A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of fr...A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of freedom of the Trailing Edge Flap(TEF)is analyzed by employing an inverse nested overset grid method.Simulation of non-rotational and rotational modes of blade motion are carried out to investigate the formation and development of TEF shedding vortex with high-frequency deflection of TEF.Moreover,the mechanism of TEF deflection interference with blade tip vortex and overall rotor aerodynamics is also explored.In nonrotational mode,two bundles of vortices form at the gap ends of TEF and the main blade and merge into a single TEF vortex.Dynamic deflection of the TEF significantly interferes with the blade tip vortex.The position of the blade tip vortex consistently changes,and its frequency is directly related to the frequency of TEF deflection.In rotational mode,the tip vortex forms a helical structure.The end vortices at the gap sides co-swirl and subsequently merge into the concentrated beam of tip vortices,causing fluctuations in the vorticity and axial position of the tip vortex under the rotor.This research concludes with the investigation on suppression of Blade Vortex Interaction(BVI),showing an increase in miss distance and reduction in the vorticity of tip vortex through TEF phase control at a particular control frequency.Through this mechanism,a designed TEF deflection law increases the miss distance by 34.7%and reduces vorticity by 11.9%at the target position,demonstrating the effectiveness of AFC in mitigating BVI.展开更多
Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)ai...Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)airfoil,the DU06-W200.As noise reduction benefits of these mechanisms are already well-established,this study focuses on their impact on airfoil and VAWT performance.A saw-tooth geometry was chosen based on VAWT specifications and existing research,followed by a detailed assessment through wind tunnel tests using a newly developed aerodynamic balance.For a broad spectrum of attack angles and Reynolds numbers,lift,drag,and pitching moments were carefully measured.The results show that TES enhance the lift-to-drag ratio,especially in stalled conditions,and postpone stall at negative angles,expanding the effective performance range.A notable increase in pitching moment also is also observed,relevant for blade-strut joint design.Additionally,the impact on turbine performance was estimated using an analytical model,demonstrating excellent accuracy when compared against previous experimental results.TES offer a modest 2%improve-ment in peak performance,though they slightly narrow the optimal tip-speed ratio zone.Despite this,the potential noise reduction and performance gains make TES a valuable addition to VAWT designs,especially in urban settings.展开更多
The seamless trailing edge morphing flap is investigated using a high-fidelity steady-state aerodynamic shape optimization to determine its optimum configuration for different flight conditions,including climb,cruise,...The seamless trailing edge morphing flap is investigated using a high-fidelity steady-state aerodynamic shape optimization to determine its optimum configuration for different flight conditions,including climb,cruise,and gliding descent.A comparative study is also conducted between a wing equipped with morphing flap and a wing with conventional hinged flap.The optimization is performed by specifying a certain objective function and the flight performance goal for each flight condition.Increasing the climb rate,extending the flight range and endurance in cruise,and decreasing the descend rate,are the flight performance goals covered in this study.Various optimum configurations were found for the morphing wing by determining the optimum morphing flap deflection for each flight condition,based on its objective function,each of which performed better than that of the baseline wing.It was shown that by using optimum configuration for the morphing wing in climb condition,the required power could be reduced by up to 3.8%and climb rate increases by 6.13%.The comparative study also revealed that the morphing wing enhances aerodynamic efficiency by up to 17.8%and extends the laminar flow.Finally,the optimum configuration for the gliding descent brought about a 43%reduction in the descent rate.展开更多
Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in t...Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in the dimensional design of serration height 2 h,wavelengthλand flap angleϕare yet to be dealt with in a satisfactory manner.To address the problem,a general model for simulating the effects of serrations on the hydrodynamic and aeroacoustic performance is proposed due to its ease of use and relatively low requirements for user input.The solid serrations are replicated by momentum sources calculated by its aerodynamic forces.Then,a case relevant to wind turbine airfoil is examined,a hybrid improved delay detached eddy simulation(IDDES)method coupled with FW-H integration is deployed to obtain the flow features and far-field sound pressure level.It is found that the modeling method could reproduce the flow field and noise as serrated airfoil.展开更多
SARISTU was a big cooperation project granted by the European Commission,7th Framework Programme,carried out between 2011 and 2015.It dealt with smart aeronautic structures,both morphing and sensored;its main target w...SARISTU was a big cooperation project granted by the European Commission,7th Framework Programme,carried out between 2011 and 2015.It dealt with smart aeronautic structures,both morphing and sensored;its main target was to demonstrate the feasibility of designing,manufacturing and operating in representative environment,instrumented structures.Till now,it represents the major effort carried out within the European Union on the development of adaptive architectures for air systems.Inside that big activity,the realization of an Adaptive Trailing Edge Device(ATED)for wing camber adaptations aimed at compensating the weight reduction following the fuel consumption during cruise was addressed.It made the core of investigations target variable geometry aircraft components together with two other analyses concerning the development of shape-changing winglet and droop nose.ATED activities were conducted by the Italian Aerospace Research Centre(CIRA)in tight cooperation with the University of Napoli,"Federico II",who coordinated a group of 12 different partners from 8 different nations(France,Germany,Greece,the Netherlands,Israel,Spain,Turkey,and Italy).In this paper,an integral synthesis of that work is reported,with a focus on the definition and realization of the components of the presented device.The publication is in fact meant as the first part of a series that is aimed at overviewing the whole adaptive trailing edge development,till wind tunnel tests execution.Such a concise report is a critical and harmonized review of what have been performed by many colleagues spread all over Europe,all of which are duly recalled in the reported bibliography where the reader may access more detailed information and descriptions.In detail,the paper starts with a general introduction of the concept and its aims,to move to the specs definition immediately after.Then,it deals with a short but comprehensive description of the main ATED components:structural skeleton,skin,actuation and sensing systems.It is worth remarking that the paragraph dedicated to the body frame includes some discussion about aeroelastic assessment and manufacture,seen as complementation for a complete assessment of the design constraints.展开更多
