Sciencemadness Discussion Board - Safe and mild energetics to make E85 as energy dense as petroleum ?

Safe and mild energetics to make E85 as energy dense as petroleum ?

DubaiAmateurRocketry - 14-5-2018 at 15:39

Just brain storming, any clue?

The idea behind E85 is that its plant produced, so nitromethane for example, involving industrial process that involves propane (natural gas) is not wanted by people who uses E85 ?

a liquid thats miscible with ethanol or potentially a salt / compound that could dissolve in it ?
(provided that extracting this salt does not result in a detonable explosive)

[Edited on 15-5-2018 by DubaiAmateurRocketry]

RogueRose - 14-5-2018 at 21:03

Are you looking at something to add to up the energy/BTU content for mass production as a fuel for the general public or is this something like a specialty fuel for limited use like in racing?

I looked into this before and didn't find many options but I'm sure I didn't exhaust all the options. I had thought about mixing ethanol and diesel or something as it has a higher BTU rating than gasoline, but not by a whole lot. I did come across something that had a BTU rating of about 168,000 BTU/gallon, which is over double that of ethanol at 76,100 BTU/gal. E85 has a 81,800 BTU rating while gasoline (regular unleaded is 114,100). I think I found the high BTU fuel while researching jet fuels or possibly binary rocket fuels if that might help you find something.

Even if you found a fuel that was 168,000 BTU, you would need 40% of this fuel mixed with 60% ethanol to get a BTU (~112,800) equal to regular gasoline.

What I would suggest is trying to find a way to harness more energy from burning ethanol than how a standard engine does. IDK how well turbo charged engines run on E85 or even ethanol, that would be interesting to study if there were different efficiencies when a turbo or supercharger is added. I think there has to be a way to increase efficiency of engines by using the heat generated as an energy source in some manner. From what I have seen the average internal combustion engine uses about 20-25% of the energy for motion and the rest is lost as heat.

I'm wondering if harnessing the energy from heat using thermoelectric generators (peltier devices) and then using that energy for something like drive motors or motors to drive blowers. There are always ways to increase efficiency if you are willing to spend the $$ but there comes a point where there isn't a payback for it.

Here is a good page that lists fuels and their BTU content in comparison to gasoline.
https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent

Vomaturge - 14-5-2018 at 23:50

Some people believe that methanol made from biomass could be feasible. The process uses partial oxidation, pyrolysis, and catalysts instead of fermentation. As such, a ton of feedstock could in theory produce more alcohol this way. More importantly, the feedstock isn't corn or sugar. It can be sawdust, straw left over from growing wheat for food, old newspapers and egg cartons, or any number of other things.

Quote:

The goal of the program is to
reduce the cost of methanol from
biomass to $0.13/liter ($0.50/gal-
lon) from its present estimated cost
of $0.22/liter ($0.84/gallon). At the
reduced price it will be competitive
with the wholesale price of gasoline
from oil at $25/barrel.

Of course, since this is the National Renewable Energy Laboratory saying this, perhaps they mean they'll give it government subsidies to bring the price down. I'm not 100% sure that methanol is really the fuel of the future. If it were so great, why has it not been used as widely? I'd love to try this process at home, but I think it would be hard to control temperature, stoichiometry, catalyst area etc.

As far as what additives would boost the energy content of e85, I don't know. An engine uses both fuel and air. Since there's only so much space in the combustion chamber, then you can only get so much of both in at any one time. This will limit how much power you can put out per second, or how many horsepower the engine can produce. Additives we normally think of as "energetic materials" (fuel oxidizer mixtures, nitro compounds, etc) are ones which burn without air. When race cars burn nitromethane, some of the energy comes from these "airless" reactions. Since less air is needed to burn a given amount of fuel, you can put more fuel in the combustion chamber at once, and still burn all of it.

For the average driver, on the other hand, the goal is to have a fuel that is only needed in small amounts to create power. Even if you can only burn a little bit of it in a cylinder of air, that's okay. The best fuels in this case would be ones which can react with a much larger amount of air, to produce a fair amount of energy. If you are looking at energy per gallon (or kg) of fuel, and don't care about the volume and weight of air, then the best fuels will tend to be hydrogen , carbon, and of course hydrocarbons like gasoline. A mix of hydrocarbons and an alcohol will never be more powerful than hydrocarbons alone. An alcohol might be thought of as a partially oxidized hydrocarbon. You're just going to have to burn more of it to get the same result. Even if you did find an additive to make the fuel more energy dense, that additive would need to be cheap and environmentally safe to even make adding it worthwhile.

