Engines: Motive Power Types

Motive power fundamental principles	Pressure & temperature	The pressure and temperature of a gas are linked. As pressure goes up and down, so does temperature.
	Pressure & volume	Pressure and volume are in inverse relation. As one rises, the other falls.
	Temperature & energy	The temperature of a gas is a measure of how much energy it has.
	Understanding power and torque	When an piston is forced down the cylinder during the power stroke it applies the force to the connecting rod. The connecting rod then causes the crankshaft to turn. The rotational force applied to the crankshaft is called torque.

4-stroke spark-ignition engines	Basic 4-stroke principles	The five events of an internal combustion engine are Intake, Compression, Ignition, Power, and Exhaust. In a 4-stroke gasoline engine, the crankshaft does two revolutions in each engine cycle. Only one of its 4-strokes delivers energy to the crankshaft.
	4-stroke engine cycle	A stroke is the movement of the piston from top dead center to bottom dead center.

2-stroke spark-ignition engines	Basic 2-stroke principles	In most 2-stroke gasoline engines the inlet and exhaust ports are opened and closed by the movement of the piston, not valves.
	2-stroke engine power stroke	In a 2-stroke cycle there is only one revolution and one power stroke.
	2-stroke engine cycle	In a 2-stroke gasoline engine, the air-fuel mixture first enters the crankcase. It then passes through the transfer port into the combustion chamber.
	2-stroke intake system	In some 2-stroke gasoline engines, intake is controlled by a rotary valve in the crankshaft. Others systems use a reed valve attached to the crankcase.
	2-stroke cycle	In a 2-stroke gasoline engine the events occurring below the piston are: intake of the mixture into the crankcase and its pre-compression. The events occurring above the piston are: compression of the mixture, combustion, and scavenging of exhaust gases.

Spark-ignition engine components	Basic engine components	The cylinder head attaches to the cylinder block. A gasket makes a seal between them. Some cylinder blocks have passages to carry oil and coolant.
	4 & 2-stroke engine differences	Ports in the cylinder head or walls carry air-fuel mixture and exhaust gases. In 4-stroke engines, valves open and close the ports. A rocker arm acts on a valve spring to operate the valve.
	Engine cams & camshaft	A cam is a lobe on a camshaft, shaped to control how the valve opens and closes. The camshaft keeps all of the valves working with the correct timing and in the correct sequence.
	Engine power transfer	Power can be transferred from the crankshaft to the camshaft by timing gears, a timing chain running on sprockets, or a timing belt running on toothed pulleys.
	2-stroke power transfer	The crankcase is the lower part of the cylinder block. In a 2-stroke gasoline engine, air-fuel mixture flows through a transfer port from the crankcase to the combustion chamber.
	Scavenging	In crossflow scavenging the inlet or transfer port is opposite the exhaust port. In loop scavenging the inlet or transfer ports are within 90° of the exhaust ports.
	Counter weights	The crankshaft is the main rotating component in the engine. The crankshaft rotates in main bearings. The flywheel stores momentum during non-power strokes.
	Piston components	The connecting rod secures the piston to the crankshaft. The piston transfers the force produced by the combustion to the crankshaft. Piston rings make a seal between the piston and the cylinder wall.
	Alloys	An alloy is a combination of materials to make a substance that has properties that are different from the original materials.

Rotary spark-ignition engine & components	Basic principles of the rotary engine	The rotary engine is very powerful for its size. It uses a rotor instead of pistons. It is an internal combustion engine so it uses the five events: Intake, Compression, Ignition, Power , Exhaust.
	Basic components of the rotary engine	The rotor is attached to an eccentric shaft. During combustion, a gear in the rotor makes the rotor walk around a stationary gear. This combines with the eccentric shaft to give the rotor planetary motion.
	Rotary engine cycle	Inlet and exhaust ports are covered and uncovered by the lobes of the turning rotor. As the rotor turns, the working chamber changes size. After intake, it becomes smaller, and compresses the air-fuel mixture.
	Rotary/piston engine comparison	For each complete rotation of the rotor, there are three power pulses, one for each chamber. At any one time, each chamber is in a different phase.
	Rotary engine power pulses	The eccentric shaft does one revolution for each power phase. That means three revolutions for each rotor rotation. So the eccentric shaft turns at three times the speed of the rotor.
	Renesis rotary engine	The Renesis engine is a further development of the "Wankel" rotary engine. The operating cycle is the same as the conventional rotary engine, with improvements to it's design which has the result of improving fuel economy when under load.

