2014-2020 Formula One 1.6l V6 turbo engine formula

[Tommy Cookers]

You have tried to respond to my post without even checking the graph or text I referenced - which clearly show that even at WOT, best economy occurs at significantly leaner than stoic' - contrary to the statements by yourself and Abarth.

maybe you can show us this statement that you say I have made ?

nobody has said that leaning doesn't help efficiency
they have even given some of the reasons for this
they just don't agree with your view that engines must be run significantly lean to burn essentially all the fuel

[Tommy Cookers]

the Wright example is at FAR of about 0.057 (well lean) ie power is reduced by leaning not throttling
the pilot's 'throttle' lever was not connected to the throttle plates like modern F1 etc

Again - the point you might have seen in the Wright data is that best efficiency occurs well lean of stoich - even under high load operation.
And no - the power was not controlled by leaning the mixture. The 10% power drop was a measure used to establish the correct cruise mixture.

pardon me for giving you the Wright FAR that you were saying a few posts earlier that you didn't actually know
now you are an expert who thinks these high load aircraft engine operations are carried out at mixtures well lean of stoich
(and what do you think the other (less lean) mixtures are made available for ?)
and now here you seem to be saying that leaning doesn't reduce power
and simultaneously saying that it does reduce power (10% power drop)

we (ex) pilots were required to lean (in cruise) as being more efficient than reducing to cruise power by throttling without leaning
flights were planned on this basis and technical exams expected this explanation
though we didn't have the power/torque measurement that this Wright engine had to enable precise leaning
cars (until the 3 way catalyst) automatically went lean in cruise because running lean reduced power, so less throttling was needed

[langwadt]

[....]The cost of compressing the higher massflow is more than compensated by expanding the additional massflow in the turbine. [...]

Sounds like a perpetual motion to me...if you want to increase charge air mass flow, the compressor needs more power.
This has to come from exhaust mass flow. How can you have more exhaust mass flow than the amount you have previously charged, with constant fuel flow?

The point is that although additional air mass flow increases the compressor power requirement - the same extra mass flow is available in the exhaust and increases turbine power by more than enough to cover the shortfall.

Think gas turbine (Brayton cycle). Simple Brayton cycle efficiency is a function of pressure ratio - the higher the pressure ratio the greater the efficiency. (Check Wikipedia for a formula.)

for a Brayton cycle you wouldn't want an intercooler

[gruntguru]

1. The graph in the Honda article doesn't show specific consumption mixtures lower than equvalence ratio = 1 (or higher than lambda =1).
So how can you state "significantly leaner" based on that paper?

2. The Honda engine did not have direct injection, not to speak about very high pressure DI. You can't compare quantitatively carburettor or manifold injection engine BSFC graphs with external mixture formation and therefore more or less homogeneous mixture with DI stratified injection.

1. The graph shows bsfc reducing steeply at AFR = 1.0 Are you suggesting the trend suddenly changes there? Do you think the Wright TC in cruise mode operates at 1.1 for any reason other than best efficiency?

2. A homogeneous prepared mixture in a chamber, burns the same regardless of how it was prepared and all the research indicates best efficiency at about 1.1 There is zero possibility a DI engine will sopmehow want a richer mixture for best efficiency. It will want approx 1.1 average in the mixed fuel-air region - then you have fresh air beyond that.

[gruntguru]

You have tried to respond to my post without even checking the graph or text I referenced - which clearly show that even at WOT, best economy occurs at significantly leaner than stoic' - contrary to the statements by yourself and Abarth.

maybe you can show us this statement that you say I have made ?

Here is one.

you seem to think that an engine needs to be 10% lean to fully burn its fuel and then assume that 20% lean must be better than 10% ?
2% lean (AFR 1.02) was/is my view - this is just the sort of thing that 500 bar DI should guarantee any leaner than this just means in one way or another making the engine 'bigger'

BTW, I do not believe that "20% lean must be better than 10%. I believe that:
1. 10% lean will produce optimum combustion in the prepared fuel zone.
2. Teams are running substantial additional air (possible without efficiency penalty if using stratified charge) to produce other benefits including: higher PR in the "turbine engine", reduced combustion temperature, detonation resistance, reduced intercooling etc.

