High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate tor...High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.展开更多
Longitudinal vibration,torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system.However,these vibrations of the propeller-crankshaft-sliding bearing system ...Longitudinal vibration,torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system.However,these vibrations of the propeller-crankshaft-sliding bearing system generated by the fluid exciting force on the propeller are much more complex.Currently,the torsional and longitudinal vibrations have been studied separately while the research on their coupled vibration is few,and the influence of the propeller structure to dynamic characteristics of a crankshaft has not been studied yet.In order to describe the dynamic properties of a crankshaft accurately,a nonlinear dynamic model is proposed taking the effect of torsional-longitudinal coupling and the variable inertia of propeller,connecting rod and piston into account.Numerical simulation cases are carried out to calculate the response data of the system in time and frequency domains under the working speed and over-speed,respectively.Results of vibration analysis of the propeller and crankshaft system coupled in torsional and longitudinal direction indicate that the system dynamic behaviors are relatively complicated especially in the components of the frequency response.For example,the 4 times of an exciting frequency acting on the propeller by fluid appears at 130 r/min,while not yield at 105 r/min.While the possible abnormal vibration at over-speed just needs to be vigilant.So when designing the propeller shafting used in marine diesel engines,strength calculation and vibration analysis based only on linear model may cause great errors and the proposed research provides some references to design diesel engine propeller shafting used in large marines.展开更多
Because of propeller hydrodynamic influence, the shafting vibration is a coupled vibration which includes torsional, longitudinal and whirling vibrations. It is unsuitable to analyze different vibrations of propulsive...Because of propeller hydrodynamic influence, the shafting vibration is a coupled vibration which includes torsional, longitudinal and whirling vibrations. It is unsuitable to analyze different vibrations of propulsive shafting systems with development of shipbuilding technologies. To overcome the shortages of traditional marine standards, we establish a new numerical model of the shafting coupled vibration. And we put forward shafting coupled vibration calculation to ensure better reliability of main propulsion system. The shafting system is modeled into two sub-systems, a continuous one and a discrete one. Wave approach and transit matrix method are used to investigate displacement and stress fields in continuous and discrete sub-systems, respectively. And vibrations of different modes in both sub-systems are coupled by using dynamic equilibrium and continuity condition to deduce the global equations governing the motion of shafting. The coupling calculation is then used to research the reason of a very large crude carrier(VLCC) stern hull vibration. It is shown by the comparison of the results from both coupling and dependent vibration calculations that vibration in deferent directions will cause deformation in the same mode, which leads to extra stress and displacements on shafting, especially as the resonant frequencies of different vibration modes match each other. This is helpful to prevent ship stern vibration due to poor shafting vibration calculation.展开更多
With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of...With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of propeller shafts has been done under increasing rudder corner conditions with complex hydrodynamics simulation for a great domestic liquified natural gas(LNG) vessel,which is with dual propulsion systems.The improved three-moment equation is adopted in the process of dual propulsive shafting alignment.The calculated results show that the propeller hydrodynamic characteristics,which affect dual propulsive shafting alignment greatly,must be considered under large rudder angle conditions.Shafting accidents of Korean LNG vessels are interpreted reasonably.At the same time,salutary lessons and references are afforded to the marine multi-propulsion shafting alignment in the future.展开更多
The shafting vibration is closely related to the rotational angular speed.The angular speed of hydro turbine generating sets(HTGS)is rapidly change in fault transient,it maybe reduce the shafting damage.By means of en...The shafting vibration is closely related to the rotational angular speed.The angular speed of hydro turbine generating sets(HTGS)is rapidly change in fault transient,it maybe reduce the shafting damage.By means of energy analysis,the differential equation of shafting vibration for the HTGS is derived,in which include the equation of generator rotor and hydro turbine runner,it can be applied to transient analysis.Shafting model is transformed into first order differential equation groups,and is combined with the motion equation of HTGS to build integrated model.Various additional forces of shafting are taken as input inspire in proposed model,the generality of model is good.At last,the shafting vibration in emergency stop transient is simulated.展开更多
This paper aims at investigating the effectiveness of squeeze oil film in suppressing the longitudinal vibration of propulsion shaft systems through a novel integral axial squeeze film damper(IASFD).After designing th...This paper aims at investigating the effectiveness of squeeze oil film in suppressing the longitudinal vibration of propulsion shaft systems through a novel integral axial squeeze film damper(IASFD).After designing the IASFD,a propulsion shafting test rig for the longitudinal vibration control is built.Longitudinal vibration control experiments of the propulsion shafting are carried out under different magnitude and frequency of the excitation force.The results show that both IASFD elastic support and IASFD elastic damping support have excellent vibration attenuation characteristics,and can effectively suppress the longitudinal vibration of the shaft system in a wide frequency range.However,IASFD elastic damping support has a more significant vibration reduction effect than the other supports,and increasing the damping of the system has obvious effect on reducing the shafting vibration.For an excitation force of 45 N,the maximum reduction of the vibration amplitude is 89.16%.Also,the vibration generated by the resonance phenomenon is also significantly reduced.展开更多
