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
Quote:
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?
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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:
- packed together to have a reasonable size
- have small cross-section to increase velocity of the exhaust gasses
- 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.)