Round exhaust exits vs fishtail

The theory is that fishtail creates better rearwards thrust.



P-51
http://www.grubby-fingers-aircraft-illustration.com/images/Mustang_VH-JUC_36_med.jpg


109
http://www.adlertag.de/bilder/f4trop_kanada/frontre2.jpg


A slightly better shot can be found in here.
http://www.ipmsstockholm.org/magazine/1999/10/stuff_eng_detail_bf109g10_fuselage.htm

 

Why don't you just grab that rock hard Messerschmitt cock of yours and break it off? How much thrust do you think engine exhaust is really going to make? It looks like they built the exhaust of the 109 like that to A) make it more aerodynamically sound (reduce drag some trivial amount), and B) possibly reduce the exhaust flare for night operations (Remember: Britain bombed them at night). I do think you would make more thrust with that big fan up front if you didn't have the restrictions in the exhaust ports.

 

Don't bother with this guys threads mumble, he is more obsessed with proving german stuff is better than anybody elses, it's like listening to Henning Wehn He brags about German stuff so much and puts down British stuff and everybody elses stuff so often you need a chartered accountant to keep up with it.

 

WTF
Herman ain't German. He is what we call, in Canada, a DP
I was once honored to watch a bunch of hardy Canucks [my grandad, dad and a couple uncles] explain to a DP like Herman what is up.
We were hunting. Looking for a moose [or two even].
Herman the German never shut up. He would yap about the crappy highways to the watery beer, the lazy women, the inept service, the bad cars.
Herman got humbled. Herman got left in the bush, a couple miles from the road out of there. A place called 118 Mile, yep, that's what the sign sad. Nobody lived there, just moose and bears and stuff.. 118 mile.
I was little, I just watched and kept quiet, to many armed men there, a few of them fought and beat the Germans twenty years earlier.
Left the guy in the bush. We Cancucks left the DP with his VW Van, abandoned him. Fucked off up to 135 Mile and got our moose...
He made it out okay. But he didn't get a moose. We, the canucks got one. Ate it too. My grandad smoked some of it. Made sausage. About 500 pounds of sausages. Herman didn't.

OH this was about stacks?
sorry. I got mixed up, confuse em with racks. Too late to change this story. So I won't. Just ignore it.

 

Well said Bro. Mumble.

 

Nice pile of .... "information".

Now go back to what the Spitfire engine people did with the "fishtail" exhausts".

The exhaust stacks have nothing to do with thrust.

It has to do with boundary layer augmentation and exhaust extraction.


They found out (try "Boundary Layer Theory" by Hermann Von Schlichting- get the pre-ww2 copy in original German if you can.) that adding energy to the boundary layer or extracting the air at the boundary layer at areas where the boundary layer starts to separate reduces the drag significantly.

Most of those engines had twin exhaust valves in common ports and exhaust flow was not that great. The pinching effect changed the boundary layer, quite possibly smoothing-out the exhaust flow- increasing gas velocity to the point where the boundary layer was changed reducing the drag and also "pulling" the exhaust from the cylinder head.

Notice on P-51 the oil cooling exhaust air is ported to where the boundary layer is expected to separate.

Notice the radiators changing in P-38s and air intakes in later models that got more wind tunnel time.

Notice the Tempest and Typhoons also air intakes being moved about.

Yes, another way of saying it: lowering the drag increases "thrust" as the drag to thrust ratio changes.

If you continue the research you arrive at the discovery of the scram-jet, the UFO and 20 mach aircraft... well not-so-much-air craft.....

Even now you there are some places you could get arrested and some places get shot for saying certain words....

I could tell you... but that would spoil it...

 

Wow, thanks for the warm reception. The Spitfire as well switched from round to fishtail exhausts. I'm sure you'll find other examples of this as well. As to the accusations, I'm a nuts & bolts type, haven't got time for agenda & politics if the type described above. Peace out perhaps its time to say.


http://en.wikipedia.org/wiki/Supermarine_Spitfire_(early_Merlin_powered_variants)

Starting in early 1941 the round section exhaust stacks were changed to a "fishtail" type, marginally increasing exhaust thrust




Ejector exhausts
Merlin 55 ejector exhaust detail, Spitfire LF.VB, EP120The Merlin consumed an enormous volume of air at full power (equivalent to the volume of a single-decker bus per minute), and with the exhaust gases exiting at 1,300 mph (2,100 km/h) it was realised that useful thrust could be gained simply by angling the gases backwards instead of venting sideways.

http://en.wikipedia.org/wiki/Rolls-Royce_Merlin

 

As you are a "nuts and bolts" kind of guy, then you must know that passage in wiki about "thrust" is pure bullshit. That has to be written by some grade school kid or old WW2 propaganda agent to promote the great myth of British high tech..

Read that book. and some of the NACA stuff that should be available by now.


that hot exhaust from the engine did not produce thrust in itself no more than you drive your car a top speed and aiming a light ahead of you make the photon travel faster. nor shooting a gun behind you make the car travel faster in any measurable way.

