A new stirring method,reciprocating stirring,is developed by incorporating a periodic axial reciprocating motion into conventional stirring.This study employs computational fluid dynamics methods,utilizing volume of f...A new stirring method,reciprocating stirring,is developed by incorporating a periodic axial reciprocating motion into conventional stirring.This study employs computational fluid dynamics methods,utilizing volume of fluid and user-defined functions to control and analyze the flow field characteristics in a reciprocating stirred tank.Compared to conventional stirring,reciprocating stirring increases the overall fluid velocity by approximately 7.9%,turbulent kinetic energy(TKE)by 35.9%to 45.6%,and the turbulent dissipation rate by 10.6%to 15.7%.The primary reason is the dynamic integration of multiple flow regions,which enhances fluid interface interactions.Additionally,the study investigates the dynamic evolution of the vortex structure,uncovering the correlation between the impeller's start-stop behavior and the vortex area.The optimal impeller plate designs,forward sine-4/12D and reverse sine-5/12D,were determined based on the effective area of TKE.Reciprocating stirring,in comparison to conventional stirring,enhances secondary flow intensity by 67.3%to 93.7%and shortens mixing time by 56.6%to 173.0%.展开更多
This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault dia...This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault diagnosis of a reciprocating compressor(RC).Initially,raw vibration signals undergo empirical mode decomposition to break them down into multiple intrinsic mode functions(IMFs).This operation can reveal inherent vibration patterns of fault and other components hidden in the original signals.Subsequently,features are refined from all the IMFs and concatenated into a high-dimensional representative vector,offering localized and comprehensive insights into RC operation.Through DBN,the fault-sensitive information is further refined from the features to enhance their performance in fault identification.Finally,similarities among subspaces on the Grassmann manifold are computed to match fault types.The efficacy of the method is validated usingfield data.Comparative analysis with traditional approaches for feature dimension reduction,feature extraction,and Euclidean distance-based fault identification underscores the effectiveness and superiority of the proposed method in RC fault diagnosis.展开更多
To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’...To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’along the spiral trajectory,was proposed.From the kinematics analysis,it is found that the machining quality of micro-dimpled structures is highly dependent on the machining trajectory using spiral trajectory tool reciprocating motion.To reveal this causation,simulation modelling and experimental studies were carried out.A simulation model was developed to quantitatively and qualitatively investigate the influence of the trajectory discretization strategies(constant-angle and constant-arc length)and parameters(discrete angle,discrete arc length,and pitch)on surface texture and residual height of micro-dimpled structures.Subsequently,micro-dimpled structures were milled under different trajectory discretization strategies and parameters with spiral trajectory tool reciprocating motion.A comprehensive comparison between the milled results and simulation analysis was made based on geometry accuracy,surface morphology and surface roughness of milled dimples.Meanwhile,the errors and factors affecting the above three aspects were analyzed.The results demonstrate both the feasibility of the established simulation model and the machining capability of this machining way in milling high-quality micro-dimpled structures.Spiral trajectory tool reciprocating motion provides a new machining way for milling micro-dimpled structures and micro-dimpled functional surfaces.And an appropriate machining trajectory can be generated based on the optimized trajectory parameters,thus contributing to the improvement of machining quality and efficiency.展开更多
The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy ...The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy structural components.In this work,the combined loading of reciprocating free-end torsion(FET)and free-rotational tension(FRT)was performed on the extruded AZ31 solid rod with basal fiber texture.The corresponding mechanical response,microstructure evolution,and twinning behaviors were investigated,and the physical mechanism of the second-order behaviors(both the Swift and inverse Swift effects)was discussed.The results indicate that the two-stage deformation of reciprocating torsion is capable of activating tensile twins,effectively refining the surface grains,and thus improving the yield asymmetry.Due to the reverse load,detwinning dominates the deformation of reverse FET(RFET),while detwinning in FRT deformation is caused by the spontaneous rotation of the inverse Swift effect.The twin variants with c-axis tending to extrusion direction(ED)are predisposed to detwinning,and the bimodal texture introduced by FET is degraded.The plastic deformation of RFET is primarily coordinated by basal and prismatic slips.The large strain FRT is dominated by basal slip due to its low SF/CRSS.The interaction between twinning and detwinning dominates the multi-directionality of the Swift effect during reciprocating torsion,and the cumulative effect of strain hardening further enhances the dependence of RFET axial strain on basal slip.The dγ/dεindex successfully captures the evolution of the inverse Swift effect during FRT.The forward rotation of the solid rod is caused by the inversion of the radial residual shear stress field,and the internal stress introduced by the torsional inhomogeneity is compensated.The subsequent reverse rotation is the result of balancing the orientation inhomogeneity and local strain heterogeneity introduced by the shear deformation.The increase in the reverse rotation rate is caused by detwinning.展开更多
Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion, and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×1...Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion, and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×10^-4 to 3.3×10-2^s^-1. The results show that the alloy has an equiaxed grain structure with an average grain size of about 5.0μm, and the sizes of broken secondary particles and precipitates are no more than 175 and 50 nm, respectively. The alloy exhibits quasi-superplasticity with a maximum elongation of 270% at 523 K and an initial strain rate of 3.3×10^-4 s^-1. The strain rate sensitivity m is less than 0.2 at 443 and 473 K, and it is 0.42 at 523 K. The apparent activation energies at temperature below 473 K and at 523 K are less than 63.2 and 110.6 kJ/mol, respectively At temperature below 473 K, mainly intragranular sliding contributes to superplastic flow. At 523 K, grain boundary sliding is the dominant deformation mechanism, and dislocation creep controlled by grain boundary diffusion is considered to be the main accommodation mechanism.展开更多
Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. On...Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.展开更多
The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valv...The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valve dynamic has not been taken account into thermal cycle computation,the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered.This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation.The valve dynamics equation,gas forces for normal and back flow,and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed.A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation.The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically.The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation.The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor.The experimental results agree with the numerical simulation results,which show that the theoretical models proposed are effective and high-precision.The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.展开更多
This paper presents an application of global sensitivity analysis for system safety analysis of reciprocating aircraft engine. Compared with local sensitivity analysis results, global sensitivity analysis could provid...This paper presents an application of global sensitivity analysis for system safety analysis of reciprocating aircraft engine. Compared with local sensitivity analysis results, global sensitivity analysis could provide more information on parameter inter- actions, which are significant in complex system safety analysis. First, a deterministic aviation reciprocating engine thermody- namics model is developed and parameters of interest are defined as random variables. Then, samples are generated by Monte Carlo method for the parameters used in engine model on the basis of definition of factor distribution. Eventually, results from engine model are generated and importance indices are calculated. Based on the analysis results, design is improved to satisfy the airworthiness requirements. The results reveal that by using global sensitivity analysis, the parameters could be ranked with respect to their importance, including first order indices and total sensitivity indices. By reducing the uncertainty of parameters and adjusting the range of inputs, safety criteria would be satisfied.展开更多
The submersible pumping unit is a new type of pumping system for lifting formation fluids from onshore oil wells, and the identification of its working condition has an important influence on oil production. In this p...The submersible pumping unit is a new type of pumping system for lifting formation fluids from onshore oil wells, and the identification of its working condition has an important influence on oil production. In this paper we proposed a diagnostic method for identifying the working condition of the submersible pumping system. Based on analyzing the working principle of the pumping unit and the pump structure, different characteristics in loading and unloading processes of the submersible linear motor were obtained at different working conditions. The characteristic quantities were extracted from operation data of the submersible linear motor. A diagnostic model based on the support vector machine （SVM） method was proposed for identifying the working condition of the submersible pumping unit, where the inputs of the SVM classifier were the characteristic quantities. The performance and the misjudgment rate of this method were analyzed and validated by the data acquired from an experimental simulation platform. The model proposed had an excellent performance in failure diagnosis of the submersible pumping system. The SVM classifier had higher diagnostic accuracy than the learning vector quantization （LVQ） classifier.展开更多
An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were ...An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were investigated.The results show that SPD occurring in ECRE leads to a mixed microstructure.ECREed 7005 alloy exhibits a significant improvement of ultimate tensile strength(UTS)and elongation.Mechanical properties in the region undergoing a complete ECRE process are higher than those in the region undergoing an incomplete ECRE process due to larger dislocation strengthening effect.Yield strength(YS)and UTS first decrease and then increase with an increase of extrusion temperature.The YS of 359.2 MPa,UTS of 490 MPa and elongation of 17.7%are obtained after T6 treatment.Fine-grain strengthening,dislocation strengthening and precipitation strengthening in the T6-treated ECREed sample all play important roles in improving the mechanical properties.展开更多
