Possible limits, tricks and cheats of the flow sensors?

[Tommy Cookers]

....mass certification is allowed to assume 'g' = 9.815 m/sec/sec - but 'g' significantly varies from venue to venue....

Mass is not dependent on 'g', weight is.

yes to the correction (I was confused into misplaced reverence thinking of certified calibration weights as calibration masses)
officialdom is upset when you submit for official checking your weights with Newton values you stamped on them
it is of course weighing that officialdom allows to assume 'g' is 9.815 m/sec/sec and to disregard the true local 'g' value
yes the statuary standards are for trading purposes and so rather sloppy
but eg the UK Geological Survey will provide a Silverstone 'g' estimate certain to c. 3 ppm or do a survey for c. 1 ppm

otherwise a balance that reads 100 kg at FIA HQ won't properly weigh 100 kg of fuel at eg Mexico City or Kyalami or anywhere
and 100 kg of fuel is a different amount (not 100 kg mass) of fuel at each and every venue
as the FIA officials presumably don't recalibrate their balance (against a 100 kg reference mass) at each venue

and re the previous post
does Wolff mean combustion efficiency or thermal efficiency ? (aka indicated thermal efficiency)
eg if Ferrari improved its combustion efficiency by 5.4% the H recovery would fall by about 18 kW
combustion efficiency is about 95% always - and won't be improved eg by leaner running
but the engine that can run leanest without CE falling below 95% will win as TE will be greater due to lower heat loss

[henry]

otherwise a balance that reads 100 kg at FIA HQ won't properly weigh 100 kg of fuel at eg Mexico City or Kyalami or anywhere
and 100 kg of fuel is a different amount (not 100 kg mass) of fuel at each and every venue
as the FIA officials presumably don't recalibrate their balance (against a 100 kg reference mass) at each venue

They don’t weigh the fuel. They integrate the fuel sensor readings. So it’s mass everywhere.

[gruntguru]

I assume Tommy's reference to the "FIA's balance" is a set of scales or similar used to weigh components (or fuel?).

I disagree with Tommy's presumption that the balance is not calibrated to the local value of g for each venue. To not do so would be a very amateurish error.

[j.yank]

Remember though that teams have to provide a fuel sample to FIA before use and also have sufficient in the 'tank' to be tested at the end of the race.

FIA checks what is described in the technical rules. They cannot check for something that is not parametrized there.

[subcritical71]

Remember though that teams have to provide a fuel sample to FIA before use and also have sufficient in the 'tank' to be tested at the end of the race.

FIA checks what is described in the technical rules. They cannot check for something that is not parametrized there.

The after race fuel sample is very routine and covered in the sporting regulations with this catch all;

25.5 The scrutineers may :
a) Check the eligibility of a car or of a competitor at any time during an Event.
b) Require a car to be dismantled by the competitor to make sure that the conditions of eligibility or conformity are fully satisfied.
c) Require a competitor to pay the reasonable expenses which exercise of the powers mentioned in this Article may entail.
d) Require a competitor to supply them with such parts or samples as they may deem necessary.

There are also TDs which must be complied with.

[j.yank]

The after race fuel sample is very routine and covered in the sporting regulations with this catch all;

Exactly, the fuel check is routine but only for the chemical composition, temperature and mass. The bulk modulus is not in this list. Again, I am not sure is it possible to change it (the B for gasoline is 1.3) but if you find a way to lower its value you will be able to increase the fuel density.

[subcritical71]

The after race fuel sample is very routine and covered in the sporting regulations with this catch all;

Exactly, the fuel check is routine but only for the chemical composition, temperature and mass. The bulk modulus is not in this list. Again, I am not sure is it possible to change it (the B for gasoline is 1.3) but if you find a way to lower its value you will be able to increase the fuel density.

I don’t think it needs to be. How much do you think bulk modulus can be changed in the fuel while staying within all the parameters specified in the regulations, and then from that how much it would change the fuel flow reading?

Density needs to be within spec of the approved fuel sample (+/- 0.25%).

[j.yank]

The after race fuel sample is very routine and covered in the sporting regulations with this catch all;

Exactly, the fuel check is routine but only for the chemical composition, temperature and mass. The bulk modulus is not in this list. Again, I am not sure is it possible to change it (the B for gasoline is 1.3) but if you find a way to lower its value you will be able to increase the fuel density.

I don’t think it needs to be. How much do you think bulk modulus can be changed in the fuel while staying within all the parameters specified in the regulations, and then from that how much it would change the fuel flow reading?

Density needs to be within spec of the approved fuel sample (+/- 0.25%).

(+/- 0.25%) density gives +/- 4.24 HP per 100 kg/h gasoline flow. However, this density is measured outside of the fuel tank and it is supposed to be the same at 500 bar pressure in the fuel pump. Let suppose that we lower the bulk modulus and make a fuel tank with slightly less volume that should accommodate the legal fuel mass. In this case the density of the fuel would be above the approved 0.25 density delta but when pass through the fuel sensor it will give the expected regulated speed of sound. In this way, you can get power boost for a lap or two but cannot sustain it during the race.

