目前，传统的汽油机仍有其独到的优势。研究人员可通过采用较高的压力来改善汽油机的燃油经济性和排放，而针对点火系统的改进主要通过减小火花塞尺寸来实现。

At present, the traditional gasoline engine still has its unique advantages. Researchers can improve the fuel economy and emission of gasoline engine by using higher pressure, while the improvement of ignition system is mainly realized by reducing the size of spark plug.

对于传统汽油机而言，预燃室具有更高的技术潜力，其目前已应用于1级方程式赛车（Formula 1）等车型中。预燃室是在汽油机燃烧室内部的1个小型燃烧室，可通过安装1个传统火花塞而实现。预燃室可通过小孔连接主燃烧室，可燃混合气则在进气行程中进入预燃室，并由火花塞点燃。混合气点燃后形成的火焰锋面从预燃室表面的小孔流出，并点燃主燃室中的可燃混合气。燃烧室内的多个点火位置可使混合气更快且更充分地进行燃烧。研究人员可对汽油机的运行特性图进行调整，以改善燃油经济性和功率。

For traditional gasoline engines, the precombustion chamber has higher technical potential, which has been applied to models such as Formula 1. The precombustion chamber is a small combustion chamber inside the combustion chamber of gasoline engine, which can be realized by installing a traditional spark plug. The precombustion chamber can be connected to the main combustion chamber through a small hole, and the combustible mixture enters the precombustion chamber during the intake stroke and is ignited by the spark plug. The flame front formed after the mixture is ignited flows out of the small hole on the surface of the precombustion chamber and ignites the combustible mixture in the main combustion chamber. Multiple ignition positions in the combustion chamber enable the mixture to burn faster and more fully. Researchers can adjust the operating characteristic diagram of gasoline engine to improve fuel economy and power.

2种布置型式

2 layout types

预燃室通常有2种设计型式。主动型是在预燃室中采用1个额外的燃油或燃气喷射器，从而对可燃混合气进行调节与控制。被动型则通过预燃室与主燃室之间的压力差来实现气体交换。

There are usually two design types of precombustion chamber. The active type uses an additional fuel or gas injector in the precombustion chamber to regulate and control the combustible mixture. The passive type realizes gas exchange through the pressure difference between the precombustion chamber and the main combustion chamber.

从20世纪60年代末开始，针对预燃室点火过程已开展了一系列优化，但研究人员则将更多精力集中于改善燃油经济性和排放过程，并通过调整试验程序以分析更宽工况范围内的发动机运转特性。到目前为止，汽油机预燃室技术已取得了一系列进展。

Since the late 1960s, a series of optimization has been carried out for the ignition process of the precombustion chamber, but researchers have focused more on improving fuel economy and emission process, and analyzed the engine operating characteristics in a wider range of operating conditions by adjusting the test program. So far, a series of progress has been made in the technology of gasoline engine precombustion chamber.

MJI技术可使汽油机在λ=2的条件下同样实现理想的燃烧效果，同时也改善了燃油经济性和排放过程。但当λ值越接近2，可燃混合气被点燃的难度也会相应更高。

Mji technology enables gasoline engines to λ= 2, while improving fuel economy and emission process. But when λ The closer the value is to 2, the more difficult it is for the combustible mixture to be ignited.

技术应用

Technology application

研究人员针对预燃室技术提供了相应的优化方案。在主动型MJI系统中，可通过喷油器以提高预燃室中的可燃混合气浓度，点火后形成的热自由基（hot radicals）在传入主燃烧室后会形成多个着火点，从而可在λ=2的稀薄混合气中产生强烈的燃烧过程。

Researchers provide corresponding optimization schemes for precombustion chamber technology. In the active Mji system, the fuel injector can be used to increase the concentration of combustible mixture in the precombustion chamber. The hot radicals formed after ignition will form multiple ignition points after being introduced into the main combustion chamber λ= A strong combustion process occurs in the lean mixture of 2.

该系统可有效减少平均有效燃油耗（BSFC）约15%或更多，但技术挑战也悄然而至。预燃室专用的喷油器需要进行专门开发，并与后处理系统相匹配。因此，研究人员目前正在对被动型MJI系统进行开发。但在该系统中，主燃烧室中的可燃混合气会受到废气再循环（EGR）系统的影响，从而减小了其着火范围。

The system can effectively reduce the average effective fuel consumption (BSFC) by about 15% or more, but the technical challenge also comes quietly. The special fuel injector for the precombustion chamber needs to be specially developed and matched with the aftertreatment system. Therefore, researchers are currently developing a passive Mji system. However, in this system, the combustible mixture in the main combustion chamber will be affected by the exhaust gas recirculation (EGR) system, which reduces its ignition range.

在理论空燃比下进行的点火能减少燃烧过程的持续时间，由此能相应提高EGR率。而通过EGR也能相应优化汽油机的抗爆燃性，使整机压缩比可相应增大，同时BSFC也减少了约10%。

The ignition under the theoretical air-fuel ratio can reduce the duration of the combustion process, so as to improve the EGR rate accordingly. The anti deflagration performance of gasoline engine can also be optimized by EGR, so that the compression ratio of the whole engine can be increased, and the BSFC can be reduced by about 10%.