Quote:
Originally Posted by Daox
I have read a bit about how hydrogen effects combustion. I am aware that it increases flame speed, and is thus a great candidate to pair with lean burn to speed things back up and extend lean burn to even higher air/fuel ratios. I have yet to see someone actually put these two together in a car and run it though. There is also the issue with producing hydrogen onboard efficiently which I haven't seen addressed... ever. I'd like to see someone give it a shot though. If paired with variable compression, you'd have an amazing combo.
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. . . to affect combustion in the classical way. You are absolutely correct that we will not be able to efficiently produce it via on board electrolysis. But, as a seeding ingredient to affect the chemical kinetics, it can be effective. Studies on HCCI often use mixtures of hydrocarbons and hydrogen so that the chemical kinetics can be varied via fuel mix. Those studies use AFRs so lean, neither of the fuels should be able to burn when viewed in the classic sense, either individually or together. Both fall below the combustibility limits. But, when heat, pressure and turbulence are included into the equation, they detonate.
I include HHO in the discussion only because I would like to have an investigated answer for folks who drop in and ask. However, I surmise that it won't be needed in the end. Heat, turbulence, vaporization (added enthalpy) and pressure will be enough. And the turbo charger acts like a variable compression device. Oil Pan had a good discussion of that a long while back.
https://www.academia.edu/8209167/Basics_of_HCCI_engine
Here is a link that I hope allows a direct view of the presentation slides for HCCI. There isn't much discussion but the graphs give copious information. Especially telling is the pressure rise and ignition delay. If we could build an engine with "near HCCI" conditions, I propose the start of ignition via a spark would soon (micro seconds) incite ignition in the rest of the combustion chamber leading to rapid pressure rise. That is development further down the road, but I think iveyjh and pgfpro are closer than I am to answering the question.