Max power, at 10500RPM or higher than 10500RPM?

[gruntguru]

Read my post above.
The engines are running MAP of approximately 4 Bar at 10,500. If VE stays constant they would only need to reduce MAP to 2.8 Bar at 15,000 to maintain the same AFR. Clearly they can reduce boost even further and run a lot richer than this if needed.

[saviour stivala]

I did read your post; your statement is correct and totally as expected an answer.

Which prompts technical logic to ask. How is drastically reducing one of the two components that makes up the strongest possible combustion, namely the air boost from 4 BAR to 2.8 BAR, and so the air volume going to help produce as strong a combustion as that attained at maximum power speed of 10500rpm when the engine air is boosted at 4 BAR with the resultant bigger volume of air.

In short, how will all that reduction in air boost/volume going to help increase power output over and above the maximum power speed?

[Tommy Cookers]

.....In short, how will all that reduction in air boost/volume going to help increase power output over and above the maximum power speed?

if the above actually means ..... how will PU power be supported despite the reduction in air mass per cycle ? .....

as compressor power taken reduces greatly with boost reduction H-recovered power is rather unaffected ...or ...
increased MGU-H generator load increases 'back pressure' and H-recovered power but this costs crankshaft power ..or
selective VLI operation could vary the boost/engine rpm relationship in use

piston expander efficiency depends on difference between maximum and minimum temperatures of in-cylinder gasses
maintained charge cooling (with reduced boost) helps via increased H recovery or ...
piston expander efficiency is maintained as with reduced charge cooling in-cylinder temperature differences are maintained
higher charge temperature is allowed as temperature rise from in-cylinder compression (of reduced mass/cycle) is less

and in principle reduced cylinder cooling is possible - remember brief 10500 rpm operation is flattered by being undercooled
and/or any underscavenge ie from increased back pressure strongly maintains in-cylinder temperature

and of course frictional torque reduces with boost reduction and rpm increase

the whole issue is of course substantially relieved when F1 operates (invisibly to us) from 10200 rpm or 10100 rpm etc

[gruntguru]

I did read your post; your statement is correct and totally as expected an answer.

Which prompts technical logic to ask. How is drastically reducing one of the two components that makes up the strongest possible combustion, namely the air boost from 4 BAR to 2.8 BAR, and so the air volume going to help produce as strong a combustion as that attained at maximum power speed of 10500rpm when the engine air is boosted at 4 BAR with the resultant bigger volume of air.

In short, how will all that reduction in air boost/volume going to help increase power output over and above the maximum power speed?

(At WOT.) The best utilisation of the limited fuel at every engine speed, is established in testing. At each engine speed from 10,500 to 15,000 there will be a unique AFR that produces the best output. It is more likely that the result is close to constant AFR rather than constant MAP. This is for reasons of combustion chemistry and flame speed in particular.

This has been the case with both NA and turbo engines throughout history. A given engine will make best power with a particular AFR - even when the engine is throttled to MAP < 1 or when a supercharged engine is re-tuned for a different boost level.

Your last sentence

In short, how will all that reduction in air boost/volume going to help increase power output over and above the maximum power speed

is incorrect on one important point. If MAP is reduced with rpm to maintain AFR, there is no reduction in air volume (there is actually an increase). Neither is there a reduction in air massflow - this remains constant if AFR and fuel flow remain constant. Power is the result of fuel mass and air mass flows. At higher speed, each "bang" is smaller - but there are more of them.

Rephrasing to your words, at higher speed you do not produce "as strong a combustion". You do not need to, to achieve the same power - because there are more combustions happening.

[saviour stivala]

Reducing the boost from 4 BAR at maximum power speed of 10500rpm down to 2.8 Bar past the maximum power speed in order to maintain stoichiometric (14.7:1) air fuel ratio to produce the strongest combustion possible using regular pump fuel will also reduce the air volume. The air volume have to be reduced to compensate for the extra number of combustions per minute with RPM increase because the extra number of combustions have to share the same maximum volume of fuel flow. Those extra number of combustions will be much weaker to such an extent that that no additional power can be produced over and above the maximum power speed of 10500rpm. In short this here power unit is fuel limited. It max its power at 10500rpm. If the rule makers didn’t added the (@ 10500 RPM) to the (MAXIMUM FUEL FLOW OF 100KG/H) on their second attempt when formulating the rules. These engines would have been designed to peak their power output at a much lower maximum RPM.

