Where do you think the wastegate(s) are positioned to behave as you say?
Yes there are two possible paths. The question is, why does the exhaust stream choose one path over the other rather than using both? As I believe @Tommy Cookers pointed out the pressure at the end of both paths is atmospheric. So rather than an alternative path the open wastegate adds a supplementary path.saviour stivala wrote: ↑Tue Mar 01, 2022 9:00 am
Thanks for the link which clearly confirms what I have been saying namely that, the cylinders exhaust gases are convened to the pressure turbine wheel through a collector pipe, with two possible paths. Either through a waste-gate or through the turbine wheel.
Thanks. I stand corrected.gruntguru wrote: ↑Tue Mar 01, 2022 11:06 pmWith a radial inflow turbine spinning at high speed (courtesy of the MGUH) there will be significant pressure required for exhaust gas to flow through it. The majority of the exhaust will therefore pass through the wastegate with only high pressure pulses able to fight their way through. Axial flow turbines do not have this backpressure issue. Mixed (radial-axial) flow turbines sit somewhere in between.
???? The purpose of a wastegate is to control/limit boost pressure or turbine overspeed. There may be instances where a blowdown turbine requires a wastegate to control one or both of these.
It is quite common for a radial turbocharger system to be designed with no wastegate.
The radial pressure type of turbine, a design that does necessitates the need to incorporate a ‘waste-gate’ into the design set-up.
It is very rare to see a turbocharger system where exhaust pressure is reduced to zero. In almost all cases, the turbine continues to drive the compressor even while the wastegate is opened sufficiently to control the boost.
The pressure type of radial turbine design waste-gate can be used in one of two ways, a build-in (into the turbine housing) a design that can ‘only relives’ the exhaust gas pressure build-up inside the turbine housing. Or An external waste-gate, build into the exhaust piping supplying the turbine, this design set-up, when fully open will bypass exhaust gases away from the turbine, completely eliminating any exhaust gas pressure inside both the turbine and the collector pipe supplying turbine. With this waste-gate set-up, no turbine harvesting is possible when waste-gate is fully open. Because exhaust gases will chose to travel the path of least resistance.
It may be the case that F1 does not utilise any blowdown pulse energy during electric supercharger mode, but it is by no means certain. With appropriate turbine and wastegate design it is certainly possible and even 10 or 20 hp of capture would reduce the ES drawdown during electric supercharger mode and permit additional deployment.This answers the question of (why does the exhaust stream chose one path over the other?). So yes. Unfortunately I cannot agree.
If the wastegate plumbing or the orifice of the wastegate itself are not of sufficient cross sectional area, there will be a pressure drop and the exhaust manifold will not be able to reduce fully to atmospheric pressure.
If I've followed that correctly (and I may not have done!), you're describing a mode of operation in which you are electrically driving the compressor in preference to using available exhaust gas energy/flow. Why would you do that?saviour stivala wrote: ↑Thu Mar 03, 2022 9:33 pmThe turbocharging system used in F1 is different from that used by the majority of normal road cars. In F1 when the waste-gate is fully opened it is meant to reduce exhaust pressure in collector to zero. Because only with exhaust collector pressure at zero can the electric supercharging mode extract maximum possible power from the ICE. With the exhaust collector pressure at zero, the turbine wheel being fixed to compressor shaft, it is just getting a ride on shaft. As is the function of the waste-gate of a F1 turbo, it does not control boost, it makes sure that when fully open exhaust gas pressure in collector is zero. The exhaust stream of a F1 exhaust piping system from engine to turbo will chose the path of least resistance when waste-gate is fully open. End the least resistance path is through the waste-gate and not through the turbine. In electric supercharging mode with waste-gat fully open. The F1 turbo cannot utilise blowdown pulses energy because of a fully open waste-gate. And with waste-gate closed and turbine being powered by exhaust gas pressure. I doubt how much use it can make of blowdown pulse energy. This because as far as I know all four PU’S on the grid uses an exhaust pressure collector for a path for exhaust gases to turbine and not the proper exhaust piping conductive to make best use of blowdown pulse energy. ( 07 oct 2014 ‘’blowdown energy is free’’ by GR – To harness this energy the pressure pulse must be piped to the turbo without adding pressure to the exhaust of any cylinder)