High Aerodynamic Performance Research Articles

Experimental Study on the Stiffness and Shape Layout of Flapping Wing

Flapping-wing Micro Air Vehicle (FMAV) is a kind of bionic air vehicle, which looks like natural flying creatures and flies by flapping-wings only. Now, there is an upsurge of relative research about FMAV, and one focus research domain is to develop a flapping-wing with high aerodynamic performance. The wind-tunnel experiment is one of the main research manner, which can be used to test and control many parameters with high accuracy, like force, torque, flapping angle, frequency, power, etc. Based on the wind-tunnel system and inspired by birds, we mainly study the effects of stiffness and shape layout of the flapping wing, and get some conclusions. And this work may set up a good fundamental for further experiment about developing wing with high efficiency.

Electrooptical complex for terrain on-time survey

The article deals with a number of approaches to the use of electrooptical systems and unmanned aerial vehicles (UAV) to solve the tasks of live terrain surface screening, air incident spots and objects survey. The paper provides the grounds for the UAV airframe chosen structure and the design of the electrooptical complex. The light weight, high -wing monoplane airframe structure is suggested. Using the CNC production center, a UAV with high aerodynamic performance was developed. The UAV was fitted with the optoelectronic system. Structural design for the airborne and ground equipment of the survey complex was developed. The structural design comprises the forward-looking and side airborne surveillance cameras and also downward-looking cameras of visible and infrared bands to provide the day and night vision. The downward-looking cameras of visible and infrared bands, integrated into the UAV fuselage belly are used for the surface monitoring and survey. The flight test on the use of electrooptic system comprised the flight on the route and automatic return using the satellite system navigation. The test showed that navigation data correction was required. The positioning accumulative error elimination is suggested to be done via automated image registration with the contour extraction and landmark reference. The image processing results using Canny algorithm were presented. The recommendations on the algorithm practical application and speed of response are given. To solve the problem of terrain on-time surveillance and monitoring the flight routes were subjected to research. Based on the experiments performed, the recommendations were given on the electrooptic complex application and flight route plotting for the tasks of on-time search and rescue.

Entropy Generation Analysis in a Mixed-Flow Compressor with Casing Treatment

Casing treatments (CT) can effectively extend compressors flow ranges with the expense of efficiency penalty. Compressor efficiency is closely linked to loss. Only revealing the mechanisms of loss generation can design a CT with high aerodynamic performance. In the paper, a highly-loaded mixed-flow compressor with tip clearance of 0.4 mm was numerically studied at a rotational speed of 30,000 r/min to reveal the effects of axial slot casing treatment (ASCT) on the loss mechanisms in the compressor. The results showed that both isentropic efficiency and stall margin were improved significantly by the ASCT. The local entropy generation method was used to analyze the loss mechanisms and to quantify the loss distributions in the blade passage. Based on the axial distributions of entropy generation rate, for both the cases with and without ASCT, the peak entropy generation rate increased in the rotor domain and decreased in the stator domain during throttling the compressor. The peak entropy generation in rotor was mainly caused by the tip leakage flow and flow separations near the rotor leading edge for the mixed-flow compressor no matter which casing was applied. The radial distributions of entropy generation rate showed that the reduction of loss in the rotor domain from 0.4 span to the rotor casing was the major reason for the efficiency improved by ASCT. The addition of ASCT exerted two opposite effects on the losses generated in the compressor. On the one hand, the intensity of tip leakage flow was weakened by the suction effect of slots, which alleviated the mixing effect between the tip leakage flow and main flow, and thus reduced the flow losses; On the other hand, the extra losses upstream the rotor leading edge were produced due to the shear effect and to the heat transfer. The aforementioned shear effect was caused by the different velocity magnitudes and directions, and the heat transfer was caused by temperature gradient between the injected flow and the incoming flow. For case with smooth casing (SC), 61.61% of the overall loss arose from tip leakage flow and casing boundary layer. When the ASCT was applied, that decreased to 55.34%. The loss generated by tip leakage flow and casing boundary layer decreased 20.54%) relatively by ASCT.

A new methodology for preliminary design of centrifugal impellers with prewhirl

The overall trend of centrifugal compressor design is to strive for high aerodynamic performance and high flow capacity products. A new methodology is derived to implement a preliminary design for high flow capacity centrifugal impeller with and without prewhirl. First, several new non-dimensional equations connecting impeller geometric and aerodynamic parameters are derived for the maximum flow capacity. The effects of prewhirl on mass flow function, inlet diameter ratio and work coefficient are discussed, respectively. Then, based on these equations, a series of design diagrams are drawn to extract the universal rules in centrifugal impeller design with prewhirl. Some physical limits of design maps are also discussed. Finally, the throat area of impeller is discussed under prewhirl, and the matching principle between prewhirl impeller and vaned diffuser is derived and validated. The proposed method can be used to design a new centrifugal compressor, or to evaluate the design feasibility and the challenge of a given design specification.

