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

[johnny comelately]

1. Richer

What mechanism do you propose to ensure this? GIven the regulatory set.

From what I understand about your question: the Mahle design, as an example, is the mechanism. It is inherently rich by design and operation.
This engine design could not work without this, as lambda 1.4 is impossible under even these normal circumstances to ignite reliably.
Pat Symonds mentions this in one of his engine descriptions: stratified.
Which regulatory set do you mean?
If it is the one about one injector per cylinder, it is ridiculous imo, 2 injectors would provide much better effect. Pat Symond mentions this towards the end of his talk. Which begs the question, as with most of the archaic rules, why the 1 injector rule?

[Zynerji]

1. Richer

What mechanism do you propose to ensure this? GIven the regulatory set.

From what I understand about your question: the Mahle design, as an example, is the mechanism. It is inherently rich by design and operation.
This engine design could not work without this, as lambda 1.4 is impossible under even these normal circumstances to ignite reliably.
Pat Symonds mentions this in one of his engine descriptions: stratified.
Which regulatory set do you mean?
If it is the one about one injector per cylinder, it is ridiculous imo, 2 injectors would provide much better effect. Pat Symond mentions this towards the end of his talk. Which begs the question, as with most of the archaic rules, why the 1 injector rule?

"Cost cutting"

[vorticism]

1. Richer

What mechanism do you propose to ensure this? GIven the regulatory set.

From what I understand about your question: the Mahle design, as an example, is the mechanism. It is inherently rich by design and operation.
This engine design could not work without this, as lambda 1.4 is impossible under even these normal circumstances to ignite reliably.
Pat Symonds mentions this in one of his engine descriptions: stratified.
Which regulatory set do you mean?
If it is the one about one injector per cylinder, it is ridiculous imo, 2 injectors would provide much better effect. Pat Symond mentions this towards the end of his talk. Which begs the question, as with most of the archaic rules, why the 1 injector rule?

The yet to be publicly seen F1 TJI prechamber, whose face, whether shaped like a disk or a thimble (who knows), is linked to the cylinder only through a series of small holes. The trick is getting both fuel and air into the prechamber through the necessarily restrictive TJI orifices, via an injector nozzle located across the cylinder head. Some points to consider:

--Logically the prechamber can never reach peak pre-combustion cylinder pressures due to filling lag through the orifices (not sure if relevant although this delay feature may allow advanced ignition earlier than otherwise possible)

--The x number of injection moments (5?) must be relied upon to both aerosol while ideally localize around the prechamber in order to maximize its a:f ratio (seems like two conflicting goals)

--Exhaust gas entrapment. The prechamber likely retains more combustion products than the cylinder again due to filling/emptying delay brought on by the orifices.

[johnny comelately]

What mechanism do you propose to ensure this? GIven the regulatory set.

From what I understand about your question: the Mahle design, as an example, is the mechanism. It is inherently rich by design and operation.
This engine design could not work without this, as lambda 1.4 is impossible under even these normal circumstances to ignite reliably.
Pat Symonds mentions this in one of his engine descriptions: stratified.
Which regulatory set do you mean?
If it is the one about one injector per cylinder, it is ridiculous imo, 2 injectors would provide much better effect. Pat Symond mentions this towards the end of his talk. Which begs the question, as with most of the archaic rules, why the 1 injector rule?

The yet to be publicly seen F1 TJI prechamber, whose face, whether shaped like a disk or a thimble (who knows), is linked to the cylinder only through a series of small holes. The trick is getting both fuel and air into the prechamber through the necessarily restrictive TJI orifices, via an injector nozzle located across the cylinder head. Some points to consider:

--Logically the prechamber can never reach peak pre-combustion cylinder pressures due to filling lag through the orifices (not sure if relevant although this delay feature may allow advanced ignition earlier than otherwise possible)



--The x number of injection moments (5?) must be relied upon to both aerosol while ideally localize around the prechamber in order to maximize its a:f ratio (seems like two conflicting goals)

--Exhaust gas entrapment. The prechamber likely retains more combustion products than the cylinder again due to filling/emptying delay brought on by the orifices.

And yet it works!

May I ask with respect, if it doesnt exist and cannot work, how do you think that these engines work?

[johnny comelately]

What mechanism do you propose to ensure this? GIven the regulatory set.

From what I understand about your question: the Mahle design, as an example, is the mechanism. It is inherently rich by design and operation.
This engine design could not work without this, as lambda 1.4 is impossible under even these normal circumstances to ignite reliably.
Pat Symonds mentions this in one of his engine descriptions: stratified.
Which regulatory set do you mean?
If it is the one about one injector per cylinder, it is ridiculous imo, 2 injectors would provide much better effect. Pat Symond mentions this towards the end of his talk. Which begs the question, as with most of the archaic rules, why the 1 injector rule?