According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearin...According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearings in two-dimensional space are established,and a coupling mathematical model of the marine propulsion shafting in steady operating state is proposed.Then the simulation of a real ship is carried out,and the variation laws of some special parameters such as bearing load and deflection are obtained.Finally,the results of simulation are verified by experimental data of a real ship,which can provide the mathematical model and analysis method for the research on the characteristics of ship propulsion shafting condition in steady state.展开更多
Shafting vibration has been a problem of 660MW steam turbine of SAIC in a power plant since it was put into operation. Through long-term tracking and in-depth analysis of the unit and combined with the opportunity of ...Shafting vibration has been a problem of 660MW steam turbine of SAIC in a power plant since it was put into operation. Through long-term tracking and in-depth analysis of the unit and combined with the opportunity of a repair of the unit, find out the causes of shafting vibration, verify and deal with them one by one, and eliminate poor spherical contact of main engine #3 bearing, #4 bearing seat and foundation void. There are some problems, such as the breakage of the generator seal pad and the thermal imbalance of the generator rotor, so that the shafting vibration reaches an excellent level.展开更多
The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification metho...The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.展开更多
To enhance the operational capacity and space utilization of baffle-drop shafts,this study improved the traditional baffle-drop shaft by expanding the wet-side space,incorporating large rotation-angle baffles,and inst...To enhance the operational capacity and space utilization of baffle-drop shafts,this study improved the traditional baffle-drop shaft by expanding the wet-side space,incorporating large rotation-angle baffles,and installing overflow holes in the dividing wall.A three-dimensional turbulent model was developed using ANSYS Fluent to simulate the hydraulic characteristics of both traditional and new baffle-drop shafts across various flow rates.The simulation results demonstrated that the new shaft design allowed for discharge from both the wet and dry sides,significantly improving operational capacity,with the dry side capable of handling 40%of the inlet flow.Compared to the traditional shaft,the new design reduced shaft wall pressures and decreased the mean and standard deviation of pressure on typical baffles by 21%and 63%,respectively,therefore enhancing structural safety.Additionally,the new shaft achieved a 2%-12%higher energy dissipation rate than the traditional shaft across different flow rates.This study offers valuable insights for the design and optimization of drop shafts in deep tunnel drainage systems.展开更多
To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellen...To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellent corrosion resistance,was introduced.A novel method for manufacturing these composite shaft parts using cross-wedge rolling(CWR)was proposed and explored.Thermal simulation experiments,CWR forming trials and finite element analysis were conducted to examine the coordinated deformation during the CWR process.The results revealed a downhill diffusion pattern of elements from higher to lower-concentration areas,forming a smooth and uniform concentration gradient.When the cladding thickness(CT)ranged from 3 to 4 mm,the trajectories of the points on both the cladding material and the substrate coincided,indicating strong bonding at the transitional interface of the composite shaft.Conversely,with a CT of 5 mm,coordinated deformation between the substrate and cladding material was not achieved.Shear strength tests demonstrated a gradual decrease in strength with increasing CT.The microscopic morphology of the interface showed that the metal grains near both sides of the interface were refined,and the binding interface displayed a slightly curved shape.A viable method was provided for producing high-performance corrosion-resistant composite shaft components using CWR technology.展开更多
The self-reforming of coke oven gas(COG)in a gas-based shaft furnace was investigated,employing metallized iron as a catalyst.Thermodynamic analyses,supported by FactSage 8.3 calculations and regression modeling,were ...The self-reforming of coke oven gas(COG)in a gas-based shaft furnace was investigated,employing metallized iron as a catalyst.Thermodynamic analyses,supported by FactSage 8.3 calculations and regression modeling,were used to investigate the effects of temperature(700–1100℃),CO_(2)(3%–10%),and H_(2)O(1%–9%)concentrations on CH_(4) conversion efficiency.Results indicate that CH_(4) conversion exceeds 90%at temperatures above 1000℃,with CO_(2) and H_(2)O concentrations at 9%and 5%,respectively.During the reforming process,introducing CO_(2) provides additional oxygen,facilitating the oxidation of CH_(4),while H_(2)O enhances H_(2) production through the steam reforming pathway.Experimental findings reveal a CH_(4) conversion of 85.83%with a H_(2)/CO ratio of 5.44 at 1050℃.In addition,an optimal H_(2)O concentration of 6%yields the highest CH_(4) conversion of 84.24%,while CO_(2) exhibits minimal effects on promoting the reforming process.Increasing the metallization rate of pellets from 43%to 92%significantly enhances CH_(4) reforming.This is mainly due to the fact that metallized iron is vital in promoting CH_(4) dissociation and improving syngas yield by providing active sites for the redox cycle of CO_(2) and H_(2)O.展开更多
