A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the fi...A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time. It is shown that under some assumptions, the stability equation can be obtained yielding from a group of homogeneous equations. The stability can be judged by the non-dimensional imaginary part of the resultant complex frequency eigenvalue. Further more, based on the analysis of the unsteady phenomenon caused by casing treatment, the function of casing treatment has been modeled by a wall impedance condition which is included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system. Finally, some experimental investigation and two numerical evaluation cases are conducted to validate this model and emphasis is placed on numerically studying the sensitivity of the setup of different boundary conditions on the stall inception of axial flow fan/compressors. A novel casing treatment which consists of a backchamber and a perforated plate is suggested, and it is noted that the open area ratio of the casing treatment is less than 10%, and is far smaller than conventional casing treatment with open area ratio of over 50%, which could result in stall margin improvement without obvious efficiency loss of fan/compressors.展开更多
The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a re...The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.展开更多
An analytical model for chatter aero-engine casings is presented in this paper stability prediction in bull-nose end milling of And the mechanics and dynamics variations due to the complex cutter and workpiece geomet...An analytical model for chatter aero-engine casings is presented in this paper stability prediction in bull-nose end milling of And the mechanics and dynamics variations due to the complex cutter and workpiece geometry are considered by analyzing the effects of the lead angle on the milling process. Firstly, the tool-workpiece engagement region is obtained by using a previously developed method and divided into several disk elements along the tool-axis direction. Secondly, a 3D dynamic model for stability limit calculation is developed and simplified into a 1D model in normal direction considering only the dominant mode of the workpiece. Then the cutting force coefficients, the start and exit angles corresponding to each disk element are determined. And the total stability lobe diagram is calculated using an iterative algorithm. Finally, several experimental tests are carried out to validate the feasibility and effectiveness of the proposed ~rediction approach.展开更多
The influence of Axial-Slot Casing Treatment(ASCT)on the performance and stability enhancement mechanisms of ASCT were experimentally and numerically investigated in a highspeed mixed-flow compressor under three diffe...The influence of Axial-Slot Casing Treatment(ASCT)on the performance and stability enhancement mechanisms of ASCT were experimentally and numerically investigated in a highspeed mixed-flow compressor under three different tip clearances.Unsteady simulations showed the compressor stalled through end-wall stall route,i.e.the spike stall inception originating from rotor tip region,which was validated by dynamical measurements.When the ASCT was applied,greater than 20%of Stall Margin Improvement(SMI)could be achieved for the compressor under each tip clearance size.The streamwise velocity contours and flow structures in the tip region and axial slots were deeply analyzed to explore how the so called‘‘suction and injection effects"generated by the ASCT manipulate tip clearance flow and enhance the stability of compressor under different tip clearances.It was found that the dominant stability enhancement mechanisms of ASCT varies with tip clearance size for the mixed-flow compressor.(A)For the small tip clearance,the dominant mechanism of stability enhancement is the blockage reduction generated in the blade passage by the suction effect of ASCT.(B)For the large tip clearance,the injection effect of the ASCT is the dominant mechanism of stability enhancement with ASCT,which plays the leading role in delaying the spillage of incoming/tip leakage flow interface at the rotor Leading Edge(LE)plane.展开更多
This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is e...This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is employed to analyze the stability of 3D anisotropic soil slopes.The accuracy of the proposed method is first verified against the data in the literature.We then simulate the 3D soil slope with a straight slope surface and the convex and concave slope surfaces with a 90turning corner to study the 3D effect on slope stability and the failure mechanism under anisotropy conditions.Based on our numerical results,the end effect significantly impacts the failure mechanism and safety factor.Anisotropy degree notably affects the safety factor,with higher degrees leading to deeper landslides.For concave slopes,they can be approximated by straight slopes with suitable boundary conditions to assess their stability.Furthermore,a case study of the Saint-Alban test embankment A in Quebec,Canada,is provided to demonstrate the applicability of the proposed FE model.展开更多
The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The...The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The framework is validated through the experiments of rotating inlet distortion within a low-speed compressor. The input–output method is subsequently applied to transonic compressors, including NASA Rotor37 and Stage35, wherein impedance optimization is studied along with the exploration of its fundamental mechanisms. The IBC is employed to model the effect of Casing Treatment (CT). The optimal complex impedance values are determined through predicted results and tested across a range of circumferential modes and forcing frequencies. The IBC significantly reduces the energy and Reynolds stress gain, notably at the first-order circumferential mode and within the Rotor Rotating Frequency (RRF) range. Output modes reveal that transonic compressors with fine-tuned impedance values exhibit a more confined perturbation distribution and redistribute the perturbations compared to the uncontrolled case. Additionally, the roles of resistance and reactance are elucidated through input–output analysis, and resistance determines the energy transfer direction between flow and pressure waves and modulates the amplitude, whereas reactance modifies the phase relationships and attenuates the perturbations.展开更多
Slope is a non-linear and uncertain kinetic system affected by many factors. In view of the incompleteness and uncertainty of the information of slope stability evaluation, a new method of slop stability evaluation by...Slope is a non-linear and uncertain kinetic system affected by many factors. In view of the incompleteness and uncertainty of the information of slope stability evaluation, a new method of slop stability evaluation by using case-based reasoning is presented. Considering the sensitivity of attribute weights to the environment, the algorithm of attribute weights is set up on the basis of the concept of changeable weights. Calculating the similarity between target case of the slope and base case, the stability of target case is evaluated. It is shown from examples that the method is simple, visual, practical, and convenient for use.展开更多
Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equi...Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equilibrium method. The calculation results present that the safety factors of pillars in Sections 19, 20, 24, 28 are less than 1.3, and those of unstable sections are identified preliminarily. Further, a numerical investigation in Sections 18, 20, 22, 24, 25 and 28 implemented with numerical code RFPA20 is employed to further validate the pillar performance and the stability of stopes. The numerical results show the pillars in Sections 18, 22 and 24 are stable and the designed pillar size is suitable. The width of the ore body near Section 28 averages 20 m, failure occurs in the left stope, but the boundary pillars near Section 28 maintain good performance. The pillars in Sections 20 and 25 are unstable which are mainly affected by the Faults F8 and F18. The existence of faults alters the stress distribution, failure mode and water inrush pathway. This work provides a meaningful standard for boundary pillar and stope design in a mine as it transitions from an open pit to underground.展开更多
This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on ...This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment pillar.The primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 457-m-wide longwall faces under about 183 m of cover. Four test wells and four monitoring wells were drilled and installed over a 38-m by84-m centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457-m-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries.展开更多
The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the ...The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.展开更多
Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in ga...Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings.If the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or explosion.By the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars.The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study.The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars.As the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep cover.Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study.This study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam.The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability.The other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas wells.Numerical modeling was used to model abutment pressure,subsurface deformations,and the response of gas well casings.The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of gas well failures,thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars.展开更多
BACKGROUND In recent years,the mechanical concept of intervertebral disc regeneration has become more and more popular due to the increasing awareness of the importance of preservation of spine movement.Interestingly,...BACKGROUND In recent years,the mechanical concept of intervertebral disc regeneration has become more and more popular due to the increasing awareness of the importance of preservation of spine movement.Interestingly,there is increasing evidence,however,that dynamic stabilization systems may compensate nonphysiological loads,limit pathological movement,normalize disc height and intradiscal pressure,and provide an adaptive environment for disc regeneration.CASE SUMMARY The patient was a 54-year-old man,who presented with a 10-year history of mechanical back pain,which had become progressively serious and radiated into the left lower limb with numbness 3 mo prior.He had decreased muscle strength(class IV)of the left dorsal extensor and plantar flexor.Magnetic resonance imaging scans showed L3-S1 disc degeneration and L4-L5 disc herniation.Because the patient did not respond to various conservative treatments,he underwent a posterior L4-5 discectomy with fixation of the BioFlex dynamic stabilization system(Bio-Spine,Seoul,Korea).Preoperative symptoms were relieved and lumbar function was markedly improved after the operation.L4-L5 disc rehydration of instrumented segment was noted on magnetic resonance imaging at the 2-year follow-up.CONCLUSION Rehydration of the degenerated disc in our patient indicates that the BioFlex dynamic stabilization system may promote disc regeneration.Further research is needed to provide more evidence to support lumbar disc rehydration in the bridged segment using this system.展开更多
BACKGROUND Post-traumatic blunt pericardial injury is a rare condition with only a few reported cases which were generally diagnosed during initial examinations upon admission.However,pericardial injuries not bad enou...BACKGROUND Post-traumatic blunt pericardial injury is a rare condition with only a few reported cases which were generally diagnosed during initial examinations upon admission.However,pericardial injuries not bad enough to dislocate the heart may only cause intermittent electrocardiogram(ECG)changes or be asymptomatic.CASE SUMMARY In this case,we report a blunt pericardial injury undetected on preoperative transthoracic echocardiography and chest computed tomography.We misjudged intermittent ECG changes and blood pressure fluctuations as minor symptoms resulting from cardiac contusion and did not provide intensive treatment.The pericardial injury was found incidentally during surgical stabilization of rib fractures and was successfully repaired.CONCLUSION Post-traumatic blunt pericardial ruptures should be considered in patients with blunt chest trauma showing abnormal vital signs and ECG changes.展开更多
BACKGROUND Paraganglioma(PGL)is a neuroendocrine tumor originating from paraganglia that can occur in various locations,such as the head,neck,chest,abdomen,and pelvis.Retroperitoneal PGLs are rare,and recurrent cases ...BACKGROUND Paraganglioma(PGL)is a neuroendocrine tumor originating from paraganglia that can occur in various locations,such as the head,neck,chest,abdomen,and pelvis.Retroperitoneal PGLs are rare,and recurrent cases in this area are partic-ularly uncommon,posing considerable surgical complexities.Owing to their neu-roendocrine activity,PGLs are capable of secreting hormones like catecholamines,thereby presenting significant challenges in hemodynamic management during the perioperative period.CASE SUMMARY We report a 64-year-old man with a recurrent retroperitoneal PGL.The patient underwent retroperitoneal mass resection in 2013,with postoperative pathology revealing a PGL.Regular follow-up was not conducted until April 2024,when a computed tomography scan revealed a huge mass in the retroperitoneum,closely adjacent to the abdominal aorta.Laboratory