This article deals with the effects of a blowing ratio measured with narrowband liquid crystal in transonic experiments on the heat transfer characteristics of trailing edge cutback. The experimental results are compa...This article deals with the effects of a blowing ratio measured with narrowband liquid crystal in transonic experiments on the heat transfer characteristics of trailing edge cutback. The experimental results are compared and contrasted in terms of available data for traditional experiments with thermocouples. It is concluded that the blowing ratio exerts rather significant effects on film cooling effectiveness distribution of the rib center line. As the blowing ratio decreases, similar to the cooling effectiveness distribution curve of the slot center line, that of the rib center line makes a clockwise rotation about the end. When the blowing ratio increases, the regular film cooling effectiveness curve of the surface becomes rather smooth. On the whole measuring surface, the most intensive heat transfer occurs at the extended borderline of the slot and the rib, neither at the rib center line nor at the slot center line. The experimental results of cooling effectiveness measured with thermocouples are lower than those with liquid crystal. In addition, the transient experiments using narrowband liquid crystal can eliminate the higher errors of Nusselt numbers in measurements with thermocouples at the slot outlet.展开更多
The morphing trailing edge based compliant mechanism is a developing technology which can increase lift-drag ratio for variable flight modes by bending down the trailing edge.Composite material design is integrated in...The morphing trailing edge based compliant mechanism is a developing technology which can increase lift-drag ratio for variable flight modes by bending down the trailing edge.Composite material design is integrated into topology optimization for the morphing trailing edge based compliant mechanism in the paper.A two-step optimization strategy is established to solve the integrated design problem.Initially,lamination parameters are introduced and viewed as a bridge between structure stiffness and fiber angles for composite material.Design variables include the lamination parameters and element density.The least-squares between actual and desired displacements at output points along trailing edge is adopted to evaluate the deformed capability of the trailing edge.An integrated optimization model for the composite morphing trailing edge is established with the volume constraints.The optimal topologic shape and lamination parameters are initially obtained.Subsequently,a least-squares optimization between fiber angles and the optimal lamination parameters is implemented to obtain optimal fiber angles.Finally,morphing capability of composites trailing edge based compliant mechanism is investigated by simulation and experiments.The results indicate the composites trailing edge based compliant mechanism can approximately bend down 8 degrees and satisfies the design requirement.展开更多
This paper presented an experimental investigation the effects of the trailing edge cooling on the aerodynamic performance. The experiments were conducted on the low-speed linear cascade tunnel at Northwestern Polytec...This paper presented an experimental investigation the effects of the trailing edge cooling on the aerodynamic performance. The experiments were conducted on the low-speed linear cascade tunnel at Northwestern Polytechnical University. The external aerodynamic characteristics in the 40 percent chord downstream of exit plane were measured using five-hole probe with the different ejection rates. The results showed that the total pressure loss coefficient at the middle spanwise plane increased at first and then it has a decreasing tendency with the increase of ejection ratio. The trailing edge cooling would influence the structure of the turbine cascade outlet flow field. When the ejection rate was 3%,the loss area near the blade endwall would become stronger,but it would become weaker with the 6% ejection ratio. On the whole,the trailing edge cooling had more influence on the profile loss than on the secondary loss.展开更多
Morphing wing has attracted many research attention and effort in aircraft technology development because of its advantage in lift to draft ratio and flight performance.Morphing wing technology combines the lift and c...Morphing wing has attracted many research attention and effort in aircraft technology development because of its advantage in lift to draft ratio and flight performance.Morphing wing technology combines the lift and control surfaces into a seamless wing and integrates the primary structure together with the internal control system.It makes use of the wing aeroelastic deformation induced by the control surface to gain direct force control through desirable redistribution of aerodynamic forces.However some unknown mechanical parameters of the control system and complexity of the integrated structure become a main challenge for dynamic modeling of morphing wing.To solve the problem,a method of test data based modal sensitivity analysis is presented to improve the morphing wing FE model by evaluating the unknown parameters and identifying the modeling boundary conditions.An innovative seamless morphing wing with the structure integrated with a flexible trailing edge control system is presented for the investigation.An experimental model of actuation system driven by a servo motor for the morphing wing is designed and established.By performing a vibration test and the proposed modal sensitivity analysis,the unknown torsional stiffness of the servo motor and the boundary condition of the actuation mechanism model is identified and evaluated.Comparing with the test data,the average error of the first four modal frequency of the improved FE model is reduced significantly to less than 4%.To further investigate the morphing wing modeling,a wing box and then a whole morphing wing model including the skin and integrated with the trailing edge actuation system are established and tested.By using the proposed method,the FE model is improved by relaxing the constraint between the skin and actuation mechanism.The results show that the average error of the first three modal frequency of the improved FE model is reduced to less than 6%.The research results demonstrate that the presented seamless morphing wing integrated with a flexible trailing edge control surface can improve aerodynamic characteristics.By using the test data based modal sensitivity analysis method,the unknown parameter and boundary condition of the actuation model can be determined to improve the FE model.The problem in dynamic modeling of high accuracy for a morphing wing can be solved in an effective manner.展开更多
