marekk wrote:atmospheric pressure.ringo wrote:Where did you get that 1 bar value from?1 Bar at pipe's exit - please read a little bit more carefully.If it was just over 1 bar, a turbo charger would not work on any engine. Turbos work on pressure difference.
so the pressure directly from the exhaust port is not 1 bar.
This pressure is representative right as exhaust stroke starts.
As the exhaust stroke starts, there is just 1 bar inside - exhaust valves open long befor BDC.
You have to decide - exhaust pressure or speed. You cant have both at the same time in subsonic flow.
It's temp of exhaust on exhaust port. And not 3 times hotter - it needs to have just +33% energy.Explain also why BMW v8 exhaust is 950 degrees.
Is their engine burning 3 times hotter?
Actually flame temp of diesel is slightly higher than for light fuel.This lemans, and we know diesels burn cooler.
at exit due to the excess air creating NOx which has a cooling effect.n smikle wrote:Diesel makes colder exhaust.
n smikle wrote:[youtube]http://www.youtube.com/watch?v=B0Pnvgc2_gA[/youtube]
the exhaust is colder full stop.Raptor22 wrote:at exit due to the excess air creating NOx which has a cooling effect.n smikle wrote:Diesel makes colder exhaust.
at the exhaust valve the tmeperature is higher than for gasoline/petrol
Mere 2,000 times. For one CF6-80.Raptor22 wrote:I think the mass flwo there is SIGNIFICANTLY higher than a 2.4L v8 F1 engine
It was the easy part.shelly wrote:I suggest dropping diesel vs gasoline peak temperature discussion and focus on finding an agreement on exhaust conditions estimate.
We have fixed:
-mass flow rate aroun 0.20kg/s per bank
-energy content around 300kW per bank
We have to converge on:
-2 out of 3 between temperature, pressure and density at output section
-reasonable size of exhaust
Then we can move on to discuss exhaust gas behaviour outside
Green is 6, red is > 12. mass flow at constant density is proportional to speed.ringo wrote:Why is one slower by half?
Using that diagram light orange is 12 red is 15. 12/15 is not a half.
Secondly we do not know the nature of the bend or pipe diameter in the bend. It's simpler to assume the speed is the same.
mass flow is not what you say. Both still have equal mass flow.
Real flow is much more complex than this pictured one (not steady, much slower in boundary to pipe walls ...), and we don't know anything about pipes geometry and inner build jet, but it gives us an overview.shelly wrote:@marekk: I think we need an estimate of exit conditions before thinkinkg of exit path.
The picture you show is interesting; however as far as the thin wall in the middle of exhaust pipe is concerned, I am not sure that it is there for splitting flow: I have seen it on more than one f1 car in the 80s-90s and it can be ralated to structural resons of the pipe itself.
Anyway: do we all agree that exaust speed is 100+ m/s?