The authors have studied the motion mechanism of the magnetic fluid in a reciprocating seal gap,on the basis of which the authors obtain an anti pressure formula of the reciprocating shaft magnetic fluid seal from gen...The authors have studied the motion mechanism of the magnetic fluid in a reciprocating seal gap,on the basis of which the authors obtain an anti pressure formula of the reciprocating shaft magnetic fluid seal from general Navier Stokes equation.In order to verify the correctness of the anti pressure formula,the authors have calculated the magnetic field distribution of seal structure and have gotten the maximum still anti pressure.Finally,the authors have verified the influence of speed and stroke on the seal anti pressure.展开更多
Detailed behaviors of nanoscale textured surfaces during the reciprocating sliding contacts are still unknown although they are widely used in mechanical components to improve tribological characteristics.The current ...Detailed behaviors of nanoscale textured surfaces during the reciprocating sliding contacts are still unknown although they are widely used in mechanical components to improve tribological characteristics.The current research of sliding contacts of textured surfaces mainly focuses on the experimental studies,while the cost is too high.Molecular dynamics(MD)simulation is widely used in the studies of nanoscale single-pass sliding contacts,but the CPU cost of MD simulation is also too high to simulate the reciprocating sliding contacts.In this paper,employing multiscale method which couples molecular dynamics simulation and finite element method,two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated.Four textured surfaces with different texture shapes are designed,and a rigid cylindrical tip is used to slide on these textured surfaces.For different textured surfaces,average potential energies and average friction forces of the corresponding sliding processes are analyzed.The analyzing results show that"running-in"stages are different for each texture,and steady friction processes are discovered for textured surfaces II,III and IV.Texture shape and sliding direction play important roles in reciprocating sliding contacts,which influence average friction forces greatly.This research can help to design textured surfaces to improve tribological behaviors in nanoscale reciprocating sliding contacts.展开更多
Single cell temperature difference of lithium-ion battery(LIB) module will significantly affect the safety and cycle life of the battery. The reciprocating air-flow module created by a periodic reversal of the air flo...Single cell temperature difference of lithium-ion battery(LIB) module will significantly affect the safety and cycle life of the battery. The reciprocating air-flow module created by a periodic reversal of the air flow was investigated in an effort to mitigate the inherent temperature gradient problem of the conventional battery system with a unidirectional coolant flow with computational fluid dynamics(CFD). Orthogonal experiment and optimization design method based on computational fluid dynamics virtual experiments were developed. A set of optimized design factors for the cooling of reciprocating air flow of LIB thermal management was determined. The simulation experiments show that the reciprocating flow can achieve good heat dissipation, reduce the temperature difference, improve the temperature homogeneity and effectively lower the maximal temperature of the modular battery. The reciprocating flow improves the safety, long-term performance and life span of LIB.展开更多
Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on ...Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 ℃ and decreasing by 10 ℃ for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.展开更多
A multi-point flexible straightening process characterized by reciprocating bending is proposed.Specifically,the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical...A multi-point flexible straightening process characterized by reciprocating bending is proposed.Specifically,the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical experiments of the straightening of a series of metal profiles with different materials and initial shapes.Further,the relationship between the bending radius and the times of reciprocating bending required to unify the curvature is discussed,and the distribution of residual stress after straightening is analyzed.The results show that the reciprocating bending process can eliminate the difference of the initial curvature,make the curvature of each section tend to be uniform;the times of reciprocating bending to reach the uniform curvature decreases with the decrease of bending radius.The straightness of the straightened profile obtained from the experiment and simulation is less than 0.2%,demonstrating a good feasibility of this method.展开更多
An integrated dynamic model of China＇s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is bu...An integrated dynamic model of China＇s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control.展开更多
As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the r...As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the reciprocating Langmuir four-tip probe, which has been built and operated as the primary diagnostic tool in the boundary of J-TEXT tokamak. In this paper, spatial profiles of the plasma-edge parameters are obtained, such as electron temperature, plasma density, plasma potential, poloidal electric field and their fluctuations. The results indicate the existence of a Er ×BT shear layer at the vicinity of last closed flux surface （LCFS）, with the fluctuations suppressed in varying degrees. The turbulence-induced particle and energy fluxes can be calculated by the local plasma parameters above. Convection dominates the cross-field turbulent transport in boundary plasma. Electrostatic fluctuations properties are also studied in detail with the help of numerical analysis. Statistical analysis on density fluctuation shows that, the intermittency can affect the turbulence in the scrape-off layer （SOL）.展开更多
