Posted by harry on August 22, 2009, 6:35 pm
> Ulysses.
> > The first thing that pops into my mind is "how much energy does it take to
> > make the fuel?" I suppose it must be a net gain or nobody would bother
> > making their own bio-diesel. Personally I think it would be a good idea to
> > have a diesel engine on hand and the ability to make the fuel just in
> > case...
> From my understanding by corresponding with two fairly large users of
> this SVO-Gas system the process is normal agriculture, followed by
> pressing the oil from the seeds, mixing the oil with gasoline, and
> filtering the mixture through a centrifuge (diesel truck oil filter).
> I thinks there may be a difference in economy of scale for both yields
> and fuel usage between farm and home scales operations.
> But still, even if the yields were 50% of farm-scale or 50 gallon per
> acre for 2 acres and fuel usage was 10x of farm-scale or 5 gallon of
> fuel per acre, that still leaves 100 gallons for the cost of 10
> gallons of gasoline and no federal alcohol permits to produce home-
> scale ethanol.
> With the diesel's more efficient use of fuel, it would seem that it
> could equate to 200 hours NET engine use per year.
> Curbie
A modern petrol engine and a modern diesel aren't very different as
regards efficiency. It was the carburretor that f****d things up in
the past
Posted by Bruce Richmond on August 22, 2009, 11:02 pm
> > Ulysses.
> > > The first thing that pops into my mind is "how much energy does it take to
> > > make the fuel?" I suppose it must be a net gain or nobody would bother
> > > making their own bio-diesel. Personally I think it would be a good idea to
> > > have a diesel engine on hand and the ability to make the fuel just in
> > > case...
> > From my understanding by corresponding with two fairly large users of
> > this SVO-Gas system the process is normal agriculture, followed by
> > pressing the oil from the seeds, mixing the oil with gasoline, and
> > filtering the mixture through a centrifuge (diesel truck oil filter).
> > I thinks there may be a difference in economy of scale for both yields
> > and fuel usage between farm and home scales operations.
> > But still, even if the yields were 50% of farm-scale or 50 gallon per
> > acre for 2 acres and fuel usage was 10x of farm-scale or 5 gallon of
> > fuel per acre, that still leaves 100 gallons for the cost of 10
> > gallons of gasoline and no federal alcohol permits to produce home-
> > scale ethanol.
> > With the diesel's more efficient use of fuel, it would seem that it
> > could equate to 200 hours NET engine use per year.
> > Curbie
> A modern petrol engine and a modern diesel aren't very different as
> regards efficiency. It was the carburretor that f****d things up in
> the past- Hide quoted text -
> - Show quoted text -
Under light load conditions a diesel has a great advantage in that it
does not have to draw air in past a nearly closed throttle plate.
That saves it from doing a lot of work.
Another reason for the diesel's higher efficiency is its compression
ratio. I forget the formula for theoretical efficiency right now, but
CR was a major factor. In the days of old it wasn't unusual to find
diesels with 22:1 CRs compared to gasoline engines with 7:1. But
those high CRs required heavy parts to withstand the forces and
tempertures involved. Those heavy parts made for a heavier vehicle
and limited the working speed of the engine, restricting its power
output for a given size. Diesels also tended to have small bores and
long strokes so that they could achive those high CRs, which also
tended to limit their rpm capability.
Over the years CRs in diesels has dropped allowing them to be made
lighter and with bore to stroke ratios more like gasoline engines.
That has allowed them to rev higher and produce more hp for a given
engine weight. At the same time gasoline engines have gone to higher
CRs. This was allowed in part by better fuel mixture control from
fuel injection. Other major factors are better spark timing and
combustion chamber shapes that help avoid detonation.
So yes, the efficiency of the two as used in vehicles is closer than
it was. But if we are talking a stationary diesel running a generator
there's no reason to worry about the power to weight ration and skimp
on strength. Give it a high CR and let it chuff away at low rpm to
reduce internal losses.
Bruce
Posted by Frank on August 21, 2009, 12:18 pm
Curbie wrote:
> http://www.oilcrusher.5u.com/
>
> This guy grows sunflower seeds and processes them to make his own fuel
> for all his diesel tractors to run a large farm. He uses a screw press
> to squeeze the oil from the seeds, mixes 10 to 15% regular gasoline to
> a level set by a hydrometer to match the specific gravity of his home-
> made fuel to that of #2 diesel fuel (not quite sure how specific
> gravity equates to fuel volatility?) then runs it through a centrifuge
> to mix and filter it. Once the fuel is mixed and filtered he claims it
> does not settle or separate.
