ENGINE COMPONENTS

AE 422Agricultural Power and

Its Sources

Class RecordAttendance Quizes

Names 11-18-13 11-25-13 12/02/13 12/09/13 Absences Q1 Q2 Q3Acay, Nollen Grace P P P 0 30 46 25Barbo, P P P 0 30 50 30Bayan P P P 0 30 41 14Borda P P P 0 14 66 22Borero P P P 0 31 45 17Duran P P P 0 16 57 23Eslao P P P 0 30 43 22Flores P P P 0 18 46 27Gallera P P P 0 9 57 20Gomez, P P P 0 13 57 28Lampon P P P 0 23 48 25Mateo P P P 0 12 40 15Omega P P P 0 26 42 26Paulino P P P 0 28 - 16Pino P P P 0 27 27 20Reponte P P P 0 15 48 20Salik P P P 0 26 33 29Samillano P P P 0 20 22 24Travilla P P P 0 20 36 10Pavo P A P 1 3 30 20Florido P P P 0 23 39 28Sasi P P P 0 31 55 14Nadala P P P 0 27 42 26Garcia P P P 0 25 - 15

Short Quiz (50 pts)

1. What is the piston speed of an engine having a revolution of 2100 revolution per minute and a stroke of 21 cm (15 pts)

2. Given a four-cylinder Otto cycle engine with a 70-mm bore, 135-mm stroke, and a clearance volume of 0.121 L . (Assume n = 1.4). A) What is the total engine displacement?. B) What is the compression ratio of the engine? C) What is the theoretical Cycle efficiency? (25 pts)

Short Quiz (50 pts)

1. The volume of gas in the cylinder when the piston is at head dead center (HDC) is called _________. (2 pts)a. Total Volumeb. Clearance Volumec. Displacement Volumed. Head Dead Volume

Short Quiz (50 pts)

2. What is the volume fo the air-fuel mixture in the figure (2 pts)a. Total Volumeb. Displacement Volumec. Clearance Volumed. Exhaust Volume

Short Quiz (50 pts)

3. At point 0 the intake valve is ___________ . (2 pts)a. Openb. Closedc. Semi Opend. Semi Closed

Short Quiz (50 pts)

4. The process that occurs between point 1 and 2 is ______________. (2 pts)a. polytropic compression strokeb. polytropic expansion strokec. Power stroked. Exhaust Stroke

Short Quiz (50 pts)

5. It is the theoritical cycle for spark ignition system?a. Diesel Cycleb. Carnot Cyclec. Gasoline Cycled. Otto Cycle

ANSWERS

1. What is the piston speed of an engine having a revolution of 2100 revolution per minute and a stroke of 21 cm (15 pts)

S=2LNS=2∗21∗2100S=88200 cm/minS=1470 cm/ sec

ANSWERS

2. Given a four-cylinder Otto cycle engine with a 70-mm. bore, 135-mm stroke, and a clearance volume of 0.121 L (7.386 in.3). (Assume n = 1.4). A) What is the total engine displacement?.

V e=nV d V d=πD2

4L

V d=π72

413.5

V d=519.5cc

V e=4∗519.5V e=2078cc

ANSWERS

2. Given a four-cylinder Otto cycle engine with a 70-mm. bore, 135-mm stroke, and a clearance volume of 0.121 L (7.386 in.3). (Assume n = 1.4). B) What is the compression ratio of the engine?

CR=V TV C

=V D+V CV C

CR=V TV C

=519.5+121121

CR=5.294

Probably a Gasoline Engine

ANSWERS

2. Given a four-cylinder Otto cycle engine with a 70-mm. bore, 135-mm stroke, and a clearance volume of 0.121 L (7.386 in.3). (Assume n = 1.4). C) What is the theoretical Cycle efficiency?

Ottocycle efficiency=1−1

rn−1

Ottocycle efficiency=1−1

5.2941.4−1

Ottocycle efficiency=0.4866

ProbablyNot Yet

INVENTED

ANSWERS

1. The volume of gas in the cylinder when the piston is at head dead center (HDC) is called _________. (2 pts)a. Total Volumeb. Clearance Volumec. Displacement Volumed. Head Dead Volume

ANSWERS

2. What is the volume fo the air-fuel mixture in the figure (2 pts)a. Total Volumeb. Displacement Volumec. Clearance Volumed. Exhaust Volume

ANSWERS

3. At point 0 the intake valve is ___________ . (2 pts)a. Openb. Closedc. Semi Opend. Semi Closed

ANSWERS

4. The process that occurs between point 1 and 2 is ______________. (2 pts)a. polytropic compression strokeb. polytropic expansion strokec. Power stroked. Exhaust Stroke

ANSWERS

5. It is the theoritical cycle for spark ignition system?a. Diesel Cycleb. Carnot Cyclec. Gasoline Cycled. Otto Cycle

A cutaway view of an internal combustion engine. (Courtesy of Deere & Company.)

THE CYLINDER BLOCK

● The cylinder block is the backbone of the engine. It supports most of the other engine parts and holds them in proper relationship to each other.

● The block also may act as part of the framework of some tractors and support the front wheels (Figure 3.2).

Types of Cylinder Liner

● Enbloc – cylinders are cast directly into the block

● Dry liner – the liner does not come into contact with the engine coolant

● Wet sleeve – serves as the only wall between the piston and coolant.

