| 摘要 |
A method for determining the free-field thrust of a gas turbine engine 18 in an enclosed test facility 12 includes the steps of calculating the intake momentum drag 34 and cradle drag 36 and compensating for these losses. Drag 38 produced by an exhaust nozzle 24 may also be compensated for. The gas turbine 18 may be tested at various speeds to produce a performance curve. The cradle (2 see fig 1) comprises a load cell (10 see fig 1) measuring a net cradle force 32 and a movable support (4 see fig 1) mounted to a static structure (6 see fig 1) by flexure plates (8 see fig 1). An airflow meter 26 measures the mass flow 17 of air into the engine 18 and anemometers (54,56,58,60 see fig 4) monitor air velocities. The calculation of cradle drag takes account of the drag coefficient of each component.
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