[Tommy Cookers]

.....If the rule makers didn’t added the (@ 10500 RPM) to the (MAXIMUM FUEL FLOW OF 100KG/H) on their second attempt when formulating the rules. These engines would have been designed to peak their power output at a much lower maximum RPM.

much lower rpm/much higher torque ....
would require a much higher boost (particularly important for lean running)
frictional power losses wouldn't fall - frictional torque would increase due to the higher MEP
detonation would be a bigger problem - CR would need to be lower
the gearbox internals etc would have more inertia - so being less suited to established shifting and clutching techniques

[gruntguru]

Reducing the boost from 4 BAR at maximum power speed of 10500rpm down to 2.8 Bar past the maximum power speed in order to maintain stoichiometric (14.7:1) air fuel ratio to produce the strongest combustion possible using regular pump fuel will also reduce the air volume.

Do you mean the "air volume per cycle"? The "air volume" ie total flow into the engine will increase as rpm increases - it does not reduce. In fact - every engine ever raced has airflow increasing - all the way to the redline.

In short this here power unit is fuel limited. It max its power at 10500rpm. If the rule makers didn’t added the (@ 10500 RPM) to the (MAXIMUM FUEL FLOW OF 100KG/H) on their second attempt when formulating the rules. These engines would have been designed to peak their power output at a much lower maximum RPM. The air volume have to be reduced to compensate for the extra number of combustions per minute with RPM increase because the extra number of combustions have to share the same maximum volume of fuel flow. Those extra number of combustions will be much weaker to such an extent that that no additional power can be produced over and above the maximum power speed of 10500rpm.

OK, what if the fuel flow regulations were changed slightly.
From 0 - 10,500 the rule is the same as at present ie 100 kg/hr @10,500. Above 10,500, the fuel flow increases linearly from 100 kg/hr @10,500, peaking at 102 kg/hr @15,000.
Where is the peak power engine speed now?

[saviour stivala]

“Air volume” – total air flow into the engine. Will increase as RPM increases. Yes of course it does, up to the respective maximum power speed. But maximum power speed is not the engine ‘red-line’. The engine ‘red-line’ is the maximum RPM either imposed by the rules or as decided by the engine maker as the maximum RPM the respective engine can withstand for at least a race distance. The maximum power speed point is always below the maximum RPM irrespective if it’s an NA or a forced induction fuel restricted engine.
As to (WHAT IF), “IF” the fuel flow is allowed to increase linearly from 100kg/h @ 10500rpm, peaking at 102kg/h @ 15000rpm, the peak power (maximum power speed) will be moved to the maximum RPM the maximum fuel flow will peak at. Ask any of the two teams, one of which had his results disqualified when caught-out for breaching the fuel flow rules using two different makes of engines and recently was screaming that another particular team was breaching the maximum fuel flow to gain a power advantage.
But really, as to the term (IF - THIS OR IF THAT), In my native language they say IF – he fell he would most probably broken his leg.

[hollus]

IF a designer decided to, on purpose, slightly reduce the power his engine is making at 10500RPM compared with what it could do?
@stivala, you may say we should not be discussing in hypotheticals, but most people in this thread, certainly including me, are proposing that that is exactly what is happening and the only optimal strategy. Also, this is a forum, discussing hypotheticals is one of the main activities here.

Wouldn't purposely making less power than absolutely possible at 10500rpm change the effective max power point?

[saviour stivala]

“Wouldn’t purposely making less power than absolutely possible at 10500rpm (The point at which maximum fuel flow permitted is reached) change the effective maximum power point (speed)?. What it does change is the ‘purposely’ chosen power to be made and how less than optimum possible obtainable.
I see nothing wrong in anyone describing a ‘hypothetical case to clarify one’s point, although it will be just hypothetical/conjectural even if not well supported by available evidence. This because I honestly cannot imagine anybody choosing to make less power than that possible if not to curtail reliability.

[hollus]

It should be clear by now, but the proposal is to make less power than possible at 10500 to make more power than otherwise at 11000 or so (which would still (probably) be less than the absolute max attainable at 10500).
I think that IF the engineering target is to make as much power as possible at 11000, a logical consequence will be slightly less power than possible at 10500 and less peak power than otherwise attainable.

Why the engineering target would focus on 11000 is a separate question.