The hydrogen-enriched direct reduction shaft furnace addresses the high CO_(2) emissions associated with the blast furnace process.A discrete element method(DEM)model was introduced to explore how the structure of the...The hydrogen-enriched direct reduction shaft furnace addresses the high CO_(2) emissions associated with the blast furnace process.A discrete element method(DEM)model was introduced to explore how the structure of the diversion cone affects particle descent behavior in a hydrogen-enriched shaft furnace.The results indicated that in the absence of a diversion cone,the descending velocity near the furnace wall zone is significantly lower than that at its center,resulting in a‘V’-shaped burden flow pattern.The discharge velocity has a minor impact on the flow pattern in the shaft furnace.Upon installation of a diversion cone,burden descending velocity becomes more uniform,leading to a‘-’-shaped burden flow pattern.As the bottom of the diversion cone ascends(i.e.,the lower end of the diversion cone is progressively closer to the top),there is an increase in the volume fraction of the dead zone within the shaft furnace.This is particularly evident in the formation of a triangular dead zone at the base of the diversion cone.It is suggested that the lower cone of the bi-conical diversion cone should maintain a sufficient height.展开更多
The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined ...The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.展开更多
To study the use of a shaft support for the auxiliary shaft of the Xi’anshan Iron Mine,in high-stress strata at a depth between 900 and 1000 m,a new type of mold was developed using the physical similarity model test...To study the use of a shaft support for the auxiliary shaft of the Xi’anshan Iron Mine,in high-stress strata at a depth between 900 and 1000 m,a new type of mold was developed using the physical similarity model test method,based on the similarity theory,and an experimental model of the shaft lining and surrounding rock was poured.Two sets of large-scale destructive tests were conducted on the shaft lining and surrounding rock.The deformation and failure laws of the shaft lining and surrounding rock under high ground stress and their ultimate horizontal bearing capacity characteristics were studied,and the safety support characteristics of the shaft lining under the interaction of the shaft lining and surrounding rock were obtained.An experimental study demonstrated that the axial pressure on the shaft wall directly affected its ultimate horizontal bearing capacity of the shaft wall.In designing the shaft wall,the influence of the axial pressure on the stress state of the concrete should be considered,and the vertical pressure should be modified to optimize the utilization of the three-dimensional compressive strength of the concrete.The reliability of the 400-mm C30 concrete shaft wall at a depth of 1000 m in the actual project was verified,and the ultimate horizontal bearing capacity of the shaft wall was obtained for a depth of 1000 m.展开更多
The iron and steel industry,standing as a quintessential manufacture example with high consumption,pollution and emissions,faces significant environmental and sustainable development challenges.Electric arc furnace(EA...The iron and steel industry,standing as a quintessential manufacture example with high consumption,pollution and emissions,faces significant environmental and sustainable development challenges.Electric arc furnace(EAF)steelmaking process mainly uses scrap as raw material and is characterized by environmentally friendly and recyclable process.However,the further development of EAF route in China is limited by the reserve,supply,availability and quality of scrap resource.Direct reduced iron(DRI)is one of typical low-carbon and clean charges,which can effectively make up for the adverse effects caused by the lack of scrap.The physical and chemical properties,classifications,and production technologies of DRI are firstly reviewed.In particular,the reducing gas types,reduction temperature,and reduction mechanism of the DRI production with gas-based shaft furnace(SF)technology are detailed.Considering the crucial role played by DRI application in EAF,the influences of DRI addition on EAF smelting rules and operations including the blending and charging process,heat transfer and melting in molten bath,slag formation operation,refractory corrosion,and slag system evolution are then further discussed.Finally,the comparative analysis and assessment of the consumption level of material and energy as well as the cleaner production both covering the clean chemical composition of molten steel and the clean environment impact in EAF steelmaking with DRI charged are conducted.From perspectives of metallurgical process engineering,a suitable route of hydrogen generation and application(from coke oven gas,methanol,and clean energy power),CO_(2) capture and utilization integrated with SF–EAF process is proposed.In view of the difficulties in large-scale DRI application in EAF,the follow-up work should focus on the investigation of DRI charging and melting,slag system evolution and molten pool reaction rules,as well as the developments of the DRI standardized use technology and intelligent batching and control models.展开更多
BACKGROUND The objective of this study was to evaluate the use of combined parallax-free panoramic X-ray imaging during surgery by enabling the mobile C-arm with minimally invasive plate osteosynthesis(MIPO)in the man...BACKGROUND The objective of this study was to evaluate the use of combined parallax-free panoramic X-ray imaging during surgery by enabling the mobile C-arm with minimally invasive plate osteosynthesis(MIPO)in the management of proximal humeral shaft fractures.AIM To evaluate parallax-free panoramic X-ray images during surgery.METHODS A retrospective series of 17 proximal humeral shaft fractures were treated using combined parallax-free panoramic X-ray imaging during surgery by enabling the mobile C-arm with MIPO.The operating time and radiation exposure time were recorded,and early postoperative physical therapy and partial weight bearing were encouraged.Patients were followed at regular intervals and evaluated radiographically and clinically.RESULTS The mean operating time and radiation time were 73(range,49-95)minutes and 57(range:36-98)seconds,respectively.No complications occurred during the operation.All fractures healed at an average of 16.9(range:15-23)weeks.The average Constant-Murley score for all the patients was 89.5(range:75-100)points.None of the patients showed symptoms of vascular or nerve damage or wound infection.Three months after the operation,none of the patients developed subacromial impingement syndrome.No loosening or fracture of the implants occurred.The frontal and lateral radiographs showed good alignment.CONCLUSION We consider that MIPO with combined parallax-free panoramic X-ray imaging during surgery is an efficient method for treating proximal humeral shaft fractures,and could significantly reduce operative morbidity as well as lower the rate of intra-and postoperative complications.展开更多
Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared t...Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared to functional bracing,particularly in complex cases,while conservative treatment remains viable for low-demand patients.Surgical techniques,including open reduction internal fixation,intramedullary nailing,and minimally invasive plate osteosynthesis,offer trade-offs between anatomic precision and complication risks(e.g.,radial nerve injury vs rotator cuff damage),with over 90%of radial nerve injuries resolving spontaneously.Ultrasound-guided diagnosis(89%sensitivity,95%specificity)optimizes decision-making for nerve entrapment.Individualized treatment selection,prioritizing fracture complexity and patient needs,is critical to balance accelerated rehabilitation with minimized complications.展开更多
Background of the Study: Femoral shaft fracture is the most common pediatric injury requiring hospitalization. For children less than 5 years old, non-surgical approach is recommended. For pediatric patients 5 - 14 ye...Background of the Study: Femoral shaft fracture is the most common pediatric injury requiring hospitalization. For children less than 5 years old, non-surgical approach is recommended. For pediatric patients 5 - 14 years old, the most common mode of treatment is flexible intramedullary nailing with a known complication of pain at post-op site, inflammatory reaction/bursitis at the entry site, superficial and deep infection, knee synovitis, knee stiffness, leg length discrepancy, proximal nail migration, angulation or malunion, delayed and non-union, implant breakage. This study aims to present a rare complication of a femoral fracture fixed with flexible intramedullary nail. Methodology: We report the outcome of a 12-year-old male with peri implant fracture of the left femur. He underwent removal of plates and screws and subsequently fixed with flexible intramedullary nails. Patient was followed up at 1, 3, 7, and 10 months post-operatively. Varus-valgus, sagittal angulation, and limb shortening were measured pre- and post-operatively. Complications were recorded on each visit. Results: Pre-operative varus angulation was 10˚, pro-curvatum of 55˚ with limb shortening of 4 cm. Postoperatively, varus was maintained to 10˚ but pro-curvatum was corrected to 4˚ and limb shortening was reduced to 1 cm. However, after 1 month the varus angulation increased to 30˚ while maintaining sagittal pro-curvatum. Limb shortening also increased to 2 cm. New bone formation started to appear along the mechanical axis of the left femur which is apparent at 3 months post-op and pro-curvatum increased to 20˚. At 7 and 10 months post-op no signs of union was noted at the fracture site but the callus formation along the mechanical axis gradually matured and appeared as a new femoral shaft. Conclusion: Formation of new bone in response to unstable flexible intramedullary fixation in pediatric femoral shaft fracture is a very rare complication.展开更多
Dendritic spines are small protrusions along dendrites that contain most of the excitatory synapses in principal neurons,playing a crucial role in neuronal function by creating a compartmentalized environment for sign...Dendritic spines are small protrusions along dendrites that contain most of the excitatory synapses in principal neurons,playing a crucial role in neuronal function by creating a compartmentalized environment for signal transduction.The plasticity of spine morphologies provides a tunable handle to regulate calcium signal dynamics,allowing rapid regulation of protein expression necessary to establish and maintain synapses(Cornejo et al.,2022).If excitatory inputs were to be located primarily on dendritic shafts,dendrites would frequently short-circuit,preventing voltage signals from propagating(Cornejo et al.,2022).It is thus not surprising that the structural plasticity of dendritic spines is closely linked to synaptic plasticity and memory formation(Berry and Nedivi,2017).While comprehensive in vitro studies have been conducted,in vivo studies that directly tackle the mechanism of dendritic transport and translation in regulating spine plasticity spatiotemporally are limited.展开更多
文摘High-static-low-dynamic stiffness (HSLDS) vibration isolators have been demonstrated to be an effective means of attenuating low-frequency vibrations, and may be utilized for ship shafting applications to mitigate torsional vibration. This paper presents the construction of a highly compact HSLDS torsional vibration isolator by connecting positive and negative stiffness components in paral lel. Based on mechanical model analysis, the restoring torque of negative stiffness components is de rived from their springs and connecting rods, while that of positive stiffness components is obtained through their circular section flexible rods. The quasizero stiffness characteristics of the HSLDS iso lator are achieved through a combination of static structural simulation and experimental test. The tor sional vibration isolation performance is assessed by means of numerical simulation and theory analy sis. Finally, the frequency-sweep vibration test is conducted. The test results indicate that the HSLDS torsional vibration isolator exhibits superior low-frequency isolation performance compared to its linear counterpart, rendering it a promising solution for mitigating low-frequency torsional vi bration in ship shafting.
