The Road to the 50% Thermally Efficient F1 Internal Combustion Engine

[gruntguru]

However the properties of the fuels must be significant; yet are the differences between CI and HCCI so great?

There is a huge difference between premixed (typical of SI) and diffusion (typical of diesel) combustion.

HCCI is a premixed combustion regime.

It might be possible to approach the F1 combustion regime in a diesel with a form of PPCI (Partially Premixed Compression Ignition) where some of the charge is pre-mixed e.g. an early spray of fuel near BDC and the remainder of the fuel is injected near TDC to initiate combustion. This technology is fairly mature in the lab. Not sure if researchers have yet achieved HCCI using this technique.

I always thought that was exactly how the single injector TJI system worked...

Almost. TJI is spark ignited, PPCI is ignited by injecting fuel.

[gruntguru]

I was actually surprised that cars were approaching 11K.

No surprise. Under the rules, maximum fuel is only available from 10,500 - 15,000 rpm. Friction and other losses mean the lower part of that range is preferred so teams generally operate somewhere between 10,000 and 11,500.

[saviour stivala]

As per the rules maximum fuel flow is available from 10500 rpm up to a maximum of 15000 rpm, with the maximum fuel flow being 100 kg/h. So 10500 rpm is the max power speed. At any RPM above 10500 each combustion will become weaker, the more the RPM the weaker each combustion will become. When the new power unit rules were introduced the first version of the rules listed just the maximum fuel flow and did not list at what RPM the maximum fuel flow was to be reached. Because the new engine formula was all about achieving maximum power at maximum efficiency, it was realised that the engine design was being pushed into extracting maximum power possible at the mandated maximum fuel flow with an unregulated turbo boost will lead to a max power speed as low as possible. This realization prompted the complaining about the much reduced anticipated engine sound. With the result that the maximum engine RPM was upped to 15000 and the 10500 RPM was added at which the maximum fuel was to flow.

[vorticism]

Does anyone know how they arrived at that fuel rate curve? An estimated piston pressure compared to available material properties perhaps. The wide range might suggest they didn't know if piston design would incline the designers to 15k RPM or 10.5k RPM. That they hover at the low end might suggest they would go lower if they could. The balancing of reciprocating part weight, frictional losses, combustion properties.

[gruntguru]

Does anyone know how they arrived at that fuel rate curve? An estimated piston pressure compared to available material properties perhaps. The wide range might suggest they didn't know if piston design would incline the designers to 15k RPM or 10.5k RPM. That they hover at the low end might suggest they would go lower if they could. The balancing of reciprocating part weight, frictional losses, combustion properties.

They started with the 1.6 displacement, and designed the fuel curve to keep revs above 10,000 (think audio). Probably looked at what sort of MAP would be required to consume the fuel allocation at 10k (2 bar min, 3+ for lean burn) and figured those were sensible numbers.

[vorticism]

Thanks. If that's the case then they were again doing some sort futile aesthetic curation. Bizarre. All of the combustion research they've trumpeted could have been achieved in an 8, 10 or 12 cylinder format. They need to get the piano, flugelhorn, guitar, and internal combustion engine manufacturer Yamaha involved at some point.

[Zynerji]

Thanks. If that's the case then they were again doing some sort erstwhile aesthetic curation. Bizarre. All of the combustion research they've trumpeted could have been achieved in an 8, 10 or 12 cylinder format. They need to get the piano, flugelhorn, guitar, and internal combustion engine manufacturer Yamaha involved at some point.

I sooo agree with the Yamaha play!

[Stu]

Does anyone know how they arrived at that fuel rate curve? An estimated piston pressure compared to available material properties perhaps. The wide range might suggest they didn't know if piston design would incline the designers to 15k RPM or 10.5k RPM. That they hover at the low end might suggest they would go lower if they could. The balancing of reciprocating part weight, frictional losses, combustion properties.

….and originally that curve was just a cap from 10,500rpm on. Only after Ferrari were assumed to be “cheating” was a true curve introduced. But all of the noise about ‘fooling the sensor’ drowned out the bigger regulation change of a mandated peak fuelling ‘map’ to cover the full operating range of the engine in relation to engine speed/throttle operation.

