It's all about the FUEL

General engine tech -- Drag Racing to Circle Track

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dannobee
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Re: It's all about the FUEL

Post by dannobee »

Talk to some of the old timers about hydrazine. It's banned everywhere because it's so dangerous. Not only physiologically but even leaving it in the fuel tank too long after the run can cause it to spontaneously combust. You'd likely face a lifetime ban if anything bad happened.

But as long as we're dreaming of hypothetical fuels, why not a nitromethane and hydrazine with liquid oxygen direct injection engine? You wouldn't even need to waste money on things like intake manifolds or blowers, or even ignition systems for that matter. Just put an exhaust port in the bottom of the cylinder, like a two-stroke.
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Re: It's all about the FUEL

Post by ptuomov »

It’d likely be a short ban!
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Re: It's all about the FUEL

Post by RDY4WAR »

The fuel is where the power is made so long as you can burn it. That's the part some people struggle with.

I've wondered about blending 1 gallon of VP Nitro 50-50 with 9 gallons of 93 non-ethanol pump fuel to get something like this.

BTU/lb of air
Gasoline = 1274
Methanol = 1328
Nitromethane = 2049

Stoichiometric Air/Fuel Ratio
Gasoline = 14.7
Methanol = 6.47
Nitromethane = 1.70

Specific Gravity
Gasoline = 0.745
Methanol = 0.795
Nitromethane = 1.139

Blend Ratio
Gasoline = 90%
Methanol = 5%
Nitromethane = 5%

Oxygen Content
Gasoline = 0%
Methanol = 49%
Nitromethane = 52%

Ballpark Blended Properties
Btu/lb of air = 1316
Stoich AFR = 13.64
Specific Gravity = 0.767
Oxygen Content = 5%
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Re: It's all about the FUEL

Post by ptuomov »

dannobee wrote: Mon Sep 27, 2021 11:40 pm But as long as we're dreaming of hypothetical fuels, why not a nitromethane and hydrazine with liquid oxygen direct injection engine? You wouldn't even need to waste money on things like intake manifolds or blowers, or even ignition systems for that matter. Just put an exhaust port in the bottom of the cylinder, like a two-stroke.
Liquid oxygen and liquid hydrogen would need big and heavy insulated tanks that are continuously cooled.

One of the methyl hydrazines and some sort of liquid nitrous oxide would be easier to store onboard a car. Say Dinitrogen Tetroxide (which autocorrect for some reason capitalizes) is a liquid under 21C. Both those bipropellants are also stable enough to be stored in a rocket, have acceptable ignition delay for many purposes, and might burn fast enough for internal combustion engine.
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Re: It's all about the FUEL

Post by David Redszus »

The heat energy of a fuel is not the sole determinant of power production.

The rate of heat release is an important parameter to consider.

Most hydrocarbon fuels release heat energy relatively slowly; a process called deflagration.

But exotic monopropellants have a much higher heat release rate; called detonation.

The difference is typically from 600 m/s up to 7800-10,000 m/s.

No internal combustion engine can withstand heat release rates in the supersonic speed range.
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Re: It's all about the FUEL

Post by hoodeng »

In the nineties before it was banned the go to combustion assistant for nitro was propylene oxide, if you though your fuel needed a little help getting its fire lit, this stuff would add that little extra snap crackle and pop. You could hear an engine running this stuff a mile off, it would jump into life with a distinct crack, much like parts wanting to jump out of their enclosure.

One fact about a nitro Harley is that each cylinder only fires roughly 350 times in a pass. I did the calculation some time back as to how many cc's of fuel was in the cylinder each time it fired, can't remember off hand now but it's a lot, a real lot!

Another point about richness in an mechanically injected engine is the pumps displacement, there were two fuel Harley's running in the nineties that had the same displacement, same layout, similar in a lot of ways but were tuned quite differently, one was built with a dash 0 pump the other a dash 1, it was the one with the dash 0 that ran with the reversed main can, only thing i can think of why it did not fall over was that the pump fitted was only just providing enough fuel with little going through the bypass at line pressure, if it had a dash 1 it would have hosed the cylinders.

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Re: It's all about the FUEL

Post by dannobee »

Top Fuel demo at Pomona. Just a wee bit more fuel than your dad's Oldsmobile.

https://www.youtube.com/watch?v=xGTbQuhhluY
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Re: It's all about the FUEL

Post by ptuomov »

David Redszus wrote: Tue Sep 28, 2021 3:14 pm The heat energy of a fuel is not the sole determinant of power production.

The rate of heat release is an important parameter to consider.

Most hydrocarbon fuels release heat energy relatively slowly; a process called deflagration.

But exotic monopropellants have a much higher heat release rate; called detonation.

The difference is typically from 600 m/s up to 7800-10,000 m/s.

