2014-2020 Formula One 1.6l V6 turbo engine formula

[gruntguru]

Another hypothesis for everyone to chew on.
"Mercedes are running their engine leaner than Renault and Ferrari."

1. MB clearly have a power advantage and therefore a thermal efficiency advantage.

2. A lot of people are suggesting that Mercedes are using a larger turbine. I don't know what the evidence for this is but if true, a larger turbine suggests a higher mass flow, higher boost and leaner mixture.

3. It is apparent that Mercedes are able to charge the ES more rapidly and run at maximum output for longer before needing to recharge. To do this they must be harvesting more energy from their turbine (MGUK). This suggests a higher pressure ratio and mass flow through their turbine.

Another way to look at this is to consider the PU as a gas turbine engine with a recip' engine as the combustion chamber. Gas turbines increase in efficiency as the PR is increased. (This is analogous to increasing the CR and ER in a recipe engine). The limit on PR is the temperature exiting the combustion chamber and entering the turbine. The turbo compound engine extends this limit by performing a lot of the compression and expansion in a recip' cylinder where the peak pressure and temperature is very brief (just after TDC) and intermittent (combustion chamber components are cooled by the fresh charge for a large percentage of the cycle). Evidence from the Napier Nomad and the Garrett helicopter proposal indicates that best efficiency coincides with very high PR in the turbo machinery (of the order of 10:1) and moderate compression ratios in the recip' machinery. In the Garrett paper (http://ntrs.nasa.gov/archive/nasa/casi. ... 001160.pdf) PR is 10.3 on the intake side and 9.3 on the exhaust side. Turbine output is 32% of ICE crankshaft power (24% of total power) which is equivalent to about 150kW

The situation in the F1 PU is quite different. Excess power generated in the turbine can only be consumed at the rate of 120kW (MGUK limit) the rest must go to storage. To maximise the continuous power available to the wheels, it would be better to reduce the turbine power in favour of higher crankshaft power from the recip' (by reducing PR) - even though this would result in lower efficiency and therefore lower total power. Other considerations limiting PR include small electrical losses in converting turbine power to electricity in the MGUK and back to work in the MGUH and probably also lean combustion limits in the SI recip'.

I think it is reasonable to guess that MB has similar crankshaft power but higher turbine power compared to the other teams. The obstacles MB may have overcome to achieve this include:
- Extending stable combustion to leaner mixtures. Possible methods include - higher intake temp for stable combustion of homogeneous mixtures (see Honda researchhttp://www.greencarcongress.com/2014/04 ... -hlsi.html), extending stratified charge to higher (10,500+) rpm.
- Operating at a higher PR without significant reduction in CR. Detonation control by lean mixture and/or stratified charge.
- Reduced inter-cooling would improve combustion stability as stated above but will also increase turbine power.

[Tommy Cookers]

you are quoting 60s NASA material on the efficiency benefits of higher PR in the turbo parts of a compounded engine
this I have repeatedly said,( 40s NACA descriptions of raising mean exhaust pressure retaining PU power and boosting efficiency)
essentially the same thing, an effect that is in principle unrelated to mixture strength

NACAs work suggested the load of higher exhaust pressure/density reduces the supersonic element of blowdown
so less blowdown pressure is (wastefully) converted to heat and dispersed through time, equivalent to some mean pressure term

and we now seem to agree that the designer of a turbine or CI or SI compounded engine cannot use an ideal PR or equivalent
but engages with leaner mixture's help to raising useable PR or CR/mep

so we are left to consider the predictable benefits of leaning to efficiency 'in cylinder' - due to improved specific heats ratio
(interestingly if these benefits were proportionate to the fuelling reduction, diesel cars would be undriveable)
against the disbenefits - eg here due to the power costs (net after recovery) and 'package costs' of pumping the extra air
80s European road car engines (not needing 3 way catalysis) ran around 20-22% lean to near-WOT/high rpm

vehicle gas turbine (and CI engine) designers have made their choices
leaning clearly will reach a limit where the performance costs outweigh the performance benefits (or they'd fuel in molecules)
and we know SI has some leaning-limiting factors related to combustion speed and consistency
and that F1 demands conventional spark ignition (1 plug ?) - no plasma, no lasers etc - they don't want 'freak' engine developments
and that running above 10500 rpm surely demands scope for an element of leaning for motives of practicality
given that they must be slightly or somewhat lean to combust fully the fuel
and that lean runnung to reduce power is more efficient than throttling (cylinder cutting is allowed, are they doing it ?)
my guess is that all are running most of the time in the range 2-20% lean

a big turbine doesn't necessarily mean lean running, anyway.....
how much better is the Merc PU ? (a Renault PU-ed car beats all the Merc powered or Merc PU-ed teams except one)
the Merc chassis etc has been as good as any eg last year

p.s.
we (with thanks to the OP of the link) had seen the Honda/greencarcongress paper before , the full SAE paper would tell us more
eg more about the friction loss regime (crank rpm, piston speed etc) related to this 30 AFR unthrottled running relative to F1's

[Brian Coat]

NOTE: The Honda abstract is quoting an engine running at 5 Bar NMEP (equiv. BMEP <4 Bar?) and 1500 rpm ...

