Pushing the piston.

Ranger Mike

Thanks Doctor
Mopars RULE!!!

ehabulhaq

hey guys hi

actually i was reading your conversation and at the instant a question was generated in my mind!!!!and that was if hydrogen is burned in the piston what would be the temperature change inside it and how much pressure will its product-which is water- generate!!!!!!

anyone of u cud answer it!!!!!thanx

xxChrisxx

It depends on the ratio of Hydrogen to fuel, hydren to air and hydrogen and fuel to air. Fuel mixing is tricky and, to be honest I can't remember all of it.

I also have a New Years hang over,

Assuming enough air for full combustion of both fuel and H2,
The hydrogen will burn totally, but the overall power would be reduced and the temperature of the combustion would be reduced slightly also. There would be more water in the exhaust gas.

Assuming Octane.

C8H18 + 12.5(O2 +3.86N2) ----> 9H2O + 8CO2 + 48.25N2
add 2 mol H2 for enery mol fuel.

C8H18 + 13.5(O2 +3.86N2) + 2H2 ----> 11H2O + 8CO2 + 52.11N2
So for every mol of Hydrogen you add you need to add 1 mol of oxygen.

Basically adding H2 just dilutes the fuel, but doesn't make it run lean, as there is enough air for the pertrol to burn stoichiometrically and the h2 to burn stoich.



Assuming not enough Air for full combustion.
This case is what you get when you get people who try to run their car on water using little electrodes.

In this case, there is a set amount of fuel and air drawn in, but you are then dumping H2 in with it. This upsets the stiochiometric balance of the fuel, and the reason why they see marginal increases in fuel efficiency is that they are basically running the engine lean.

C8H18 + 12.5(O2 +3.86N2) + 2H2 ----> ??????????????

Becuase we don't know the composition of the exhaust (it will contain lots of crap due to oncomplete combustion of possibly both fuel and hydrogen).

Running lean long term will cause the temperature to increase, and it ends up ruining the piston, liners, block. (basically a whole manner of problems). It also means they are getting less power.

With incomplete combustion it's very hard to just work out an equation as the exhaust gas composition changes. You get unburnt fuel, carbon monoxide, NOx, and a whole manner of other crud.

ehabulhaq

ok all right i got it!!!!that was a good explanation!!!!
i had another question to ask that if say we electrolyse a dilute solution of NaCl which will give us hydrgen and oxygen in 2:1!!!for this electrloysis i think using a car battery(which is 50-60 AMP) would be enough to produce sufficient amount of these gases!!!!
if we introduce these gases into the piston and close the air inlet valve(which will stop nitrogen to come in)the reaction will go as follows

H2+1/2O2------H2O

the reaction is exothermic which has an enthalpy change of -286kJ per mole of hydrogen!!!the specific heat capacity and latent heat of vapourisation of water and specific heat capacity of water vapours i suppose is not much high so i think the temperature rise would be great and enough for making those vapours to push the piston and drive a car of say 1000cc or 800cc!!!!!

am i correct or totally wrong????what do you say

brewnog

You're right in principle, but there are a few things you should consider:

Setting aside the practical difficulties of actually storing the required quantity of hydrogen needed for a useful vehicle (as you propose with an internal combustion engine), it burns horrendously; controlling detonation is a massive problem and you'd need to de-rate the engine by a very large amount to overcome this. Your 1000cc or 800cc engine may only produce a tenth the power it did while running on petrol.

I'm sure you also realise that hydrogen isn't a fuel in the sense that coal or oil are; we just don't have hydrogen lying around waiting to be used; and producing it from water requires a lot of energy (more, in fact, that you extract from burning it).

xxChrisxx

You can't run your can on H2 alone by electrolysing it at the source, you can't get out more energy than it took to split apart the water in the first place.

Also electrolysis is about 50-80% efficient in turning electrical to chemical energy. So even if you did hook up a jar of water to the battery youu would basically be running your car from the battery.

At some point im acutally going to do the energy cycle of the all the reaction to show whythis Hydrogen jar is just a massive scam. Time to find my chemistry textbooks.

dr dodge

you could liberate the hydrogen chemically, but I don't see any real advantage over plain old (well maybe not old) gasoline. You would get some expansion bonus out of the water, but the true killed in any reaction that produces water as the by product is the destruction of the oil in the crank case. the dirt late model wasted oil by the end of 2 weekends racing (methanol fuel) the oil looked like chocolate milk. not a benefit for long use.

dr

xxChrisxx

You could use Aluminium and water in the presence of a sodium hydroxide catalyst. The reason for looking to switch to hydrogen is that petrol is a non renewable commodity. H2 power is more long term. For the reasons you said, most methods of hydrogen are better suited to fuel cell usage.

dr dodge

what is the waste product of the caustic aluminum mix
probably cleaner to burn gas

dr

xxChrisxx

Aluminium hydroxide, a mineral found in Al ore. (edit:its been a while since I did chemistry, TO WIKI BATMAN)