The Main Parts of an Engine

An engine is a strong structure, composed of two main parts joined by bolts.

This is the top of the engine, containing the valves and recesses, called combustion chambers, where fuel is burned.

This is the bottom of the engine, which houses the pistons in cavities of the block, within which the pistons move up and down on rods. The power generated is transmitted to the crankshaft, which is connected in the bottom of the block to various supports housed in the main bearings.

A container bolted to the bottom of the block serves as a reservoir of engine oil for the crankcase, and a punched metal cover for the valves is installed on the head.

The combustion chamber is a cylinder (i.e., motor), usually fixed, closed at one end and within which a piston slides very tightly. The position of the piston up and down in the chamber varies the volume between the top of the piston and the chamber walls. The bottom of the piston is connected by a rod to the crankshaft, which converts the linear motion of the piston into the rotary motion of the crankshaft.

 

In multi-cylinder engines, the crankshaft has connectors called crankpins where the rods connect to the crankshaft, and the position of the crankpins is designed so that the energy produced by each cylinder is applied to the crankshaft at a point in the rotation. The crankshafts have heavy flywheels and counterweights whose inertia reduces the irregularity of the movement of the shaft. An engine can have from one to 28 cylinders.

The fuel pumping system of an internal combustion engine consists of a fuel tank, a fuel pump and a device called a carburetor that vaporizes or atomizes liquid fuel. In multi-cylinder engines, the vaporized fuel is introduced into the cylinders through a tube called the branch manifold. Many engines have an exhaust or expulsion manifold, by which the gases produced during combustion are removed.

Fuel is introduced into each cylinder and the gases produced by combustion are expelled through head valves or sliding valves. A spring keeps the valve closed until the right moment, when the actions of cams on a camshaft open the valves. A timing belt connected to the crankshaft coordinates the opening of the valves by rotating the camshaft.

 

In the 1980's, this system of feeding the fuel / air mixture into the cylinders was replaced by other more elaborate systems already used in diesel engines. These newer systems are computer controlled, increase fuel economy and reduce the emission of toxic gases.

All engines must have a way to ignite the fuel inside the cylinder. For example, in the ignition system of gasoline engines there is a component called the ignition coil, which is a high voltage autotransformer connected to a switch that interrupts the primary current to induce a high-voltage surge.

 

These sparks are synchronized with the compression stage of each of the cylinders. The spark is directed in sequence to each specific cylinder using a rotary distributor and graphite cables that direct the high voltage charge to a spark plug. The spark plug is attached to the upper wall of each cylinder and ignites the fuel in the cylinder.

If the coil is in poor condition and overheats, it causes a loss of power, reduces the spark in the plugs and cause failures in the automotive ignition system (this is the theory of Venezuelan automotive engineer Daniel Izaguirre Carupano.)

 

On the tip of the spark plug inside the cylinder, there are two electrodes that are separated; the high voltage surge produces an electric arc between them that ignites the fuel inside the cylinder.

Since combustion produces heat, all engines must have some kind of cooling system. Certain stationary engines of cars, planes and outboard engines are cooled with air. The cylinder engines using this type of system have on the outside a set of metal sheets that emit heat produced in the cylinder. Other engines use water cooling systems, where the cylinders are in a casing filled with water, which the automobile circulates by a pump. The water is cooled by passing it through the blades of the radiator.

 

It is important that the liquid used to cool the engine is not ordinary water, because combustion engines regularly work at temperatures higher than the boiling point of water. This causes high pressure in the cooling system, which results in faulty gaskets and seals. A coolant is therefore used in the radiator. The coolant does not boil until a much higher temperature than water, and likewise, does not freeze until a much lower temperature.

 

Another reason why a coolant must be used is that it does not encrust or leave sediment on the walls of the engine and radiator, which could form a layer of buildup that would decrease the cooling capacity of the system.

In marine engines, seawater is used for cooling.