2014-2020 Formula One 1.6l V6 turbo engine formula

[Tommy Cookers]

there's about 15% at takeoff and about 8% in cruise (anybody else like to come in on this ?)

always full rich for takeoff in any plane (in this plane you would probably die without it) - that's what full rich is for !
auto-rich wouldn't do it

the load on the engine is in principle well suited to 'centrifugal' supercharging (which delivers roughly with the square of rpm)
the load is comes from the (aerodynamic) pitch of the prop
this is maintained automatically at whatever setting the pilot has chosen regardless of the power the pilot uses
like an adjustable CVT
so in fine pitch selected for takeoff the load allows the engine 2900 rpm
cruise is in coarse pitch, this pitch increases the load, so pulling the engine down the power curve handily reducing the power
going to lean mixture (probably auto-lean) further reduces the power and allows the (automatic) throttle to be well open
and the rpm here is 1600-2000, the sfc better than any other SI engine
so the proper aero engine is always a race-type design, supercharged like a Novi or V16 BRM, top-endy and free-breathing
radials in particular have very little bearing friction

many eg the USAAF had manual selection of supercharger (blower) gearing
and high blower was used quite often at low altitude to give life-saving power
similarly single speed blowers were geared for medium altitude, so should never have full throttle at low altitude, but often did
such are flown using the throttle eg to maintain 36" Hg, if you use full throttle you might get 44" and 60% more power
so unofficially they could be flown by feel, if there's detonation you will know to throttle back (your teeth may fall out)
(eg a T-6 Harvard requires 36" and 550 hp, based 80/87 fuel, but will do 44" and 800 hp on 100/130 but watch the head temps)
most other countries (and the US Navy) used auto boost control though, often with a calculated and limited manual over-ride
a former colleague did a zero boost takeoff in a Mk XIV Spitfire (about 1000 hp of 2000+)

some N/A aero engines eg racers had excessive CR for efficiency at high altitude and WOT was not allowed at low altitude
takeoff at WOT was ok only if the engine was not hot
they were flown by reference to a manifold pressure gauge eg throttling to -3lb boost limit
BMW started this in WW1
it never caught on

[WhiteBlue]

there's about 15% at takeoff and about 8% in cruise (anybody else like to come in on this ?)

If this is meant to be recovery your figures cannot come from the data sheet. Where do you get them from?

I think I have read the diagram correctly for the gross recovery. Your figures could be for net values after the compressor is taken off. But then they look too high.

Regarding rich mixture at the start I have to take your word as I'm not familiar with aero engines and it sounds you actually are.

[Tommy Cookers]

set dividers to the width (height really) of the recovery band - where it says TAKEOFF
move dividers across to the scale and read off the scale the power corresponding to the divider setting
eg 510-520 hp for the top of the chart (3400 hp)
510hp is about 15% of 3400hp

or the crankshaft power of 2890 hp has about 17.5% (510 hp) added from recovery, giving a combined power of 3400 hp

yes, if that % was read across to F1 it would need the compressor power deducted

[WhiteBlue]

The first relation does not make sense to me. 17.5% is the correct figure IMO. It is the percentage of power added to the basic engine by recovery.

At max Cruising Power in low blower ratio I get 12.4%
At cruising power with high blower ratio I get 8.3%

We agree about the need to take away the compressor to make it comparable with the F1 configuration. I'll do that only for the take off point:

Increasing compressor ratio from 6 to 8 % is 100 hp.
So initial 6% compressor ratio could be worth 300 hp.

So net recovery at max power would be 200 from 2900 hp = 7%

That would mean 46 hp for F1. A bit unrealistic?

Good that there is higher CR now.

[wuzak]

I think with aero engines of the WW2 era the terms Rich and Lean are relative terms.

Lean would still be rich in an absolute sense, just nowhere as rich as rich mixture is.

Re the direct injection in the R-3350 - that was incorporated not because of efficiency gains, but because of continuing issues Wright were having in getting even mixture distribution to all cylinders.

