Honda Power Unit Hardware & Software

[godlameroso]

In a way, because you reduce back pressure with higher turbine speed . . .

I don't think this is right. Higher turbine speed = higher back pressure.

The turbine is a restriction to the exhaust pulses, a windmill trapped in the exhaust. So under normal circumstances, yes you have higher back pressure when you shove more air through the engine. Higher turbine speed is achieved because the pressure in the turbine is higher than the ambient pressure. If it weren't then you wouldn't have higher turbine speed. But if you're driving the turbine with the compressor, and the exhaust pulses, now you have two energy sources, and a wastegate which can in fact relieve backpressure, as the exhaust no longer needs to flow past the turbine. The wastegate doesn't have to be fully open to have a meaningful change in system backpressure. If using compressor air allows you to run higher wastegate duty cycle for the same turbine speed, you just effectively lowered system backpressure for a given turbine RPM.

[PlatinumZealot]

In a way, because you reduce back pressure with higher turbine speed . . .

I don't think this is right. Higher turbine speed = higher back pressure.

The turbine is a restriction to the exhaust pulses, a windmill trapped in the exhaust. So under normal circumstances, yes you have higher back pressure when you shove more air through the engine. Higher turbine speed is achieved because the pressure in the turbine is higher than the ambient pressure. If it weren't then you wouldn't have higher turbine speed. But if you're driving the turbine with the compressor, and the exhaust pulses, now you have two energy sources, and a wastegate which can in fact relieve backpressure, as the exhaust no longer needs to flow past the turbine. The wastegate doesn't have to be fully open to have a meaningful change in system backpressure. If using compressor air allows you to run higher wastegate duty cycle for the same turbine speed, you just effectively lowered system backpressure for a given turbine RPM.

What do you mean driving the turbine with the compressor? It's the other way around.

The turbine speed has a lot to do with the load on it. It will spin pretty fast even with a low pressure difference if the load is low. So it's three factors. Load, pressure and speed.

Opening the wastegate means your system design is not optimal. As the name implies its waste. The more suboptimal the system design the more the wastegate will have to be used.

It is opened on qualifying laps because the PU is not designed to be optimal for that sitation. (max power from ICE but zero recovery to ERS).

[saviour stivala]

Good read/reasoning at last. Anybody remember the arguments by the same people in previous threads about the formula 1 turbine being a pressure turbine?

[gruntguru]

In a way, because you reduce back pressure with higher turbine speed . . .

I don't think this is right. Higher turbine speed = higher back pressure.

The turbine is a restriction to the exhaust pulses, a windmill trapped in the exhaust. So under normal circumstances, yes you have higher back pressure when you shove more air through the engine. Higher turbine speed is achieved because the pressure in the turbine is higher than the ambient pressure. If it weren't then you wouldn't have higher turbine speed. But if you're driving the turbine with the compressor, and the exhaust pulses, now you have two energy sources, and a wastegate which can in fact relieve backpressure, as the exhaust no longer needs to flow past the turbine. The wastegate doesn't have to be fully open to have a meaningful change in system backpressure. If using compressor air allows you to run higher wastegate duty cycle for the same turbine speed, you just effectively lowered system backpressure for a given turbine RPM.

Perhaps. But if turbine speed is increased with all else held constant, it takes higher pressure to force gas inward through the turbine.

[holeindalip]

... in effect it reduces the backpressure created by the turbine to the combustion process .....

there is no (turbine) "backpressure to the combustion process"
exhaust is inherently a choked process - ie the backpressure has no effect on the power stroke

It does have an effect on cylinder scavenging and filling, which are crucial to the power stroke. As the power stroke is entirely dependent on those intermediate events, much like combustion itself is determined by intermediate reactive radicals in the fuel.

On a completely unrelated note, cooling exhaust gas could have the benefit of increasing the mass density of said gas. Afterall a limiting factor to a compressor is that the air is compressed to a point that the heat generated lowers density and with it the ability to do work. That is why intercoolers make more power, they increase the air density improving cylinder filling.

Perhaps one of the reasons fuel is necessary to power an engine is the fact that the density of combusted gases having CO2, NOx, and other molecules that are more dense than air means that you don't lose much gas density despite the high temperature. I imagine if we just heated air, it's density would be so low that there would be little to no power generated.

Are you saying cooler denser air in the hot side will drive the turbine more/better? I always thought you wanted it hot as the air expands driving it more efficiently, hence why everyone moved to wrapping everything on the hot side to put as much heat through there as possible….

[saviour stivala]

‘’Cooling exhaust gas could have the benefit of increasing the mass’’ Really wrapped reasoning. Exhaust piping to turbo wrapping which all four does keeps heat in, as it improves performance. Insulating headers with exhaust wrap is intended to keep heat in because it raises exhaust temperature as this increases gas velocities and improves scavenging of spent gasses from combustion.

