gruntguru wrote:There are two fundamental compressor dimensions that are indicative of its performance. First is the inducer diameter - the size of the entry hole. The optimum massflow of the compressor is roughly proportional to the area of this passage. If turbo B has double the inducer diameter of turbo A, it will have 4 times the area, 4 times the mass flow and suit an engine capable of roughly 4 times the power at a given boost.
The second is the impeller tip diameter. The pressure ratio is proportional to the tip speed squared, so if the compressor speed and tip diameter are known, the pressure ratio can be estimated. In this case we have some idea of PR (3.5) and compressor speed (100,000 rpm). The tip speed required to produce this PR is about 500 m/s which leads us to an impeller tip diameter of 95mm @ 100k rpm.
The outer diameter of the housing is not a good indicator of impeller diameter as there are a range of volute or housing designs - many of them aimed primarily at reducing housing diameter to produce a compact turbocharger. The one in the photo above appears to be a no-compromise design targeting efficiency, and so is not very compact. Just looking at it, I would estimate the impeller is half the diameter of the housing (estimated by Blanchimont as 200mm diameter) which brings us very close to the 95mm mark.
It seems that they a re running lower boost and lower compressor speed... If we assume realistic these datas (http://www.formula1benzing.eu/ungheria2014.html it's in italian and already posted, excuse me), they are a little bit over 3 bar (in other analysis Benzing says something like 3.15 or 3.2 for the Mercedes and williams engines, all the others were lower) and around 90k rpm
Re: Formula One 1.6l V6 turbo engine formula
Posted: 12 Feb 2015, 18:08
by PlatinumZealot
gruntguru wrote:A centrifugal compressor operating at PR = 3.5 will have tip speeds > Mach 1.
Yes, the "reality factor" as I like to call it makes the comparison of inducer diameter to pressure ratio very very general (vague) because there are so many compressors out that can achieve that pressure ratio, at various speeds at various inducer diameters (even much much smaller than 95 mm). The speed of sound also has an effect on the air ( it chokes and mass flow cannot increase). You also can see the bigger turbos cannot reach 100,000 rpms. (I did not find any 95mm inducer turbocharger than can go past 80k rpm on Garrets website) So that could certainly be a limiting factor. We also see that these large garret compressors are in a horsepower range much, much higher than 700 horsepower even though Mercedes assumingly has an inducer (though it is covered in the photo) that could close in size these. It is an interesting topic though.
PlatinumZealot wrote:
....You also can see the bigger turbos cannot reach 100,000 rpms. (I did not find any 95mm inducer turbocharger than can go past 80k rpm on Garrets website) So that could certainly be a limiting factor. http://www.turbobygarrett.com/turbobyga ... er#GT5533R (2)......
Wouldn't that suggest an axial flow compressor as a better solution?
Re: Formula One 1.6l V6 turbo engine formula
Posted: 12 Feb 2015, 22:59
by OO7
Vortex37 wrote:
PlatinumZealot wrote:
....You also can see the bigger turbos cannot reach 100,000 rpms. (I did not find any 95mm inducer turbocharger than can go past 80k rpm on Garrets website) So that could certainly be a limiting factor. http://www.turbobygarrett.com/turbobyga ... er#GT5533R (2)......
Wouldn't that suggest an axial flow compressor as a better solution?
I was just about to ask a question about axial turbos
Can F1 benefit from them and can the compressor be of the axial design and be of benefit in F1?
The above video mentions a loss in peak efficiency and I wonder if this the limitation in racing applications?
Re: Formula One 1.6l V6 turbo engine formula
Posted: 12 Feb 2015, 23:09
by ringo
I already told you all what the boost pressures are. I don't believe in the 3.5 bar.
I've stated 2.5max and this is only at low engine speeds. At 10,500 rpm boost is maybe 1.2 bar. I believe I have a diagram showing boost pressure. 3.5bar is not required and neither is it necessary.
I will stick with 620bhp for the ICE. +/- 25 and that doesn't require the levels of boost that are suggested.
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 00:00
by Abarth
I'm with you on this ringo.
Unless there is something going on with fuels we cannot imagine, with these restrictions.
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 04:56
by gruntguru
PlatinumZealot wrote:
gruntguru wrote:A centrifugal compressor operating at PR = 3.5 will have tip speeds > Mach 1.
Yes, the "reality factor" as I like to call it makes the comparison of inducer diameter to pressure ratio very very general (vague) because there are so many compressors out that can achieve that pressure ratio, at various speeds at various inducer diameters (even much much smaller than 95 mm). The speed of sound also has an effect on the air ( it chokes and mass flow cannot increase). You also can see the bigger turbos cannot reach 100,000 rpms. (I did not find any 95mm inducer turbocharger than can go past 80k rpm on Garrets website) So that could certainly be a limiting factor. We also see that these large garret compressors are in a horsepower range much, much higher than 700 horsepower even though Mercedes assumingly has an inducer (though it is covered in the photo) that could close in size these. It is an interesting topic though. http://www.turbobygarrett.com/turbobyga ... er#GT5533R (2)
95mm is my estimate for tip diameter not inducer diameter, Inducer diameter is indicative of flow, tip diameter (with rpm) is indicative of PR.
Does anyone have an estimate of inducer diameter from photos?
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 04:59
by gruntguru
Vary wrote:
gruntguru wrote:There are two fundamental compressor dimensions that are indicative of its performance. First is the inducer diameter - the size of the entry hole. The optimum massflow of the compressor is roughly proportional to the area of this passage. If turbo B has double the inducer diameter of turbo A, it will have 4 times the area, 4 times the mass flow and suit an engine capable of roughly 4 times the power at a given boost.
