Mercedes Power Unit Hardware & Software

[dren]

BTY, in the thread where Andy's comments were posted, the author clarified that NOx is a concern for them to transfer the technology to road cars.

That makes more sense since there is little reason to care about NOx emissions in a purely F1 context.

Ok, yes that does make sense. I was a bit thrown off by the initial statement as NOx in an F1 car shouldn't matter at all.

[ENGINE TUNER]

And following on from Tommy, they have to tune the engine to support electricity generation by running hotter exh. temperatures, This may not be happening all the time the engine is running, but it does happen sufficiently to be a concern if the technology were translated to road cars.

What proof do we have that they tune for hotter exhaust temps to spin the MGUH better? When I use compressed air to spin my turbines to test their balance it doesn't care how hot the compressed air is, only the pressure(and flow)(which I can easily regulate). The delta T from turbine inlet to exhaust is minimal in my experience. Lowering the exhaust temps would be a much smarter path IMO.

Max boost would be far more beneficial for MGUH electrical generation than higher exhaust temps.

[ENGINE TUNER]

.... NOx emissions increase as you lean from 1.0 (stoich) and peak at about 1.2 (20% excess air) then drop as you lean out from there. ......

not necessarily ?
NOx generation (once there is adequate spare oxygen) is fundamentally driven by temperature ie duration at/above a flame temperature of 2800 deg F
the typical engine has (by heat dilution) lower cycle temperatures when lean so spends little or no time at this critical temperature
but the Merc F1 is not typical, for efficiency its temperatures are kept unusually high by the high boost and intentionally minimal charge cooling
and certainly we can find references that say that NOx falls above 45% lean

What evidence do we have for "intentionally minimal charge cooling"? Other than standard F1 procedure of minimizing drag by minimizing cooling .

[hurril]

And following on from Tommy, they have to tune the engine to support electricity generation by running hotter exh. temperatures, This may not be happening all the time the engine is running, but it does happen sufficiently to be a concern if the technology were translated to road cars.

What proof do we have that they tune for hotter exhaust temps to spin the MGUH better? When I use compressed air to spin my turbines to test their balance it doesn't care how hot the compressed air is, only the pressure(and flow)(which I can easily regulate). The delta T from turbine inlet to exhaust is minimal in my experience. Lowering the exhaust temps would be a much smarter path IMO.

Max boost would be far more beneficial for MGUH electrical generation than higher exhaust temps.

Gas expands with heat (and conversely: contracts with reduced temperature.)

[NL_Fer]

In road car technology hcci and spinoff's like tji, are using excess air to keep the combustion cool, increase efficiency and lower NOx. What if in F1 the excess air is used as a coolant, to cool the engine from within the cilinders and out through the exhaust? Would it be the intension to put as much heat in the excess air also for maximum expansion and put that energy in turbine/mgu-h for recovery?

[FPV GTHO]

How is the extra air supposed to keep it cooler?

[PlatinumZealot]

And following on from Tommy, they have to tune the engine to support electricity generation by running hotter exh. temperatures, This may not be happening all the time the engine is running, but it does happen sufficiently to be a concern if the technology were translated to road cars.

What proof do we have that they tune for hotter exhaust temps to spin the MGUH better? When I use compressed air to spin my turbines to test their balance it doesn't care how hot the compressed air is, only the pressure(and flow)(which I can easily regulate). The delta T from turbine inlet to exhaust is minimal in my experience. Lowering the exhaust temps would be a much smarter path IMO.

Max boost would be far more beneficial for MGUH electrical generation than higher exhaust temps.

You must question why the wrap the exhaust pipes in insulation? Answer that first.

[Tommy Cookers]

.... NOx emissions increase as you lean from 1.0 (stoich) and peak at about 1.2 (20% excess air) then drop as you lean out from there. ......

not necessarily ?
NOx generation (once there is adequate spare oxygen) is fundamentally driven by temperature ie duration at/above a flame temperature of 2800 deg F
the typical engine has (by heat dilution) lower cycle temperatures when lean so spends little or no time at this critical temperature
but the Merc F1 is not typical, for efficiency its temperatures are kept unusually high by the high boost and intentionally minimal charge cooling
and certainly we can find references that say that NOx falls above 45% lean

What evidence do we have for "intentionally minimal charge cooling"? Other than standard F1 procedure of minimizing drag by minimizing cooling .

no evidence afaik ..... but the charge temperature will be allowed to remain higher than in eg earlier F1 engines at similar boost levels
because higher charge temperature helps combustion of lean mixtures and so allows leaner mixture
and the leaner the mixture (that can be quickly, fully, and consistently combusted) the more efficient and powerful the engine will be

although a high charge temperature and very high CR gives a higher than usual temperature after compression, injection strategy prevents detonation
with the leaner mixture the cycle peak temperature (on combustion) will be lower - the '100 kg/hr' heat being 'diluted' across a greater mass of air
this lower peak temperature means that there's less heat loss to coolant - so more work done on the piston by the greater mass at pressure
similarly the exhaust has a greater mass at pressure - so more work is done on the turbine and there's less (heat) energy loss

lagging the exhaust manifold is always useful of course

[Just_a_fan]

You must question why the wrap the exhaust pipes in insulation? Answer that first.

