Honda Power Unit Hardware & Software

[trinidefender]

Peak gas temperature is >2,600K though.

Peak gas temperature is ~1800K at peak thermal efficiency, this is in many optical and laser imaging diagnosis.

I was under the impression these engines produced a fair bit of NOx which would be hard to do at such low temps.

Or am I confusing gas with flame temperature?

I don't think that it was ever explicitly stated that it was NOx that these PU's produce high levels of. It was just stated that the exhaust emissions weren't environmentally friendly or healthy to those around it.

If I had to guess, it would be fuel additives that would be the major cause of any harmful emissions.

If high levels of NOx are also present then I would imagine that they would be formed from the very high temperature flame jets.

Gas turbines suffer from that problem (where a lot of the development money is going to reduce NOx outputs on commercial turbofans). Even though the overall air:fuel ratio is very high, the combustion event itself is limited to a very small area where the mixture is much closer to stoichiometric. Ergo high combustion temperatures and high levels of NOx.

[PlatinumZealot]

Peak gas temperature is >2,600K though.

Peak gas temperature is ~1800K at peak thermal efficiency, this is in many optical and laser imaging diagnosis.

I was under the impression these engines produced a fair bit of NOx which would be hard to do at such low temps.

Or am I confusing gas with flame temperature?

2,600K is the adiabatic flame temperature.

[PlatinumZealot]

I don't think that it was ever explicitly stated that it was NOx that these PU's produce high levels of. It was just stated that the exhaust emissions weren't environmentally friendly or healthy to those around it.

If I had to guess, it would be fuel additives that would be the major cause of any harmful emissions.

If high levels of NOx are also present then I would imagine that they would be formed from the very high temperature flame jets.

Gas turbines suffer from that problem (where a lot of the development money is going to reduce NOx outputs on commercial turbofans). Even though the overall air:fuel ratio is very high, the combustion event itself is limited to a very small area where the mixture is much closer to stoichiometric. Ergo high combustion temperatures and high levels of NOx.

Yeah the SAE papers showed high levels of NOx.

[trinidefender]

I don't think that it was ever explicitly stated that it was NOx that these PU's produce high levels of. It was just stated that the exhaust emissions weren't environmentally friendly or healthy to those around it.

If I had to guess, it would be fuel additives that would be the major cause of any harmful emissions.

If high levels of NOx are also present then I would imagine that they would be formed from the very high temperature flame jets.

Gas turbines suffer from that problem (where a lot of the development money is going to reduce NOx outputs on commercial turbofans). Even though the overall air:fuel ratio is very high, the combustion event itself is limited to a very small area where the mixture is much closer to stoichiometric. Ergo high combustion temperatures and high levels of NOx.

Yeah the SAE papers showed high levels of NOx.

Oh well evidently I'm a muppet and missed those papers . Do you mind posting them or sending them via PM?

If that's the case then I would have to say it would have to do with high flame fronts on the jets.

[gruntguru]

The papers I've read on TJI mostly show very low engine-out NOx at the typically lean mixtures.

[saviour stivala]

"It's turbulent jet ignition - TJI. Used by all F1 engines" when I as much as made a statement like that I was asked to sustain/proof what I am saying,

[MarcJ]

Peak gas temperature is >2,600K though.

Peak gas temperature is ~1800K at peak thermal efficiency, this is in many optical and laser imaging diagnosis.

I was under the impression these engines produced a fair bit of NOx which would be hard to do at such low temps.

Or am I confusing gas with flame temperature?

At 1800K there's no NOx as it's formation temperature is above this. Only NOx is from prechamber combustion.
Peak thermal efficiency @ lambda 1.85 in tested engines and the RCM rigs rapid cumbustion machines.
F1 run high pressure like the RCM.

[henry]

.... TJI is very different to CVCC. Pre-chamber volume is much smaller.

I feel we ought to be able to calculate the volume. Mahle say their TJI pre-chamber use 2-3% of the fuel consumed. If I assume the AFR in the pre-chamber is 12:1 and in the main chamber 20:1 I get a volume of 4 to 5cc. That doesn’t include the volume of the fuel which may add a little.

Prechamber is nominally 1-2cc for automotive sized cylinders. Prechamber volume had me uncertain for a long while.

Thanks for that. If those volumes and Mahle’s claimed fuel percentage are combined that suggests quite a low AFR. Very rich. Maybe they need a rich mixture to generate enough active ingredients for the jets.

[godlameroso]

I feel we ought to be able to calculate the volume. Mahle say their TJI pre-chamber use 2-3% of the fuel consumed. If I assume the AFR in the pre-chamber is 12:1 and in the main chamber 20:1 I get a volume of 4 to 5cc. That doesn’t include the volume of the fuel which may add a little.

Prechamber is nominally 1-2cc for automotive sized cylinders. Prechamber volume had me uncertain for a long while.

