Limited tests were conducted at the USNPGS Astro /Aeronautical PropulsionLaboratories to determine the magnitude and variation of the momentumdrag which is developed within turboject engine test chamberwhile operating a J-57-8B powerplant. A survey of the aerodynamic characteristicsat the chamber inlet and the calculation of the momentum andenergy interchange at the engine exhaust plane reveal that this restric=tive drag which penalizes the "indicated" performance of the engine isapproximately 1.07» of the thrust output and varies directly with theratio of engine thrust to secondary airflow.Further tests will be necessary to evaluate the effects of the positioningof the exhaust augmenter and the variation of the exhaust coolingwater flow rate upon the secondary airflow and the resulting momentumdrag. With the completion of these surveys it is anticipated thatthe over-all accuracy of the facility thrust measuring system will bet 0.50% throughout the thrust range of 1000 to 30,000 lbs.
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