What happens to pressure in the exhaust duct when an exhaust cone is placed aft of the turbine?

When an exhaust cone is placed aft of the turbine, it serves to direct the exhaust flow and can influence the pressure and velocity of the gases exiting the turbine. The exhaust cone effectively acts as a nozzle that reduces the cross-sectional area of the flow path, which enhances the exhaust gas velocity while simultaneously affecting the pressure dynamics.

As the exhaust gases pass through the exhaust cone, the reduction in area leads to an increase in velocity due to the conservation of mass (continuity equation). As the gases accelerate, the pressure in the exhaust duct behind the cone increases. This increase in pressure can be attributed to the way the exhaust cone captures and guides the turbulent flow, allowing for a more streamlined exit of the gases.

Hence, the correct assessment is that the pressure increases while the velocity decreases. This phenomenon aligns with the principles of fluid dynamics that govern turbine exhaust behavior. The relationship between pressure and velocity is governed by Bernoulli's equation, which illustrates that as the velocity of a fluid increases, there is often a corresponding change in pressure.

Understanding this concept is crucial for recognizing how design elements in turbine engines influence performance, efficiency, and overall system behavior.