Honda Power Unit Hardware & Software

[subcritical71]

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta. High combustion temps are what causes these engines to produce NOx.

Peak power is at peak TE. So 'best efficiency' and max power can't be at different AFR.

Every ICE engine I have seen has a different AFR for best efficiency and max power. Is there something about an F1 car that makes it different?

[dren]

Since the rate is capped, it's assumed max efficiency is aimed at the max fuel rate which would give you your max power.

[subcritical71]

My general understanding is that with a lower AFR you reach a point with max power - I think this is where the assumption that max power is at 10,500RPM as this is where you have max fueling rate with lowest engine speed.

My understanding is also with a higher AFR you reach a point with max efficiency. Since only the fuel rate is capped, the mixture can still be leaned out to a desired AFR to get somewhere at or between these two points (eff vs pwr), depending on mapping.

[saviour stivala]

Since the rate is capped, it's assumed max efficiency is aimed at the max fuel rate which would give you your max power.

Yes exactly. And if the max capped fuel rate wasn’t capped at max RPM these engines would have been designed to run at a much slower maximum power speed than 10500RPM.

[godlameroso]

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta. High combustion temps are what causes these engines to produce NOx.

Peak power is at peak TE. So 'best efficiency' and max power can't be at different AFR.

That's a good point. Naturally there's a compromise for fuel consumption and power, and the most fuel frugal mode may not be the most efficient from a TE point of view. Or the most TE mode may not be the mode that gives the most energy for turbine recovery.

[saviour stivala]

Maximum fuel flow rate is capped and tied to a maximum RPM. Beyond that maximum power speed the engine will not produce any additional power. (100kg/h max fuel flow@ 10500RPM) sets the max power speed.

[Tommy Cookers]

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta...

no
imagine a turbo engine at stoichiometric AFR and 100 kg/hr fuel rate
about 30% of the fuel's heat must be taken and dumped by the coolant and some of the remainder is converted to work
now imagine doubling the MAP to give a 2 lambda AFR at the same 100 kg/hr fuel rate
the fuel heat released is the same but this heat is spread over twice the mass of air - so the temperature is lower
because the temperature is lower the amount of cooling needed is disproportionately lower
(guessing - maybe if we burned hydrogen at a 10 lambda AFR we might need no cooling)

this is the heat dilution engine
it's more efficient because more of the fuel's heat is available for conversion to work
it's more efficient as long as the increase in air mass is free of work cost (by turbocharging)
the practical limit to HD is how lean a mixture can be combusted properly - this depends on the main and prechamber fuels
HD is much less good with NA

the questions here are what MAP and what AFR are used
quite easy to answer the AFR question if we know the MAP and can assume they use conventional valve timings
the existence of prechambers may have answered the AFR question

[63l8qrrfy6]

Oké. But why do they do that when efficiency is best at lambda 2. Think the graph is not completely representative for gasoline as this is LNG, but it won't be much different, or would it?

One might think that big maritime engines are a lot different and even "simple", but lean burn and 3 bar turbo pressure is quite common in the business. Newest engine has 5 bar and sequential turbocharging and is 51% efficient. For maritime engines, efficiency has always been important, and easier to achieve because they mostly run close to full power, unlike car engines, but like nowadays F1.

I think there are quite some parallels to find.

Yes - I agree there are some very interesting similarities.

Even though large natural gas engines operate at relatively low speeds (actually off the top of my head they tend to run slower than a similarly sized diesel engine) their bore size is limited by the ability to combust the charge quick enough as well as difficulty in igniting very lean mixtures.

These issues are addressed by employing .. drum roll .. TJI! Well not exactly, but a very similar principle - a pre-chamber which is either fed by a separate fuel circuit (known in the industry as a fuel fed pre-chamber) or a so called passive pre chamber which is filled during the compression stroke with air fuel mixture that has been delivered to the cylinder in a conventional manner (air-fuel is pre-mixed in these engine, sometime even before the turbo(s)). The pre-chamber is either part of the spark-plug or part of the cylinder head (in which case it is referred to as 'permanent').

Modern permanent passive pre chamber (PPPC) natural gas engines can run with peak cylinder pressures of around 240 bar and operate on a very narrow band between knock and misfire. Actually many designs employ separate cylinder heads for each cylinder (mostly due to servicing requirements) that can survive excessive cylinder pressures caused by the combustion of abnormally large air/fuel charges caused by misfire on previous cycles. In these cases the heads actually lift and allow the excess pressure to vent to the atmosphere. In some extreme cases the air-fuel mixture self-ignites in the intake manifold ( it is common to pre-mix before the turbo since many of these engines run off pipe-line gas and make do without high pressure fuel pumps) and the pressure rise is high enough to force the intake valves open.
Fortunately these large industrial engines only operate at fixed engine speed and combustion can be optimized relatively easily.

I think F1 engines also operate somewhere just between knock and misfire.

[PlatinumZealot]

I am an absolute noob (on this front, as well as many others ) but before I saw the TJI "pre chamber" spark plugs (a mild let down) I envisioned a "pre chamber" as a small room above the cylinder with several thin hollow channels running from that room and exiting into the main cylinder side walls from all sides, introducing the sparks from all sides at the same time.

That is actually a VERY interesting concept...
In F1 the valves take up most of the top of the combustion chamber so those channels cannot exist internally. If you have a channel on the surface though.. that might work.. you can have shaped valves but they cannot be allowed to rotate. Not to mention it is more weight.. but interesting idea. Surface friction will also slow the jets.

[PlatinumZealot]

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta. High combustion temps are what causes these engines to produce NOx.

