N1, N2 and N3

[speedlightning]

:ugh:N= Speed ( rotational) measured in RPM or PERCENT
N1 Fan Speed, Low Compressor
N2 Turbine Spool, High Compressor
N3 Free Turbine

What does the letter "N" actually stand for ?
Is it a VECTOR BASIS FUNCTION similar to what one would find in other mathematical and physics formulae ?
eg f=ma, "f" = force
So.... how did the letter "N" come about ?

Please be as technical as anyone wants to be(is capable of )!

Cheers.:sad:

[The Nr Fairy]

I'll have a stab, but I suspect it's lost in the mists of time.

N = number (either actual, scaled or %)

in the same way we have

T = Temperature

P = Pressure

[ericferret]

Allison 250 engine, N1 compressor, N2 turbine

Nr Helicopter rotor speed

Arriel engine, NG compressor speed, NF Turbine speed also seen as NTL (Turbine libre i.e free turbine).

[ais2plot]

"N1 Fan Speed, Low Compressor
N2 Turbine Spool, High Compressor
N3 Free Turbine"?
Not for a 3 shaft (large civil) engine -
N1 is the speed of the low pressure spool (fan and LP turbine)
N2 is the speed of the intermediate pressure spool (IP compressor & turbine)
N3 is the speed of the high pressure spool (HP compressor & turbine)
Each section of turbine is physically connected to the corresponding compressor (=fan for low pressure spool), otherwise the turbine would just accelerate (until the disk explodes:\) and the compressor wouldn't compress.
I think 'N' is number, as in number of revolutions per minute, ie. relatively dimensionless compared to pressures, temperatures etc. Usually the values are percentages of an assumed max speed (although the actual max speeds e.g. full power takeoff) can be above or below 100% of the original design value).

[tescoapp]

it is generally standard for Mech eng types to always use N when referering to different shafts and gears when doing ratio's

I think it comes from the greek eta :- η which nobody can be bothered finding so N it is. All the older text books use η the new ones use N

All the ratio equations for power transfer through gear boxes etc use N1 N2 notation for different shaft speeds.

The N number will be different for different engines.

On a 2 shaft engine You will get N1 and N2.

On a three shaft engine you will have N1,N2 and N3

N to engineers is measured in whatever you like as it all works its self out as you are looking for a ratio.

N is only really used when you finding a none dimensional ratio.
And hence as the display is N1/N1(max)*100. N is the correct term.

If you were doing energy calc's you would use ω with the shaft number as a subscript. ω being in radians per second.