dragosmp wrote:It seems to me there could be a more basic way of limiting mass flow by setting a restriction on the:
*max diameter tubing
*tank pressure
*fuel temperature
With the fixed tubing, primary pressure and fuel viscosity characteristics (dependent on temperature) one can compute pretty accurately the amount of fuel that could pass. I think temperature and pressure sensors are based on quite mature technology, as opposed to this sensor.
afaiu is is "just" an ultrasonic flow sensor, it measures the speed of the flow though a defined section of tube that is a quite mature technology.
I guess they could skip the sensor and instead use a flow restrictor but that would change one thing; the rpm dependent flow restriction, which i expect would mean the teams would run at much lower rpms and that would be bad for those who think the new engine already sound boring
I'm puzzled why so many on here - and the teams themselves - seem to be assuming that the measurements from the fuel injection system will be more accurate than the fuel flow meter. I don't know the detail of the F1 fuel injection control systems, but I am assuming that they aren't that far removed from road car systems where there is no direct measurement of fuel flow, but injected fuel volume/mass is estimated as a function of injector energisation time, and fuel temperature/pressure.
To put some numbers against it all, I did a few rough calculations. The rules state that the 100kg/h limit applies above 10500rev/min, up to the rev limit at 15000rev/min. For a 6-cylinder, 4-stroke engine this gives 525inj/s and 750inj/sec respectively, and corresponding fuel mass per power stroke as 52.9mg at 10500rev/min down to 37mg at 15000rev/min. Assuming that the fuel is injected over a 20° crank rotation (this may even be too long...), then this gives injector energisation times of the order of 317 to 222 microseconds. So the 1% error that the regulations permit in the FFM equates to around 2-3 microseconds of energisation time at the injector.
Now, I don't know about you, but I very much doubt that the injectors can be controlled with that degree of precision - I'd expect shot-to-shot variability would probably be at least double this - plus injectors tend to drift in use due to wear of the nozzle and the moving parts and are highly susceptible to noise factors such as clamping load, vibration and temperature. In a precisely controlled environment - such as an engine dynamometer - then variability would be reduced, but in an F1 car, running in a hot, high G-force environment?
So for me, I'd rather believe the FFM...
...aside from anything else though, how arrogant of Red Bull to assume that they were above the rules!
Paul C wrote:I'm puzzled why so many on here - and the teams themselves - seem to be assuming that the measurements from the fuel injection system will be more accurate than the fuel flow meter.
I don't know what systems are used to control the power plant of an F1 vehicle, but a rather imagine that a fairly sophisticated filtering methodology would be required (e.g. Kalman). One of the inputs would be fuel velocity, and one of the outputs would be mass flow rate. The result would not be perfect, but it would probably be more representative than a single transducer output.
Paul C wrote:...aside from anything else though, how arrogant of Red Bull to assume that they were above the rules!
Agreed... But they are racers. I don't think they will succeed in reversing the decision, but they may change the concept that the calibration of a single transducer can decide the results of a race.
I have a question to the more knowledgeable.
I haven't seen and I don't know the internal design of an F1 car fuel system. But I assume they should have some kind of fuel recirculation, like on ordinary cars. Excess fuel from the feeder pump to the rail is returned back and one of the reasons is to prevent fuel getting too hot.
On the other hand the rules postulate that the fuel flow sensor is in the fuel tank. Up to now I thought the fuel sensor is somewhere after the high pressure pump.
If there is a return then how do they account for it?
Is the HP pump in the fuel tank too?
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I'm slightly puzzled why from all possibilities to regulate the power of the combustion engine, they took this one.
In a post here somewhere else it was calculated, with 100kg/h flow means a limit of +/- 600hp. The measurement of flow of a certain mass of liquid just sounds difficult (but I could be very wrong). If the sensor does measure volume, it would be possible to cool the fuel and get above 100kg/h.
The only reason I can think of that they didn't go for the normal solution of a air restrictor, is that they want to push the development of extra lean burning (what makes the engine very very hot) and let the turbo, with electric assistance "push" the crankshaft.
Jolle wrote:In a post here somewhere else it was calculated, with 100kg/h flow means a limit of +/- 600hp. The measurement of flow of a certain mass of liquid just sounds difficult (but I could be very wrong). If the sensor does measure volume, it would be possible to cool the fuel and get above 100kg/h.
The ultrasonic sensor measures the fuel velocity, which can then be converted into a volume flow rate - and you're quite right, cooling the fuel would increase the mass flow rate for a constant volume flow rate. However, the FFM also incorporates 2 temperature sensors, which are then be used to calculate fuel density and therefore convert the volume flow rate to mass flow rate. So, to answer your question, cooling the fuel doesn't help to circumvent the rule. Hope this helps!
