2014-2020 Formula One 1.6l V6 turbo engine formula

[pgfpro]

@ ringo
all our 'turbo' experience has been without backpressure
assuming we haven't needed to lower the CR, this gives a relatively small amount of free power (for supercharging or compounding)
this was the basis of the world's only significant turbocompounding programme, giving on average less than 10% free power
and it would give a similar result in 2014 F1 ?

higher exhaust pressure (ie a substantial backpressure) loses crankshaft power but allows corresponding increase in recovered power
because the usual (necessary evil) large pressure/KE losses around the exhaust valve are reduced by backpressure
NACA tests showed a much larger gain in bsfc from this (15-20% better than the engine in turbocharged form)

so for 2014, backpressure is no longer a bad thing ?
and promises more combined power
if/when there is a correspondingly larger recovery system

IMO the new F1 2014 turbo engines will off set the back pressure issues the 1945 Wright engine had.

1) Increased compression ratio. IMO it will be around 13:1 This higher compression number will be because of DI.
High compression helps with the "isentropic expansion" starting earlier with a higher pressure then ending with a lower pressure number as the piston gets closer to BDC. This is the same reason high compression engines are more efficient. More energy is used to push the piston down the bore and less energy dumped out the exhaust.
Today's example would be when all out small CI race engines are running a ton of boost and they then choose to go to Methanol over petrol so they can run a higher compression ratio, they record lower back pressure from the increased compression ratio number.

2) Higher "engine delta p" F1 engineers will run leaner A/F ratios with the help of DI again (high boost levels) and a larger turbine then normal to offset MGUH load and all the while keep more wiggle room to keep a great engine delta p numbers.
Example: This is a good friends 2.0L that makes around 1000 HP running a turbo compound system. It uses the small turbo to make boost at lower rpm, and then when max flow from the small turbo is reach large waste gates open and start bypassing the small turbo turbine and feeding the large turbo, while maintaining the small turbo's turbine's perfect PR.


Yellow line is the trans break
Red line rpm
Blue back pressure in psi
Green intake pressure in psi

[Tommy Cookers]

I was anyway thinking about CR in all this
if the EV opening was the same wouldn't the pressure at EV opening be more or less the same for any CR ?
and pressure energy and kinetic energy of the exhaust are equivalent
I felt that the aircraft people might have found a CR that was possibly a bit low worked well with backpressure

btw IIRC the 88 Honda F1 was raced about 8% rich all year, because of hesitation when trying to run 2% rich
although 2% gave good (or comparable ?) dyno results

[pgfpro]

I was anyway thinking about CR in all this
if the EV opening was the same wouldn't the pressure at EV opening be more or less the same for any CR ?
and pressure energy and kinetic energy of the exhaust are equivalent
I felt that the aircraft people might have found a CR that was possibly a bit low worked well with backpressure

btw IIRC the 88 Honda F1 was raced about 8% rich all year, because of hesitation when trying to run 2% rich
although 2% gave good (or comparable ?) dyno results

It would have more pressure at the EV with a lower compression and less pressure at the EV with a higher compression engine.
TC, here's a great simulator.
http://www.fing.edu.uy/if/mirror/TEST/t ... toria.html

move the slide on the compression ratio to change compression ratios then hit calculate.Take a look at p3 verses p4

[WhiteBlue]

This may be a start.

Thanks Wuzak for this excellent source which I did not know. Particularly the difference between a blow down turbine and a turbo are excellently explained which creates another understanding of the blow down mechanism. This will go into my permanent storage.

[Tommy Cookers]

the turbo as we know it in zillions of road cars (SI engined anyway) is of course operated as what Wright calls blowdown
that is running on pressure/KE 'pulses' without raising mean exhaust pressure above ambient
(Wright showed the reader how well their engine worked in this way at sea level ambient pressure)

the turbos whose running was categorized by Wright as a pressure turbine worked much harder (than for road cars)
but anyway had no bulky and complex exhaust piping and so did not retain orderly exhaust pulses
an exhaust design without useable pulses can only work with mean exhaust pressure raised above ambient
so was called a pressure turbine
we do not know the exhaust pressure relative to the induction pressure/'boost'
I assume it was lower, ie +delta P

NACA report 822 is largely concerned with exhaust pressure higher than 'boost', ie -delta P
NACA report 1602 agrees that exhaust pressure greater or equal to induction pressure is needed for best efficiency
(but reminds us that exhaust pressure about 20% less than induction pressure give best power)
this is a summary of tests on the Allison 1710 and P&W 2800 engines, as well as the Wright 3350 cu in

interestingly, the Allison was tested with afterburning
ie using a rich mixture, air was injected into the (cooled) exhaust ahead of the turbine
both power and efficiency were greatly improved (this combustion being free of blowdown losses across the exhaust port ?)
this is not allowed in F1