The turbulent wakes behind trailing edge are analyzed for understanding of the flow mechanisms responsible for the generation of trailing edge noise. The TILS （turbulence integral length scale） of the turbulent wake...The turbulent wakes behind trailing edge are analyzed for understanding of the flow mechanisms responsible for the generation of trailing edge noise. The TILS （turbulence integral length scale） of the turbulent wake of hydrofoil with blunt trailing edge is calculated from TR-PIV （time-resolved particle image velocimetry） data. The temporal auto-correlation method based on Taylor hypothesis and spatial correlation method are used to get the TILS information of the turbulent wake of hydrofoil, respectively The comparison of results by two methods indicates that the spatial correlation method is independent on Taylor hypothesis and suitable to strong turbulence and non-isotropic turbulence.展开更多
This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal D...This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal Decomposition(POD) method.The Delayed Detached Eddy Simulation(DDES) turbulence model was used to obtain detailed information about the velocity and temperature field for the POD method.To verify the accuracy of the numerical results,fast-response Pressure Sensitive Paint(PSP) and high-frequency Particle Image Velocimetry(PIV) experiments were also conducted,and the results achieved good agreement.As the blowing ratio increases,the effectiveness η of the cutback's film cooling exhibits a "increase-decrease-increase" trend,with η reaching its minimum point at around a blowing ratio(M_(slot)) of 0.75.Three kinds of coherent vortex structures are observed in the flow field at different blowing ratios.According to the analysis using the POD method,the first and second order modes of a Karman-like vortex street are observed in the vicinity of the wall at various blowing ratios.This coherent flow structure is directly related to the mixing intensity between the mainstream gas and the coolant.At M_(slot)=0.75,these modes had the highest energy ratio and formed a stable dominant coherent structure in the flow field.As the blowing ratio increases,the main characteristic modes in the temperature field gradually change,and the mode appears crescent-shaped when the effectiveness of film cooling is at its lowest.This paper combines the vortex structure of the flow field to explain the flow field feature distribution at the lowest effectiveness point η and analyzes its impact on the film cooling characteristics of the protected surface.展开更多
Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions i...Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.展开更多
This paper discussed a noise reduction effect of airfoil and small-scale model rotor by using attached serration trailing edge in the wind tunnel test condition. In order to analyze the changes in the performance due ...This paper discussed a noise reduction effect of airfoil and small-scale model rotor by using attached serration trailing edge in the wind tunnel test condition. In order to analyze the changes in the performance due to the inclusion of a serrated trailing edge designed to reduce noise, a 10 k W wind turbine rotor was equipped with a thin serrated trailing edge. The restrictive condition for the serrated trailing edge equipped with the using of a 2D airfoil was examined through the using of a wind tunnel experiment after studying existing restrictive condition and analyzing prior research on serrated trailing edges. The aerodynamic performance and noise reduction effect of a small-scale model were investigated with the using of a serrated trailing edge. Moreover, the noise levels from the experiment were considered that the noise prediction method could be used for a full-scale rotor. It is confirmed that noise reduction effect is compared with wind tunnel test data at the 2D airfoil and model rotor condition.展开更多
An experimental study was conducted to quantify the flow characteristics of the wall jets pertinent to trailing edge cooling of turbine blades.A high-resolution stereoscopic particle image velocimetry(PIV)system was u...An experimental study was conducted to quantify the flow characteristics of the wall jets pertinent to trailing edge cooling of turbine blades.A high-resolution stereoscopic particle image velocimetry(PIV)system was used to conduct detailed flow field measurements to quantitatively visualize the evolution of the unsteady vortices and turbulent flow structures in the cooling wall jet streams and to quantify the dynamic mixing process between the cooling jet stream and the mainstream flows.The detailed flow field measurements were correlated with the adiabatic cooling effectiveness maps measured by using pressure sensitive paint(PSP)technique to elucidate underlying physics in order to explore/optimize design paradigms for improved cooling effectiveness to protect the critical portions of turbine blades from harsh environments.展开更多
Unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance....Unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance. The turbine stage used in this paper is composed of a vane section and a rotor one which are both near the root section of a transonic high-load turbine stage. The Mach number is 0.94 at vane outlet, and the relative Mach number is above 1.10 at rotor outlet. Various positions and oblique angles of film cooling holes were investigated in this research. Results show that the cooling efficiency on the blade surface of rotor near leading edge is significantly affected by vane trailing edge outer-extending shockwave in some cases. In the cases that film holes are close to leading edge, cooling performance suffers more from the sweeping vane trailing edge outer-extending shockwave.In addition, coolant flow ejected from oblique film holes is harder to separate from the blade surface of rotor, and can cover more blade area even under the effects of sweeping vane trailing edge shockwave. As a result, oblique film holes can provide better film cooling performance than vertical film holes do near the leading edge on turbine blade which is swept by shockwaves.展开更多
The characteristics of flow past beveled trailing edges attached to flat plates have been investigated numerically and experimentally. The test models used in the present study were two 2D blunt-faced flat plates havi...The characteristics of flow past beveled trailing edges attached to flat plates have been investigated numerically and experimentally. The test models used in the present study were two 2D blunt-faced flat plates having asymmetric beveled trailing edges of angles 27° and 60°. The numerical simulation results display an asymmetric wake behind the 27° beveled trailing edge and von karmen street vortices behind the 60° beveled trailing edge. The flow visualization using cavitation technique showed the same observations of the numerical simulation. Therefore, it is obvious that the trailing edge geometry has a pronounced effect on the wake development and vortex shedding. Also, it is concluded that the cavitation phenomenon can be used as a visualization technique at high flow velocities.展开更多