examinations revealed elevated levels of catecholamines in the patient's blood serum.Upon admission,volume expan-sion and blood pressure(BP)monitoring were carried out for one week,with catecholamine levels reviewed and normalized.Adequate preoperative prepa-ration was conducted,including central venous access,arterial BP monitoring,and the preparation of vasoactive agents.During tumor resection,the patient ex-perienced acute,significant fluctuations in BP.The timely intervention of the anesthesiologist stabilized the BP,facilitating the successful resection of the tumor which was confirmed as a recurrent PGL.Postoperative follow-up revealed no evidence of tumor residual or recurrence.CONCLUSION PGL recurrence is rare but non-negligible.PGLs adjacent to major arteries com-plicate surgery,and perioperative hemodynamic stability demands meticulous attention.Core Tip:Recurrent retroperitoneal paragangliomas are infrequent but pose substantial surgical challenges,particularly when located adjacent to critical vascular structures such as the abdominal aorta.Effective perioperative management of he-modynamic fluctuations,driven by catecholamine secretion,requires meticulous preoperative planning,including volume expansion,blood pressure monitoring,and vasoactive agent preparation.Surgical intervention demands prompt and coordinated anesthetic support to stabilize hemodynamics,ensuring successful tumor resection.Given the potential for late recurrence,long-term follow-up is essential for early detection and management of asymptomatic recurrences.INTRODUCTION Paraganglioma(PGL)is a neuroendocrine tumor originating from paraganglia,which are associated with the autonomic nervous system[1].These tumors arise from chromaffin cells or similar cells capable of secreting catecholamines,such as adrenaline and noradrenaline.PGLs manifest in various anatomical locations,including the head,neck,chest,abdomen,and pelvis,and are characterized by neurosecretory and chief cells surrounded by prominent vascular stroma.Although typically benign,malignant forms of PGL are also recognized,and they may exhibit a tendency for recurrence or me-tastasis[2].PGLs located in the retroperitoneum are relatively uncommon and present greater surgical challenges because of their complex anatomical location near vital organs and major blood vessels.Their catecholamine-secreting nature further complicates the maintenance of hemodynamic stability during the perioperative period.In May 2024,a patient with recurrent retroperitoneal PGL was admitted to our hospital,and the details are reported below.展开更多
BACKGROUND Periprosthetic fractures of the tibia are uncommon complications after total knee arthroplasty(TKA).Therefore,there is still clinical debate regarding the appropriate treatment method.This study presents th...BACKGROUND Periprosthetic fractures of the tibia are uncommon complications after total knee arthroplasty(TKA).Therefore,there is still clinical debate regarding the appropriate treatment method.This study presents the case of a patient with two successive periprosthetic fractures of the tibial shaft treated with revision TKA(rTKA)and intramedullary fixation.CASE SUMMARY A 65-year-old woman was treated for tibial shaft pseudarthrosis after a periprosthetic fracture.The patient underwent rTKA with a tibial component exchange to a long-stemmed implant.At her 1.5-year follow-up visit,partial asymptomatic bone union was noted with no prosthesis loosening.The patient achieved 0°to 120°range of motion and a stable knee,and reported high satisfaction.Improvements were observed in the Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC)from 74 to 17,and in the knee society scores(KSS)from 56 to 91(clinical)and 10 to 80(functional).After 2.5 years,the patient sustained a second fracture below the original site due to low-energy trauma.The rTKA with intramedullary stabilization was performed.One year later,WOMAC and clinical and functional KSS were 15,81,and 80,respectively.Despite tibial shortening and lower limb inequality,the patient remains very satisfied and does not experience any issues with daily activities nor weight-bearing.CONCLUSION There is little consensus in the literature on the management of tibial shaft periprosthetic fractures.Intramedullary stabilization may yield excellent outcomes,but individual case discussion is necessary for rTKA indications.展开更多
An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(...An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.展开更多
Casing treatment is a mature stabilization technique which has been widely applied on aero-engines for modern aircrafts and turbo-chargers for automobiles. After the investigations of half century since the 1960 s, th...Casing treatment is a mature stabilization technique which has been widely applied on aero-engines for modern aircrafts and turbo-chargers for automobiles. After the investigations of half century since the 1960 s, this technique has been well developed for various configurations with different effectiveness. From the perspective of stabilization mechanism, this paper roughly categorizes the configurations of casing treatment into two types: traditional ones which work by affecting the flow structure of blade tip region; a novel one named as Stall Precursor-Suppressed(SPS) casing treatment. The effectiveness of both types will be demonstrated for their applications on axial compressors and centrifugal compressors with uniform or distorted inlet. And the stabilization mechanism of casing treatments for regular types and SPS one will also be explained respectively. In addition, this review will summarize the methodologies of casing treatments with the numerical simulations for regular grooved configurations and the eigenvalue approach for SPS casing treatment.Looking forward to the future of compressor stabilization, casing treatment technique will still exist as a general and inexpensive option, and the exploration for its effectiveness and mechanism will be deeper with the development of computational fluid dynamics and advanced measurement techniques.展开更多
The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental res...The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow.The distorted flow fields of different levels are generated by annular distortion flow generators of different heights.The characteristic curves under these conditions are measured and analyzed.The results show that the radial inlet distortion could cause a stall margin loss from 2%to30%under different distorted levels.The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of characteristic curves.The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment.The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system.展开更多
