The deviation in wall thickness caused by core shift during the investment casting process significantly impacts the strength and service life of hollow turbine blades.To address this issue,a core shift limitation met...The deviation in wall thickness caused by core shift during the investment casting process significantly impacts the strength and service life of hollow turbine blades.To address this issue,a core shift limitation method is developed in this study.Firstly,a shift model is established based on computational fluid dynamics and motion simulation to predict the movement of the ceramic core in investment casting process.Subsequently,utilizing this model,an optimization method for fixturing layout inside the refractory ceramic shell is devised for the ceramic core.The casting experiment demonstrates that by utilizing the optimized fixture layout,not only can core shift during the investment casting pouring process be effectively controlled,but also the maximum wall thickness error of the blade can be reduced by 42.02%.In addition,the core shift prediction is also validated,with a prediction error of less than 26.9%.展开更多
In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile desig...In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.展开更多
The directional solidification process of turbine blade sample castings was investigated in the work. Variable withdrawal rates were used in one withdrawal process and compared with the other using uniform rate. A mat...The directional solidification process of turbine blade sample castings was investigated in the work. Variable withdrawal rates were used in one withdrawal process and compared with the other using uniform rate. A mathematical model for heat radiation transfer and microstructure simulation of directional solidification process was developed based on CA-FD method. The temperature distribution and microstructure w.ere simulated and compared with the experimental results. The stray grains were predicted and compared with the experimental results. The uneven temperature distribution of platform was the main reason of the formation of stray grains.展开更多
To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the ...To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality.展开更多
As the key parts of an aero-engine,single crystal(SX)superalloy turbine blades have been the focus of much attention.However,casting defects often occur during the manufacturing process of the SX turbine blades.Modeli...As the key parts of an aero-engine,single crystal(SX)superalloy turbine blades have been the focus of much attention.However,casting defects often occur during the manufacturing process of the SX turbine blades.Modeling and simulation technology can help to optimize the manufacturing process of SX blades.Multiscale coupled models were proposed and used to simulate the physical phenomena occurring during the directional solidification(DS)process.Coupled with heat transfer(macroscale)and grain growth(meso-scale),3D dendritic grain growth was calculated to show the competitive grain growth at micro-scale.SX grain selection behavior was studied by the simulation and experiments.The results show that the geometrical structure and technical parameters had strong influences on the grain selection effectiveness.Based on the coupled models,heat transfer,grain growth and microstructure evolution of a complex hollow SX blade were simulated.Both the simulated and experimental results show that the stray grain occurred at the platform of the SX blade when a constant withdrawal rate was used in manufacturing process.In order to avoid the formation of the stray crystal,the multi-scale coupled models and the withdrawal rate optimized technique were applied to the same SX turbine blade.The modeling results indicated that the optimized variable withdrawal rate can achieve SX blade castings with no stray grains,which was also proved by the experiments.展开更多
A new technology,semi-solid casting(thixocasting) method,was used to replace the conventional hot forging process to form AISI420 stainless steel air-turbine blade.The power law cut-off(PLCO) material model in Procast...A new technology,semi-solid casting(thixocasting) method,was used to replace the conventional hot forging process to form AISI420 stainless steel air-turbine blade.The power law cut-off(PLCO) material model in Procast software was used to simulate the thixocasting process.The thixocasting process was simulated.The results show that the reasonable technology parameters for air-turbine blade thixocasting process are obtained:billet temperature 1 483-1 485 °C,piston velocity 12-15 m/s and die temperature is about 400 °C.展开更多
During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turb...During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turbine blade castings at the still air cooling and forced air cooling stages during heat treatment process. The method was used to measure the distortion behavior at the cooling stages in both normalizing and tempering processes. At the normalization, the distortion at the blade comer near outlet side undergoes four stages with alternating bending along positive and negative directions. At the tempering stage, the distortion could be divided into two steps. The temperature difference between the two surfaces of blade casting was employed to analyze the distortion mechanism. The measured results could be applied to guide the production, and the machining allowance could be reduced by controlling the distortion behavior.展开更多
