2014-2020 Formula One 1.6l V6 turbo engine formula

[ringo]

I don't think there will be any lean running under normal race situations.
It's a waste of air and energy to run the compressor. Lean running directly affects flame temperatures and pressures.

[gruntguru]

Have you ever seen how much excess air goes through a turbo diesel engine? Do you know how efficient these engines are? Do you think they could be made more efficient if they "wasted" less energy running the compressor?

Yes - lean running affects flame temperatures and pressures, but did you know that current F1 engines have Direct Injection and "stratified charge" which means the engine can be run lean, while the flame burns in a region that is rich?

[Sasha]

First thing that came to me when I saw the exhaust for the Mercedes...axial flow turbine(compact turbine with big compressor).

My team took a look at Honeywells petrol Axial turbocharger for our project.

With the MGU-H,they can work around the problems with axial turbine and it would have a big compressor(better with multi air-entry).

[Powerslide]

. . . . probably it comes down to setting where Mercedes-Benz will run optimum air fuel ratio when needed for that flier then run lean on parts of the circuit where power is less important. . . . .

If running lean improves efficiency (power produced/fuel flow rate) they will run lean for maximum power. If power becomes less important, they may choose to reduce the "fuel flow rate" but they will still run the engine at whatever is the most efficient AFR.

There is a difference between "lean" and "less fuel".

I'm just thinking they run that turbo at full boost as much as possible just turning down fuel, leaning out for power reduction via driver throttle input lift. Inf act they might even go as far as cylinder deactivation on minimal input. I would not know if they run lean for maximum power but we can safely assume all Formula One engine manufacturers have the capacity to tune air fuel ratio for optimization in an engine test room that would deem shocking for them to have miss something. If mercedes-Benz are running lean for full power, what are the chances the other manufacturers engineers to missing this??

[gruntguru]

You are right in saying thy have full control of boost (airflow) and fuel flow at every engine speed and throttle setting. The boost and fuel flow will be chosen to achieve the highest efficiency at every operating point. It is not as simple as saying they keep the boost high and reduce fuel when they want to reduce power.

Yes, all the engine manufacturers will have determined what AFR and boost works best for them. How high they can go with boost will depend a lot on how accurately their injection system can position the atomised fuel cloud in the combustion chamber, how accurately they can control the tumble, swirl and turbulence in the chamber and so on. Small gains in these areas can easily produce a significant advantage.

[Brian Coat]

"4. Each of the three conditions above calls for leaner AFR and consequently an increase in the required boost pressure. Higher boost means increased detonation tendency and higher cycle temperatures. An easy way to reduce both is to increase excess air. This excess air would not be added to the air-fuel zone but to the region surrounding it. This is standard practice on diesels (to control cycle temps)."

What you are describing is increasing the overall CR and increasing inlet temp, whilst using peripheral air around a stratified charge to prevent detonation. Hmmm ...

This works on a Diesel because the stratification is guaranteed by the fact that the fuel is only introduced at the point of combustion.

I imagine the level of stratification obtainable from spray-guided DI at 10,0000 rpm WOT is not going to stop the engine detonating when you increase the overall CR and inlet charge temp ...

[gruntguru]

Agreed. It is undoubtedly a fine balancing act and it will be interesting when the details of what they have achieved can be revealed.

It pays to remember what Honda achieved in 1988. 26 years ago:
- 2.5 bar MAP
- 9.4:1 CR
- 70*C charge temperature
- Lambda ratio 0.98 at full power and 12,000 rpm
- 32.2% thermal efficiency (Mercedes claims over 40% in 2014)
and remember this was an "airflow limited" engine with race fuel consumption restrictions. Todays engines are "fuel flow limited" which creates a direct relationship between power and efficiency which did not exist in 1988. Remember also the Honda engine did not have DI. If the DI system is unable to produce significant charge stratification at 10,500 rpm what is the benefit of having it?

[Brian Coat]

But I must admit, if it was me doing the engine programme, I would at least look at this lean-WOT-knock-mitigation idea early on and get some real data.

[xpensive]

...
- 2.5 bar abs boost
...

Perhaps a detail, but the above is a contradiction, if the turbo pressure was 2.5 bar absolute, it means 1.5 bar boost.

[gruntguru]

Sorry - I will use "MAP" from now on. Or how about IPR (for Intake Pressure Ratio), then I won't have to type "bar" either.

[xpensive]

2.5 bar absolute will do just fine.

[Pierce89]

Agreed. It is undoubtedly a fine balancing act and it will be interesting when the details of what they have achieved can be revealed.

It pays to remember what Honda achieved in 1988. 26 years ago:
- 2.5 bar abs boost
- 9.4:1 CR
- 70*C charge temperature
- Lambda ratio 0.98 at full power and 12,000 rpm
- 32.2% thermal efficiency (Mercedes claims over 40% in 2014)
and remember this was an "airflow limited" engine with race fuel consumption restrictions. Todays engines are "fuel flow limited" which creates a direct relationship between power and efficiency which did not exist in 1988. Remember also the Honda engine did not have DI. If the DI system is unable to produce significant charge stratification at 10,500 rpm what is the benefit of having it?

Did you really write that last question? Do you not understand the compression/temperature benefits of high pressure GDI with a very late injection? Surely, if you're talking stratified charges you should already understand these benefits.

Besides, you don't have to have "significant" stratification to run slightly richer around the plug tip. The "fully stratified" systems with no fuel at all close to the cylinder walls effectively reduce your volumetric efficiency in exchange for the increase in thermal efficiency. In other words, you've got a smaller less powerful but very efficient engine. That's why its not done in WOT situations. It reduces overall power and the extra boost requirement would reduce rcoverable power at the turbine too.

[gruntguru]

Agreed there are other benefits to GDI especially in-cylinder evaporation and its effect on charge temperature. "Very late injection" is only possible at part load and has limited relevance to F1. Hopefully technology will reach the point where this changes.

Fully stratified charge "making them smaller" will not reduce power in these F1 engines. As shown earlier in this thread these engines are capable of breathing far more air than is needed to burn the fuel allocation.

The "extra boost requirement" will increase mass flow and pressure ratio through the turbine and more than compensate for the additional compressor work required. Efficiency of a gas turbine (Brayton cycle) with a fixed fuel (heat) input increases with pressure ratio.

[gruntguru]

2.5 bar absolute will do just fine.

Not enough information. Needs to be 2.5 bar absolute "something" e.g. "intake pressure".

[Wayne DR]

Did you really write that last question? Do you not understand the compression/temperature benefits of high pressure GDI with a very late injection? Surely, if you're talking stratified charges you should already understand these benefits.

Besides, you don't have to have "significant" stratification to run slightly richer around the plug tip. The "fully stratified" systems with no fuel at all close to the cylinder walls effectively reduce your volumetric efficiency in exchange for the increase in thermal efficiency. In other words, you've got a smaller less powerful but very efficient engine. That's why its not done in WOT situations. It reduces overall power and the extra boost requirement would reduce rcoverable power at the turbine too.

My understanding is the same, a Stratified Charge can only be used under light and moderate loading and not at high RPMs. A Homogeneous Charge (either stoichiometric or slightly rich) is needed at WOT for maximum power generation.

You can run lean (or even super lean), but you will not generate the same level of power as a homogeneous charge. There are no free lunches!

I wonder if any of the engine manufacturers running compression ignition (and whether they use spark assist)?