This study investigated the influence of casing profiles on the aeroelastic stability of a transonic compressor rotor.To elucidate the influence of casing profiles on aerodynamic damping(AD)and delve into more detaile...This study investigated the influence of casing profiles on the aeroelastic stability of a transonic compressor rotor.To elucidate the influence of casing profiles on aerodynamic damping(AD)and delve into more detailed insights,the influence coefficient method and phase-shift theory were incorporated into the conventional energy method to establish the multi-passage energy method.The unsteady pressure was calculated using the influence coef-ficient method and the outcomes at various nodal diameters(NDs)were reconstructed based on the phase-shift theory.Thus,the multi-passage energy method offers more comprehensive information than the conventional energy method,the aeroelastic eigenvalue method,and the coupled fluid-structure interaction method.Four casing profiles were simulated.In contrast to the straight casing configuration,the concave shrinking casing was found to be detrimental to aeroelastic stability.The convex shrinking casing can alleviate the blockage in the tip flow field and improve both the aerodynamic performance and aeroelastic stability.The multi-passage energy method further revealed that the AD is contributed by the blade itself and the adjacent blades.In comparison to the straight casing,the convex shrinking casing not only enhances the AD of the blade itself but also diminishes the AD fluctuation of the adjacent blades.Consequently,the minimum AD is increased.展开更多
Generally, casing treatment（CT） is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a met...Generally, casing treatment（CT） is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in experiment. In order to investigate the mechanism of this kind of casing treatment, an experimental investigation of a stall precursor-suppressed（SPS） casing treatment with air suction or blowing air is conducted in the present paper. The SPS casing treatment is designed to suppressing stall precursors to realize stall margin enhancement in turbomachinery. The experimental results show that the casing treatment with blowing air of small quantity can improve the stall margin by about 8% with about 1% efficiency loss. By contrast, the SPS casing treatment with micro-bias flow does not improve the stall margin much more than that without bias flow, even worse. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with the casing treatment.It is found that the stall margin improvements vary with the modification of the unsteady shedding flow and the unsteady wall boundary impedance. The experimental results agree fairly well with the theoretical prediction using a flow stability model of rotating stall.展开更多
基金National Natural Science Foundation of China (50736007, 50890181)the Innovation Foundation of BUAA for PhD Graduates (300383)
文摘A three-dimensional compressible flow stability model is presented in this paper, which focuses on stall inception of multi-stage axial flow compressors with a finite large radius annular duct configuration for the first time. It is shown that under some assumptions, the stability equation can be obtained yielding from a group of homogeneous equations. The stability can be judged by the non-dimensional imaginary part of the resultant complex frequency eigenvalue. Further more, based on the analysis of the unsteady phenomenon caused by casing treatment, the function of casing treatment has been modeled by a wall impedance condition which is included in the stability model through the eigenvalues and the corresponding eigenfunctions of the system. Finally, some experimental investigation and two numerical evaluation cases are conducted to validate this model and emphasis is placed on numerically studying the sensitivity of the setup of different boundary conditions on the stall inception of axial flow fan/compressors. A novel casing treatment which consists of a backchamber and a perforated plate is suggested, and it is noted that the open area ratio of the casing treatment is less than 10%, and is far smaller than conventional casing treatment with open area ratio of over 50%, which could result in stall margin improvement without obvious efficiency loss of fan/compressors.
基金supported by a scholarship from the Peruvian Institute of Mining Engineers
文摘The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.
基金supported by the National Basic Research Program of China(No.2013CB035802)the 111 Project of China(No.B13044)
文摘An analytical model for chatter aero-engine casings is presented in this paper stability prediction in bull-nose end milling of And the mechanics and dynamics variations due to the complex cutter and workpiece geometry are considered by analyzing the effects of the lead angle on the milling process. Firstly, the tool-workpiece engagement region is obtained by using a previously developed method and divided into several disk elements along the tool-axis direction. Secondly, a 3D dynamic model for stability limit calculation is developed and simplified into a 1D model in normal direction considering only the dominant mode of the workpiece. Then the cutting force coefficients, the start and exit angles corresponding to each disk element are determined. And the total stability lobe diagram is calculated using an iterative algorithm. Finally, several experimental tests are carried out to validate the feasibility and effectiveness of the proposed ~rediction approach.
基金the National Science Foundation of China(Nos.51676184,51636001 and 51922098)the National Science and Technology Major Project(Nos.2017-II-00040017 and 2017-II-0005-0018)the National Key R&D Program of China(No.2018YFB0606100)。
文摘The influence of Axial-Slot Casing Treatment(ASCT)on the performance and stability enhancement mechanisms of ASCT were experimentally and numerically investigated in a highspeed mixed-flow compressor under three different tip clearances.Unsteady simulations showed the compressor stalled through end-wall stall route,i.e.the spike stall inception originating from rotor tip region,which was validated by dynamical measurements.When the ASCT was applied,greater than 20%of Stall Margin Improvement(SMI)could be achieved for the compressor under each tip clearance size.The streamwise velocity contours and flow structures in the tip region and axial slots were deeply analyzed to explore how the so called‘‘suction and injection effects"generated by the ASCT manipulate tip clearance flow and enhance the stability of compressor under different tip clearances.It was found that the dominant stability enhancement mechanisms of ASCT varies with tip clearance size for the mixed-flow compressor.(A)For the small tip clearance,the dominant mechanism of stability enhancement is the blockage reduction generated in the blade passage by the suction effect of ASCT.(B)For the large tip clearance,the injection effect of the ASCT is the dominant mechanism of stability enhancement with ASCT,which plays the leading role in delaying the spillage of incoming/tip leakage flow interface at the rotor Leading Edge(LE)plane.
