How are burnt pistons avoided at lean AFR seen in F1 hybrid engines??

[n4rf]

we have seen from Honda via Green Car Congress that gasoline homogeneous 2 lambda is possible ......
only with port injection (charge preparation) combined with charge heating combined with a lot of turbulence, and only at low rpm

unless the F1 fuel has the combustion properties of a small gas molecule how will it combust fast and fully beyond 2 ?
(by stuffing it with 'natural' dissolved propane/ethane as I suggested 2-3 years ago, and maybe the pre-chamber/TJI is mainly such gas ?)

Regarding homogeneous Lambda 2: The current development is for DI, no charge heating and significant rpm and load range (basically the part of the engine map you can cover with the amount of air you can provide at a certain engine speed with the given turbocharger). But that's a side note here, because that's development for series production. The one I'm talking about is not even involved in F1.

The "standard" approach to get really lean (beyond lambda 2) is to go for a stratified combustion system, so inhomogeneous charge preparation where you have an ignitable air/fuel mixture at the spark plug, but not close to the surfaces of the combustion chamber. That also has benefits with the amount of heat transferred to the cylinder, piston and head. However, the charge motion design is quite a challenge, especially over the time of a production vehicle, not so much for motorsport. Hence, only Mercedes is still doing it in a couple of engines for series production.
For F1, I would assume that some kind of inhomogeneous charge preparation takes place, what with the alleged prechamber/TJI situation of different manufacturers and what not. That's probably all I should say in that regard, since it's one of the more closely guarded areas of these PUs.

The findings from the current F1 developments should be interesting for future road use to some regard, which is interesting. Since in the EU WLTP+RDE regulations are now relevant, there's very little chance to avoid the GPF and fuel consumption targets are going to be more difficult. Maybe that will allow for the increased costs of lean exhaust aftertreatment for gasoline engines. That would open the chance of seriously lean burning engines with immense potential in terms of thermal efficiency. Interesting times ahead

[gruntguru]

we have seen from Honda via Green Car Congress that gasoline homogeneous 2 lambda is possible ......
only with port injection (charge preparation) combined with charge heating combined with a lot of turbulence, and only at low rpm

unless the F1 fuel has the combustion properties of a small gas molecule how will it combust fast and fully beyond 2 ?
(by stuffing it with 'natural' dissolved propane/ethane as I suggested 2-3 years ago, and maybe the pre-chamber/TJI is mainly such gas ?)

In terms of lean-limit extension, TJI is a significant step beyond what Honda did in the Green Car Congress article. Lambda 2.0 is straightforward using TJI and without the intake heating and mixing used by Honda.

[n4rf]

Just as an update from discussions I've had with a number of colleagues that are also involved in the latest research for gasoline engines (I'm more on the controls side of things):
We think the most likely is, that the teams are running homogeneous charge in the region of lambda 1.2 to 1.5. The pre-chamber might very well be a "conventional" pre-chamber spark-plug, which has been in research heavily some almost 10 years ago. The tricky part is, to get the spray targeting and the injection timing of the DI injectors just right, so the perfect amount of fuel gets into the pre-chamber to achieve a desirable combustion behaviour inside it. This combustion will then push out through all of the holes in the pre-chamber in order to ignite the charge inside the cylinder as fast as possible. Whether or not there are flames coming out of the pre-chamber or just a high-velocity flow of combustion-products with a high temperature, this is both possible and an interesting discussion point. Basically depends on the size of the holes (below a certain size, they stop the flames).
Generally, the mentioned lambda range will give you the best thermal efficiency. However, the burn velocity tends to be low, which in turn reduces the thermal efficiency of the engine. From a theoretical standpoint, the ideal situation would be to burn the entire charge in one instance. The pre-chamber system helps with achieving exactly that.
So, in general, the technologies that are used are not necessarily new. It's just that they have taken it to the next level, with the sheer amount of resources these manufacturers have. Especially considering, there's almost no price-limit to the engines and at the same time no emissions legislations.
The problem with the, presumably, used lambda-range is, that it is precisely, where the NOx emissions have their peak in an emissions over lambda diagram. Thus, it is questionable, whether this will be road relevant in the future. Certainly only with lean exhaust after treatment measures that are not necessary for lambda 1 operation.
Another extreme are the immense combustion pressures and pressure gradients that you get from this combustion process. Certainly a big mechanical challenge for the piston, crankshaft, conrod and conrod-bearing.