The aerothermal performance of a trailing edge （TE） internal cooling system of a high pressure gas turbine blade was evaluated under stationary and rotating conditions. The investigated geometry consists of a 30：1 ...The aerothermal performance of a trailing edge （TE） internal cooling system of a high pressure gas turbine blade was evaluated under stationary and rotating conditions. The investigated geometry consists of a 30：1 scaled model reproducing a typical wedge shaped discharge duct with one row of enlarged pedestals. The airflow pattern inside the device simulates a highly loaded rotor blade cooling scheme with a 90 [deg] turning flow from the radial hub inlet to the tangential TE outlet. Two different tip configurations were tested, the first one with a completely closed section, the second one with a 5 holes outlet surfaces discharging at ambient pressure. In order to assess rotation effects, a rotating test rig, composed of a rotating ann holding both the PMMA TE model and the instru mentation, was purposely developed and manufactured. A thin Inconel heating foil and wide band Thermochromic Liquid Crystals are used to perform steady state heat transfer measurements on the blade pres sure side. A rotary joint ensures the pneumatic connection between the blower and the rotating apparatus; more over several slip rings are used for both instrumentation power supply and thermocouple connection. A parallel CFD analysis involving steadystate RANS modeling was conducted to allow an insight of the flow field inside the redirecting channel and the interpedestal ducts to better interpret the developing vortical structures. LowReynolds grid clustering permits to integrate up to the wall both the momentum and the thermal boundary layer. Calculations were performed by means of an inhouse developed pressure based solver exploiting the kco SST turbulence model implemented in the framework of the opensource finite volume discretization toolbox OpenFOAM~. Analyzed flow conditions correspond to Reynolds number of 20000 in the hub inlet section and angular speed varies to obtain rotation numbers in the range from 0 to 0.3. The orientation of the rotation axis is orthogonal to the heated surface as to resemble a 90 [deg] blade metal angle. Results are reported in terms of de tailed heat transfer coefficient 2D maps on the suction side surface as well as spanwise profiles inside the pedestal ducts.展开更多
Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature;as a consequence,advanced cooling techniques must be applied to protect from thermal stresses,oxidation and corrosion the ...Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature;as a consequence,advanced cooling techniques must be applied to protect from thermal stresses,oxidation and corrosion the components located in the high pressure stages,such as the blade trailing edge.A suitable design of the cooling system for the trailing edge has to cope with geometric constraints and aerodynamic demands;state-of-the-art of cooling concepts often use film cooling on blade pressure side:the air taken from last compressor stages is ejected through discrete holes or slots to provide a cold layer between hot mainstream and the blade surface.With the goal of ensuring a satisfactory lifetime of blades,the design of efficient trailing edge film cooling schemes and,moreover,the possibility to check carefully their behavior,are hence necessary to guarantee an appropriate metal temperature distribution.For this purpose an experimental survey was carried out to investigate the film covering performance of different pressure side trailing edge cooling systems for turbine blades.The experimental test section consists of a scaled-up trailing edge model installed in an open loop suction type test rig.Measurements of adiabatic effectiveness distributions were carried out on three trailing edge cooling system configurations.The baseline geometry is composed by inclined slots separated by elongated pedestals;the second geometry shares the same cutback configuration,with an additional row of circular film cooling holes located upstream;the third model is equipped with three rows of in-line film cooling holes.Experiments have been performed at nearly ambient conditions imposing several blowing ratio values and using carbon dioxide as coolant in order to reproduce a density ratio close to the engine conditions(DR¼1.52).To extend the validity of the survey a comparison between adiabatic effectiveness measurements and a prediction by correlative approach was performed to compare the experimental results with 1D methodologies.展开更多
This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved b...This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness(TET).The solidity of the LPT cascade blade can be reduced by about12.5% through increasing the TET of the blade without a significant drop in energy efficiency.For the low solidity LPT cascade,increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by1.86% for Reynolds number(Re) of 25,000 and freestream turbulence intensities(FSTT) of 2.35%.The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented.The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.展开更多
The flow around two plates having asymmetric beveled trailing edge placed side-by-side in a uniform stream were investigated both numerically and experimentally. Two plates with spacing ratio of 1.0 and beveled traili...The flow around two plates having asymmetric beveled trailing edge placed side-by-side in a uniform stream were investigated both numerically and experimentally. Two plates with spacing ratio of 1.0 and beveled trailing edge of angle 20° were tested at Reynolds numbers equal to 3.97×10^4. The numerical simulation results displayed that the flow separates on one plate beveled trailing edge surface. The vortex formation and shedding from this plate led to deflecting the flow toward the other plate and consequently the wake behind the plates showed an asymmetric development. The photographs obtained from the flow visualization confirmed the numerical results concerning the flow separation and vortex formation. It was also found that the computed pressure distribution on the two plate surfaces was different, particularly on the beveled trailing edge surfaces and on the fiat sides.展开更多
基金supported by the National Natural Science Foundation of China(No.11972190)。
文摘A robust Reynolds-Averaged Navier-Stokes(RANS)based solver is established to predict the complex unsteady aerodynamic characteristics of the Active Flap Control(AFC)rotor.The complex motion with multiple degrees of freedom of the Trailing Edge Flap(TEF)is analyzed by employing an inverse nested overset grid method.Simulation of non-rotational and rotational modes of blade motion are carried out to investigate the formation and development of TEF shedding vortex with high-frequency deflection of TEF.Moreover,the mechanism of TEF deflection interference with blade tip vortex and overall rotor aerodynamics is also explored.In nonrotational mode,two bundles of vortices form at the gap ends of TEF and the main blade and merge into a single TEF vortex.Dynamic deflection of the TEF significantly interferes with the blade tip vortex.The position of the blade tip vortex consistently changes,and its frequency is directly related to the frequency of TEF deflection.In rotational mode,the tip vortex forms a helical structure.The end vortices at the gap sides co-swirl and subsequently merge into the concentrated beam of tip vortices,causing fluctuations in the vorticity and axial position of the tip vortex under the rotor.This research concludes with the investigation on suppression of Blade Vortex Interaction(BVI),showing an increase in miss distance and reduction in the vorticity of tip vortex through TEF phase control at a particular control frequency.Through this mechanism,a designed TEF deflection law increases the miss distance by 34.7%and reduces vorticity by 11.9%at the target position,demonstrating the effectiveness of AFC in mitigating BVI.