[gruntguru]

the Wright example is at FAR of about 0.057 (well lean) ie power is reduced by leaning not throttling
the pilot's 'throttle' lever was not connected to the throttle plates like modern F1 etc

Again - the point you might have seen in the Wright data is that best efficiency occurs well lean of stoich - even under high load operation.
And no - the power was not controlled by leaning the mixture. The 10% power drop was a measure used to establish the correct cruise mixture.

pardon me for giving you the Wright FAR that you were saying a few posts earlier that you didn't actually know now you are an expert who thinks these high load aircraft engine operations are carried out at mixtures well lean of stoich and what do you think the other (less lean) mixtures are made available for ?) and now here you seem to be saying that leaning doesn't reduce power and simultaneously saying that it does reduce power (10% power drop)

we (ex) pilots were required to lean (in cruise) as being more efficient than reducing to cruise power by throttling without leaning flights were planned on this basis and technical exams expected this explanation though we didn't have the power/torque measurement that this Wright engine had to enable precise leaning cars (until the 3 way catalyst) automatically went lean in cruise because running lean reduced power, so less throttling was needed

I am very familiar with the Wright document and have had a copy on my PC for several years.

The other less-lean settings are for max power. I am not sure where I "seem to be saying that leaning doesn't reduce power". Any of the current F1 engines are capable of a massive increase in power - with no other changes - if it was possible to increase the fuel flow.

[gruntguru]

You have tried to respond to my post without even checking the graph or text I referenced - which clearly show that even at WOT, best economy occurs at significantly leaner than stoic' - contrary to the statements by yourself and Abarth.

maybe you can show us this statement that you say I have made ?

Here is another.

normally, lean running improves efficiency only at partial power ie in road use (because it reduces throttling)

[gruntguru]

Sounds like a perpetual motion to me...if you want to increase charge air mass flow, the compressor needs more power.
This has to come from exhaust mass flow. How can you have more exhaust mass flow than the amount you have previously charged, with constant fuel flow?

The point is that although additional air mass flow increases the compressor power requirement - the same extra mass flow is available in the exhaust and increases turbine power by more than enough to cover the shortfall.

Think gas turbine (Brayton cycle). Simple Brayton cycle efficiency is a function of pressure ratio - the higher the pressure ratio the greater the efficiency. (Check Wikipedia for a formula.)

for a Brayton cycle you wouldn't want an intercooler

Absolutely. That returns to my original suggestion, that reduced intercooling might be a means of producing more power in the current formula.

Anyway my reference to the Brayton cycle is to illustrate that higher boost pressures do not produce a net power drain (due to the increased compressor power) as claimed by some here. If you look at the formula for simple Brayton efficiency, the only variable is Pressure Ratio. So in a simple GT consisting of compressor-combustor-turbine, increasing the "boost" is the only way to increase power output from a given fuel flow.

[piston]

To cool down this discussion I would like to throw in some points:
1. What are upsides and downsides of running lean?
Upsides:
- more mass and therefore less temperature rise while burning the same amount of fuel (=> less prone to knock)
- higher isentropic coefficient => more thermal efficiency
Downsides:
- slower burn rate => lowers the quality of combustion (right word? in German we say "Gütegrad")
- slightly more losses due to friction for the same power output

This leads to the point, that you do want to have a stoichiometric or slightly rich mixture at the spark plug to have a fast burn rate and a (slightly?) lean mixture in the rest of your cylinder for high thermal efficiency and less temperature (=> knock resistance).
Should be a big challange at high engine speeds.

2. Desired A/F ratios:
You can look into almost every good book about combustion: If there is a diagramm for BSFC (or overall efficiency) in relation to A/F ratio it will always be the beast at about lambda = 1.1 (slightly lean) for non-DI engines (so homogeneous mixtures). These diagrams refer to wide open throttle (WOT). For DI engines I know only diagrams for part load, as they try to get homogeneus mixtures at WOT.

3. Flame front velocity
- Depends on A/F ratio (as mentioned in point 1)
- Depends strongly on turbulence in combustion chamber and therefore on engine speed
I have seen a diagramm that shows an increase of almost 100% between 2000 rpm and 14000 rpm (from 23 m/s to 45 m/s). The book says that the transportational velocity is depending on geometry of the combustion chamber and increases with rpm.
I am no expert on this, but for me this would mean there is a smaller influence of A/F ratio on flame front velocity at high engine speeds than on low engine speeds. Which would lead to better efficiency at even leaner mixtures than lambda = 1.1 at high engine speeds.
Do I know it fore sure? No. So please correct me if I'm wrong.

4. Turbocharging / Turbocompounding:
- The Turbine will be slightly more efficient if it is bigger
- You have one turbine / compressor that you build for your engine. The operating range of both (turbine and compressor) is not very big and there are operationg points with best efficiency for this specific turbine.
So as mentioned before: You will have to simulate and test what pressure ratio (and therefore A/F ratio) you will need at which engine speed (and therefore massflow) for the combination of your ICE and the turbocharger that you have picked.

