hydrogen gas engine related research trends

However, after the BMW Hydrogen 7, it seems that there is no news of the hydrogen engine. But I believe that the research is still quietly continue, perhaps for technical reserves, or wait for the technical bottleneck of a breakthrough. Previously, I had learned about the cycle of hydrogen gas engine related research trends, it is worth to share with readers. Taking into account the hydrogen cylinder combustion is easy to form high-pressure high-temperature environment, this time, the air of oxygen and nitrogen will generate harmful nitrogen oxides. This reaction is difficult to avoid, that is to say, after hydrogen combustion products may not only water, not pollution-free. Therefore, in the academic community had proposed the "argon cycle" concept. Combustion with hydrogen is no longer a combination of oxygen and nitrogen, but a combination of oxygen and argon. Argon is an inert gas, do not participate in any reaction, naturally completely eliminate the formation of nitrogen oxides. After filtration, you can also continue to use the argon recovery, which is the "cycle" was intended.