Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: GNucks on May 08, 2011, 01:40:56 PM
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I was in the TA earlier testing out some of my preferred aircraft and one of the things I looked for was how much extra gas you burn when you use WEP. And boy was I surprised when I got the Corsairs to discover that the GPH doesn't change at all when you engage WEP.
I was even more surprised when I got to the Jugs and found that the M and N models actually have lower GPH when on WEP. This is the case with the -4 model Corsair as well.
My question is: What other aircraft in Aces High behave this way?
But more importantly: Why? :headscratch:
I've been searching trying to appease my curiosity but I figured I'd ask here while I'm at it to see what some of the gurus have to say.
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Its the same power boost system on them, i heard its "water injection" or something. Im not sure.
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Its the same power boost system on them, i heard its "water injection" or something. Im not sure.
Yeah, I've read about different kinds of WEP, some just open the throttle even more, and then there's the water injection systems. Compared to the other planes I looked at these were the only ones that were said to use water injection, maybe that's the factor. I'll look into how it works and come back with what I find (if somebody doesn't ninja me).
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You're on the right track with water injection. Keep up the search. :aok
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From what I gather, emergency power was run with richer fuel mixtures before water injection. The extra fuel's purpose was to absorb the higher generated temperatures through evaporation. Obviously this is a pretty wasteful way to keep the temperature in check, because that fuel could be used for more combustion. Water injected systems allowed for much leaner mixtures to be used because the water could take care of the cooling, and the fuel can be used what it was meant for: actually combusting and generating energy.
I guess I could imagine the GPH remaining the same, but I'm still perplexed as to how more power can mean better economy. I mean, that just seams like an oxymoron based on "common sense" I've lived with my whole life. Muscle cars go fast and guzzle gas and little 4-cylinders go slow and sip petrol like a pompous noble sips tea. More power has always been at a sacrifice to efficiency.
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It varied from airplane to airplane depending on the systems. A number of Luftwaffe airplanes used a methanol injection system which uses the same principal. I don't know enough on the subject of Luftwaffe airplanes to say whether or not the methanol was diluted but assume so.
What you'll find is by injecting water into the fuel/air mix it effectively retards detonation to allow more power to be produced than if you were to simply throw fuel at it. Running the engine too rich will actually reduce the power output whereas the water allows more compression (temporarily as it is beyond what the motor is designed for) while keeping the fuel/air mixture lean enough to give you maximum power over throwing more fuel into the fire. What that meant was at a maximum power setting using an auto rich mixture, the use of the WEP (depending on the airplane) would actually lean the mixture and introduce the on board water supply into it. You're burning less fuel but producing more power, higher pressure and introducing more wear. "Cool" is a relative term as it's still going to get hot and it's not an infinite supply of free power that cools the motor.
Jet airplanes have used it and while it's not in service these days the older KC-135s used it when necessary on takeoffs as did early B-52s. I don't know what other airplanes
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Plus cooling the intake air, creates a greater air density, hence more power.
HiTech
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It varied from airplane to airplane depending on the systems. A number of Luftwaffe airplanes used a methanol injection system which uses the same principal. I don't know enough on the subject of Luftwaffe airplanes to say whether or not the methanol was diluted but assume so.
What you'll find is by injecting water into the fuel/air mix it effectively retards detonation to allow more power to be produced than if you were to simply throw fuel at it. Running the engine too rich will actually reduce the power output whereas the water allows more compression (temporarily as it is beyond what the motor is designed for) while keeping the fuel/air mixture lean enough to give you maximum power over throwing more fuel into the fire. What that meant was at a maximum power setting using an auto rich mixture, the use of the WEP (depending on the airplane) would actually lean the mixture and introduce the on board water supply into it. You're burning less fuel but producing more power, higher pressure and introducing more wear. "Cool" is a relative term as it's still going to get hot and it's not an infinite supply of free power that cools the motor.
