i was just researching some chemistry, and i got some interesting info. im going to disagree with what i said last week, but heres what ive got:
according to my chemistry book, octane, as well as most other HC's have a negative enthalpy of formation. in simple terms, that means their internal energy is less than that of elemental C and H. Naturally, they are less negative than CO2 and H2O, which is why burning them produces energy. Most of us know that anything in its elemental form has 0 internal energy, but what i just found is interesting. for carbon, it has zero energy as graphite, but when it has been broken from HC's, it exists as a gas, which has a VERY POSITIVE energy. Likewise, hydrogen has a zero value as H2, but when you rip individual H atoms off a molecule, they also have a VERY POSITIVE energy. if any of you want the actual numbers, just ask, but i dont want to bore everyone if you dont want it.
Therefore, if we do superheat our fuel to somewhere above where it decomposes into individual atoms, we get a heck of a lot more energy out of it! naturally, we would use exhaust(wasted energy) for this process. Until i have time to research what temp is required, i dont know if exhaust is even hot enough, but it looks good on paper!
the other thing i found, as someone asked about, fuel "cracking". according to my chemistry book, cracking is the process of changing a "straight" hydrocarbon into a "forked" hydrocarbon. oil refineries do this to raise the octane rating, according to my book, from about 50 up to where we can use it (around 90-ish).
my book even describes the process: the fuel is mixed with a catalyst (Al2O3 or SiO2), and then heated to only 400-500*C. This cracks some of the fuel as i described above, and breaks some of it into smaller HC's. And according to a different section of the book, the smaller HC's contain more energy, if you know what everything means. what i mean by that is that while the smaller HC's have smaller energy numbers, those are calculated per mole. if you convert that to energy per gram (or any other unit of mass), you find significantly more energy in the smaller HC's.
my example here is with smaller HC's so its easier to read:
CH4 (methane) has -74.8 KJ/mol, and
C4H10 (butane) has -147.6 KJ/mol
if you divide these numbers by the molecular mass, you find that
CH4 (methane) has -4.675 KJ/gram, and
C4H10 (butane) has -2.545 KJ/gram,
i wish my book had exact numbers on the bigger HC's, but if the trend follows (and theres no reason it wouldnt), we might tripple the fuel's internal energy if we crack it all the way down!
Which means that breaking into those smaller HC's gets a lot more out of your gallon of gas! so cracking the fuel on the road might do a lot for us if we can find a way to do it effectively!!
i dont know if the exhaust has enough energy flowing through it to do all this, but it might be worth a try!!
the other question we have to ask is if the fuel would detonate, instead of burn properly. if yes, then 3/4 of what i just told you is useless, but i really dont know.
Also, this kind of superheated fuel probably wouldnt be able to pass through the intake manifold without igniting, so it would have to be injected. If your engine is built for FI, thats as easy as replacing the injectors with something that accepts a vaporized fuel.
for those of you who arent bored to death yet, we all have a lot more to think about. if y'all have any more info, please post it so we can all think about it!
according to my chemistry book, octane, as well as most other HC's have a negative enthalpy of formation. in simple terms, that means their internal energy is less than that of elemental C and H. Naturally, they are less negative than CO2 and H2O, which is why burning them produces energy. Most of us know that anything in its elemental form has 0 internal energy, but what i just found is interesting. for carbon, it has zero energy as graphite, but when it has been broken from HC's, it exists as a gas, which has a VERY POSITIVE energy. Likewise, hydrogen has a zero value as H2, but when you rip individual H atoms off a molecule, they also have a VERY POSITIVE energy. if any of you want the actual numbers, just ask, but i dont want to bore everyone if you dont want it.
Therefore, if we do superheat our fuel to somewhere above where it decomposes into individual atoms, we get a heck of a lot more energy out of it! naturally, we would use exhaust(wasted energy) for this process. Until i have time to research what temp is required, i dont know if exhaust is even hot enough, but it looks good on paper!
the other thing i found, as someone asked about, fuel "cracking". according to my chemistry book, cracking is the process of changing a "straight" hydrocarbon into a "forked" hydrocarbon. oil refineries do this to raise the octane rating, according to my book, from about 50 up to where we can use it (around 90-ish).
my book even describes the process: the fuel is mixed with a catalyst (Al2O3 or SiO2), and then heated to only 400-500*C. This cracks some of the fuel as i described above, and breaks some of it into smaller HC's. And according to a different section of the book, the smaller HC's contain more energy, if you know what everything means. what i mean by that is that while the smaller HC's have smaller energy numbers, those are calculated per mole. if you convert that to energy per gram (or any other unit of mass), you find significantly more energy in the smaller HC's.
my example here is with smaller HC's so its easier to read:
CH4 (methane) has -74.8 KJ/mol, and
C4H10 (butane) has -147.6 KJ/mol
if you divide these numbers by the molecular mass, you find that
CH4 (methane) has -4.675 KJ/gram, and
C4H10 (butane) has -2.545 KJ/gram,
i wish my book had exact numbers on the bigger HC's, but if the trend follows (and theres no reason it wouldnt), we might tripple the fuel's internal energy if we crack it all the way down!
Which means that breaking into those smaller HC's gets a lot more out of your gallon of gas! so cracking the fuel on the road might do a lot for us if we can find a way to do it effectively!!
i dont know if the exhaust has enough energy flowing through it to do all this, but it might be worth a try!!
the other question we have to ask is if the fuel would detonate, instead of burn properly. if yes, then 3/4 of what i just told you is useless, but i really dont know.
Also, this kind of superheated fuel probably wouldnt be able to pass through the intake manifold without igniting, so it would have to be injected. If your engine is built for FI, thats as easy as replacing the injectors with something that accepts a vaporized fuel.
for those of you who arent bored to death yet, we all have a lot more to think about. if y'all have any more info, please post it so we can all think about it!