基金The authors wish to thank the financial support of the Spanish Ministry of Science,Innovation and Universities in reference to the Project:Efficiency improvement and noise reduction of a vertical axis wind turbine for urban environments(MERTURB)-Ref.MCINN-22-TED2021-131307B-100.
文摘Biomimetics has recently emerged as an interesting approach to enhance renewable energy technologies.In this work,bioinspired Trailing Edge Serrations(TES)were evaluated on a typical Vertical Axis Wind Turbine(VAWT)airfoil,the DU06-W200.As noise reduction benefits of these mechanisms are already well-established,this study focuses on their impact on airfoil and VAWT performance.A saw-tooth geometry was chosen based on VAWT specifications and existing research,followed by a detailed assessment through wind tunnel tests using a newly developed aerodynamic balance.For a broad spectrum of attack angles and Reynolds numbers,lift,drag,and pitching moments were carefully measured.The results show that TES enhance the lift-to-drag ratio,especially in stalled conditions,and postpone stall at negative angles,expanding the effective performance range.A notable increase in pitching moment also is also observed,relevant for blade-strut joint design.Additionally,the impact on turbine performance was estimated using an analytical model,demonstrating excellent accuracy when compared against previous experimental results.TES offer a modest 2%improve-ment in peak performance,though they slightly narrow the optimal tip-speed ratio zone.Despite this,the potential noise reduction and performance gains make TES a valuable addition to VAWT designs,especially in urban settings.
基金the Hydra Technologies team in Mexicothe CREATEUTILI Program for their financial support。
文摘The seamless trailing edge morphing flap is investigated using a high-fidelity steady-state aerodynamic shape optimization to determine its optimum configuration for different flight conditions,including climb,cruise,and gliding descent.A comparative study is also conducted between a wing equipped with morphing flap and a wing with conventional hinged flap.The optimization is performed by specifying a certain objective function and the flight performance goal for each flight condition.Increasing the climb rate,extending the flight range and endurance in cruise,and decreasing the descend rate,are the flight performance goals covered in this study.Various optimum configurations were found for the morphing wing by determining the optimum morphing flap deflection for each flight condition,based on its objective function,each of which performed better than that of the baseline wing.It was shown that by using optimum configuration for the morphing wing in climb condition,the required power could be reduced by up to 3.8%and climb rate increases by 6.13%.The comparative study also revealed that the morphing wing enhances aerodynamic efficiency by up to 17.8%and extends the laminar flow.Finally,the optimum configuration for the gliding descent brought about a 43%reduction in the descent rate.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51736008)“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21050303).
文摘Trailing edge serrations(TESs)are capable of noticeably suppressing the turbulent trailing edge noise induced by rotating wind turbine blades and become an integral part of a blade.However,the challenges involved in the dimensional design of serration height 2 h,wavelengthλand flap angleϕare yet to be dealt with in a satisfactory manner.To address the problem,a general model for simulating the effects of serrations on the hydrodynamic and aeroacoustic performance is proposed due to its ease of use and relatively low requirements for user input.The solid serrations are replicated by momentum sources calculated by its aerodynamic forces.Then,a case relevant to wind turbine airfoil is examined,a hybrid improved delay detached eddy simulation(IDDES)method coupled with FW-H integration is deployed to obtain the flow features and far-field sound pressure level.It is found that the modeling method could reproduce the flow field and noise as serrated airfoil.
基金The research herein reported did gratefully receive funding from Seventh Framework Programme of the European Union(FP7/2007-2013)under Grant Agreement N.284562,SARISTUThe project was prodigiously and effectively coordinated by Piet Christof Woelcken(Airbus)with the support of Michael Papadopoulos(EASN–European Aeronautic Science Network).
文摘SARISTU was a big cooperation project granted by the European Commission,7th Framework Programme,carried out between 2011 and 2015.It dealt with smart aeronautic structures,both morphing and sensored;its main target was to demonstrate the feasibility of designing,manufacturing and operating in representative environment,instrumented structures.Till now,it represents the major effort carried out within the European Union on the development of adaptive architectures for air systems.Inside that big activity,the realization of an Adaptive Trailing Edge Device(ATED)for wing camber adaptations aimed at compensating the weight reduction following the fuel consumption during cruise was addressed.It made the core of investigations target variable geometry aircraft components together with two other analyses concerning the development of shape-changing winglet and droop nose.ATED activities were conducted by the Italian Aerospace Research Centre(CIRA)in tight cooperation with the University of Napoli,"Federico II",who coordinated a group of 12 different partners from 8 different nations(France,Germany,Greece,the Netherlands,Israel,Spain,Turkey,and Italy).In this paper,an integral synthesis of that work is reported,with a focus on the definition and realization of the components of the presented device.The publication is in fact meant as the first part of a series that is aimed at overviewing the whole adaptive trailing edge development,till wind tunnel tests execution.Such a concise report is a critical and harmonized review of what have been performed by many colleagues spread all over Europe,all of which are duly recalled in the reported bibliography where the reader may access more detailed information and descriptions.In detail,the paper starts with a general introduction of the concept and its aims,to move to the specs definition immediately after.Then,it deals with a short but comprehensive description of the main ATED components:structural skeleton,skin,actuation and sensing systems.It is worth remarking that the paragraph dedicated to the body frame includes some discussion about aeroelastic assessment and manufacture,seen as complementation for a complete assessment of the design constraints.