基金supported by the National Natural Science Foundation of China(Grant Nos.51890912,51979025 and 52011530189).
文摘This article presents a micro-structure tensor enhanced elasto-plastic finite element(FE)method to address strength anisotropy in three-dimensional(3D)soil slope stability analysis.The gravity increase method(GIM)is employed to analyze the stability of 3D anisotropic soil slopes.The accuracy of the proposed method is first verified against the data in the literature.We then simulate the 3D soil slope with a straight slope surface and the convex and concave slope surfaces with a 90turning corner to study the 3D effect on slope stability and the failure mechanism under anisotropy conditions.Based on our numerical results,the end effect significantly impacts the failure mechanism and safety factor.Anisotropy degree notably affects the safety factor,with higher degrees leading to deeper landslides.For concave slopes,they can be approximated by straight slopes with suitable boundary conditions to assess their stability.Furthermore,a case study of the Saint-Alban test embankment A in Quebec,Canada,is provided to demonstrate the applicability of the proposed FE model.
基金co-supported by the National Natural Science Foundation of China(Nos.52325602,52306036 and 52306035)the National Science and Technology Major Project of China(No.Y2022-II-0003-0006 and Y2022-II-0002-0005)+1 种基金the project funded by China Postdoctoral Science Foundation(No.2022M720346)supported by the Key Laboratory of Pre-Research Management Centre of China(No.6142702200101).
文摘The influence of Impedance Boundary Condition (IBC) on transonic compressors is investigated. A systematic input–output analytical framework is developed, which treats the nonlinearities as unknown forcing terms. The framework is validated through the experiments of rotating inlet distortion within a low-speed compressor. The input–output method is subsequently applied to transonic compressors, including NASA Rotor37 and Stage35, wherein impedance optimization is studied along with the exploration of its fundamental mechanisms. The IBC is employed to model the effect of Casing Treatment (CT). The optimal complex impedance values are determined through predicted results and tested across a range of circumferential modes and forcing frequencies. The IBC significantly reduces the energy and Reynolds stress gain, notably at the first-order circumferential mode and within the Rotor Rotating Frequency (RRF) range. Output modes reveal that transonic compressors with fine-tuned impedance values exhibit a more confined perturbation distribution and redistribute the perturbations compared to the uncontrolled case. Additionally, the roles of resistance and reactance are elucidated through input–output analysis, and resistance determines the energy transfer direction between flow and pressure waves and modulates the amplitude, whereas reactance modifies the phase relationships and attenuates the perturbations.
基金Funded by Hubei Natural Science Foundation (2000J146)
文摘Slope is a non-linear and uncertain kinetic system affected by many factors. In view of the incompleteness and uncertainty of the information of slope stability evaluation, a new method of slop stability evaluation by using case-based reasoning is presented. Considering the sensitivity of attribute weights to the environment, the algorithm of attribute weights is set up on the basis of the concept of changeable weights. Calculating the similarity between target case of the slope and base case, the stability of target case is evaluated. It is shown from examples that the method is simple, visual, practical, and convenient for use.
基金Projects(1004025,51174044,50934006)supported by the National Natural Science FoundationProject(2011AA060400)supported by the National High Technique Research and Development Program of ChinaProject(Sklgduek1113)supported by Funds of the State Key Laboratory for Geomechanics&Deep Underground Engineering,Chinese University of Mining and Technology,China
文摘Based on the height of back-filled materials, thickness of ore body, height of boundary pillar and dipping angle of ore body and water pressure, the safety factors of all the pillars are calculated with the limit equilibrium method. The calculation results present that the safety factors of pillars in Sections 19, 20, 24, 28 are less than 1.3, and those of unstable sections are identified preliminarily. Further, a numerical investigation in Sections 18, 20, 22, 24, 25 and 28 implemented with numerical code RFPA20 is employed to further validate the pillar performance and the stability of stopes. The numerical results show the pillars in Sections 18, 22 and 24 are stable and the designed pillar size is suitable. The width of the ore body near Section 28 averages 20 m, failure occurs in the left stope, but the boundary pillars near Section 28 maintain good performance. The pillars in Sections 20 and 25 are unstable which are mainly affected by the Faults F8 and F18. The existence of faults alters the stress distribution, failure mode and water inrush pathway. This work provides a meaningful standard for boundary pillar and stope design in a mine as it transitions from an open pit to underground.
