Aerodynamic Analysis of a Boundary-Layer-Ingesting Distortion-Tolerant Fan

2013 ◽  
Author(s):  
Razvan V. Florea ◽  
Dmytro Voytovych ◽  
Gregory Tillman ◽  
Mark Stucky ◽  
Aamir Shabbir ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
High Performance ◽  
Risk Mitigation ◽  
Pressure Ratio ◽  
Wind Tunnel Test ◽  
Fuel Burn ◽  
Global And Local ◽  
The Impact ◽  
Stage Efficiency

The paper describes the aerodynamic CFD analysis that was conducted to address the integration of an embedded-engine (EE) inlet with the fan stage. A highly airframe-integrated, distortion-tolerant propulsion preliminary design study was carried out to quantify fuel burn benefits associated with boundary layer ingestion (BLI) for “N+2” blended wing body (BWB) concepts. The study indicated that low-loss inlets and high-performance, distortion-tolerant turbomachines are key technologies required to achieve a 3–5% BLI fuel burn benefit relative to a baseline high-performance, pylon-mounted, propulsion system. A hierarchical, multi-objective, computational fluid dynamics-based aerodynamic design optimization that combined global and local shaping was carried out to design a high-performance embedded-engine inlet and an associated fan stage. The scaled-down design will be manufactured and tested in NASA’s 8′×6′ Transonic Wind Tunnel. Unsteady calculations were performed for the coupled inlet and fan rotor and inlet, fan rotor and exit guide vanes. The calculations show that the BLI distortion propagates through the fan largely un-attenuated. The impact of distortion on the unsteady blade loading, fan rotor and fan stage efficiency and pressure ratio is analyzed. The fan stage pressure ratio is provided as a time-averaged and full-wheel circumferential-averaged value. Computational analyses were performed to validate the system study and design-phase predictions in terms of fan stage performance and operability. For example, fan stage efficiency losses are less than 0.5–1.5% when compared to a fan stage in clean flow. In addition, these calculations will be used to provide pretest predictions and guidance for risk mitigation for the wind tunnel test.

Evaluation of Wind Loads on FPSO Topsides Using a Numerical Wind Tunnel

2016 ◽  
Author(s):  
Daniel Barcarolo ◽  
Yann Andrillon ◽  
Erwan Jacquin ◽  
Alain Ledoux
Keyword(s):  
Boundary Layer ◽  
Numerical Model ◽  
Wind Tunnel ◽  
Atmospheric Boundary Layer ◽  
Scale Effects ◽  
Geometric Model ◽  
Wind Tunnel Test ◽  
Offshore Structures ◽  
Wind Loads ◽  
The Impact

The accurate evaluation of wind loads applied on floating offshore structures is extremely important as they are in specific conditions one of the dimensioning criteria for the mooring design. Nowadays these loads are mainly assessed through wind tunnel tests performed at model scale. Estimating realistic wind loads however, remains a big challenge. The complexity and associated simplification level of FPSO topside structures, the scale effects and the establishment of the atmospheric boundary layer imply that many simplifications are to be made. Typically, the FPSO topside is greatly simplified and equivalent blocs of wired frame are used. Today with the evolution of CFD software, and the increase of the meshing capacity, new scopes open to CFD. Aerodynamic simulations on complex FPSO structures are therefore now possible, but need specific developments and validations that are presented in this paper. The main objective of the work presented is to investigate the ability of CFD to evaluate wind loads on complex FPSOs topsides and to provide information on the impact of model simplifications made in wind tunnels. In a first stage, the numerical model was intensively validated by comparing its results to a wind tunnel test case. The numerical model was developed in order to ensure the quality of the results and enable a relevant comparison that was obtained with grids density up to 30 million cells. For this purpose, the geometric model used corresponds to the one used in wind tunnel. The same Atmospheric Boundary Layer was simulated and a thorough effort was performed to ensure the mesh convergence. In a second stage, more physical aspects of the wind tunnel methodology were investigated. Typically the accuracy of the blockage effect correction was evaluated by performing computations with and without blockage, and results were compared with classical corrections applied in wind tunnel. The impacts of the Atmospheric Boundary Layer on wind loads have also been investigated. Finally, the wind load contribution of each component of the FPSO was evaluated.

scholarly journals Technical note: Boundary layer height determination from Lidar for improving air pollution episode modelling: development of new algorithm and evaluation