An integration system was developed to satisfy the need of information integration in the process of designing, investment casting and monitoring aero-engine's turbo blade. The general architecture is detailed pre...An integration system was developed to satisfy the need of information integration in the process of designing, investment casting and monitoring aero-engine's turbo blade. The general architecture is detailed presented in this paper. The system mainly comprises of product master model, design information management, anti-deformation design of mould cavity, intelligence mould design and blade testing. The developed system can manage mould design and blade test data flow, optimize mould design process and achieve the goal of integration design.展开更多
The three-dimensional solidification simulation of the investment castings of single crystal hollow turbine blade at the withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min has been performed with the finite element...The three-dimensional solidification simulation of the investment castings of single crystal hollow turbine blade at the withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min has been performed with the finite element thermal analysis. The calculated results are in accordance with the experimental ones. The results show that with the increase of withdrawal rate the concave curvature of the liquidus isotherm is larger and larger, and the temperature gradients of the blades increase. No effects of withdrawal rate on the distribution of the temperature gradients of the starter and helical grain selector of the blades are observed at withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min. The relatively high temperature gradient between 500℃/cm and 1000℃/cm in the starter and helical grain selector is obtained at three withdrawal rates.展开更多
In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of h...In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling(LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength(the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature(1,520 ℃ for upper region and 1,500 ℃ for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring(3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation <001>, resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate.展开更多
Laser shock peening （LSP） is a novel effective surface treatment method to improve the fatigue performance of turbine blades. To study the effect of LSP on combined low- and high-cycle fatigue （CCF） life of turbin...Laser shock peening （LSP） is a novel effective surface treatment method to improve the fatigue performance of turbine blades. To study the effect of LSP on combined low- and high-cycle fatigue （CCF） life of turbine blades, the CCF tests were conducted at elevated temperatures on two types of full-scale turbine blades, which were made of K403 by casting and GH4133B by forging. Probabilistic analysis was conducted to find out the effect of LSP on fatigue life of those two kinds of blades. The results indicated that LSP extended the CCF life of both casting blades and forging blades obviously, and the effect of LSP on casting blades was more evident; besides, a threshold vibration stress existed for both casting blades and forging blades, and the CCF life tended to be extended by LSP only when the vibration stress was below the threshold vibra- tion stress. Further study of fractography was also conducted, indicating that due to the presence of compressive residual stress and refined grains induced by LSP, the crack initiation sources in LSP blades were obviously less, and the life of LSP blades was also longer; since the compressive residual stress was released by plastic deformation, LSP had no effect or adverse effect on CCF life of blade when the vibration stress of blade was above the threshold vibration stress.展开更多
A turbine blade is one of the key components of the aero-engine. Its geometric shape should be inspected carefully in the production stage to ensure that it meets the tolerance specification. In the present paper, an ...A turbine blade is one of the key components of the aero-engine. Its geometric shape should be inspected carefully in the production stage to ensure that it meets the tolerance specification. In the present paper, an approach for investment turbine blade geometric shape analysis based on multi-source digital measurement is presented. Its key technologies, such as measurement data collection, blade model reliable alignment, geometric shape deviation fast calculation and visualization, were investigated. Actual measurement data from a structure light measurement device and a Coordinate Measuring Machine(CMM) for turbine blades were used to validate the presented method. The experimental results show that the proposed method is accurate, quick and effective to implement.展开更多
To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structur...To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structural correlation study.Numerical simulations and pouring experiments were carried out based on the designed double-walled model,and a reliable displacement field model of the double-walled blade was established.A decoupling method for the displacement field of the double-walled blade castings was proposed,which decoupled the displacement field into bending,torsion,and expansion/shrinkage deformation vectors.Based on the displacement field analysis of the theoretical and physical models,an expansion/shrinkage model of double-walled blade structure castings was established.Furthermore,an experiment to determine the mapping relationship between double-walled construction and deformation was designed,which included the characteristic distribution distance and designed angle as structural parameters.The functional relationship between the deformation and the structural parameters was established based on a nonlinear regression method.展开更多
Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and n...Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.展开更多