Jet airplanes have used it and while it's not in service these days the older KC-135s used it when necessary on takeoffs as did early B-52s. I don't know what other airplanes
We used ADI (Anti-Detonation Injection) in our C-118s and C-131s. Both used versions of the R-2800. In WWII, the typical "water" was 50% Methanol/50% Water, or 50% Ethanol/50% Water. For a brief time in the ETO, Isopropyl was tried, but found to be unsatisfactory. Pratt & Whitney specified both Methanol and Ethanol.
As we see in the game, the NATOPS manuals for all aircraft powered by R-2800s used by the Navy limited ADI duration under normal conditions. However, in an emergency (like losing an engine immediately after takeoff, while near or at max gross weight), you could run the ADI pumps until the tanks were empty. At that point, the derichment valves would close and the carburetors would automatically enrichen the mixture to cool the combustion chambers to prevent detonation. ADI basically displaces an equal volume of fuel, so fuel flow (consumption) is reduced accordingly. The R-2800-52W engines on our C-118s, typically used about 12 pounds of methanol/water per minute, per engine to make 2,500 hp.
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Great info. Thanks!
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What a terrific model, game, and community. Thanks for the contributions. It sure is pretty awesome having dozens of resident pilots participating in the forum, they just can't help but share neat info. :aok
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but I'm still perplexed as to how more power can mean better economy... More power has always been at a sacrifice to efficiency.
Not exactly germane to WEP specifically, but if you increase the efficiency of an engine you will get more power too. If I can turn 80% of the potential energy in a gallon of fuel into kinetic energy, I would, in theory, be able to use half the fuel and achieve the same output as an engine achieving only 40% efficiency. On the other hand, i could use the same amount of fuel and double the power while keeping the economy the same. It's the same reason that modern muscle cars are getting 300+ BHP and 30+ MPG compared to the 60's cars at maybe half that mileage for the same power.
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IIRC - at 61" on the 1650-7 Packard Merlin - she was guzzling > 200 gph and at 30"/2300 rpm it was closer to 45+/gpm for the P-51.
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Jet airplanes have used it and while it's not in service these days the older KC-135s used it when necessary on takeoffs as did early B-52s. I don't know what other airplanes
Wasn't it the water injection that caused the massive smoke output?
I've heard that on jets the water added "mass" to the flow which increased thrust. Or was it used to cool?
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That sounds pretty reasonable considering that's what you'd want in a jet. I don't know about the smoke so I can't really speculate but it's plausible. The Harrier uses water for hover and you definitely see smoke coming out of the nozzles when it's engaged. I don't know many specifics which is pretty clear to begin with and less so regarding jets the use of WEP or Water Injection in jets.
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The Harrier uses water for hover and you definitely see smoke coming out of the nozzles when it's engaged.
The first Harrier combat sortie into Kosovo sprayed me with a fine film of it on its way down the deck on takeoff. At Reno, you can tell which aircraft are using ADI and which ones aren't from the plume of light smoke...
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dbl post...
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Wasn't it the water injection that caused the massive smoke output?
I've heard that on jets the water added "mass" to the flow which increased thrust. Or was it used to cool?
That sounds pretty reasonable considering that's what you'd want in a jet. I don't know about the smoke so I can't really speculate but it's plausible. The Harrier uses water for hover and you definitely see smoke coming out of the nozzles when it's engaged. I don't know many specifics which is pretty clear to begin with and less so regarding jets the use of WEP or Water Injection in jets.
I read something about that when I was reading up on the water injection systems earlier. The water increases the mass being pushed out the engine which means more thrust. It also doubles its use by cooling to prevent or postpone overheating. Unfortunately the water thrown in with the combustion stifles or quenches it somewhat and some of the fuel doesn't get burned, and that's what explains the black smoke.
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An older but good basic primer on water/alcohol injection:
http://www.flightglobal.com/pdfarchive/view/1946/1946%20-%201007.html