2014-2020 Formula One 1.6l V6 turbo engine formula

[saviour stivala]

OK. So now you have narrowed your wisdom down too ''A combined simultaneous 'pressure' and (im)'pulse aka turbine effects''.

[gruntguru]

Dividing exhaust runners for as far as possible, then collecting the runners in groups of 3 or less evenly-firing cylinders is a sure sign that the design is focused on making maximum use of the blowdown pulse energy. This is evident in the use of a divided turbine housing which keeps overlapping blowdown pulse separated right up to the turbine wheel.

A 100% pressure (reaction) turbine would not display these design features.

No the F1 turbocharger is not 100% driven by blowdown energy (neither was the Wright TC although it came very close). The F1 turbine does generate a significant proportion of its power from blowdown energy. Even the early log manifold Mercedes engine was harnessing significant blowdown energy at certain rpm by keeping interfering pulses separated right up to the turbine wheel. (interference would occur at certain rpm due to unequal lengths of the three grouped cylinders)

[saviour stivala]

Designing to make use of ‘blow-down’ pulses or not, three exhaust runners from each bang of cylinders of constant cross section and length, as used by F1 turbocharging system being joint together into a collector with said collector pumping exhaust gasses into turbine scroll, said collector will change exhaust blow-down velocity energy into pressure energy. Because the turbine is than rendered as a pressure energy turbine, unlike a blow-down energy design, the exhaust gasses will need two paths out, one path through the turbine and the other to atmosphere through a waste-gate. When waste-gate (second path out) is fully open, exhaust gasses pressure energy is rendered at atmospheric pressure, with exhaust gasses rendered at atmospheric pressure, no energy recovery by the turbine is possible. But with the formula 1 turbine rendered unable to recover any energy, it, the turbine, also eliminates the impacting of exhaust gasses pressure on cylinder scavenging, because the F1 turbocharger can also be run in ‘electric supercharging mode' with exhaust gasses at atmospheric pressure, it, ‘’ free load mode’’ makes the extracting of maximum power output from the power unit possible.

[hollus]

...When waste-gate (second path out) is fully open, exhaust gasses pressure energy is rendered at atmospheric pressure, with exhaust gasses rendered at atmospheric pressure...

I am going to focus on this one item only, if that is OK. How can the wastegate achieve atmospheric pressure at the engine? First of all, as far as I know, no pipe ever is free of backpressure. But more specifically, the wastegate pipe or pipes are of lesser diameter than the normal exhaust, so they can only be less effective than the normal exhaust in allowing the gasses a nice passage out.

I am not an engine person, so I might be completely missing the point, of course.

[saviour stivala]

Since you chose to drop-in on the subject. not being an engine person you are missing the point. When waste-gate/s are open exhaust gas pressure energy is rendered at near atmospheric pressure and with exhaust gasses at near atmospheric pressure the result will be (1) the impacting on cylinder scavenging will be eliminated and (2) no energy recovery by the turbine is possible.

[hollus]

How much gas can really get through the small red circles? I see how they can alleviate the pressure, but I fail to see how they can eliminate it when the normal flow requires the larger pipe.

[saviour stivala]

Nice pictures, thanks. The small pipe/s are exhaust gasses out of waste-gate/s. As such there should be no doubt that waste-gate/s in/out and the pipe/s volume capacity would have been appropriately designed/selected to fulfil the aim of rendering exhaust gas pressure as near atmospheric pressure as possible when waste-gate/s is/are fully open.

[hollus]

...the aim of rendering exhaust gas pressure as near atmospheric pressure as possible when waste-gate/s is/are fully open.

That's your statement. It does not mean that it is the designer's or the regulator's aim. If fact it would make sense for the regulators to make them safety elements rather than performance elements. Which of course might or might not be true.

Anyways, the maximum diameter of the "red circles" is specified in the regulations. So if it were inappropriate for that function, the teams would still be stuck with it.

