New 2015 fuel flow Directive

[DaveW]

Fuel pulsation damper = fuel accumulator.

If I remember correctly, RB were disqualified last year after the Australian GP for allowing the instantaneous fuel flow meter reading to exceed the regulated limit. They then had to reduce the actual fuel flow (by their calculations) to remain within the peak flow meter reading. The difference was "lost" energy they had no way of accessing.

I think G-G's observations were well made, and probably correct.

[Vortex Motio]

In this Omnicorse article, http://www.omnicorse.it/magazine/50523/ ... i-100-kg-h
the author mentions engine speed near 13,500 rpm.

Would 13,500 rpm be a sign of higher fuel flow?

Is this true, that some are now running close to 13,500 rpm?

[gandharva]

http://www.bosch-motorsport.de/de/de/pr ... 197557.php
http://www.bosch-motorsport.de/media/ca ... 971pdf.pdf

[dans79]

http://www.bosch-motorsport.de/media/ca ... 971pdf.pdf

This rules out any kind of fuel line trickery, as the supply pressure is only 4 - 7 bar.


Does anyone have any idea what the volume of the bellows is?

[Richard]

http://www.bosch-motorsport.de/media/ca ... 971pdf.pdf

This rules out any kind of fuel line trickery, as the supply pressure is only 4 - 7 bar.


Does anyone have any idea what the volume of the bellows is?

I'd expect F1 to use a bespoke spec with the fuel pressure they want, not just what happens to be available.

[dans79]

http://www.bosch-motorsport.de/media/ca ... 971pdf.pdf

This rules out any kind of fuel line trickery, as the supply pressure is only 4 - 7 bar.


Does anyone have any idea what the volume of the bellows is?

I'd expect F1 to use a bespoke spec with the fuel pressure they want, not just what happens to be available.

Most likely, but to me specifying a bellows larger than standard, would be pretty sketchy!

[Juzh]

Is this true, that some are now running close to 13,500 rpm?

No. I don't know where omnicorse got their data, but I do know they're incorrect.

[gruntguru]

One thing confirmed by the Omnicourse article is heating of the fuel. The wording used is "fuel used . . . to cool the upper part of the engine.". This is clearly an ideal spot to form a temporary vapor bubble and allow this region to be depleted of fuel at some rate - in addition to the 100 kg/hr coming from the flow meter.

[dans79]

One thing confirmed by the Omnicourse article is heating of the fuel.

Omnicourse is not a reliable source!

[itix]

I wonder how accurate those "fuel used" charts we get on the TV are?

I remember last year mercedes consistently used a tiny percentage less fuel than most teams. This would not make sense if they were cheating the fuel flow with some form of accumulator or flexing fuel lines as some suggest. The idea would be that when the rest of the field (non merc PU's) slowed down and did not use the full 27.8 ml/s flow, the merc PU's would continue to charge up their accumulator but staying within the . This is all well, but you'd need to empty the accumulator on the next straight to increase the fuel flow to the injectors and that's where it starts to get difficult to hide. Even if you have a damper that's working like an accumulator it would need emptying by some mechanical means.

Temperature regulation would not work as it is massflow that is measured rather than volumetric flow, unless heated it up massively afterwards to increase the fuel flow, but that would require a very long fuel line, possibly in some form of coil, with a heating device. The expansion coefficient of fuel is not that big so this would have to be a big and conspicuous device that we are talking about. I don't really believe in that theory.

EDIT: to add to the above you'd also need to cool down the fuel between the straights to "accumulate" fuel in a very long fuel line, so the device would not only need to heat up fuel but also need to cool it down in the corners... naaaaah.

I also do not believe in the cavitation theory as I agree with what R_gowin wrote... cavitation in a fuel system is not something you want to have and you don't change the massflow in the injectors and into the cylinders via cavitation. Also you can't control cavitation so creating a smooth power delivery on a straight of maybe 15 seconds with one big cavitation bubble is impossible, as it would just cause a massive vacuum in the fuel lines.

And bleeding in air into the fuel system... first of all that would require a secondary booster pump and you'd need some form of de-airation valve to let the air out again or the engine would magically stop after every straight halfway through the corner. Second, you'd also risk spilling precious fuel through the deaeration valve. Naaah too far fetched.

Does anyone here know hat happens to the signal from the fuel flow sensor before it reaches the FIA? If I wanted to cheat the sensor, that's where I would do it. Small inconspicuous signal converter somewhere and voila, less fuel used!

[gruntguru]

itix.
If you have a region of warmer fuel, all you need to do is reduce the pressure in the fuel to the vapor pressure and a vapor bubble will begin to form. You could be taking liquid fuel displaced by the bubble at a rate of say 5 kg/hr. Add in the 100 kg/hr from the flow meter and you have 105 kg/hr available to the engine.

When you are done consuming "extra" fuel (eg your engine now needs only 20 kg/hr through a sweeping corner), you simply increase the fuel pressure again and the vapor bubble will condense. During this process the flow meter might be reading 24 kg/hr. 20kg/hr for the engine and 4 to replace the vapor bubble. Simple.

[DaveW]

Temperature regulation would not work as it is massflow that is measured rather than volumetric flow

I have a sight issue with that statement. According to Gill the device "uses ultrasonic technology to deliver a solution that measures bi-directional fuel flow to a very high degree of accuracy and which has the fastest step response rate on the market." see here.

