Converging diverging nozzle

Theory:

A nozzle is a relatively simple device, just a specially shaped tube through which hot gases flow. Ramjets and rockets typically use a fixed convergent section followed by a fixed divergent section for the design of the nozzle. This nozzle configuration is called a convergent-divergent, or CD, nozzle. In a CD nozzle, the hot exhaust leaves the combustion chamber and converges down to the minimum area, or throat, of the nozzle. The throat size is chosen to choke the flow and set the mass flow rate through the system. The flow in the throat is sonic which means the Mach number is equal to one in the throat. Downstream of the throat, the geometry diverges and the flow is isentropically expanded to a supersonic Mach number that depends on the area ratio of the exit to the throat. The expansion of a supersonic flow causes the static pressure and temperature to decrease from the throat to the exit, so the amount of the expansion also determines the exit pressure and temperature. The exit temperature determines the exit speed of sound, which determines the exit velocity. The exit velocity, pressure, and mass flow through the nozzle determines the amount of thrust produced by the nozzle.

Geometry:

Meshing:

Nodes-1752

Elements-1656

Pre-processing physics set up

Solver: density based

Simulation: steady state

Material: air

Viscous model: inviscid

Boundary conditions:

Inlet pressure- 101325Pa

Outlet pressure-2815Pa

Operating pressure-0Pa

Temperature: 300K

Convergence plot:

Post processing:

Pressure variation

Temperature variation

Mach variation

Pressure contour

velocity contour

temperature contour

conclusions:

• the mesh has been performed smoothly to capture the variation of temperature, pressure and velocity.
• the variation of pressure, velocity and temperature is shown as a function of nozzle distance.