What is the purpose of a split-spool compressor in a gas turbine engine?

What is the purpose of a split-spool compressor in a gas turbine engine?

• A. To reduce weight
• B. To allow high compressive pressure ratios and improve high altitude operation
• C. To simplify maintenance
• D. To increase turbine temperature

Answer: (B)

Split-spool means the compressor stages are on separate shafts, each with its own turbine, so each section can run at its own optimal speed. This decoupling lets the high-pressure compressor reach higher speeds and pressures without being forced to match the low-pressure compressor’s speed. The result is a higher overall pressure ratio and better efficiency, especially at high altitude where air density is low and you need more compression to achieve the same turbine inlet conditions. In short, this design enhances performance and operability across a wide range of conditions by letting the high- and low-pressure stages be optimized independently.

Split-spool means the compressor stages are on separate shafts, each with its own turbine, so each section can run at its own optimal speed. This decoupling lets the high-pressure compressor reach higher speeds and pressures without being forced to match the low-pressure compressor’s speed. The result is a higher overall pressure ratio and better efficiency, especially at high altitude where air density is low and you need more compression to achieve the same turbine inlet conditions. In short, this design enhances performance and operability across a wide range of conditions by letting the high- and low-pressure stages be optimized independently.