Boundary-Layer-Ingesting Inlet Flow Control

Abstract

This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCP avg ) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow. Nomenclature a = distance between the inlet lip highlight station and the inlet throat station (see fig. 3), in. A C = inlet capture (highlight) area; area enclosed by inlet highlight (see fig. 3 for highlight definition) and tunnel wall, in. = distance between the inlet highlight height and the inlet throat height (see fig. 3), in. D 2 = duct diameter at AIP (see fig. 3), in. DPCP avg = average SAE circumferential distortion descriptor DPRP i = SAE radial distortion descriptor for ring i on AIP total-pressure rake h = height of vortex generator, in. H = boundary-layer shape factor, δ * /θ H i = height of inlet throat (see fig. 3), in. H max = maximum height of inlet cowl (see fig. 3), in. ΔH = distance between inlet throat centroid and duct exit centroid (see fig. 3), in. i = ring number on AIP total-pressure rake, value increases from 1 in hub region to 5 in tip region L = length of inlet duct from throat to AIP (see fig. 3 https://ntrs.nasa.gov/search.jsp?R=20060004990 2018-05-11T22:26:25+00:00ZAmerican Institute of Aeronautics and Astronautics 2 P t = free-stream total pressure, psi P t,2,avg = area weighted average total pressure at AIP P t,2,avg /P t = inlet recovery pressure ratio Rn/ft = R...

Numerical Modeling of Flow Control in a Boundary-Layer-Ingesting Offset Inlet Diffuser at Transonic Mach Numbers

“…The numerical simulations of the BLI inlet with flow control jets and vanes are compared to the experimental wind tunnel results of Owens, Allan, and Gorton 26 . The transonic BLI inlet experiments were conducted at NASA Langley's 0.3-Meter Transonic Cryogenic Tunnel (0.3-Meter Tunnel) for a BLI offset inlet mounted on the tunnel sidewall.…”

“…Experimental data for the baseline BLI inlet in transonic flow was performed by Berrier and Morehouse 25 , which were also used to validate OVERFLOW 6 . These validations of the flow solver provided confidence in the design of flow control jets for a flow control BLI inlet experiment at transonic Mach numbers 26 . The flow solver was used to identify candidate jet actuator locations, which were then used in the modification of the baseline BLI inlet model.…”

“…A DOE was also performed for a VG vane configuration to be tested at transonic Mach numbers performed by Allan, Owens, and Lin 27 . This research will use the experimental wind tunnel results of Owens, Allan, and Gorton 26 for the validation of OVERFLOW. A comparison of the engine fan-face distortion levels, average total pressure recovery, and static inlet wall pressures are made for a single jet actuator and vane configuration.…”

Passive Flow Control Study in an S-Duct Using Stereo Particle Image Velocimetry

“…In addition, active flow control methods such as pulsed or continuous air jets [14,24] have also been studied.…”

Optimal Design of Passive Flow Control for a Boundary-Layer-Ingesting Offset Inlet Using Design-of-Experiments

“…Experimental data for the baseline BLI inlet in I transonic flow was obtained by Berrier and Morehouse 25 and was used to validate OVERFLOW for the baseline case 6 . These validations of the flow solver provided confidence to use OVERFLOW for the design of flow control jets in the BLI inlet for an experiment at transonic Mach numbers 26 . The flow solver was used to identify candidate jet actuator locations that were built into the BLI inlet wind tunnel model.…”