[wuzak]

there's about 15% at takeoff and about 8% in cruise (anybody else like to come in on this ?)

always full rich for takeoff in any plane (in this plane you would probably die without it) - that's what full rich is for !
auto-rich wouldn't do it

the load on the engine is in principle well suited to 'centrifugal' supercharging (which delivers roughly with the square of rpm)
the load is comes from the (aerodynamic) pitch of the prop
this is maintained automatically at whatever setting the pilot has chosen regardless of the power the pilot uses
like an adjustable CVT
so in fine pitch selected for takeoff the load allows the engine 2900 rpm
cruise is in coarse pitch, this pitch increases the load, so pulling the engine down the power curve handily reducing the power
going to lean mixture (probably auto-lean) further reduces the power and allows the (automatic) throttle to be well open
and the rpm here is 1600-2000, the sfc better than any other SI engine
so the proper aero engine is always a race-type design, supercharged like a Novi or V16 BRM, top-endy and free-breathing
radials in particular have very little bearing friction

many eg the USAAF had manual selection of supercharger (blower) gearing
and high blower was used quite often at low altitude to give life-saving power
similarly single speed blowers were geared for medium altitude, so should never have full throttle at low altitude, but often did
such are flown using the throttle eg to maintain 36" Hg, if you use full throttle you might get 44" and 60% more power
so unofficially they could be flown by feel, if there's detonation you will know to throttle back (your teeth may fall out)
(eg a T-6 Harvard requires 36" and 550 hp, based 80/87 fuel, but will do 44" and 800 hp on 100/130 but watch the head temps)
most other countries (and the US Navy) used auto boost control though, often with a calculated and limited manual over-ride
a former colleague did a zero boost takeoff in a Mk XIV Spitfire (about 1000 hp of 2000+)

some N/A aero engines eg racers had excessive CR for efficiency at high altitude and WOT was not allowed at low altitude
takeoff at WOT was ok only if the engine was not hot
they were flown by reference to a manifold pressure gauge eg throttling to -3lb boost limit
BMW started this in WW1
it never caught on

Usually Low Gear and High Gear were chosen by altitude.

In British parlance, the maximum power in each gear was achieved at Full Throttle Height. That is the altitude at which the throttle plate can be fully open. Below that the throttle is partially closed.

Below full throttle height the boost remains more or less constant. Above FTH boost falls off. So as the aircraft climbs the power rises until FTH (because with the throttle closed the engine is less efficient), after which it falls off. In theory the supercharger gear would change at the height where power in low gear and high gear are the same.

For a multi-speed engine (2 or more distinct gears) that gives a distinctive saw tooth power against altitude graph.

In some instances aircraft would take-off in high gear, before switching to low gear for climbing. An instance of this is the Avro Shackleton, whose Griffons would be set to FS (Full supercharger = high gear) for take-off at +25psi boost using anti detonation injection (water/methanol injection).

Lower boost levels have higher FTH. So for an airliner cruise may be in low gear, rather than high gear, because that is the optimum altitude. Low gear consumes less power than high gear, so that is an advantage.

Early Merlins were flat out with +6psi or +9psi boost. By 1943 they could cruise at +7pss boost.

[WhiteBlue]

Wuzak, the main reason I looked into the Wright again - I did that three years ago already - is the question how much net recovery was possible with the combination of fixed two gear supercharger and the compounded turbine recovery in comparison to a compounded design of today. The answer seems to be very little in take off mode and nothing even in cruise at high altitude, because the compressor will take more power than the recovery turbine generated.

But that view is an artificial view of today. At the time the compressor was a must to keep up power at altitude and the recovery turbine was a great way to get take off power with low engine weight. Boosting and recovery were not done for the purposes they will be done in F1. Nevertheless it is good to have done the numbers because now I can say that any proposal to use supercharging and blow down turbine recovery with mechanical linkage would not make much sense in F1.

To give you a reasonable level of power in F1 you need net recovery of at least twice the 7%. It would ideally be above 20% In order to saturate the MGU-K. To achieve that the turbo in F1 needs high turbine and compressor efficiencies above 80% and it cannot afford to loose any significant amount of power by a waste gate. That is something we knew already.

