gruntguru wrote: ↑
Fri Dec 02, 2022 1:02 am
saviour stivala wrote: ↑
Fri Nov 25, 2022 4:32 pm
Tommy Cookers wrote: ↑
Fri Nov 25, 2022 3:33 pm
the above is incorrect ......
unless the exhaust gas is entirely diverted away from the turbine and the main exhaust pipe
the turbine actually gets 1 atm exhaust so kinetic pulses/waves still (quite weakly) power the turbine and compressor
this power recovery-without-backpressure is the so-called blowdown recovery
here it somewhat reduces the amount of ES energy needed by the MGU-H in driving the compressor
so increasing the available duration of this ('electric supercharge') running mode
there is no evidence that the turbine responds only to mean exhaust pressure (is unresponsive to kinetic 'pulses')
clearly all 4 makes of ICE have exhaust manifolds designed to encourage these pulses
and the pulses are anyway relatively stronger in 1 atm exhaust than in the main ('backpressure') running mode
It is your accredits which are wrong. First. Any exhaust gas past the exhaust valve is 'blow-down' gas. Secondly. The turbine used in F1 is not a blow-down turbine like used by the Wright Cyclone, but a pressure turbine. A blow-down turbine will not have a waste-gate because it doesn't need pressure to produce useful work. The F1 turbine needs exhaust gas pressure to produce useful work, when waste-gate/s are opened the exhaust gas pressure is dropped to atmospheric pressure, and any gases inside the turbine at atmospheric pressure cannot make the turbine do any useful work because turbine can only do so under exhaust gas pressure.
With wastegate open, the pressure in the exhaust does not drop to atmospheric. Have you ever heard of wave tuning? The exhaust collector sees pulses of up to 2.5 atmospheres on a NA engine - higher on a supercharged engine. Are these pulses able to force their way into the rapidly spinning turbine and generate any power with the wastegate open? Who knows. Certainly there will be some partially-open settings for the wastegate where useful turbine power is generated while reducing average exhaust pressure sufficiently to increase crankshaft power.
One thing people are forgetting here is where the exhaust and wastegate dumps, is not at atmospheric pressure, as it will be less, and will vary with vehicle speed. Also, probably part of what Ferrari is doing is using the exhaust stream to help scavenge the waste gate stream. Running it in the exhaust will likely be easier to tune around as the pressure in it will likely vary less than the beam wing area. It’s almost like those exhaust breather systems… they can pull a small amount of vacuum when done right.
Everyone has to remember, underflow aero really works a lot better because of the pressure drop the rear wing causes. There is a big pressure drop in the vicinity of where these exhaust and waste gate systems dump.