One more thing: "high-octane" fuels do not have more energy per gallon. They don't create more energy per volume of air in the cylinder either. They are just moderately harder to ignite. This allows them to be exposed to hot engine parts, high engine pressures, etc while still only igniting at the spark plug. Despite their low energy density, ethanol and methanol both have good octane ratings. Octane numbers matter because engines running at top speed get very hot, and because one way of making engines more efficient is to use higher pressures. If you have a hot, high pressure engine, and low octane gas, it will cause premature ignitions that reduce efficiency and wear out the engine. But, if you have enough "octane rating" to stop premature ignition, then having more "octane" won't do anything as far as I know. High octane gas doesn't burn hotter, it doesn't last longer, and it doesn't have more power. It's just a fuel more suited to high power, high efficiency engines. There are additives to boost octane ratings, but ethanol already has a great octane rating, along with low energy per gallon, a high price (when not subsidized) and a slight tendency to damage fuel pumps valves and such which are not designed to pump it.

phlogiston - 15-5-2018 at 01:34

The oxidiser is a limiting factor in the amount of energy released in an engine cylinder, not the fuel.

So, you would be looking for a compound that does not require air/oxygen to burn (like nitromethane).
Alternatively, adding a liquid or solid oxidiser to the fuel would also help, as you can then burn more fuel with the combination of air+liquid oxidiser.

DubaiAmateurRocketry - 15-5-2018 at 01:46

Quote: Originally posted by Vomaturge

slight tendency to damage fuel pumps valves and such which are not designed to pump it.

Right, was also wondering whats a lubricant with ethanol that could reduce that produce.

Doctor0000 - 25-5-2018 at 17:48

Quote:

IDK how well turbo charged engines run on E85 or even ethanol, that would be interesting to study if there were different efficiencies when a turbo or supercharger is added. I think there has to be a way to increase efficiency of engines by using the heat generated as an energy source in some manner.

Turbocharged and supercharged engines LOVE E85, people with 1.3-2.4l engines need 50-100lb/hr fuel injectors to keep up with forced air induction when run flat out.

This also kind of hits the nail on the head that the ability of a gasoline engine to make power isn't limited by the energy density of the fuel so much as the fuel/air+heat capacity of the cylinder and upper bound on reaction rate a spark ignition engine can handle before the engine detects knock or detonation.

RogueRose - 25-5-2018 at 18:47

I've been reading up on methanol and methanol/water injection and they seem to increase the HP output of the engine by cooling the engine (with the water) and upping the octane rating of the fuel. I think I've seen these used in both diesel and gasoline engines but I need to look further into this.

I was also wondering what would happen if instead of a straight water mix if something like 35% H2O2 was used, or some other concentration of H2O2, either with an alcohol or alone. The water would cool the cylinder and the decomposition of the H2O2 would produce O2 as well, kind of like adding a blower onto the engine. The problem that I have seen with adding water to the ignition cycle is the increased gas volume of water vapor which reduces the volume of vaporized fuel that can enter the cylinder unless under higher pressures.

Bert - 25-5-2018 at 22:39

Quote:

This also kind of hits the nail on the head that the ability of a gasoline engine to make power isn't limited by the energy density of the fuel so much as the fuel/air+heat capacity of the cylinder and upper bound on reaction rate a spark ignition engine can handle before the engine detects knock or detonation.

As much nostalgia as I feel for reciprocating engines, you want high power to weight ratios and the ability to eat enormalous quantities of fuel, it is time to break out the gas turbine. Especially now that engineering materials are catching up to the thermal and centrifugal stresses involved in pushing these to what seem to us old farts patently ridiculous fuel/air throughput.

nitro-genes - 7-6-2018 at 05:28

Or one of these, curious how efficient these would be... probably difficult to control output levels though

https://www.youtube.com/watch?v=DaHioh0emTo
https://www.youtube.com/watch?v=pHcxI-8GtZg

[Edited on 7-6-2018 by nitro-genes]

SWIM - 7-6-2018 at 14:37

Quote: Originally posted by Bert

Turbines may also be more feasible now than before because of the advent of hybrid cars.

With a hybrid, the turbine could be designed to run even more efficiently in narrower rpm ranges than would be possible if its directly driving the wheels through a transmission.

Generators that can be directly driven by high speed turbines are available in sizes appropriate for even tiny economy cars nowadays.

They're expensive (or were last time I checked), but the price would probably plummet if some big guy like FIAT or Ford started ordering them by the hundred thousand.

(I checked on high speed generators because I was curious about linking one to an exhaust turbine for co-generation on a reciprocating engine.)

kulep - 8-6-2018 at 15:01

As stated above cars produce more power when running ethanol. Fuel energetic density isn't a problem as your car doesn't care if it has to haul 50kg more, although planes do. Ethanol has a higher octane rate than gasoline, aswell as a higher specific heat.
The mass of fuel injected and specific heat cools the combustion chamber which toghether with the higher octane ratio allows for higher pressure in the combustion chamber, so better efficiency.

Gas turbines still require a lot of maintenance, high temperatures and rpm's aren't very nice to many materials

[Edited on 9-6-2018 by kulep]