Continuous biodiesel production from a waste pig-roasting lard,methanol and KOH was carried out in a reciprocating plate reactor(RPR)using a factorial design containing three process factors,namely methanol/lard molar...Continuous biodiesel production from a waste pig-roasting lard,methanol and KOH was carried out in a reciprocating plate reactor(RPR)using a factorial design containing three process factors,namely methanol/lard molar ratio,catalyst loading,and normalized height of the reactor.The main goals were to optimize the influential process factors with respect to biodiesel purity using the response surface methodology and to model the kinetics of the transesterification reaction in order to describe the change of triacylglycerols(TAG)and fatty acid methyl esters(FAME)concentrations along the RPR height.The first-order rate law was proved for both the reaction and the mass transfer.The model of the changing reaction mechanism and mass transfer of TAG was also applicable.Both kinetic models agreed with the experimental concentrations of TAG and FAME determined along the RPR height.展开更多
Sealing performance of the reciprocating seals on a larger diameter (100 mmin diameter) axial piston is theoretically investigated. Based on the characteristics of theclearance flow between the seal and the piston, re...Sealing performance of the reciprocating seals on a larger diameter (100 mmin diameter) axial piston is theoretically investigated. Based on the characteristics of theclearance flow between the seal and the piston, reasonable boundary conditions for Navier-Stokesequations are determined and the equations are modified, so that the final equations can describethe real flow state of the clearance flow. Through combining the final equations with finite elementmethod, the pressure distributions within the clearance field during the reciprocating motion ofthe piston and the leakage rate with the pressure are studied. The deflections of the seal whichaffect sealing performance are calculated as well. Sealing performance of piston seals using oil asthe working liquid is compared with using water. It is concluded that the seal using water as theworking liquid is under dry friction, which cannot be dealt with the theory of fluid mechanics. Theseal structure is only acceptable using oil as the working liquid..展开更多
Reciprocating engines and their fuels are largely associated with road transport. This isn’t surprising. About 70% of transport-sector greenhouse gas emissions today are from road vehicles [1], and these vehicles are...Reciprocating engines and their fuels are largely associated with road transport. This isn’t surprising. About 70% of transport-sector greenhouse gas emissions today are from road vehicles [1], and these vehicles are overwhelmingly propelled by reciprocating engines. However, reciprocating engines are also widely used in other sectors, particularly off-road land transport, sea transport, and electrical power generation.展开更多
基金National Key Research and Development Program of China(2022YFC3902000)Yunnan Major Scientific and Technological Projects(202202AG050002,202202AG050007)National Natural Science Foundation of China(52166004).
文摘A new stirring method,reciprocating stirring,is developed by incorporating a periodic axial reciprocating motion into conventional stirring.This study employs computational fluid dynamics methods,utilizing volume of fluid and user-defined functions to control and analyze the flow field characteristics in a reciprocating stirred tank.Compared to conventional stirring,reciprocating stirring increases the overall fluid velocity by approximately 7.9%,turbulent kinetic energy(TKE)by 35.9%to 45.6%,and the turbulent dissipation rate by 10.6%to 15.7%.The primary reason is the dynamic integration of multiple flow regions,which enhances fluid interface interactions.Additionally,the study investigates the dynamic evolution of the vortex structure,uncovering the correlation between the impeller's start-stop behavior and the vortex area.The optimal impeller plate designs,forward sine-4/12D and reverse sine-5/12D,were determined based on the effective area of TKE.Reciprocating stirring,in comparison to conventional stirring,enhances secondary flow intensity by 67.3%to 93.7%and shortens mixing time by 56.6%to 173.0%.
文摘This paper introduces a new method based on deep belief networks(DBNs)to integrate intrinsic vibration information and assess the similarity of subspaces established on the Grassmann manifold for intelligent fault diagnosis of a reciprocating compressor(RC).Initially,raw vibration signals undergo empirical mode decomposition to break them down into multiple intrinsic mode functions(IMFs).This operation can reveal inherent vibration patterns of fault and other components hidden in the original signals.Subsequently,features are refined from all the IMFs and concatenated into a high-dimensional representative vector,offering localized and comprehensive insights into RC operation.Through DBN,the fault-sensitive information is further refined from the features to enhance their performance in fault identification.Finally,similarities among subspaces on the Grassmann manifold are computed to match fault types.The efficacy of the method is validated usingfield data.Comparative analysis with traditional approaches for feature dimension reduction,feature extraction,and Euclidean distance-based fault identification underscores the effectiveness and superiority of the proposed method in RC fault diagnosis.
基金co-supported the National Natural Science Foundation of China(No.52235010)the Heilongjiang Postdoctoral Fund(No.LBH-Z22136)the New Era Longjiang Excellent Master and Doctoral Dissertation Fund(No.LJYXL2022-057).