"Cost cutting"

6 extra injectors? I cannot see that as valid (unless I am not getting your smilie)

[vorticism]

And yet it works!
utube.com/watch?v=n6Eutw0WU3U
May I ask with respect, if it doesnt exist and cannot work, how do you think that these engines work?

Note the location of the injector in the video. I'm not contesting its existence in F1, I'm asking how people suppose it works.

[johnny comelately]

Thank you for this instructive information.
It highlights the part temperatures plays, something I havent considered enough apart from rudimentary factors.
These engines are more akin to the racing diesels of Audi etc than traditional petrol engines.

Additionally, this engine philosophy is analogous to gas turbine principles where exhaust recovery is a goal and necessary.
Bringing all this together, to reimagine the traditional model and create a new and effective design is incredible (and the point of this thread)

[johnny comelately]

And yet it works!
utube.com/watch?v=n6Eutw0WU3U
May I ask with respect, if it doesnt exist and cannot work, how do you think that these engines work?

Note the location of the injector in the video. I'm not contesting its existence in F1, I'm asking how people suppose it works.

IMH (and uneducated)O:
The location of the injector next to the spark plug is paramount to produce the rich mixture (how much is another subject, but it will be inherent from other factors) to enable reliable and effective prechamber ignition.
The holes seem to be bothering you, so this is how I see the sizing calculation:
Working backwards from what is needed to combust the entire and particularly shaped main combustion chamber of 1.4 lambda in the given timeframes (another subject) will give the number (minimised to keep the diameter the largest), placement and size of the holes.
The adequate evacuation will happen because of the nature of the dynamics of the combustion.
with more than one hole the deficit from diameter (your concern) is offset by the availability of another hole/s to egress, and that is not taking into consideration the possibility that both movements may happen in all holes and simply be volumetrically efficient. The viscosity and pressures (huge and dynamic) seem to allow this.
The key point here is the need to produce adequate pressure to achieve the desired flame reach.
Most of this is found by trial and error(as I mentioned before where changing hole diameter effected the distance the flame travelled)
In my experience two parallel holes (each one's flame reaching across the crown), positioned at the edge of the bore horizontally of 3 mm diameter in a bore of 94 mm worked perfectly, so I imagine that with a single unit(and not knowing the burn characterisics of this particular fuel and considering the enormous pressures) 3 or 4 holes that only have to travel aproximately 35 mm would suffice (central and vertical placement) of diameter 1.8 mm (check that as I have acalculia) for 3 holes.
Just as important as the hole diameters is the volume of the prechamber, it also is critical to produce the flame length.

[vorticism]

Right but the injectors in the F1 engines are not located within the prechambers. For all we know at least. The fuel rails on more recent Hondas and Mercs are routed beneath the exhaust manifolds and this implies the injectors are between the exhaust valves, their nozzles located one half bore diameter from the central spark plug - TJI prechamber. Even if they have some exotic prechamber gallery routed from the spark plug to the injector nozzle, you probably wouldn't want your one and only injector to be encased in the prechamber relying on the TJI orifices to also fill the main charge with fuel prior to ignition.

[johnny comelately]

Right but the injectors in the F1 engines are not located within the prechambers. For all we know at least. The fuel rails on more recent Hondas and Mercs are routed beneath the exhaust manifolds and this implies the injectors are between the exhaust valves, their nozzles located one half bore diameter from the central spark plug - TJI prechamber. Even if they have some exotic prechamber gallery routed from the spark plug to the injector nozzle, you probably wouldn't want your one and only injector to be encased in the prechamber relying on the TJI orifices to also fill the main charge with fuel prior to ignition.

Ok, I see what you are saying. If you have any pictures of or information of the injectors "not located within the prechambers" please.
For me they have to be able to charge the ignition point with a richer mixture.
Could the position you talk about near the exhaust be a more horizontal angle, which imo is better? ( even if it is unitary)

[vorticism]

That's one of the assumptions right now for those outside F1. Horizontal injector, central spark. This is inferred by the engine photos which show three coils in expected locations, and fuel lines routed underneath the exhaust manifold, sometimes with the rail itself visible. Earlier iterations of Honda and Renault engines showed a fuel rail on top of the cam cover alongside the coils, which might be the more expected location.

Regardless I presume the injector will be outside the prechamber somewhere, again because of the filling lag between prechamber and cylinder. The question then as you bring up is how to localize the fuel plume, and how to get sufficient fuel in through the prechamber orifices. In the OP vid you said Pat mentioned stratified charge? Instead of homogeneous. I can't recall. Regardless this defines the injector design and regime. Inject as late as possible to minimize mixing? Or vise versa.