Thanks for that. If those volumes and Mahle’s claimed fuel percentage are combined that suggests quite a low AFR. Very rich. Maybe they need a rich mixture to generate enough active ingredients for the jets.

The radical chain reaction is the key to modeling the combustion process in these engines. There is something like 20,000 chemical reactions that happen in a few nano seconds after the spark plug fires that basically determine everything afterwards. Modeling this accurately has been key to development and why Mercedes doesn't believe the limits of this formula have been reached.

[PlatinumZealot]

Yeah the SAE papers showed high levels of NOx.

Oh well evidently I'm a muppet and missed those papers . Do you mind posting them or sending them via PM?

If that's the case then I would have to say it would have to do with high flame fronts on the jets.

My memory actually was a little faded when I typed that! I have the papers on my computer... but anyway I know the F1 engines exhaust high NOx. If you are reading it now, the NOx from combustion in the SAE paper is about the same trend as regular spark ignition as lambda increases. The ignition type doesn't really matter much actually, as the peak NOx is near 15:1 AFR and falls off similarly for both types. So yeah this argument is moot anyway.

However I must mention that the part of the catalytic converter that reduces NOx to N2 and O2 only work well in reducing conditions (low oxygen). The ultra lean burn mode in F1, whether you want to use TJI or whatever technology, I assume, produces O2 levels that the NOx reduction part of the typical catalytic converter wont be effective at. Advanced converting technology is required. Lean NOx Catalyst (LNC), Selective Catalytic Reduction (SCR) and the Lean NOx Trap (LNT) are solutions being developed.

The papers I've read on TJI mostly show very low engine-out NOx at the typically lean mixtures.

Yes. For both types.. there are some other lean burn engines that achieve 1.5 lambda without TJI (but only at low rpm low load).

[MarcJ]

I don't think that it was ever explicitly stated that it was NOx that these PU's produce high levels of. It was just stated that the exhaust emissions weren't environmentally friendly or healthy to those around it.

If I had to guess, it would be fuel additives that would be the major cause of any harmful emissions.

If high levels of NOx are also present then I would imagine that they would be formed from the very high temperature flame jets.

Gas turbines suffer from that problem (where a lot of the development money is going to reduce NOx outputs on commercial turbofans). Even though the overall air:fuel ratio is very high, the combustion event itself is limited to a very small area where the mixture is much closer to stoichiometric. Ergo high combustion temperatures and high levels of NOx.

Yeah the SAE papers showed high levels of NOx.

While some of us recognise someone being funny, many won't so please use facts.

With ultra lean NOx emissions drop by 99.75% down to 2 or 3 parts per million.

[MarcJ]

Prechamber is nominally 1-2cc for automotive sized cylinders. Prechamber volume had me uncertain for a long while.

Thanks for that. If those volumes and Mahle’s claimed fuel percentage are combined that suggests quite a low AFR. Very rich. Maybe they need a rich mixture to generate enough active ingredients for the jets.

The radical chain reaction is the key to modeling the combustion process in these engines. There is something like 20,000 chemical reactions that happen in a few nano seconds after the spark plug fires that basically determine everything afterwards. Modeling this accurately has been key to development and why Mercedes doesn't believe the limits of this formula have been reached.

The rate coefficients of intermediate reactions are not known for all species and only to a few digits accuracy. Mostly it's guessed at, cuz they needed a number, and they get it wrong and they calculate off each other.

The active thermodynamics rate coefficients effort is trying to minimise the lack of accuracy. ATCC site.
Rates are much slower in the microseconds range, temperature effects rate and negative temperature coefficient reverses this behavior, reducing the species number modeled down to a few dozen is essential for compute power available even using 1.25 million cores.
SpaceX have at least moved this to GPU architecture where you have 4,000 high performance cores per chip. They perform simulations in a weekend more accurately than a million dollar server farm does in weeks on their standard engineering workstation.

[subcritical71]

With ultra lean NOx emissions drop by 99.75% down to 2 or 3 parts per million.

2 to 3 ppm. I would have never guessed a race engine would ever approach that level.

[MarcJ]

With ultra lean NOx emissions drop by 99.75% down to 2 or 3 parts per million.

2 to 3 ppm. I would have never guessed a race engine would ever approach that level.

RCM where piston rapidly compresses and holds compression for optical high speed imaging gives researchers good data.
TJI relieves engines of stoichiometry limited combustion and their issues. Be good if li-ion cells had a similar major improvement their want to be a solid fuel bomb.

[Tommy Cookers]

With ultra lean NOx emissions drop by 99.75% down to 2 or 3 parts per million.

2 to 3 ppm. :shock: I would have never guessed a race engine would ever approach that level.

imo it doesn't because it chooses the highest possible in-cycle temperature to get highest power