Originally Posted by deuzx
When you reduce the N1 with 10% does the thrust reduces with 30%?
That's about right for a low bypass engine, where the exponent for the N1 to Thrust derivative was 3.5,
i.e. Thrust is proportional to N1 ^ 3.5
This exponent is significantly reduced as bypass increases, as 'core' thrust has an exponent of 3.5, whilst the fan produced thrust, like a propeller has an exponent of 2. Thus, as bypass ratio increases, the exponent will reduce from a 'base-line' 3.5 to something above 2.
In comparing 90% N1 to 100% N1, a low bypass engine would experience a 31.7% increase in thrust, a pure fan engine would experience a 23.5% increase in thrust. The CFM-56 that you refer to would be somewhere between these two.
Regards,
Old Smokey