To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the ro...To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the rotating blades applied in contra-rotating open rotors under the concept of frozen-rotor.A 70-channel phased microphone array and nine high-precision free-field microphones are employed.The beamforming method,enhanced by a source filtering technique,is employed to locate noise sources,providing insights into the source patterns of blade-blade interaction noise concerning flow speed,blade spacing,and aft blade clipping.The results show the following:(A)Sources of tandem-blade noise exist in the form of concentrated source clusters,resulting in two major clusters:the mid-span interaction noise and the tip-induced noise.(B)These source clusters tend to separate as flow speed or blade spacing increases.(C)By increasing blade spacing,the band-pass filtered overall sound pressure level is reduced by 2.9 dB.(D)A two-phase noise suppression pattern is observed with blade clipping,resulting in a total reduction of 3.0 dB for the interaction noise through the removal of tip-induced noise sources and the replacement of mid-span noise sources.Based on these findings,suggestions concerning blade spacing and clipping are discussed.展开更多
Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiske...Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.展开更多
This study investigates the formation feasibility of the integrated bottom car body components with dual die casting injection molding technology.During the production of a die-cast super-large one-piece body part wei...This study investigates the formation feasibility of the integrated bottom car body components with dual die casting injection molding technology.During the production of a die-cast super-large one-piece body part weighing over 10,000 t,a thorough comparison and investigation were conducted on the arising issues,using both single and double injection systems.Particular attention was given to meticulously discussing the die casting filling problems and microstructural defects that originated from the filling process.The research findings indicate that the implementation of a double injection system can significantly minimize cold shuts and reduce the solidification time.The effectiveness of this die casting technique was further confirmed by the production of high-quality castings using a scaled model that replicated real casting conditions at a 1:3 ratio,thereby maintaining a one-to-one correspondence in essential aspects.This successful study offers both theoretical insights and practical applications for the production of integrated bottom car bodies utilizing die casting in conjunction with a dual injection system.展开更多
Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.Howev...Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.展开更多
基金the National Natural Science Foundation of China(Grant No.52005311)the Scientific and the National Science and Technology Major Project(Grant No.J2019-VII-0013-0153)Research Project Supported by Shanxi Scholarship Council of China(Grant No.2023-003).
文摘The deviation in wall thickness caused by core shift during the investment casting process significantly impacts the strength and service life of hollow turbine blades.To address this issue,a core shift limitation method is developed in this study.Firstly,a shift model is established based on computational fluid dynamics and motion simulation to predict the movement of the ceramic core in investment casting process.Subsequently,utilizing this model,an optimization method for fixturing layout inside the refractory ceramic shell is devised for the ceramic core.The casting experiment demonstrates that by utilizing the optimized fixture layout,not only can core shift during the investment casting pouring process be effectively controlled,but also the maximum wall thickness error of the blade can be reduced by 42.02%.In addition,the core shift prediction is also validated,with a prediction error of less than 26.9%.
基金Project (2008ZE53042) supported by National Aerospace Science Foundation of China
文摘In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.
文摘The directional solidification process of turbine blade sample castings was investigated in the work. Variable withdrawal rates were used in one withdrawal process and compared with the other using uniform rate. A mathematical model for heat radiation transfer and microstructure simulation of directional solidification process was developed based on CA-FD method. The temperature distribution and microstructure w.ere simulated and compared with the experimental results. The stray grains were predicted and compared with the experimental results. The uneven temperature distribution of platform was the main reason of the formation of stray grains.
文摘To solve the problems in turbine blade investment casting die design process such as long design time,lacking of expert experience and low level of intelligence,knowledge-based engineering (KBE) was introduced in the turbine blade investment casting die design field. The key technologies of the intelligent design method were researched and a prototype system was developed. A hybrid reasoning model was prompted in which case-based reasoning (CBR) was applied to conceptual design and rule-based reasoning (RBR) was applied to parts design after research the design process and domain knowledge of casting die. In the conceptual design stage,a retrieval model which integrated nearest neighbor approach and knowledge-based retrieval approach was prompted to improve the retrieval efficiency. Meanwhile,RBR was used to modify the retrieval result. The practical application results indicate that this system can reuse the expert experience efficiently and heighten the die design efficiency and quality.