>
> I’d never heard of this notion before so I started digging through web-
> site pages for scam flags (give me your money) and couldn’t find any.
> He appears to be saying this works for me, and here’s how I do it. He
> claims to have run 25,000 gallons of this home-made fuel through his
> diesels without attributable problems.
>
> I did some research on standard diesel fuel, found basically three
> issues that diesel have to deal with in this area, volatility,
> viscosity, and lubricity.
>
> Volatility is needed to start "compression ignition" engines and to
> prevent compression-chamber carbon-buildup causing a rise in
> compression ratio and resulting in pre-ignition, knock, power-loss,
> and engine damage if not properly cared for.
>
> Viscosity (or lack thereof) is needed for fuel flow from the tank,
> through filters, and then through the injectors. ("cloud", "pour",
> "gel" or "wax" points)
>
> Lubricity is the fuel’s ability to contribute its designed part to the
> engine’s lubrication.
>
> It seems like this ides has the potential to solve a lot if
> transesterifed fuel issues?
>
> Has anyone else heard of anyone using this idea, or can punch some
> holes in it?
>
> Thanks,
>
> Curbie
Offhand, I can't see any fault with his reasoning. If he were in the
far south, he could probably avoid blending with gas but in Kansas,
where it can get cold, viscosity or gelling would be a problem in cold
weather with pure seed oils. He's also not paying fuel taxes.
I've seen biodiesel for sale at a gas station in PA for about the same
price as regular gas.
Posted by Curbie on August 21, 2009, 11:11 pm
Frank,
> Offhand, I can't see any fault with his reasoning. If he were in the
> far south, he could probably avoid blending with gas but in Kansas,
> where it can get cold, viscosity or gelling would be a problem in cold
> weather with pure seed oils. He's also not paying fuel taxes.
> I've seen biodiesel for sale at a gas station in PA for about the same
> price as regular gas.
There seems to be two issues going on here:
1) raising the viscosity of the fuel. (cold weather)
2) raising the volatility to completely burn glycerin and avoid
combustion-chamber carbon-buildup (a problem common to diesels running
with SVO).
The thing that has me confused with this, is that I would think that
once enough gasoline has been added to SVO to achieve proper
combustion, it seems that adding any more for to adjust for cold
weather viscosity would be risky for combustion?
Seems like there may be some here, but I just can't get my mind around
it yet?
Curbie
Posted by Bruce Richmond on August 22, 2009, 2:10 am
> Frank,
> > Offhand, I can't see any fault with his reasoning. If he were in the
> > far south, he could probably avoid blending with gas but in Kansas,
> > where it can get cold, viscosity or gelling would be a problem in cold
> > weather with pure seed oils. He's also not paying fuel taxes.
> > I've seen biodiesel for sale at a gas station in PA for about the same
> > price as regular gas.
> There seems to be two issues going on here:
> 1) raising the viscosity of the fuel. (cold weather)
> 2) raising the volatility to completely burn glycerin and avoid
> combustion-chamber carbon-buildup (a problem common to diesels running
> with SVO).
> The thing that has me confused with this, is that I would think that
> once enough gasoline has been added to SVO to achieve proper
> combustion, it seems that adding any more for to adjust for cold
> weather viscosity would be risky for combustion?
> Seems like there may be some here, but I just can't get my mind around
> it yet?
> Curbie
I'm just thinking out loud here so I may be way off but,
Thick heavy oils have long carbon chains. Gasoline has mostly shorter
carbon chains, is thinner and burns quicker. Could be that the
gasoline is not only adjusting the viscosity but also the burn rate/
temperture.
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> > The first thing that pops into my mind is "how much energy does it take to
> > make the fuel?" I suppose it must be a net gain or nobody would bother
> > making their own bio-diesel. Personally I think it would be a good idea to
> > have a diesel engine on hand and the ability to make the fuel just in
> > case...
> From my understanding by corresponding with two fairly large users of
> this SVO-Gas system the process is normal agriculture, followed by
> pressing the oil from the seeds, mixing the oil with gasoline, and
> filtering the mixture through a centrifuge (diesel truck oil filter).
> I thinks there may be a difference in economy of scale for both yields
> and fuel usage between farm and home scales operations.
> But still, even if the yields were 50% of farm-scale or 50 gallon per
> acre for 2 acres and fuel usage was 10x of farm-scale or 5 gallon of
> fuel per acre, that still leaves 100 gallons for the cost of 10
> gallons of gasoline and no federal alcohol permits to produce home-
> scale ethanol.
> With the diesel's more efficient use of fuel, it would seem that it
> could equate to 200 hours NET engine use per year.
> Curbie