Reingestion characteristics and inlet flow distortion of V/STOL lift-engine fighter configurations
Jerry V. Kirk, Jerry P. Barrack, Ames Research Center, United States. National Aeronautics and Space Administration
National Aeronautics and Space Administration, 1970 - Jet engines - 41 pages
Reingestion of exhaust gas into engine inlets during hover, and inlet flow distortion with the associated loss in total-pressure recovery during transition were studied using a largescale generalized lift-engine fighter model powered by 5-85 engines. Exhaust gas reingestion during hover was studied on a static test facility, and inlet flow distortion and total-pressure recovery loss were studied in the 40- by 80-foot wind tunnel. Two lift-engine arrangements were studied, the swiveling, retractable and the internally fixed. Both arrangements were subject to excessive thrust loss and compressor stalls due to reingestion when the engine exhaust was vectored nearly vertical. Vectoring the exhaust approximately 20' from vertical essentially eliminated reingestion problems. Vectoring the lift-engine exhaust forward and the lift-cruise engine exhaust aft tcr balance the aircraft and minimize reingestion appears to be a feasible means of allowing VTOL operation. Inlet flow distortion and total-pressure recovery were within acceptable limits for the swiveling, retractable lift-engine configuration. With the inlet guide vane installed to help turn the flow into the engine, the vertically mounted lift engines of the internally fixed configuration with an inlet radius to diameter ratio of 0.19 produced acceptable inlet flow distortion and totalpressure recovery results. Without the guide vane the nominal acceptable distortion level of 10 percent was exceeded at the higher velocity ratios.--P. i.
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80-foot wind tunnel angle of attack average inlet temperature compressor face compressor stalls diameter ratio distortion and pressure distortion and total-pressure engine angles Engine number engine stall exhaust gas pressure Exhaust gas reingestion exhaust nozzles exhaust vectoring exhaust was vectored fixed lift engines forward free Ingestion light free Stall free fuselage ground height guide vane installed higher velocity ratios hot exhaust hover Ingestion free Ingestion Ingestion light Ingestion inlet distortion inlet flow distortion inlet guide vane inlet radius inlet temperature rise internally fixed configuration leading-edge lift-cruise engine exhaust lift-cruise engine inlets lift-engine fighter model lift-engine inlets light Ingestion light light to moderate maximum temperature gradients moderate Ingestion moderate mounted lift engines number l engine pressure recovery pressure transients retractable configuration retractable lift shown in figure sideslip angle slotted nozzles Stall engine Stall free Stall swivel plane temperature distortion thermocouple thrust vectors total-pressure recovery V/STOL vector angle VTOL wing