Mercedes Power Unit Hardware & Software

[johnny comelately]

Are y'all talking about the 5 outer vanes that are fixed and it is thought it is an iris throttle??
And that you want swirl going into a turbo?
Ice water, STAT!

[Tommy Cookers]

Closing the movable vanes when driver lifts throttle will increase turbo rpm for a given turbine exhaust flow because with no airflow the compressor have less work to do, when driver returns on throttle the turbo higher rpm will eliminate turbo lag.

the turbo rpm is continuously subject to the action of the MGU-H (because it's a synchronous machine)
we have seen (Honda) bench runs showing that pre-corner the MGU-H pulls down the rpm getting a burst of generation


... the vanes don't close to restrict the flow
they vary the airstream's angle (eg with compressor rpm) to control angle of attack at the compressor blades
the angle can be for max compressor output - or lesser angles so the blades do less velocity change as required
reducing output and load in good proportion

.. talk of 'iris throttles' (reducing compressor load on output reduction) as in a few WW2 planes ...
and the V16 BRM's intended so-called 'vortex throttling'
isn't it all the same thing ?

[saviour stivala]

Quoting – f1tech 2006 ‘’throttle body before turbo’’ 14 posts page 1 of 1 by trendy tramp.
‘’The spatial velocity across the inducer plane will have an effect upon compressor efficiency. A small amount of swirl can actually increase efficiency but this will only be at one point on the map. Generally the effects are detrimental to the efficiency and linear flow is desirable’’.

[saviour stivala]

Closing the movable vanes when driver lifts throttle will increase turbo rpm for a given turbine exhaust flow because with no airflow the compressor have less work to do, when driver returns on throttle the turbo higher rpm will eliminate turbo lag.

the turbo rpm is constantly controlled by the activity of the MGU-H (because it's a synchronous machine)
we have seen (Honda) bench runs showing that pre-corner the MGU-H pulls down the rpm getting a burst of generation


now everybody's talking about 'closing' the vanes - but the vanes don't close to restrict the flow
they vary the airstream's angle (eg with compressor rpm) to control angle of attack at the compressor blades
the angle can be eg for max compressor output - or some lesser angles reducing the output and load as required
reducing output and load in better proportion ie more efficiently than traditional things we normally call throttles

afaik until recently only fixed geometry was allowed .. (contrarily another thread says VGVs were allowed from 2014)
maybe the rules were then amended to enable elimination of the oil burn issue
now talk of 'iris throttles' (reducing compressor load power when reduced output is required) - as in a few WW2 planes
and the V16 BRM theoretically had the same concept - then called 'vortex throttling'
isn't it all the same thing ? (and rather new to F1 followers)

The turbo rpm is not constantly controlled by the MGU-H. one example is when the driver goes off throttle. When the driver gets back on throttle yes, but the higher the turbo rpm is when driver goes off throttle the faster the MGU-H can spin-up the turbo when the driver returns on throttle.
Although the BRM V-16 eye of the superchargers SU fuel injection and vortex throttle systems were both manufactured neither would ever be raced. One of the many reasons why the BRM V-16 was unsuccessful was the RR centrifugal superchargers.

[saviour stivala]

The BRM V-16 intended vortex throttling involved inducing variable swirl to the inlet airflow, and it was more complex than a camera iris. It was part of the original master-scheme devised by RR supercharger specialist Prof Allen and ‘oscar’ wilde of the compressor section of RR’S experimental department, and approved by Lord Hives of RR for BRM project by FEB 1947. It comprised an array of nine vanes introduced into the supercharger intake, each of which could swivel about its individual perpendicular axis to vary swirl as it entered the impeller. These swivel vanes were to be actuated automatically by a servo piston controlled by boost pressure or engine speed. Bellow 9k rpm these vanes would present edge-on to the intake to create negligible pressure loss, but above 10k rpm they would swivel progressively to swirl the incoming mixture in the same direction of rotation as the adjacent -fast rotating -impeller blades. Ahead of the vanes was a butterfly throttle controlled in the normal manner by the driver.

[gruntguru]

If they only intend to throttle the upstream airflow, a butterfly valve would be much simpler, cheaper and more reliable. Angling the radial vanes not only provides throttling when needed but allows the compressor inducer angle of attack to be optimised for all operating points. There are times when the optimum angle for air approaching the compressor is zero ie no swirl, times when CW rotation will improve compressor efficiency and times when CCW rotation will do the same.

[saviour stivala]

‘’Swirl caused by angling the movable vanes will actually only improve efficiency at only one point on the map. Generally the effects are detrimental to the efficiency and linear flow is desirable.’’