Numerical investigation of strake profile and maximum thickness position in the ram-rotor

Numerical investigation of ram-rotors with different strake profiles and maximum thickness positions has been performed. Four types of strake profiles are modeled firstly and the results show that total pressure ratio and adiabatic efficiency of the ss-sym, ss-ps, and ss-ss schemes are improved in different degrees compared with the sym-sym scheme, in which the comprehensive performance of the ss-ss scheme is relatively optimal, and its total pressure ratio and adiabatic efficiency are increased by 26.275% and 2.554%, respectively. The results of different strake maximum thickness positions indicate that the total pressure ratio and adiabatic efficiency are gradually increasing with the backward movement of starting point of maximum thickness, and the pressure rising capacity can come to a peak value. As the ending point of maximum thickness moves backward, there both exist peak values of the total pressure ratio and adiabatic efficiency. Compared with the ss-ss scheme, the scheme that combines optimal starting and ending point positions of maximum thickness takes advantage of these two schemes to achieve a higher aerodynamic performance, with total pressure ratio and adiabatic efficiency increasing 0.182% and 1.928%, respectively. Moreover, in comparison to the original sym-sym scheme, the total pressure ratio and the adiabatic efficiency of the combination scheme are improved much by 26.50% and 4.53%.

Influence of geometric configuration on aerodynamics of streamlined bridge deck by unsteady RANS

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from 1.65x104 to 25x104. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

An Integrated Design and Optimization Approach for Radial Inflow Turbines—Part I: Automated Preliminary Design

An integrated design and optimization approach was developed for radial inflow turbines, which consists of two modules, an automated preliminary design module, and a flexible three-dimensional multidisciplinary optimization module. In this paper, the first module about the automated preliminary design approach was presented in detail and validated by the experimental data. The approach employs a genetic algorithm to explore the design space defined by the loading coefficient, flow coefficient, and rotational speed. The aim is to obtain the best design scheme with high aerodynamic performance under specified constraints and to reduce the dependency on human experiences when designing a radial inflow turbine. The validation results show that the present approach is able to get the optimal design and alleviate the dependence on the designer’s expertise under specified constraints at the preliminary design stage. Furthermore, the optimization results indicate that using the present optimization approach the total-to-static efficiency of the optimized T-100 radial inflow turbine can be increased by 1.0% under design condition and the rotor weight can be decreased by 0.35 kg (26.7%) as compared with that of the original case.

Numerical and Experimental Fluid–Structure Interaction-Study to Determine Mechanical Stresses Induced by Rotating Stall in Unshrouded Centrifugal Compressor Impellers

Unshrouded industrial centrifugal compressor impellers operate at high rotational speeds and volume flow rates. Under such conditions, the main impeller blade excitation is dominated by high frequency interaction with stationary parts, i.e., vaned diffusers or inlet guide vanes (IGVs). However, at severe part load operating conditions, sub-synchronous rotating flow phenomena (rotating stall) can occur and cause resonant blade vibration with significant dynamic (von-Mises) stress in the impeller blades. To ensure high aerodynamic performance and mechanical integrity, part load conditions must be taken into account in the aeromechanical design process via computational fluid dynamics (CFD) and finite element method (FEM) analyzes anchored by experimental verification. The experimental description and quantification of unsteady interaction between rotating stall cells and an unshrouded centrifugal compression stage in two different full scale compression units by Jenny and Bidaut (“Experimental Determination of Mechanical Stress Induced by Rotating Stall in Unshrouded Impellers of Centrifugal Compressors”, ASME J. Turbomach. 2016; 139(3):031011-031011-10) were reproduced in a scaled model test facility to enhance the understanding of the fluid–structure interaction (FSI) mechanisms and to improve design guide lines. Measurements with strain gauges and time-resolved pressure transducers on the stationary and rotating parts at different positions identified similar rotating stall patterns and induced stress levels. Rotating stall cell induced resonant blade vibration was discovered for severe off-design operating conditions and the measured induced dynamic von-Mises stress peaked at 15% of the mechanical endurance limit of the impeller material. Unsteady full annulus CFD simulations predicted the same rotating stall pressure fluctuations as the measurements. The unsteady Reynold's Averaged Navier-Stokes simulations were then used in FEM FSI analyses to predict the stress induced by rotating stall and assess the aerodynamic damping of the corresponding impeller vibration mode shape. Excellent agreement with the measurements was obtained for the stall cell pressure amplitudes at various locations. The relative difference between measured and mean predicted stress from fluid–structure interaction was 17% when resonant blade vibration occurred. The computed aerodynamic damping was 27% higher compared to the measurement.

