Water washing and MPG?

[Tony]

This may be a complete idiot moment, but after Amber's death we were donated quite a quantity of biodiesel by VOD members and members here so that I wouldn't have to spend time worrying about making fuel instead of time with the family.  And to date, I've run on nothing but that - thank you guys.

I have a feeling, which may be totally unsubstantiated, that the washed bio has given greater MPG than the settled bio.  Of course, this may be because different feedstocks were used, but it has got me wondering if there could be a correlation?

[dgs]

This is certainly a good question Tony, but I can't see that the water washing could make any difference. Even if we assume that a very small amount of methanol, glycerol and soap could be left in settled bio, these
would be so small they could be regarded as insignificant as far as MPG is concerned.

Just my thoughts.

[Julian]

There might be some truth in that, the idea's been around for many years.

My first job was with a marine equipment supplier.  They tried some experiments in connection with one of the universitys to emulsify marine diesel.  They also ran tests on big diesel gensets.

I was involved in the tests at a high security radar base looking out for incoming Soviet missiles!  All seemed a bit OTT, but these massive gensets had to run 24/7 without fail and at an outrageous cost ... because they didn't trust the integrity of the grid!

Anyhow, they were getting proven fuel savings with between 2 and 5% water (I had one old diesel in the factory running on 15% ... didn't run well at all, but it ran!).  What put the dampers on the idea were reports of bugs in the water creating acid which, in dead spots in the fuel system, ate components.

Also, Spitfires were supposed to be fitted with water injection to catch V2s during the war ... don't know how true that was.

[Tony]

Might be true actually - check this:

http://www.spitfire.dk/motorer_eng.htm

"In 1944 150-octane fuel was used and water injection was fitted on a Merlin and that gave an output of 2,640 hp at 36 lbs. manifold pressure."

On a diesel related note I'm sure we found some "fuel booster" years back on VOD that really was just mostly water and some cunning chemicals to keep it miscible with oil-based fuels.

[Julian]

Did it contain platinum in some form?

[dgs]

Does this mean I shouldn't be drying my bio as much. My finished bio is usually <150ppm.

[Julian]

Given that bio costs us next to nothing, on balance, I recon drying thoroughly is the way to go.  But I have wondered if it's really necessary given the experiments I was involved in.

I guess it wouldn't be too difficult to test.  A couple of tanks of damp bio compared to a couple of dry and accurately clock the MPG.

I think it was only speculation because I can't see how they would know for sure, but the theory put forward by the university was that the fuel coated minuscule drops of water which, under heat of the cylinder, flashed to steam and further atomised the fuel.

In the case of the Spitfire, if the water was injected into the manifold, I wonder if it had more to do with cooling the incoming air rather than directly aiding combustion.

[Bio-boy]

Water injection is usually utilised to prevent the onset of detonation/knock. It is often used in conjunction with a turbo/supercharger with the addition of water enabling higher boost pressures to be used and increased performance. Water injection alone will not affect performance it is simply an enabler that in conjunction with other supporting modifications will provide improved performance.

[Tony]

I suspect water injection via the air inlet/cylinder head is preferable to water present in fuel where it can corrode high tolerance injection equipment.

Presumably it works because heat energy is extracted from combustion in flashing water to steam which then gets converted into energy in the piston stroke, making the overall extraction of energy from combustion more efficient?

[dgs]

I was just thinking about your !st post Tony (I sometimes do this, it's a bit of a weakness) The water present in the bio is probably the reverse of what we think. The water washers amongst us dry our fuel for obvious reasons wheras most of the de-meth and settlers don't. The latter finishing method usually is @ 600ppm water and dried bio after water washing is probably around the 400ppm.

Probably nothing to do with it but just a thought.

[Tony]

What processes result in those figures? I would like to think my settled bio is pretty dry!

[therecklessengineer]

Presumably it works because heat energy is extracted from combustion in flashing water to steam which then gets converted into energy in the piston stroke, making the overall extraction of energy from combustion more efficient?

This sounds wrong to me.

The amount of work done by the piston is determined by the mean effective pressure (https://en.wikipedia.org/wiki/Mean_effective_pressure, which in turn is determined by the peak pressure (Pmax), the timing, and cylinder dimensions.

If water is in the fuel then it will absorb energy in the cylinder, reducing the maximum temperature and thus Pmax (ideal gas law). You'd then see a drop in power output.

If this is the opposite of what's observed then there must be some other effect going on.

[dgs]

What processes result in those figures? I would like to think my settled bio is pretty dry!

From tests I have done on settled bio it is never within specification ie <500ppm On the few occaisions I have done this method the water remains at the 550 to 600ppm range so it still needs drying. I realise that most that de-meth and settle assume that just because no water has been added then the resultant bio will be dry enough, but it isn't.

[Keef]

I was of the opinion that water injection benefited the performance by cooling the air and making it more dense with a side effect of keeping the engine internals free from carbon deposits, therefor more efficient.


I haven't dried my fuel (wvo) in any way for years now and have never noticed any negative effects and always get pretty good mpg


Well, I consider 35mpg from an old Transit doing about 50% 70mph motorway work pretty good.


I would agree that water injection is preferable to water in the fuel though but who knows, maybe a controlled amount in the fuel may be beneficial.

[therecklessengineer]

These guys seem to be into water in fuel: http://www.quadrisefuels.com/

I've known about them for a while. I haven't yet worked out whether it's an elaborate con or not. I've never met anyone who's actually used their fuel.