Basic knowledge of popular science automobile, number of cylinders, V/W engine structure, etc.


● 1 The number of cylinders cannot be too many

General cars are mostly four-cylinder and six-cylinder engines. Since the power of the engine is mainly derived from cylinders, is it better to have more cylinders? In fact, as the number of cylinders increases, the parts of the engine are also Correspondingly, the structure of the engine will be more complicated, which will also reduce the reliability of the engine, and will also increase the cost of engine manufacturing and subsequent maintenance costs. V12 engines, W12 engines and W16 engines are only used in a few high-performance cars.

● 2 V-type engine structure

In fact, a simple understanding of a V-type engine is to combine adjacent cylinders at a certain angle. From the side, it looks like a V-shape, which is a V-type engine. Compared with the in-line engine, the V-type engine has a reduced height and length, which can make the engine cover lower and meet the requirements of aerodynamics. The cylinders of the V-type engine are arranged oppositely at an angle, which can offset part of the vibration, but the disadvantage is that two cylinder heads must be used, and the structure is relatively complicated. Although the height of the engine is reduced, its width is also increased accordingly, so that it is not easy to install other devices for the engine compartment with a fixed space.

● 3 W type engine structure

Stagger the cylinders on both sides of the V-engine at a small angle, and it is a W-engine. Compared with the V-type engine, the W-type engine has the advantage that the crankshaft can be shorter and the weight can be lighter, but the width is correspondingly increased, and the engine compartment will be more full. The disadvantage is that the structure of the W-type engine is divided into two parts, the structure is more complicated, and it will produce a lot of vibration during operation, so it is only used in a few cars.

● 4 Horizontal opposed engine structure

The adjacent cylinders of the horizontally opposed engine are arranged opposite each other (the bottom of the piston faces the outside), and the angle between the two cylinders is 180°, but it is essentially different from the 180°V engine. The horizontally opposed engine is similar to the in-line engine in that it does not share a crank pin (that is, a piston is connected to only one crank pin), and the direction of movement of the opposed piston is opposite, but the 180°V engine is just the opposite. The advantage of the horizontally opposed engine is that it can well offset the vibration and make the engine run more smoothly; the center of gravity is low, and the front of the car can be designed lower to meet the requirements of aerodynamics; the direction of the power output shaft is consistent with the direction of the drive shaft, and the power is transmitted Higher efficiency. Disadvantages: complex structure, inconvenient maintenance; demanding production technology, high production cost, in well-known brands of cars, only Porsche and Subaru still insist on using horizontally opposed engines.

● 5 Why does the engine continuously provide power?

During compression stroke, the intake and exhaust valves are closed, and the piston moves from bottom dead center to top dead center to compress the mixed gas to the top of the cylinder to increase the temperature of the mixed gas and prepare for the work stroke.

In the work stroke, the spark plug ignites the compressed gas, and the mixed gas “explodes” in the cylinder to generate huge pressure, pushing the piston from the top dead center to the bottom dead center, and pushing the crankshaft to rotate through the connecting rod.

● 6 The engine power comes from the explosion

The engine’s ability to generate power is actually derived from the “explosive force” in the cylinder. In the combustion chamber of the sealed cylinder, the spark plug ignites a certain proportion of gasoline and air mixture at the right moment, which will produce a huge explosive force. The top of the combustion chamber is fixed, and the huge pressure forces the piston to move downward. , The crankshaft is pushed through the connecting rod, and the power is transmitted to the driving wheels through a series of mechanisms, and finally the car is pushed.

● 7 Spark plug is a master of “detonation”

In order for the “explosion” in the cylinder to be more powerful, timely ignition is very important, and the spark plug in the cylinder plays the role of “detonation”. In fact, the principle of spark plug ignition is somewhat similar to lightning. The head of the spark plug has a center electrode and a side electrode (as opposed to two clouds with ions of opposite polarity), and there is a small gap between the two electrodes (called the ignition gap). When energized, it can generate an electric spark of more than 10,000 volts, which can instantly “detonate” the mixed gas in the cylinder.

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