基金supported by the National Basic Research Program of China(No.2011CB706801)the National Natural Science Foundation of China(Nos.51171089 and 51374137)the National Science and Technology Major Project(Nos.2011ZX04014-052 and 2012ZX04012-011)
文摘As the key parts of an aero-engine,single crystal(SX)superalloy turbine blades have been the focus of much attention.However,casting defects often occur during the manufacturing process of the SX turbine blades.Modeling and simulation technology can help to optimize the manufacturing process of SX blades.Multiscale coupled models were proposed and used to simulate the physical phenomena occurring during the directional solidification(DS)process.Coupled with heat transfer(macroscale)and grain growth(meso-scale),3D dendritic grain growth was calculated to show the competitive grain growth at micro-scale.SX grain selection behavior was studied by the simulation and experiments.The results show that the geometrical structure and technical parameters had strong influences on the grain selection effectiveness.Based on the coupled models,heat transfer,grain growth and microstructure evolution of a complex hollow SX blade were simulated.Both the simulated and experimental results show that the stray grain occurred at the platform of the SX blade when a constant withdrawal rate was used in manufacturing process.In order to avoid the formation of the stray crystal,the multi-scale coupled models and the withdrawal rate optimized technique were applied to the same SX turbine blade.The modeling results indicated that the optimized variable withdrawal rate can achieve SX blade castings with no stray grains,which was also proved by the experiments.
基金Project(50375117) supported by the National Natural Science Foundation of China
文摘A new technology,semi-solid casting(thixocasting) method,was used to replace the conventional hot forging process to form AISI420 stainless steel air-turbine blade.The power law cut-off(PLCO) material model in Procast software was used to simulate the thixocasting process.The thixocasting process was simulated.The results show that the reasonable technology parameters for air-turbine blade thixocasting process are obtained:billet temperature 1 483-1 485 °C,piston velocity 12-15 m/s and die temperature is about 400 °C.
基金supported financially by the National Eleventh Five-Year Science and Technology Support Program of China through Grant No.2007BAF02B02Major National Sci-Tech Project of China No 2011ZX04014-052
文摘During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turbine blade castings at the still air cooling and forced air cooling stages during heat treatment process. The method was used to measure the distortion behavior at the cooling stages in both normalizing and tempering processes. At the normalization, the distortion at the blade comer near outlet side undergoes four stages with alternating bending along positive and negative directions. At the tempering stage, the distortion could be divided into two steps. The temperature difference between the two surfaces of blade casting was employed to analyze the distortion mechanism. The measured results could be applied to guide the production, and the machining allowance could be reduced by controlling the distortion behavior.
基金National High-tech R&D Program (863 Program) (2006AA04Z144)Key Technologies R&D Program (2006BAF04B02).
文摘An integration system was developed to satisfy the need of information integration in the process of designing, investment casting and monitoring aero-engine's turbo blade. The general architecture is detailed presented in this paper. The system mainly comprises of product master model, design information management, anti-deformation design of mould cavity, intelligence mould design and blade testing. The developed system can manage mould design and blade test data flow, optimize mould design process and achieve the goal of integration design.
文摘The three-dimensional solidification simulation of the investment castings of single crystal hollow turbine blade at the withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min has been performed with the finite element thermal analysis. The calculated results are in accordance with the experimental ones. The results show that with the increase of withdrawal rate the concave curvature of the liquidus isotherm is larger and larger, and the temperature gradients of the blades increase. No effects of withdrawal rate on the distribution of the temperature gradients of the starter and helical grain selector of the blades are observed at withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min. The relatively high temperature gradient between 500℃/cm and 1000℃/cm in the starter and helical grain selector is obtained at three withdrawal rates.
基金financially supported by the National Science and Technology Major Project of High-end CNC Machine Tools and Basic Manufacturing Equipment(No.2017ZX04014001)
文摘In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling(LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength(the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature(1,520 ℃ for upper region and 1,500 ℃ for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring(3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation <001>, resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate.