[gruntguru]

The road relevance will come with TJI plus auxiliary injector which has been capable of lambda 2.0+ and single digit NOx.

[PlatinumZealot]

The problem with the, presumably, used lambda-range is, that it is precisely, where the NOx emissions have their peak in an emissions over lambda diagram. Thus, it is questionable, whether this will be road relevant in the future. Certainly only with lean exhaust after treatment measures that are not necessary for lambda 1 operation.

Interesting. Andy Cowell did say that these engines are down-right nasty towards the environment.

[J.A.W.]

...Andy Cowell did say that these engines are down-right nasty towards the environment.

Yeah... no news as such, there though.. & since when, has GP racing - ever actually been 'green'?

Like, apart from from putative grandstanding, such as loudly noting a ban on heavy TEL fuel dosing..
..but slyly still allowing TEL usage in fuel ( let alone lubricants) - well beyond road-legal 'unleaded' levels..

[PlatinumZealot]

Exactly my gripe with this "Fuel flow limit." It is smoke and mirrors. It makes the engines seem green but they actually aren't. The rear jack-man probably loses a few years of his life standing behind those things.

[JonoNic]

I recently learnt that fuel can be microwaved to boiling point without combustion taking place unless an external ignition point is created. (Yes, a very stupid experiment but with a very boring outcome - absolutely no one was harmed ). The fuel boiled quickly once it was microwaved.

My question is: Would it be possible to heat fuel by microwaves to speed up the filling of the combustion and pre-combustion chamber?

As we all know that rapidly moving particles are excited neighbouring particles and eventually moves away from each other as in a gaseous state.

[gruntguru]

No need for microwaves. Can use coolant or exhaust heat and a heat exchanger to heat the fuel.

[gruntguru]

Exactly my gripe with this "Fuel flow limit." It is smoke and mirrors. It makes the engines seem green but they actually aren't. The rear jack-man probably loses a few years of his life standing behind those things.

The cars are undoubtedly "greener" if not totally "green". The quantity of fuel burnt alone tells you a lot about emissions. Of course the big one is the technology being developed - which will make a difference to road car emissions and efficiency.

And then you have the reduction in noise pollution . . .

[J.A.W.]

Exactly my gripe with this "Fuel flow limit." It is smoke and mirrors. It makes the engines seem green but they actually aren't. The rear jack-man probably loses a few years of his life standing behind those things.

The cars are undoubtedly "greener" if not totally "green". The quantity of fuel burnt alone tells you a lot about emissions. Of course the big one is the technology being developed - which will make a difference to road car emissions and efficiency.

And then you have the reduction in noise pollution . . .

Classic!

Sound quality, & not noise volume? Or is it reverse-wise ?

( & quietly, best not mention the reports of excessive lubricant consumption..
..the mysteriously unknown/unregulated composition of which..
..would likely rapidly poison the green mandated exhaust cleansing catalysts..
..that is - if - GP machines were fitted with 'em..)

[n4rf]

I'm quite certain, that these engines produce significantly more NOx emissions than ANY F1 engine that has ever been raced, simply due to the fact, that up until now, engines have been run a bit rich at higher engine loads and the NOx peak over lambda happens to almost coincide with the peak thermal efficiency of the combustion.

