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$10 gallon Avgas

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skydawg

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TEL It's also required to prolong valve seating surfaces, so any other additive would have to require that cushioning property
 

rbarnes

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I thought the lead in avgas had as much to do with lubrication of the valves as it does in boosting octane. Is this still true with aviation engines ?
Will these new fuels still address this ? ...... or what I just saw SkyDawg write after hitting the post reply button....
 

Patrickh99

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My understanding is that due to the higher octane & cooling effects of ethanol, engines specifically designed to run on it can be much more efficient, negating the lower BTU. One proposed engine design is similar to a diesel, with turbo-charging and very high compression ratios (15-25:1). The downside is it could never be run with anything but E100.
 

Doggzilla

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My understanding is that due to the higher octane & cooling effects of ethanol, engines specifically designed to run on it can be much more efficient, negating the lower BTU. One proposed engine design is similar to a diesel, with turbo-charging and very high compression ratios (15-25:1). The downside is it could never be run with anything but E100.
There are actually E85 ethanol engines that outperform diesel. A purpose built ethanol engine for aviation would be game changing.
 

Bigshu

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The ethanol density issue is actually very simple. It only takes 30% ethanol to boost regular gas to 98 octane. And it retains about 90% the total energy.

The proper mixture can be created by existing pumps automatically out of E10 and E85, which are also the cheapest and easiest to get.

With a 3 mixture pump the mid grade is simply a mixture of the low and high. So using E10 and E85 would produce a mid grade of E47.5. Which has very close to 100 octane. And about 85-90% the energy density.

So simply mixing existing fuels in an existing pump will produce a suitable fuel without any additional development or refining required.

Completely off the shelf and affordable.
Not sure where you find "mixture pumps" I work for a petroleum pipeline, and the only fuels that leave our facilities meet a specification, and are legal to sell as is. Regular, Mid-grade and Premium gasoline are all stored in their own underground tanks at gas stations, and there's no mixing at the pump. The mixing takes place at the terminals, and you can get whatever % blend that's offered by the suppliers. Most "gasohol" is either 10 or 15% ethanol, depending on the state mandates in place. High ethanol blends are typically used by municipalities, not often at retail outlets. There is a reduction in fuel economy as the ethanol % increases, which some people don't mind in trade for the octane improvement. Prium gasoline with 10% ethanol typically tests out at 93 octane. We find some retailer stations will offer ethanol free gasoline, but it's rare. Marinas prefer ethanol free fuels, as do small motors (like lawn mowers, etc).
 

Bigshu

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I thought the lead in avgas had as much to do with lubrication of the valves as it does in boosting octane. Is this still true with aviation engines ?
Will these new fuels still address this ? ...... or what I just saw SkyDawg write after hitting the post reply button....
Lead in Avgas is a tiny component of the fuel. When our facility stored avgas, it was a huge PITA, especially when it came time to service the tank, it's pumps, and piping. All components that leaded fuel touched had to be placarded as containing a known carcinogen, and the product QC testing required extra PPE.
 

TXFlyGuy

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Lead in Avgas is a tiny component of the fuel. When our facility stored avgas, it was a huge PITA, especially when it came time to service the tank, it's pumps, and piping. All components that leaded fuel touched had to be placarded as containing a known carcinogen, and the product QC testing required extra PPE.
And 100LL is not low lead at all. It contains four times the lead that premium Ethyl pump gas used to have.
 

Bigshu

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That's true, but it's also relative. Premium gasoline typically has .15 g/liter of lead. 100LL has .56 g/liter. Half a gram isn't all that much when you look at the amount of the fuel burned. It's the boutique nature of avgas that makes it expensive. Costs more to make, costs more to store and transport, and not much gets sold. Look at all the data we have from aircraft STC'd for mogas. Those aircraft don't fall from the sky because they are lead free. It's a shame that all engines that were ok on 80/87 octane fuel don't get a blanket ok to burn 91 octane premium gasoline. Practically criminal.
 

trimtab

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Ethanol fuels generally raise the octane, reduce particulate and NOx emissions, increase the enthalpy losses, and reduce energy density of the fuel. In terms of recovering per charge efficiencies, the effective compression ratio achievable with ethanol fuels can more than compensate for it. The increases in compression ratio have to be a bit more substantial to break even on volume. The Atkinson cycle is one compromise that can burn high ethanol fuels with the same reciprocating engine geometry by changing the valve timing appropriately. The increase in compression ratio generally obliterates the reduction in NOx emissions when optimized for power. It's a tight engineering corner.
 

skydawg

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Here's a link discussing AVGAS vs. MOGAS issues in aircraft. It's a bit more detailed than needed but has good info.


It's amazing that Lycoming or Continental never modified their design over 6 decades wherein every other industry did.
 

Vigilant1

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That's true, but it's also relative. Premium gasoline typically has .15 g/liter of lead. 100LL has .56 g/liter. Half a gram isn't all that much when you look at the amount of the fuel burned.
Yes, but the lead in mogas is there only because we have lead in avgas--it is cross-contamination from tanks, pipes, etc. When TEL is eliminated from AVGAS, it will also (eventually) be gone from mogas. As it is, despite the much smaller quantity of AVGAS burned compared to mogas, AVGAS contributes much more lead to the environment than the trace amounts in mogas does.
It's the boutique nature of avgas that makes it expensive. Costs more to make, costs more to store and transport, and not much gets sold.
Fer sure. And, in some places, there's not much price competition at the retail level, so that increases the price.
 