Impact of Economic Indicators on the Integrated Design of Wind Turbine Systems

This article presents a framework to integrate and optimize the design of large-scale wind turbines. Annual energy production, load analysis, the structural design of components and the wind farm operation model are coupled to perform a system-level nonlinear optimization. As well as the commonly used design objective levelized cost of energy (LCoE), key metrics of engineering economics such as net present value (NPV), internal rate of return (IRR) and the discounted payback time (DPT) are calculated and used as design objectives, respectively. The results show that IRR and DPT have the same effect as LCoE since they all lead to minimization of the ratio of the capital expenditure to the energy production. Meanwhile, the optimization for NPV tends to maximize the margin between incomes and costs. These two types of economic metrics provide the minimal blade length and maximal blade length of an optimal blade for a target wind turbine at a given wind farm. The turbine properties with respect to the blade length and tower height are also examined. The blade obtained with economic optimization objectives has a much larger relative thickness and smaller chord distributions than that obtained for high aerodynamic performance design. Furthermore, the use of cost control objectives in optimization is crucial in improving the economic efficiency of wind turbines and sacrificing some aerodynamic performance can bring significant reductions in design loads and turbine costs.

Design of Spray-dried Porous Particles for Sugar-based Dry Powder Inhaler Formulation

For efficient and deeper drug delivery into the lungs via dry powder inhalers (DPIs), we designed porous spray-dried particles (SDPs) containing anti-tuberculosis drugs and sugar-based excipients. The SDPs were prepared by spray-drying ethanol solutions containing isoniazid and/or rifampicin and sucrose, maltose, or highly branched cyclic dextrin (HBCD). Solid-state fluorescence emission spectroscopy showed that 1-naphthoic acid (1-NPA), a model drug, was dispersed in a molecular dispersion/solid solution, suggesting high potential of HBCD as an excipient in DPIs. 1-NPA was dispersed not only as active pharmaceutical ingredient (API) molecules with HBCD, but also as fine crystals. Morphological examination showed that the fine particles of HBCD/anti-tuberculosis drugs were porous, indicating high aerodynamic performance. Isoniazid and rifampicin could also be incorporated into the HBCD matrix. HBCD formulations exhibited higher released doses and fine-particle fractions than sucrose and maltose formulations, and could incorporate both hydrophilic and hydrophobic drugs.

Aerodynamic Numerical Analysis of the Low Reynolds Number Diamond Joined-Wing Configuration Unmanned Aerial Vehicle

Aerodynamic numerical simulation of low Reynolds number long-endurance Diamond Joined-Wing configuration unmanned aerial vehicle was performed. First, low Reynolds number aerodynamic characteristics of a typical wing are numerically simulated by solving the Reynolds averaged Navier–Stokes (RANS) equations based on the structural grid technology and the k–kL–ω transition model. To prove the accuracy of this method, experimental data and numerical simulation results were compared. Second, the performance of low Reynolds number Diamond Joined-Wing configuration UAV (unmanned aerial vehicle) aerodynamic characteristics and control surfaces was studied by numerical simulation and theoretical analysis. The analysis of the interference between the Frt-wing (front wing) and the Aft-wing (after wing) of the Diamond Joined-Wing configuration UAV and the reason for the change in the pitching moment in the lateral-directional motion is carried out. The results show that the Diamond Joined-Wing configuration UAV has a typical low Reynolds number surface flow characteristics, Frt-wing and Aft-wing flow interference are relatively minor at a small angle of attack, which has a high basic aerodynamic performance in addition to good stall characteristics, with longitudinal and lateral-directional static stability. The performance of control surfaces and flaps is higher to meet the design requirements. Finally, the accuracy of the numerical simulation results was verified by vehicle aerodynamic testing.

