2012 Exhaust Blowing & Coanda

[marcush.]

General comment>>

....

wouldn´t a high performance engine get more than 100% cylinder filling?

[kilcoo316]

It's not, at peak power rpms I'd expect it to be a little more.

Yeah - its approx - I didn't include overfill.

[hardingfv32]

Where is your exhaust velocity figured located, exhaust port or exhaust pipe tip/opening?

The exhaust temp at the exhaust port is 850 C and 150-200 C at the exhaust tip/opening?

I also find it odd that the velocity does not seem to be affected by the exhaust system geometry. Are you claiming that that routing the exhaust flow though bends has no effect on velocity. Why do the calculation lack any input for the exhaust system layout?

Brian

[Ferraripilot]

wouldn´t a high performance engine get more than 100% cylinder filling?

No. Getting to 95% is quite an achievement. The volumetric efficiency of an engine is naturally poor. Positive cylinder filling (over 100%) is only achieved through forced induction or illegal fuels. Maximizing thermal efficiency is even more difficult so I believe the above estimation kilcoo316 made to be overly generous.

[Ferraripilot]

Where is your exhaust velocity figured located, exhaust port or exhaust pipe tip/opening?

The exhaust temp at the exhaust port is 850 C and 150-200 C at the exhaust tip/opening?

I also find it odd that the velocity does not seem to be affected by the exhaust system geometry. Are you claiming that that routing the exhaust flow though bends has no effect on velocity. Why do the calculation lack any input for the exhaust system layout?

Brian

An engine designer will tune the engine according to the backpressure the exhaust manifold places on the system. For instance I have no doubt the engine mappings are different this year compared to last with the EBD. This in essence means the port velocity and exhaust backpressure from the manifold directly effects the intake breathing and in turn exhaust breathing. I've no doubt the volumetric efficiency and thus tip velocity is slightly better than last year but still not enough to make a difference considering how far the system has to blow to seal the diffuser. The numbers quoted above are definitely not port velocity figures. I still believe this system is not very good compared to Mercedes system but I suppose we will find out. Too much of a compromise to coke bottle section flow.

[hardingfv32]

No. Getting to 95% is quite an achievement.

Up to 115-130% normally aspirated is possible with a good intake and exhaust system.

Brian

[hardingfv32]

I've no doubt the volumetric efficiency and thus tip velocity is slightly better than last year

I see no reason why it would have changed?

I still believe this system is not very good compared to Mercedes system but I suppose we will find out. T

I do not see how we will ever find out with all the other variables that affect the car's performance.
It is assumed that RB had the best exhaust system last year, but that can not be proven. We have no idea if some other feature made RB the best car last year.

Brian

[strad]

Up to 115-130% normally aspirated is possible with a good intake and exhaust system.

Brian

Brian..I'd love to see how you come up with that..You or somebody earlier pegged it at 125%...From my experience I just ain't buying it..Without a blower I can't see it.

[PlatinumZealot]

Ok I will check it out.

I made a small mistake on the reading. There was a small trip in the flow during the iterations and the progam left the max value displayed.

I did a surface parameter check and the velocity at the exit pipe is 209 meters per second.

These are some parameters at the exhaust pipe.

Notice I used the mass flow rate as the input.. because Williams gave a "Normal Liters per second" of air of 450 for the whole engine. I can't use this value as the output of the exhaust pipe.

Calculated results on the exhaust tip.


Mass Flow rate = 0.27 kg/s (I chose this value as the mass flow rate going though one bank of the engine at normal room temp and pressure conditions).

Area = .00593 m^2
Mass Flow Rate [kg/s] 0.27
Pressure: 1.0067 bar
Density: 0.292 kg/m^3 (at normal conditions this is 1.225 kg/m3)
Velocity = 209.74 m/s
Mac number = 0.31
Temperature = 926*C (I think this is fluid reheating)

Volume flow rate: 0.924 m^3/second

Notice that the volume flow rate is much much higher than the 0.225 m^3 per second at normal conditions due to gas expansion.

How much does the fuel add to the mass flow rate? Is it negligible?

It increases the mass flow rate. It is not significant for most "every day" calculations.

But you can go into the intricacies -

Because the chemical reaction that occurs in combustion, Oxygen is replaced with CO2 in the exhaust air - you have to go into details of that. So what you would do instead of using "Air" as the material selected at the exhaust exit you would create a custom material called "exhaust" with the appropriate fractions of Nitrogen and Carbon dioxide, unburnt fuel vapours, CO etc and use that as the gas at the exhaust exit. The mass flow rate you can calculate - so you use that.

[dren]

No. Getting to 95% is quite an achievement.

Up to 115-130% normally aspirated is possible with a good intake and exhaust system.

Brian

Yes, the shape of the intake aids in this.

[marcush.]

No. Getting to 95% is quite an achievement.

Up to 115-130% normally aspirated is possible with a good intake and exhaust system.

Brian

that´s how i see it.WOT full load conditions of course.We are not talking about efficiency but ability to use the inlet and exhaust as a tuned wavesystem ....

[Ferraripilot]

No. Getting to 95% is quite an achievement.

Up to 115-130% normally aspirated is possible with a good intake and exhaust system.

Brian

I've never heard of that without forced induction.

Tip velocity increases proportionally with volumetric efficiency. VE is increased this year due to less back pressure, and this is per Renault advising the new exhaust regs have afforded them slightly more power. So more VE = more air which means more volume being pushed through the same sized port as last year which means more velocity.

[hardingfv32]

VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

F1 engine: 755 BHP @ 1900 RPM, 146 CI (2.4 L) BSFC .5 (optimum)

I think you get 128% VE.

Brian

[strad]

edit
You may be right.. I didn't really think it possible but my engine builder assures me we get at or over 100%.

[NonNewtonic]

VE = ( 9411 x HP x BSFC ) / (DISPLACEMENT x RPM)

F1 engine: 755 BHP @ 1900 RPM, 146 CI (2.4 L) BSFC .5 (optimum)

I think you get 128% VE.

Brian

I like to point out that the rev limit of the current engine is 18000rpm