As for injector number limits it may or may not have been about cost cutting. It limited engine concepts by not permitting hybrid port injection systems, so perhaps some money was saved there on the R&D side.

[johnny comelately]

That's one of the assumptions right now for those outside F1. Horizontal injector, central spark. This is inferred by the engine photos which show three coils in expected locations, and fuel lines routed underneath the exhaust manifold, sometimes with the rail itself visible. Earlier iterations of Honda and Renault engines showed a fuel rail on top of the cam cover alongside the coils, which might be the more expected location.

Regardless I presume the injector will be outside the prechamber somewhere, again because of the filling lag between prechamber and cylinder. The question then as you bring up is how to localize the fuel plume, and how to get sufficient fuel in through the prechamber orifices. In the OP vid you said Pat mentioned stratified charge? Instead of homogeneous. I can't recall. Regardless this defines the injector design and regime. Inject as late as possible to minimize mixing? Or vise versa.

As for injector number limits it may or may not have been about cost cutting. It limited engine concepts by not permitting hybrid port injection systems, so perhaps some money was saved there on the R&D side.

So this particular discussion comes down to unitary versus split components of a "TJI" system.
We need more information.
Could the fuel line postioning you mention be for preheating the fuel?

[gruntguru]

We know from the Pat Symons lecture that the pre-chamber is integral to the spark plug. The injector is to one side of the main chamber. As I have proposed several times in other threads, the injector sprays toward the centre of the main chamber and the rich cloud of mixture is pushed into the pre-chamber during the compression stroke, while the "rich cloud" remaining in the main chamber is dispersed by tumble and squish turbulence.

The AFR in the pre-chamber can be accurately controlled by timing of the multiple pulses of fuel issuing from the injector. For example:
- firing the injector early in the intake stroke will result in a well mixed near-homogeneous charge in both chambers - similar to PFI.
- early in the compression stroke for a spray-guided stratified charge
- later in the compression stroke (when air flow into the pre-chamber is maximum) for a richer pre-chamber AFR.

Varying the proportion of fuel injected at these timings will enable control of the pre-chamber AFR.

[vorticism]

So this particular discussion comes down to unitary versus split components of a "TJI" system.
We need more information.
Could the fuel line postioning you mention be for preheating the fuel?

Probably a good way to frame it. Honda 2018 engine photos below. The steel fuel tubes are routed in front of the cam gear covers.


Not coils yet not fuel lines atop the cam covers. The fuel line makes a 180 bend after the pump (behind the CF bracket) and makes its way to the front of the engine as shown above. I don't think there's any advantage to the routing, only necessity. If fuel heating is wanted then consider the injectors are between the exhaust ports and the rail is under the header primaries although separated by thermal insulation.

Varying the proportion of fuel injected at these timings will enable control of the pre-chamber AFR.

Do you think a relatively lean a:f mix in the prechamber (compared to cylinder charge) is feasible or even unavoidable? Residual combustion products must play some role in this, there won't be much evacuation of the prechamber during the exhaust stroke beyond pressure attempting to equalize.

[johnny comelately]

So this particular discussion comes down to unitary versus split components of a "TJI" system.
We need more information.
Could the fuel line postioning you mention be for preheating the fuel?

Probably a good way to frame it. Honda 2018 engine photos below. The steel fuel tubes are routed in front of the cam gear covers.
https://i.imgur.com/a7tv6Md.png

Not coils yet not fuel lines atop the cam covers. The fuel line makes a 180 bend after the pump (behind the CF bracket) and makes its way to the front of the engine as shown above. I don't think there's any advantage to the routing, only necessity. If fuel heating is wanted then consider the injectors are between the exhaust ports and the rail is under the header primaries although separated by thermal insulation.

https://i.imgur.com/iHjmVbf.png

https://i.imgur.com/foOyYB6.png

Varying the proportion of fuel injected at these timings will enable control of the pre-chamber AFR.

Do you think a relatively lean a:f mix in the prechamber (compared to cylinder charge) is feasible or even unavoidable? It should still permit formation of jets, reduced maybe, but still enough to make the combustion regime work. Residual combustion products must play some role in this, there won't be much evacuation of the prechamber during the exhaust stroke.

good pictures, thank you
let me "digest" this
somehow when replying it reveals your text "Do you think a relatively lean a:f mix in the prechamber (compared to cylinder charge) is feasible or even unavoidable? It should still permit formation of jets, reduced maybe, but still enough to make the combustion regime work. Residual combustion products must play some role in this, there won't be much evacuation of the prechamber during the exhaust stroke."
if this is meant to be there:
Like I said before I cannot imagine how being leaner than 1.4 could be feasible.
during pressured combustion you get a suck back effect which is probably aiding evacuation rather than just the pressure drop from EVO