Design and high speed aerodynamic performance analysis of vortex lift waverider with a wide-speed range

According to the geometrical relationships of osculating cone waveriders, two kinds of design methods for the constant swept waverider are discussed in the current study, and both of them own more flexible design curves. The correctness and effectiveness of the proposed approaches has been verified by means of the CFD approach. The design Mach numbers of the cuspidal waverider and the general osculating cone waverider with the same volumetric efficiency of the delta-winged waverider have been determined by writing a program for calculating the volumetric efficiencies of waveriders. Furthermore, the high speed aerodynamic performance advantages of the cuspidal and delta-winged waveriders have been analyzed in detail, in comparison with the high speed aerodynamic performance of the general osculating cone waverider. The obtained results show that compared with the general osculating cone waverider, the cuspidal waverider has better high speed aerodynamic performance under any flight condition in the high speed range, while the high speed aerodynamic performance of the delta-winged waverider is worse. In addition, at the high flight Mach number, the cuspidal waverider shows the significant non-linear behavior of the vortex generated lift, while the delta-winged waverider and the general osculating cone waverider do not have this property.

Effect of corrugated skins on the aerodynamic performance of the cambered airfoils

PurposeThis paper aims to study the effect of corrugated skins on the aerodynamic performance of the cambered NACA 0012 airfoils at different corrugations parameters, maximum cambers, Reynolds numbers and maximum camber locations.Design/methodology/approachIn this work, numerical approach is concerned, and results are obtained based on the finite volume approach. To characterize the effect of corrugated skins, the NACA 0012-corrugated airfoil section is chosen as the base airfoil, and different cambered corrugated airfoil sections are obtained by inclusion the camber to the base airfoil. In this research, the corrugation shape is a sinusoidal wave and corrugated skins are in the aft 30 per cent of airfoil chord. To investigate the effect of corrugations on the cambered sections, the drag coefficient and averaged lift curve slope for the corrugated airfoils are compared to those of the corresponding smooth sections.FindingsResults indicate that the effect of increase in the maximum camber and also Reynolds number on the relative zero-incidence drag coefficient is of little importance at low corrugation amplitudes, whereas at high corrugation, amplitude results in different behaviors. It is found that as the maximum camber increases, the deterioration in the relative curve slope introduced by corrugated skins is reduced, and reduction in this deterioration is significant for high corrugation amplitudes airfoils. It is shown that an increase in the maximum camber location has nearly no effect on the relative zero-incidence drag coefficient and also relative lift curve slope.Originality/valueThe outcome of the present research provides the clues for better understanding of the effect of different corrugations parameters on the aerodynamic performance of the unmanned air vehicles to have as high aerodynamic performance as possible in different mission profiles of such vehicles.

ON THE IMPACT OF FLIGHT SAFETY CERTIFICATION REQUIREMENTS ON THE AERODYNAMIC EFFICIENCY OF COMMERCIAL AIRPLANES

The article considers the issue of aerodynamics efficiency implementation taking into account certification requirements for flight safety. Aerodynamics efficiency means high aerodynamic performance (depending on the airplane size), aerodynamic performance in cruise flight, high aerodynamic performance at takeoff, as well as lift performance at landing. The author estimated the impact on aerodynamics efficiency of both the requirements for aerodynamics performance and requirements for aircraft systems, noncompliance with which may result in significant change of expected operating conditions. It was shown that the use of supercritical wing profiles may result in flight mode limitations due to failure of the required buffeting capacities. It does not allow engaging all the advantages of aerodynamics layout and requires special design solutions to prevent such cases. There were reviewed certification requirements for flight level pressure altitude accuracy and icing conditions warning sysytem. The research presented the methods of aerodynamic efficiency increase by meeting the requirements for reduced vertical separation minima flights and in icing conditions, including requirements for air data probes. Reduced vertical separation minima flight requirements are met by means of efficient air data probes location. Theoretical methods of flow calculation determine areas on the airplane skin surface where static probes minimize errors depending on angle-of-attack and sideslip. It was shown that if certification requirements are not met and in case of flight out of reduced vertical separation minima area, aerodynamics efficiency is significantly reduced and fuel consumption can be increased by 10% and higher. Suggested approaches implementation allows increasing commercial airplanes competitiveness.

PARSIFAL Project: a Breakthrough Innovation in Air Transport

PARSIFAL is a Horizon 2020 project, started on May 2017, with the aim to design an innovative aircraft, based on the “PrandtlPlane” (PrP) configuration, for the civil aviation of the future. The PrP configuration allows us to reduce the fuel consumption and the external noise, especially during low speed flight. The high aerodynamic performances are used to limit the span to 36m, compliant with ICAO Aerodrome Reference Code C standard, and to extend the payload capacity to 250–350 passengers without significant penalties of aerodynamic efficiency. The paper presents the overall characteristics of this innovative aircraft and how the PrP configuration could allow to improve the civil air transport of the future, as far as aircraft manufacturers, airports, airlines and passengers are concerned; in particular, some aspects of the architectural solutions and the aerodynamic design and optimization are underlined in subsonic and transonic regimes. Some details are given here on the fuselage design and the lifting system.