Peak power is at peak TE. So 'best efficiency' and max power can't be at different AFR.

Every ICE engine I have seen has a different AFR for best efficiency and max power. Is there something about an F1 car that makes it different?

That is after LOSSES and ILL EFFECTS!! that are not mentioned.
For a street car you can get the highest power capability at around 12.6 AFR.. but the efficiency is crap at these AFR. IF however the friction was low, combustion was good, no knocking, more heat is transferred into the air, the expansion is good... The highest power at a given rpm would actually be where there is best efficiency.
In other words we are not fuel limited in street cars.. so we can be dumping a tonne of fuel to get high power levels but this amount of fuel is required because of losses and negative effects.

[subcritical71]

Peak power is at peak TE. So 'best efficiency' and max power can't be at different AFR.

Every ICE engine I have seen has a different AFR for best efficiency and max power. Is there something about an F1 car that makes it different?

That is after LOSSES and ILL EFFECTS!! that are not mentioned.
For a street car you can get the highest power capability at around 12.6 AFR.. but the efficiency is crap at these AFR. IF however the friction was low, combustion was good, no knocking, more heat is transferred into the air, the expansion is good... The highest power at a given rpm would actually be where there is best efficiency.
In other words we are not fuel limited in street cars.. so we can be dumping a tonne of fuel to get high power levels but this amount of fuel is required because of losses and negative effects.

I think I get it, but as you say I am also used to fuel rates which are not limited. I’ll have to hit the ‘I believe’ button on this one until I can understand it better. Thx!

[godlameroso]

Efficiency is best ~lambda 1.2-1.4, and max power is near stoich for these engines. Power comes from heating the compressed air crammed in the CC, the most expansion of that compressed air comes from a high temperature delta...

no
imagine a turbo engine at stoichiometric AFR and 100 kg/hr fuel rate
about 30% of the fuel's heat must be taken and dumped by the coolant and some of the remainder is converted to work
now imagine doubling the MAP to give a 2 lambda AFR at the same 100 kg/hr fuel rate
the fuel heat released is the same but this heat is spread over twice the mass of air - so the temperature is lower
because the temperature is lower the amount of cooling needed is disproportionately lower
(guessing - maybe if we burned hydrogen at a 10 lambda AFR we might need no cooling)

this is the heat dilution engine
it's more efficient because more of the fuel's heat is available for conversion to work
it's more efficient as long as the increase in air mass is free of work cost (by turbocharging)
the practical limit to HD is how lean a mixture can be combusted properly - this depends on the main and prechamber fuels
HD is much less good with NA

the questions here are what MAP and what AFR are used
quite easy to answer the AFR question if we know the MAP and can assume they use conventional valve timings
the existence of prechambers may have answered the AFR question

Prechamber or not, flame out would happen somewhere around 1.6, so for gasoline that would be a practical limit. I would guess that due to there being large amounts of NOx associated with these engines, they would operate around 1.2 - 1.4. Where a normal gasoline engine would operate around .8 or .7, these power units are on the other side of stoich. And yes you are correct, since you have such fine control over the AFR due to the turbo being able to operate at a desired speed independent of engine speed. I suspect the MGU-H is such a powerful tool for efficiency because it can make sure the AFR is spot on for ideal combustion at all times, just as much as it's capable of harvesting energy.

[godlameroso]

I am an absolute noob (on this front, as well as many others ) but before I saw the TJI "pre chamber" spark plugs (a mild let down) I envisioned a "pre chamber" as a small room above the cylinder with several thin hollow channels running from that room and exiting into the main cylinder side walls from all sides, introducing the sparks from all sides at the same time.

That is actually a VERY interesting concept...
In F1 the valves take up most of the top of the combustion chamber so those channels cannot exist internally. If you have a channel on the surface though.. that might work.. you can have shaped valves but they cannot be allowed to rotate. Not to mention it is more weight.. but interesting idea. Surface friction will also slow the jets.

Poppet valves rotate. It's a design feature, it's a good way to keep valve seats concentric and sealing.

[Bandit1216]

Haha. Nice that I've started a discussion .

I'm NOT saying big engines are 100% the same, but there are parallels. After all, no matter how big and slow, a mm is still a mm, and a second still a second, and a calorie still a calorie, right. They run slower, because the are bigger. The largest engine the company I work for makes, runs 72 rmp (no I did not forget a zero) but the stoke is almost 3,5 meters. Duh.

For sure maximum power for hybrid F1 would be a different thing, but max efficiency is what counts when your fuelflow is limited. With max power they would run out of fuel 2/3 in the race.

I even think the hybrid F1's will make good show cars in the future. When not limited on fuel and running so hot, they can last a lot longer. And without having to harness energy all the time, the waste gate can open a sound will be better.

[Bandit1216]

I am an absolute noob (on this front, as well as many others ) but before I saw the TJI "pre chamber" spark plugs (a mild let down) I envisioned a "pre chamber" as a small room above the cylinder with several thin hollow channels running from that room and exiting into the main cylinder side walls from all sides, introducing the sparks from all sides at the same time.

That is actually a VERY interesting concept...
In F1 the valves take up most of the top of the combustion chamber so those channels cannot exist internally. If you have a channel on the surface though.. that might work.. you can have shaped valves but they cannot be allowed to rotate. Not to mention it is more weight.. but interesting idea. Surface friction will also slow the jets.

Poppet valves rotate. It's a design feature, it's a good way to keep valve seats concentric and sealing.

https://www.youtube.com/watch?v=kFbfHF9gzTY

Wouldn't that only work when you use both? I mean from the side walls to the middle is 1/2 of the bore. From the middle to the side is also 1/2 of the bore.