Most gas path components allow specification of volumes to allow calculation of volume effects during transients. Volumes in the gas path act as buffers capable of temporarily storing extra gas due to relatively large pressures during an acceleration for example. Components with relatively large volume such as recuperators can have a significant effect on transient performance.
Note that large volumes may easily lead to unstable system operation and therefore also to numerical convergence problems in GSP. Therefore, volumes often need to be specified between components and in GSP this is done by adding a duct component with a volume.
See the Technical manual for information on the theory and equations of volume effects.
Volume effects