2017 ◽  
Author(s):  
Ting Yang ◽  
Zifa Wang ◽  
Wei Zhang ◽  
Alex Gbaguidi ◽  
Nubuo Sugimoto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
High Performance ◽  
Accurate Determination ◽  
Technical Note ◽  
Strong Increase ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Retrieval Algorithms ◽  
The Impact

Abstract. Predicting air pollution events in low atmosphere over megacities requires thorough understanding of the tropospheric dynamic and chemical processes, involving notably, continuous and accurate determination of the boundary layer height (BLH). Through intensive observations experimented over Beijing (China), and an exhaustive evaluation existing algorithms applied to the BLH determination, persistent critical limitations are noticed, in particular over polluted episodes. Basically, under weak thermal convection with high aerosol loading, none of the retrieval algorithms is able to fully capture the diurnal cycle of the BLH due to pollutant insufficient vertical mixing in the boundary layer associated with the impact of gravity waves on the tropospheric structure. Subsequently, a new approach based on gravity wave theory (the cubic root gradient method: CRGM), is developed to overcome such weakness and accurately reproduce the fluctuations of the BLH under various atmospheric pollution conditions. Comprehensive evaluation of CRGM highlights its high performance in determining BLH from Lidar. In comparison with the existing retrieval algorithms, the CRGM potentially reduces related computational uncertainties and errors from BLH determination (strong increase of correlation coefficient from 0.44 to 0.91 and significant decrease of the root mean square error from 643 m to 142 m). Such newly developed technique is undoubtedly expected to contribute to improve the accuracy of air quality modelling and forecasting systems.

scholarly journals Aerodynamics of Boundary Layer Ingesting Fuselage Fans

2021 ◽  
pp. 1-30
Author(s):  
Alejandro Castillo Pardo ◽  
Cesare A. Hall
Keyword(s):  
Boundary Layer ◽  
Pollutant Emissions ◽  
Experimental Facility ◽  
Test Results ◽  
Free Vortex ◽  
Low Speed ◽  
Fuel Burn ◽  
Design Changes ◽  
Work Input ◽  
The Impact

Abstract Boundary Layer Ingestion (BLI) potentially offers significant reductions in fuel burn and pollutant emissions. The Propulsive Fuselage Concept features a fan at the back of the airframe that ingests the 360deg fuselage boundary layer. Consequently, the distortion at the fan face during cruise is close to radial. This paper aims to devise and test a fan design philosophy that is tuned to this inflow distortion. Initially a free-vortex fan design matched to clean inflow is presented. The effects of BLI on the aerodynamics of this fan are investigated. A series of design steps are then presented to develop the baseline fan into a new design matched to fuselage BLI inflow. Both fan designs have been tested within a low speed rig. The impact of the fan design changes on the aerodynamics and the performance with BLI are evaluated using the test results. This paper presents the successful application of a unique experimental facility for the analysis of BLI fuselage fans. It shows that it is possible to design a fan that accepts the radial distortion caused by fuselage BLI with a modified profile of work input. The new fan design was found to increase the work input by 4.9% and to improve the efficiency by 2.75% relative to a fan designed for clean flow. This new fan design has reduced loading near the hub to account for the incoming distortion, increased mid span loading and negative incidence towards the tip for tolerance to circumferential distortion off-design.

Engine Design Strategy for Boundary Layer Ingesting Propulsion Systems With Multiple Non-Symmetric Engine Inlet Conditions

2013 ◽  
Author(s):  
Jonathan C. Gladin ◽  
Brian K. Kestner ◽  
Jeff S. Schutte ◽  
Dimitri N. Mavris
Keyword(s):  
Boundary Layer ◽  
Design Strategy ◽  
Total Power ◽  
Design Strategies ◽  
Fuel Burn ◽  
Practical Strategy ◽  
Engine Design ◽  
Vehicle Aerodynamics ◽  
Inlet Conditions ◽  
The Impact

