Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Sp4de on July 07, 2005, 08:46:10 PM
-
Would it be possible to have it so if you dont turn off wep your engine goes BANG?! (overheat) or something... I'm no history buff so it may not even be possible.
-
Engines did not typically explode when WEP or other performance boosters were (over)used.
Water injection would simply result in a loss of horsepower when it quit.
Same with Nitrous when it ran out.
Overboosting for too long could cause damage to the cylinder heads, but not likely catastrophic unless there was already something wrong with the engine.
Overheating doesn't cause engines to explode, either. Instead, they either seize up due to the oil breaking down and no longer lubricating the moving parts, or the engine nacell catches fire, or the engine just runs rough or quits because the plugs fouled up.
And then there's my personal favorite, and that is the magneto's 'grenading' due to massive over-revving.
-
Thanks tails, My friends are into rice rockets so i hear about them seeing alot of turbo's gernading. I think it would be cool to have something like that in ah
-
Theoretically, you could overspeed the turbo in the P-38 or the P-47, but you had to be way up high, and really moving to do it. Most often, it happened to P-38's, when the pilots were not properly instructed on how to operate the engines. Simply put, they let the oil get too cold, causing it to congeal in the turbo regulators, allowing the turbo to overspeed and explode. There is an armored ring around the turbo to protect the rest of the plane from being damaged by a turbo explosion.
When WEP includes water injection, or water/methanol injection, yes, an engine could be quickly and easily severely damaged if the power setting was used after the water or water/methanol ran out. The water or water/methanol is injected to lower both exhaust and combustion temperatures to prevent detonation. To continue to operate an engine under detonation WILL destroy it.
Detonation will:
Crush ring lands on the pistons.
Shatter rings.
Break or burn valves.
Hammer out rod bearings.
Melt pistons until they cave in.
For dry WEP, it simply overheats the engine. Power will be reduced, and if the throttle remains in the WEP setting, the engine will fail.
You can see all sorts of examples of these failures if you see the air races at Reno. The engine failures seen there, and seen often, are the result of operating the engine at WEP type settings and having it fail due to overheat and over stress, or failure to properly manage "wet" WEP.
You'll hear Reno racers talking about the "tweedle" valve, or "tweedling" water. In MOST planes, the pilot has to monitor the engine temperatures while flying at nearly 500MPH 20 feet off another plane and 50 feet off the ground, and "tweedle" water to keep the engine temperatures within the correct range. Too much water and it makes less power, too little and it blows up. It costs about $100K to fix one, if it can be fixed. The top teams, Dago Red for example, have on board telemetry, that broadcasts the engine parameters back to the crew on the ground. They radio the pilot and tell him to "tweedle'' more or less water, or otherwise adjust to control the temperatures. They can also alert the pilot to impending failures, giving him more time to pull out and make it back to land.
An interesting note. The Merlin engine was unable to run hard enough to win at Reno and stull finish without catastrophic failure until someone adapted Allison connecting rods to the Merlin in the late 1960's or early 1970's.
-
Well, even A-P's learn something new every day. Guess I should keep my yap shut about water injection systems, seeing as I've never got my paws dirty on one :D
-
Originally posted by Tails
Well, even A-P's learn something new every day. Guess I should keep my yap shut about water injection systems, seeing as I've never got my paws dirty on one :D
Don't feel bad, I've been working on race cars and race engines for almost 30 years, I learn ALL the time.
I've been wanting an A-P rating so I could fool with aircraft on the side, I just cannot afford to get there from here.
I learned about the dry and wet WEP from talking to guys like Steve Hinton, and from working on pulling tractors with aircraft engines.
You are correct about nitrous oxide. It is really just an artificial atmosphere, or a chemical supercharger. It cools the intake, and provides more oxygen to mix with fuel. When you run out, the mixture just goes rich, for lack of oxygen. Mostly it just quits making power.
What I posted was a grossly oversimplified explanation of how water and water/methanol works. Water itself really kills power, but the methanol burns, it adds octane and power. It mixes almost homogenously with water, as methanol is hygroscopic, and that allows the water to be used in the combustion process, rather than to just cool the cylinder and chamber and put some of the fire out. However, methanol is corrosive, and mixing it with water makes it worse.
We inject pure methanol into turbocharged engines as a means of cooling the charge like an intercooler, and to add octane to the fuel. People more insane than we are use propane instead. I call it propain, because used wrong it will cause you serious pain in the area of your hip, where your wallet is.
-
Originally posted by Captain Virgil Hilts
I've been wanting an A-P rating so I could fool with aircraft on the side, I just cannot afford to get there from here.
If you know anyone who's an A-P, see if they'll let you work with them. It takes (alot) longer, but you can skip 147 school that way. Still need to take your written tests and orals and practicles though.
-
Originally posted by Tails
If you know anyone who's an A-P, see if they'll let you work with them. It takes (alot) longer, but you can skip 147 school that way. Still need to take your written tests and orals and practicles though.
I don't know anyone around here with an A-P certification.
Bodhi was going to try to get me together with someone around here (Nashville TN) with a warbird, but I have problems at my business right now, my partner is deathly ill.
-
Sorry to hear about that.:(
-
Water injection would simply result in a loss of horsepower when it quit.
As Virgil points out.
Not necessarily. Anti knock agents are essential for running a motor at extreme pressure and rpm`s.
Until the alkane ratio was adjusted in C3 fuel, the BMW801 series could burn through pistons at 1.42ata due to excessive knocking.