Paul Lamars note shows us that at 1840 hp the Wright engine wastes 2655 hp in sensible exhaust energy
(our diesels have less waste to exhaust than SI engines do, but even more waste to coolant)
1735 hp of this is accessible only to temperature-responsive recovery systems like wuzaks Organic Rankine ('steam') devices
these might be more efficient than the BMW turbosteamer
only the KE/pressure energy (395 hp after losses) is accessible to temperature-unresponsive recovery systems like turbines
a bit more if we operate at - delta P ? (Wright recovered 160 hp from theirs)

so MGU-H is a misnomer unless it is driven by eg the Organic Rankine device
this would best use both coolant heat energy and exhaust heat energy (together these total about double the ICE power output)
if allowed in F1, the OR recovery device could yield maybe 150 hp ?

btw the Wright DI injected very early, making no attempt to reduce fuel exposure to the compression process
btw in aircraft lean running is to reduce or eliminate throttling, so is not useful to F1 ?

[WhiteBlue]

I noticed the low CR of the Writhe engine. That should really make a difference. But they had more efficient compressors and turbines than we see in commercial road cars. If we come back to injection and combustion you have to assume that injection pressure was very poor and the fuel would be delivered in a similar fashion as the Mercedes DI did in the fifties. In effect it was no different to port injection today. They injected before the intake stroke and delivered a rich mixture.

TC, you seem to think that they could be going for partial compression before injection. What do you think that is going to do to AFR at different rpm? Stoichiometric all the way with earlier and earlier injection as the rpm raises? Or perhaps even under stoichiometric in a lazy rev band from 4.000-8.000?

In take off configuration the Wright turbines were adding 21% more power to the engines. 21% of 650 hp would be 137 hp. In best power mode with stoichiometric combustion - which they were not designed to do - the Wright Engine with turbo compound got a BSFC of .465 lb/bhp.h which is 283 g/kW.h or 79 g/MJ. If the F1 engines are designed for 650 hp from the ICE only they would get 206.3 g/kW.h or 57.2 g/MJ without the compounded energy. So there is a huge difference in the fuel efficiency of the basic engine involved. Among other reasons I see the injection and combustion process as crucial for that kind of fuel efficiency.

[wuzak]

Don't forget that the Wright R-3350 development started in 1937/38.

Its bore was 6.125" (155.6mm), so it is little wonder that the compression ratio was low.

Also consider that the R-3350 was air cooled and ths was somewhat limited in cooling capacity, which can't help knock resistance. And there was no intercooler after the compressor.

Materials and combustion chamber design have improved considerably since. The smaller cylinder allows better compression ratios, as does the higher speed nature of the modern engine.

And, without looking it up, I would hazard a guess that in the last 20-30 years CR have gone up, with or without DI.

[WhiteBlue]

The interesting question is the compounded proportion of the power. If F1 can also get a 21% ratio or better they would not be far from saturating the MGU-K. 21% would be 102 kW compared to 120 kW the MGU-K can handle. It is encouraging that it has been done before. It is all very speculative at the moment.

[Tommy Cookers]

I think they were by compounding adding up to 18% to the power ?
I don't think you can get even this without robbing the piston-to-crankshaft power somewhat (based on the NACA work)
because you need an unfavourable or zero delta P compared the favourable delta P of the same engine turbocharged but uncompounded
I think Wright retained crankshaft power on the T-C with help from the 12 tuned length exhausts (necessary for T-C anyway)
no other production aero engine (supercharged anyway) ever had tuned length exhausts

CR choice was presumably dominated by the desire to use around 68" Hg absolute for best takeoff power
always with 115/145 PN fuel
aircraft engines always chose CR this way
the prop has the effect of a CVT, full power has the effect of lowering the gearing and high mep
cruising has high gearing allowing near-WOT, low rpm and relatively high mep
often just kept the original CR and raised the boost when fuel improved
the Merlin was about 7:1, but the N/A Merlin (the Meteor) used 8:1 with 80 Octane fuel

now the Wrights are run on 100/130 and use 58" or so
some late ones used 7.2:1 CR (military with heavy ADI I assume)

the Wrights got only a few % from compounding most of the time
and rather a lot at max boost, max rpm, max mixture strength ie takeoff
no doubt they chose to go this way

note they never ran stoichiometrically, always rich or lean, because stoi is hottest and overheats the turbine and exhaust valves
the DI seems to have been used in part to give exhaust valve cooling (late EV closing was general for this reason)
the exhaust plume is often almost white hot, presumably there is burning (at rich mixture) on the outside of the plume
partly why I think that they had a relatively high exhaust pressure at takeoff (also at the usual airline altitude ?)
and the confidence-inspiring chart showing an absence of high exhaust pressure was only true for sea level etc
originally this was a USN project for patrol work (endurance at low altitude)
there then was a big demand for general military transport with Korea, the airlines followed almost by accident IMO

regarding 2014 CR, I don't understand the fuel rules on Octane no

[WhiteBlue]

..the Wrights got only a few % from compounding most of the time
and rather a lot at max boost, max rpm, max mixture strength ie takeoff..