基金Supported by Shanghai Municipal Commission of Economy and Informatization of China(Grant Nos.201001007,2013000016)
文摘Longitudinal vibration,torsional vibration and their coupled vibration are the main vibration modes of the crankshaft-sliding bearing system.However,these vibrations of the propeller-crankshaft-sliding bearing system generated by the fluid exciting force on the propeller are much more complex.Currently,the torsional and longitudinal vibrations have been studied separately while the research on their coupled vibration is few,and the influence of the propeller structure to dynamic characteristics of a crankshaft has not been studied yet.In order to describe the dynamic properties of a crankshaft accurately,a nonlinear dynamic model is proposed taking the effect of torsional-longitudinal coupling and the variable inertia of propeller,connecting rod and piston into account.Numerical simulation cases are carried out to calculate the response data of the system in time and frequency domains under the working speed and over-speed,respectively.Results of vibration analysis of the propeller and crankshaft system coupled in torsional and longitudinal direction indicate that the system dynamic behaviors are relatively complicated especially in the components of the frequency response.For example,the 4 times of an exciting frequency acting on the propeller by fluid appears at 130 r/min,while not yield at 105 r/min.While the possible abnormal vibration at over-speed just needs to be vigilant.So when designing the propeller shafting used in marine diesel engines,strength calculation and vibration analysis based only on linear model may cause great errors and the proposed research provides some references to design diesel engine propeller shafting used in large marines.
基金the National Natural Science Foundation of China(No.51109131)
文摘Because of propeller hydrodynamic influence, the shafting vibration is a coupled vibration which includes torsional, longitudinal and whirling vibrations. It is unsuitable to analyze different vibrations of propulsive shafting systems with development of shipbuilding technologies. To overcome the shortages of traditional marine standards, we establish a new numerical model of the shafting coupled vibration. And we put forward shafting coupled vibration calculation to ensure better reliability of main propulsion system. The shafting system is modeled into two sub-systems, a continuous one and a discrete one. Wave approach and transit matrix method are used to investigate displacement and stress fields in continuous and discrete sub-systems, respectively. And vibrations of different modes in both sub-systems are coupled by using dynamic equilibrium and continuity condition to deduce the global equations governing the motion of shafting. The coupling calculation is then used to research the reason of a very large crude carrier(VLCC) stern hull vibration. It is shown by the comparison of the results from both coupling and dependent vibration calculations that vibration in deferent directions will cause deformation in the same mode, which leads to extra stress and displacements on shafting, especially as the resonant frequencies of different vibration modes match each other. This is helpful to prevent ship stern vibration due to poor shafting vibration calculation.
基金the National Natural Science Foundation of China (Nos.50979058 and 51109131)the Simulation and Research Fund of Vessel Reducing Vibration with Stochastic Vibration Influence(No.J10LG60)
文摘With the rudder angles getting larger and larger,the moment and force on propeller shafts,which are caused by complex flowing field,become more and more.They influence the shafting alignment greatly.Stress analysis of propeller shafts has been done under increasing rudder corner conditions with complex hydrodynamics simulation for a great domestic liquified natural gas(LNG) vessel,which is with dual propulsion systems.The improved three-moment equation is adopted in the process of dual propulsive shafting alignment.The calculated results show that the propeller hydrodynamic characteristics,which affect dual propulsive shafting alignment greatly,must be considered under large rudder angle conditions.Shafting accidents of Korean LNG vessels are interpreted reasonably.At the same time,salutary lessons and references are afforded to the marine multi-propulsion shafting alignment in the future.
基金financially supported by the National Natural Science Foundation of China under Grant No.51179079
文摘The shafting vibration is closely related to the rotational angular speed.The angular speed of hydro turbine generating sets(HTGS)is rapidly change in fault transient,it maybe reduce the shafting damage.By means of energy analysis,the differential equation of shafting vibration for the HTGS is derived,in which include the equation of generator rotor and hydro turbine runner,it can be applied to transient analysis.Shafting model is transformed into first order differential equation groups,and is combined with the motion equation of HTGS to build integrated model.Various additional forces of shafting are taken as input inspire in proposed model,the generality of model is good.At last,the shafting vibration in emergency stop transient is simulated.
基金Supported by the National Science and Technology Major Project(No.2017-Ⅳ-0010-0047)Key Laboratory Fund for Ship Vibration and Noise(No.614220406020717)+1 种基金China Postdoctoral Science Foundation Funded Project(No.2020M670113)the Fundamental Research Funds for the Central Universities(No.JD2003)。
文摘This paper aims at investigating the effectiveness of squeeze oil film in suppressing the longitudinal vibration of propulsion shaft systems through a novel integral axial squeeze film damper(IASFD).After designing the IASFD,a propulsion shafting test rig for the longitudinal vibration control is built.Longitudinal vibration control experiments of the propulsion shafting are carried out under different magnitude and frequency of the excitation force.The results show that both IASFD elastic support and IASFD elastic damping support have excellent vibration attenuation characteristics,and can effectively suppress the longitudinal vibration of the shaft system in a wide frequency range.However,IASFD elastic damping support has a more significant vibration reduction effect than the other supports,and increasing the damping of the system has obvious effect on reducing the shafting vibration.For an excitation force of 45 N,the maximum reduction of the vibration amplitude is 89.16%.Also,the vibration generated by the resonance phenomenon is also significantly reduced.
