A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Owning
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

More About Leaning During Climb



 
 
Thread Tools Display Modes
  #12  
Old July 11th 03, 04:11 AM
Mike Rapoport
external usenet poster
 
Posts: n/a
Default

We optimized the timing for the H2O injection and it still made less power
than without the H2O. Based on my experiences, I doubt that one could make
more power with higher compression and H2O injection than with a compression
ratio suitable for the fuel.. The only time more power will be made is with
an increase in MP (turbocharging) were H2O injection functions as a really
effective intercooler.

Mike
MU-2


wrote in message
...
Mike Rapoport wrote:
: If you inject water into an engine with no other changes, power will go

down
: a lot. I have used water injection to get a high compression engine to

run
: on 92 octane fuel and the H2O decreases performance. Now if it were a
: turbocharged engine, I could increase the MP without detonation and

produce
: more power, but that power would be the result of burning more air and

fuel
: (not the water).

This could also be due to the poor ignition timing after this is
done. The timing (24 BTDC typical) will put the peak pressure pulse after
TDC. If you effectively retard this by slowing the burn with water
injection, the power will go down appropriately.

: Like you said, you are consuming energy to heat and vaporize the excess
: liquid. The energy used to heat the liquid to the boiling point and

then
: effect a phase change is lost. You are puting liquid into an engine and
: having it come out the exhaust at a higher energy level (hotter and
: vaporized). That energy came from somewhere. It came from the power

output
: of the engine.

Perhaps somewhat, but remember that typically almost 70% of the
energy in the fuel for a gasoline engine is *not* used to turn the crank,
but rather just makes your muffler glow a nice cherry red. It's the
integral of pressure, area, and crank throw that produces rotational
energy in the form of torque and RPM. I believe that water injection is
pretty much like high octane fuel. Some people (idiots, mostly) believe
that by putting fuel in their car that's higher octane than the car's
manual stipulates results in increased performance. All higher octane
does is let *OTHER* changes that can then be done (advanced timing,
increased CR, etc) to increase the power be performed and not damage the
engine. Water injection should amount to the same... all other things
equal, it will reduce the power somewhat. BUT if you do it, you can then
increase the CR, advance the timing, etc... and get more back out of it.


Imagine this: inject water into a high compression
: cylender and rotate the crank. The water will vaporize into steam. If

what
: you are suggesting (that the steam is higher in volume and will drive

the
: piston) where true, you could make an engine that would produce power

and
: steam from water alone.

Man... if only I could get my carb set right for that....


: Try this: Lean to best power mixture in your airplane, note your speed

or
: climb rate then go full rich and watch the performance decline.

Oh yeah... here in SW VA at 2100' field elevation, it about
vibrates off its mounts if you takeoff full rich on a 4200' DA day.
Doesn't climb too well either. Too rich is bad for everything except
CHT's.

-Cory


--
************************************************** ***********************
* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
************************************************** ***********************



  #14  
Old July 11th 03, 02:36 PM
James M. Knox
external usenet poster
 
Posts: n/a
Default

"Mike Rapoport" wrote in
:

Like you said, you are consuming energy to heat and vaporize the
excess liquid. The energy used to heat the liquid to the boiling
point and then effect a phase change is lost. You are puting liquid
into an engine and having it come out the exhaust at a higher energy
level (hotter and vaporized). That energy came from somewhere.


Agreed. I think we all wound up in agreement on that one. I had
originally thought that Cory was saying that there *was* no heat
absorbed in vaporizing the unburned fuel, and that I was having trouble
accepting. G [True, it's only about 1/4th that of water, but it's
still there.]

But on further msg's back and forth, I think we are in agreement. There
*is*, as you say, a decrease in temperature due to vaporization.

And I will agree that there is probably also (and maybe bigger) a
decrease due to the change in flamefront propogation as the mixture is
enrichened. [Although I question if this is quite correctly
represented. It may give the conductive cooling more time in which to
work, but the exact same amount of energy should be released unless we
slow it up so much that we start shoving flaming fuel out the exhaust
(which can happen). Otherwise, it burns cooler but it burns longer - up
to the still same amount of O2 available.]

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Newbie question on Rate of Climb Wright1902Glider Home Built 0 August 17th 04 03:48 PM
Old airframe, new engine Jim Strand Naval Aviation 52 November 3rd 03 10:04 PM
Leaning with EGT? Chris W Home Built 3 September 18th 03 07:28 PM
Second Stage Climb Gradient? Bill Instrument Flight Rules 10 September 15th 03 06:41 PM
Minimum rate of climb or descent Aaron Kahn Instrument Flight Rules 3 July 25th 03 03:22 PM


All times are GMT +1. The time now is 12:28 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.