One reason would be to protect everything else under the bodywork from the heat of the exhaust. Oh, and the bodywork itself too.

[godlameroso]

Only Mercedes had that problem during 2013 testing.

Anyone that's built a few turbo motors knows about the importance of heat wrapping the turbine and the exhaust manifold.

The greater the difference in the temperature between turbine inlet and outlet, the greater the force acting on the turbine.

The back pressure created in the engine by the placement of the turbine is the primary driver of the turbine, as the heat from combustion rapidly increases the pressure in the engine, it is this pressure created from the heat of combustion that creates the pressure differential between the inlet and outlet of the turbine. It is this energy that is harvested by the MGU-H, thus to increase turbine operation requires both increased combustion temperatures, and pressures.

Like it's been stated, faster combustion, means lower heat loss to the surroundings, you can also lower heat loss by improving valve port geometry to promote faster combustion.


Almost a 1/3rd of the heat energy in an engine is lost to cooling, a lower cooling requirement would mean less energy lost to convective radiation.

Faster combustion also reduces the amount of time the flame front is in contact with any convective surface. Similarly to how your hand will not get burned if it's waved past a candle flame quickly in contrast to doing the same motion more slowly.

[noname]

You must question why the wrap the exhaust pipes in insulation? Answer that first.

One reason would be to protect everything else under the bodywork from the heat of the exhaust. Oh, and the bodywork itself too.

Coatings can be helpful here. There is bunch of stuff covered by them under the skin. This way you can wrap bodywork tighter, yet people are still wrapping insulations around manifolds.

BTW, Ferrari started 2014 with un-insulated exhausts in pursuit of aero gains. It took them just few races to change their mind.

[PlatinumZealot]

Only Mercedes had that problem during 2013 testing.

Anyone that's built a few turbo motors knows about the importance of heat wrapping the turbine and the exhaust manifold.

The greater the difference in the temperature between turbine inlet and outlet, the greater the force acting on the turbine.

The back pressure created in the engine by the placement of the turbine is the primary driver of the turbine, as the heat from combustion rapidly increases the pressure in the engine, it is this pressure created from the heat of combustion that creates the pressure differential between the inlet and outlet of the turbine. It is this energy that is harvested by the MGU-H, thus to increase turbine operation requires both increased combustion temperatures, and pressures.

Like it's been stated, faster combustion, means lower heat loss to the surroundings, you can also lower heat loss by improving valve port geometry to promote faster combustion.
https://www.youtube.com/watch?v=cWHq-Qr ... e=youtu.be

Almost a 1/3rd of the heat energy in an engine is lost to cooling, a lower cooling requirement would mean less energy lost to convective radiation.

Faster combustion also reduces the amount of time the flame front is in contact with any convective surface. Similarly to how your hand will not get burned if it's waved past a candle flame quickly in contrast to doing the same motion more slowly.

THIS!!
Thank you.
Alot of people dont realise that these turbines have a very large heat dependency.
Firms like mitsubishi and General electric spends millions in development each year improving the hot stage before the turbine to improve efficiency.

[Frank_]

the turbine can only harvest a percentage of the heat tho surely ? ie more heat on the intake = more heat on the exit

[godlameroso]

Then you create a better flowing turbine to manage that temperature difference. There's enough energy in the exhaust to run the MGU-H -> MGU-K at half power(60kW) and charge the batteries at the same time, it's believed Mercedes can do 80kW + battery charging.

And this actually makes a lot of sense. We all sing praises of Mercedes chassis, but there's something most people overlook. Relying less on the MGU-K to harness electricity has a big influence on chassis performance, particularly under braking.

I think a big part of their advantage is their chassis is designed around using less MGU-K and more MGU-H to harvest electricity.

*Merry Christmas everyone.

[Tommy Cookers]

......The back pressure created in the engine by the placement of the turbine is the primary driver of the turbine, as the heat from combustion rapidly increases the pressure in the engine, it is this pressure created from the heat of combustion that creates the pressure differential between the inlet and outlet of the turbine. It is this energy that is harvested by the MGU-H, thus to increase turbine operation requires both increased combustion temperatures, and pressures....
........... Like it's been stated, faster combustion, means lower heat loss to the surroundings, you can also lower heat loss by improving valve port geometry to promote faster combustion. ........

'faster' combustion could mean greater heat loss to the surroundings .....
unless expansion is also 'faster' - which it likely won't be in an engine whose fuel rate is flat over 10500 rpm
the relative speed of the two things being (in SI engines anyway) evidenced by the ignition timing