Many researchers believe that because hydrogen fuel is prone to spontaneous combustion, the engine does not need to use the pre combustion chamber spark plug when burning hydrogen fuel, because this component will reduce the safety of hydrogen fuel combustion. However, the actual situation is just the opposite. In order to achieve the goal of zero emission, the hydrogen mixture is relatively thin and the mixture λ> 2.5。 Under this condition, the spontaneous combustion of hydrogen fuel will be significantly reduced, so its combustion speed will be reduced accordingly.

研究人员通过采用经优化设计的预燃室火花塞，改善了该类稀薄混合气的燃烧速度。与此相反，存在缺陷的预燃室火花塞在燃用氢燃料时会导致一系列技术弊端，从而降低了预燃室火花塞用于氢发动机的适用性。

The researchers improved the combustion speed of this kind of lean mixture by using the optimized pre combustion chamber spark plug. On the contrary, the defective precombustion chamber spark plug will lead to a series of technical disadvantages when burning hydrogen fuel, which reduces the applicability of precombustion chamber spark plug for hydrogen engine.

对应用预燃室火花塞的挑战在于所开发的预燃室火花塞必须能有效平衡发动机在燃用天然气和氢燃料时的所有目标冲突。设计这种火花塞的核心技术是预燃室的主动扫气过程。研究人员借助于1个可侧面贯穿预燃室的较长直孔，即可将新鲜混合气导入至电极间隙附近，在形成火焰束之前就使其在预燃室中进行充分燃烧。

The challenge for the application of precombustion chamber spark plugs is that the developed precombustion chamber spark plugs must be able to effectively balance all target conflicts when the engine burns natural gas and hydrogen fuel. The core technology of designing this spark plug is the active scavenging process of the precombustion chamber. With the help of a long straight hole that can pass through the precombustion chamber on the side, the researchers can introduce the fresh mixture near the electrode gap and fully burn it in the precombustion chamber before forming the flame beam.

同时，研究人员采用了CFD模拟软件来优化预燃室参数(预燃室几何学、容积、喷孔方向和其他参数)，以达到所期望的λ数值和流动速度。特别是使预燃室内的混合气浓度比主燃烧室内更稀，以便减小氢燃料自燃的倾向。缸内混合气必须有着较高的流动速度，以便使可燃混合气在燃烧时具有足够的冷却效果，同时防止天然气在250 mg/Nm3的浓度运行时导致的火焰熄灭。佳的预燃室设计可通过预燃室内的完全燃烧而产生强烈的火焰束，从而确保主燃烧室内的火焰传播过程更为迅速和均匀。

At the same time, the researchers used CFD simulation software to optimize the precombustion chamber parameters (precombustion chamber geometry, volume, orifice direction and other parameters) to achieve the desired results λ Numerical and flow velocity. In particular, the mixture concentration in the precombustion chamber is thinner than that in the main combustion chamber, so as to reduce the tendency of spontaneous combustion of hydrogen fuel. The mixture in the cylinder must have a high flow speed, so that the combustible mixture can have sufficient cooling effect during combustion, and prevent the flame extinction caused by the operation of natural gas at the concentration of 250 mg / Nm3. The good precombustion chamber design can produce a strong flame beam through the complete combustion in the precombustion chamber, so as to ensure that the flame propagation process in the main combustion chamber is more rapid and uniform.

由于发动机配备了气缸压力测量装置，因此研究人员更易于识别缸内的燃烧状况。图6示出了所有6个气缸使用标准火花塞和Prometheus预燃室火花塞时的燃烧压力数据。正如预计，后者的燃烧压力波动有所降低。据此就能证实发动机在燃用氢燃料时仍具有较高的工作能力。

Because the engine is equipped with a cylinder pressure measuring device, it is easier for researchers to identify the combustion conditions in the cylinder. Figure 6 shows the combustion pressure data for all six cylinders using standard spark plugs and Prometheus precombustion chamber spark plugs. As expected, the combustion pressure fluctuation of the latter is reduced. Therefore, it can be confirmed that the engine still has high working capacity when burning hydrogen fuel.

研究人员已通过天然气进行过相似的试验过程，并与原始设备制造商(OEM)生产的预燃室火花塞进行了比较。在采用了Prometheus预燃室火花塞后，缸内展现出较为稳定和迅速的燃烧过程，特别是在排放量为500 mg/Nm3的情况下运行时，整机效率提高了0.3%。

Researchers have conducted a similar test process with natural gas and compared it with the pre combustion chamber spark plugs produced by the original equipment manufacturer (OEM). After using Prometheus precombustion chamber spark plug, the cylinder shows a relatively stable and rapid combustion process, especially when the emission is 500 mg / Nm3, the overall efficiency is increased by 0.3%.

在排放量为250 mg/Nm3的情况下运行时，整机效率提高了0.4%，而且在排放量为200 mg/Nm3的情况下运行时，离爆燃极限的裕量进一步增大，使用天然气运行时的稀薄极限与此相似。研究人员在证实了Prometheus预燃室火花塞具有预期的工作能力之后，后续仍需要对其进行耐久性试验。

When the emission is 250 mg / Nm3, the efficiency of the whole machine is improved by 0.4%, and when the emission is 200 mg / Nm3, the margin from the deflagration limit is further increased. The rarefaction limit when using natural gas is similar. After the researchers confirmed that the Prometheus precombustion chamber spark plug has the expected working capacity, the durability test still needs to be carried out later.