文摘To mill fine and well-defined micro-dimpled structures,a machining manner of spiral trajectory tool reciprocating motion,where the tool repeats the process of‘feed milling–retract–cutting feed–feed milling again’along the spiral trajectory,was proposed.From the kinematics analysis,it is found that the machining quality of micro-dimpled structures is highly dependent on the machining trajectory using spiral trajectory tool reciprocating motion.To reveal this causation,simulation modelling and experimental studies were carried out.A simulation model was developed to quantitatively and qualitatively investigate the influence of the trajectory discretization strategies(constant-angle and constant-arc length)and parameters(discrete angle,discrete arc length,and pitch)on surface texture and residual height of micro-dimpled structures.Subsequently,micro-dimpled structures were milled under different trajectory discretization strategies and parameters with spiral trajectory tool reciprocating motion.A comprehensive comparison between the milled results and simulation analysis was made based on geometry accuracy,surface morphology and surface roughness of milled dimples.Meanwhile,the errors and factors affecting the above three aspects were analyzed.The results demonstrate both the feasibility of the established simulation model and the machining capability of this machining way in milling high-quality micro-dimpled structures.Spiral trajectory tool reciprocating motion provides a new machining way for milling micro-dimpled structures and micro-dimpled functional surfaces.And an appropriate machining trajectory can be generated based on the optimized trajectory parameters,thus contributing to the improvement of machining quality and efficiency.
基金supported by the National Natural Science Foundation of China(Nos.51771166,52225101)Fundamental Research Funds for the Central Universities(No.2023CDJYXTD-002)+1 种基金Cultivation Project for Basic Research and In-novation of Yanshan University(No.2021LGZD002)Project of State Key Laboratory of Materials Processing and Die&Mould Technology(No.P2023-004).
文摘The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy structural components.In this work,the combined loading of reciprocating free-end torsion(FET)and free-rotational tension(FRT)was performed on the extruded AZ31 solid rod with basal fiber texture.The corresponding mechanical response,microstructure evolution,and twinning behaviors were investigated,and the physical mechanism of the second-order behaviors(both the Swift and inverse Swift effects)was discussed.The results indicate that the two-stage deformation of reciprocating torsion is capable of activating tensile twins,effectively refining the surface grains,and thus improving the yield asymmetry.Due to the reverse load,detwinning dominates the deformation of reverse FET(RFET),while detwinning in FRT deformation is caused by the spontaneous rotation of the inverse Swift effect.The twin variants with c-axis tending to extrusion direction(ED)are predisposed to detwinning,and the bimodal texture introduced by FET is degraded.The plastic deformation of RFET is primarily coordinated by basal and prismatic slips.The large strain FRT is dominated by basal slip due to its low SF/CRSS.The interaction between twinning and detwinning dominates the multi-directionality of the Swift effect during reciprocating torsion,and the cumulative effect of strain hardening further enhances the dependence of RFET axial strain on basal slip.The dγ/dεindex successfully captures the evolution of the inverse Swift effect during FRT.The forward rotation of the solid rod is caused by the inversion of the radial residual shear stress field,and the internal stress introduced by the torsional inhomogeneity is compensated.The subsequent reverse rotation is the result of balancing the orientation inhomogeneity and local strain heterogeneity introduced by the shear deformation.The increase in the reverse rotation rate is caused by detwinning.
基金Project (50271054) supported by National Natural Science Foundation of ChinaProject (20070700003) supported by Ph.D. Programs Foundation of Ministry of Education of China+1 种基金Project (102102210031) supported by Science and Technologies Foundation of Henan,ChinaProject (2010A430008) supported by Natural Science Foundation of Henan Educational Committee,China
文摘Fine-grained ZK60 alloy was prepared by 2-pass reciprocating extrusion, and the low temperature superplasticity was conducted in a temperature range from 443 to 523 K and an initial strain rate ranging from 3.3×10^-4 to 3.3×10-2^s^-1. The results show that the alloy has an equiaxed grain structure with an average grain size of about 5.0μm, and the sizes of broken secondary particles and precipitates are no more than 175 and 50 nm, respectively. The alloy exhibits quasi-superplasticity with a maximum elongation of 270% at 523 K and an initial strain rate of 3.3×10^-4 s^-1. The strain rate sensitivity m is less than 0.2 at 443 and 473 K, and it is 0.42 at 523 K. The apparent activation energies at temperature below 473 K and at 523 K are less than 63.2 and 110.6 kJ/mol, respectively At temperature below 473 K, mainly intragranular sliding contributes to superplastic flow. At 523 K, grain boundary sliding is the dominant deformation mechanism, and dislocation creep controlled by grain boundary diffusion is considered to be the main accommodation mechanism.
