Look at the diagram and try to explain how the internal-combustion engine works. Use the words and phrases below.

fuel-injection system, carburetor, vehicle, to provide, fuel delivery system, electronic sensors, engine speeds, the ratio of fuel to air, fuel-injection nozzle, combustion chamber, mixture of fuel and air, to trigger ignition

READING

Read the text and match the questions (a-e) to the paragraphs (1-5).

1. What parts do Otto-cycle and diesel engines consist of?

2. Where are the different types of internal-combustion engines used?

3. What are the main parts of the ignition system of Otto-cycle engines?

4. Where are fuel and oxidizer burned in an internal-combustion engine?

5. How is fuel supplied in an internal-combustion engine?

INTERNAL-COMBUSTION ENGINES

1. While the steam engine remained dominant in industry and transportation during much of the 19th century, engineers and scientists began developing other sources and converters of energy. One of the most important of these was the internal-combustion engine. In such a device a fuel and oxidizer are burned within the engine and the products of combustion act directly on piston or rotor surfaces.

2. Four principal types of internal-combustion engines are in general use: the Otto-cycle engine, the diesel engine, the rotary engine, and the gas turbine. The Otto-cycle engine, named after its inventor, the German technician Nikolaus August Otto, is the familiar gasoline engine used in automobiles and airplanes; the diesel engine, named after the French-born German engineer Rudolf Christian Karl Diesel, operates on a different principle and usually uses oil as a fuel. It is employed in electric-generating and marine-power plants, in trucks and buses, and in some automobiles. Both Otto-cycle and diesel engines are manufactured in two-stroke and four-stroke cycle models.

3. The essential parts of Otto-cycle and diesel engines are the same. The combustion chamber consists of a cylinder, usually fixed, that is closed at one end and in which a close-fitting piston slides. The in-and-out motion of the piston varies the volume of the chamber between the inner face of the piston and the closed end of the cylinder. The outer face of the piston is attached to a crankshaft by a connecting rod. The crankshaft transforms the reciprocating motion of the piston into rotary motion. In multicylindered engines the crankshaft has one offset portion, called a crankpin, for each connecting rod, so that the power from each cylinder is applied to the crankshaft at the appropriate point in its rotation. Crankshafts have heavy flywheels and counterweights, which by their inertia minimize irregularity in the motion of the shaft. An engine may have from 1 to as many as 28 cylinders.

4. The fuel supply system of an internal-combustion engine consists of a tank, a fuel pump, and a device for vaporizing or atomizing the liquid fuel. In Otto-cycle engines this device is either a carburetor or, more recently, a fuel-injection system. In most engines with a carburetor, vaporized fuel is conveyed to the cylinders through a branched pipe called the intake manifold and, in many engines, a similar exhaust manifold is provided to carry off the gases produced by combustion. The fuel is admitted to each cylinder and the waste gases exhausted through mechanically operated poppet valves or sleeve valves. The valves are normally held closed by the pressure of springs and are opened at the proper time during the operating cycle by cams on a rotating camshaft that is geared to the crankshaft. By the 1980s more sophisticated fuel-injection systems, also used in diesel engines, had largely replaced this traditional method of supplying the proper mix of air and fuel. In engines with fuel injection, a mechanically or electronically controlled monitoring system injects the appropriate amount of gas directly into the cylinder or inlet valve at the appropriate time. The gas vaporizes as it enters the cylinder. This system is more fuel efficient than the carburetor and produces less pollution.

5. In all engines some means of igniting the fuel in the cylinder must be provided. For example, the ignition system of Otto-cycle engines described below consists of a source of low-voltage, direct-current electricity that is connected to the primary of a transformer called an ignition coil. The current is interrupted many times a second by an automatic switch called the timer. The pulsations of the current in the primary induce a pulsating, high-voltage current in the secondary. The high-voltage current is led to each cylinder in turn by a rotary switch called the distributor. The actual ignition device is the spark plug, an insulated conductor set in the wall or top of each cylinder. At the inner end of the spark plug is a small gap between two wires. The high-voltage current arcs across this gap, yielding the spark that ignites the fuel mixture in the cylinder.

From Encyclopædia Britannica

 

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