Determination of the Momentum Drag within the Turbojet Engine Laboratory While Operating the J-57-8B Turbojet Engine

Abstract

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