基金the National Natural Science Founda-tion of China(No.51479154)。
文摘According to the analysis of the problems about the operation of marine propulsion shafting in steady state,the geometric and mechanical coupling relationships between marine propulsion shafting and oil film of bearings in two-dimensional space are established,and a coupling mathematical model of the marine propulsion shafting in steady operating state is proposed.Then the simulation of a real ship is carried out,and the variation laws of some special parameters such as bearing load and deflection are obtained.Finally,the results of simulation are verified by experimental data of a real ship,which can provide the mathematical model and analysis method for the research on the characteristics of ship propulsion shafting condition in steady state.
文摘Shafting vibration has been a problem of 660MW steam turbine of SAIC in a power plant since it was put into operation. Through long-term tracking and in-depth analysis of the unit and combined with the opportunity of a repair of the unit, find out the causes of shafting vibration, verify and deal with them one by one, and eliminate poor spherical contact of main engine #3 bearing, #4 bearing seat and foundation void. There are some problems, such as the breakage of the generator seal pad and the thermal imbalance of the generator rotor, so that the shafting vibration reaches an excellent level.
基金co-supported by the National Natural Science Foundation of China(No.52275061)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0562)。
文摘The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFD1700802).
文摘To enhance the operational capacity and space utilization of baffle-drop shafts,this study improved the traditional baffle-drop shaft by expanding the wet-side space,incorporating large rotation-angle baffles,and installing overflow holes in the dividing wall.A three-dimensional turbulent model was developed using ANSYS Fluent to simulate the hydraulic characteristics of both traditional and new baffle-drop shafts across various flow rates.The simulation results demonstrated that the new shaft design allowed for discharge from both the wet and dry sides,significantly improving operational capacity,with the dry side capable of handling 40%of the inlet flow.Compared to the traditional shaft,the new design reduced shaft wall pressures and decreased the mean and standard deviation of pressure on typical baffles by 21%and 63%,respectively,therefore enhancing structural safety.Additionally,the new shaft achieved a 2%-12%higher energy dissipation rate than the traditional shaft across different flow rates.This study offers valuable insights for the design and optimization of drop shafts in deep tunnel drainage systems.
基金supported by the National Key Research and Development Program of China(No.2022YFE0123700)the National Natural Science Foundation of China(No.52205329)the Beijing Natural Science Foundation(Nos.L212024 and L201010).
文摘To address the increasing demand for corrosion-resistant shaft components,a bi-metallic composite shaft comprising carbon steel,which is known for its high thermal strength,and stainless cladding,which offers excellent corrosion resistance,was introduced.A novel method for manufacturing these composite shaft parts using cross-wedge rolling(CWR)was proposed and explored.Thermal simulation experiments,CWR forming trials and finite element analysis were conducted to examine the coordinated deformation during the CWR process.The results revealed a downhill diffusion pattern of elements from higher to lower-concentration areas,forming a smooth and uniform concentration gradient.When the cladding thickness(CT)ranged from 3 to 4 mm,the trajectories of the points on both the cladding material and the substrate coincided,indicating strong bonding at the transitional interface of the composite shaft.Conversely,with a CT of 5 mm,coordinated deformation between the substrate and cladding material was not achieved.Shear strength tests demonstrated a gradual decrease in strength with increasing CT.The microscopic morphology of the interface showed that the metal grains near both sides of the interface were refined,and the binding interface displayed a slightly curved shape.A viable method was provided for producing high-performance corrosion-resistant composite shaft components using CWR technology.
基金financially supported by the National Natural Science Foundation of China(No.52004339)the Key Research and Development Project of Hunan Province,China(No.2022SK2075)+1 种基金China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202216)Central South University Graduate Student Independent Exploration and Innovation Project(2024ZZTS0378).
文摘The self-reforming of coke oven gas(COG)in a gas-based shaft furnace was investigated,employing metallized iron as a catalyst.Thermodynamic analyses,supported by FactSage 8.3 calculations and regression modeling,were used to investigate the effects of temperature(700–1100℃),CO_(2)(3%–10%),and H_(2)O(1%–9%)concentrations on CH_(4) conversion efficiency.Results indicate that CH_(4) conversion exceeds 90%at temperatures above 1000℃,with CO_(2) and H_(2)O concentrations at 9%and 5%,respectively.During the reforming process,introducing CO_(2) provides additional oxygen,facilitating the oxidation of CH_(4),while H_(2)O enhances H_(2) production through the steam reforming pathway.Experimental findings reveal a CH_(4) conversion of 85.83%with a H_(2)/CO ratio of 5.44 at 1050℃.In addition,an optimal H_(2)O concentration of 6%yields the highest CH_(4) conversion of 84.24%,while CO_(2) exhibits minimal effects on promoting the reforming process.Increasing the metallization rate of pellets from 43%to 92%significantly enhances CH_(4) reforming.This is mainly due to the fact that metallized iron is vital in promoting CH_(4) dissociation and improving syngas yield by providing active sites for the redox cycle of CO_(2) and H_(2)O.
基金the National Key R&D Program of China(Nos.2021YFC2902400 and 2021YFC2902401)the project of State Key Laboratory of Intelligent Optimized Manufacturing in Mining&Metallurgy Process(No.BGRIMM-KZSKL-2023-14).