Jolle wrote:In a post here somewhere else it was calculated, with 100kg/h flow means a limit of +/- 600hp. The measurement of flow of a certain mass of liquid just sounds difficult (but I could be very wrong). If the sensor does measure volume, it would be possible to cool the fuel and get above 100kg/h.
The ultrasonic sensor measures the fuel velocity, which can then be converted into a volume flow rate - and you're quite right, cooling the fuel would increase the mass flow rate for a constant volume flow rate. However, the FFM also incorporates 2 temperature sensors, which are then be used to calculate fuel density and therefore convert the volume flow rate to mass flow rate. So, to answer your question, cooling the fuel doesn't help to circumvent the rule. Hope this helps!
I'm just baffled that from all the solutions they took the worst one. Measure vs restrictor, mass vs volume and fuel vs air.
a simple air restrictor (just before the turbo) would have (or will be) a very simple, bulletproof and very cheap solution to keep the engine power limited.
Jolle wrote:I'm slightly puzzled why from all possibilities to regulate the power of the combustion engine, they took this one.
...
The only reason I can think of that they didn't go for the normal solution of a air restrictor, is that they want to push the development of extra lean burning (what makes the engine very very hot) and let the turbo, with electric assistance "push" the crankshaft.
The very laudable goal (IMO) in restricting fuel is to have some of the hundreds of millions of dollars being spent on F1 and the productive work of some of the best engineers in the world be used for something more useful than just making cars have shorter lap times.
As an engineer (not in F1), I would much prefer having my work have some more general positive impact. Designing an engine that uses less air does not do that. Getting more work out of a gram of fuel does.
They could have just gone with a prescribed restriction/venturi in the fuel lines and fuel pressure restriction (which is far easy to measure accurately. Even if it wasn't flowing exactly 100kg/h at least all the teams would have the same...
Paul C wrote:I'm puzzled why so many on here - and the teams themselves - seem to be assuming that the measurements from the fuel injection system will be more accurate than the fuel flow meter. I don't know the detail of the F1 fuel injection control systems, but I am assuming that they aren't that far removed from road car systems where there is no direct measurement of fuel flow, but injected fuel volume/mass is estimated as a function of injector energisation time, and fuel temperature/pressure.
To put some numbers against it all, I did a few rough calculations. The rules state that the 100kg/h limit applies above 10500rev/min, up to the rev limit at 15000rev/min. For a 6-cylinder, 4-stroke engine this gives 525inj/s and 750inj/sec respectively, and corresponding fuel mass per power stroke as 52.9mg at 10500rev/min down to 37mg at 15000rev/min. Assuming that the fuel is injected over a 20° crank rotation (this may even be too long...), then this gives injector energisation times of the order of 317 to 222 microseconds. So the 1% error that the regulations permit in the FFM equates to around 2-3 microseconds of energisation time at the injector.
Now, I don't know about you, but I very much doubt that the injectors can be controlled with that degree of precision - I'd expect shot-to-shot variability would probably be at least double this - plus injectors tend to drift in use due to wear of the nozzle and the moving parts and are highly susceptible to noise factors such as clamping load, vibration and temperature. In a precisely controlled environment - such as an engine dynamometer - then variability would be reduced, but in an F1 car, running in a hot, high G-force environment?
So for me, I'd rather believe the FFM...
...aside from anything else though, how arrogant of Red Bull to assume that they were above the rules!
Yes. Anyone who says they "know" the true value of a mass flow to a high precision by measuring it indirectly has never tried to repeat the measurements themselves. RB upper management may think they know, and they don't. I suspect RB engineers with more sensor experience are a bit red faced at their team's press releases.
Sorry to repeat myself from another thread, but there are consistent questions to the effect of: Why does the FIA use the FFM instead of a simpler and more robust alternative such as a fuel restrictor or weighing the fuel at the beginning of the race?
The answer is that the FIA (and most of the F1 community) wants to maintain the traditional ramp-up step-down sound of the engine revving between gearshifts as the car accelerates.
To achieve this the FIA specifically needs to restrict low-rpm fuel flow more than high-rpm fuel flow. This forces low-rpm power to be lower than high-rpm power. In turn that forces gear changes to optimize the car's acceleration.
I think multiple gears are the big lie of modern high performance driving. I think any general type of racecar would be cheaper and faster with broad-powerband engines and direct-drive final drives. However, current racecar regulations consistently force engines with relatively narrow powerbands in combination with multi-speed transmissions.
bill shoe wrote:Sorry to repeat myself from another thread, but there are consistent questions to the effect of: Why does the FIA use the FFM instead of a simpler and more robust alternative such as a fuel restrictor or weighing the fuel at the beginning of the race?
