Etanol.nu

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InläggPostat: mån 09-12-14 20:19 
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Blev medlem: mån 08-09-01 22:07
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Hello!

how can we calculate minimal temperature of intake air for ethanol fuel?

i have automatic thermostat for intake air for carbureator engine, and it holds 35C, mixing hot and cold air.

for which temperature i have to adjust it for ethanol?

PS in book "Alcohol as motor fuel" (1933 year) there is some data about it:

with full evaporisation, temperature in intake decreases:

1. at 18-22°C for gasoline,
2. 85°C for 98% ethanol
3. and 98°C for 85% ethanol.

so, for 98% ethanol, temperature of intake air has to be 85°C + 13°C = 98°C ?

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InläggPostat: mån 09-12-14 21:44 
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Blev medlem: tis 06-12-19 15:54
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If these figures are correct (balancing air heat content and ethanol vapouization heat) for a stoichiometric mixture (AFR = 9:1) I think you should take ino account the heat transfer from the cylinder walls and the piston top when the mixture is in the cylinder and the additional compression heating before the spark ignition. Therefore I suspect that somewhat lower temperatures are optimal. Thus a proportion of unvapourized ethanol should enter the inlet valves to use that extra heating once inside the cylinder.

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InläggPostat: mån 09-12-14 23:02 
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Blev medlem: lör 06-12-23 09:31
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Yes I thhink so too, in an ideal situation the evaporation happens mosty durning the compression stroke, that way the compression stroke does not slow down the engine as much. On the other hand all fuel should be evaporated at the end of the compression stroke so that the combustion goes quickly and completely.

If the air needs to supply the heat energy for evaporisation of the fuel smaller droplets will evaporate well before larger ones.

That makes me think that a combination of preheated air and preheated fuel would be optimal. If you only heat the air and the fuel is very cold there is always the risc that larger droplets will not evaporate in time when the intake temperature is optimal for smaller droplets.

/Aryan

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InläggPostat: tis 09-12-15 00:06 
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Blev medlem: mån 07-01-01 20:57
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And we are back to the problem of heating large volumes of air enough in higher engine speeds.
(That old book is very interesting to hear from!
Is not available on the net..?)
But the degees mentioned is how much the air is cooled DOWN by full evaporation, not a recommendation on how much to heat.
But was it not also written about fuel heating?
Nothing about the combination of fuel heating and air heating?

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InläggPostat: tis 09-12-15 09:39 
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Blev medlem: mån 08-09-01 22:07
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http://depositfiles.com/files/hzsxbdp1h

but it is scanned and not in very good quality, for translating you need to OCR it first :(

there was recomendations about heating fuel and air, and heating of air called much more effective.

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InläggPostat: tis 09-12-15 10:09 
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Blev medlem: lör 06-12-23 09:31
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However it is an interesting idea to re-adjust the thermostat for intake air. I have always thought that for optimal efficiency it is better to have permanent heating of the air also in the summer, because ypu never reach so high temperatures that it affects efficiency negative anyway, but maybe it is a better idea to change the termostat to a higher temperature.

If the new fuel is not heated and the ideal temp for gasoline really is 35°C your calculation 85°C (evap heat for new fuel) - 20°C (evap heat gasoline )+ 35°C = 100°C would be correct.

On http://www.scribd.com/doc/13359829/Mola ... loid-state I found that the heat of evaporation of the mixture of gasoline and ethanol is linear to the amot of ethanol and gasoline so if he AFR is also linear one could even presume that the evap heat value for for E85 would be something like 0,85x -85°C + 0,15x -20°C = 75°C and the teoretical ideal intake temperature would be 75°C - 20°C + 35°C = 90°C

I also tried to find the enthalpy of vaporization for some fuels and how much heat energy is taken from the air in a stochastic air fuel mixture:
butane 21 kJ/mol, 320 kJ/kg AFR 15,4 -> 20,8 kJ/kg air
petrol 26.2 kJ/mol 293 kJ/kg AFR 14,7 -> 19,9 kJ/kg air
diethyl ether 27.247 kJ/mol 368 kJ/kg AFR 11,2 -> 32,9 kJ/kg air
ethanol 38.6 kJ/mol, 841 kJ/kg AFR 9 -> 93,4 kJ/kg air

Given a specific heat of air of a little over 1 kJ/(kg·K) the temperature in the intake decreases with the same amount of degrees as the above values:
petrol ∆T -19,9°K
ethanol ∆T -93,4°K (add water and it gets worse)
butane ∆T -20,8°K
diethyl ether ∆T -32,9°K

Or did I make a mistake somewhere ?

