July 12 2023

What is working principle of a car engine

Although Nudao's driver friend bought car and can drive it, he is not yet familiar with how some parts of car work. For example, some people do not know how an engine works. Then, principle of operation of a car engine, what is it? What is introduction of motor principle? Let's find out together.

How a car engine works

Although purely electric vehicles are currently being actively discussed, power of modern vehicles is still provided by internal combustion engines. The so-called internal combustion engine is that fuel and air are mixed inside engine, and thermal energy generated by combustion is converted into mechanical energy. An automobile engine consists of a cylinder, piston, connecting rod, crankshaft and so on. The piston moves in a straight line in cylinder, and crankshaft is driven through connecting rod.

Basic Engine Terms:

Top dead center-TDC, bottom dead center-BDC, piston stroke, crank radius, cylinder displacement, engine displacement, combustion chamber volume, total cylinder volume, compression ratio, etc.

How engine works

Typically, engines are four-stroke, and their principle of operation includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke.

In simple terms, an engine usually consists of two mechanisms and five systems. The two mechanisms are crank mechanism and gas distribution mechanism, and five systems are supply system, cooling system, lubrication system, ignition system and starting system. So, what are functions of these two institutions?

The crank mechanism is like movable levers, and objects can be pushed by swinging levers. On direct sport valve train, it acts like air ducts of entire engine. The engine also needs to breathe: it inhales air to burn fuel and must exhaust exhaust gases produced after fuel is burned. The trigger system of these five systems is equivalent to a trigger pistol, it will issue a command and engine will start. This is equivalent to human intestines and stomach, which is part used to power engine, and food here is also fuel. The ignition system is similar to a lighter. The fuel burns and sets engine in motion so that it starts to move.

The cooling system is similar to an air conditioner in a classroom. As engine runs, its temperature will get higher and higher. The lubrication system is equivalent to engine stepping on a banana peel so that engine can move more smoothly. People often say that engine is heart of car, so how does it work? Next, editor will introduce you to functional principle of engine. Let's take a gaming machine as an example, and engine workflow can be divided into four parts. The first is a short-term journey, i.e. fuel gas is mixed withi with air and then enters engine, which is equivalent to mixing rice and vegetables together when we eat bibimbap.

In this process, a combustible mixture will be formed, and these mixtures will be sucked into engine cylinder in preparation for next process. The next step is compression process. Compression is necessary so that combustible mixture burns quickly. It's like in a bus. When there are only ten people on bus, everyone is in no hurry. The speed of passengers getting off bus should be slower. The more passengers, faster everyone get off bus. A gas is made up of individual molecules. When mixture of fuel and air is compressed, gas molecules become very fast. Once ignited, they will burn intensely. The third process is called power stroke, it turns out that there is a plug on cylinder head, which is called a spark plug.

It can emit electrical sparks to ignite compressed mixture, and combustible mixture starts to burn and generate a lot of heat, which is equivalent to a bus full of passengers. As soon as arrival door opens, crowd runs out of car. At this time, everyone can be considered as a small molecule of gas. Moving at high speed, they generate energy that drives engine. The last process is called exhaust stroke. We know that fuel will produce a lot of exhaust gases after combustion. If they are not emitted from engine, engine cannot continue to run, so generation of exhaust gases is also a very important reference. In this process, most of exhaust gases generated by combustion are emitted, but a small part of exhaust gases still remains in combustion chamber, this part of exhaust gases is called residual exhaust gases.

The four processes presented today are simply working cycle of a gasoline engine. Only when engine continuously completes such an operating cycle can vehicle run normally and continuously.