文摘This paper presents the results of a comprehensive study conducted by CONSOL Energy, Marcellus Shale Coalition, and Pennsylvania Coal Association to evaluate the effects of longwall-induced subsurface deformations on the mechanical integrity of shale gas wells drilled over a longwall abutment pillar.The primary objective is to demonstrate that a properly constructed gas well in a standard longwall abutment pillar can maintain mechanical integrity during and after mining operations. A study site was selected over a southwestern Pennsylvania coal mine, which extracts 457-m-wide longwall faces under about 183 m of cover. Four test wells and four monitoring wells were drilled and installed over a 38-m by84-m centers abutment pillar. In addition to the test wells and monitoring wells, surface subsidence measurements and underground coal pillar pressure measurements were conducted as the 457-m-wide longwall panels on the south and north sides of the abutment pillar were mined by. To evaluate the resulting coal protection casing profile and lateral displacement, three separate 60-arm caliper surveys were conducted. This research represents a very important step and initiative to utilize the knowledge and science obtained from mining research to improve miner and public safety as well as the safety and health of the oil and gas industries.
基金supported by a NIOSH Capacity Building grant (No. 200-2016-90154) to Drs. G. Walton and E. Holley and collaborators at the Colorado School of Mines
文摘The coal mine roof rating(CMRR) was developed to bridge the gap between geological variation in underground coal mines and engineering design. The CMRR accounts for the compressive strength of the immediate roof, the shear strength and intensity of any discontinuities present, and the moisture sensitivity of the immediate roof. The CMRR has been widely used and validated in Eastern US coal mines, but it has seen limited application in the Western US. This study focuses on roof behavior at a Western coal mine(Mine A). Mine A shows significant lateral geological variation, along with localized faulting and a laterally extensive sandstone channel network. The CMRR is not used to predict roof instability at the mine. It is, therefore, hypothesized that there are other factors that are correlated with roof instability in underground coal mines that could potentially also be considered in conjunction with the CMRR.This hypothesis was tested by collecting 30 CMRR measurements at Mine A. At each measurement location, a binary record of the roof condition(stable or unstable) was made, and other parameters such as depth of cover, presence of faulting, and sandstone channels were also recorded. ANOVA tests showed that the CMRR values and the roof conditions were not strongly correlated, indicating that the CMRR input criteria are not fully predictive of roof stability at this mine. The CMRR values showed statistically significant correlations(p less than 0.05) with faulting as well as with location at an intersection. For areas that had previously experienced roof fall but were currently stable, faulting was correlated with roof condition(p less than 0.05) only when the condition was classified as unstable.
文摘Longwall mining has a significant influence on gas wells located within longwall chain pillars.Subsurface subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well casings.If the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or explosion.By the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal pillars.The current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar study.The study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the pillars.As the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep cover.Gas well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 study.This study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal Seam.The study results indicate that overburden depth and pillar size are not the only determining factors for gas well stability.The other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas wells.Numerical modeling was used to model abutment pressure,subsurface deformations,and the response of gas well casings.The study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of gas well failures,thereby providing a more quantifiable approach to assess the stability of the gas wells in longwall chain pillars.
基金Supported by Foundation of Capital Medical Development,Beijing,China,No.2010026.
文摘BACKGROUND In recent years,the mechanical concept of intervertebral disc regeneration has become more and more popular due to the increasing awareness of the importance of preservation of spine movement.Interestingly,there is increasing evidence,however,that dynamic stabilization systems may compensate nonphysiological loads,limit pathological movement,normalize disc height and intradiscal pressure,and provide an adaptive environment for disc regeneration.CASE SUMMARY The patient was a 54-year-old man,who presented with a 10-year history of mechanical back pain,which had become progressively serious and radiated into the left lower limb with numbness 3 mo prior.He had decreased muscle strength(class IV)of the left dorsal extensor and plantar flexor.Magnetic resonance imaging scans showed L3-S1 disc degeneration and L4-L5 disc herniation.Because the patient did not respond to various conservative treatments,he underwent a posterior L4-5 discectomy with fixation of the BioFlex dynamic stabilization system(Bio-Spine,Seoul,Korea).Preoperative symptoms were relieved and lumbar function was markedly improved after the operation.L4-L5 disc rehydration of instrumented segment was noted on magnetic resonance imaging at the 2-year follow-up.CONCLUSION Rehydration of the degenerated disc in our patient indicates that the BioFlex dynamic stabilization system may promote disc regeneration.Further research is needed to provide more evidence to support lumbar disc rehydration in the bridged segment using this system.
文摘BACKGROUND Post-traumatic blunt pericardial injury is a rare condition with only a few reported cases which were generally diagnosed during initial examinations upon admission.However,pericardial injuries not bad enough to dislocate the heart may only cause intermittent electrocardiogram(ECG)changes or be asymptomatic.CASE SUMMARY In this case,we report a blunt pericardial injury undetected on preoperative transthoracic echocardiography and chest computed tomography.We misjudged intermittent ECG changes and blood pressure fluctuations as minor symptoms resulting from cardiac contusion and did not provide intensive treatment.The pericardial injury was found incidentally during surgical stabilization of rib fractures and was successfully repaired.CONCLUSION Post-traumatic blunt pericardial ruptures should be considered in patients with blunt chest trauma showing abnormal vital signs and ECG changes.
基金Supported by Natural Science Foundation of Zhejiang Province,China,No.LQ21H020007.