Doggzilla

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Not sure where you find "mixture pumps" I work for a petroleum pipeline, and the only fuels that leave our facilities meet a specification, and are legal to sell as is. Regular, Mid-grade and Premium gasoline are all stored in their own underground tanks at gas stations, and there's no mixing at the pump. The mixing takes place at the terminals, and you can get whatever % blend that's offered by the suppliers. Most "gasohol" is either 10 or 15% ethanol, depending on the state mandates in place. High ethanol blends are typically used by municipalities, not often at retail outlets. There is a reduction in fuel economy as the ethanol % increases, which some people don't mind in trade for the octane improvement. Prium gasoline with 10% ethanol typically tests out at 93 octane. We find some retailer stations will offer ethanol free gasoline, but it's rare. Marinas prefer ethanol free fuels, as do small motors (like lawn mowers, etc).
Blender pumps are actually very common. Especially with ethanol. It vastly reduces logistics problems.


I know a professor who is a pipeline engineer and according to him the mid grade is from different batches of product mixing in the pipeline because they cant purge it between batches. They just pump in the new batch and the mixed stuff between the batches is pumped out into another tank until it starts coming out pure.
 

Doggzilla

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Ethanol fuels generally raise the octane, reduce particulate and NOx emissions, increase the enthalpy losses, and reduce energy density of the fuel. In terms of recovering per charge efficiencies, the effective compression ratio achievable with ethanol fuels can more than compensate for it. The increases in compression ratio have to be a bit more substantial to break even on volume. The Atkinson cycle is one compromise that can burn high ethanol fuels with the same reciprocating engine geometry by changing the valve timing appropriately. The increase in compression ratio generally obliterates the reduction in NOx emissions when optimized for power. It's a tight engineering corner.
Cummins diesel is working on an ethanol diesel and it already greatly outperforms existing diesels. It has 30% more torque per given RPM. Since they are the kings of the Diesel world, its somewhat likely we will see a ethanol diesel eventually.
 

Derswede

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Blender pumps or dispensers mix two grades of fuel. For example, if you have a tank of premium and regular, you can mix for a mid-grade octane. The blenders are not designed to mix alcohol and fuel, just two fuel grades. Alcohol is mixed in at the tank farm or distribution point, as are any detergent packages, etc for a specific retailer. I helped design the blender pumps of the brand "Gilbarco."

Derswede
 

Doggzilla

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Blender pumps or dispensers mix two grades of fuel. For example, if you have a tank of premium and regular, you can mix for a mid-grade octane. The blenders are not designed to mix alcohol and fuel, just two fuel grades. Alcohol is mixed in at the tank farm or distribution point, as are any detergent packages, etc for a specific retailer. I helped design the blender pumps of the brand "Gilbarco."

Derswede
They are very commonly used for ethanol. I already provided a link.

Where do people get the idea that because they haven't seen something it doesn't exist?
 

Derswede

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Units are used in mixing alcohol, but the problem is the mixing valve does not last long with pure Eth. Our sister company in Brazil had many problems with the mix valve materials failing in pure alcohol. Viton was being used already, but it got eaten fairly quickly. Most of the applications we had used a high % alcohol fuel base and was mixed with a lower % Eth fuel. Valve life was short. One company which uses our tech mixing alcohol in that way is the Sheetz fuel stores. The tech was originally for Venezuela, where fuel was $0.25 a gallon and it was blended with a cheap base stock to give up to 5 grades of fuel. Poor bought the cheap stuff, those with more money bought the higher octane products. Always wanted to bring home a couple of tankers of Venez. gas at a dime to a quarter a gallon. Could have made a few $$!
 

TFF

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The last 20 years Lycoming and Continental engines can handle no lead. Most engines can handle lower octane.

The issue is legacy engines that are high octane and or that need lead. As it sits the only way the FAA can legislate no lead is to ground any aircraft that requires leaded gas especially high octane. It would be in the form of an AD. No one with a car has to follow a recall. Airbags not going off or with more force breaking your neck does not require you to comply. The dang cheapskates that airplane owners are, me included, would bear arms if your 1972 Mooney or your 1959 172 required an engine before next flight by an AD.

Safety police also have to make sure you are not calling it complied with. Unleaded will be cheaper. How will the FAA keep you from putting unleaded in your Cessna 310 turbo, when it has to have lead.

The FAA told the EPA to shove it. They protected you from the AD that could ground your plane. EPA getting constant pressure from the government who is getting pressure from The UN. There is no way the FAA with its 100% or else can do anything but stall. They definitely don’t have the budget or backbone to go through every type certificate to pitch out the problem planes and ok the others. They can’t say “most likely not to have a problem.” That’s not 100%. The FAA’s yearly budget is about the same as what some billionaire’s kid buys a house for to trash. At some point some aging aircraft line in the sand will be drawn, not for safety like they say, but because it’s the only way they can catch up.
 

BBerson

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Propane is 91,000 btu per gallon. Fully vaporizes and is octane 120. Might only need a small percent injected to raise octane. Propane is delivered almost anywhere.
 

Doggzilla

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Propane is 91,000 btu per gallon. Fully vaporizes and is octane 120. Might only need a small percent injected to raise octane. Propane is delivered almost anywhere.
Physically this is possible but I am not sure about chemically. Since the fuels cannot blend this may not have the intended effect.
 
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