The flow splitter splits a flow into two flows according to the Split Fraction SR. SR is the fraction of Splitter entry flow that is diverted to the secondary exit. So with SR = 0, all is going to exit 1, with SR = 1 all is going to exit 2. With SR = 0.5 for example, each exit gets half of the flow.
The Split fraction can be free state, user specified fixed or user specified variable. The last option requires an additional Flow Splitter Control component.
Use the split fraction for blowing off air somewhere from the gas path, either to model large compressor bleed flows (APU case) or secondary air flows that may go into a gas path elwsewhere using a Mixer component.
Specify design split fraction and exit static conditions as area, velocity or mach nr on the Design tab sheet.
The DownStream Calculation option is to specify which downstream gas path (1 or 2) is calculated first. This is for cases where bleeds must be calculated in one downstream gas path that is used in the other. For example: is bleed from a duct downstream of exit 2 is inserted somewhere downstream exit 1, the 2 flow must first be calculated (DownStream Calculation = 2 First).
In the case of both flows from 1 to 2 and vice versa, the problem can not be made 'determinate' anymore and splitter and mixer components must be used (instead of bleeds/sec. airflows) to model the secondary flows, like in the ABFAN_SECAIR model (same case for Fan instead of Splitter).
Flow Splitter
