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. |
|
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
|
#12
|
|||
|
|||
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
|
|||
|
|||
"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 | |
|
|
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 09:04 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 |