It was all about adding energy to the boundary layer and reducing drag.

and the effect causing the exhaust gases to be "pulled" from the cylinder head, aiding in the volumetric efficiency of the engine.

 

Ha. Listen to looseleaf. The fuckin guy didn't make up his pseudo, he earned way back in the day when he got smarter than everyone else. He was 7.
Her is smarter than me, and I am one fucking smart guy.
[just kiddin. Kinda.]
This is interesting, guys!
I think we ought to have NO ICONS. Just a dot, for those with shitty graphics......
....
,....
never mind. It is pension day. I am drunk

 

The supercharged aircraft engine had another way of making use of this unspent energy - ejector exhausts which added forward thrust. This was why companies like "Rolls Royce"...

Roger Bywater, AJ6 Engineering.
Dennis Priddle, AJ6 Superchargers.


http://www.jagweb.com/aj6eng/supercharging_article.php

 

You are so unbelievably incorrect that it would require a complete lack of basic physics to sell that rhetoric.

 

The exhaust gases from a piston engine in no measurable way of Newtonian physics can cause the propeller driven aircraft to go faster.

The exhaust gases do NOT create thrust in that way.

Those gases energize the boundary layer and that reduces drag.

The thrust to drag ratio is improved.

 

Then all the aircraft designers of the day were wrong? I think I'll stick with them & the PHDs.

this model had the improved Sakai 31 engine with ejector exhaust stacks to augment thrust, http://www.chuckhawks.com/zero_A6M.htm

As it turned out, exhaust thrust was very important.
A well-designed jet (ejector) exhaust system can capture a considerable amount of this energy, and can easily increase rated horsepower by 10 per-cent or more. At 25,000 feet a 400-mph airplane could expect a gain of around 20-25 mph… and it cost almost nothing.

http://www.wwiiaircraftperformance.org/p-38/p-38-wayne.html

 

Because the exhaust system aids in engine cooling, the limiting factor in these aero engines, thus allowing the increase in boost/manifold pressure which allows for the extra horsepower. This extra horsepower is where the extra thrust comes from, not the exhaust flow itself. The extra power equates to the increase in speed.


The whole reason these "fishtail" exhausts were created was to help diffuse the exhaust flow and angled such that the boundary layer would act as a vacuum to pull the exhaust gasses away from the cylinder cranium. It was designed as a cooling aid, at first, to reduce the flare caused by unburned, raw fuel present in the exhaust for night operations. They discovered this effect was much greater than expected, so it was applied to most every aircraft since that application in order to grant increases in boost/intake manifold pressure in order to get more power from the engine. The point never was to generate thrust from exhaust gas flows.

In order to do that, precisely the opposite would have to occur, where the exhaust exit would be crimped in order to reduce it's area, rather than increase it with the fishtail flare, and focus the energy of the exhaust flow, which would restrict the mass air flow through the engine, thus reducing it's power, efficiency, and a great deal of the thrust you speak of. You just can't get enough of a mass air flow out of the exhaust of a piston engine as you can generate with the propeller spinning up front.

 

Brother Mumble....


"In the Country of the Blind the One-Eyed Man is King"


You are the king of this thread...

 

No, not all. but some, yes. You may not have heard of the stories about how the British "phds" who read "Boundary Layer Theory" started experimenting with BL augmentation controls and as they did not understand the reasoning behind the theory made great errors to the point they deemed the study worthless and abandoned the entire research.

This small act by some of the greatest Phds in England at the time put England last in all the WW2 aircraft technology. England never recovered.

Americans and Germans and Italians, French, Japanese and Russians stole their lunch money.

The British aircraft industry went down the toilet.. er Crapper courtesy of their old boy Explorer Club system ....


Having Phd does not make you smart nor always right.


Please take note of what I said about "Newtonian" aspects....

 

http://www.hark.com/clips/pgbrgqqrjh-respect-the-cock

 

Yes, you said Newtonian physics doesn't match up with all these engineers & PHD's, but did not eludicate in any way shape or form that argument.


North American understood boundary layer, which is why the belly scoop is couple inches apart from the fuselage, same for 109 supercharger scoop.



http://en.wikipedia.org/wiki/Dewoitine_D.520

incorporating exhaust ejectors for added thrust,

 

"added thrust" is a misnomer.

If the drag is reduced, if the exhaust "ejectors" contribute to the volumetric efficiency of the engine and results in more horsepower, the effect is "more thrust".

However if you believe that the angled, fish tailed exhaust ends cause a jet propulsion, increase in "thrusting" the aircraft forward, you are mistaken. (Newtonian theory of force and counter force.)

Put a fish tail exhaust on your car. Put the car in neutral and rev your engine to red line , see if the thrust from the exhaust moves the car forward.....

Now get your car up to.. say 160 kph. Put the trans in neutral and keep the revs at max rpm. See what speed you car holds by the thrust of the exhaust.

Don't be worried that your car comes coasting to a stop.....

 

that's what I'm talkin' about !!!!