基金supported by National Basic Research Program of China(973 Program,Grant No. 2009CB724304)Key Research Program of the State Key Laboratory of Tribology of Tsinghua University,China (Grant No. SKLT08A06)National Natural Science Foundation of China(Grant No. 50975157)
文摘Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.
基金supported by China National Key Technology R&D Program(Grant No.2008BAF34B13)China Postdoctoral Science Foundation Funded Project(Grant No.2011M501363)
文摘The existing researches of stepless capacity regulation system by depressing the suction valve for reciprocation compressor always adopt hypothesis that the compressor valves are open or close instantaneously,the valve dynamic has not been taken account into thermal cycle computation,the influence of capacity regulation system on suction valves dynamic performance and cylinder thermal cycle operation has not been considered.This paper focuses on theoretical and experimental analysis of the valve dynamic and thermal cycle for reciprocating compressor in the situation of stepless capacity regulation.The valve dynamics equation,gas forces for normal and back flow,and the cylinder pressure varying with suction valve unloader moment during compression thermal cycle are discussed.A new valve dynamic model based on L-K real gas state equation for reciprocating compressor is first deduced to reduce the calculation errors induced by the ideal gas state equation.The variations of valve dynamic and cylinder pressure during part of compression stroke are calculated numerically.The calculation results reveal the non-normal thermal cycle and operation condition of compressor in stepless capacity regulation situation.The numerical simulation results of the valve dynamic and thermal cycle parameters are also verified by the stepless capacity regulation experiments in the type of 3L-10/8 reciprocating compressor.The experimental results agree with the numerical simulation results,which show that the theoretical models proposed are effective and high-precision.The proposed theoretical models build the theoretical foundation to design the real stepless capacity regulation system.
基金Innovation Plan of Aero Engine Complex System Safety by the Ministry of Education Chang Jiang Scholars of China (IRT0905)
文摘This paper presents an application of global sensitivity analysis for system safety analysis of reciprocating aircraft engine. Compared with local sensitivity analysis results, global sensitivity analysis could provide more information on parameter inter- actions, which are significant in complex system safety analysis. First, a deterministic aviation reciprocating engine thermody- namics model is developed and parameters of interest are defined as random variables. Then, samples are generated by Monte Carlo method for the parameters used in engine model on the basis of definition of factor distribution. Eventually, results from engine model are generated and importance indices are calculated. Based on the analysis results, design is improved to satisfy the airworthiness requirements. The results reveal that by using global sensitivity analysis, the parameters could be ranked with respect to their importance, including first order indices and total sensitivity indices. By reducing the uncertainty of parameters and adjusting the range of inputs, safety criteria would be satisfied.
文摘The submersible pumping unit is a new type of pumping system for lifting formation fluids from onshore oil wells, and the identification of its working condition has an important influence on oil production. In this paper we proposed a diagnostic method for identifying the working condition of the submersible pumping system. Based on analyzing the working principle of the pumping unit and the pump structure, different characteristics in loading and unloading processes of the submersible linear motor were obtained at different working conditions. The characteristic quantities were extracted from operation data of the submersible linear motor. A diagnostic model based on the support vector machine （SVM） method was proposed for identifying the working condition of the submersible pumping unit, where the inputs of the SVM classifier were the characteristic quantities. The performance and the misjudgment rate of this method were analyzed and validated by the data acquired from an experimental simulation platform. The model proposed had an excellent performance in failure diagnosis of the submersible pumping system. The SVM classifier had higher diagnostic accuracy than the learning vector quantization （LVQ） classifier.
基金This work is supported by the National Natural Science Foundation of China(51875124).
文摘An equal channel reciprocating extrusion(ECRE)was proposed first to obtain a severe plastic deformation(SPD)of 7005 alloy.The microstructure and mechanical properties of one-pass ECREed(ECRE processed)7005 alloy were investigated.The results show that SPD occurring in ECRE leads to a mixed microstructure.ECREed 7005 alloy exhibits a significant improvement of ultimate tensile strength(UTS)and elongation.Mechanical properties in the region undergoing a complete ECRE process are higher than those in the region undergoing an incomplete ECRE process due to larger dislocation strengthening effect.Yield strength(YS)and UTS first decrease and then increase with an increase of extrusion temperature.The YS of 359.2 MPa,UTS of 490 MPa and elongation of 17.7%are obtained after T6 treatment.Fine-grain strengthening,dislocation strengthening and precipitation strengthening in the T6-treated ECREed sample all play important roles in improving the mechanical properties.
