What is the effect of turbine on bleed air pressure, temperature, and velocity supplied to the air conditioning system?

• A. Increase pressure, increase temperature, decrease velocity
• B. Decrease pressure, decrease temperature, increase velocity
• C. Decrease pressure, increase temperature, increase velocity
• D. Increase pressure, decrease temperature, increase velocity

Answer: (B)

The main idea is what happens to bleed air as it expands through the turbine in the air conditioning system. When high-pressure bleed air enters the turbine, some of its energy is converted into shaft work to drive the cycle’s compressor and other components. This expansion causes the air to drop in pressure and temperature, because the gas does work on the turbine blades and cools as it expands. At the same time, the flow is accelerated as it passes through the turbine channels, so the air exits with higher velocity than it had entering.

So, bleed air after the turbine ends up with lower pressure, lower temperature, and higher velocity.