基金This work was supported by National Natural Science Foundation of China （Grant Nos. 11602010 and 51505018）.
文摘Laser shock peening （LSP） is a novel effective surface treatment method to improve the fatigue performance of turbine blades. To study the effect of LSP on combined low- and high-cycle fatigue （CCF） life of turbine blades, the CCF tests were conducted at elevated temperatures on two types of full-scale turbine blades, which were made of K403 by casting and GH4133B by forging. Probabilistic analysis was conducted to find out the effect of LSP on fatigue life of those two kinds of blades. The results indicated that LSP extended the CCF life of both casting blades and forging blades obviously, and the effect of LSP on casting blades was more evident; besides, a threshold vibration stress existed for both casting blades and forging blades, and the CCF life tended to be extended by LSP only when the vibration stress was below the threshold vibra- tion stress. Further study of fractography was also conducted, indicating that due to the presence of compressive residual stress and refined grains induced by LSP, the crack initiation sources in LSP blades were obviously less, and the life of LSP blades was also longer; since the compressive residual stress was released by plastic deformation, LSP had no effect or adverse effect on CCF life of blade when the vibration stress of blade was above the threshold vibration stress.
基金financially supported by the Major National S&T Project(No.2012ZX04007021)Doctoral fund of China(No.2013YD050008)
文摘A turbine blade is one of the key components of the aero-engine. Its geometric shape should be inspected carefully in the production stage to ensure that it meets the tolerance specification. In the present paper, an approach for investment turbine blade geometric shape analysis based on multi-source digital measurement is presented. Its key technologies, such as measurement data collection, blade model reliable alignment, geometric shape deviation fast calculation and visualization, were investigated. Actual measurement data from a structure light measurement device and a Coordinate Measuring Machine(CMM) for turbine blades were used to validate the presented method. The experimental results show that the proposed method is accurate, quick and effective to implement.
基金This research was funded by the National Natural Science Foundation of China(Grant Number 51705440)the Natural Science Foundation of Fujian Province,China(Grant Number 2019J01044)+1 种基金the Aeronautical Science Foundation of China(Grant Number 20170368001)the National Science and Technology Major Project of China(Nos.J2019-III-0008 and J2019-VII-0013-0153)。
文摘To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structural correlation study.Numerical simulations and pouring experiments were carried out based on the designed double-walled model,and a reliable displacement field model of the double-walled blade was established.A decoupling method for the displacement field of the double-walled blade castings was proposed,which decoupled the displacement field into bending,torsion,and expansion/shrinkage deformation vectors.Based on the displacement field analysis of the theoretical and physical models,an expansion/shrinkage model of double-walled blade structure castings was established.Furthermore,an experiment to determine the mapping relationship between double-walled construction and deformation was designed,which included the characteristic distribution distance and designed angle as structural parameters.The functional relationship between the deformation and the structural parameters was established based on a nonlinear regression method.
基金supported by the National Natural Science Foundation of China(Nos.52405088 and 92360306)the Postdoctoral Fellowship Program of CPSF,China(No.GZC20241446)+2 种基金the Natural Science Basic Research Program of Shaanxi,China(No.2024JC-YBMS-402)the Fundamental Research Funds for the Central Universities,CHD(No.300102254102)the Foundation of Beilin District,China(No.GX2455)。
文摘Anti-aliasing spectrum analysis is essential for rotor blade condition monitoring based on Blade Tip Timing(BTT).The Multiple Signal Classification(MUSIC)algorithm,which exploits the orthogonality between signal and noise subspaces,has been successfully applied for this purpose.However,conventional subspace selection methods relying on fixed thresholds are sensitive to variations in large eigenvalues.Furthermore,the complex disturbances during rotor operation and measurement complicate the identification of blade vibration characteristics.To overcome these challenges,this paper proposes Adaptive Subspace Separation(ASS)and Local Spectral Centroid(LSC)methods to improve the adaptability of subspace selection and the stability of frequency identification,respectively.The impacts of overestimating and underestimating the subspace dimensions on MUSIC's performance are derived mathematically.Simulation and experiments demonstrate the effectiveness of proposed approaches:ASS offers more accurate and stable subspace dimension selection and tracking,while LSC reduces the standard deviation of estimated frequencies by 30 percent.