The second is the impeller tip diameter. The pressure ratio is proportional to the tip speed squared, so if the compressor speed and tip diameter are known, the pressure ratio can be estimated. In this case we have some idea of PR (3.5) and compressor speed (100,000 rpm). The tip speed required to produce this PR is about 500 m/s which leads us to an impeller tip diameter of 95mm @ 100k rpm.
The outer diameter of the housing is not a good indicator of impeller diameter as there are a range of volute or housing designs - many of them aimed primarily at reducing housing diameter to produce a compact turbocharger. The one in the photo above appears to be a no-compromise design targeting efficiency, and so is not very compact. Just looking at it, I would estimate the impeller is half the diameter of the housing (estimated by Blanchimont as 200mm diameter) which brings us very close to the 95mm mark.
It seems that they a re running lower boost and lower compressor speed... If we assume realistic these datas (http://www.formula1benzing.eu/ungheria2014.html it's in italian and already posted, excuse me), they are a little bit over 3 bar (in other analysis Benzing says something like 3.15 or 3.2 for the Mercedes and williams engines, all the others were lower) and around 90k rpm
3.2 bar and 90k probably still lands us in the 90 - 95mm tip diameter region.
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 05:08
by gruntguru
Abarth wrote:How do you come to conclude that PR=3.5?
Me thinks in that case the engines would run extremely lean.
Correct. Fuel rate is fixed. Therefore best power = best BSFC.
"SI engines with intake manifold injection achieve the lowest fuel consumption at constant engine output dependent on the engine at 20-50% air surplus (lambda = 1.2 - 1.5)" Bosch Automotive Handbook, 8th Edition Page 559.
The F1 engines are DFI not PFI which allows still leaner operation with stratified charge. High scavenge ratios (benefit is cooling during valve overlap) further increase the air consumption without leaning the actual combustion process.
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 08:09
by wuzak
Vortex37 wrote:
PlatinumZealot wrote:
....You also can see the bigger turbos cannot reach 100,000 rpms. (I did not find any 95mm inducer turbocharger than can go past 80k rpm on Garrets website) So that could certainly be a limiting factor. http://www.turbobygarrett.com/turbobyga ... er#GT5533R (2)......
Wouldn't that suggest an axial flow compressor as a better solution?
Axial compressors have small pressure ratios per stage (<1.5), so they need to be multi stage to gain benefit. The F1 rules, however, stipulate only one stage for the compressor and one stage for the turbine.
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 10:30
by Abarth
gruntguru wrote:
Abarth wrote:How do you come to conclude that PR=3.5?
Me thinks in that case the engines would run extremely lean.
Correct. Fuel rate is fixed. Therefore best power = best BSFC.
"SI engines with intake manifold injection achieve the lowest fuel consumption at constant engine output dependent on the engine at 20-50% air surplus (lambda = 1.2 - 1.5)" Bosch Automotive Handbook, 8th Edition Page 559.
The F1 engines are DFI not PFI which allows still leaner operation with stratified charge. High scavenge ratios (benefit is cooling during valve overlap) further increase the air consumption without leaning the actual combustion process.
But PR=3.5 would mean 4.5 bar absolute pressure, or around 4.7kg /m3 air at 60 deg C.
Lambda then is >2....
I don't believe they are running more lean then 1.2...1.3
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 10:49
by wuzak
Abarth wrote:
gruntguru wrote:
Abarth wrote:How do you come to conclude that PR=3.5?
Me thinks in that case the engines would run extremely lean.
Correct. Fuel rate is fixed. Therefore best power = best BSFC.
"SI engines with intake manifold injection achieve the lowest fuel consumption at constant engine output dependent on the engine at 20-50% air surplus (lambda = 1.2 - 1.5)" Bosch Automotive Handbook, 8th Edition Page 559.
The F1 engines are DFI not PFI which allows still leaner operation with stratified charge. High scavenge ratios (benefit is cooling during valve overlap) further increase the air consumption without leaning the actual combustion process.
But PR=3.5 would mean 4.5 bar absolute pressure, or around 4.7kg /m3 air at 60 deg C.
Lambda then is >2....
I don't believe they are running more lean then 1.2...1.3
PR of 3.5 means they are running 3.5bar absolute or 2.5bar boost (gauge pressure).
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 11:19
by Abarth
wuzak wrote:PR of 3.5 means they are running 3.5bar absolute or 2.5bar boost (gauge pressure).
Isn't PR pressure ratio?
Re: Formula One 1.6l V6 turbo engine formula
Posted: 13 Feb 2015, 12:47
by wuzak
Abarth wrote:
wuzak wrote:PR of 3.5 means they are running 3.5bar absolute or 2.5bar boost (gauge pressure).
Isn't PR pressure ratio?
Yes.
PR = (output pressure)/(input pressure)
Input pressure is 1bar absolute (near enough in standard atmospheric conditions), so to get a PR of 3.5 the output pressure must be 3.5bar absolute.
You are confusing it with boost, which is pressure over and above atmospheric pressure (ie gauge pressure). For most venues in F1 that is ~1bar absolute.
Not sure if in F1 boost is strictly gauge pressure or pressure above normal sea level air pressure.
In WW2 aircraft terms bppst was the latter.
For example, most late model Merlins were rated for +18psi boost.
At sea level that meant that the output pressure was 14.7psi + 18psi = 32.7psi. The pressure ratio of the compressor was, therefore 32.7/14.7 = 2.22.
At ~18,000ft the outside air pressure was half of sea level pressure, 7.35psi. Some versions of Merlins would still be capable of +18psi boost at that altitude (mainly those with 2 stage compressors).
The output pressure remains at 14.7psi + 18psi = 32.7psi. But the input pressure is 7.35psi so the pressure ratio of the compressor is 32.7/7.35 = 4.44.
