🔍 Key Concepts

• Axial-flow gas turbine flow path: air moves from left (inlet) to right (turbine exhaust) in the illustration. • Difference between ambient inlet (before the compressor) and compressor discharge (after all compressor stages). • Typical location of a compressor inlet pressure sensor (Pt2 or CPD-1) on marine gas turbines – usually at or just inside the compressor bellmouth before the first stage blades.

💭 Think About

• On the illustration, identify where air first enters the compressor section. Which label is closest to the point where air has just passed the inlet guide vanes but has not yet been compressed by the first rotor stage? • Compare the labels AA, BB, DD, and EE: which ones are clearly located in later compressor or turbine stages, and which is positioned right at the entrance to the compressor? • Think about what the engine control system needs from a compressor inlet pressure sensor: does it make more sense to measure where pressure is still close to ambient, or where it has already been compressed several stages? Where would that be on this drawing?

✅ Before You Answer

• Confirm which label is closest to the front face of the compressor (bellmouth/inlet guide vane area). • Eliminate any labels that are clearly in the turbine section or near high-pressure compressor discharge rather than the inlet. • Verify that the selected label is on the inner gas path (not in an external bleed or cooling line), right where air enters the compressor flow annulus.