[gruntguru]

“Air volume” – total air flow into the engine. Will increase as RPM increases. Yes of course it does, up to the respective maximum power speed. But maximum power speed is not the engine ‘red-line’. The engine ‘red-line’ is the maximum RPM either imposed by the rules or as decided by the engine maker as the maximum RPM the respective engine can withstand for at least a race distance. The maximum power speed point is always below the maximum RPM irrespective if it’s an NA or a forced induction fuel restricted engine.
As to (WHAT IF), “IF” the fuel flow is allowed to increase linearly from 100kg/h @ 10500rpm, peaking at 102kg/h @ 15000rpm, the peak power (maximum power speed) will be moved to the maximum RPM the maximum fuel flow will peak at. Ask any of the two teams, one of which had his results disqualified when caught-out for breaching the fuel flow rules using two different makes of engines and recently was screaming that another particular team was breaching the maximum fuel flow to gain a power advantage.
But really, as to the term (IF - THIS OR IF THAT), In my native language they say IF – he fell he would most probably broken his leg.

The purpose of the hypothetical was to test your ability to think through the issues. If you believe 102 kg/hr @15,000 makes more power than 100 kg/hr @ 10,500, why are you so sure that 100 kg/hr @ 10,500 must make more power than 100 kg/hr @ 15,000? Your response to the hypothetical shows you believe the difference is less than 2%. (This is unlikely to to be the case.)

With equal fuel flow from 10,500 to 15,000 there is equal potential for the power peak to fall anywhere in that range. It is not just the size of the "bang" (the size of the bang determines torque.) It is the size of the bang times the number of bangs per minute that determines power. With every engine, the designer has to choose where the power peak should occur. It is always possible to move it up or down a little by changing camshaft profile, intake and exhaust diameters, intake and exhaust runner length etc. Regardless of the chosen speed for peak power, the power at adjacent speeds will be slightly lower than it could be.

In the case of the current F1 rules sure - if the goal is the absolute highest peak power number, the designer would optimise for 10,500 because friction is lower and there is slightly more potential for a higher number. Unfortunately that would be a compromise because power drops sharply below 10,500 and accelerating through the gears the engine must be operated mostly above 10,500. Optimising for 10,500 will slightly reduce power at all speeds above 10,500 and the average power accelerating through the gears will be mostly at less than optimal power. Optimising the engine at the middle of the main operating range (say 10,500 - 12,000) will result in higher average power when accelerating through the gears, than optimising for 10,500.

[saviour stivala]

The consequences of the engine being fuel flow restricted/limited at a maximum flow of 100kg/h @10500rpm by the rules (5.1.4 = fuel mass flow must not exceed 100kg/h @ 10500rpm. And 5.1.5 = below 10500rpm the fuel mass flow must not exceed Q (KG/H) = 0.009N ((RPM) +5.5.) meaning that from 10500rpm onwards up to the maximum RPM permitted of 15000 the fuel flow flows at 100kg/h which means no additional power can be added to that reached at maximum power speed of 10500rpm. While below 10500rpm the flow is permitted to flow at (9500rpm = approx 92kg/h) and (at 10000rpm = approx 96kg/h) which means power output is below that reached at maximum power speed.

[turbof1]

In the case of the current F1 rules sure - if the goal is the absolute highest peak power number, the designer would optimise for 10,500 because friction is lower and there is slightly more potential for a higher number. Unfortunately that would be a compromise because power drops sharply below 10,500 and accelerating through the gears the engine must be operated mostly above 10,500. Optimising for 10,500 will slightly reduce power at all speeds above 10,500 and the average power accelerating through the gears will be mostly at less than optimal power. Optimising the engine at the middle of the main operating range (say 10,500 - 12,000) will result in higher average power when accelerating through the gears, than optimising for 10,500.

This, this, this.

What good is a high peak power if you can only maintain for a fraction of a moment, while if you choose a power curve that has less peak power but can maintain a higher average power across the band.

This discussion has been made so many times and it's going in circles. So for the benefit of the topic, the above will be hold as a fact of which there is no discussion possible about. That is forceful, but if that's the only way to get some evolution in this topic, so be it.

[gruntguru]

. . . to that reached at maximum power speed of 10500rpm. . .

Maximum fuel flow is available from 10,500 to 15,000. Why do you insist on using the phrase

maximum power speed of 10,500

?????