[godlameroso]

there is no (turbine) "backpressure to the combustion process"
exhaust is inherently a choked process - ie the backpressure has no effect on the power stroke

It does have an effect on cylinder scavenging and filling, which are crucial to the power stroke. As the power stroke is entirely dependent on those intermediate events, much like combustion itself is determined by intermediate reactive radicals in the fuel.

On a completely unrelated note, cooling exhaust gas could have the benefit of increasing the mass density of said gas. Afterall a limiting factor to a compressor is that the air is compressed to a point that the heat generated lowers density and with it the ability to do work. That is why intercoolers make more power, they increase the air density improving cylinder filling.

Perhaps one of the reasons fuel is necessary to power an engine is the fact that the density of combusted gases having CO2, NOx, and other molecules that are more dense than air means that you don't lose much gas density despite the high temperature. I imagine if we just heated air, it's density would be so low that there would be little to no power generated.

Are you saying cooler denser air in the hot side will drive the turbine more/better? I always thought you wanted it hot as the air expands driving it more efficiently, hence why everyone moved to wrapping everything on the hot side to put as much heat through there as possible….

Depends, air density decreases greatly with temperature increase. The reason for wrapping the exhaust manifold, and exhaust, is because higher temperatures raises the Mach number, in other words, it extends the choking limit, because again lower density means less pressure rise, and hence lower back pressure. However then you get to a point where the exhaust geometry needs to be perfect to get the most power, even scratches or carbon build up can cost 3-4hp.



Air's density in particular is greatly affected by temperature. Combustion products have a density of ~1.1kg/m3 at a temperature of around 1,000C, whereas air has a density of ~.25kg/m3 at that temperature. At the temperature of combustion which is around 500-700c hotter, the relationship is even more lopsided. Particularly when you start producing NOx. In addition, the kinematic viscosity of air increases with temperature as well, so to an extent the density decrease is countered by the viscosity increase, although the relationship between all these variables are not linear so it makes it quite complex to study said relationship.

Cooler denser air flows easier, and has more momentum than a similar amount of much hotter air, however the increased density more easily creates a bottle neck and as a result increases system backpressure.

Remember Wazari-san said that turbine power and crank power are conflicting goals and finding the right compromise between the two is the big challenge with these power units.

[johnny comelately]

In ancient times before the current accuracies there was a large range of diameters of the primaries that seemingly made little difference to power, this maybe showed that flow characteristics and pulses thus generated were more important than volume.
EVO timing has a large effect too, not sure how the use of the Atkinson cycle may effect things.
Another factor is the increase in the speed of sound as the temperature goes up.
A while back weren't some teams running lower wastegate settings for qualifying?

[godlameroso]

In ancient times before the current accuracies there was a large range of diameters of the primaries that seemingly made little difference to power, this maybe showed that flow characteristics and pulses thus generated were more important than volume.
EVO timing has a large effect too, not sure how the use of the Atkinson cycle may effect things.
Another factor is the increase in the speed of sound as the temperature goes up.
A while back weren't some teams running lower wastegate settings for qualifying?

A favorite topic of mine. Having a sonic shock produces a sharp pressure peak, and a large raise in stagnation pressure, and energy lost to entropy, and reduces flow downstream. IF the pipe/passage is improperly designed, if however, the pipe/passage is carefully sculpted, the losses will be minimal even with a sonic shock until ~Mach 1.4 which seems to be the point of diminishing returns.



Here we see a flow of M=1, you see the shockwave creates a recirculation zone on the walls of the duct. The recirculation zone is the zone of increased stagnation pressure.



However, all hope is not lost, for those lines you see, the so called re-attachment shockwave, can only exist because the flow is locally accelerated by expansion fans. So if your duct achieves sonic choking, sculpting the duct in the shape of the recirculation zone, will promote the propagation of expansion fans which will actually increase the speed of the flow. In other words minimize losses.

That is the theory behind rocket engines, they try to exploit expansion fans in order to minimize losses in the engine's thrust.

[johnny comelately]

In ancient times before the current accuracies there was a large range of diameters of the primaries that seemingly made little difference to power, this maybe showed that flow characteristics and pulses thus generated were more important than volume.
EVO timing has a large effect too, not sure how the use of the Atkinson cycle may effect things.
Another factor is the increase in the speed of sound as the temperature goes up.
A while back weren't some teams running lower wastegate settings for qualifying?

A favorite topic of mine. Having a sonic shock produces a sharp pressure peak, and a large raise in stagnation pressure, and energy lost to entropy, and reduces flow downstream. IF the pipe/passage is improperly designed, if however, the pipe/passage is carefully sculpted, the losses will be minimal even with a sonic shock until ~Mach 1.4 which seems to be the point of diminishing returns.

https://files.catbox.moe/1partl.png

Here we see a flow of M=1, you see the shockwave creates a recirculation zone on the walls of the duct. The recirculation zone is the zone of increased stagnation pressure.

https://files.catbox.moe/49jb1p.png

However, all hope is not lost, for those lines you see, the so called re-attachment shockwave, can only exist because the flow is locally accelerated by expansion fans. So if your duct achieves sonic choking, sculpting the duct in the shape of the recirculation zone, will promote the propagation of expansion fans which will actually increase the speed of the flow. In other words minimize losses.

