flying car company in Edmonds, WA

[freebeard]

Exhaust driven cooling airflow? It's a rocket bell. I saw a b&w pic out of an old Popular Mechanix Illustrated from the 50s that had a Porsche race car with a similar system.

My own design uses cooling air into a Coanda nozzle.



If it was cut down to what's behind the tail lights and inject air at the leading edge, it would mimic the Jetoptera design. Plus there would be a sight-line for the rear view.

[redneck]

.

Came across this today and immediately thought of this thread.

Though not as cool or useful as your example.

The takeoff, looks exciting.

https://www.youtube.com/watch?v=LTog-mTg2js

Another angle.

https://m.youtube.com/watch?v=-tnqMpz-EIQ

He did manage to stick the landing though, so....


Carry on...





>

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[kach22i]

Originally Posted by samwichse

Another pic, this one down the ejector cooling, just because I like it

If you like it, must mean you understand it.

Please explain it to me, what am I looking at?

Tatra 603
https://www.flickr.com/photos/davydu...61128/sizes/l/



ECORRA - gallery Tatra 603 B5 - Ejektorový motor



https://www.flickr.com/photos/andreboeni/48986852172/


Does the exhaust drive the fan and pulley assembly, or does the fan/pulley drawn more exhaust out?

The specific shape, that of a U or a V from a O.............what advantage, what rules of physics at work?

How is this better than just a smaller O?

How is this different/better than the Tatra 603 B5 - Ejektorový motor megaphones (orange car page -2)? See below.

http://www.ecorra.com/en/galerie/pre...&off=12&page=2

[freebeard]

^^^ That is quite the engine stand.

[samwichse]

Originally Posted by kach22i

If you like it, must mean you understand it.

Please explain it to me, what am I looking at?

I think the confusion is that the the ejector Tatra has no cooling fans. They replaced the cooling fans in their low-dual stock position with the two ejector tubes around the star shaped exhaust outlets. The high speed exhaust entering the ejector draws air in the base of the ejector. The fans aren't involved.

If you look at this image, you an see the blocking plates around the ejector exits where the slightly larger fans once were, and the ununsed pulley that drove them:



They supposedly gained ~20hp by eliminating the fan drag, but it was loud, and I assume it didn't work as well at low speed/idle so it wasn't something used outside of race cars.

[aerohead]

* the compressor requires 1.25-megawatts/ hour net energy input for level flight cruise, of unknown velocity which matches drag equal to a maximum 3,000- pounds thrust.
* @ 55% thermal efficiency maximum for an aviation gas turbine, requires 16.835-gallons JET-A ( 135,000 Btus/gallon )[ 2.272727- megawatts gross ] /hour.
* with the forward thrusters tucked into the fuselage, the majority 'laminar' flow claim seems reasonable. She's a 'pusher' plane, with no propeller slipstream contaminating the canard, forward fuselage, and forward box-wing.
* more efficient than a 'turbojet' small plane ( in an era when turbofan engines are the benchmark ).
* faster than a 'helicopter' ( no comparative data provided )
* up to 15-X air multiplication ( they use a 'static' Toshiba-Dyson fan as a comparison to a 'dynamic' airframe ).
* for FAA certification, Jetoptera would have to demonstrate flight control in a power-off / hands-off flight scenario, and be able to self-recover from spin , stall, and land as a fixed-wing ( as auto-rotation is obviously impossible ). Canards would have to deploy without power, and without the forward propulsors. STOL would be impossible. The plane doesn't appear to have any brakes, which would be necessary with very high stall speed, landing speed. Emergency fuel dump would be a good idea. If not a all-aircraft parachute system.

[orange4boy]

Laminar flow on an aircraft is helpful but at our level of mastery, it is not going to allow for revolutionary increases in efficiency.

So the thrust is augmented by 15x

"15-X air multiplication" does not = thrust multiplication. It's meaningless without an efficiency factor. I don't see how this tech is any more efficient than current tech. How much of a penalty comes from ducting all that high pressure air into the nozzles. My guess is it's pretty high loss.

Semi-educated judgment: Vapourware.

I want to believe but I don't want to be duped either.

I've always been a fan of Coanda (and Bernoulli)

Pun intended? Shouldn't it be: "I find the work of Coanda and Bernoulli highly entraining."

[freebeard]

Pun intended?

Indubitably.

[seifrob]

In replay to Tatra ejectors (sorry to hijack a thread)

Samwichse explained it nearly all. As Tatra was air-cooled V8, they relied on two fans to cool the engine. (The drawing shows stock engine.) In this modification they replaced two fans with ejectors to draw hot air away from the engine, gaining 20 hp. The project was cancelled because of 2 reasons: The system was too loud to be allowed on some races, and (more importantly), in 1968, one year after this car was built, Soviet tanks came and everbody here had other problems than to practise motorsport.

( you can listen to the engine sound here : https://youtu.be/sUaqqNU_WhE?t=287
compare to stock version here: https://youtu.be/sUaqqNU_WhE?t=118

Originally Posted by kach22i

The specific shape, that of a U or a V from a O.............what advantage, what rules of physics at work?

How is this better than just a smaller O?

As far as I know, the amount of "slipstream" being carried (pulled? drawn? generated?) by fast stream of moving air depends both on velocity (see bernoulli equation and pressure differential) and "surface" area that two gases (moving and not moving) are in contact.
What you see here are four exhaust tubes that needed to be:

1. packed together to have a reasonable size
2. have small cross-section to increase velocity of the exhaust gasses
3. have large circumference to maximize contact with mass of not-movig air

were it just "small circles", it would have not so favourable cross-section/circumference ratio.

This was not first Tatra venture into ejector cooling. They made monopost Tatra 607 in the 50´s (Tatra 607 F1,Formule 1, construct, okruhy, závody, grand prix | Constructors F1). (Unfortunatelly I am not aware of any similar Porsche design from that era.)

[seifrob]

In reply to OT:

- their webpage ( Jetoptera | Revolutionary Propulsion System ) promises first prototype of drone J-220 for practical use in Q1/2020 (here) since that not a postpone message, not a "due pandemic we didnt manage" note. Strange.

- here: GlobeNewsWire they announced sort of partnership with VZLÚ, which is our aerodynamic research lab. I guess I will try to ask VZLU press office for details (nothing on their webpage)