文摘This article deals with the effects of a blowing ratio measured with narrowband liquid crystal in transonic experiments on the heat transfer characteristics of trailing edge cutback. The experimental results are compared and contrasted in terms of available data for traditional experiments with thermocouples. It is concluded that the blowing ratio exerts rather significant effects on film cooling effectiveness distribution of the rib center line. As the blowing ratio decreases, similar to the cooling effectiveness distribution curve of the slot center line, that of the rib center line makes a clockwise rotation about the end. When the blowing ratio increases, the regular film cooling effectiveness curve of the surface becomes rather smooth. On the whole measuring surface, the most intensive heat transfer occurs at the extended borderline of the slot and the rib, neither at the rib center line nor at the slot center line. The experimental results of cooling effectiveness measured with thermocouples are lower than those with liquid crystal. In addition, the transient experiments using narrowband liquid crystal can eliminate the higher errors of Nusselt numbers in measurements with thermocouples at the slot outlet.
基金co-supported by the National Natural Science Foundation of China(Nos.51375383 and 51575443)Natural Science Foundation of Shaanxi Province of China(No.2019JQ-728)Doctor’s Research Foundation of Xi’an University of Technology of China(No.102-451118017)。
文摘The morphing trailing edge based compliant mechanism is a developing technology which can increase lift-drag ratio for variable flight modes by bending down the trailing edge.Composite material design is integrated into topology optimization for the morphing trailing edge based compliant mechanism in the paper.A two-step optimization strategy is established to solve the integrated design problem.Initially,lamination parameters are introduced and viewed as a bridge between structure stiffness and fiber angles for composite material.Design variables include the lamination parameters and element density.The least-squares between actual and desired displacements at output points along trailing edge is adopted to evaluate the deformed capability of the trailing edge.An integrated optimization model for the composite morphing trailing edge is established with the volume constraints.The optimal topologic shape and lamination parameters are initially obtained.Subsequently,a least-squares optimization between fiber angles and the optimal lamination parameters is implemented to obtain optimal fiber angles.Finally,morphing capability of composites trailing edge based compliant mechanism is investigated by simulation and experiments.The results indicate the composites trailing edge based compliant mechanism can approximately bend down 8 degrees and satisfies the design requirement.
文摘This paper presented an experimental investigation the effects of the trailing edge cooling on the aerodynamic performance. The experiments were conducted on the low-speed linear cascade tunnel at Northwestern Polytechnical University. The external aerodynamic characteristics in the 40 percent chord downstream of exit plane were measured using five-hole probe with the different ejection rates. The results showed that the total pressure loss coefficient at the middle spanwise plane increased at first and then it has a decreasing tendency with the increase of ejection ratio. The trailing edge cooling would influence the structure of the turbine cascade outlet flow field. When the ejection rate was 3%,the loss area near the blade endwall would become stronger,but it would become weaker with the 6% ejection ratio. On the whole,the trailing edge cooling had more influence on the profile loss than on the secondary loss.
基金supported by National Natural Science Foundation of China (Grant No. 11102019)
文摘Morphing wing has attracted many research attention and effort in aircraft technology development because of its advantage in lift to draft ratio and flight performance.Morphing wing technology combines the lift and control surfaces into a seamless wing and integrates the primary structure together with the internal control system.It makes use of the wing aeroelastic deformation induced by the control surface to gain direct force control through desirable redistribution of aerodynamic forces.However some unknown mechanical parameters of the control system and complexity of the integrated structure become a main challenge for dynamic modeling of morphing wing.To solve the problem,a method of test data based modal sensitivity analysis is presented to improve the morphing wing FE model by evaluating the unknown parameters and identifying the modeling boundary conditions.An innovative seamless morphing wing with the structure integrated with a flexible trailing edge control system is presented for the investigation.An experimental model of actuation system driven by a servo motor for the morphing wing is designed and established.By performing a vibration test and the proposed modal sensitivity analysis,the unknown torsional stiffness of the servo motor and the boundary condition of the actuation mechanism model is identified and evaluated.Comparing with the test data,the average error of the first four modal frequency of the improved FE model is reduced significantly to less than 4%.To further investigate the morphing wing modeling,a wing box and then a whole morphing wing model including the skin and integrated with the trailing edge actuation system are established and tested.By using the proposed method,the FE model is improved by relaxing the constraint between the skin and actuation mechanism.The results show that the average error of the first three modal frequency of the improved FE model is reduced to less than 6%.The research results demonstrate that the presented seamless morphing wing integrated with a flexible trailing edge control surface can improve aerodynamic characteristics.By using the test data based modal sensitivity analysis method,the unknown parameter and boundary condition of the actuation model can be determined to improve the FE model.The problem in dynamic modeling of high accuracy for a morphing wing can be solved in an effective manner.
文摘The turbulent wakes behind trailing edge are analyzed for understanding of the flow mechanisms responsible for the generation of trailing edge noise. The TILS （turbulence integral length scale） of the turbulent wake of hydrofoil with blunt trailing edge is calculated from TR-PIV （time-resolved particle image velocimetry） data. The temporal auto-correlation method based on Taylor hypothesis and spatial correlation method are used to get the TILS information of the turbulent wake of hydrofoil, respectively The comparison of results by two methods indicates that the spatial correlation method is independent on Taylor hypothesis and suitable to strong turbulence and non-isotropic turbulence.
