POWER

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DEFINATION OF WORK If force applied to an object and the object moves,

work is done.

Amount of work done is directly proportional to theforce applied and distance the object moves.

If force is applied to an object and the does notmoves , work is not done.

Work produced by the engine is used to turn the

propellerwork (w) = force (f) x distance (d)

= ______ ft/lbs

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DEFINATION OF WORK English system, work is typically measured in foot-pounds. One foot-

pound is equal to one pound of force applied to an object through thedistance of one foot

In the metric system, the unit of work is the joule.

One joule is the work done by a force of one newton acting through adistance of one meter.

One pound is equal to 4.448 newtons.

The work produced by an engine is used to turn a propeller which isproduces thrust to move an aircraft.

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POWER

When determining the amount of work done, time required to do thework is not considered, Power, on the other hand, does take time intoconsideration.

Define as time rate of doing work.

FORMULA

FORCE X DISTANCE = ___________ft/lbs/secTIME

When rating engines, power is a primary consideration because itrepresents how quickly an engine-propeller combination can respond topower demands.

Power is a critical factor when determining whether or not an engine candeliver the force needed to produce a specific amount of work in a giventime.

E.g., a large airplane needs more power to take off in the samedistance as a small airplane because more force is needed to accelerate aheavier object the same distance in the same amount of time.

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HORSE POWER Another unit of measure for power is the horse-power.

The amount of power required to do 33,000 ft/lbs work in 1 minor 550 foot-pounds of work in one second.

HORSEPOWER = FORCE X DISTANCE

33000 X TIME

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INDICATED HORSE POWER

(IHP) is the total power actually developed in an enginescylinders without reference to friction losses within theengine.

To calculate indicated horsepower, the average effective

pressure within the cylinders must be known. One way to determine the effective pressure is to attach a

mechanical indicating device to the engine cylinder thatrecords the actual pressure existing in the cylinder during acomplete operating cycle.

This average pressure is referred to as indicated meaneffective pressureand is included in the indicated horsepowercalculation with other engine specifications.

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INDICATED HORSE POWER

FORMULA

PLANK

33,000

P = IMEP inside the during a power strokeL = length of stroke

A = area of piston head

N = number of power stroke per min for one cylinder.

On a four-stroke engine, this is found by dividing the rpm bytwo.

K = number of cylinder

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FRICTION HORSEPOWER

Not all of the horsepower developed by engine goes to

driving the propeller, all the moving part inside the engine

will creating friction.

Engine lubrication is crucial in limiting friction and wear, but

cannot completely eliminated.

The power required to overcome the friction and energy

losses

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BRAKE HORSEPOWER

The actual power delivered to the propeller shaft

IHP - FHP = BHP Devices that are capable to measuring torque, including

the dynamometer and torquemeter.

Early powerplant design engineers measured brake

horsepower using a Prony brake dynamometer ,on mostmodern engines is measured with an electric or hydraulic

dynamometer.

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PISTON DISPLACEMENT

Volume of air displace by a piston as it moves from

BDC to TDC

FORMULA - A X L X N

A = area of piston head ( r )

L = length of stroke in inches

N = number cylinders

piston displacement always in cubic inches

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THERMAL EFFICIENCY

- A ratio of the amount of energy converted to useful work tothe amount of heat energy contained in the fuel used tosupport combustion

- E.g - two engine that produce the same amount hp butconsume different amount of fuel

- the engine that consume less amount of fuel has higher

thermal efficiency

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VOLUMETERIC EFFICIENCY Ratio of volume of fuel and air takes into the cylinder to the

total piston displacement

If engine draws in volume of fuel/air that is exactly equal to

the total piston displacement, VE would be 100%

Varies with change of atmospheric condition

VE in normally aspirated engine is less than 100 %

VE on turbo charge engine can exceed than 100 %

Anything that decreases the density, or volume of air

entering a cylinder decreases volumetric efficiency.

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MECHANICAL EFFICIENCY

Is the ratio of brake horsepower to indicated horsepowerand represents the percentage of power developed in thecylinders that reaches the propeller shaft.

E.g an engine develops 160 brake horsepower and 180indicated horsepower, the ratio of brake horsepower toindicated horsepower is 160:180, which represents amechanical efficiency of 89 percent.

The factor that has the greatest effect on mechanicalefficiency is the friction within the engine itself.