[Lightknight]

Looking at the 100kg/hr fuel rate is worrisome though, it works out to a 8900rpm limit, 2 bar boost, with 588 indicated horsepower, at stoichometry.

That's weak!! 438kW at 8900rpm is as anemic as it can get.

The torque is still staggering however. I think this was the number the engine working group was watching keenly.

I got 347lb.ft of torque vs 297 for the current engines.

Actually the figure to date is 600 NM compared to 320 NM for the V8 as it should be. That is more realistic. By the time Honda is in town the Hp will be, including the ERS 825 to 850 bhp.

[Tommy Cookers]

the NACA report 822 tells us what we need to know (as shown particularly in Fig 7 and Table III)
it's based on the R-2800 with 40deg valve overlap
because it has some sea level data it is much more useful than NACA 1602

the best bsfc at sea level is with a delta P of -20" Hg
and the best bsfc is consistent with best combined power

at 10000' power recovered is 263 hp and net ('crankshaft') power is 1043 hp with 85% turbine and 94% transmission efficiencies
this recovery figure is after the deduction of supercharging power
this is at -8" Hg delta P

a bit of mental extrapolation shows clearly that there would be more recovery at sea level
because of the best bsfc - delta P even with more overlap would be close to the above -20" Hg, say -15" Hg or -0.5 bar
and this gives more turbine power, as exhaust pressure is greater relative to ambient (than eg at 10,000')

I would say that efficient recovery of 30% of crankshaft power is available
(this is the crankshaft power at -0.5 bar)
because this 'backpressure running' gives the greatest efficiency
ie the greatest power in a fuel-limited race

that's how they got the 120 kW they had in mind all along



btw @wuzak
the concept regarding full throttle height is only applied when there is automatic throttling (as with most eg all RAF)
or when obeying the rules
if the pilot believes throttling is auto when its not he will overboost by accident (read Boyington/P40)
or deliberately overboost as was often done with manual throttling, flying by ear (to avoid detonation)
done successfully by entire RAF squadrons in early Mustangs on tactical recon and reported to authority
done by Jim Mollison unsuccessfully with N/A engines in the McRobertson race, against advice from his wife in the back seat
detonation can result from clumsy use of prop pitch control even in modern N/A light aircraft - I should know

[WhiteBlue]

TC , as often you have completely lost me with this post. To many imperial units or expressions that are unknown with very little explanation. The only thing I understand is your opinion that 30% crankshaft power should be recoverable if a certain level of back pressure occurs.

[dren]

So roughly 30% of crank power will be available via added back pressure at the best bsfc. So the MGUK will likely be saturated at max fuel flow. But this isn't really recovery through the MGUH, it's just more efficient power transfer, right? I think I noticed that it was roughly a 1:1 ratio of crank to pressure engergy transfer. So if the ICE is making xxx hp, then by increasing the PR we are really only helping the bsfc but not total power output? Or is there still some recovery figure, like the low 7% or so I was reading?

So I guess I'm asking: What's the loss at the crank vs the gain at the MGUH with a PR increase? If we're getting the full 120kW into the MGUH, what are we losing at the crank?

[ringo]

Looking at the 100kg/hr fuel rate is worrisome though, it works out to a 8900rpm limit, 2 bar boost, with 588 indicated horsepower, at stoichometry.

That's weak!! 438kW at 8900rpm is as anemic as it can get.

The torque is still staggering however. I think this was the number the engine working group was watching keenly.

I got 347lb.ft of torque vs 297 for the current engines.

Actually the figure to date is 600 NM compared to 320 NM for the V8 as it should be. That is more realistic. By the time Honda is in town the Hp will be, including the ERS 825 to 850 bhp.

There were revisions, i've made an error there, my current bet is 580bhp.
Interesting stuff on the TC engine.
The discussion of waste gates reminds me of the discussion of whether intercoolers will be used. haha
I guess time will tell if they are used.

