Naked Science Forum
General Science => General Science => Topic started by: Eric A. Taylor on 06/06/2010 09:12:38
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Just watched the Indy 500 on my DVR (nice to skip the adds) They made a statement I feel I should point out may not be entirely accurate.
They stated that methanol produces about 60% of the pollution that gasoline (petrol) produces. I wonder if the comparison is made per unit burned (say gallons or liters)or work done (say miles or kilometers driven). The reason this is important is that methanol has only about 25% of the energy of gasoline per gallon. If you disagree this take a look at the last (quite deadly) Indy 500 in which the cars ran with gasoline. I think it was 1964 but I'm not sure.
Basically, with 1/4 the energy in methanol, you'll need to burn 4 times the amount in methanol to do the same thing you could do with gasoline. If your car gets 20 miles to the gallon in gasoline you'll get just 5 miles with a gallon of methanol.
So a more fair comparison would be comparing 4 gallons of methanol burned for 1 gallon of gasoline. If the 60% was a unit volume comparison (1 gallon of methanol to 1 gallon of gasoline), then it would be deceptive. In reality gasoline would be cleaner by 15% (if I did my math right) when comparing work done by burning the two fuels.
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The engery density of methanol is about 23 MJ/Kg while that for gasoline is about 45 MJ/Kg.
On a weight for weight basis gasoline has about twice the energy and , since methanol is slightly denser the energy per litre (or gallon) of methanol is a bit more than half that of gasoline.
Looking at the last gas powered Indy 500 race won't change that, so I will still disagree with the idea that it's about a quarter.
Since motor racing basically is just a waste of fuel, there's little point worrying much about the relative merits of the two different fuels.
It may be that, when they talk of less pollution they mean less soot etc- methanol burns very cleanly.
Also, burning a litre of methanol produces a lot less CO2 than burning a litre of gasoline
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Yea motor racing, yepper, if it weren't for that motor racing waste of fuel and time, we may still be using a 4 cylinder engine, single barrel carburetor 25.4 mm throat, with a mag spark with manual advance, that ironically produce less emissions and maybe get 45 miles to a gallon running 50 mph at 1800 rpm with a single malt brew.
There is more behind racing than just entertainment, you might say it is grossly misunderstood...
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Does methanol need all the additives that typical lead-free gasoline requires?
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Does methanol need all the additives that typical lead-free gasoline requires?
I just learned this, and have wondered why there is a fuel to air mixture for the petrol engine.
Efficient hot burn is (lean and mean); let the motor burn in the 4th turn.
Lead has been eliminated and what is left is the pollutant from the Hydrocarbon
Diminishing the ratio simultaneously sustaining the energy (MJ/L) levels is ideal,
With our present knowledge and technology.
http://www.newton.dep.anl.gov/askasci/chem00/chem00787.htm
Gasoline: A general combustion form for 8 octanes balancing the equation
C(n)H(2n+2) + [(3n+1)/2] O2 -------> (n) CO2 + (n+1) H2O
2C8H18 + 25O2 -- yields > 16CO2 + 18H2O
The formula for methane: CH4; Combustion of methane involves its reaction with ...
Need to be balanced
Methanol CH3OH + O2 --> CO2 + H2O
http://www.ebsinstitute.com/OtherActivities/EBS.qs1sa.html
Methanol CH3OH + O2 --> CO2 + H2O
Gasoline C8H18 + O2 --> CO2 + H2O
Hydrogen H2 + O2 --> H2O
Balanced formula shows the difference in the yield of the most Carbon and hydrogen combo Gasoline needed to be copied for it was a bit complex can’t count over 5 and keep track of the other bonds
Methanol 2CH3OH + O2 --> 2CO2 + 4H2O
Gasoline 2C8H18 + 25O2 --> 16CO2 + 18H2O
Hydrogen 2H2 + O2 --> 2H2O
http://en.wikipedia.org/wiki/Methanol_economy
Methanol has a high octane rating (RON of 107 and MON of 92), which makes it a suitable gasoline substitute. It has a higher flame speed than gasoline, leading to higher efficiency as well as a higher latent heat of vaporization (3.7 times higher than gasoline), meaning that the heat generated by the engine can be removed more effectively, making it possible to use air cooled engines. Besides this methanol burns cleaner than gasoline and is safer in the case of a fire. However, methanol has only half the volumetric energy content of gasoline (15.6 MJ/L vs. 32.4 MJ/L)
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Does methanol need all the additives that typical lead-free gasoline requires?
Not per-se: methanol already has a high octan number, high volatility and doesn't contain aromatics. Maybe some could additivate it with 0.25% of acetone to even increase the combustion speed, but just for competitions and where this is allowed.
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Just watched the Indy 500 on my DVR (nice to skip the adds) They made a statement I feel I should point out may not be entirely accurate.
They stated that methanol produces about 60% of the pollution that gasoline (petrol) produces. I wonder if the comparison is made per unit burned (say gallons or liters)or work done (say miles or kilometers driven). The reason this is important is that methanol has only about 25% of the energy of gasoline per gallon. .
