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Internal Combustion Engine


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A semi-technical description of internal combustion engine basics with German translations interspersed. Designed for ESL university class.

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Internal Combustion Engine

  1. 1. Technical English for Native German Speakers How Internal Combustion Engines Work (Adapted by Harvey Utech from “How Stuff Works”, German translations of stems added by Utech The purpose of a gasoline-driven car engine is to convert (umwandeln) gasoline (Benzin) into motion (Bewegung) so that the car can move. Currently (zur Zeit), the easiest way to create motion from gasoline is to burn the gasoline inside an engine. Therefore, a car engine is called an internal combustion engine (Verbrennungsmotor)--combustion takes place internally. Two things to note: There is also such a thing as an external combustion engine. A steam engine (Dampfmaschine) in old-fashioned (altmodisch) trains and steamboats is the best example of an external combustion engine. The fuel (coal, wood, oil, whatever (was auch immer)) in a steam engine burns outside the engine to create steam (Wasserdampf), and the steam creates motion inside the engine. Internal combustion is a lot more efficient (less (weniger) fuel per mile) than external combustion, plus an internal combustion engine is a lot smaller than an equivalent external combustion engine. This explains why we don't see any cars from Ford and VW using steam engines. Let's look at the internal combustion process in more detail. Internal Combustion Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are: • Intake (Einlass) stroke • Compression stroke • Combustion (Verbrennung) stroke • Exhaust (Auspuff) stroke You can see in the figure that a device called a piston is connected to the crankshaft by a connecting rod. As the crankshaft revolves (sich dreht), it has the effect of "resetting (neu einstellen) the cannon." Here is what happens as the engine goes through its cycle: 1. The piston starts at the top, the intake valve (Ventil) opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. This is the intake stroke. Only the tiniest (win- zigste) drop of gasoline needs to be mixed into the air for this to work. 2. Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful (kraftvoll). licensed under * Page 1 of 5
  2. 2. Technical English for Native German Speakers 3. When the piston reaches the top of its stroke, the spark plug emits a spark to ignite (anzünden) the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. 4. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe (Auspuffrohr). Now the engine is ready for the next cycle, so it takes in another charge of air and gas. Notice that the motion that comes out of an internal combustion engine is rotational (drehend), while the motion produced by the piston itself is linear [straight line]. In an engine, the linear motion of the pistons is converted into rotational motion by the connecting rod. The rotational motion is convenient because we plan to turn [rotate] the car's wheels with it anyway. Now let's look at all the parts that work together to make this happen, starting with the cylinders. Basic Engine Parts The core of the engine is the cylinder, with the piston moving up and down inside it. The engine described above has one cylinder. That is typical of most lawn mowers (Rasenmäher), 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 (waagerecht) opposed). Different configurations have different advantages (Vorteile) and disad- vantages (Nachteile) in terms of smoothness (Laufruhe), manufactur- ing cost and shape (Form) characteristics. These advantages and dis- advantages make them more suitable (geeignet) for certain vehicles (Fahrzeuge). Let's look at some key engine parts in more detail. 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 (in richtiger Art und Weise). 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 (Dichtung) between the outer edge (Flanke) of the piston and the inner edge of the cylinder. The rings serve two purposes: licensed under * Page 2 of 5
  3. 3. Technical English for Native German Speakers • They prevent (verhindern) the fuel/air mixture and exhaust in the combustion chamber from leaking (lecken) 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 1,000 miles 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 an old fashioned record player does. Sump The sump surrounds the crankshaft. It contains some amount of oil, which collects in the bottom of the sump (oil pan). Engine Valve Train and Ignition Systems Most engine subsystems can be implemented (realizieren) using differ- ent technologies (Technik), and better technologies can improve the performance of the engine. Let's look at all of the different subsystems used in modern engines, beginning with the valve train. The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes (Nocken) on it that move the valves up and down. Most modern engines have what are called overhead cams. This means that the camshaft is located above (über) the valves. The cams on the shaft activate the valves directly or through a very short linkage (Gestänge). Older engines used a camshaft located in the sump near the crankshaft. Rods linked the cam below to valve lifters above the valves. This approach has more moving parts and also causes more lag (Rückstand) between the cam's activation of the valve and the valve's subsequent (nachfolgend) motion. A