The Small Internal Combustion Engine

Objectives Identify the operating principles of the internal combustion engine. Identify the operating characteristics of the two and four-stroke cycle engine. Identify the basic parts of the internal combustion engine. Compare the operation of the spark-ignition gasoline engine and the compression-ignition diesel engine.

Technology in Mechanical Machines Technology is much advanced since 1876 when the first external combustion steam tractor was successfully manufactured. –Everything is more efficient –Practical

Motors vs. Engines Motors –Motors must be supplied with energy from an external power source Engines –Identifies a machine which is able to produce power independent from an external power source.

Internal Combustion Engine vs. External Combustion Engine Internal Combustion Engine –Capable of converting heat, developed by the burning of a fuel within a combustion chamber External Combustion Engine –Steam powered

Air Cooled vs. Water Cooled Air Cooled Water Cooled

Principles of Engine Operation Two types of Internal-Combustion engines are in present use. –The Piston Engine Sometimes called the “reciprocating” type engine because the piston moves up and down in the cylinder in a reciprocating action –Rotary Engine Two Types –The Turbine Engine used in jet aircraft –Wankel Engine

Rotary Engines Wankel Engine

Rotary Engines

Basic Parts of the Piston Engine Cylinder –Cylinder and housing The cylinder or block is usually cast iron or aluminum

Basic Parts of the Piston Engine Piston –Sliding part of the combustion chamber –It performs the important function of transmitting heat energy into straight line motion. Piston Rings –Compression, Scrapers, and Oil

Basic Parts of the Piston Engine Connecting Rod –Transfers the sliding force of the piston to the crankshaft.

Basic Parts of the Piston Engine Crankshaft –The purpose of the crankshaft is to convert the reciprocating action of the piston into rotary motion and force. –Crankshafts are manufactured using highly refined nodular cast iron.

Basic Parts of the Piston Engine Flywheel –Attached to one end of the crankshaft. –The function of the flywheel is to even out power flow to the crankshaft by resisting any change in speed of rotation –Small Engine-Helps to cool the engine –It is usually part of the magneto-ignition system

Basic Parts of the Piston Engine

Engine Operation Spark Ignition –A mixture of air is drawn into the combustion chamber of the cylinder through the intake valve or port –A mixture is then compressed into a much smaller volume –The compressed gases are ignited at the correct position of the piston in the cylinder –The burning gases then expand, driving the piston down with great force. –During the end of the stroke, the exhaust port or valve opens releasing spent gases.

Engine Operation-Spark Ignition The first successful engine to operate in this manner was developed by Dr. N.A. Otto in 1876 The engine required 4-strokes of the piston to complete the events in the proper sequence.

Four-Stroke-Cycle Engine

Intake Stroke –This is the process of getting the fuel and air required for combustion into the combustion chamber. –The exhaust valve is closed and the intake valve is open. –The piston is moving down in the cylinder and the fuel air mixture is drawn into the combustion chamber. Compression Stroke –The process of compressing the air and fuel mixture in the combustion chamber. –Both valves are closed –Piston is moving up in the cylinder. –The spark plug will ignite the mixture as the cylinder reached TDC –The spark causes an explosion forcing the piston down in the cylinder

Four-Stroke-Cycle Engine Power Stroke –This is the result of converting the chemical potential energy to mechanical power by the rapid expansion of gasses in the cylinder. –These gasses are produced by the combustion of the compressed fuel/air mixture. –Both valves are closed and the piston is moving downward in the cylinder Exhaust Stroke –This is the process of removing the spent products resulting from combustion in the combustion chamber. –After the power stroke, the cylinder contains burned gasses. –During the exhaust stroke, the exhaust valve opens and the spent gasses are forced out of the cylinder. –Exhaust valve is open and the piston is moving up in the cylinder.

Four-Stroke-Cycle Engine

Classification of Internal Combustion Piston Engines Internal Combustion Engines can be classified by the following manner. –Four and Two Stroke Engines –Classified by Power –Classified by Piston Displacement –Number of Cylinders –The manner in which the cylinders are arranged –Fuel they use

Number of Cylinders Single Cylinder –These Engines only have one cylinder –Usually small horsepower engines

Number of Cylinders Multi-Cylinder Engines –Engines that have 2, 3, 4, 5, 6, 8, 10, or 12 cylinders

Cylinder Arrangement In-Line Engine –All Cylinders are in a straight line

Cylinder Arrangement V-Blocks –Means the engine cylinders are arranged in a “V” configuration with two banks of cylinders on a 90 degree angle operating off the same drive shaft.

Cylinder Arrangement Slant –Mopar® or Dodge Engines –Not used in the agricultural industry

Two-Stroke-Cycle Engine

Engine Operation Compression Ignition Engines –Engines which burn gasoline use an electric spark to ignite the air fuel mixture. –Compression Ignition Engines use the heat generated by compression to ignite the fuel –Diesel Engine –Most of them are 4 stroke diesel engines Intake, Compression, Power, and Exhaust

Compression Ignition Engines