Plane engines

[niklas]

 

When talking super/turbo charges keep in mind that it's not the air that is compressed but the air-fuel mixture. This is the reason for their very existence.

i have to disagree. First the air gets compressed, fuel is added later.

 

Looking at the AH initial climb of the G-6 vs the G-10, both at climb power - suggests to me the G-10 has the 605DB engine.

what do you mean with climb power? 100% in AH?
One thing is sure, when you compare manifold pressure of the G6@wep and G10@100% then both seem to be very close together or equal. So I think 100% for the G10 in AH is maybe 1475HP, while 100% for the G6 ~1300HP

niklas

[niklas]

double post

[This message has been edited by niklas (edited 11-20-2000).]

[Vermillion]

 

then why not use a different supercharger?

Luke, in Engineering there is no absolute perfect solution. Its all a matter of tradeoffs.

If you optimize performance in one area, you usually give up performance in another.

Remember that to drive the supercharger, it requires part of the engines power to run it. So therefore, if you increase the superchargers power (increases performance at altitude) it requires more of the power of the engine itself. So what happens is that at Sea Level, the aircraft can be actually slower than it would be without the change to the supercharger.

Its all a matter of tradeoffs!

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Vermillion
**MOL**, Men of Leisure

[Jigster]

The main reason superchargers are so prevailent is it requires some massive ducting work in order to make the turbo charger efficent enough to consider using over a supercharger.

On paper the turbos look more efficent but you have to add numerous objects in order to use it i.e. a collection manifold, linear linkage of the impeller and turbine (most efficent link) heat resistant materials, exhaust trailer, etc. This is why both the P-47 and P-38 are so huge, the interior of the P-38's booms and the P-47's fuselage are all ducting (albeit alot of the 38 is radiator ducting as well)

All this weight is hard to justify if a supercharger puts out roughly the same horse power.

With the compact airframes the Germans were insistant upon, it really makes no sense to try and install a turbo charger, because there is no way it will make the same power as the supercharger within the same space.

For comparison, the super charger on the F4U and F6F is not much bigger then the standard bell housing for a mid-size pickup. The turbo charger on the P-47 (not including the the ducting work) is roughly the size of a washing machine.

[RAM]

   

Originally posted by Vermillion:
Luke, in Engineering there is no absolute perfect solution. Its all a matter of tradeoffs.

If you optimize performance in one area, you usually give up performance in another.

Remember that to drive the supercharger, it requires part of the engines power to run it. So therefore, if you increase the superchargers power (increases performance at altitude) it requires more of the power of the engine itself. So what happens is that at Sea Level, the aircraft can be actually slower than it would be without the change to the supercharger.

Its all a matter of tradeoffs!

I understand this perfectly,Verm, but I still cant see why it wasnt done as you say.

Lets take RAF's example: they have a Spitfire F.IX. Good weapon for medium altitudes, and reasonable performance low and high.

Still they do a LF.IX with awesome low level performance (And quite well retained at medium altitudeS too).

And they do too a HF.IX optimiced to very high altitudes, able to retain too a very good performance at medium altitudes.

Bassicaly they had a weapon that performed well at all altitudes, still they improved the performance of some of the types.


Now, we take a look into a Fw190A. Awesome performance at low levels with a very high engine output (for a 14 cylinder engine). But this same engine gasps for air over 20000 feet, and most of the Fw190A's use as interceptor of bombers over the reich is at altitudes od 25000-30000 feet.

There was a heavy need for a high level interceptor, still the only thing they gave to the BMW801 was a GM1 boost?...

If you have to sacrifice low level performance, go ahead, anyway the FWs on Germany wont do many Jabo missions, but they are really needed as high level interceptors.

Something is missing here, Verm...there must be a real reason for not having a supercharger optimiced for higher altitudes in the 190.

(in fact, and after reading those threads about the Ta152 they sure did sacrifice low level performance to attain great high level performance...(deck speed of 335mph? ouch!!!)but in 1945 and with an inline Jumo inline engine. I cant understand why they didnt it in 1943 and with the BMW radial engine   )

[This message has been edited by RAM (edited 11-20-2000).]

[Luke Skywalker]

Well, I have to agree with RAM in this matter, the Fw190D9 was built with an inline engine just because they couldnt get good high altitude performance from the BMW801, right?.

So, something was wrong with the supercharger?...someone knows?

[Hans]

I have a book with a nice detailed cutaway of several engines.  Maybe describing the full process of the Merlin XX engine airflow would help.

