In gasoline engine, when the mixture (air and fuel fully mixed) enters the combustion chamber in the intake stroke, the piston compresses it in the compression stroke. After the spark plug ignites the high-pressure mixture, the pressure generated by its combustion is converted into the power of engine operation.

发动机燃烧虽可以用三言两语简单的形容，但光是内燃机的燃烧研究，不知已造就了多少博、硕士论文，甚许多学者、工程师穷其一生都在研究燃烧的学问，所以要真正了解发动机，是要花很多工夫的。

Although engine combustion can be simply described in a few words, I don't know how many doctoral and master's theses have been produced in the combustion research of internal combustion engine alone. Even many scholars and engineers have spent their whole lives studying the knowledge of combustion. Therefore, it takes a lot of effort to really understand the engine.

右侧高压缩比设定，比较容易引起爆震，因此需要使用高辛烷值的燃油避免爆震

The setting of high compression ratio on the right side is easy to cause knock, so it is necessary to use fuel with high octane number to avoid knock

正是因为发动机的燃烧十分复杂，所以需要有相当精确的设计与控制，稍有一点控制失误或是失常，便会造成不正常燃烧，而“爆震”就是一种不正常燃烧。简单的说，爆震是不正常燃烧所导致的燃烧室内压力失常。

It is precisely because the combustion of the engine is very complex, so it needs to have quite accurate design and control. A little bit of control error or abnormality will cause abnormal combustion, and "knock" is a kind of abnormal combustion. In short, detonation is the abnormal pressure in combustion chamber caused by abnormal combustion.

造成爆震主要有以下几点原因：

The main reasons for knock are as follows:

一、点火角过于提前：

1、 Too early ignition angle:

为了使活塞在压缩上止点结束后，一进入动力冲程能立即获得动力，通常都会在活塞达到上止点前提前点火(因为从点火到完全燃烧需要一段时间)。而过于提早的点火会使得活塞还在压缩行程时，大部分油气已经燃烧，此时未燃烧的油气会承受极大的压力自燃，而造成爆震。

In order to make the piston obtain power immediately after entering the power stroke at the end of compression TDC, it is usually ignited in advance before the piston reaches TDC (because it takes a period of time from ignition to complete combustion). If the ignition is too early, most of the oil and gas will burn when the piston is still in the compression stroke. At this time, the unburned oil and gas will bear great pressure and spontaneously ignite, causing detonation.

二、发动机过度积碳：

2、 Excessive carbon deposition in engine:

发动机于燃烧室内过度积碳，除了会使压缩比增大(产生高压)，也会在积碳表面产生高温热点，使发动机爆震。

Excessive carbon deposition in the combustion chamber will not only increase the compression ratio (produce high pressure), but also produce high temperature hot spots on the surface of carbon deposition, which will make the engine knock.

三、发动机温度过高：

3、 Engine temperature too high:

发动机在太热的环境使得进气温度过高，或是发动机冷却水循环不良，都会造成发动机高温而爆震。

If the engine is too hot, the intake air temperature is too high, or the engine cooling water circulation is not good, it will cause the engine high temperature and knock.

四、空燃比不正确：

4、 Incorrect air fuel ratio:

过于稀的燃料空气混合比，会使得燃烧温度提升，而燃烧温度提高会造成发动机温度提升，当然容易爆震。

If the fuel air mixture ratio is too thin, the combustion temperature will increase, and the increase of combustion temperature will increase the engine temperature, which is easy to knock.

五、燃油辛烷值过低：

5、 Low octane number of fuel:

辛烷值是燃油抗爆震的指标，辛烷值越高，抗爆震性越强。压缩比高的发动机，燃烧室的压力较高，若是使用抗爆震性低的燃油，则容易发生爆震。

Octane number is an index of knock resistance of fuel. The higher the octane number is, the stronger the knock resistance is. The engine with high compression ratio has high pressure in combustion chamber. If the fuel with low shock resistance is used, it is easy to knock.