Volumetric Efficiency.

[Caito]

I was reading the news in f1 technical, in which it says:

How much air does the engine admit at maximum revs?
"At 18,000 rpm, the engine admits around 450 litres of air per second - which would equate to 27,000 litres per minute at maximum revs. By way of comparison, a Mercedes-Benz C-Class Estate has a load capacity of 485 litres."

So,


18.000rpm == 300 rev/s

Every 2 rev, we have the 8 cylinders filled once.

150 complete cycles/s.

There are 2.4l so a Volumetric efficiency of 1 would mean

150 x 2.4l = 360 lit/s

The article claims around 450 liters/s

450/360= 1,25

Am I doing something wrong, or it's really 1,25?

I thought it was too much to be naturally aspirated. Though it's probably speed dependent(RAM, air box with higher pressure at higher speeds).



Some more numbers.

At sea level and at 15°C according to ISA (International Standard Atmosphere), air has a density of approximately 1.22521 kg/m3

450l means 0.45m3 which means 0.551kg/s which also means 33 kg of air per minute.

If that 0.551 kg where thrown vertical at 100km/h that would equate to 15.3 kg of downforce. Rather useless? Do exhaust gases move at the speed of sound? That would be 185 kgf, which could be thrust, downforce or combination, though I doubt it.






Pole on 2010 (Vettel) 1:34.558

Let's put 1:35 for this year( really don't know, Australia was faster, then it was slower...)

24.000 rotations in 95 sec = 15158rpm average for a 62% wot lap.


Too much for the moment:P


bye!

[PlatinumZealot]

How did you calculate down force from that?

The volumetric efficiency has to do with the momentum of the air from the air box through the throttle bodies in addition to the acoustic effects.

I like to visualize it as pouring a jug of my favourite drink. You pour a glass full then lift back the jug. There will still be liquid coming down into the glass because the drink that was in mid mid air was still moving when the jug was pulled away. So you end up with an overflowing glass of juice. Of course an engine doesn't "overflow" because the air is compressed as it rushes in, and there is still more air behind that pushing from behind (Especially when the engine uses pulse tuning).

[Belatti]

Long time ago I have a discussion with a forumer about volumetric effciency. He told me he was an F1 "insider" and that they couldnt reach the levels you calculated.

I have an ASME paper from 2006 about the 5 to 1 junction of a Renault F1 V10 engine is simulated and measured, the graph shows 120% peaks...

[Caito]

How did you calculate down force from that?

The volumetric efficiency has to do with the momentum of the air from the air box through the throttle bodies in addition to the acoustic effects.

I like to visualize it as pouring a jug of my favourite drink. You pour a glass full then lift back the jug. There will still be liquid coming down into the glass because the drink that was in mid mid air was still moving when the jug was pulled away. So you end up with an overflowing glass of juice. Of course an engine doesn't "overflow" because the air is compressed as it rushes in, and there is still more air behind that pushing from behind (Especially when the engine uses pulse tuning).

Well, I supposed that air can't be accumulated in the engine. So, all the air that goes into the engine must go out.

If 0.5kg/s enter, then they must get out. If you multiply kg/s by speed at which it exits you get force. If someone knows the velocity of the exhaust gases it could be a better number. Although the heat also affects and etc etc.

Long time ago I have a discussion with a forumer about volumetric effciency. He told me he was an F1 "insider" and that they couldnt reach the levels you calculated.

Then I'll guess it's possible

[dren]

I read somewhere the VE of an F1 engine is over 100%. The intake is designed to slow down the air which increases its pressure. It's not about air speed ramming into the cylinders, it's about manifold pressure before the cylinders. A higher than ambient air pressure in the intake manifold would allow VE to be greater than 100%.