Renault Power Unit Hardware & Software

[Tommy Cookers]

@ gg
my first impression - isn't this paper founded on the concept that there is no 'free' power recoverable from raised exhaust pressure ?
the opposite of your position, that (turbine power-compressor power) yields 'free' power that's too good to be ignored ???

fwiw - I expected raised exhaust pressure, as raised electrical power is in F1 worth even a corresponding fall in crankshaft power

[mikeerfol]

[Blackout]

Interesting plumbing. Current layouts invariably seek to minimise length of the exhaust plumbing to the turbine (to preserve heat energy). I guess because the early turbines were limited to much lower turbine inlet temperatures.
Also because aircraft applications are less sensitive to transients. Long pipework takes a few seconds to heat up when transitioning from light load to full power with dreadful turbo lag being the result.

The exhaust plumbing is not very long on the Renault, (still longer than the Merc and Honda) but charge air plumbing is ridiculously long
http://www.servimg.com/view/14795526/1811
http://img1.auto-motor-und-sport.de/Red ... 850225.jpg

[gruntguru]

@ gg
my first impression - isn't this paper founded on the concept that there is no 'free' power recoverable from raised exhaust pressure ? the opposite of your position, that (turbine power-compressor power) yields 'free' power that's too good to be ignored ??? fwiw - I expected raised exhaust pressure, as raised electrical power is in F1 worth even a corresponding fall in crankshaft power

Sure - no improvement in Brayton recovery with increased PR (increasing MAP and EBP by the same amount to maintain crankshaft MEP) under the assumptions used:
- 80% compressor and turbine efficiency. (Better efficiencies would however favour increasing PR).
- Intercooling to ambient. Any intercooling is energy lost to the Brayton machine. As I mentioned in the Honda thread yesterday, intercooling could be reduced at higher PR and Brayton work recovery would improve with increasing PR.

Of course the main benefit of higher PR is a leaner overall AFR:
- Mixture in spark region needs to be 1.0 - 1.2
- Leaner mix as flame progresses for best combustion and for knock resistance (lower flame temp)
- "Zero Fuel" zone at chamber extremities to avoid quench and unburned HC
- Increased scavenge air for chamber cooling and complete removal of combustion products.

[Tommy Cookers]

the paper PZ kindly linked is a construct on the position of blowdown dominance making raised exhaust pressure counterproductive
so it appears to disagree fundamentally with both (of what I still perceive as) the PZ/ringo position and the gg position
it says that (with raised exhaust pressure) the power available to the turbine is less than the consequent loss of crankshaft power ?

I imagine some of the disagreement could be attributed to differences in flow choking
but all engines will anyway be choked at serious power eg the current F1 rules force more choking than in the N/A F1
(also Gilles Simon mentioned the conflict between valve sizing and realisation of a high CR)
the gg approach of using very high AFR seems to increase choking and thereby the importance of blowdown ?

btw
the turbocompound aircraft engines didn't seem to be particularly lacking in valve area
the recovery was at takeoff power an 18% supplement to a crankshaft power undegraded by exhaust pressure
yes the CR was no higher than 7.2

[gruntguru]

I imagine some of the disagreement could be attributed to differences in flow choking
but all engines will anyway be choked at serious power eg the current F1 rules force more choking than in the N/A F1
(also Gilles Simon mentioned the conflict between valve sizing and realisation of a high CR)
the gg approach of using very high AFR seems to increase choking and thereby the importance of blowdown?

Choking at the exhaust valve during blowdown is as you say common to all engines at all but the very lowest power settings.

Raising the PR in the manner I have described (intake and exhaust pressures both increase by the same amount) should have little effect on choking. Higher cylinder pressure at EVO is offset by higher pressure in the port. Another way to look at this is density and massflow. At higher PR, the density and massflow increase but volume flow does not. Higher cylinder pressure at EVO means higher massflow through the (choked) exhaust valve.

[Blackout]

Renault turbo seems to have a wastegate that is connected directly to the turbine (and a single entry turbine?)... kinda external and internal at the same time, a bit like this turbo
Is that a common design? I rarely see it elswehere. What are the advantages/drawbacks?

[knabbel]

One of the advantages of this setup is an nicer routing for the wastegate. Bear in mind that the wastegate is not used normally, pressure and turbo rpm is regulated with the ERS-H unit. The wastegate is only used if they have issues with the ERS systems.

[Blackout]

Yeah the rooting is very neat but no, the wastegates play nowadays a bigger role in F1. Just read the previous pages

[hurril]

That sure is a big old turbine!

[bergie88]

It looks like the turbine is at the back with the small tube at the top being connected to the waste gate, with the compressor at the front close to the engine and the ERS-H inbetween or in the V.

[Blackout]

Between the compressor and the engine, there is the compressor's disk-shaped airbox. The MGUH is in the V.

[gruntguru]

That style of wastegate port would allow significant blowdown gas to impinge on the turbine with minimum backpressure during qualy mode. A bit like a Pelton wheel.

[Blackout]

Better pic
(but this time, turbine seems to be surrounded by carbon fiber. Wtf)


It's strange the RB11 has no wastegate there... as if STR and RBR are running different turbines
2014
2015

[wuzak]

but this time, turbine seems to be surrounded by carbon fiber. Wtf

Nice pics.

I think you'll find that the carbon fibre is the forward end of the gearbox where it mounts to the engine. The gearbox will have cutouts in the side, for the exhausts to go through, and the top, to clear the turbo.

To me the top part of the turbine looks to have the same finish as in the lower photo.

In these you can see that the compressor is quite massive too. May be Honda is pushing --- uphill if theirs fits in the vee.