Dear Emmanuele Frasci

I hope this message finds you Emmanuele Frasci well! I wanted to reach out to discuss the density ratio between unburned and burned hydrogen mixtures (ρ_unburned / ρ_burned) as we dive deeper into hydrogen combustion analysis. As you Emmanuele Frasci know, hydrogen has a significantly lower molecular weight than conventional fuels like gasoline, which leads to some interesting dynamics during combustion.

When we look at the combustion products, hydrogen primarily produces water (H₂O), unlike gasoline, which generates both CO₂ and H₂O. This difference in combustion byproducts affects the overall density of the burned gases, and I’ve found that the density ratio for hydrogen typically ranges from 1.6 to 2.2. This is quite a bit lower than the 4 we see with gasoline, primarily due to the lighter molar mass of water vapor compared to carbon dioxide.

I’m curious to hear your thoughts on how changes in combustion conditions, such as pressure or temperature, might influence this density ratio and the overall combustion efficiency of hydrogen compared to traditional fuels. Your insights would be invaluable as we continue to explore this topic.

I found a relevant video for this answer

https://youtu.be/8juImpritRw?si=R6Mzx5P4HyQ2yOZy

Looking forward to your thoughts!

Dear Kaushik Shandilya,

Thanks for your very quick reply. I agree with you regarding the lower rho_unburned/rho_burned ratio for hydrogen combustion, if compared to gasoline combustion, also because an air-H2 mixture is characterized by a lower density than an air-gasoline mixture, given the very low density of hydrogen. Moreover, given the higher LHV of hydrogen, the combustion temperatures might be higher than the combustion of an air-gasoline combustion. Therefore, the burned mixture density is expected to be even lower in case of hydrogen combustion.

Please, make me know if my conclusions are convincing.

Best regards,

Emmanuele Frasci.