Boundary layer ingesting inlets for hybrid wing body aircraft have been investigated at some depth in recent years due to the theoretical potential for fuel burn savings. Such savings derive from the ingestion of a portion of the low momentum wake into the propulsor to reenergize the flow, thus yielding total power savings and reducing required block fuel burn. A potential concern for BLI is that traditional concepts such as “thrust” and “drag” become less clearly defined due to the interaction between the vehicle aerodynamics and the propulsive thrust achieved. One such interaction for the HWB concept is the lateral location of the inlet on the upper surface which determines the effective Reynolds number at the point of ingestion. This is an important factor in determining the amount of power savings achieved by the system, since the boundary layer, displacement, and momentum thicknesses are functions of the local chord length and airfoil shape which are all functions of the lateral location of the engine. This poses a design challenge for engine layouts with more than two engines as at least one or more of the total engines will be operating at a different set of changing inlet conditions throughout the flight envelope. As a result, the engine operating point and propulsive performance will be different between outboard and inboard engines at flight conditions with appreciable boundary layer influence including key flight conditions for engine design: takeoff, top of climb, and cruise. The optimal engine design strategy in terms of performance to address this issue is to design separate engines with similar thrust performance. This strategy has significant challenges such as requiring the manufacturing and certification of two different engines for one vehicle. A more practical strategy is to design a single engine that performs adequately at the different inlet conditions but may not achieve the full benefits of BLI. This paper presents a technique for cycle analysis which can account for the disparity between inlet conditions. This technique was used for two principal purposes: first to determine the effect of the inlet disparity on the performance of the system; second, to analyze the various design strategies that might mitigate the impact of this effect. It is shown that a single engine can be sized when considering both inboard and outboard engines simultaneously. Additionally, it is shown that there is a benefit to ingesting larger mass flows in the inboard engine for the case with large disparity between the engine inlets.

Experimental and Numerical Investigation of Inflow Turbulence on the Performance of Wind Turbine Airfoils

2013 ◽  
Author(s):  
O. Eisele ◽  
G. Pechlivanoglou ◽  
C. N. Nayeri ◽  
C. O. Paschereit
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Wind Tunnel Test ◽  
Wind Turbine Blade ◽  
Two Dimensional ◽  
Airfoil Surface ◽  
Wind Tunnel Measurements ◽  
Inflow Turbulence ◽  
The Impact

Wind turbine blade design is currently based on the combination of a plurality of airfoil sections along the rotorblade span. The two-dimensional airfoil characteristics are usually measured with wind tunnel experiments or computed by means of numerical simulation codes. The general airfoil input for the calculation of the rotorblade power characteristics as well as the subsequent aerodynamic and aeroelastic loads are based on these two-dimensional airfoil characteristics. In this paper, the effects of inflow turbulence and wind tunnel test measurement deviations are investigated and discussed, to allow considerations of such effects in the rotorblade design process. The results of CFD simulations with various turbulence models are utilized in combination with wind tunnel measurements in order to assess the impact of such discrepancies. It seems that turbulence, airfoil surface roughness and early transition effects are able to contribute significantly to the uncertainty and scattering of measurements. Various wind tunnel facilities generate different performance characteristic curves, while grid-generated turbulence is generally not included in the wind tunnel measurements during airfoil characterization. Furthermore the correlation of grid-generated wind tunnel turbulence with the atmospheric turbulence time and length scales is not easily achieved. All the aforementioned uncertainties can increase the performance scattering of current wind turbine blade designs as well as the generated aeroelastic loads. A brief assessment of the effect of such uncertainties on wind turbine performance is given at the last part of this work by means of BEM simulations on a wind turbine blade.

Current Drag From Tow and Wind Tunnel Tests of a FLNG Hull

2016 ◽  
Author(s):  
Zhenjia (Jerry) Huang ◽  
Jang Kim ◽  
Hyunchul Jang ◽  
Scott T. Slocum
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Model Test ◽  
Cfd Simulation ◽  
Wind Tunnel Test ◽  
Model Tests ◽  
Additional Contribution ◽  
Wind Tunnel Model ◽  
Tunnel Model ◽  
Current Drag

In this paper, the current drag of a barge-shaped floating liquefied natural gas (FLNG) vessel was studied. Three model tests were performed — a wind tunnel model test, a submerged double-body tow test and a surface tow test. Computational fluid dynamics (CFD) simulations were carried out to gain further insights into the test results. During testing, the tow speed was kept low to avoid surface waves. When the current heading was around the beam current direction, the transverse drag coefficient measured from the wind tunnel test was significantly lower than those of the submerged tow and surface tow tests. The submerged tow and the surface tow provided similar drag coefficients. Results presented in this paper indicated that the difference between the wind tunnel test and the tow tests was caused by the wind tunnel boundary layer effect on the incoming wind profile and formation of a recirculation zone on the upstream side of the model, with a possible additional contribution from the wind tunnel floor constraint on the flow in the wake. Such effects are not accounted for with the simple corrections based on flow velocity reduction in the wind tunnel boundary layer. When conducting future wind tunnel model tests for barge-shaped FLNG hulls, one should consider the potential under-measurement of the transverse drag. In this paper, details of the FLNG model, test setup, test quality assurance (QA), measurement and CFD simulation results are presented, as well as discussions and recommendations for model testing.