That is the theory behind rocket engines, they try to exploit expansion fans in order to minimize losses in the engine's thrust.

https://www.researchgate.net/profile/Be ... tics-3.png

That looks like classic valve seat play.

[saviour stivala]

Why do they run ‘waste-gate open settings’ ?. first of all they still do, even during the race. They do so because when needed that is the fastest way to go (the power unit – ICE + ERS produces the most power). It does so because the turbine used is a pressure turbine and so when waste-gate/s are open pressure/back pressure is relieved inside the turbine.

[J.A.W.]

In ancient times before the current accuracies there was a large range of diameters of the primaries that seemingly made little difference to power, this maybe showed that flow characteristics and pulses thus generated were more important than volume.
EVO timing has a large effect too, not sure how the use of the Atkinson cycle may effect things.
Another factor is the increase in the speed of sound as the temperature goes up.
A while back weren't some teams running lower wastegate settings for qualifying?

A favorite topic of mine. Having a sonic shock produces a sharp pressure peak, and a large raise in stagnation pressure, and energy lost to entropy, and reduces flow downstream. IF the pipe/passage is improperly designed, if however, the pipe/passage is carefully sculpted, the losses will be minimal even with a sonic shock until ~Mach 1.4 which seems to be the point of diminishing returns.

https://files.catbox.moe/1partl.png

Here we see a flow of M=1, you see the shockwave creates a recirculation zone on the walls of the duct. The recirculation zone is the zone of increased stagnation pressure.

https://files.catbox.moe/49jb1p.png

However, all hope is not lost, for those lines you see, the so called re-attachment shockwave, can only exist because the flow is locally accelerated by expansion fans. So if your duct achieves sonic choking, sculpting the duct in the shape of the recirculation zone, will promote the propagation of expansion fans which will actually increase the speed of the flow. In other words minimize losses.

That is the theory behind rocket engines, they try to exploit expansion fans in order to minimize losses in the engine's thrust.

https://www.researchgate.net/profile/Be ... tics-3.png

That looks like classic valve seat play.

You might think so J-C, however the 4T poppet-valve tends to obtund the flow, say compared to a
piston rapidly & fully clearing an exhaust port in a 2T, (which then may want a reflection-wave post
diffuser-expansion space within the pipe) whereas the rocket jet-efflux is exhausted against ambient.

[godlameroso]

A favorite topic of mine. Having a sonic shock produces a sharp pressure peak, and a large raise in stagnation pressure, and energy lost to entropy, and reduces flow downstream. IF the pipe/passage is improperly designed, if however, the pipe/passage is carefully sculpted, the losses will be minimal even with a sonic shock until ~Mach 1.4 which seems to be the point of diminishing returns.

https://files.catbox.moe/1partl.png

Here we see a flow of M=1, you see the shockwave creates a recirculation zone on the walls of the duct. The recirculation zone is the zone of increased stagnation pressure.

https://files.catbox.moe/49jb1p.png

However, all hope is not lost, for those lines you see, the so called re-attachment shockwave, can only exist because the flow is locally accelerated by expansion fans. So if your duct achieves sonic choking, sculpting the duct in the shape of the recirculation zone, will promote the propagation of expansion fans which will actually increase the speed of the flow. In other words minimize losses.

That is the theory behind rocket engines, they try to exploit expansion fans in order to minimize losses in the engine's thrust.

https://www.researchgate.net/profile/Be ... tics-3.png

That looks like classic valve seat play.

You might think so J-C, however the 4T poppet-valve tends to obtund the flow, say compared to a
piston rapidly & fully clearing an exhaust port in a 2T, (which then may want a reflection-wave post
diffuser-expansion space within the pipe) whereas the rocket jet-efflux is exhausted against ambient.

The exhaust system itself is largely at ambient, no?

[J.A.W.]

That looks like classic valve seat play.

You might think so J-C, however the 4T poppet-valve tends to obtund the flow, say compared to a
piston rapidly & fully clearing an exhaust port in a 2T, (which then may want a reflection-wave post
diffuser-expansion space within the pipe) whereas the rocket jet-efflux is exhausted against ambient.

The exhaust system itself is largely at ambient, no?

No, unless it is a type of simple short stack - 'dump tube', otherwise it forms a 'chamber' with heat/
pressure-waves/gasses contained/constrained to a certain set of parameters varying from 'ambient'.

But true, a large high-altitude rocket likewise must contend with a range of 'ambient' values,
(heat/pressure) as it ascends on up through the levels of atmosphere.

[etusch]

Honda shut down speculation over possible F1 comeback

Despite occasional rumours of a return to F1, Honda chief executive Koji Watanabe has suggested that there are no concrete plans for this, though he does not rule out the possibility altogether.

https://racingnews365.com/honda-shut-do ... dLKIeNahKA