Table of Contents
- 1 What is the purpose of using a CD nozzle?
- 2 What is the relation between back pressure and exit pressure in case of subsonic flow at the nozzle exit?
- 3 What is flow choking in a CD nozzle?
- 4 Why expansion shock is not possible?
- 5 Why is my CD nozzle not producing thrust?
- 6 What happens when you don’t choke a nozzle?
What is the purpose of using a CD nozzle?
Cylinder A contains air at high pressure, and takes the place of the chamber. The CD nozzle exhausts this air into cylinder B, which takes the place of the tank.
What is the relation between back pressure and exit pressure in case of subsonic flow at the nozzle exit?
For subsonic flows, the exit pressure is always equal to the back pressure, so p o p exit = 1.020 leads to p b = 0.98 MPa for the subsonic expansion. For the supersonic case, this is called the perfect supersonic expansion because the exit plane pressure in the supersonic exit flow matches exactly the back pressure.
What is flow choking in a CD nozzle?
Choked flow is a fluid dynamic condition associated with the venturi effect. When a flowing fluid at a given pressure and temperature passes through a constriction (such as the throat of a convergent-divergent nozzle or a valve in a pipe) into a lower pressure environment the fluid velocity increases.
Why do nozzles increase pressure?
To maintain a constant amount of fluid moving through the restricted portion of the nozzle, the fluid must move faster. The energy to make this fluid speed up has to come from somewhere. Some energy is in the random motion of molecules, which we observe as pressure.
Why supersonic flow Cannot be achieved using a converging nozzle?
The exhaust jet will be having a temperature over 700 Celsius which makes speed of sound to have a higher value (Approx 600 m/s). Unless it is a converging diverging nozzle, the velocity inside the nozzle cannot breach the sound barrier.
Why expansion shock is not possible?
Each wave in the expansion fan turns the flow gradually (in small steps). It is physically impossible for the flow to turn through a single “shock” wave because this would violate the second law of thermodynamics.
Why is my CD nozzle not producing thrust?
For our CD nozzle, if the flow in the throat is subsonic, the flow downstream of the throat will decelerate and stay subsonic. So if the converging section is too large and does not choke the flow in the throat, the exit velocity is very slow and doesn’t produce much thrust.
What happens when you don’t choke a nozzle?
When the nozzle isn’t choked, the flow through it is entirely subsonic and, if you lower the back pressure a little, the flow goes faster and the flow rate increases. As you lower the back pressure further the flow speed at the throat eventually reaches the speed of sound (Mach 1).
What are the advantages and disadvantages of the flow nozzle?
Advantages and disadvantages of the flow nozzle. Advantages. Compact – Low dimension as compared to venturi meter. Cheaper and easy to install as compared to venturi meter. High coefficient of discharge than the orifice meter. Less susceptible to wear.
How does the Mach number of a nozzle increase?
In a steady internal flow (like a nozzle) the Mach number can only reach 1 at a minimum in the cross-sectional area. When the nozzle isn’t choked, the flow through it is entirely subsonic and, if you lower the back pressure a little, the flow goes faster and the flow rate increases.