基金National Natural Science F oundation of China(No.59705004)
文摘The authors have studied the motion mechanism of the magnetic fluid in a reciprocating seal gap,on the basis of which the authors obtain an anti pressure formula of the reciprocating shaft magnetic fluid seal from general Navier Stokes equation.In order to verify the correctness of the anti pressure formula,the authors have calculated the magnetic field distribution of seal structure and have gotten the maximum still anti pressure.Finally,the authors have verified the influence of speed and stroke on the seal anti pressure.
基金Supported by National Natural Science Foundation of China(Grant Nos.51205313,50975232)Fundamental Research Funds for the Central Universities of China(Grant No.3102014JCS05009)the 111 Project of China(Grant No.B13044)
文摘Detailed behaviors of nanoscale textured surfaces during the reciprocating sliding contacts are still unknown although they are widely used in mechanical components to improve tribological characteristics.The current research of sliding contacts of textured surfaces mainly focuses on the experimental studies,while the cost is too high.Molecular dynamics(MD)simulation is widely used in the studies of nanoscale single-pass sliding contacts,but the CPU cost of MD simulation is also too high to simulate the reciprocating sliding contacts.In this paper,employing multiscale method which couples molecular dynamics simulation and finite element method,two dimensional nanoscale reciprocating sliding contacts of textured surfaces are investigated.Four textured surfaces with different texture shapes are designed,and a rigid cylindrical tip is used to slide on these textured surfaces.For different textured surfaces,average potential energies and average friction forces of the corresponding sliding processes are analyzed.The analyzing results show that"running-in"stages are different for each texture,and steady friction processes are discovered for textured surfaces II,III and IV.Texture shape and sliding direction play important roles in reciprocating sliding contacts,which influence average friction forces greatly.This research can help to design textured surfaces to improve tribological behaviors in nanoscale reciprocating sliding contacts.
基金Project(50803008)supported by the National Natural Science Foundation of ChinaProjects(14JJ4035,2011RS4067)supported by the Natural Science Foundation of Hunan Province,China+1 种基金Project(2013-sdllmd-08)supported by the State Key Laboratory of Luminescent Materials and Devices(South China University of Technology),ChinaProjects(20100480946,201104508)supported by the China Postdoctoral Science Foundation,China
文摘Single cell temperature difference of lithium-ion battery(LIB) module will significantly affect the safety and cycle life of the battery. The reciprocating air-flow module created by a periodic reversal of the air flow was investigated in an effort to mitigate the inherent temperature gradient problem of the conventional battery system with a unidirectional coolant flow with computational fluid dynamics(CFD). Orthogonal experiment and optimization design method based on computational fluid dynamics virtual experiments were developed. A set of optimized design factors for the cooling of reciprocating air flow of LIB thermal management was determined. The simulation experiments show that the reciprocating flow can achieve good heat dissipation, reduce the temperature difference, improve the temperature homogeneity and effectively lower the maximal temperature of the modular battery. The reciprocating flow improves the safety, long-term performance and life span of LIB.
基金financially supported by the Natural Science Foundation of Shanxi Province (No. 201901D111176)the Joint Funds of the National Natural Science Foundation of china (Grant No. U20A20230)+3 种基金the Bureau of science, technology and industry for National Defense of China (No. WDZC2019JJ006)the Key R&D program of Shanxi Province (International Cooperation) (No. 201903D421036)the National Natural Science Foundation of China (Grant No. 52075501)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (No. 2018002)。
文摘Based on the deforming technique of severe plastic deformation(SPD), the grain refinement of a Mg-9Gd-3Y-2Zn-0.5Zr alloy treated with decreasing temperature reciprocating upsetting-extrusion(RUE) and its influence on the mechanical properties and wear behavior of the alloy were studied. The RUE process was carried out for 4 passes in total, starting at 0 ℃ and decreasing by 10 ℃ for each pass. The results showed that as the number of RUE passes increased, the grain refinement effect was obvious, and the second phase in the alloy was evenly distributed. Room temperature tensile properties of the alloy and the deepening of the RUE degree showed a positive correlation trend, which was due to the grain refinement, uniform distribution of the second phase and texture weakening. And the microhardness of the alloy showed that the microhardness of RUE is the largest in 2 passes. The change in microhardness was the result of dynamic competition between the softening effect of DRX and the work hardening effect. In addition, the wear resistance of the alloy showed a positive correlation with the degree of RUE under low load conditions. When the applied load was higher, the wear resistance of the alloy treated with RUE decreased compared to the initial state alloy. This phenomenon was mainly due to the presence of oxidative wear on the surface of the alloy, which could balance the positive contribution of severe plastic deformation to wear resistance to a certain extent.