文摘BACKGROUND Paraganglioma(PGL)is a neuroendocrine tumor originating from paraganglia that can occur in various locations,such as the head,neck,chest,abdomen,and pelvis.Retroperitoneal PGLs are rare,and recurrent cases in this area are partic-ularly uncommon,posing considerable surgical complexities.Owing to their neu-roendocrine activity,PGLs are capable of secreting hormones like catecholamines,thereby presenting significant challenges in hemodynamic management during the perioperative period.CASE SUMMARY We report a 64-year-old man with a recurrent retroperitoneal PGL.The patient underwent retroperitoneal mass resection in 2013,with postoperative pathology revealing a PGL.Regular follow-up was not conducted until April 2024,when a computed tomography scan revealed a huge mass in the retroperitoneum,closely adjacent to the abdominal aorta.Laboratory examinations revealed elevated levels of catecholamines in the patient's blood serum.Upon admission,volume expan-sion and blood pressure(BP)monitoring were carried out for one week,with catecholamine levels reviewed and normalized.Adequate preoperative prepa-ration was conducted,including central venous access,arterial BP monitoring,and the preparation of vasoactive agents.During tumor resection,the patient ex-perienced acute,significant fluctuations in BP.The timely intervention of the anesthesiologist stabilized the BP,facilitating the successful resection of the tumor which was confirmed as a recurrent PGL.Postoperative follow-up revealed no evidence of tumor residual or recurrence.CONCLUSION PGL recurrence is rare but non-negligible.PGLs adjacent to major arteries com-plicate surgery,and perioperative hemodynamic stability demands meticulous attention.Core Tip:Recurrent retroperitoneal paragangliomas are infrequent but pose substantial surgical challenges,particularly when located adjacent to critical vascular structures such as the abdominal aorta.Effective perioperative management of he-modynamic fluctuations,driven by catecholamine secretion,requires meticulous preoperative planning,including volume expansion,blood pressure monitoring,and vasoactive agent preparation.Surgical intervention demands prompt and coordinated anesthetic support to stabilize hemodynamics,ensuring successful tumor resection.Given the potential for late recurrence,long-term follow-up is essential for early detection and management of asymptomatic recurrences.INTRODUCTION Paraganglioma(PGL)is a neuroendocrine tumor originating from paraganglia,which are associated with the autonomic nervous system[1].These tumors arise from chromaffin cells or similar cells capable of secreting catecholamines,such as adrenaline and noradrenaline.PGLs manifest in various anatomical locations,including the head,neck,chest,abdomen,and pelvis,and are characterized by neurosecretory and chief cells surrounded by prominent vascular stroma.Although typically benign,malignant forms of PGL are also recognized,and they may exhibit a tendency for recurrence or me-tastasis[2].PGLs located in the retroperitoneum are relatively uncommon and present greater surgical challenges because of their complex anatomical location near vital organs and major blood vessels.Their catecholamine-secreting nature further complicates the maintenance of hemodynamic stability during the perioperative period.In May 2024,a patient with recurrent retroperitoneal PGL was admitted to our hospital,and the details are reported below.
文摘BACKGROUND Periprosthetic fractures of the tibia are uncommon complications after total knee arthroplasty(TKA).Therefore,there is still clinical debate regarding the appropriate treatment method.This study presents the case of a patient with two successive periprosthetic fractures of the tibial shaft treated with revision TKA(rTKA)and intramedullary fixation.CASE SUMMARY A 65-year-old woman was treated for tibial shaft pseudarthrosis after a periprosthetic fracture.The patient underwent rTKA with a tibial component exchange to a long-stemmed implant.At her 1.5-year follow-up visit,partial asymptomatic bone union was noted with no prosthesis loosening.The patient achieved 0°to 120°range of motion and a stable knee,and reported high satisfaction.Improvements were observed in the Western Ontario and McMaster Universities Osteoarthritis Index(WOMAC)from 74 to 17,and in the knee society scores(KSS)from 56 to 91(clinical)and 10 to 80(functional).After 2.5 years,the patient sustained a second fracture below the original site due to low-energy trauma.The rTKA with intramedullary stabilization was performed.One year later,WOMAC and clinical and functional KSS were 15,81,and 80,respectively.Despite tibial shortening and lower limb inequality,the patient remains very satisfied and does not experience any issues with daily activities nor weight-bearing.CONCLUSION There is little consensus in the literature on the management of tibial shaft periprosthetic fractures.Intramedullary stabilization may yield excellent outcomes,but individual case discussion is necessary for rTKA indications.
基金supported by the National Natural Science Foundation of China(Nos.52306035 and 52325602)the Science Center for Gas Turbine Project,China(Nos.P2022-A-II-002-001 and P2022-C-II-003-001)+1 种基金the National Science and Technology Major Project,China(Nos.Y2022-II-0002-0005 and Y2022-II-0003-0006)the Key Laboratory of Pre-Research Management Centre,China(No.6142702200101)。
文摘An experimental investigation is conducted to evaluate the performance and the stalling process of a fan subjected to inlet swirls,as well as the effectiveness of an Impedance Boundary-Controlled(IBC)Casing Treatment(CT)on the stall margin recovery.An operating cycle is proposed based on the hysteresis effect of harmonic flap oscillation of airfoils and parallel compressor theory to explain the pressure characteristic of the fan under twin swirl inlets.Twin swirls are observed to reduce the stall margin of the fan,and the circumferential location where the spike is detected turns to the intersection area of the twin swirl.The IBC CT is proven to extend the stall margin of the fan for 12.7%–22.3%when subjected to inlet swirls with an efficiency loss of around 1%.The IBC CT helps to reduce the size of the operating cycle of the fan by redistributing the blade loading and adding the system damping to dissipate the perturbation energy.
