In a dual-spool engine, N1 and N2 refer to rotor speeds of which components?

In a dual-spool engine, N1 and N2 refer to rotor speeds of which components?

• A. Low Pressure (N1) And High-Pressure (N2) Compressors
• B. Fans And Turbines
• C. Inlet Guide Vanes And Outlet Vanes
• D. Pumps And Shafts

Answer: (A)

In a dual-spool engine, there are two independent rotating assemblies or spools, each with its own shaft and compressor stages. N1 is the rotational speed of the low‑pressure spool, which includes the fan and the low‑pressure compressor. N2 is the rotational speed of the high‑pressure spool, which includes the high‑pressure compressor. These two speeds can vary independently, reflecting how each spool is driven by its own turbine on its own shaft. So the rotor speeds referred to by N1 and N2 are specifically the Low Pressure and High-Pressure Compressors. The other options don’t fit as well: the idea of fans and turbines mixes components tied together on the spools rather than naming the rotor speeds of the compressors themselves; inlet and outlet vanes are stationary and don’t have rotor speeds; pumps and shafts aren’t the standard way these rotor speeds are described in this context.

In a dual-spool engine, there are two independent rotating assemblies or spools, each with its own shaft and compressor stages. N1 is the rotational speed of the low‑pressure spool, which includes the fan and the low‑pressure compressor. N2 is the rotational speed of the high‑pressure spool, which includes the high‑pressure compressor. These two speeds can vary independently, reflecting how each spool is driven by its own turbine on its own shaft. So the rotor speeds referred to by N1 and N2 are specifically the Low Pressure and High-Pressure Compressors.

The other options don’t fit as well: the idea of fans and turbines mixes components tied together on the spools rather than naming the rotor speeds of the compressors themselves; inlet and outlet vanes are stationary and don’t have rotor speeds; pumps and shafts aren’t the standard way these rotor speeds are described in this context.