No internal combustion engine can withstand heat release rates in the supersonic speed range.
Ok, I’ll bite. Is the benchmark here about stoichiometric homogenous gaseous gasoline air mixture? Because that burns pretty fast.
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Re: It's all about the FUEL

Post by ptuomov »

How about running E85 and tuning the fuel mixture for the car to be appropriate for E85? That’s somewhat available at pump right now. Then, when one wants extra power, blend in both high octane racing gasoline and nitromethane or nitropropane. Nitromethane should blend with ethanol in E85 and nitropropane should blend with gasoline in E85. Adding both nitro* and gasoline will have offsetting effects on stoichiometric AFR, so I’m thinking that picking the proportions right should allow one to maintain the AFR tuned for E85. Higher octane of the racing gasoline should help with higher cylinder pressures. Would this work?
RDY4WAR wrote: Tue Sep 28, 2021 7:34 am The fuel is where the power is made so long as you can burn it. That's the part some people struggle with.

I've wondered about blending 1 gallon of VP Nitro 50-50 with 9 gallons of 93 non-ethanol pump fuel to get something like this.

BTU/lb of air
Gasoline = 1274
Methanol = 1328
Nitromethane = 2049

Stoichiometric Air/Fuel Ratio
Gasoline = 14.7
Methanol = 6.47
Nitromethane = 1.70

Specific Gravity
Gasoline = 0.745
Methanol = 0.795
Nitromethane = 1.139

Blend Ratio
Gasoline = 90%
Methanol = 5%
Nitromethane = 5%

Oxygen Content
Gasoline = 0%
Methanol = 49%
Nitromethane = 52%

Ballpark Blended Properties
Btu/lb of air = 1316
Stoich AFR = 13.64
Specific Gravity = 0.767
Oxygen Content = 5%
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Re: It's all about the FUEL

Post by David Redszus »

Hydrocarbon vapor fuel mixtures have a deflagration velocity of about 1400-1800 m/s,
similar to sonic velocities at elevated temperatures.
That is not the same as flame propagation or laminar flame speed, which is much slower.

Detonation velocities of exotics are 5 to 7 times faster than deflagration velocities.

Nitropropane is not useful as a race fuel, unlike nitromethane. Nitropropane has
the same specific energy as gasoline.

Useful, but dangerous, additives are propylene oxide and ethylene oxide. Both banned.

For an insight to the use of nitromethane as a race fuel see SAE 852130, by Germaine.

Years ago, John Copeland did a study involving the performance of various additives,
in various amounts, called The question of race fuels.???
His conclusion was that small amounts of additives had little effect on performance.
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Re: It's all about the FUEL

Post by ptuomov »

“Nitropropane is not useful as a race fuel, unlike nitromethane. Nitropropane has the same specific energy as gasoline.“

Per unit of air ingested by the engine? I’m talking about an air limited engine. Nitropropane brings its own oxygen.
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Re: It's all about the FUEL

Post by RDY4WAR »

This engine is rather air limited. Stock heads, valves, intake, and cam. Heads flow ~205/145 and cam is just 202/207 @ .050". It needs all the help it can get.

I hadn't considered blending nitromethane with E85. That would be interesting. In either case, would 5-10% nitromethane make any substantial difference worth the hassle of handling the mess?
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Re: It's all about the FUEL

Post by ptuomov »

I don’t know about the power increase. Smarter people can answer that question.

My idea was simply to start with E85 and then add both racing gasoline and nitro in the right proportions in a way that allows one to keep the same carb jetting / fuel injector maps. Wonder if that would work?
RDY4WAR wrote: Wed Sep 29, 2021 3:39 pm This engine is rather air limited. Stock heads, valves, intake, and cam. Heads flow ~205/145 and cam is just 202/207 @ .050". It needs all the help it can get.

I hadn't considered blending nitromethane with E85. That would be interesting. In either case, would 5-10% nitromethane make any substantial difference worth the hassle of handling the mess?
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Re: It's all about the FUEL

Post by hoodeng »

RDY4WAR wrote: Wed Sep 29, 2021 3:39 pm This engine is rather air limited. Stock heads, valves, intake, and cam. Heads flow ~205/145 and cam is just 202/207 @ .050". It needs all the help it can get.

I hadn't considered blending nitromethane with E85. That would be interesting. In either case, would 5-10% nitromethane make any substantial difference worth the hassle of handling the mess?

5-10% will not do much but will do something, it might smell nice. Over 40-50% should start pushing parts around.

The trouble with nitro is keeping the concentrations at the required level, it is heavily influenced by ambient temp when new batches are mixed, just chucking in a percentage by volume or weight will get you into a whole new mess. Nitromethane % is a completely separate tuning area.

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Re: It's all about the FUEL

Post by David Redszus »

ptuomov wrote: Wed Sep 29, 2021 11:30 am “Nitropropane is not useful as a race fuel, unlike nitromethane. Nitropropane has the same specific energy as gasoline.“

Per unit of air ingested by the engine? I’m talking about an air limited engine. Nitropropane brings its own oxygen.
Nitropropane has an oxygen content of 36%, very similar to ethanol at 34.7%.
It is not a monopropellant; nitropropane stoich = 5.8, ethanol stoich = 6.4.

Nitromethane is often used with methanol as a co-solvent. A mixture of 20% nitromethane in methanol will increase power by approx 20%. The power output will increase in proportion to the percentage of nitromethane that is used.

Nitropropane is sometimes used in place of methanol as a co-solvent for nitromethane; while no improvement in power results, the knock limit is somewhat raised, allowing a higher compression ratio to be used.
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