SLIDE 1
B Y : E V A N N E Y 1 2 / 1 6 / 1 4
Converging Diverging Nozzle - Background
Hour glass shaped nozzle
Inlet of decreasing cross sectional area
Outlet of increasing cross sectional area
Used to accelerate pressurized fluid to supersonic speeds
Useful in many turbine and jet engine applications.
Reference 1
Outlet (Back) Pressure HIGH LOW
Fully subsonic isentropic flow
Velocity increases in converging section and decreases in diverging section
Flow becomes choked (Mach 1 at throat)
Upper limit of back pressure range for shocks
Converging section becomes time independent
Normal shock wave is formed near throat
Instantaneous property changes across shock
Pressure increase
Temperature increases
Velocity decreases
Shock wave location moves towards outlet
Shock is just at outlet. More complex shock patterns begin to occur
Flow pressure at exit is less than ambient pressure – Overexpanded nozzle
Fully supersonic isentropic flow (design condition)
Lower limit of back pressure for shocks in
- verexpanded flow
Back pressure low enough that it equals the nozzle exit pressure
Shocks disappear
𝒆𝑩 𝑩 = 𝒆𝑾 𝑾 (𝑵𝟑 − 𝟐)