Just 25% of the energy of gasoline per gallon cannot be true. About the pollution, remember that pollution doesn't mean CO2 and NOx only, it also means aromatics, unburned hydrocarbons and particolate. Methanol burns enormously clearer than gasoline, considering these 3 pollutants (which are the most important in this case).
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Indy cars (these days) run on Ethanol. They used Methanol for a while too.
Comparative Energies (MJ)
Gasoline 46.4/kg 34.2/L
Methanol 19.7/kg 15.6/L
Ethanol 30/kg 24/L
Diesel 46.2/kg 37.3/L
Source: http://en.wikipedia.org/wiki/Energy_density
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The engery density of methanol is about 23 MJ/Kg while that for gasoline is about 45 MJ/Kg.
On a weight for weight basis gasoline has about twice the energy and , since methanol is slightly denser the energy per litre (or gallon) of methanol is a bit more than half that of gasoline.
Looking at the last gas powered Indy 500 race won't change that, so I will still disagree with the idea that it's about a quarter.
Since motor racing basically is just a waste of fuel, there's little point worrying much about the relative merits of the two different fuels.
It may be that, when they talk of less pollution they mean less soot etc- methanol burns very cleanly.
Also, burning a litre of methanol produces a lot less CO2 than burning a litre of gasoline
I had only heard this durring the race. Methanol is being pushed hard for use in passenger cars, so I beg to differ. The argument us highly relivent.
Perhaps if you feel that way all spectator sports should be banned. Think of the amount of fuel "wasted" by sports fans going to and coming from events. My cousin got tickets to the "Civil War" (Oregon State vs. University of Oregon) foot ball game. It's VERY popular here in Oregon. Took him 4 hours just to get out of the parking lot.
On another point, somebody changed my title. I wrote "gasoline" not "car fuel" car fuel could be gasoline, diesel, methanol, LPG, natural gas, coal oil....it's too generic a term. Will the administrator kindly change it back?
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Just watched the Indy 500 on my DVR (nice to skip the adds) They made a statement I feel I should point out may not be entirely accurate.
They stated that methanol produces about 60% of the pollution that gasoline (petrol) produces. I wonder if the comparison is made per unit burned (say gallons or liters)or work done (say miles or kilometers driven). The reason this is important is that methanol has only about 25% of the energy of gasoline per gallon. .
Just 25% of the energy of gasoline per gallon cannot be true. About the pollution, remember that pollution doesn't mean CO2 and NOx only, it also means aromatics, unburned hydrocarbons and particolate. Methanol burns enormously clearer than gasoline, considering these 3 pollutants (which are the most important in this case).
You cannot make statements like this without backing them up. Simply saying it's not true is inflammatory (you're calling me a liar). If your willing to prove me wrong then do it.
I got my information about the properties of methanol vs gasoline from my father who worked 30 years in an oil refinery, so he knows a bit about gasoline.
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And you, Eric, can't say his statement isn't backed up without calling me a liar because I told you the energy densities earlier in the thread. Granted that I should have said a bit more than half, rather than a bit less.
In any event, Geezer has provided the data for the two fuels and also a source for that data.
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There is so much misinformation out there from both sides it's really hard to know what's true in environmental science. The only way to know for sure is to go into the field and do the experiments yourself.
I wonder if Dave can do a kitchen science experiment on this. I know there is a way to precisely measure the amount of work a particular fuel can do per unit burned. In the states we use units called "British Thermal Units" Don't know if BTUs are used elsewhere but it should not make a difference.
Just looked it up. 1 BTU will heat 1 pound of water 1 degree F. It's equal to 1.06 kilojoules.
Perhaps an experiment could be made up with a stove powered by alcohol and one powered by gasoline. I don't think an alcohol stove will be hard to find but a safe gasoline stove may be harder to find. That might tell you something about the BTUs in gasoline compared to alcohol. An alcohol camp stove is easy to find, a gasoline camp stove is considered insane!!!!
Could the temperature of the fame from each fire be measured directly? I know the flame from gasoline is quite visible in daylight where the alcohol flame is nearly invisible. This poses a danger to safety crews in F1 and Indy car races (along with any alcohol powered race car. The workers, in their haste to get to a drive might run into the fire.
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Eric, what's the need for a new experiment?
Geezers figures from Wikipedia are in Megajoules (although he's not put that).
It is clearer as:
| Energy by | weight | Energy by | volume |
| Gasoline | | 46.4MJ/kg | | 34.2MJ/L |
| Methanol | | 19.7MJ/kg | | 15.6MJ/L |
| Ethanol | | 30.0MJ/kg | | 24.0MJ/L |
| Diesel | | 46.2MJ/kg | | 37.3MJ/L |
BTUs can be expressed as Joules (as you point out), so the information is there already.
As I understand it, both Methanol and Ethanol allow far higher compression than higher fraction fuels (hence no need for anti-knock additives) and can therefore run at almost unlimited boost - so offsetting some of the energy limitations of the fuel with better power from a smaller (highly turbo'd) engine.
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Eric, what's the need for a new experiment?
Geezers figures from Wikipedia are in Megajoules (although he's not put that).