基金supported by grants from the National Natural Science Foundation of China(Nos.12102451,12072186)the National Science and Technology Major Project,China(No.J2019-II-0006-0026)AVIC Aerodynamics Research Institute,China(No.XFX20220201).
文摘To facilitate the low-noise design of tandem lift bodies as applied in aeroengines and aircraft,the acoustic features of tandem blades are investigated by wind-tunnel experiments.This is further specialized for the rotating blades applied in contra-rotating open rotors under the concept of frozen-rotor.A 70-channel phased microphone array and nine high-precision free-field microphones are employed.The beamforming method,enhanced by a source filtering technique,is employed to locate noise sources,providing insights into the source patterns of blade-blade interaction noise concerning flow speed,blade spacing,and aft blade clipping.The results show the following:(A)Sources of tandem-blade noise exist in the form of concentrated source clusters,resulting in two major clusters:the mid-span interaction noise and the tip-induced noise.(B)These source clusters tend to separate as flow speed or blade spacing increases.(C)By increasing blade spacing,the band-pass filtered overall sound pressure level is reduced by 2.9 dB.(D)A two-phase noise suppression pattern is observed with blade clipping,resulting in a total reduction of 3.0 dB for the interaction noise through the removal of tip-induced noise sources and the replacement of mid-span noise sources.Based on these findings,suggestions concerning blade spacing and clipping are discussed.
文摘Considering the fracture problem of the silica-based ceramic core in the integrated casting of hollow turbine blades during directional solidification,the influence of various whiskers,including silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,on the high-temperature strength of the silica-based ceramic core was investigated.Additionally,the formation of microstructure morphology and phase structure was analyzed.Research results show that silicon carbide whiskers can reduce the microcracks caused by the shrinkage of cristobalite.During the sintering process,some of the silicon carbide whiskers oxidize and react with aluminum powder to form mullite,which can improve the high-temperature strength of the ceramic cores.When the content of silicon carbide whiskers is 3wt.%,the high-temperature bending strength of the cores reaches the maximum value of 21 MPa.Silicon nitride whiskers decompose in a high-temperature environment and react with aluminum powder in the matrix material to form mullite whiskers.When the content of silicon nitride whiskers is 5wt.%,the high-temperature bending strength of the cores reaches 20 MPa.By adding mullite whiskers,a structure of cristobalite wrapped mullite whiskers can be formed to achieve toughening.When the content of mullite whiskers is 4wt.%,the high-temperature bending strength can reach 17.2 MPa.By comparing the performance of silicon carbide whiskers,silicon nitride whiskers,and mullite whiskers,along with conducting slurry viscosity tests and casting experiments,it is determined that a ceramic slurry containing 4wt.%mullite whiskers is the most suitable for making the cores used in the integrated casting of hollow turbine blades.
基金supported by the National Natural Science Foundation of China(No.52175284)the National Key Research and Development Program of China(Grant No.2022YFB3404201).
文摘This study investigates the formation feasibility of the integrated bottom car body components with dual die casting injection molding technology.During the production of a die-cast super-large one-piece body part weighing over 10,000 t,a thorough comparison and investigation were conducted on the arising issues,using both single and double injection systems.Particular attention was given to meticulously discussing the die casting filling problems and microstructural defects that originated from the filling process.The research findings indicate that the implementation of a double injection system can significantly minimize cold shuts and reduce the solidification time.The effectiveness of this die casting technique was further confirmed by the production of high-quality castings using a scaled model that replicated real casting conditions at a 1:3 ratio,thereby maintaining a one-to-one correspondence in essential aspects.This successful study offers both theoretical insights and practical applications for the production of integrated bottom car bodies utilizing die casting in conjunction with a dual injection system.
基金Supported by the National Natural Science Foundation of China(Nos.52222904 and 52309117)China Postdoctoral Science Foundation(Nos.2022TQ0168 and 2023M731895).
文摘Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.