5. knock
- The knock tendency (I hope it's the correct word) can be calculated as the integral of the inverse of the ignition delay time
- It is a function of pressure and temperature (more pressure/temperature = more knock tendency)
I have already calculated knock tendencies and I would not bet that the concept "more pressure (and more A/F ratio) without intercooling" will reduce knock.
With intercooling it's something different, but as mentioned by gruntguru the energy will be lost.

I have picked up these certain points as I think these things are mixed up a bit in this discussion. I do not want to tell anybody here that one or the other concept is rubbish, but that it is extremely difficult to tell what could give an advantage.
But if it was easy, anybody could do it.

[gruntguru]

Nice summary Piston - thanks.

[Brian Coat]

I know this is obvious but ...

"Which AFR?" is interesting but easy to optimise during mapping.

As opposed to say, "how to optimise ICE compression ratio or which compressor/turbine geometry?"

[gruntguru]

I know this is obvious but ...
"Which AFR?" is interesting but easy to optimise during mapping.
As opposed to say, "how to optimise ICE compression ratio or which compressor/turbine geometry?"

It is a lot more than "which AFR". The numbers I have suggested (perhaps 1.4 i.e. 20:1) have never been used in a performance SI engine - these are diesel numbers. To run so lean is a design process - not a mapping decision and every aspect of the engine and ancillaries would reflect that process.

There is no way you could design a turbo compound power unit to operate at say 0.9 then re-map it to 1.4 without redesigning everything in the air path from intake scoop to exhaust outlet.

[Powerslide]

Irony of this discussion is mentioning overworking a turbocharger and its intercooler for less returns. Have we forgotten that a turbocharger is always overworked? Thats what those wastegate are there for, since when did turbochargers take as much exhaust to giving intake? The whole idea of modern day cars giving extraordinary torque for a petrol engine at 1,250-1,500 rp/m is to over work those turbochargers! Go look at BMW and how small turbos they use on their six's designed around nothing less to over work a turbocharge and its intercoolers.

Have we diminished into thinking overworking a turbocharger is a bad thing when it gets its energy for waste???

[Wayne DR]

I know this is obvious but ...
"Which AFR?" is interesting but easy to optimise during mapping.
As opposed to say, "how to optimise ICE compression ratio or which compressor/turbine geometry?"

It is a lot more than "which AFR". The numbers I have suggested (perhaps 1.4 i.e. 20:1) have never been used in a performance SI engine - these are diesel numbers. To run so lean is a design process - not a mapping decision and every aspect of the engine and ancillaries would reflect that process.

There is no way you could design a turbo compound power unit to operate at say 0.9 then re-map it to 1.4 without redesigning everything in the air path from intake scoop to exhaust outlet.

I agree, I think the operating window will be a lot narrower than we all think. In the end, I believe, it comes down to efficiency and engine life.

The "rules" limit fuel flow to 100kg/h, and the laws of chemistry/physics limit energy released from that fuel to between 43-46 MJ/kg (potentially a 6-7% variance, but essentially fixed per fuel supplier). The only significant variable is efficiency.

Due to increased internal friction, engines will be less efficient at higher RPMs, not to mention increased wear and component stresses. I am struggling to see a benefit that is gained from running lean at higher RPMs (over 11-12k RPM).

Could the engine manufacturers be running their engines "super lean"? Possibly, but I believe they are more likely to be controlling boost pressure, to maintain AFR between acceptable narrow operating ranges.

My guess is that they will be running about 0.84 for their "rich" map (max power - not used often, but available) and 1.08-1.1 for "lean" map (about 30% less power than "rich" - again not used often, but available). Their normal operating range will be in the order of 0.9 and 1.02 (99% of max power down to say 88% of max power at 1.02).

[gruntguru]

My guess is that they will be running about 0.84 for their "rich" map (max power - not used often, but available) and 1.08-1.1 for "lean" map (about 30% less power than "rich" - again not used often, but available). Their normal operating range will be in the order of 0.9 and 1.02 (99% of max power down to say 88% of max power at 1.02).

0.84? never! Max fuel flow is fixed at 100 kg hr. Max power occurs at max efficiency - probably about 1.1 in the combustion region plus some spare air around that.

At 0.84 a maximum of only 84% of the fuel can be burned so the maximum heat available from the fuel is 0.84 x 44 MJ/kg x 100 kg/hr x 1/3600 hr/sec = 1.02 MW or 1020 kW. (compared to 1220 kW if you burn all the fuel) At 40% efficiency thats 408 kW at the crankshaft.