THE CYLINDER HEAD

● The open ends are sealed by means of a cylinder head

In addition to sealing the combustion chambers, the head contains thevalves and passages, or ports, to the intake and exhaust manifolds

THE CYLINDER HEAD

● A special cylinder head gasket is used between the head and block .

● Typically, such gaskets are made of asbestos and include metallic rings around each cylinder to aid in sealing in combustion gases.

● The head is fastened to the block with high-strength head bolts, which must be tightened down gradually and uniformly to ensure good sealing.

THE VALVE TRAIN

● The valves control the inflow of unburn fuel and the outflow of the burned fuel.

● The valve actuation begins with the camshaft, to the tappet, push rod and soon.

THE VALVE SEATING

PISTON AND CONNECTING ROD ASSEMBLIES

TYPES OF PISTON RINGS

CRANKSHAFTS, FLYWHEELS AND BALANCERS

BEARINGS

PRACTICAL ENGINE CYCLES ANG TIMING

In either type of engine, it is essential that certain events are timed correctly with the movement of the piston, or the engine will not run.

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Valve Timing

– Cam lobes to camshaft lift the tappets. Each rocker arm translates upward movement of a tappet and push rod into downward movement of a valve, thereby compressing the valve spring and opening the valve.

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Ignition Timing

– Ideally, nearly all of the fuel energy would be released when the piston was at HDC and ready to begin the power stroke.

– Spark advance refers to the number of crankshaft degrees before HDC at which the spark plug fires.

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Injection Timing

– Injector nozzles are used to inject fuel into diesel engines. The fuel does not ignite instantaneously when it is injected into the hot combustion chamber.

– ignition delay, injection must start before HDC if a high percentage of the fuel is to be consumed before the piston is well past HDC. Timing of the start of injection is selected to optimize performance of each model of engine, but is typically in the range from 15° to 30° before HDC.

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Firing Intervals

– The firing intervals refer to the number of degrees of crankshaft rotation between successive power strokes.

– Cylinders must be numbered in a multicylinder engine for purposes of identification. Numbering begins at the front of the engine.

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Firing Interval for a 4 cylinder

PRACTICAL ENGINE CYCLES ANG TIMING

FOUR-STROKE-CYCLE ENGINES

● Firing Orders

– There are two possible firing orders for the engine of 4 cylinders. The firing order given in the figure is as follows:

1 - 3 - 4 - 2

or

1 - 2 - 4 – 3

Most Common for 6 cylinder

1 - 5 - 3 - 6 - 2 - 4

PRACTICAL ENGINE CYCLES ANG TIMING

TWO-STROKE-CYCLE ENGINES

● Two-Cycle Spark-Ignition Engines

– While the piston is moving upward on a compression stroke, a vacuum is created in the crankcase, and the check valve opens to admit the air fuel mixture. The check valve closes, and the mixture in the crankcase is compressed as the piston moves downward on the power stroke.

PRACTICAL ENGINE CYCLES ANG TIMING

TWO-STROKE-CYCLE ENGINES

● Two-Cycle Spark-Ignition Engines

– Two-cycle engines have the advantage of a high power-to-size ratio. By producing a power stroke during every revolution of the crankshaft, a two-cycle engine can produce much more power than a four-stroke-cycle engine of the same size.

PRACTICAL ENGINE CYCLES ANG TIMING

TWO-STROKE-CYCLE ENGINES

● Timing in the Two-Cycle Engine

– There is no valve train in two-cycle spark-ignition engines because the moving piston covers and uncovers the intake and exhaust ports in the cylinder wall and thus the timing is set when the engine is built.

● The exhaust valve begins to open at 97.5° before CDC, begins closing at 43° after CDC, and is fully closed at 63° after CDC.

● The intake port is uncovered after the exhaust valve is closing on the downstroke and before the exhaust valve closes on the upstroke. Thus, approximately 55% of the cycle is used for compression and power; the remaining 45% is used for scavenging exhaust gases and intake of fresh air.

PRACTICAL ENGINE CYCLES ANG TIMING

TWO-STROKE-CYCLE ENGINES

● Timing in the Two-Cycle Engine

● The spark plug is timed to fire approximately 6° to 8° before HDC in two-cycle spark-ignition engines.

● Typically, these engines run at full speed when doing work, and no ignition advance system is needed.

● Diesel injection begins at 23.5° before HDC in a typical two-cycle diesel engine and ends at 6° before HDC when the engine is running at full load. Thus, injection ends much earlier than in four-cycle diesels, where injection can continue well past HDC at full load.

● Extending fuel injection into the power stroke of two-cycle diesel engines would not be satisfactory

PRACTICAL ENGINE CYCLES ANG TIMING

TWO-STROKE-CYCLE ENGINES

● Firing Intervals and Orders

● Firing Intervals and Orders ● The firing interval of a

two-cycle engine is half that of a comparable four-cycle engine as indicated by Equation

Reminders:

● First Long Exam Next meeting● Make up for absenses on Exam till Thursdays.● Next Module: Engine Performance

– References● Goering, Carroll E., and Alan C. Hansen. 2004. Practical Engine Cycles and

Timing. Chapter 2- 3 in Engine and Tractor Power, 4th edition, St. Joseph, Michigan: ASAE. © American Society of Agricultural Engineers.

● Roth, Alfred C. Small Engine● Philippine Agricultural Engineering Standards