That is where the power to weight ratio really matters. They got this short term power for very little weight increase. They would have had to add an extra engine for most 4 engine air frames to have the same effect at much higher weight.

Btw. max boost was also influenced by the two step blower ratio which was always in low at take off.



They still had 14.4% compounding during maximum power except take off (METO) amazingly although the absolute power level was 22% lower in METO mode than in take off mode. In cruise at low blower ratio they still got 12.4% compounding and the power level was only 56% of take off power. I understand that take off was in stoichiometric mixture. In METO and in Cruise they had to run a leaner mixture in order to get reasonable valve and turbine life. But the most amazing thing to me is the rpm level of these engines. 2900 at TO, 2600 at METO and 2400 at Cruise. Compare to F1 engines they were running very slow in a small rev band.

note they never ran stoichiometrically, always rich or lean, because stoi is hottest and overheats the turbine and exhaust valves.

That is not what I understand from the figures and the text. The take of was at best power and stoichiometric and then they had to go leaner until compounded BMEP was shown 10% lower in METO and Cruise. METO and Cruise were also different by engine rpm. METO would have been used for altitude climb and Cruise for high and low altitude cruising speed.

The engine also had two different supercharger ratios. Low blower ratio was generally used for take off, low level patrol, climb, descend and landing. High blower ration was only used when high altitudes were reached because this setting could lead to detonation of the motor if the ratio was engaged at too low altitude.

At low altitude the turbine power was smaller because the blow down was towards a higher atmospheric pressure. That gave an increase of turbine power at high altitude cruise. Nevertheless the power of the naked engine was higher at low altitude cruise because blower ratio was lower and that took away 100 hp less from the engine for the supercharger. Difficult to understand initially.

[lio007]

http://www.cranfield.ac.uk/sas/pdf/engi ... ngpost.pdf

This one says about 7% energy recovered in a 4 cylinder engine.

7% of 450kW (603hp) ~ 31.5kW (42hp).

It says:

It is important to note that the gear ratio of the mechanical linkage was optimised to get the highest value possible for the power at 8,500 rpm. Furthermore, the ratio was the same for all speeds. A higher output can be obtained if the gear ratio is variable and is optimised at each speed.

The MGUH gives that variable speed control.

Also

The study also revealed that an axial turbine induces less backpressure than a radial turbine and is therefore better suited for this application.

from the revealed renault and mercedes pictures...does both have a axial turbine?

[Tommy Cookers]

@WB
your recovery figures are miles out
the engine has about twice the stroke of typical road car engines, so 2900 rpm is quite high enough for 2000+ hour life
it would spend most of the time below 2000 rpm in high pitch (like overdrive), lean mixture, more or less unthrottled
not particularly reliable or trusted

[strad]

..the Wrights got only a few % from compounding most of the time
and rather a lot at max boost, max rpm, max mixture strength ie takeoff..

That is where the power to weight ratio really matters. They got this short term power for very little weight increase. They would have had to add an extra engine for most 4 engine air frames to have the same effect at much higher weight.

http://img710.imageshack.us/img710/7851/3a25.png

They still had 14.4% compounding during maximum power except take off (METO) amazingly although the absolute power level was 22% lower in METO mode than in take off mode. In cruise they still got 12.4% compounding and the power level was only 56% of take off power. In METO and in Cruise they had to run a rich mixture in order to get reasonable valve and turbine life. But the most amazing thing to me is the rpm level of these engines. 2900 at TO, 2600 at METO and 2400 at Cruise. Compare to F1 engines they were running very slow in a small rev band.

Ya call that a broad flat torque curve????

[strad]

Sounds peaky to me
http://www.youtube.com/watch?v=ebpkJXJ7 ... r_embedded
[youtube]http://www.youtube.com/watch?v=ebpkJXJ7 ... r_embedded[/youtube]

[WhiteBlue]

@WB
your recovery figures are miles out...

I don't think so. The diagram shown is pretty exhaustive about those figures as is the data table. Can you tell me which figures you think I got wrong?
But I agree that my conclusion was wrong. I did not consider that the blow down turbine had no compressor to drive. So compressor power has to be taken out first to arrive at a percentage that can be applied for the F1 engine comparison.

If we make an estimate how much the compressor took out of the engine at full take off power I would think we are talking almost 400 hp. That leaves just a meagre 200 hp for net recover if you transfer the thing to a turbo. 200 hp by 3200 hp would be 6.3% net recovery.

Here goes all the glory!

But it has been an interesting exercise all together. I finally understood more about those air craft engines than I ever did before.