A Methodology for Quantifying Distortion Impacts Using a Modified Parallel Compressor Theory

2018 ◽  
Author(s):  
Manish Pokhrel ◽  
Jonathan Gladin ◽  
Elena Garcia ◽  
Dimitri N. Mavris
Keyword(s):  
Boundary Condition ◽  
Design Space ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Interface Plane ◽  
Design And Optimization ◽  
Fan Performance ◽  
Fuel Burn ◽  
Distributed Propulsion ◽  
The Impact

Efforts to achieve NASA’s N+2 and N+3 fuel burn goals have led to various future aircraft concepts. A commonality in all these concepts is the presence of a high degree of interaction among the various disciplines involved. A tightly integrated propulsion/airframe results in distortion in the flow field around the engine annulus. Although beneficial in terms of propulsive efficiency (due to boundary layer ingestion), the impact of distortion on fan performance and operability remains in question for these concepts. As such, rapid evaluation of the impacts of distortion during the conceptual design phase is necessary to assess various concepts. This is especially important given the expansion of the design space afforded by turbo-electric and hybrid-electric distributed propulsion concepts, in which the gas turbine generator and propulsive devices can be decoupled in space. A simple and rapid methodology to assess operability of compressors is the theory of Parallel Compressors (PC). PC theory views the compressor as two compressors in parallel, one with a uniform high Pt and the other with a uniform low Pt, both operating at the same speed and exiting to a common static pressure. The assumption of two compressors exiting at the common static pressure is not entirely true, especially when the distortion is high. In this paper, the development of a modified parallel compressor model with parametric boundary condition that can capture the impact of non-uniform inflow on fan performance is introduced and validated. Unlike classical PC model, the modified approach introduces a boundary condition dependent on the intensity of distortion (DPCP) at the Aerodynamic Interface Plane (AIP). Additionally, the concept of PC is also extended to Multi-Per Revolution (MPR) distortion. A modeling environment which follows this methodology is created in PROOSIS, an object oriented 0-D cycle code. The model was created using the “compressor” components acting in parallel and a procedure for implementing both design mode and off-design mode solutions was created using the PROOSIS toolset. The example problem was implemented to demonstrate two capabilities — i) the ability of quantifying impacts on thrust and performance of a ducted fan propulsion system, and ii) the ability of predicting loss in stability pressure ratio. The results clearly show the ability of the tool to quantify distortion related losses. The work described in this paper can be integrated to a Multi-Disciplinary Design and Optimization (MDAO) framework along with other disciplines and can be used to evaluate the viability of design space offered by novel aircraft configurations.

scholarly journals Experimental and Computational Analysis of Model–Support Interference in Low-Speed Wind-Tunnel Testing of Fuselage-Boundary-Layer Ingestion

2019 ◽  
Vol 304 ◽  
pp. 02020
Author(s):  
Biagio Della Corte ◽  
André A.V. Perpignan ◽  
Martijn van Sluis ◽  
Arvind Gangoli Rao
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Junction Flow ◽  
Tunnel Model ◽  
Aerodynamic Interaction ◽  
Support Interference ◽  
Model Support

Junction flow caused by the aerodynamic interaction between a wind-tunnel model and the support structure can largely influence the flowfield and hence the experimental results. This paper discusses a combined numerical and experimental study which was carried out to mitigate the model–support interference in a wind-tunnel test setup for the study of fuselage boundary-layer ingestion. The setup featured an axisymmetric fuselage mounted through a support beam, covered by a wing-shaped fairing. The junction flow appearing at the fuselage–fairing connection produced undesired flow distortions at the fuselage aft section, due to the formation of an horseshoe vortex structure at the fairing leading edge. Numerical and experimental analysis were performed with the aim of reducing the distortion intensity by improving the fairing design. Results show that modifying the leading-edge shape of the fairing effectively decreased the flowfield distortions. Moreover, the addition of a dummy fairing diametrically opposed to the first one was found to be beneficial due to the enhancement of the configuration symmetry.

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