Generation after Next Propulsor Research: Robust Design for Embedded Engine Systems

Abstract

have contracted to pursue multidisciplinary research into boundary layer ingesting (BLI) propulsors for generation after next environmentally responsible subsonic fixed wing aircraft. This Robust Design for Embedded Engine Systems project first conducted a high-level vehicle system study based on a large commercial transport class hybrid wing body aircraft, which determined that a 3 to 5 percent reduction in fuel burn could be achieved over a 7,500 nm mission. Both pylonmounted baseline and BLI propulsion systems were based on a low-pressure-ratio fan (1.35) in an ultra-high-bypass ratio engine (16), consistent with the next generation of advanced commercial turbofans. An optimized, coupled BLI inlet and fan system was subsequently designed to achieve performance targets identified in the system study. The resulting system possesses an inlet with total pressure losses less than 0.5%, and a fan stage with an efficiency debit of less than 1.5% relative to the pylon-mounted, clean-inflow baseline. The subject research project has identified tools and methodologies necessary for the design of nextgeneration, highly-airframe-integrated propulsion systems. These tools will be validated in future large-scale testing of the BLI inlet / fan system in NASA's 8 ft x 6 ft transonic wind tunnel. In addition, fan unsteady response to screen-generated total pressure distortion is being characterized experimentally in a JT15D engine test rig. These data will document engine sensitivities to distortion magnitude and spatial distribution, providing early insight into key physical processes that will control BLI propulsor design. Nomenclature 0 = free stream U = velocity difference  p = propulsive efficiency AEDC = Arnold Engineering Development Complex AIP = aerodynamic interface plane BLI = boundary layer ingesting BPF = blade passing frequency BWB = blended wing body CAEP = Committee on Aviation Environmental Protection 2 conv = conventional ERA = Environmentally Responsible Aviation (Project) EXTE = extended trailing edge FAR = Federal Aviation Regulations HWB = hybrid wing body ICAO = International Civil Aviation Organization, a United Nations Specialized Agency in = inlet ITAPS = Integrated Total Aircraft Power System j = jet (nozzle exhaust) LTO = landing and take-off m  = air mass flow rate MIT = Massachusetts Institute of Technology N+1 = next generation (similarly, N+2 = generation after next, and so forth) N2A = generation after next airframe designed for podded engines NASA = National Aeronautics and Space Administration NRA = NASA Research Announcement NPSS = Numerical Propulsion System Simulation P = power P&W = Pratt & Whitney, a United Technologies Company P&WC = Pratt & Whitney Canada, a United Technologies Company RANS = Reynolds averaged Navier Stokes SFW = Subsonic Fixed Wing (Project) SPL = sound power level T = thrust TSFC = thrust specific fuel consumption TWT = transonic wind tunnel U = velocity U = mass averaged velocity UCI = University of California, Irvine UHB = ultra-high bypass USAF = United States ...

NASA's Role in Gas Turbine Technology Development: Accelerating Technical Progress Via Collaboration Between Academia, Industry, and Government Agencies

“…NASA partnered with UTRC, Pratt & Whitney, and Virginia Polytechnic and State University (Virginia Tech) through the NRA to exploit the optimal design space and to design and build an integrated inlet and fan embedded system. A sampling of the relevant publications supporting this activity including the simulated aircraft boundary layer, the embedded inlet and distortion tolerant fan design, and the aeromechanics analysis is found in References [104][105][106][107][108][109][110]. NASA recently completed the testing of a distortion-tolerant fan with a relevant boundary layer inflow field in the 8-by 6-Foot Supersonic Wind Tunnel at GRC.…”

The Effect of Incoming Boundary Layer Characteristics On The Performance Of a Distributed Propulsion System

“…A significantly improved inlet design by United Technologies Research Center (UTRC) under NASA's Subsonic Fixed Wing Project fulfills multiple objectives for an optimal inlet, maximizing BLI benefits without increasing weight and drag [20]. More recently, NASA, UTRC, and Virginia Polytechnic performed a series of tests with a novel boundary layer ingesting inlet/ distortion-tolerant fan (BLI2DTF) in NASA's 8 × 6 transonic wind tunnel [21,22,23]. Similarly, CFD-based analyses of Liou and Lee [24] for a hybrid wing body and Lee and Liou [10] for the STARC-ABL configuration underscore continued interest in designing optimal geometries to minimize distortion related penalties.…”

Vehicle Level System Impact of Boundary Layer Ingestion for the NASA D8 Concept Aircraft

“…The ultimate impact of a DTF design on the engine fan efficiency for a BLI propulsor is an area that NASA's AATT Project has been researching for several years. A Boundary Layer Ingestion Inlet / Distortion-Tolerant Fan (BLI2DTF) Task was created to research BL ingestion technology that could enter service in the 2020-2025 time frame [13]. NASA partnered with United Technologies Research Center (UTRC) to design, analyze, and fabricate a BL ingesting inlet coupled with a 22" diameter distortion-tolerant fan, which was tested in the NASA Glenn Research Center 8'x6' Supersonic Wind Tunnel (SWT) [14].…”