cold fuel?

[thewave]

Slightly off topic, but reading the F1 website about restrictions, it appears the pinnacle of motor racing is severely restricted by regulations.

However, I can see that by maintaining strict regulations, they are creating less room for massive steps forward in technology, and thus creating a more level playing field (of sorts)

[Scuffers]

WilliBetz said:

I've not seen research to suggest that intake air temperature materially influences atomisation, nor can I think of any novel way to influence the intake air temperature. Instead, if you've problems getting an adequate mass fraction burn at high engine speeds, then fuel design can help. Ditto if you have problems with vaporisation due to, for instance, fuel being heated while looping between the collector and fuel rail.

Variations in ambient conditions are a fact of life. That's why, from memory, the ambient temperature was "set" and communicated to the teams who would then set the thermostats in their fuel trucks accordingly.

cheers,
WilliBetz

Sorry??

it's basic physics, if you evaporate fuel into air, then the air will be cooled by the exaporation of the fuel.

do this right, by injecting the fuel high up in the inlet tract, then the air will be measuably cooled (and thus it's dencity increased).

now, if you start with fuel well below it's evaporation temp, then it's cleary going to take more energy to evaporate it, this the air will be cooled even more, the limit here it that it will also take longer - so there is a limit to how cold the fuel can be.

now, lower intake temps = more power and it's not insignificant...

other benifits of chilling the fuel are things like shorter fill times (in KG's /Min) etc.

Edited by Scuffers on Tuesday 23 October 18:51

[WilliBetz]

Scuffers said:

WilliBetz said:

I've not seen research to suggest that intake air temperature materially influences atomisation, nor can I think of any novel way to influence the intake air temperature. Instead, if you've problems getting an adequate mass fraction burn at high engine speeds, then fuel design can help. Ditto if you have problems with vaporisation due to, for instance, fuel being heated while looping between the collector and fuel rail.

Variations in ambient conditions are a fact of life. That's why, from memory, the ambient temperature was "set" and communicated to the teams who would then set the thermostats in their fuel trucks accordingly.

cheers,
WilliBetz

Sorry??

it's basic physics, if you evaporate fuel into air, then the air will be cooled by the exaporation of the fuel.

do this right, by injecting the fuel high up in the inlet tract, then the air will be measuably cooled (and thus it's dencity increased).

now, if you start with fuel well below it's evaporation temp, then it's cleary going to take more energy to evaporate it, this the air will be cooled even more, the limit here it that it will also take longer - so there is a limit to how cold the fuel can be.

now, lower intake temps = more power and it's not insignificant...

other benifits of chilling the fuel are things like shorter fill times (in KG's /Min) etc.

Edited by Scuffers on Tuesday 23 October 18:51

As far as I can tell, you are asserting that the process of evaporating fuel will cool the surrounding air. As you say, that's well understood physics.

However, the topic under discussion is atomisation of the fuel at the point of injection. In other words, does an injector perform a better job when injecting into cool air or warm air? If you happen to have any experience of this, I would take an academic interest. But I doubt its practical significance, as there's limited scope to alter the intake air temperature.

cheers,
WilliBetz

[carl_w]

Scuffers said:

it's basic physics, if you evaporate fuel into air, then the air will be cooled by the exaporation of the fuel

Yes, evaporative cooling is well understood. However, are you telling me there's a significant difference in the cooling of the inlet charge through evaporative cooling between case (a): fuel injected at 310K, and (b): fuel injected at 296K?

[Scuffers]

carl_w said:

Scuffers said:

it's basic physics, if you evaporate fuel into air, then the air will be cooled by the exaporation of the fuel

Yes, evaporative cooling is well understood. However, are you telling me there's a significant difference in the cooling of the inlet charge through evaporative cooling between case (a): fuel injected at 310K, and (b): fuel injected at 296K?

In simple terms, yes.

this is one of the reasons some engines are built with the top set of injectors actualy firing *away* from the port.

and quoting tems in K is a bit missleading when the evap point of petrol is some 340-350K, at if the fuel is at 310K, it's only some ~30K of it's evap point (in free air which of course an engine intake s not). dopping this 10 degrees is some 20% difference....

[carl_w]

Scuffers said:

and quoting tems in K is a bit missleading when the evap point of petrol is some 340-350K, at if the fuel is at 310K, it's only some ~30K of it's evap point (in free air which of course an engine intake s not). dopping this 10 degrees is some 20% difference....

Surely this is the wrong way round? From what you're saying, hotter fuel is more likely to evaporate (or evaporate more completely) and hence the charge cooling effect would be greater. Surely the cooling effect is just a latent heat issue, which means that it's only the state change that needs to be considered, not any temperature changes that have gone on beforehand in the liquid state?

Edited by carl_w on Wednesday 24th October 19:52

[Scuffers]

No, to get the fuel to evaporate, you need heat from somewhere.....

the cooler the fuel, the more heat required...

[WilliBetz]

I wouldn't worry too much. F1 cars are very good at generating heat.

Care to guess at how hot the fuel gets in the fuel cell?

WilliBetz

[Scuffers]

WilliBetz said:

I wouldn't worry too much. F1 cars are very good at generating heat.

Care to guess at how hot the fuel gets in the fuel cell?

WilliBetz

probably not much, I doubt F1 designers have not considered this....

like the current trend in road cars, they might be running dead-ended fuel rails....

[s.m.h.]

WilliBetz said:

I wouldn't worry too much. F1 cars are very good at generating heat.

Care to guess at how hot the fuel gets in the fuel cell?

WilliBetz

I would guess the chassis would get to around 70 - 80 degrees, the fuel at a similar temp seeing the cell is between the driver and engine. This is just a guess as Ive never measured the temp of fuel coming out of a sportscar...

The vipers used to almost boil the fuel in their tank, the rollover valve had to be working properly else the tank would expand breaking the framework around it. ..