First, the engine's air intake is under the back of the engine, pointing straight down.  Next is the carburator.  Then the air is ducted straight up, makes a 90 degree turn right into the face of the single stage supercharger.  The "fan" isn't what you would think.  Its a nearly flat disk, with a bunch of straight fins on it radiating out from the center hub.  The air comes in over the middle hub, and the fins throw the air out to the edge.  The now compressed air is fed straight up to the top of the engine, turns 90 degrees and runs down between the "V" of the two rows of engine cylanders and feeds each one.

The air does have the fuel vapor in it as it runs thru the supercharger.  Note:  The BMW 801 injects the fuel into the air after the supercharger.

The compressor is a centerfuge configuration.  The compressor has two speeds it runs at, and is powered by a shaft geared off the engine's crankshaft.

Also, something mentioned above, but not given it's proper name.  In two stage superchargers there is a cooling device.  Air comes into the first stage, is compressed (which also heats it), goes thru a cooling device called the intercooler, and then into another compressor, then on into the engine cylanders to burn.

The reason you cool the air isn't because its dangerous or something, its to further compress the air.  Cold air is dense air is smaller volume air.  You can fit more cool air into a space than you can hot air.  Cooling the air back down after its  been heated in the compressor will make it even more dense and thus more air/oxygen for the engine to mix with fuel and burn.  This is more power for the same engine without an intercooler.

Hans.

[This message has been edited by Hans (edited 11-21-2000).]

[This message has been edited by Hans (edited 12-01-2000).]

[-lynx-]

 

i have to disagree. First the air gets compressed, fuel is added later.

Technically you are correct nicklas. I still stand by the fact that it is the idea of cramming as much air/fuel mixture at the correct, most efficient burning ratio into the cylinder was the reason for developing of superchargers.

Their use in the airplane engines came later when planes started going higher and higher and the chargers were needed to maintain the power output as the air density dropped with altitude.

quote:

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lynx
13 Sqn RAF

[juzz]

niklas; by climb power, I meant 100% for both aircraft, ie: 1310HP for the G-6. Looking at the climbrates/powerloadings then, I figure the G-10 has the DB engine with 1430HP at 100%.

RAM; I think your answer is here already:
 

There was a BMW801 project running for a high altitude version.
At the end of the war BMW didnīt had the production capacity or the difficult situation didnīt allowed a production.


The 801J was ready to be tested in flights (Ju88D) in 1943 with a turbocharger. It had a critical altitude of 38k feet. Though it was never used for fighters, the Ju388 got it at the end of the war.

801 TM, TN , TQ1, TQ2, were all projects of the bmw801 as a high altitude engine, but never were build in serial production.

In 1944 they also had the bmw805 engine, later they changed it and used many parts of the 801 and called it bmw801TR. Critical altitude in 35k. Again they had no capacity AND the Jumo213 and DB603 engines were avaible, so there was no need for it.

[niklas]

i put up a 5 pages to read. They were written in december 45. The RAF made a little review of german engines. Quite interesting to read imo

 http://people.freenet.de/luftwaffeln/flight_geng.html

juzz i think i know why the rated altiutde is lower at cruising setting for the db605 compared to battle setting. I believe itīs because cruising setting means also less RPM for the engine, what affect the effectivness of the supercharger.

niklas

[senna]

One thing is for sure, you cant just engage WEP right after takeoff or even during it if you want to keep your engine running. Engine/fuel/boost management was a very important part of flying a prop plane. Getting the most out of engine management was one of the fundamental difference between pilots.

-- senna

 

Originally posted by Luke Skywalker:

 I know a lot about TIE fighters, but my knoledge about WWII planes is limited, to say the least. Well, not so about planes but about engines.

I own several books about piston engined fighters, and after reading them I have to ask this thing:

How does a piston engine work?

Ok, I know, the engine moves a shaft and the propeller, linked with the shaft, spins. But beyond that my knowledge is nil.

What is a supercharger? what is a single stage supercharger? what is a (X) speed,(Y) stage supercharger?...

What is the difference between supercharger and turbosuperchargers?...

I get completely lost after reading things such as that a Dornier 217 version had two DB603 on the wings and one DB605 in the fuselage to feed the superchargers?...

Then we reach the next question...I understand that water and water-methanol injection make an engine run with increased power...what I dont understand is how does it work. Will an engine run smooth with the injection on until the plane runs out of booster?...

And another thing, what is the use of that little scoop the Bf109 has in the side of its engine?.

I know, are a lot of questions...but I know a lot about hyperdrives and ion propulsion systems, I had no piston engines in Tatooine to work with  

[Darth Vader]

Just give in to the dark side already.

[juzz]

Great stuff niklas