timing belt or timing chain links the crankshaft to the camshaft so that the valves are in sync [= syn- chronization] with the pistons. The camshaft is geared (verzahnt) to turn at one-half the rate of the crankshaft. Many high-performance en- gines have four valves per cylinder (two for intake, two for exhaust), and this arrangement requires two camshafts per bank of cylinders, hence the phrase "dual overhead cams." The ignition system produces a high-voltage electrical charge and transmits (senden) it to the spark plugs via ignition wires. The charge first flows to a distributor, which you can easily find under the hood (Motorhaube) of most cars. The distributor has one wire going in the center and four, six, or eight wires (depending on the number of cylin- ders) coming out of it. These ignition wires send the charge to each spark plug. The engine is timed so that only one cylinder receives a licensed under * Page 3 of 5
  4. 4. Technical English for Native German Speakers spark from the distributor at a time. This approach provides maximum smoothness. We'll look at how your car's engine starts, cools and circulates air in the next section. Engine Cooling, Air-intake and Starting Systems The cooling system in most cars consists of (bestehen aus) the radiator (Kühler) and water pump. Water circulates through passages (Durch- lass) around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably the original Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled in- stead (You can tell an air-cooled engine by the fins (Lamelle) adorning the outside of each cylinder to help dissipate (ableiten) heat.). Air- cooling makes the engine lighter (leichter) but hotter, generally de- creasing engine life and overall performance. So now you know how and why your engine stays cool. But why is air circulation so important? Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed (gedrückt) into each cylinder) to increase performance (Leistung). The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the ex- haust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor. Increasing your engine's performance is great, but what exactly hap- pens when you turn the key to start it? The starting system consists of an electric starter motor and a starter solenoid (Magnetspule). When you turn the ignition (Zündung) 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 (Reibung) 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 (= amperes) of electricity must flow into the starter motor. The starter solenoid is essentially a large elec- tronic switch that can handle that much current. When you turn the ignition key, it activates the solenoid to power the motor. Engine Lubrication, Fuel, Exhaust and Electrical Sys- tems When it comes to day-to-day car maintenance, your first concern is probably the amount of gas in your car. How does the gas that you put in power the cylinders? The engine's fuel system pumps gas from the licensed under * Page 4 of 5
  5. 5. Technical English for Native German Speakers gas tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered (liefern) in three common ways: carburetion, port fuel injection and direct fuel injection. • In carburetion, a device called a carburetor (Vergaser) mixes gas into air as the air flows into the engine. • In a fuel-injected engine, the right amount of fuel is injected indi- vidually into each cylinder, either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection). Oil also plays an important part. The lubrication system makes sure that every moving part in the engine gets oil so that it can move easily. The two main parts needing oil are the pistons (so they can slide easily in their cylinders) and any bearings (Lager) that allow things like the crankshaft and camshaft to rotate freely. In most cars, oil is sucked out (aussaugen) of the oil pan by the oil pump, run through the oil filter to remove any grit (Sand), and then squirted (gespritzt) under high pres- sure onto bearings and the cylinder walls. The oil then trickles (hinun- terrieseln) down into the sump, where it is collected again and the cy- cle repeats. Now that you know about some of the stuff (Kram) that you put in your car, let's look at some of the stuff that comes out of it. The exhaust sys- tem includes the exhaust pipe and the muffler (Schalldämpfer). With- out a muffler, what you would hear is the sound of thousands of small explosions coming out your tailpipe. A muffler dampens (dämpen) the sound. The exhaust system also includes a catalytic converter. The emission control system in modern cars consists of a catalytic con- verter (Katalysator), a collection of sensors and actuators, and a com- puter to monitor (überwachen) and adjust (regulieren) everything. For example, the catalytic converter uses a catalyst and oxygen (Sauerstoff) to burn off any unused fuel and certain other chemicals in the exhaust. An oxygen sensor in the exhaust stream makes sure there is enough oxygen available (vorhanden) for the catalyst to work and adjusts things if necessary. Besides gas, what else powers your car? The electrical system consists of a battery and an alternator (Drehstromlichtmaschine). The alterna- tor is connected to the engine by a belt and generates electricity to re- charge the battery. The battery makes 12-volt power available to every- thing in the car needing electricity (the ignition system, radio, head- lights, windshield wipers, power windows and seats, computers, etc.) through the vehicle's wiring. licensed under * Page 5 of 5