However, that is not to say, these engines don't have any relevance. There is existing technology for after treatment of NOx emissions. The problem is, that in the range they probably use in F1, you would have to regenerate a lean NOx trap so frequently, the fuel consumption benefit would be reduced a lot. And for SCR systems you would have to refill frequently at the gas station, also increasing the costs - interesting calculation to balance.
So you either go really lean, like >1.6 or 1.8 or you just stay at 1.0 and use the sweet old 3-way catalyst.
The problem with really lean mixtures is the burn velocity, which just goes down dramatically. This then reduces the effiency benefits because you deviate from the ideal process. Nevertheless, it should still be worth it in efficiency terms, if handled correctly. The problem is eventually gonna be the operating range of the engine. You will need immense amounts of air to achieve higher loads (not even speaking of pre-ignition and other combustion problems), while maintaining the capability for low loads and fast transient response (i.e. boost pressure build up). Conventional turbocharging is not feasible for that. Add an electric compressor and you might be fine.
(TJI is a method to increase the burn velocity with really lean mixtures, HCCI is another option, another name for TJI is just pre-chamber, which is not particularly new, but hasn't been reasonable cost-wise thus far)

Simply put: Costs will only go up for the next generation of gasoline engines (not that diesels are any better).

I am still convinced, that the current F1 engines have much more relevance to future road engines than many might think. For me personally, the controls side of it is just amazing and also quite similarly to what I'm facing with developing ECU functionalities for use in road cars in 5-10 years. Basically managing an increasing number of sources for torque (positive and negative) while maintaining the maximum efficiency, without the driver noticing any change in the vehicle behaviour when something gets activated/deactivated. Had an interesting chat about that with someone from Mercedes AMG HPP last year.

[gruntguru]

Judging from reports on boost pressure (anywhere from 3 to 5 bar abs) it would appear that full power lambda ratios are in fact greater than 1.6. Further evidence to suggest this can be found in TJI papers which show peak ITE at around 2.0. (At 2.0 these would be the lowest NOx producing F1 engines of all time with less than 0.05 g/kwh).

[J.A.W.]

Judging from reports on boost pressure (anywhere from 3 to 5 bar abs) it would appear that full power lambda ratios are in fact greater than 1.6. Further evidence to suggest this can be found in TJI papers which show peak ITE at around 2.0. (At 2.0 these would be the lowest NOx producing F1 engines of all time with less than 0.05 g/kwh).

What about HC emissions though.. burning through ~20-1 fuel-to-lubricant ratio would never cut it..
That's no better ( likely worse) than 2T G.P. bike lube-oil consumption, & they were banned for it..

Curiously, HC & NOx emissions are often paired in reg's tests,
& current 2T Evinrude DI engines better 4T rivals in NOx & match them in HC..

[Edax]

The only rules regarding pistons are that they can't be Ti, Mg, MMC's Tg, intermetallic materials(ie no half and half metals), less than .25% berillium in the alloy. As well as no alloys containing more than 5% by weight of Platinum, Ruthenium, Iridium or Rhenium. Finally the pistons have to be no less than 300g each.

Note that steel is mostly iron and only small changes can have profound effects on the strength, ductility, hardness and heat rejection of an alloy, not to mention that you can have a .8mm coating of whatever you want.

True. With the current coating technology you can have a dense and conformal layer of just about anything you like and any thickness you want if you have the patience and money.

The car industry is a penny business, everything is dominated by cost, performance just has to be adequate enough have lifetime and to prevent too many recalls. Engine technology between F1 and cars might be comparable but material selection and manufacturing certainly not.

Even at the restrictions on exots, you still have heaps of high temperature alloys available, which from a price perspective wouldn't work for road cars, but could give serious benefit. In the 90's I had a brief encounter with f1 manufacturing. Back then they made extensive use of thick plasma and HVOF sprayed coatings for thermal management, I don't think that has changed today. If anything the advance of jet engine technology has only extended the availability of semi off the shelf solutions to extend the thermal, mechanical and tribological envelope of materials like aluminum.