[Tommy Cookers]

Closing the movable vanes when driver lifts throttle will increase turbo rpm for a given turbine exhaust flow because with no airflow the compressor have less work to do, when driver returns on throttle the turbo higher rpm will eliminate turbo lag.

the turbo rpm is constantly controlled by the activity of the MGU-H (because it's a synchronous machine)
we have seen (Honda) bench runs showing that pre-corner the MGU-H pulls down the rpm getting a burst of generation

The turbo rpm is not constantly controlled by the MGU-H. one example is when the driver goes off throttle. When the driver gets back on throttle yes, but the higher the turbo rpm is when driver goes off throttle the faster the MGU-H can spin-up the turbo when the driver returns on throttle.

no
being synchronous the MGU-H machine is coupled to the turbo assembly by internal 'splines' (electromagnetic ones)
the MGU-H won't experience enough torque (motoring or generating or externally driven) to make that coupling fail
ie the H strongly opposes eg extreme turbo acceleration or rpm if eg the compressor load collapsed due to throttling
strongly enough to prevent such extreme acceleration
as I have said, the (Honda) data supports this

if eg turbo rpm isn't pulled down pre-corner this doesn't mean that the turbo rpm isn't constantly controlled by the H
the H can produce any necessary change of its torque in microseconds and of turbo rpm in milliseconds
and as with other rules there is ingenuity here ....
if the H was too small it couldn't always restrain the desires of the turbo .... the 'splines' would 'pole slip' ....
but by 'Goldilocks design' it is just right in size

[saviour stivala]

Yes. When driver goes of throttle the ‘’H’’ is doing no work on or by the turbo shaft. It is just getting a ride on the turbo shaft. And because it is playing no part on the turbo shaft, turbo rpm will be increased when driver goes of throttle. This system will even eliminate the need for a popoff valve.

[Tommy Cookers]

.. When driver goes of throttle the ‘’H’’ is doing no work on or by the turbo shaft. It is just getting a ride on the turbo shaft...

that of course is entirely possible if the H machine has no other instruction
keeping timed excitation pulse train for synchronicity, nulling by voltage/back emf & current /torque by load resistance
as is done in many EVs eg when they stop at traffic lights
(this is analogous to a mechanical transmission having the so-called 'geared neutral' mode)
restoring synchronicity otherwise could be impossible in a race

but it seems better to turn unused turbo rpm into electrical energy - promptly recycled in a turbo rpm-optimal way
afaik that's what most people believe is done

[saviour stivala]

No matter how ‘sesquipedalian’ when the driver lifts (goes off throttle) the ‘H’ is doing no work on or by the turbo shaft. Work by the turbo shaft - when the driver lifts (goes off throttle) the exhaust gas flow to turbine is useless for the ‘H’ to harvest. Work on the turbo shaft – and on the other hand. When ICE is on closed throttle/s it will be a total waste of electrical energy for the ‘H’ to spin the turbo.

[chaoticflounder]

The 5 vanes are inlet guide vanes and help prevent the formation of a vortex that spins in the direction of the compressor direction. This helps improve the pumping efficiency of the compressor. If they want to get really fancy they will cup them just a bit at the end to help hit a 90 deg angle of incidence to the front tips of the compressor. You need to look at a book on turbomachinery for this / axial gas turbines is also good.

The turbo will have a controller driving the current and voltages across the poles of the electric machine. I haven't seen anything indicating if it's an induction machine or a permanent magnet synchronous machine or a switched reluctance machine. For these, it took me a while to wrap my head around ... voltage is proportional to speed, current is proportional to torque ... power is a function of voltage * current

At perfect torque balance where the turbine is driving the compressor, there will be empty voltage waves with no current behind it so no torque is being applied one way or the other. I will be honest I still don't fully understand it but I would suggest looking at Hybrid Electric Vehicles and they give a brief overview of electric machines in there.

Last, the turbine is retrieving heat from the exhaust system ... so in other words the net energy going out exhaust pipe is lower than if it were naturally aspirated. Thinking of complex cycle gas turbines where you have the primary gas turbine and then a secondary heat exchanger in the exhaust that uses water to power a steam turbine. They can get about 45 to 50 % efficiency from the primary but using the combined cycle can get about +60% thermal efficiency.

[johnny comelately]

Further to the above:

[johnny comelately]

"Last, the turbine is retrieving heat from the exhaust system ... so in other words the net energy going out exhaust pipe is lower than if it were naturally aspirated. Thinking of complex cycle gas turbines where you have the primary gas turbine and then a secondary heat exchanger in the exhaust that uses water to power a steam turbine. They can get about 45 to 50 % efficiency from the primary but using the combined cycle can get about +60% thermal efficiency."

Similarly as an aside, with trigeneration units (turbines) when they burn natural gas they produce, heat (to hot water for heating), electricity and CO2 for use in greenhouses (as it is a fertiliser)

[gruntguru]

‘’Swirl caused by angling the movable vanes will actually only improve efficiency at only one point on the map. Generally the effects are detrimental to the efficiency and linear flow is desirable.’’

You got it back to front. Non-rotating inlet flow will give best efficiency at only one point (or line of points) on the map. Movable vanes will give best efficiency at every point on the map and will NEVER be detrimental.
https://www.airbestpractices.com/techno ... efficiency