Flow in Boundary Layer Ingesting Serpentine Inlets

Ferrar, Anthony M.

doi:10.2514/6.2011-5568

Cited by 11 publications

(6 citation statements)

References 4 publications

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“…In BLI S-ducts, the largest separations occur in regions of combined high curvature and high diffusion. 37 The most common separation is along the bottom wall, where the low-momentum airframe boundary layer does not have the energy to remain attached under diffusion and extreme curvature ( Figure 6). The pressure deficit region at the bottom of the engine Aerodynamic Interface Plane (AIP) due to the ingested boundary layer is worsened by the massive separation occurring at the first bend.…”

Section: Total Pressure Distortionmentioning

confidence: 99%

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Progress in Boundary Layer Ingesting Embedded Engine Research

Ferrar¹,

O’Brien²

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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Modern aviation requirements for energy efficiency and environmental compatibility push air vehicle development toward highly integrated systems in which each component, and the system, is optimized for overall performance. Embedded engines and boundary layer ingesting propulsion systems have the potential to simultaneously improve fuel burn, noise, and emissions. Energizing the boundary layer of a drag-producing object has been recognized as a viable method to effectively reduce drag as part of the propulsion process for many years. For decades, investigators have suggested different methods for energizing boundary layers with propulsion systems. A wealth of publications forms a body of work including mathematical predictions of the effects of boundary layer ingestion and explanations of the physical basis for the process. This paper seeks to present a review of this work, in light of results from current research, to provide a reference and vision for the continuing development of boundary layer ingesting embedded engine technology.

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Section: Total Pressure Distortionmentioning

confidence: 99%

“…1 Additional losses within the BLI inlet arise from the complex flow structures discussed above. 37,43 The effects represent an inefficient inlet, with typical face-averaged recoveries of 0.977. By comparison, podded inlets can achieve recoveries on the order of 0.998 or better.…”

Section: A Engine Cycle Effectsmentioning

confidence: 99%

Progress in Boundary Layer Ingesting Embedded Engine Research

Ferrar¹,

O’Brien²

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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“…To meet this need, Virginia Tech planned experimental investigations to examine the flow produced in and by a BLI inlet and to measure its JT15D engine fan's response to such distortions. [25][26][27] Owing to its part-span shroud which limited aeromechanical blade deflections, the JT15D engine was viewed as being well suited for this pioneering propulsion research. Initiated early in the Robust Design project before its inlet or fan were designed, this effort leveraged the high quality, computational and experimental database which resulted from prior research conducted by NASA Langley.…”

Section: Approachmentioning

confidence: 99%

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

Arend

Tillman²,

O’Brien

2012

48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference &Amp;amp; Exhibit

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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 ...

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“…According to the analysis described by Ferrar for the same pressure measurement system, the uncertainty of the AIP pressure measurement system is ± 0.046 psi 3 . The documentation accompanying the NI 9211 when used in an NI cDAQ-9172 chassis claims a measured temperature uncertainty of ± 2 K. The Monarch Instruments ACT-3X tachometer claims an accuracy of 0.001% of the reading, with a resolution of 1 RPM.…”

Section: B Uncertainty Analysismentioning

confidence: 99%

“…This has resulted in the emergence of a hybrid wing-body (HWB) vehicle in which the fuselage is designed to produce a significant portion of the overall lift. These vehicle configurations lend themselves to the option of embedding the engines at the rear of the fuselage such that they ingest the boundary layer that forms over the fuselage, as shown in Figure 1.1 3 . By ingesting and re-energizing the boundary layer that has formed over the fuselage of the aircraft, the aircraft's drag can be substantially reduced 2 .…”

Section: Introductionmentioning

confidence: 99%

Effect of BLI–Type Inlet Distortion on Turbofan Engine Performance

Lucas

O’Brien

Ferrar

2014

Volume 1A: Aircraft Engine; Fans and Blowers

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Boundary Layer Ingestion (BLI) is currently being researched as a potential method to improve efficiency and decrease emissions for the next generation of commercial aircraft. While reenergizing the boundary layer formed over the fuselage of an aircraft has many system level benefits, ingesting the low velocity boundary layer flow through a serpentine inlet into a turbofan engine adversely affects the performance of the engine. The available literature has only yielded studies of the effects of this specific type of inlet distortion on engine performance in the form of numerical simulations. This work seeks to provide an experimental analysis of the effects of BLI-type distortion on a turbofan engine's performance. A modified JT15D-1 turbofan engine was investigated in this study. Inlet flow distortion was created by a layered wire mesh distortion screen designed to create a total pressure distortion profile at the aerodynamic interface plane (AIP) similar to NASA's Inlet A boundary layer ingesting inlet flow profile. Results of this investigation showed a 15.5% decrease in stream thrust and a 14% increase in TSFC in the presence of BLI-type distortion.Flow measurements at the AIP and the bypass nozzle exit plane provided information about the losses throughout the fan flow path. The presence of the distortion screen resulted in a 24% increase in mass-averaged entropy production along the entire fan flow path compared to the non-distorted test. A mass-averaged fan flow path efficiency was also calculated assuming an isentropic process as ideal. The non-distorted fan flow path efficiency was computed to be 60%, while the distorted fan flow path efficiency was computed to be 50.5%, a reduction in efficiency of 9.5%. The entropy generation between ambient conditions and the AIP was compared to the entropy production along the entire fan flow path. It was found that the majority of entropy generation occurred between the AIP and bypass nozzle exit. Based on flow measurements at the bypass nozzle exit plane, it was concluded that inlet flow distortion should be located away from the tip region of the fan in order to minimize losses in a very lossy region. It was also determined that the fan and bypass duct process the different regions of the total pressure distortion in different ways. In some regions the entropy production decreased for the distorted test compared to the clean test, while in other regions the entropy production increased for the distorted test compared to the clean test. Finally, it was found that small improvements in total pressure and total temperature variation at the bypass nozzle exit plane will greatly improve the fan flow path efficiency and entropy generation, thereby decreasing performance losses.iii

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Flow in Boundary Layer Ingesting Serpentine Inlets

Cited by 11 publications

References 4 publications

Progress in Boundary Layer Ingesting Embedded Engine Research

Progress in Boundary Layer Ingesting Embedded Engine Research

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

Effect of BLI–Type Inlet Distortion on Turbofan Engine Performance

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