Alternative engine cycles	Alternative engine cycles	The Miller Cycle engine and the Atkinson Cycle engine are both variations on the traditional four-stroke spark ignition engine. These engines operate more efficiently, but produce lower power outputs.

Hybrid drive systems	Hybrid vehicles	Hybrid vehicles combine an internal combustion engine with an electric motor, producing significantly lower emissions and increased fuel economy.
	Hybrid electric vehicle models	Hybrid electric vehicles (HEV) use two or more energy conversion technologies. This is usually a combination of a conventional engine with extra batteries driving electric motors.
	Hybrid vehicle systems	There are three hybrid vehicle systems which combine an internal combustion engine with an electric motor. They are: series; parallel; and series-parallel.
	Series-parallel hybrid systems	The series-parallel hybrid system uses an electric motor to drive the vehicle at low loads and speeds and a gasoline engine when loads and speeds increase. A control unit determines the best balance of power to achieve the most efficient vehicle operation.
	Hybrid system components	A permanent magnet brushless motor/generator is mounted adjacent to the engine. A smaller motor/generator replaces the engine flywheel. The motor control unit controls the delivery of electric current to and from the battery and the electric motors.
	Hybrid vehicle driving	When the vehicle is moving off from a stationary position, and when travelling at low to moderate speeds, the main electric motor drives the vehicle. During normal driving, the combustion engine starts and drives the generator & the power divider.

Compression-ignition engines	Basic 4-stroke diesel principles	The 4-stroke diesel engine operates with the five events common to all internal combustion engines: Intake, Compression, Ignition, Power, and Exhaust.
	4-stroke diesel engine cycle	In a 4-stroke diesel engine, the piston travels one stroke each for intake, compression, power, and exhaust. A stroke is the distance from top dead center to bottom dead center.
	Basic 2-stroke diesel principles	The 2-stroke diesel engine is an internal combustion engine with the five events common to all such engines: Intake, Compression, Ignition, Power, Exhaust.
	2-stroke diesel engine cycle	The 2-stroke diesel engine uses all of the five events in just 2-strokes. The crankshaft makes one revolution for each engine cycle.
	Three phases of combustion	The combustion process in the cylinder of a compression-ignition engine is usually described in three phases: Ignition delay, flame spread and direct burning.

Compression-ignition engine components	Basic diesel engine components	Diesel engine parts are usually heavier or more rugged than those of similar output gasoline engines. Their engine blocks and cylinder blocks are usually made of cast iron.
	Diesel engine passages	In a diesel engine, just air enters the combustion chamber first. It is then highly compressed. Fuel is injected and ignites due to heat of the compressed air. That's why diesels are called compression-ignition engines.
	Diesel fuel delivery	In direct injection fuel is injected directly into the combustion chamber. In indirect injection fuel is sprayed into a smaller separate chamber in the cylinder head. A glow plug helps the combustion start.
	Direct injection	Most valves in diesels are parallel to the center-line of the engine. Small 4-stroke engines usually have one inlet and one exhaust valve per cylinder. Larger 4-stroke diesels may have two of each per cylinder.
	Diesel valves & components	Valves in diesel engines are usually operated by a pushrod system. The camshaft is mounted in the engine block near the crankshaft. It keeps the valves working in sequence.
	Diesel scavenging	In uniflow scavenging air flows towards top of the cylinder. In crossflow scavenging air enters one side of cylinder, exhaust gases exit on the other. In loop scavenging air flows up in a loop across the top of the piston.
	Crankshaft rotation	In a 2-stroke diesel engine, the camshaft and crankshaft must rotate at the same speed. So the gears driving them must be the same size.
	Diesel crankshaft	In a 4-stroke cycle, only one stroke in four delivers energy. In a 2-stroke, it is only one stroke in two. A flywheel stores this energy to help turn the crankshaft through the non-power strokes.
	Diesel engine pistons	Clearance between the piston and its cylinder wall must be kept small. This is done by piston rings - expandable metal rings held in grooves in the side of the piston.

Engine characteristics	Engine output	Engine output refers to the torque and power produced by an engine.
	Power range	The power range of an engine can be described by its 'load factor' which gives its load and speed as an average.

Topic group	Topic	Summary