Abstract
An experimental investigation has been completed of the performance and operability of a first of its kind 0.289 scale boundary layer ingesting propulsor within the new 6.5ft × 6ft transonic embedded propulsor testbed of NASA’s 8ft × 6ft Supersonic Wind Tunnel. This propulsor consisted of a coupled inlet and distortion-tolerant fan stage design embedded in a simulated upper aft hybrid wing body aircraft installation. The boundary layer ingesting inlet had a length-to-diameter ratio of 0.67. The distortion tolerant fan was 22 inches in diameter and had a stage pressure ratio of 1.34 and a bypass ratio of 16. The embedded propulsor was evaluated at its Mach 0.78 local freestream conditions. At peak efficiency 100% design speed test conditions, it provided a mass flow weighted inlet total pressure recovery of 96.5% and an adiabatic fan stage efficiency of 87.9%. These values differed meaningfully from the pre-test computational fluid dynamic analysis based design intent. At this operating condition, the effects of inlet-fan coupling extended approximately 0.45 fan diameters upstream into the inlet. The inlet was measured to have a stability margin of approximately 28% and was pre-entry boundary layer separation limited. The fan had approximately 12% of stability margin at 100% corrected speed at which conditions it was flutter limited. It exhibited otherwise flutter free operation over its entire aircraft cruise operating map. Consistently increasing levels of fan stability margin were demonstrated at successively lower fan speeds to in excess of approximately 24% at 80% corrected speed. At each of these reduced speeds, fan stability margin was full annulus stall limited. Inlet airflow distortion remained one-per-rev throughout all tested conditions. At peak efficiency 100% speed test conditions, the boundary layer ingesting inlet airflow had steady state radial and circumferential ARP1420 distortion intensities of 1.2 and 7.2%, respectively. Peak time-variant distortion intensities of 2.3% radial and 8.9% circumferential were also recorded. Comparisons to pre-test computational fluid dynamic predictions are also provided.
Experimental investigation of vertical turbulent transport of a passive scalar in a boundary layer: Statistics and visibility graph analysis