基金financially supported by the National Natural Science Foundation of China(No.52005431)the National Natural Science Foundation of Hebei Province,China(No.E2020203086)the National Major Science and Technology Project of China(No.2018ZX04007002).
文摘A multi-point flexible straightening process characterized by reciprocating bending is proposed.Specifically,the process is analyzed in terms of deformation mechanism and verified by numerical simulations and physical experiments of the straightening of a series of metal profiles with different materials and initial shapes.Further,the relationship between the bending radius and the times of reciprocating bending required to unify the curvature is discussed,and the distribution of residual stress after straightening is analyzed.The results show that the reciprocating bending process can eliminate the difference of the initial curvature,make the curvature of each section tend to be uniform;the times of reciprocating bending to reach the uniform curvature decreases with the decrease of bending radius.The straightness of the straightened profile obtained from the experiment and simulation is less than 0.2%,demonstrating a good feasibility of this method.
基金supported by the National Natural Science Foundation of China(Grant No.51105386)the National Deep-Sea Technology Project of Development and Research(Grant No.DYXM-115-04-02-01)the Fundamental Research Funds for the Central Universities(Grant No.2011QNZT058)
文摘An integrated dynamic model of China＇s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control.
基金supported by Open Research Program from Key Laboratory of Geospace Environment, Chinese Academy of Sciences
文摘As the basic of a deeper investigation on the turbulent transport, the fluctuation property in the boundary of the newly-reconstructed Joint Texas Experimental Tokamak （J- TEXT） is studied experimentally using the reciprocating Langmuir four-tip probe, which has been built and operated as the primary diagnostic tool in the boundary of J-TEXT tokamak. In this paper, spatial profiles of the plasma-edge parameters are obtained, such as electron temperature, plasma density, plasma potential, poloidal electric field and their fluctuations. The results indicate the existence of a Er ×BT shear layer at the vicinity of last closed flux surface （LCFS）, with the fluctuations suppressed in varying degrees. The turbulence-induced particle and energy fluxes can be calculated by the local plasma parameters above. Convection dominates the cross-field turbulent transport in boundary plasma. Electrostatic fluctuations properties are also studied in detail with the help of numerical analysis. Statistical analysis on density fluctuation shows that, the intermittency can affect the turbulence in the scrape-off layer （SOL）.
基金Supported by the Ministry of Education,Science and Technological Development of the Republic of Serbia(ProjectⅢ45001)the Project 0-14-18 of the SASA Branch in Nis,Serbia.
文摘Continuous biodiesel production from a waste pig-roasting lard,methanol and KOH was carried out in a reciprocating plate reactor(RPR)using a factorial design containing three process factors,namely methanol/lard molar ratio,catalyst loading,and normalized height of the reactor.The main goals were to optimize the influential process factors with respect to biodiesel purity using the response surface methodology and to model the kinetics of the transesterification reaction in order to describe the change of triacylglycerols(TAG)and fatty acid methyl esters(FAME)concentrations along the RPR height.The first-order rate law was proved for both the reaction and the mass transfer.The model of the changing reaction mechanism and mass transfer of TAG was also applicable.Both kinetic models agreed with the experimental concentrations of TAG and FAME determined along the RPR height.
基金This project is supported by National Natural Science Foundation of China(No.50005019).
文摘Sealing performance of the reciprocating seals on a larger diameter (100 mmin diameter) axial piston is theoretically investigated. Based on the characteristics of theclearance flow between the seal and the piston, reasonable boundary conditions for Navier-Stokesequations are determined and the equations are modified, so that the final equations can describethe real flow state of the clearance flow. Through combining the final equations with finite elementmethod, the pressure distributions within the clearance field during the reciprocating motion ofthe piston and the leakage rate with the pressure are studied. The deflections of the seal whichaffect sealing performance are calculated as well. Sealing performance of piston seals using oil asthe working liquid is compared with using water. It is concluded that the seal using water as theworking liquid is under dry friction, which cannot be dealt with the theory of fluid mechanics. Theseal structure is only acceptable using oil as the working liquid..
文摘Reciprocating engines and their fuels are largely associated with road transport. This isn’t surprising. About 70% of transport-sector greenhouse gas emissions today are from road vehicles [1], and these vehicles are overwhelmingly propelled by reciprocating engines. However, reciprocating engines are also widely used in other sectors, particularly off-road land transport, sea transport, and electrical power generation.