[trinidefender]

NOTE: The Honda abstract is quoting an engine running at 5 Bar NMEP (equiv. BMEP <4 Bar?) and 1500 rpm ...

The Honda abstract? Who? What? When? Where? How? Why?

Source?

[J.A.W.]

you are quoting 60s NASA material on the efficiency benefits of higher PR in the turbo parts of a compounded engine

Actually the cited/linked NASA/Garrett paper is from ~20 years ago, not ~50..

[gruntguru]

The Honda abstract? Who? What? When? Where? How? Why? Source?

http://www.greencarcongress.com/2014/04 ... -hlsi.html

[gruntguru]

you are quoting 60s NASA material on the efficiency benefits of higher PR in the turbo parts of a compounded engine this I have repeatedly said,( 40s NACA descriptions of raising mean exhaust pressure retaining PU power and boosting efficiency) essentially the same thing, an effect that is in principle unrelated to mixture strength

True - however the principle of efficiency increasing with PR and CR when applied to the Brayton cycle or the Otto cycle or the Diesel cycle is independent of mixture strength. The case in hand - where the displacement of the recip' machine is fixed and the rate of heat addition is fixed will unquestionably see an efficiency improvement as the PR of the turbo cycle is increased. Yes the returns will diminish more rapidly due to real-world isentropic efficiencies in the compressor and turbine, and due to fixed friction in the 1.6 litre recip' and rising heat losses compared to the fixed heat input rate as PR is increased.

However, the turbo machinery on the F1 PU does not exist simply to produce sufficient airflow for the 1.6 L recip' to burn the available fuel. It is an integral part of a compound heat engine which has two stages of compression and two stages of expansion. The PR chosen for each stage will have an effect on the efficiency of energy recovery from the entire system.

so we are left to consider the predictable benefits of leaning to efficiency 'in cylinder' - due to improved specific heats ratio

The effect of improved specific heat value as mixture is leaned is very much secondary. The primary benefits of leaning are reduced dissociation (effectively more complete combustion) and reduced heat loss to the cylinder wall due to lower combustion temperature. The second of these can be reduced even further with stratified charge by concentrating heat toward the centre of the chamber - away from the walls.

vehicle gas turbine (and CI engine) designers have made their choices leaning clearly will reach a limit where the performance costs outweigh the performance benefits

Those choices are clearly based on optimising power from a given package - not power from a given fuel rate.

(or they'd fuel in molecules) and we know SI has some leaning-limiting factors related to combustion speed and consistency and that F1 demands conventional spark ignition (1 plug ?) - no plasma, no lasers etc - they don't want 'freak' engine developments and that running above 10500 rpm surely demands scope for an element of leaning for motives of practicality given that they must be slightly or somewhat lean to combust fully the fuel and that lean runnung to reduce power is more efficient than throttling (cylinder cutting is allowed, are they doing it ?) my guess is that all are running most of the time in the range 2-20% lean

My guess is 20% to 50% lean at full load, not just part load.

BTW, throttling is not required for manifold pressures at or above atmospheric, the MGUK can slow the compressor as required. Modulating manifold pressure between 3.5 and 1.0 bar abs would allow load modulation in the range of approximately 40% - 100% without throttling. Additional leaning (with stratification) to say lambda 1.8 would permit further load reduction to perhaps 60% of NA BMEP, perhaps as low as 9 bar or 25% of full load BMEP.

a big turbine doesn't necessarily mean lean running, anyway.....

A bigger turbine means bigger volume flow. I think you have missed the thrust of my post. Although I led with "Mercedes are running their engine leaner than Renault and Ferrari." the benefit lies only partly in the lean mixture itself. Higher turbine mass flow and PR provide an efficiency (power) advantage but higher mass flow dictates the recip' must be capable of efficiently burning a leaner mixture.

how much better is the Merc PU ? (a Renault PU-ed car beats all the Merc powered or Merc PU-ed teams except one) the Merc chassis etc has been as good as any eg last year

There is general agreement that the MB customer engines have lower power (circa 30hp) due to fuel and lubricant advantages enjoyed by the MB team and their development relationship with Petronas.

[Brian Coat]

Of course the fuel is a big factor because the power/efficiency is driven by OPR (among other things), which will be constrained by knock.

[Blanchimont]

A bigger turbine means bigger volume flow.

The size of a turbine alone doesn't tell the whole picture as long as we don't know the corresponding rotational speed. The mass or volume flow should be proportional to the cross section of the turbine and the speed, the same as in power = torque * rot. speed.

Or am i wrong on this?

