B737-800/900ER ATA 71 (POWERPLANT) "CFM 56-7 Dual Shaft High Bypass Ratio TurboFan Engine"

CFM 56-7 Dual Shaft High Bypass Ratio TurboFan Engine

26,400 LBS T/O Thrust

N1 = fan + 4 stage LPC (Driven by 4 stage LPT)
N2 = 9 stage HPC (Driven by a single stage HPT)

At low RPM, variable bleed valves open to relieve excessive air.
Also, in the first 4 stages of the HPC, VSVs (Variable Stator Vanes) are used to get better efficiency.

Variable bleed valves and VSV's help improve the engines stall margin & improve acceleration characteristics.