基金financial support of National Natural Science Foundation of China (Grant No.52306055)National Science and Technology Major Project (J2019-Ⅱ-0022-0043)Youth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘This paper investigates the film cooling characteristics and flow structure of trailing edge cutback in turbine vanes,and explains the unsteady flow mixing mechanism of this cooling structure using Proper Orthogonal Decomposition(POD) method.The Delayed Detached Eddy Simulation(DDES) turbulence model was used to obtain detailed information about the velocity and temperature field for the POD method.To verify the accuracy of the numerical results,fast-response Pressure Sensitive Paint(PSP) and high-frequency Particle Image Velocimetry(PIV) experiments were also conducted,and the results achieved good agreement.As the blowing ratio increases,the effectiveness η of the cutback's film cooling exhibits a "increase-decrease-increase" trend,with η reaching its minimum point at around a blowing ratio(M_(slot)) of 0.75.Three kinds of coherent vortex structures are observed in the flow field at different blowing ratios.According to the analysis using the POD method,the first and second order modes of a Karman-like vortex street are observed in the vicinity of the wall at various blowing ratios.This coherent flow structure is directly related to the mixing intensity between the mainstream gas and the coolant.At M_(slot)=0.75,these modes had the highest energy ratio and formed a stable dominant coherent structure in the flow field.As the blowing ratio increases,the main characteristic modes in the temperature field gradually change,and the mode appears crescent-shaped when the effectiveness of film cooling is at its lowest.This paper combines the vortex structure of the flow field to explain the flow field feature distribution at the lowest effectiveness point η and analyzes its impact on the film cooling characteristics of the protected surface.
基金the National Natural Science Foundation of China(Nos.52171316 and 51479116)。
文摘Vortex-induced vibration of hydrofoils is concerned with structural safety and noise level in hydraulic machinery and marine engineering.The research on vibration characteristics under different operating conditions is significant.In this study,numerical simulations are conducted to investigate the vortex-induced vibration responses of an elastically suspended hydrofoil with blunt trailing edge in pitch direction.The work studies the effects of four parameters,namely the structural natural frequency,mass ratio,initial attack angle,and Reynolds number on vibration characteristics,with special emphasis on frequency lock-in.Results indicate that as the structural natural frequency changes,the vibration amplitude may increase substantially within a certain frequency range,in which the vortex shedding frequency locks into the structural natural frequency,and frequency lock-in occurs.In addition,with increasing the mass ratio,the frequency range of lock-in becomes narrower,and both the upper and lower thresholds decrease.As the initial attack angle increases from 0◦to 6◦,the lock-in range gets reduced.Over the three Reynolds numbers(6×10^(5),9×10^(5),and 12×10^(5)),the lock-in range remains virtually unchanged.Moreover,for a certain structural natural frequency,modifying the mass ratio,initial attack angle,and Reynolds number could effectively suppress the vibration amplitude.
基金supported by the Research Fund of 2014 Chungnam National University of the Korea
文摘This paper discussed a noise reduction effect of airfoil and small-scale model rotor by using attached serration trailing edge in the wind tunnel test condition. In order to analyze the changes in the performance due to the inclusion of a serrated trailing edge designed to reduce noise, a 10 k W wind turbine rotor was equipped with a thin serrated trailing edge. The restrictive condition for the serrated trailing edge equipped with the using of a 2D airfoil was examined through the using of a wind tunnel experiment after studying existing restrictive condition and analyzing prior research on serrated trailing edges. The aerodynamic performance and noise reduction effect of a small-scale model were investigated with the using of a serrated trailing edge. Moreover, the noise levels from the experiment were considered that the noise prediction method could be used for a full-scale rotor. It is confirmed that noise reduction effect is compared with wind tunnel test data at the 2D airfoil and model rotor condition.
文摘An experimental study was conducted to quantify the flow characteristics of the wall jets pertinent to trailing edge cooling of turbine blades.A high-resolution stereoscopic particle image velocimetry(PIV)system was used to conduct detailed flow field measurements to quantitatively visualize the evolution of the unsteady vortices and turbulent flow structures in the cooling wall jet streams and to quantify the dynamic mixing process between the cooling jet stream and the mainstream flows.The detailed flow field measurements were correlated with the adiabatic cooling effectiveness maps measured by using pressure sensitive paint(PSP)technique to elucidate underlying physics in order to explore/optimize design paradigms for improved cooling effectiveness to protect the critical portions of turbine blades from harsh environments.
基金supported by National Natural Science Foundation of China,Grant No.51421063
文摘Unsteady numerical simulations of a high-load transonic turbine stage have been carried out to study the influences of vane trailing edge outer-extending shockwave on rotor blade leading edge film cooling performance. The turbine stage used in this paper is composed of a vane section and a rotor one which are both near the root section of a transonic high-load turbine stage. The Mach number is 0.94 at vane outlet, and the relative Mach number is above 1.10 at rotor outlet. Various positions and oblique angles of film cooling holes were investigated in this research. Results show that the cooling efficiency on the blade surface of rotor near leading edge is significantly affected by vane trailing edge outer-extending shockwave in some cases. In the cases that film holes are close to leading edge, cooling performance suffers more from the sweeping vane trailing edge outer-extending shockwave.In addition, coolant flow ejected from oblique film holes is harder to separate from the blade surface of rotor, and can cover more blade area even under the effects of sweeping vane trailing edge shockwave. As a result, oblique film holes can provide better film cooling performance than vertical film holes do near the leading edge on turbine blade which is swept by shockwaves.