[gruntguru]

As a rule of thumb, for single stage radial turbines, volume flow is proportional to flow area and pressure ratio is proportional to tip speed (rot' speed x tip diameter).

Because we are comparing different turbines used in the same application (F1 teams), a "bigger" turbine would suggest greater volume flow, higher PR or both.

[bhall II]

[lost at sea]

[FW17]

Does an air to air inter cooler have a larger drag coefficient than an equivalent water radiator?

[ringo]

I am not discrediting the wtc. But the thread seems to have on blinkers against more similar technology with similar performance similar fuels and similar operating environment.
I am sure there is much to learn from any modern turbo charged performance engine with direct injection. You only have to try and look into it.

More random words strung together without even answering a question posed to you. Do you still propose that the current generation F1 engines run at lambda .98?

If you do can you, or anybody here, possibly give a reason why the engine manufacturers would possibly want to run the engines knowingly in a condition that that doesn't burn all the fuel and hence release all the fuels energy?

A lot of evidence as to why the engines probably run on the lean side. Do you or anybody else have any evidence that they run on the rich side? Saying road cars run it doesn't count as it doesn't actually explain anything as to why it is done.

As i said to you i did not propose that they run at .98 lambda. I did not propose anything of the sort. I simply used that in my calculations so i could make some corelation to the Honda RA engine. So stop holding me to that number, it is not suggesting anything. It simply allows me to make able to compare both engines to see if my cacluations are correct.

There is no evidence existing from the engine makers that says the engines run lean or rich, and under what situations this may change. Idealy stoichemetry is what you would want, especially if you want to take advantage of the direct injection technology.
And this is why I am telling you guys to stop focusing on the turbo compounding and pay more attention to a modern turbo engine with direct injection. Maybe you will find your answer about A:F from those engines.

[trinidefender]

I am not discrediting the wtc. But the thread seems to have on blinkers against more similar technology with similar performance similar fuels and similar operating environment.
I am sure there is much to learn from any modern turbo charged performance engine with direct injection. You only have to try and look into it.

More random words strung together without even answering a question posed to you. Do you still propose that the current generation F1 engines run at lambda .98?

If you do can you, or anybody here, possibly give a reason why the engine manufacturers would possibly want to run the engines knowingly in a condition that that doesn't burn all the fuel and hence release all the fuels energy?

A lot of evidence as to why the engines probably run on the lean side. Do you or anybody else have any evidence that they run on the rich side? Saying road cars run it doesn't count as it doesn't actually explain anything as to why it is done.

As i said to you i did not propose that they run at .98 lambda. I did not propose anything of the sort. I simply used that in my calculations so i could make some corelation to the Honda RA engine. So stop holding me to that number, it is not suggesting anything. It simply allows me to make able to compare both engines to see if my cacluations are correct.

There is no evidence existing from the engine makers that says the engines run lean or rich, and under what situations this may change. Idealy stoichemetry is what you would want, especially if you want to take advantage of the direct injection technology.
And this is why I am telling you guys to stop focusing on the turbo compounding and pay more attention to a modern turbo engine with direct injection. Maybe you will find your answer about A:F from those engines.

You actually did propose it in a form or fashion. We were all discussing the probable power output and boost pressure values that these engines run. You consistently denied it when other people had a a figure higher than yours and then referred them to calculations you made. The problem is you made the calculations based off a number, cannot recall right now, lower than lambda .98. How can you deny somebody else's claim and say it is wrong then show them calculations based off of a figure you just admitted would be at least slightly to low?

That sounds like claiming that they run a rich mixture to me.

Another question. Modern road car engines run under different conditions than F1 engines do they not? Those modern road car engines only produce power through the crankshaft and whether you want to admit it or not having a compounded engine does change up how things are worked out.

They are what I would consider medium stressed as they are designed for years of running, low duty cycle engines (not designed to be run at full power for long amounts of time). F1 engines are the exact opposite of that, highly stressed and high duty cycle.

Let's look at this scenario. A road car engine runs at full load. It will run slightly rich. Why would they do this? They know that they already have as much air as possible in the cylinders (hence airflow restricted) and know that by pumping in extra fuel that it ensures all the air will be consumed making the maximum power. In our F1 engine series we have a situation where we are limited by fuel. Therefore designers will want to at least ensure all the fuel is burnt releasing the maximum amount of energy. For this to happen there has to be at least a stoichiometric ratio. Many designers say that you add 2% to the airflow stoichiometric figure to ensure complete fuel combustion. Therefore wouldn't it be fair to say that these engines run at least lambda 1.02?

[gruntguru]

1. Go back to the Bosch Handbook. Best efficiency at between 1.2 and 1.5. And that is with port injection!
2. Road cars cannot meet NOx emission standards at leaner than stoic. For that reason alone, they do not even run lean at cruise conditions where fuel economy could be significantly improved by running 1.2 or higher.
3. Road cars are not fuel flow limited as trini says. They are air flow limited.