It is clearer as:
| Energy by | weight | Energy by | volume |
| Gasoline | | 46.4MJ/kg | | 34.2MJ/L |
| Methanol | | 19.7MJ/kg | | 15.6MJ/L |
| Ethanol | | 30.0MJ/kg | | 24.0MJ/L |
| Diesel | | 46.2MJ/kg | | 37.3MJ/L |
BTUs can be expressed as Joules (as you point out), so the information is there already.
As I understand it, both Methanol and Ethanol allow far higher compression than higher fraction fuels (hence no need for anti-knock additives) and can therefore run at almost unlimited boost - so offsetting some of the energy limitations of the fuel with better power from a smaller (highly turbo'd) engine.
I guess you didn't read my post. There is quite a lot of misinformation (ie LIES) out there. The only way to reliable sort truth from lie is to do the test yourself.
There is an american company that does testing like this but I can't remember the name. It's not Underwriters Laboratories, they test products, not martial.
I tend to get worked up on environmental issues like climate change, due to all of the contradictory information. i try to think about it logically. For example: I just heard a story about how climate change is going to kill all the lizards. This is stupid if you stop to think about it logically. Lizards have been around for a couple hundred million years. They have survived events that have killed off many other species, like the dinosaurs. They have survived hundreds and hundreds of ice ages and warm periods. (Climate change is not human caused because it's a natural part of Earth's cycles). Humans may have a hard time getting used to a warmer Earth but we've done it before and we didn't have high tech gizzmos to deal with past climate change. I think some species may become extinct because of climate change but it's happened thousands of times before and there are still a lot of preachers running around.
Climate change is as natural as the change from winter to spring to fall and back to winter. And there is not a damn thing humans can do about it, nor should we try to do anything. Ever read the "Rama" books by A.C.Clarke?
Oh and the engines in F1 and Indy Car are normally aspirated. (No boost from chargers).
The anti-knock level of gasoline is called "octane". and is represented by a number. The higher the number the higher you can compress before gasoline will detonate (knock). This is why Tetra-ethyl lead lead was added to gas in the 1920's
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The big problem with a kitchen science is that actually doing it properly is very difficult, as I would have thought that you would need a differently optimised engine for each fuel, and run the engine with a standard load, have a very accurate way of measuring fuel use etc.
So it would definitely be a case of finding a lab with the real kit if you wanted a result that actually meant anything.
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I guess you didn't read my post. There is quite a lot of misinformation (ie LIES) out there. The only way to reliable sort truth from lie is to do the test yourself.
Your guess is incorrect.
Without wanting to get into the whole world of conspiracy BS would you mind explaining who you think is spreading this misinformation about these fuels? And what they stand to gain from it?
Let alone how they would get away with it... [???]
I tend to get worked up on environmental issues like climate change, due to all of the contradictory information. [?] ... I just heard a story about how climate change is going to kill all the lizards. .... I think some species may become extinct because of climate change but it's happened thousands of times before and there are still a lot of preachers running around.
I doubt there are any serious climate scientists out there claiming that all Earth's lizard species will be made extinct by CC. Again, articles if you have them please [ ? ]
Further, there has always been a rate of attrition for some species to go extinct over the Earth's natural history. The important point is that this rate has accelerated significantly during the industrial revolution period.
Many people have started threads attempting to debunk climate change on this site, so you would not be the first to 'float' this line of (uh-hum) reasoning. I would suggest, if you do want expand your take on CC 'myths' you would be better to go for a new thread.
I have read the Rama series -a long time ago- BTW
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I think the numbers I posted from Wiki simply represent the thermal energies that can be produced by burning those fuels in air. It's not too difficult to do that, so if the numbers were grossly distorted, I think that would have been exposed. I'll check them out in a couple of other references. There will probably be some variation of course, but it should not be too great.
As Dave and Peppercorn have pointed out, it's not so simple to obtain the real work output from an IC engine that uses any of these fuels. There are a great many factors that can effect overall efficiency (thermal energy input versus mechanical energy output).
The automobile industry is extremely competitive. All the manufacturers are spending huge amounts of money trying to improve fuel economy to get any kind of edge over their competition. Some of the recent developments are quite impressive too.
Any conspiracy or deception would not stand. There are far too many people looking at this space - yours truly included.
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Eric,
The data on heats of combustion are well documented, easy to measure and not worth lying about.
To a good approximation, they can also be found (for ethanol and bio-diesel) in weight loss guides. Feel free to check your data before calling people liars.
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According to "Marks' Standard Handbook for Mechanical Engineers, 10th Edition";
Gasoline (90 octane) 20,500 Btu/lb 950,000 Btu/ft^3
Ethanol (99 octane) 12,800 Btu/lb 620,000 Btu/ft^3
Methanol (98 octane) 9,600 Btu/lb 480,000 Btu/ft^3
Those skilled in the art (or with b*gger all else to do) may wish to convert these figures into SI units [:D]
Oh! Forgot to mention - it also gives them in Btu/gallon, but as the US and the UK have rather different opinions about what a gallon actually is, I thought that was a rat's nest we should avoid.