[Tommy Cookers]

So roughly 30% of crank power will be available via added back pressure at the best bsfc. So the MGUK will likely be saturated at max fuel flow. But this isn't really recovery through the MGUH, it's just more efficient power transfer, right? I think I noticed that it was roughly a 1:1 ratio of crank to pressure engergy transfer. So if the ICE is making xxx hp, then by increasing the PR we are really only helping the bsfc but not total power output? Or is there still some recovery figure, like the low 7% or so I was reading?

So I guess I'm asking: What's the loss at the crank vs the gain at the MGUH with a PR increase? If we're getting the full 120kW into the MGUH, what are we losing at the crank?

http://naca.central.cranfield.ac.uk/rep ... rt-822.pdf

the combined power is always best around best bsfc
best bsfc is with -20" Hg on the engine used (probably -15" Hg on an engine with more liberal valve timing)
ie the loss at the crank is the same or less than the gain via the MGUH as the delta P becomes more negative
so 120 kW recovered power might cost 100 kW crankshaft power without any fuel rate limit

but the bsfc as reported is 14% better at 10000' than the same engine with turbo
extrapolation suggests 10% better at sea level
so under a fuel rate limit there's 10% more combined power with this level of compounding

but the F1 engine 'boost' will be much higher, so the best bsfc delta P might be more, maybe close to -1 bar ?
so the bsfc gain over an equivalent turbo engine should be maybe 15%
(because recovered power is largely due to the pressure difference between exhaust pressure and ambient)
giving 15% more combined power with this 'best bsfc' level of recovery
of course a suitably big MGUH and related electrical system is needed

a lower level of recovery such as Wright actually used would according to this report give only maybe 7% bsfc gain
(at lower recovery levels the bsfc gain comes from recovery that costs very little crankshaft power)
and so only 7% more combined power under a fuel rate limit
but would use a much smaller capacity MGUH and related electrical system

with a turbine-electric recovery system as in new F1 .......
in a low recovery level system the electrical power can reasonably described as free
as the efficiency improves in proportion to the electrical power
at maximal recovery level as in NACA 822 only about half the electrical power can be regarded as free
because the efficiency gain is 'only' about half the recovery level
so we should resist the inevitable media and PR attempts to tell us that eg a 120 kW MGUH recovers that much 'free'

NACA 822 is based on running at pressure (loosely, 'boost') of 40" Hg Abs (about 1.35 bar Abs)
the supercharger power is rather low, around 3 % of output power
F1 'boost' will be about 2 bar Abs and the supercharging will need at least 6% of output power ?
somewhat reducing recovery
IMO

[pgfpro]

Lots of great info TC!!!

So TC what do you think the new 2014 F1 engines will be at as far as recovery power???

[Tommy Cookers]

FWIW I would now say 100kW (about 135 hp) typically ie much of the race time from the MGUH

we know the MGUH output will be driving the MGUK for much of the racetime, this saves on storage, efficiency and cooling
but I never knew how much recovery was possible with an SI engine, and how this improves efficiency (not power)
this 'backpressure operation' reduces the large loss of pressure and kinetic energies as the exhaust blows down from 8 bar
these losses are disproportionate as the great pressure and density difference causes supersonic flow and pressure drop

F1 CR will be much higher, but also mep/density will be higher so the blowdown losses are still high (unless we have backpressure)
as I see it, higher CR (although indisputably helping efficiency) means that the cylinder pressure is higher even at EV opening
unless the EV is opened later (though this seems possible)
with backpressure the blowdown may be from 9 bar Abs , but it's driving against a denser gas load now at maybe 2.7 bar Abs
which must be less lossy than eg N/A or 'no backpressure' blowdown from 8 bar Abs against maybe 1.05 bar Abs

FWIW it seems to me likely that the backpressure will be increased as rpm goes significantly above 10500
as it is the least bad option IMO for in-cylinder thermodynamics
and we now know that backpressure improves efficiency
yes there is an apparent obligation for electric power ie MGU-K motor action to be proportionate to ICE action
but that can be managed even with backpressure and recovery increasing at the high rpm end