[henry]

Exactly, the fuel check is routine but only for the chemical composition, temperature and mass. The bulk modulus is not in this list. Again, I am not sure is it possible to change it (the B for gasoline is 1.3) but if you find a way to lower its value you will be able to increase the fuel density.

I don’t think it needs to be. How much do you think bulk modulus can be changed in the fuel while staying within all the parameters specified in the regulations, and then from that how much it would change the fuel flow reading?

Density needs to be within spec of the approved fuel sample (+/- 0.25%).

(+/- 0.25%) density gives +/- 4.24 HP per 100 kg/h gasoline flow. However, this density is measured outside of the fuel tank and it is supposed to be the same at 500 bar pressure in the fuel pump. Let suppose that we lower the bulk modulus and make a fuel tank with slightly less volume that should accommodate the legal fuel mass. In this case the density of the fuel would be above the approved 0.25 density delta but when pass through the fuel sensor it will give the expected regulated speed of sound. In this way, you can get power boost for a lap or two but cannot sustain it during the race.

The fuel is not at 500bar when it passes through the sensor. The fuel is pumped out of the fuel cell by a low pressure pump and then a high pressure pump prepares it for the injectors.

[godlameroso]

Fuel octane rating and temperature affects gasoline viscosity, viscosity of fuel affects fuel pressure. Higher octane tends to have higher viscosity this is more obvious with diesel fuels. However, the same holds true for gasoline but at a different rate. Gasoline lacks something's and has some other things that diesel doesn't have increasing the octane rating to a certain point requires a fuel heater to have proper viscosity in fuel. However nothing like that is being used in F1 to my knowledge. Perhaps being pushed in that direction.

[gruntguru]

I found in the technical regulations, that the pressure, temperature, the mas and the chemical composition of the fuel are described in detailed manner, but there is not any mention of bulk modulus of the fuel that could influence the density, and in this way the flow rate for a short period. If the flow sensors are strictly calibrated to the generic petrol bulk module and they work based on defined speed of sound, it makes possible through decrease of the stiffness of the fuel to increase its density keeping the sound speed the same but allowing increased mass flow for a given time. I am not sure that this is possible at all (to decrease the stiffness) but this seems as a possible way to circumvent the temperature as a way of increasing the density. Of course, it would be illegal but until they catch the trick (if it actually exists) they could gain significant performance gain as we can see on the track.

Changing the modulus of the fuel will not change the density. Obviously a low modulus would make the density more sensitive to changes in pressure but the whole "accumulation of fuel by changing pressure" trick has been explored by the teams and rules were added to close that loophole.

[63l8qrrfy6]

Fuel octane rating and temperature affects gasoline viscosity, viscosity of fuel affects fuel pressure. Higher octane tends to have higher viscosity this is more obvious with diesel fuels. However, the same holds true for gasoline but at a different rate. Gasoline lacks something's and has some other things that diesel doesn't have increasing the octane rating to a certain point requires a fuel heater to have proper viscosity in fuel. However nothing like that is being used in F1 to my knowledge. Perhaps being pushed in that direction.

[j.yank]

Changing the modulus of the fuel will not change the density.

In a fluid, the bulk modulus K and the density ρ determine the speed of sound c (pressure waves), according to the Newton-Laplace formula
https://en.wikipedia.org/wiki/Bulk_modulus

Obviously, if you wish to keep the speed of the sound in given medium constant (as reqiired by the F1 regulations regarding the flow sensor), bulk modulud and density are interlinked.

[subcritical71]

Changing the modulus of the fuel will not change the density.

In a fluid, the bulk modulus K and the density ρ determine the speed of sound c (pressure waves), according to the Newton-Laplace formula
https://en.wikipedia.org/wiki/Bulk_modulus

Obviously, if you wish to keep the speed of the sound in given medium constant (as reqiired by the F1 regulations regarding the flow sensor), bulk modulus and density are interlinked.

Looking at the FIA homologated sensor data at https://gillsc.com/products/flow-senso ... w-meter-2/, it seems the sensor can measure speed of sound of the fuel and is not dependent on a stored value (or lookup table). I also searched and found several papers which show that speed of sound can be determined using a similar configuration as the gill sensor uses.

[gruntguru]

Changing the modulus of the fuel will not change the density.

In a fluid, the bulk modulus K and the density ρ determine the speed of sound c (pressure waves), according to the Newton-Laplace formula
https://en.wikipedia.org/wiki/Bulk_modulus

Obviously, if you wish to keep the speed of the sound in given medium constant (as reqiired by the F1 regulations regarding the flow sensor), bulk modulus and density are interlinked.

AFAIK the flow sensor is not sensitive to the speed of sound in fact it calculates the speed of sound of the medium.