基金supported by the National Natural Science Foundation of China (Nos. 51790514, 11661141020 and 51576008)
文摘Casing treatment is a mature stabilization technique which has been widely applied on aero-engines for modern aircrafts and turbo-chargers for automobiles. After the investigations of half century since the 1960 s, this technique has been well developed for various configurations with different effectiveness. From the perspective of stabilization mechanism, this paper roughly categorizes the configurations of casing treatment into two types: traditional ones which work by affecting the flow structure of blade tip region; a novel one named as Stall Precursor-Suppressed(SPS) casing treatment. The effectiveness of both types will be demonstrated for their applications on axial compressors and centrifugal compressors with uniform or distorted inlet. And the stabilization mechanism of casing treatments for regular types and SPS one will also be explained respectively. In addition, this review will summarize the methodologies of casing treatments with the numerical simulations for regular grooved configurations and the eigenvalue approach for SPS casing treatment.Looking forward to the future of compressor stabilization, casing treatment technique will still exist as a general and inexpensive option, and the exploration for its effectiveness and mechanism will be deeper with the development of computational fluid dynamics and advanced measurement techniques.
基金supported by National Natural Science Foundation of China(51236001 and 51576008)National Basic Research Program of China(2012CB720201)+1 种基金Aeronautical Science Foundation of China(2014ZB51018)Fundamental Research Funds for the Central Universities
文摘The present work is about the stall margin enhancement ability of a kind of stall precursor-suppressed（SPS） casing treatment when fan/compressor suffers from a radial total pressure inlet distortion.Experimental researches are conducted on a low-speed compressor with and without SPS casing treatment under radial distorted inlet flow of different levels as well as uniform inlet flow.The distorted flow fields of different levels are generated by annular distortion flow generators of different heights.The characteristic curves under these conditions are measured and analyzed.The results show that the radial inlet distortion could cause a stall margin loss from 2%to30%under different distorted levels.The SPS casing treatment could remedy this stall margin loss under small distortion level and only partly make up the stall margin loss caused by distortion in large level without leading to perceptible additional efficiency loss and obvious change of characteristic curves.The pre-stall behavior of the compressor is investigated to reveal the mechanism of this stall margin improvement ability of the SPS casing treatment.The results do show that this casing treatment delays the occurrence of rotating stall by weakening the pressure perturbations and suppressing the nonlinear amplification of the stall precursor waves in the compression system.
基金supported by the National Nature Science Foundation of China(Grant No.52306034).
文摘This study investigated the influence of casing profiles on the aeroelastic stability of a transonic compressor rotor.To elucidate the influence of casing profiles on aerodynamic damping(AD)and delve into more detailed insights,the influence coefficient method and phase-shift theory were incorporated into the conventional energy method to establish the multi-passage energy method.The unsteady pressure was calculated using the influence coef-ficient method and the outcomes at various nodal diameters(NDs)were reconstructed based on the phase-shift theory.Thus,the multi-passage energy method offers more comprehensive information than the conventional energy method,the aeroelastic eigenvalue method,and the coupled fluid-structure interaction method.Four casing profiles were simulated.In contrast to the straight casing configuration,the concave shrinking casing was found to be detrimental to aeroelastic stability.The convex shrinking casing can alleviate the blockage in the tip flow field and improve both the aerodynamic performance and aeroelastic stability.The multi-passage energy method further revealed that the AD is contributed by the blade itself and the adjacent blades.In comparison to the straight casing,the convex shrinking casing not only enhances the AD of the blade itself but also diminishes the AD fluctuation of the adjacent blades.Consequently,the minimum AD is increased.
基金supported by National Natural Science Foundation of China (Nos. 51236001, 51406229 and 51106154)National Basic Research Program of China (No. 2012CB720201)+1 种基金Aeronautical Science Foundation of China (No. 2014ZB51018)Fundamental Research Funds for the Central Universities
文摘Generally, casing treatment（CT） is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in experiment. In order to investigate the mechanism of this kind of casing treatment, an experimental investigation of a stall precursor-suppressed（SPS） casing treatment with air suction or blowing air is conducted in the present paper. The SPS casing treatment is designed to suppressing stall precursors to realize stall margin enhancement in turbomachinery. The experimental results show that the casing treatment with blowing air of small quantity can improve the stall margin by about 8% with about 1% efficiency loss. By contrast, the SPS casing treatment with micro-bias flow does not improve the stall margin much more than that without bias flow, even worse. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with the casing treatment.It is found that the stall margin improvements vary with the modification of the unsteady shedding flow and the unsteady wall boundary impedance. The experimental results agree fairly well with the theoretical prediction using a flow stability model of rotating stall.
