23.3.8 Point Properties for Pressure-Swirl Atomizer Injections

For a pressure-swirl atomizer injection, you will specify some of the same properties as for a plain-orifice atomizer. In addition to the position, axis (if 3D), temperature, mass flow rate, duration of injection (if unsteady), injector inner diameter, and azimuthal angles (if relevant) described in Section  23.3.7, you will need to specify the following parameters under Point Properties:

• spray angle

  Set the value of the spray angle of the injected stream in the Spray Half Angle field ( $\theta$ in this equation in the separate Theory Guide).

• pressure

  Set the absolute pressure upstream of the injection in the Upstream Pressure field ( $p_1$ in this table in the separate Theory Guide).

• sheet breakup

  Set the value of the empirical constant that determines the length of the ligaments that are formed after sheet breakup in the Sheet Constant field ( $\ln (\frac{\eta_b}{\eta_0})$ in this equation in the separate Theory Guide).

• ligament diameter

  For short waves, set the proportionality constant that linearly relates the ligament diameter, $d_L$, to the wavelength that breaks up the sheet in the Ligament Constant field (see this equation - this equation in the separate Theory Guide).

• dispersion angle

  For a smooth distribution of the droplets, the initial velocities is varied within this dispersion angle. A scetch of the Atomizer Dispersion Angle for a flat fan atomizer is depicted in Figure  23.3.5.

See this section in the separate Theory Guide for details about how these inputs are used.