# What is the effect of power extraction on turbofan compressor and turbine maps?

Effects of Power Extraction on Turbofan Compressor and Turbine Maps

The two diagrams below show the effects of shaft power extraction (shaft power offtake / shaft power off-take for the propulsion of accessories such as fuel-/hydraulic-/oil-pumps, generators etc.) on a high-bypass turbofan engine at a flight altitude of $H = 11km$ and a speed of $Ma = 0.8$, calculated with GasTurb 12:

Effects of Power Extraction on the Operating Line (Blue)

• Why are the operating lines (blue) of both the compressor and turbine shifted to the left towards the surge line?
• In particular, why does the non-dimensional corrected mass flow decrease, while the pressure ratio stays approximately constant?
• The same question from a different angle: Why does the pressure ratio not decrease at a constant mass flow?