文摘The hydrogen-enriched direct reduction shaft furnace addresses the high CO_(2) emissions associated with the blast furnace process.A discrete element method(DEM)model was introduced to explore how the structure of the diversion cone affects particle descent behavior in a hydrogen-enriched shaft furnace.The results indicated that in the absence of a diversion cone,the descending velocity near the furnace wall zone is significantly lower than that at its center,resulting in a‘V’-shaped burden flow pattern.The discharge velocity has a minor impact on the flow pattern in the shaft furnace.Upon installation of a diversion cone,burden descending velocity becomes more uniform,leading to a‘-’-shaped burden flow pattern.As the bottom of the diversion cone ascends(i.e.,the lower end of the diversion cone is progressively closer to the top),there is an increase in the volume fraction of the dead zone within the shaft furnace.This is particularly evident in the formation of a triangular dead zone at the base of the diversion cone.It is suggested that the lower cone of the bi-conical diversion cone should maintain a sufficient height.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277165,41920104007)the Hubei Natural Science Foundation(Grant No.2023AFD217).
文摘The safety of the initial support during the construction of inclined shafts in tunnels traversing through high-hydraulic-pressure surrounding rocks is paramount.This study examines a high-hydraulic-pressure inclined shaft of a tunnel in Western Sichuan Province to analyze the damage characteristics of the initial support and propose a radial drainage and decompression treatment method.Field monitoring was conducted to assess the load and deformation of the initial support structure,and on-site investigations identified the distribution of cracked areas.In addition,numerical simulations were performed to evaluate the force and deformation characteristics of the initial support structure,which were then compared with field observations for validation.The variations in the lateral pressure coefficient and water pressure were evaluated.The results revealed that damage was primarily concentrated in the shoulder,spring line,and knee areas,with the bending moment at the knee increasing by up to 66.9%.The application of the radial drainage and decompression treatment method effectively reduced water pressure loads on the initial support.Post-treatment analysis indicated significant reductions in axial force and bending moment,enhancing structural stability.These findings provide valuable insights for improving the safety and durability of initial support systems in inclined shafts of high-hydraulicpressure railroad tunnels.
基金supported by the National Key Research and Development Program of China(No.2021YFB 3401500).
文摘To study the use of a shaft support for the auxiliary shaft of the Xi’anshan Iron Mine,in high-stress strata at a depth between 900 and 1000 m,a new type of mold was developed using the physical similarity model test method,based on the similarity theory,and an experimental model of the shaft lining and surrounding rock was poured.Two sets of large-scale destructive tests were conducted on the shaft lining and surrounding rock.The deformation and failure laws of the shaft lining and surrounding rock under high ground stress and their ultimate horizontal bearing capacity characteristics were studied,and the safety support characteristics of the shaft lining under the interaction of the shaft lining and surrounding rock were obtained.An experimental study demonstrated that the axial pressure on the shaft wall directly affected its ultimate horizontal bearing capacity of the shaft wall.In designing the shaft wall,the influence of the axial pressure on the stress state of the concrete should be considered,and the vertical pressure should be modified to optimize the utilization of the three-dimensional compressive strength of the concrete.The reliability of the 400-mm C30 concrete shaft wall at a depth of 1000 m in the actual project was verified,and the ultimate horizontal bearing capacity of the shaft wall was obtained for a depth of 1000 m.
基金financial support from the National Natural Science Foundation of China(No.52174328)the Fundamental Research Funds for the Central Universities of Central South University(No.2024ZZTS0062).
文摘The iron and steel industry,standing as a quintessential manufacture example with high consumption,pollution and emissions,faces significant environmental and sustainable development challenges.Electric arc furnace(EAF)steelmaking process mainly uses scrap as raw material and is characterized by environmentally friendly and recyclable process.However,the further development of EAF route in China is limited by the reserve,supply,availability and quality of scrap resource.Direct reduced iron(DRI)is one of typical low-carbon and clean charges,which can effectively make up for the adverse effects caused by the lack of scrap.The physical and chemical properties,classifications,and production technologies of DRI are firstly reviewed.In particular,the reducing gas types,reduction temperature,and reduction mechanism of the DRI production with gas-based shaft furnace(SF)technology are detailed.Considering the crucial role played by DRI application in EAF,the influences of DRI addition on EAF smelting rules and operations including the blending and charging process,heat transfer and melting in molten bath,slag formation operation,refractory corrosion,and slag system evolution are then further discussed.Finally,the comparative analysis and assessment of the consumption level of material and energy as well as the cleaner production both covering the clean chemical composition of molten steel and the clean environment impact in EAF steelmaking with DRI charged are conducted.From perspectives of metallurgical process engineering,a suitable route of hydrogen generation and application(from coke oven gas,methanol,and clean energy power),CO_(2) capture and utilization integrated with SF–EAF process is proposed.In view of the difficulties in large-scale DRI application in EAF,the follow-up work should focus on the investigation of DRI charging and melting,slag system evolution and molten pool reaction rules,as well as the developments of the DRI standardized use technology and intelligent batching and control models.
基金Supported by Wuhu Municipal Science and Technology Bureau of Anhui Province,No.2022cg43.