The answer is that the FIA (and most of the F1 community) wants to maintain the traditional ramp-up step-down sound of the engine revving between gearshifts as the car accelerates.
...
So that's why 2014 F1 has a fuel flow meter.
That sounds plausible to me; it is consistent with the FIA ban on any kind of CVT.
It would be interesting to see what performance a Toyota hybrid synergy drive style CVT would have in F1.
Jef Patat wrote:It must have been mentioned a thousand times by now: it's about total fuel consumption over the total race distance AND about peak consumption which cannot go over 100kg/h, even not for a fraction of a split second. The second one cannot be checked by looking at the available/remaining fuel.
Yes but if you integrate the FFM sensor and get a total fuel use which is significantly more than the amount of fuel which went in the car in the first place, then it follows that it is not holding its +0/-1% accuracy spec on flow rate.
If Red Bull show that the sensor implies that the motor took more fuel then they can physically fit in the tank, they've got a pretty good case.
I agree to your point, I think it's valid and 'fair' to show that the sensor is faulty. The thing is RB got disqualified because of not obeying, not because the sensor might be erroneous.
Jef Patat wrote:Sorry, I only meant to respond to the second part of your post.
Mass rate can be measured directly but AFAIK it always involves some kind of interference with the flow. This might be a serious disadvantage in some cases but sometimes it might be a better way of measureing. Ultrasonic has the advantage of not interfering with the flow. Even if mass rate is required, in a lot of cases volume flow is used. If you know the density of the fluid a conversion is straight forward. The sensor is also temperature compensated (ultrasonic wave speed depends on temperature) and an ultrasonic sensor compensates for flow friction (speed of flow is higher in the center than it is where the fluid touches the tube). I don't think the fuels of the several teams will diverse that much in density to be able to cause a problem there neither. IMHO flow rate to mass rate is simple maths in this case.
Mass flow can be measured directly without impeding flow by Coriolis force flow meters. But G forces would probably compromise results. It would probably be simpler to limit fuel pressure through a standard orifice.
Coriolis flow meters cause a substantial pressure drop, which is in my 'not native english' interference with the flow. I don't know if the flow is big enough to use a bypass system. The biggest problem in a race car with coriolis meters probably will be the vibrations the car introduces in the measurement. Don't take my answer as an expert answer, it has been quite a while since I worked with a coriolis sensor, and it certainly was not in a race car
Paul C wrote:I'm puzzled why so many on here - and the teams themselves - seem to be assuming that the measurements from the fuel injection system will be more accurate than the fuel flow meter. I don't know the detail of the F1 fuel injection control systems, but I am assuming that they aren't that far removed from road car systems where there is no direct measurement of fuel flow, but injected fuel volume/mass is estimated as a function of injector energisation time, and fuel temperature/pressure.
To put some numbers against it all, I did a few rough calculations. The rules state that the 100kg/h limit applies above 10500rev/min, up to the rev limit at 15000rev/min. For a 6-cylinder, 4-stroke engine this gives 525inj/s and 750inj/sec respectively, and corresponding fuel mass per power stroke as 52.9mg at 10500rev/min down to 37mg at 15000rev/min. Assuming that the fuel is injected over a 20° crank rotation (this may even be too long...), then this gives injector energisation times of the order of 317 to 222 microseconds. So the 1% error that the regulations permit in the FFM equates to around 2-3 microseconds of energisation time at the injector.
Now, I don't know about you, but I very much doubt that the injectors can be controlled with that degree of precision - I'd expect shot-to-shot variability would probably be at least double this - plus injectors tend to drift in use due to wear of the nozzle and the moving parts and are highly susceptible to noise factors such as clamping load, vibration and temperature. In a precisely controlled environment - such as an engine dynamometer - then variability would be reduced, but in an F1 car, running in a hot, high G-force environment?
So for me, I'd rather believe the FFM...
...aside from anything else though, how arrogant of Red Bull to assume that they were above the rules!
Yes. Anyone who says they "know" the true value of a mass flow to a high precision by measuring it indirectly has never tried to repeat the measurements themselves. RB upper management may think they know, and they don't. I suspect RB engineers with more sensor experience are a bit red faced at their team's press releases.
As I've mentioned before I'm quite sure it can be done. I must admit I cannot give the technical details of how it works, but I can assure you that I've worked with the results. On off road vehicles fule consumption is measured in liters/hour. I used to be one of the developpers of controllers on (among others) this machine. Part of the datamining to the driver consisted of fuel consumption. I know for sure that from the measurements I've done the integration error was less than 0.5liters per tank (over a 1000 liters). If I remember well that was done without a fuel flow meter. Keep in mind this is not an F1 car and technology is a lot cheaper. I'm convinced that with a flow meter that kind of accuracy would not have been reached.
