As we mentioned earlier, igniting the Hydrogen with only compression heat is not easy. Here we will describe in a relatively simplified way how they have thought with this technology.

By using a so-called pre-injection, it has also been taken up in the models presented earlier. It can also be called pilot injection. For example, it can happen in this way: In the combustion chamber there is an injector that injects a small amount of a substance that ignites with the help of compression heat, for example diesel, it ignites and shortly afterwards the hydrogen is injected and ignited by the now burning diesel in the combustion chamber. However, in this theory there has been no information to explain how it works in reality with hydrogen. On the other hand, studies have been done with CNG, Compressed Natural Gas, which has a flammability similar to hydrogen.

Two injectors have been used, one for the diesel and one for the gas. Different angles of the injectors have had different effects. Even different pressures have had different meanings. Even in this model, they have tried injecting the gas at different times during the compression stroke and got different results from this. It has also been tried with combined injectors where the injector is designed so that both fuels are in one and the same injector.[1]

 

A setback that has emerged is that the pilot injection of diesel to start the combustion of the gas eventually builds up a layer of soot even though the amount of diesel is very small, but this problem will probably be reduced when the CNG is replaced by hydrogen, since CNG contains carbon.


[1](Dimitriou and Tsujimura, 2017)