/Aryan

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InläggPostat: tis 09-12-15 10:47 
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Blev medlem: mån 08-09-01 22:07
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in this book described testing carb. engine on mixtures benzol/ethanol 80:20 and 60:40.

minimal temperatures for good working was +15C and +30C.

if we will approximate temperature for 100% ethanol, we will have 75C

but it is for carbureator engine, where most fuel has to be evaporeted in intake mainfold.

now we have fuel, injected onto hot closed intake valve - it helps to evaporate.

and compression ratio in 1933 was about 4...6 :1, now it is about 9...11:1 for standart gasoline engines.

so i think temperature about +50...+60C will be enough for high RPM and lower temperature for lower RPM - on lower RPM fuel will have more time to evaporate.

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InläggPostat: tis 09-12-15 17:34 
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Blev medlem: mån 07-01-01 20:57
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Obormot skrev:
http://depositfiles.com/files/hzsxbdp1h

but it is scanned and not in very good quality, for translating you need to OCR it first :(

there was recomendations about heating fuel and air, and heating of air called much more effective.


Aha, but my wife can read russian!
But,
Citat:
We are sorry, but all downloading slots for your country are busy.

Can U maybe upload it to some place where availible, admins of etanol.nu, can we fix possibility to upload files to this forum, it can be useful in cases like this!
(I doubt that any russian copyrights apply in this case...the writer was probably shot 1917, if he claimed any ownership..)

UPdate: I waited and now I have the file!
But how to see it, what program to open it with?

Really, more effective to heat air?
Any explanation why, and what temperatures we are talking about for air and for fuel?

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InläggPostat: tis 09-12-15 17:43 
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Blev medlem: mån 08-09-01 22:07
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http://www.djvu.org/links/

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InläggPostat: tis 09-12-15 18:20 
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Blev medlem: mån 07-01-01 20:57
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Ahh great!!
Can U lead me to the page where its recomended to heat air instead of fuel?
(I doubt my wife wants to try to find it herself... :lol: )

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InläggPostat: tis 09-12-15 20:25 
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Blev medlem: mån 08-09-01 22:07
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pages 24-25.

Chapters:

1. basic requirements applicable to motor fuels ... 11
2. basic properties of alcohol as a motor fuel ... 14
3. alcohol tests on engines ... 24
4. corrosion of metals under the influence of alcohol fuels ... 28
5. mixture of alcohol and ether ... 33
6. mixture of alcohol with benzene (benzol) fuel ... 37
7. benzene-alcohol mixture (gasoline) ... 49
8. not evaporate residues gasoline-alcohol mixtures ... 62
9. mixture of absolute alcohol with gasoline ... 67
10. ways to obtain absolute alcohol ... 74
11. Motor mixture of absolute alcohol with gasoline ... 82
12. stability of ternary benzol - alcohol - benzene mixtures ... 85
13. evaporation of ternary benzol - alcohol - benzene mixtures ... 95
14. Motor testing of automotive ternary benzol - alcohol - benzene mixtures ... 105
15. Motor testing of aviation ternary benzol - alcohol - benzene mixtures ... 113
16. stabilization of mixtures of alcohol with gasoline ... 120

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InläggPostat: tis 09-12-15 23:04 
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Blev medlem: lör 06-12-23 09:31
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Sounds like an interesting book.

Ethanol has a specific heat of 2.44 kJ/kg, air just a little bit more than 1 kJ/kg if the engine has an AFR of 9:1 so in the mixture (1,144 kJ/kg) the heat capacity is 0,244 kJ/kg for the fuel and 0,9 kJ/kg for the air.
In a carburetor engine you can't heat the ethanol more than 78°C because it will boil and the air you could heat as much as you want. May be that is why the book reccomends to heat the air rather than heating the fuel?

In a fuelinjected engine when the fuel in under pressure it can be heated beyond the 78°C, which I think can help fast anatomization but still, the air can potentionally transport more heat energy.

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Komplettera gärna data om dit piggybacksystem här: http://www.editgrid.com/user/aryan/E85_piggyback_system och här viewtopic.php?f=10&t=6352


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InläggPostat: tis 09-12-15 23:04 
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Blev medlem: tis 06-12-19 15:54
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Interesting to see the many references cited! The Swedish researcher E Hubendick apparently worked a lot with ethanol as fuel, see references no 72 to 82. Another is O Cyren, ref 20.

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InläggPostat: tis 09-12-15 23:25 
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Blev medlem: tis 06-12-19 15:54
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An article where E Hubendick is cited.
http://tinyurl.se/g2aotk

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