文摘The characteristics of flow past beveled trailing edges attached to flat plates have been investigated numerically and experimentally. The test models used in the present study were two 2D blunt-faced flat plates having asymmetric beveled trailing edges of angles 27° and 60°. The numerical simulation results display an asymmetric wake behind the 27° beveled trailing edge and von karmen street vortices behind the 60° beveled trailing edge. The flow visualization using cavitation technique showed the same observations of the numerical simulation. Therefore, it is obvious that the trailing edge geometry has a pronounced effect on the wake development and vortex shedding. Also, it is concluded that the cavitation phenomenon can be used as a visualization technique at high flow velocities.
基金supported by the Italian Ministry of Education,University and Research (MIUR)
文摘The aerothermal performance of a trailing edge （TE） internal cooling system of a high pressure gas turbine blade was evaluated under stationary and rotating conditions. The investigated geometry consists of a 30：1 scaled model reproducing a typical wedge shaped discharge duct with one row of enlarged pedestals. The airflow pattern inside the device simulates a highly loaded rotor blade cooling scheme with a 90 [deg] turning flow from the radial hub inlet to the tangential TE outlet. Two different tip configurations were tested, the first one with a completely closed section, the second one with a 5 holes outlet surfaces discharging at ambient pressure. In order to assess rotation effects, a rotating test rig, composed of a rotating ann holding both the PMMA TE model and the instru mentation, was purposely developed and manufactured. A thin Inconel heating foil and wide band Thermochromic Liquid Crystals are used to perform steady state heat transfer measurements on the blade pres sure side. A rotary joint ensures the pneumatic connection between the blower and the rotating apparatus; more over several slip rings are used for both instrumentation power supply and thermocouple connection. A parallel CFD analysis involving steadystate RANS modeling was conducted to allow an insight of the flow field inside the redirecting channel and the interpedestal ducts to better interpret the developing vortical structures. LowReynolds grid clustering permits to integrate up to the wall both the momentum and the thermal boundary layer. Calculations were performed by means of an inhouse developed pressure based solver exploiting the kco SST turbulence model implemented in the framework of the opensource finite volume discretization toolbox OpenFOAM~. Analyzed flow conditions correspond to Reynolds number of 20000 in the hub inlet section and angular speed varies to obtain rotation numbers in the range from 0 to 0.3. The orientation of the rotation axis is orthogonal to the heated surface as to resemble a 90 [deg] blade metal angle. Results are reported in terms of de tailed heat transfer coefficient 2D maps on the suction side surface as well as spanwise profiles inside the pedestal ducts.
文摘Nowadays total inlet temperature of gas turbine is far above the permissible metal temperature;as a consequence,advanced cooling techniques must be applied to protect from thermal stresses,oxidation and corrosion the components located in the high pressure stages,such as the blade trailing edge.A suitable design of the cooling system for the trailing edge has to cope with geometric constraints and aerodynamic demands;state-of-the-art of cooling concepts often use film cooling on blade pressure side:the air taken from last compressor stages is ejected through discrete holes or slots to provide a cold layer between hot mainstream and the blade surface.With the goal of ensuring a satisfactory lifetime of blades,the design of efficient trailing edge film cooling schemes and,moreover,the possibility to check carefully their behavior,are hence necessary to guarantee an appropriate metal temperature distribution.For this purpose an experimental survey was carried out to investigate the film covering performance of different pressure side trailing edge cooling systems for turbine blades.The experimental test section consists of a scaled-up trailing edge model installed in an open loop suction type test rig.Measurements of adiabatic effectiveness distributions were carried out on three trailing edge cooling system configurations.The baseline geometry is composed by inclined slots separated by elongated pedestals;the second geometry shares the same cutback configuration,with an additional row of circular film cooling holes located upstream;the third model is equipped with three rows of in-line film cooling holes.Experiments have been performed at nearly ambient conditions imposing several blowing ratio values and using carbon dioxide as coolant in order to reproduce a density ratio close to the engine conditions(DR¼1.52).To extend the validity of the survey a comparison between adiabatic effectiveness measurements and a prediction by correlative approach was performed to compare the experimental results with 1D methodologies.
基金supported by the National Foundation for Innovative Research Groups of China(Grant No.51421063)
文摘This paper presents a new idea to reduce the solidity of low-pressure turbine(LPT) blade cascades,while remain the structural integrity of LPT blade.Aerodynamic performance of a low solidity LPT cascade was improved by increasing blade trailing edge thickness(TET).The solidity of the LPT cascade blade can be reduced by about12.5% through increasing the TET of the blade without a significant drop in energy efficiency.For the low solidity LPT cascade,increasing the TET can decrease energy loss by 23.30% and increase the flow turning angle by1.86% for Reynolds number(Re) of 25,000 and freestream turbulence intensities(FSTT) of 2.35%.The flow control mechanism governing behavior around the trailing edge of an LPT cascade is also presented.The results show that appropriate TET is important for the optimal design of high-lift load LPT blade cascades.
文摘The flow around two plates having asymmetric beveled trailing edge placed side-by-side in a uniform stream were investigated both numerically and experimentally. Two plates with spacing ratio of 1.0 and beveled trailing edge of angle 20° were tested at Reynolds numbers equal to 3.97×10^4. The numerical simulation results displayed that the flow separates on one plate beveled trailing edge surface. The vortex formation and shedding from this plate led to deflecting the flow toward the other plate and consequently the wake behind the plates showed an asymmetric development. The photographs obtained from the flow visualization confirmed the numerical results concerning the flow separation and vortex formation. It was also found that the computed pressure distribution on the two plate surfaces was different, particularly on the beveled trailing edge surfaces and on the fiat sides.
