Myth Busters SUCKS! (HHO mod, does it work?)

[tjts1]

Originally Posted by rmay635703

Mythbusters most certainly DOES SUCK, if you want real solid data. They are after all for entertainment, there are many times where they come to the blah blah blah... snore

I'm sorry what? I got bored and fell asleep before I could make it half way through your rubbish response.

[Frank Lee]

Easy now, nice tjts... ;P

[dcb]

Lol, it is kinda funny how Kari has become queen of the nerds.

[tangomar]

Originally Posted by chuckm

Until God repeals the laws of thermodynamics, I won't buy an on-board hydrogen generator system.
Let me offer this again: I'll help someone design a safe and effective way to meter in H2 from a bottle free of charge. If practical, I'll help you test the results. If it shows a net power output that is equal to more than the fuel value of the hydrogen (ie, hydrogen injected alongside gasoline), then I'd say you had something worthwhile. I'll even assign all rights to the design over to you.

There is no violations of the laws of thermodynamics. The total energy doesn't change. It is a matter of kinetics (time). This is taken from the document I indicated previously.

Listed are the basic constituents of modern pump gasoline, their vapor (boiling) points, and their burn times:
Petrochemical Vapor Point (degrees F. 1 BAR/2BAR) Burn Time
Hexane 156/199 <1 ms
Heptane 207/257
Octane 258/307
Nonane 303/350
Decane 345/400
Undecane 384/440
Dodecane 425/481 >33 ms

Consider a typical modern engine (2.0 liter with a 90mm stroke) at cruise conditions whereas the ignition event begins at approximately 30˚ BTDC. The 2% to 10% burn rate (the amount of time required for approximately 2% to 10% of the total air/fuel charge to be consumed by the combustion process) takes 16 to 17 Crank Angle Degrees (CAD).
This equates to 1.3 to 1.4 ms [(60 seconds / 2000 RPM)/360 degrees • CAD]. The 10% to 90% burn time takes another 80 CAD. This still is only another 6.6 ms. 80 + 17 CAD after spark event begins places the engine at approximately 67˚ ATDC in the combustion cycle. Considering the flame speed of gasoline is 41.5 cm/sec, and the piston will average a mean velocity of 180 cm/sec from TDC to BDC, with peak velocity around the 90˚ ATDC point of approximately 6666.67 cm/sec (6.7 m/s), it becomes easy to see
that the piston rapidly begins to outrun the pressure wave created by the expanding gasses activated by the thermal-to-mechanical conversion expansion pressure process.
It is so incredibly pronounced, even at cruise speeds, that the piston exceeds the typical speed of sound! Although pressure transducers may register positive (above ambient) pressure in and around the cylinder head within the combustion chamber, there would have to be a slight vacuum at the surface of the piston. This negates the possibility of the pressure within the cylinder to further contribute to useful work.
...
Even though as much as 90% of the fuel may be burned by 65˚ ATDC, the piston speed is already walking away from the pressure wave and rendering any Chemical-to-Thermal or Thermal-to-Pressure conversions ineffective in the engine (as far as productive work done). It therefore becomes evident that expediency in the rate of vaporization, initiation of combustion, completion of combustion, and conversion from thermal to pressure
energies are very time sensitive. The engine’s ability to harness “pressure” forces and convert them to kinetic energy occurs in a very small window of time limited to approximately 14˚ ATDC to about 30˚ ATDC (or 1.328 ms for our theoretical 2.0 liter engine at 2000 RPM).

Effectively, any fuel not vaporized and initiated in the combustion process early in the combustion cycle cannot contribute effectively in the conversion to kinetic energy at the crankshaft. Its contribution, if burned at all inside the engine, is simply thermal energy released to the coolant and exhaust systems.

...

Hydrogen has a flame speed more than five times greater than [gasoline]. Also, it has a lean limit (mixture at which flame will not propagate due to excess air) of φ = 0.1, much lower than the theoretical limit of gasoline (φ = 0.6). Theoretically, it is possible to extend the lean limit of the mixture, by adding a small amount of hydrogen to a liquid or gaseous hydrocarbon fuel. Operating with abundant excess air ensures more complete combustion, improves efficiency and results in a decrease in peak temperatures, which aids in lowering NOx, while eliminating problems commonly associated with operating on lean mixtures. Secondly, the higher flame speed increases the rate of combustion of the mixture and lowers cycle-to-cycle variations.
Hydrogen has a higher diffusivity compared to HC fuels, which improves mixing, enhances turbulence and increases homogeneity in the charge.

Thanks for reading.

[gone-ot]

...summary: using hydrogen gas as "kindling" for normal gasoline combustion with the intent of promoting more complete combustion sooner, without bumping into pre-combustion "pinging"?

[chuckm]

So, how efficient would an H2 enriched gasoline engine be? For the sake of easy math, let's say that you improved the thermal efficiency from 26.5% to 40% (about 50%, quite a feat!).

Let's say that your HHO generator is 60% efficient (that is, the energy utilized to make HHO versus the chemical energy of H2). And 60% is probably a extremely generous figure for a homemade underhood system with no active electrolyte control and cheap electrodes. (Some of the best industrial electolysers are running at ~80%. But please feel free to check my 60% figure here... there's a reason why >90% of the world's hydrogen production is accomplished by cracking fossil fuel rather than water.)

So, do you really think that the losses involved with producing HHO will be outweighed by the efficiency gains? The numbers above don't seem to give me much hope of that.

Again, I'll help someone design a bottle-based system. I've already figured out the control logic and most of the parts.

[some_other_dave]

Originally Posted by tangomar

... Operating with abundant excess air ensures more complete combustion, improves efficiency and results in a decrease in peak temperatures, which aids in lowering NOx, while eliminating problems commonly associated with operating on lean mixtures.

Wait--isn't "operating with abundant excess air" the very definition of a very lean mixture? Which is known to increase combustion temperatures, increasing NOx levels and causing other problems??

-soD

[chuckm]

Wait--isn't "operating with abundant excess air" the very definition of a very lean mixture? Which is known to increase combustion temperatures, increasing NOx levels and causing other problems??

It depends on just how lean you go. IIRC, past a certain point, exhaust temps and NOx go back down. Unfortunately, so does power.

[Nerys]

there are different LEVELS of what works. the E95 battery worked just fine. Don't see too many of them on the road. Good luck getting chevron to let you license it or buy them.

what intrigued me about the mythbusters episode and what REALLY made me mad that they did not go further with it.

THEY RAN A REGULAR ICE ENGINE ON PURE HYDROGEN GAS.

that instantly says one thing. all this HHO stuff DEFINATELY HAS MERIT !!

the issue was instantly settled for me. The issue is no longer does it work YES it works.

the issue is can an end user practically make it work within there means. IE can you make "ENOUGH" of the gas to make a difference at the gas pump.

Thats the issue now.

also generating HHO VIA the cars own power systems is plain silly. I consider any HHO setup that uses your cars battery or alternator to be instantly suspect and snakeoil. Period. your engine and your alternator are VERY INEFFICIENT the idea that you can use them to gain more power than you put in is just silly and flies in the face of the know laws of the universe.

Now if you want to put a battery pack in the trunk to run the HHO now we are getting somewhere. IF I ever have the time to actually build one of these things that is how I will do it.

[Frank Lee]

Hermie just invented HHO today too. Maybe if you guys get together and get it going you can show it at SEMA next year.