Redesign of a Compressor Stage for a High-Performance Electric Supercharger in a Heavily Downsized Engine

Engine downsizing is a modern solution for the reduction of CO2 emissions from internal combustion engines. This technology has been gaining increasing attention from industry. In order to enable a downsized engine to operate properly at low speed conditions, it is essential to have a compressor stage with very good surge margin. The ported shroud, also known as the casing treatment, is a conventional way used in turbochargers to widen the working range. However, the ported shroud works effectively only at pressure ratios higher than 3:1. At lower pressure ratio, its advantages for surge margin enhancements are very limited. The variable inlet guide vanes are also a solution to this problem. By adjusting the setting angles of variable inlet guide vanes, it is possible to shift the compressor map toward the smaller flow rates. However, this would also undermine the stage efficiency, require extra space for installing the inlet guide vanes, and add costs. The best solution is therefore to improve the design of impeller blade itself to attain high aerodynamic performances and wide operating ranges. This paper reports a recent study of using inverse design method for the redesign of a centrifugal compressor stage used in an electric supercharger, including the impeller blade and volute. The main requirements were to substantially increase the stable operating range of the compressor in order to meet the demands of the downsized engine. The three-dimensional (3D) inverse design method was used to optimize the impeller geometry and achieve higher efficiency and stable operating range. The predicted performance map shows great advantages when compared with the existing design. To validate the computational fluid dynamics (CFD) results, this new compressor stage has also been prototyped and tested. It will be shown that the CFD predictions have very good agreement with experiments and the redesigned compressor stage has improved the pressure ratio, aerodynamic efficiency, choke, and surge margins considerably.

A computational study of the effects of the radius ratio and attachment angle on the performance of a Darrieus-Savonius combined wind turbine

Small wind turbines as energy saving devices can be applied in many fields and are in great demand. There are two common types of rotors in wind turbines. Savonius rotors require a low torque for starting, but their efficiency is low. Darrieus rotors have high efficiency, but they are difficult to start up. A Darrieus-Savonius combined rotor aiming at a high aerodynamic performance with a low start-up requirement has drawn the attention of many researchers. The radius ratio and the attachment angle between the two types of rotors are important factors, but have not been studied systematically. In this paper, the effects of these two parameters on the efficiency and starting performance are investigated by a computational fluid dynamics approach. Steady simulations solving the Reynolds averaged Navier-Stokes equations with realizable k-ε turbulence model were conducted to obtain the static torque. Unsteady simulations were performed to calculate the power coefficient of the combined rotor at different tip-speed-ratios. A number of configurations were tested and the optimum attachment angle and radius ratio for the combined rotor was obtained with a maximum power coefficient of 0.363 and required starting torque below 0.1 Nm at a wind speed of 2 m/s.

Wind Turbine Airfoil Optimal Design With High Whole Aerodynamic Performance Considering Continuous Angle of Attack

Wind Turbine Airfoil Optimal Design With High Whole Aerodynamic Performance Considering Continuous Angle of Attack

Optimal design of impeller for centrifugal compressor under the influence of one-way fluid-structure interaction

In this study, a method for optimal design of impeller for centrifugal compressor under the influence of Fluid-structure interaction (FSI) and Response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS Multi-physics with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 45 design points were planned by Central composite design (CCD) method, which is one of the Design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design xplorer (DX). Through the optimization, structural safety and aerodynamic performance of centrifugal compressor were improved.

Improving the aerodynamic performance of Vila-Real Bridge deck-section

The susceptibility of bridge decks to vortex induced oscillations can be addressed through wind-tunnel testing. This paper considers the case of the Vila-Real Bridge, in the north of Portugal, which has the highest deck above ground (230m), among concrete-deck bridges cable-stayed in the central plane. It has a single-cell rectangular box girder with a wide top flange supported by regularly spaced inclined struts. Aeroelastic studies of this precise type of deck seem nonexistent in the literature.Results of sectional model tests are presented for a selection of three distinct angles of attack and three deck configurations, including a solution, alternative to the usual mitigation measures, that solved the susceptibility to vortex induced vibration of the deck and that has no relevant additional design or building costs.With the proposed approach, bridge designers may be able to relegate the use of sections with high aerodynamic performance – but that can be more costly, pose a greater challenge in the construction, or require more time to completion – and the use of mitigation measures, to cases in which they prove to be absolutely necessary.