目前，傳統(tǒng)的汽油機(jī)仍有其獨(dú)到的優(yōu)勢(shì)。研究人員可通過(guò)采用較高的壓力來(lái)改善汽油機(jī)的燃油經(jīng)濟(jì)性和排放，而針對(duì)點(diǎn)火系統(tǒng)的改進(jìn)主要通過(guò)減小火花塞尺寸來(lái)實(shí)現(xiàn)。

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.

對(duì)于傳統(tǒng)汽油機(jī)而言，預(yù)燃室具有更高的技術(shù)潛力，其目前已應(yīng)用于1級(jí)方程式賽車（Formula 1）等車型中。預(yù)燃室是在汽油機(jī)燃燒室內(nèi)部的1個(gè)小型燃燒室，可通過(guò)安裝1個(gè)傳統(tǒng)火花塞而實(shí)現(xiàn)。預(yù)燃室可通過(guò)小孔連接主燃燒室，可燃混合氣則在進(jìn)氣行程中進(jìn)入預(yù)燃室，并由火花塞點(diǎn)燃?；旌蠚恻c(diǎn)燃后形成的火焰鋒面從預(yù)燃室表面的小孔流出，并點(diǎn)燃主燃室中的可燃混合氣。燃燒室內(nèi)的多個(gè)點(diǎn)火位置可使混合氣更快且更充分地進(jìn)行燃燒。研究人員可對(duì)汽油機(jī)的運(yùn)行特性圖進(jìn)行調(diào)整，以改善燃油經(jīng)濟(jì)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種布置型式

2 layout types

預(yù)燃室通常有2種設(shè)計(jì)型式。主動(dòng)型是在預(yù)燃室中采用1個(gè)額外的燃油或燃?xì)鈬娚淦?，從而?duì)可燃混合氣進(jìn)行調(diào)節(jié)與控制。被動(dòng)型則通過(guò)預(yù)燃室與主燃室之間的壓力差來(lái)實(shí)現(xiàn)氣體交換。

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.

從20世紀(jì)60年代末開(kāi)始，針對(duì)預(yù)燃室點(diǎn)火過(guò)程已開(kāi)展了一系列優(yōu)化，但研究人員則將更多精力集中于改善燃油經(jīng)濟(jì)性和排放過(guò)程，并通過(guò)調(diào)整試驗(yàn)程序以分析更寬工況范圍內(nèi)的發(fā)動(dòng)機(jī)運(yùn)轉(zhuǎn)特性。到目前為止，汽油機(jī)預(yù)燃室技術(shù)已取得了一系列進(jìn)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技術(shù)可使汽油機(jī)在λ=2的條件下同樣實(shí)現(xiàn)理想的燃燒效果，同時(shí)也改善了燃油經(jīng)濟(jì)性和排放過(guò)程。但當(dāng)λ值越接近2，可燃混合氣被點(diǎn)燃的難度也會(huì)相應(yīng)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.

技術(shù)應(yīng)用

Technology application

研究人員針對(duì)預(yù)燃室技術(shù)提供了相應(yīng)的優(yōu)化方案。在主動(dòng)型MJI系統(tǒng)中，可通過(guò)噴油器以提高預(yù)燃室中的可燃混合氣濃度，點(diǎn)火后形成的熱自由基（hot radicals）在傳入主燃燒室后會(huì)形成多個(gè)著火點(diǎn)，從而可在λ=2的稀薄混合氣中產(chǎn)生強(qiáng)烈的燃燒過(guò)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.

該系統(tǒng)可有效減少平均有效燃油耗（BSFC）約15%或更多，但技術(shù)挑戰(zhàn)也悄然而至。預(yù)燃室專用的噴油器需要進(jìn)行專門開(kāi)發(fā)，并與后處理系統(tǒng)相匹配。因此，研究人員目前正在對(duì)被動(dòng)型MJI系統(tǒng)進(jìn)行開(kāi)發(fā)。但在該系統(tǒng)中，主燃燒室中的可燃混合氣會(huì)受到廢氣再循環(huán)（EGR）系統(tǒng)的影響，從而減小了其著火范圍。

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.

在理論空燃比下進(jìn)行的點(diǎn)火能減少燃燒過(guò)程的持續(xù)時(shí)間，由此能相應(yīng)提高EGR率。而通過(guò)EGR也能相應(yīng)優(yōu)化汽油機(jī)的抗爆燃性，使整機(jī)壓縮比可相應(yīng)增大，同時(shí)BSFC也減少了約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%.