[saviour stivala]

Those nice exhaust pictures. Have you noticed that the single waste-gate pipe is bigger in diameter than the twin waste-gate pipes. The article where those pictures were extracted from, although not of much help to the subject at hand, is a good article (how f1 exhaust works. By Gemma Hatton).
Also. Interesting read. (2016 regulation change allowing up to three exhaust pipes. By Steven De Groote).

[hollus]

The maximum diameter of the waste-gate pipes in not regulated. Indeed, my bad. The combined are of the exits are, resulting in a larger diameter for a single pipe.
5.8.3: "The cross-sectional area of the turbine tailpipe exit at the rearmost point of the turbine tailpipe must lie between 7500mm2 and 14000mm2, and the total cross-sectional area of the wastegate tailpipe exit(s) at the rearmost point of the wastegate tailpipe(s) must lie between 1590mm2 and 2375mm2. If there are two wastegate tailpipe exits they must be equal in area."

AFAIK all teams choose to run the smallest possible "turbine tailpipe", with a brief exception from Ferrari a few years ago, quickly corrected. And AFAIK, all teams choose to run the largest possible wastegate tailpipe(s).
There are no obstructions in the wastepipes, unlike in the normal exhaust, but still, that area ratio...

Anyways, right or wrong, my point is laid out. I should stop now, not wishing to drag the subject for too long.

[saviour stivala]

Not wishing to drag this subject for too long, as you wish.
But one last thing if I am allowed. Example:- a 4 inch pipe from turbine will carry a capacity and velocity of flow as 5.7 two inch pipes. Why is the turbine pipe carrying capacity chosen to be 5.7 times that of single waste-gate pipe?. Because when waste-gate is fully open exhaust gas pressure energy is as near to atmospheric pressure as could be, while when waste gate is closed exhaust gas pressure after turbine needs as much free flow as could be provided to minimize the negative effect of cylinder scavenging.

[godlameroso]

Aside from brief moments where maximum engine power is needed why would you run the wastegates fully open? The majority of the time, the power units are varying wastegate pressure relief(MGU-H harvesting is a priority after all). Wouldn't this indicate that under regular operation this is a mixed flow turbine? Not solely pressure driven, not solely pulse driven.

[gruntguru]

Yes. My previous post was not considering ES (electric supercharger) mode at all - simply pointing out that the F1 turbine operates using a combination of energy extracted in two ways.

1. Elevated average exhaust pressure (with associated pumping loss during the exhaust stroke)
2. Blowdown energy. Applying the higher-than-average pressure pulse (which travels down the runner when the exhaust valve opens and the piston is still travelling downwards on power stroke) directly to the turbine wheel. This is free energy with no associated losses in the piston engine.

[Tommy Cookers]

Designing to make use of ‘blow-down’ pulses or not, three exhaust runners from each bang of cylinders of constant cross section and length, as used by F1 turbocharging system being joint together into a collector with said collector pumping exhaust gasses into turbine scroll, said collector will change exhaust blow-down velocity energy into pressure energy.....

(further to Wright's practice and NA and turbo F1 race engine's practice suggesting otherwise) ....

Morrison & Smith's book 'Scientific Design of Exhaust & Intake Systems' shows otherwise (Page 99 paperback 3rd edition)
John C Morrison BSc PhD MI MechE having at Glasgow University 30 years of experience in this field
he specifically endorses these data .... showing ....
(as first presented in full Fig 3.19 by Colin Campbell MSc MIMechE in book 'The Sports Car - its design and performance')
data of which Campbell writes ....
'it is possible for pressure pulses and reflections to travel UP and DOWN the MAIN PIPE and its branches with very little interference'

ie pulses are fed to the turbine by the main pipe

[saviour stivala]

‘’It is possible for ‘’pressure’’ pulses and reflections to travel up <B> and down the main pipe and its branches with very little interference <B>’’. So you are saying that the turbocharger turbine as used in formula one is a ‘’pressure turbine’’, which means it is not a ‘’blow-down turbine’’ as per your original claim.