Elsewhere they state "We are experts in the development of state-of-the-art algorithms for highly accurate time-of-flight measurement and transducer designs for liquid and gas flow." I guess that means velocity, rather than mass.

[itix]

I have a sight issue with that statement. According to Gill the device "uses ultrasonic technology to deliver a solution that measures bi-directional fuel flow to a very high degree of accuracy and which has the fastest step response rate on the market." see here.

Elsewhere they state "We are experts in the development of state-of-the-art algorithms for highly accurate time-of-flight measurement and transducer designs for liquid and gas flow." I guess that means velocity, rather than mass.

FIA are not complete idiots. Since the regulation is massflow centred I am sure that the sensor is tested with various liquids of various densities and that they can translate the signal (4-20 mA or whatever it gives) to accurate massflow readings.

Since density varies with temperature they'd be beyond stupid to introduce a volumetric sensor as a control point.

I sometimes use an ultrasonic device to do mass flow testing of pipes in my work. You feed it info like pipe dimension and thickness and the liquid inside the pipe and out comes massflow (you can measure a million things with it, it even has a measument for beer hahahaha ). I assume that gills sensor has all the variables they need to figure out the actual massflow.

itix.
If you have a region of warmer fuel, all you need to do is reduce the pressure in the fuel to the vapor pressure and a vapor bubble will begin to form. You could be taking liquid fuel displaced by the bubble at a rate of say 5 kg/hr. Add in the 100 kg/hr from the flow meter and you have 105 kg/hr available to the engine.

When you are done consuming "extra" fuel (eg your engine now needs only 20 kg/hr through a sweeping corner), you simply increase the fuel pressure again and the vapor bubble will condense. During this process the flow meter might be reading 24 kg/hr. 20kg/hr for the engine and 4 to replace the vapor bubble. Simple.

If you can get that that to function in a stable and controlled way and show me a controllable increase of mass flow at the end point of a system I'll be highly impressed.

And even if you did manage that, the injectors like a bit of pressure to atomize the fuel properly so that it is distributed in an even way in the cylinder and therefor burn more stocheometrically (I probably spelled that word wrong). It is not so important with throttle body or intake injection because the fuel has more time to vaporize than in a direct injected engine. If you had so low fuel pressure that you'd vaporize parts of it you'd also just put a blurb of fuel on top of the piston that wouldn't burn right and it'd combust in the exhaust instead (and you'd have wonderful rally anti-lag sounds *dreaming*).

[DaveW]

FIA are not complete idiots. Since the regulation is massflow centred I am sure that the sensor is tested with various liquids of various densities and that they can translate the signal (4-20 mA or whatever it gives) to accurate massflow readings.....Since density varies with temperature they'd be beyond stupid to introduce a volumetric sensor as a control point.

I am sure you are right.

But I still have an issue with your original statement, because the measurement is actually an estimate of flow velocity, and corrected for fuel type, pressure & temperature. I guess RBR thought they had a better measure of mass flow and chose to ignore the FIA sensor (they had the right to do that, if the sensor was in error). The FIA proved that were not complete idiots by declaring their sensor was the standard, and everybody else was wrong. Incidentally, I believe that output of the device was digital, not analogue.

[Abarth]

[...]If you can get that that to function in a stable and controlled way and show me a controllable increase of mass flow at the end point of a system I'll be highly impressed.

And even if you did manage that, the injectors like a bit of pressure to atomize the fuel properly so that it is distributed in an even way in the cylinder and therefor burn more stocheometrically (I probably spelled that word wrong). It is not so important with throttle body or intake injection because the fuel has more time to vaporize than in a direct injected engine. If you had so low fuel pressure that you'd vaporize parts of it you'd also just put a blurb of fuel on top of the piston that wouldn't burn right and it'd combust in the exhaust instead (and you'd have wonderful rally anti-lag sounds *dreaming*).

I think there is a misunderstanding here.

There is no possible "cheating" wrt the fuel mass flow over a certain prolonged time, let's say over one lap (indeed, it would be even a shorter time...) with the idea Gruntguru proposed.

But, it is well possible to use the elasticity of the fuel transport system and/or the "elasticity of fuel in fluid vs. gaseous phase.

And, it has nothing to do with the rail pressure, i.e. the pressure the injectors are seeing, which is between 250 and max. 500 bar as far as info has been released.

All this must happen before the High Pressure Pump (HPP) which produces thede 250-500 bar and after a feeding pump. This pump could feed constantly 100kg/h, and be pressure limited to xx bar.

- In case of higher demand >100kg/h of the injectors/HPP, it would feed in the volume limited mode. The pressure in the fuel transport system falls, and elasticity/bubbles are produced. Mass flow sensor reads 100kg/h.

- When a certain low limit of the feeding pressure is reached, the engine has to reduce mass flow to 100kg/h.
- As soon as there is less than 100 kg/h used (braking, cornering), the feeding pump, still delivering 100 kg/h can repressure the system, until its pressure limit is reached, compressing the fuel bubble to liquid and/or expanding the fuel lines or whatever.

This can be made with very few electronic controls, one of the most important things being the fuel pump feeding constant volume independently from the pressure, but limiting this flow when a certain pressure level is reached.