After the adjustment a variety of boost systems were tested for their antiknock properties for Erhöhte Noteilstung. C3-Einspritzung was found to be the best antiknock and delivered the greatest performance gain when compared to Methanol Water or Ethanol Water. C3-Einspritzung delivered twice the performance gains of MW or EW.
So yes, cutting off the delivery of the agent can have a catastrophic effect on the engine.
All the best,
Crumpp
-
Well, like I said, I have zero experience with water-injection systems, and was going on the theory that the power was developed mostly through the increase in compression ratio from the injection of a non-compressable mass (IE Water).
But, as was pointed out, I was wrong.
-
Well, like I said, I have zero experience with water-injection systems, and was going on the theory that the power was developed mostly through the increase in compression ratio from the injection of a non-compressable mass (IE Water).
No problem at all! We are all learning. My research for both my book and the White 1 Foundation have caused me to learn quite a bit compared to what I knew about these aircraft/engines 3 years ago.
Speaking of antiknock properties. Made an interesting discovery about antiknock fuel additives. These are not agents injected into the mixture but rather added as part of the refining process of the fuel.
Because of the antiknock properties of natural petroleum vs. synthetic fuels you can pretty much throw any allied test of German engines that did not use German Fuel in the garbage can.
The allies were not even aware of the German Synthetic fuels antiknock agents. The natural petroleum Avgas required less antiknock additives and used different chemical compounds as antiknock additives.
Without the correct amount of antiknock additives, the German engines could not develop full power.
Since our motor ran on C3 Fuel, we are forced to get a petroleum chemist to analyze the fuel we will use and develop custom additives or, if the fuel turns out to suitable, run the engine at reduced pressures.
All the best,
Crumpp
-
Uhmm....
What makes the BMW from the 190 so vastly different from the other radials of WW2?
Or rather specifically, today the "new" 190's from the line use a russian radial. Very similar in most ways. So???
-
Valve and ignition timing and compression ratio, I would bet.
-
Uhmm....
Nothing except it was designed to optimize the German fuels as were the other German engines. You have to work with you have, right?
Tails is exactly right. Angus, you can most certainly use natural petroleum Avgas in our 801. You just have use additives or not run it at full Manifold pressure and rpm. At lower pressures, the motor would run fine.
The Russian engine was designed to run off natural petroleum. That is one of the reasons Flugwerk went with it.
Just read the Allies analysis of German Fuels from June of 1944. They end up with more questions than answers.
(http://www.onpoi.net/ah/pics/users/503_1120872933_c3fuelspeculations.jpg)
The Allies did not even know what the Germans were using for antiknock additives.
(http://www.onpoi.net/ah/pics/users/503_1120872887_alliedantiknockagents.jpg)
The Germans used the alkane ratio of their fuel as their main antiknock additive, specifically they adjusted the ratio of butane / propane from 25 : 75 to 50 : 50.
All the best,
Crumpp
-
Just idle curiousity here, but if you had to guesstimate an octane rating for german aviation gasolines for the time...
Because the way it sounds, they must of been running insane compression ratio's on what were NOT diesel engines, so the octane numbers would of had to been similarly high.
-
The Germans improved their fuels during the course of the war dramatically.
Using a process they developed in the 1920`s called hydroforming, C3 was the equivalent of allied 150 Octane by late 1943.
(http://www.onpoi.net/ah/pics/users/503_1120875325_c3octane1943.jpg)
All the best,
Crumpp
-
Very informative, thanks Crumpp.
In Britain, there was a terrible problem for a time with the fuel. They used TEL as an octane booster, and it was mixed on site.
Evidently it was not mixed until homogenous. The TEL came out of the fuel in the intake and intercoolers on the P-38's, and they'd detonate badly. The TEL would then get into the engine in high concentrations and foul the plugs.
With the P-51, they said you never knew if it was rough because it fouled a plug or because it detonated and cracked a head. You only found out when it was too late if the head was cracked. Once the coolant leak got bad and the temperature went up, the Merlin would sieze in about a minute, no matter what.
Doolittle worked for Shell during peacetime, and he got Shell to solve the fuel problems in early 1944.
-
TEL was used as well in German fuels, C3 having the same quantity of TEL as the allied 115/145.
-
Increased lead and its effects.
(http://hometown.aol.co.uk/JStirlingBomber/DCP_0163a.jpg)
(http://hometown.aol.co.uk/JStirlingBomber/DCP_0164a.jpg)
(http://hometown.aol.co.uk/JStirlingBomber/DCP_0165a.jpg)
Neil
-
Originally posted by Crumpp
(http://www.onpoi.net/ah/pics/users/503_1120872933_c3fuelspeculations.jpg)
The Allies did not even know what the Germans were using for antiknock additives.
(http://www.onpoi.net/ah/pics/users/503_1120872887_alliedantiknockagents.jpg)
The Germans used the alkane ratio of their fuel as their main antiknock additive, specifically they adjusted the ratio of butane / propane from 25 : 75 to 50 : 50.
All the best,
Crumpp
Crumpp, that is very hard to read for me. Can you post it slightly bigger? Thanks in advance.
-
Interesting stuff, thanks guys!
hogenbor I will repost it soon for you.
All the best,
Crumpp
-
Here you go!
(http://www.onpoi.net/ah/pics/users/503_1120915788_c3fuelconclusions.jpg)
All the best,
Crumpp