[saviour stivala]

‘’They started with 1.6l displacement’’ They did so only at their second attempt at their new engine formula. And on their third attempt the maximum RPM at which their mandated maximum fuel flow would flow was added. This ‘added-to-the-rules’ so called maximum RPM at which maximum fuel flow could flow only came along after those realizing that the mandated ‘maximum of 100 kg/h’ fuel flow was going to push engine design into maximizing combustion power output on the mandated cylinder size with no limit of turbo boost into the lowest possible maximum RPM, This by maximizing max fuel flow allowed to each combustion. Sticking to 100 kg/h maximum fuel flow, the lower the RPM, The more flow could be obtained for each combustion (more fuel to burn). Technically speaking the mandated maximum ‘100 kg/h fuel flow @ maximum 10500 RPM’ is looked at as the minimum RPM that the maximum fuel flow rate could flow.

[johnny comelately]

This is our old test mule showing the dual flame jet ignition where it was cast welded inserts and went too lean (methanol) causing the burn out/in on one cylinder. Unconventional engine design, dont ask
3 mm holes, 94 mm bore

[vorticism]

….and originally that curve was just a cap from 10,500rpm on. Only after Ferrari were assumed to be “cheating” was a true curve introduced. But all of the noise about ‘fooling the sensor’ drowned out the bigger regulation change of a mandated peak fuelling ‘map’ to cover the full operating range of the engine in relation to engine speed/throttle operation.

What's the distinction between setting a fuel curve and an engine/throttle map?

[Stu]

….and originally that curve was just a cap from 10,500rpm on. Only after Ferrari were assumed to be “cheating” was a true curve introduced. But all of the noise about ‘fooling the sensor’ drowned out the bigger regulation change of a mandated peak fuelling ‘map’ to cover the full operating range of the engine in relation to engine speed/throttle operation.

What's the distinction between setting a fuel curve and an engine/throttle map?

Prior to March 2020 the fuel flow was regulated as being at a maximum of 100kg/hr at 10,500rpm and beyond, since then it has become
“ 5.2.3 Fuel mass flow must not exceed 100kg/h.
5.2.4 Below 10500rpm the fuel mass flow must not exceed Q (kg/h) = 0.009 N(rpm)+ 5.5.
5.2.5 At partial load, the fuel mass flow must not exceed the limit curve defined below:
- Q (kg/h) = 10 when the engine power is below -50kW
- Q (kg/h) = 0.257 x engine power (kW) + 22.85 when the engine power is above -50kW”

[vorticism]

….and originally that curve was just a cap from 10,500rpm on. Only after Ferrari were assumed to be “cheating” was a true curve introduced. But all of the noise about ‘fooling the sensor’ drowned out the bigger regulation change of a mandated peak fuelling ‘map’ to cover the full operating range of the engine in relation to engine speed/throttle operation.

What's the distinction between setting a fuel curve and an engine/throttle map?

Prior to March 2020 the fuel flow was regulated as being at a maximum of 100kg/hr at 10,500rpm and beyond, since then it has become
“ 5.2.3 Fuel mass flow must not exceed 100kg/h.
5.2.4 Below 10500rpm the fuel mass flow must not exceed Q (kg/h) = 0.009 N(rpm)+ 5.5.
5.2.5 At partial load, the fuel mass flow must not exceed the limit curve defined below:
- Q (kg/h) = 10 when the engine power is below -50kW
- Q (kg/h) = 0.257 x engine power (kW) + 22.85 when the engine power is above -50kW”

So fuel use was exceeded 100kg/hr before 10.5k or a greater amount than was needed up to but not exceeding 100kg/hr was being used before 10.5k.

Interesting to think that is wasn't illegal to store extra fuel in the rail after the sensor. Pipe sizing and fuel pressure would determine how much reserve fuel could be stored. Short of measure flow at the injector, everyone would have unavoidably been doing something like this. There is a phase lag between the pump and injector demand, so they would always err on the side of piling up more fuel than required in the lines after the pump.

[Stu]

They have also slowly reduced the amount of fuel that may be around the engine, now a mere 0.25l may be outside of the safety cell at any one time (supported by the comment “only enough to operate the ICE). Previously that was higher.

Originally I believe it was up to a maximum of 100kg/hr, at 10,500rpm, and may not exceed that up to the maximum rev limit of 15,000rpm.
Now that it has been updated I cannot find the exact wording.

My belief is that Ferrari were operating the engine whilst braking to boost the MGU-K regeneration and give them a substantial electrical boost (whether through the MGU-K or MGU-H) on acceleration. Everyone just goes the route of “but they added a second fuel flow sensor”. The reg would not have been so precisely re-written if it had been as simple as that.

[Tommy Cookers]

only 5.2.5 was new in 2020
5.2.4 was always there

seemingly hundreds of posts were made strenuously denying any possibility of or legal window for fuel accumulation

I think that 5.2.5 is somewhat limiting fuel burn for driving GU-K activity
plausibly justified to constrain this given that the teams had had years to make their PUs work 'properly'