Static conditions
Static conditions
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Static conditions can be calculated at every engine station using the using the Exit static conditions box in (most) gas path components design tab sheets.
With the total properties (temperature and pressure) and flow rate calculated at every cycle calculation iteration step for evaluation the model equations for conservation of mass and energy, static pressure and temperature can only be calculated if flow velocity is know. Flow velocity can only be calculated if flow cross area A is given for the particular station. Alternatively, also velocity or mach number can be specified and then flow area calculated. In summary, with a value specified for either area, velocity or mach number, the other 2 can be calculated. Iteration is required to accurately maintain the correct relations for total to static conditions including the depending of density and sonic velocity of static temperature and pressure.
In GSP, engine station static conditions are calculated in the component just upstream of the station which means the component exit static condition is calculation. Since this corresponds to the inlet static condition of the next component, separate inlet static condition calculation is omitted to prevent duplication and conflicting data. So if a component inlet static condition is desired, use the upstream component the Exit static conditions option instead. Select the desired parameter for specifying static conditions (area, mach number or velocity) and enter an appropriate value. Note that unrealistic values will cause iteration failure and error messages. Also supersonic flow is inhibited and will be reported as an error.
Note that there are special gas path components which have exceptions to these rules or include additional internal stations or locations for calculation static conditions:
The inlet has no upstream gas path component for calculating inlet station static conditions so a separate inlet static parameter edit box is added above the exit one.
The exhaust nozzle inlet static conditions can be calculated by the upstream component. For the throat and exit stations, dedicated models are used to calculate static conditions including supersonic conditions in case of a con-di nozzle.
The combustor has a separate Burner static conditions Duct cross area for enabling calculation of averaged static conditions inside the combustor (between the inlet and exit stations) required for Fundamental pressure loss calculation and for afterburner mode efficiency map reading.
The mixer calculates separate mixing plane static conditions, required to calculate the equations relating the two mixing flows (usually using conservation of momentum and assuming a user specified relation between the two entry flow static conditions). Only the mixing plane exit corresponds to the component exit engine station.