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FACTORS THAT EFFECT VOLUMETRIC EFFICIENCY OF A

NON-TURBOCHARGED ENGINE

1. PART THROTTLE OPERATION

2. LONG, SMALLER DIAMETER INTAKE PIPES

3. INDUCTION SYSTEM SHARP BEND

4. HIGHCARBURETOR AIR TEMPERATURE

5. INCOMPLETE SCAVENGING

6. IMPROPER VALVE TIMING

7. INCREASE IN ALTITUDE

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FACTORS AFFECTING POWER OF THE ENGINE

1. MANIFOLD PRESSURE

2. DETONATION AND PRE IGNITION

3. COMPRESSION RATIO

4. IGNITION TIMING

5. ENGINE SPEED

6. SPECIFIC FUEL CONSUMPTION

7. ALTITUDE

8. FUEL / AIR RATIO

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MANIFOLD PRESSURE

CHANGE OF MANIFOLD PRESSURE AFFECT THE

AMOUNT OF POWER AN ENGINE CAN PRODUCE CONTINUE SUPPLY OF HIGH MANIFOLD PRESSURE

CAN DAMAGE THE ENGINE

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DETONATION AND PRE-IGNITION

DETONATION IS UNCONTROL EXPLOSIVE IGNITION IN THECYLINDER

PROMOTES TO HIGH CYLINDER TEMPERATURE

CAN BE DETECT THROUGH KNOCKING IN THE ENGINE

PRE-IGNITION FUEL/AIR MIXTURE IGNITES TOO SOON CAUSE BY HOT SPOT DUE TO OVERHEATED VALVE EDGE,

SILICA DEPOSIT ON SPARK PLUG, OR RED HOT SPARK PLUGELECTRODE

DETONATION AND PREIGNITION CAN OCCURSIMULTANEOUSLY

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COMPRESSION RATIO

A RATIO OF CYLINDER WHEN THE PISTON IS AT BDC TO WHEN THE PISTONIS AT TDC

DETERMINE THE AMOUNT OF HEAT ENERGY THAT IS CONVERT TOUSEFUL WORK

HIGH CR ALLOWS THE FUEL/AIR MIXTURE TO RELEASE ENERGYRAPIDLY AND PRODUCE MAXIMUM PRESSURE INSIDE THECYLINDER JUST AS THE PISTON BEGIN THE POWER STROKE

ONLY CAN BE INCREASED OR DECREASED BY ALTERING THE ENGINEDESIGN

CHARACTERISTIC OF AVAILABLE FUEL DETERMINE THE PRACTICALOF COMPRESSON RATIO THAT CAN BE USED IN ENGINE DESIGN

IF TURBO CHARGE ENGINE DEGREE OF TURBOCHARGING LIMIT THECOMPRESSION RATIO

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IGNITION TIMING

CHANGE IN IN ENGINE IGNITION WILL ALSO EFFECT THE ENGINE

POWER

TO ENSURE COMPLETE COMBUSTION THE ENGINE MUST BE TIME

PROPERLY

EARLY IGNITION LOST POWER DUE TO MAXIMUM PRESSURE IN THECYLINDER BUILT TOO EARLY , AND EXPANDING GAS OPPOSED THE

ROTATIONAL INERTIA BECAUSE THE PISTON IS STILL MOVING UPWARD

GAS PRESSURE ON PISTON HEAD DOES NOT BUILD UP TO EXPECTED

LEVEL

LATE IGNITION DOES NOT ALLOW ENOUGH TIME FOR COMPLETE

COMBUSTION

CAN LEAD TO DETONATION

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SPECIFIC FUEL CONSUMPTION

A NUMBER OF POUND OF FUEL BURN PER HR TO PRODUCE 1HORSEPOWER

IF AN ENGINE BURN 12 GALLON WHILE PRODUCING 180 BHP THEREFOREBSFC IS .4

- CALCULATION 7 X 12 = 84

- 84 DEVIDE BY 180 = .46666666666

FACTORS EFFECTING ENGINE FUEL CONSUMPTION

- ENGINE SPEED

- DESIGN

- VOLUMETRIC EFFICIENCY- FRICTION LOSSES

THE BEST FUEL CONSUMPTION IS APPROXIMATELY AT 75% POWER (CRUISING )

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ALTITUDE

ANY TIME ENGINE IS OPERATED ABOVE SEA LEVAL LESSAIR IS DRAWN INTO THE ENGINE THUS RESULTING INDECREASE ENGINE POWER OUTPUT

DENSITY IS A TERM GIVEN TO DESCRIBE THE DENSITY OFAIR AT GIVEN ALTITUTE

EVENTHOUGH THE ACTUAL ALTITUTE DOES NOTCHANGE DENSITY ALTITUTE CAN CHANGE CONSTANTLYDUE TO CHANGE AIR TEMPERATURE

CAN BE OVERCOME BY THE USED TURBOCHARGER

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FUEL/AIR RATIO

STOICHIOMETRIC MIXTURE IS A PERFECTLY BALANCE FUEL/AIR MIXTURE

RICH MIXTURE MORE FUEL LESS AIR E.G 14: 1.

COMBUSTIBLE FUEL AIR RATIO IS RANGE BETWEEN 8:1 TO 18:1

CONTROL MIXTUREALLOW ADJUSTMENT OF THE FUEL/AIR RATIOFROM IDLE CUT-OFF TO FULL RICH MIXTURE.

LEANING MIXTURE CAN RAISE ENGINE OPERATING TEMPERATURE

LEANING MIXTURE IS NECESSARY AS ALTITUTE INCREASE BECAUSE FUELWILL BECOME RICHER DUE TO LESS AIR AT ALTITUTE

BEST POWER MIXTURE USED DURING TAKE OFF

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