文摘BACKGROUND The objective of this study was to evaluate the use of combined parallax-free panoramic X-ray imaging during surgery by enabling the mobile C-arm with minimally invasive plate osteosynthesis(MIPO)in the management of proximal humeral shaft fractures.AIM To evaluate parallax-free panoramic X-ray images during surgery.METHODS A retrospective series of 17 proximal humeral shaft fractures were treated using combined parallax-free panoramic X-ray imaging during surgery by enabling the mobile C-arm with MIPO.The operating time and radiation exposure time were recorded,and early postoperative physical therapy and partial weight bearing were encouraged.Patients were followed at regular intervals and evaluated radiographically and clinically.RESULTS The mean operating time and radiation time were 73(range,49-95)minutes and 57(range:36-98)seconds,respectively.No complications occurred during the operation.All fractures healed at an average of 16.9(range:15-23)weeks.The average Constant-Murley score for all the patients was 89.5(range:75-100)points.None of the patients showed symptoms of vascular or nerve damage or wound infection.Three months after the operation,none of the patients developed subacromial impingement syndrome.No loosening or fracture of the implants occurred.The frontal and lateral radiographs showed good alignment.CONCLUSION We consider that MIPO with combined parallax-free panoramic X-ray imaging during surgery is an efficient method for treating proximal humeral shaft fractures,and could significantly reduce operative morbidity as well as lower the rate of intra-and postoperative complications.
文摘Operative management of humeral shaft fractures demonstrates superior early functional recovery(6-month Disabilities of the Arm,Shoulder,and Hand scores)and significantly lower nonunion rates(63.9%reduction)compared to functional bracing,particularly in complex cases,while conservative treatment remains viable for low-demand patients.Surgical techniques,including open reduction internal fixation,intramedullary nailing,and minimally invasive plate osteosynthesis,offer trade-offs between anatomic precision and complication risks(e.g.,radial nerve injury vs rotator cuff damage),with over 90%of radial nerve injuries resolving spontaneously.Ultrasound-guided diagnosis(89%sensitivity,95%specificity)optimizes decision-making for nerve entrapment.Individualized treatment selection,prioritizing fracture complexity and patient needs,is critical to balance accelerated rehabilitation with minimized complications.
文摘Background of the Study: Femoral shaft fracture is the most common pediatric injury requiring hospitalization. For children less than 5 years old, non-surgical approach is recommended. For pediatric patients 5 - 14 years old, the most common mode of treatment is flexible intramedullary nailing with a known complication of pain at post-op site, inflammatory reaction/bursitis at the entry site, superficial and deep infection, knee synovitis, knee stiffness, leg length discrepancy, proximal nail migration, angulation or malunion, delayed and non-union, implant breakage. This study aims to present a rare complication of a femoral fracture fixed with flexible intramedullary nail. Methodology: We report the outcome of a 12-year-old male with peri implant fracture of the left femur. He underwent removal of plates and screws and subsequently fixed with flexible intramedullary nails. Patient was followed up at 1, 3, 7, and 10 months post-operatively. Varus-valgus, sagittal angulation, and limb shortening were measured pre- and post-operatively. Complications were recorded on each visit. Results: Pre-operative varus angulation was 10˚, pro-curvatum of 55˚ with limb shortening of 4 cm. Postoperatively, varus was maintained to 10˚ but pro-curvatum was corrected to 4˚ and limb shortening was reduced to 1 cm. However, after 1 month the varus angulation increased to 30˚ while maintaining sagittal pro-curvatum. Limb shortening also increased to 2 cm. New bone formation started to appear along the mechanical axis of the left femur which is apparent at 3 months post-op and pro-curvatum increased to 20˚. At 7 and 10 months post-op no signs of union was noted at the fracture site but the callus formation along the mechanical axis gradually matured and appeared as a new femoral shaft. Conclusion: Formation of new bone in response to unstable flexible intramedullary fixation in pediatric femoral shaft fracture is a very rare complication.
基金supported by the National Natural Science Foundation of China(NSFC/RGC/JRF N_HKU735/21)Research Grant Council of Hong Kong,China(17102120,17108821,17103922,C1024-22GF,C7074-21G)+1 种基金Health and Medical Research Fund(HMRF 09200966)(to CSWL)FRQS Postdoctoral Fellowship(to AHKF).
文摘Dendritic spines are small protrusions along dendrites that contain most of the excitatory synapses in principal neurons,playing a crucial role in neuronal function by creating a compartmentalized environment for signal transduction.The plasticity of spine morphologies provides a tunable handle to regulate calcium signal dynamics,allowing rapid regulation of protein expression necessary to establish and maintain synapses(Cornejo et al.,2022).If excitatory inputs were to be located primarily on dendritic shafts,dendrites would frequently short-circuit,preventing voltage signals from propagating(Cornejo et al.,2022).It is thus not surprising that the structural plasticity of dendritic spines is closely linked to synaptic plasticity and memory formation(Berry and Nedivi,2017).While comprehensive in vitro studies have been conducted,in vivo studies that directly tackle the mechanism of dendritic transport and translation in regulating spine plasticity spatiotemporally are limited.
