Автор работы: Пользователь скрыл имя, 29 Ноября 2013 в 00:02, реферат
Currently the necessity to have at least a dim idea about the functioning of your vehicle is becoming more and more actual. The following article is going to clarify some basic facts about the key-element of every car. In this resource, I'll cover the basic idea behind an engine and then go into detail about how all the pieces fit together. I’m going to describe not only the way engine works, but also mention its cooling system. In conclusion, I’ll also tell you about the basic components of an average car starting system.
Currently the necessity to have at least a dim idea about the functioning of your vehicle is becoming more and more actual. The following article is going to clarify some basic facts about the key-element of every car. In this resource, I'll cover the basic idea behind an engine and then go into detail about how all the pieces fit together. I’m going to describe not only the way engine works, but also mention its cooling system. In conclusion, I’ll also tell you about the basic components of an average car starting system.
The purpose of a petroleum car engine is to convert petroleum into motion so that your car can move. Currently the easiest way to create motion from petroleum is to burn the petroleum inside an engine. Therefore, a car engine is an internal combustion engine - combustion takes place internally.
Basic Engine Parts
The core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures.
Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles.
Spark plug
The spark plug supplies the spark that ignites the air/fuel mixture so that combustion can occur. The spark must happen at just the right moment for things to work properly.
Valves
The intake and exhaust valves open at the proper time to let in air and fuel and to let out exhaust.
Note that both valves are closed during compression and combustion so that the combustion chamber is sealed.
Piston
A piston is a cylindrical piece of metal that moves up and down inside the cylinder.
Piston rings
Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:
• They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.
• They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.
• Most cars that "burn oil" and have to have a quart added every 1,500 kilometres are burning it because the engine is old and the rings no longer seal things properly.
Connecting rod
The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.
Crankshaft
The crankshaft turns the piston's up and down motion into circular motion just like a crank on a jack-in-the-box does.
Sump
The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (the oil pan).
Engine Cooling, Starting Systems
The cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance.
Increasing your engine's performance is great, but what exactly happens when you turn the key to start it? The starting system consists of an electric starter motor and a starter solenoid. When you turn the ignition key, the starter motor spins the engine a few revolutions so that the combustion process can start. It takes a powerful motor to spin a cold engine. The starter motor must overcome:
• All of the internal friction caused by the piston rings
• The compression pressure of any cylinder(s) that happens to be in the compression stroke
• The energy needed to open and close valves with the camshaft
• All of the "other" things directly attached to the engine, like the water pump, oil pump, alternator, etc. Because so much energy is needed and because a car uses a 12-volt electrical system, hundreds of amps of electricity must flow into the starter motor. The starter solenoid is essentially a large electronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor.