Experimental investigation has been performed to study the leakage and wear characteristics of carbon seal working at high circumferential speed. To expand the scope of application, two newly designed carbon seals wer...Experimental investigation has been performed to study the leakage and wear characteristics of carbon seal working at high circumferential speed. To expand the scope of application, two newly designed carbon seals were compared: #1 Carbon Seal(CS1) with the inner diameter of136 mm and including 4 segments, #2 Carbon Seal(CS2) with the inner diameter of 212 mm and including 6 segments. Air leakage tests were firstly conducted in the Medium-speed Seal Test Rig. The pressure ratio changed from 1.04 to 2.02 with the rotating speed varying from 0 to18300 r/min. Of paramount concern was the durability test, including 300 h running time accumulated by three different working conditions, which was separately implemented on each carbon seal.The morphology variation of the friction surface, wear and leakage were recorded. Results indicated that the leakage monotonously increases with the pressure ratio and decreases with the rotating speed. Comparing with CS1, more typical features exist on the friction surface of CS2, which are generated by more severe wear. Continually, leakage characteristics deteriorate. Furthermore, fitted formula has been educed for the life prediction of carbon seal, which could provide some supports for aero-engine design.展开更多
Abradable seal rubber has been widely used in aero-engine fans to improve their efficiency by reducing the clearance between rotating and stationary components. To investigate the high-speed scraping behavior between ...Abradable seal rubber has been widely used in aero-engine fans to improve their efficiency by reducing the clearance between rotating and stationary components. To investigate the high-speed scraping behavior between a vulcanized silicone rubber and a Ti-6Al-4V fan blade and evaluate the abradable performance of seal rubber, abrasion tests were conducted at a blade tip velocity of 50–300 m/s with an incursion rate of 100 lm/s. The influences of the blade tip velocity on the wear mechanism and interaction forces were specially analyzed. It is shown that abrasive wear and pattern wear are the predominant wear mechanisms, and pattern wear can be seen as the emergence and propagation of cracks. With an increase of the blade tip velocity, both of the final incursion depth and wear mass loss of seal rubber exhibit growth trends. The gradual changes of rubbing forces with an increase of rubbing time are the characteristic of abrasive wear, and force curves with unstable mutations are a reflection of pattern wear. At a constant incursion rate of 100 lm/s, the maximum values of interaction forces decrease first and then grow with an increase of the blade tip velocity, and the blade tip velocity of 150 m/s becomes the cut-off point between abrasive wear and pattern wear.展开更多
In this paper,the aero-engine test with inter-shaft bearing fault is carried out,and a dataset is proposed for the first time based on the vibration signal of rotors and casings.First,a test rig based on a real aero-e...In this paper,the aero-engine test with inter-shaft bearing fault is carried out,and a dataset is proposed for the first time based on the vibration signal of rotors and casings.First,a test rig based on a real aero-engine is established,driven by motors and equipped with a lubricating system.Then,the aero-engine is disassembled and assembled following the specification process,and the inter-shaft bearing with artificial fault is replaced.Next,the aero-engine test is conducted at 28 groups of high-and low-pressure speeds.Six measuring points are arranged,including two displacement sensors to test the displacement vibration signals of the low-pressure rotor and four acceleration sensors to test the acceleration vibration signals of the casing.The test results are integrated into an inter-shaft bearing fault dataset.Finally,based on the dataset in this paper,frequency spectrum,envelope spectrum,CNN,LSTM,and TST are used for fault diagnosis,and the results are compared with those of CWRU and XJTU datasets.The results show that the characteristic fault frequency cannot be found directly in the spectrum and envelope spectrum corresponding to this paper’s dataset but in CWRU and XJTU datasets.Using CNN,LSTM,and TST for fault diagnosis of the dataset in this paper,the accuracy is 83.13%,85.41%,and 71.07%,respectively,much lower than the diagnosis results of CWRU and XJTU datasets.It can be seen that the dataset in this paper is closer to the actual fault diagnosis situation and is a more challenging dataset.This dataset provides a new benchmark for the validation of fault diagnosis methods.Mendeley data:https://github.com/HouLeiHIT/HIT-dataset.展开更多
This study presents the design of a modified attributed control chart based on a double sampling(DS)np chart applied in combination with generalized multiple dependent state(GMDS)sampling to monitor the mean life of t...This study presents the design of a modified attributed control chart based on a double sampling(DS)np chart applied in combination with generalized multiple dependent state(GMDS)sampling to monitor the mean life of the product based on the time truncated life test employing theWeibull distribution.The control chart developed supports the examination of the mean lifespan variation for a particular product in the process of manufacturing.Three control limit levels are used:the warning control limit,inner control limit,and outer control limit.Together,they enhance the capability for variation detection.A genetic algorithm can be used for optimization during the in-control process,whereby the optimal parameters can be established for the proposed control chart.The control chart performance is assessed using the average run length,while the influence of the model parameters upon the control chart solution is assessed via sensitivity analysis based on an orthogonal experimental design withmultiple linear regression.A comparative study was conducted based on the out-of-control average run length,in which the developed control chart offered greater sensitivity in the detection of process shifts while making use of smaller samples on average than is the case for existing control charts.Finally,to exhibit the utility of the developed control chart,this paper presents its application using simulated data with parameters drawn from the real set of data.展开更多
The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties ...The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties in the Central Appalachian Basin.Geomechanical properties of the Rose Run sandstone(upper Ordovician Knox group)were tested for its suitability as a storage reservoir.A 9.8-m thick section of the Rose Run was penetrated at 1000 m drilled depth and a whole-diameter core and rotary sidewall cores were taken.Average porosity and permeability measured in core plugs were 9.1%and 44.6 mD,respectively.Maximum vertical stress gradient calculated in the wellbore was 26 MPa/km.Wellbore fractures in dolomites underlying and overlying the Rose Run follow the contemporary N53E Appalachian Basin stress field.The Rose Run elastic geomechanical properties were calibrated to values measured in core plugs to evaluate its fracturing risk as a CO2 storage reservoir.Mean Young’s modulus and Poisson’s ratio values of the Rose Run were 45 GPa and 0.23,respectively,whereas Young’s modulus and Poisson’s ratio values were 77.1 GPa and 0.28,respectively,in the overlying Beekmantown dolomite,suggesting the Rose Run may fracture if overpressured during CO2 injection but be confined by the Beekmantown.Triaxial compressive strength measured in core plugs found the Rose Run and Beekmantown fractured at mean axial stresses of 156.5 MPa and 282.2 MPa,respectively,confirming the Beekmantown as suitable for confining CO2 injected into the Rose Run.A step-rate test was conducted in a mechanically-isolated 18.6-m interval bracketing the Rose Run.Static Rose Run reservoir pressure was 9.3 MPa,and fracture gradient under injection was 13.6 MPa/km,suggesting step-rate testing before CO2 injection,and subsequent pressure monitoring to ensure confinement.As the region around the KGS 1 Hanson Aggregates well is underpressured and adjacent to faulted Precambrian basement,further research is needed to evaluate its induced seismicity risk during CO2 injection.展开更多
Purpose-Express freight transportation is in rapid development currently.Owing to the higher speed of express freight train,the deformation of the bridge deck worsens the railway line condition under the action of win...Purpose-Express freight transportation is in rapid development currently.Owing to the higher speed of express freight train,the deformation of the bridge deck worsens the railway line condition under the action of wind and train moving load when the train runs over a long-span bridge.Besides,the blunt car body of vehicle has poor aerodynamic characteristics,bringing a greater challenge on the running stability in the crosswind.Design/methodology/approach-In this study,the aerodynamic force coefficients of express freight vehicles on the bridge are measured by scale model wind tunnel test.The dynamic model of the train-long-span steel truss bridge coupling system is established,and the dynamic response as well as the running safety of vehicle are evaluated.Findings-The results show that wind speed has a significant influence on running safety,which is mainly reflected in the over-limitation of wheel unloading rate.The wind speed limit decreases with train speed,and it reduces to 18.83 m/s when the train speed is 160 km/h.Originality/value-This study deepens the theoretical understanding of the interaction between vehicles and bridges and proposes new methods for analyzing similar engineering problems.It also provides a new theoretical basis for the safety assessment of express freight trains.展开更多
The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced f...The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced firstly. The displacement time histories are then used to analyze the dynamic property such as fundamental frequency of vertical vibration and damping ratio of the test structure, and the acceleration time histories are applied to evaluate the floor vibration serviceability. The floor interaction and comparison of human walking and running are also discussed. Some valuable conclusions are given.展开更多
The pattern run-length coding test data compression approach is extended by introducing don't care bit(x) propagation strategy into it.More than one core test sets for testing core-based System-on-Chip(SoC) are un...The pattern run-length coding test data compression approach is extended by introducing don't care bit(x) propagation strategy into it.More than one core test sets for testing core-based System-on-Chip(SoC) are unified into a single one,which is compressed by the extended coding technique.A reconfigurable scan test application mechanism is presented,in which test data for multiple cores are scanned and captured jointly to make SoC test application more efficient with low hardware overhead added.The proposed union test technique is applied to an academic SoC embedded by six large ISCAS'89 benchmarks,and to an ITC' 02 benchmark circuit.Experiment results show that compared with the existing schemes in which a core test set is compressed and applied independently of other cores,the proposed scheme can not only improve test data compression/decompression,but also reduce the redundant shift and capture cycles during scan testing,decreasing SoC test application time effectively.展开更多
The test vector compression is a key technique to reduce IC test time and cost since the explosion of the test data of system on chip （SoC） in recent years. To reduce the bandwidth requirement between the automatic ...The test vector compression is a key technique to reduce IC test time and cost since the explosion of the test data of system on chip （SoC） in recent years. To reduce the bandwidth requirement between the automatic test equipment （ATE） and the CUT （circuit under test） effectively, a novel VSPTIDR （variable shifting prefix-tail identifier reverse） code for test stimulus data compression is designed. The encoding scheme is defined and analyzed in detail, and the decoder is presented and discussed. While the probability of 0 bits in the test set is greater than 0.92, the compression ratio from VSPTIDR code is better than the frequency-directed run-length （FDR） code, which can be proved by theoretical analysis and experiments. And the on-chip area overhead of VSPTIDR decoder is about 15.75 % less than the FDR decoder.展开更多
基金supported by the National Natural Science Foundation of China(No.51976214)National Science and Technology Major Project(2017-Ⅳ-0010-0047)。
文摘Experimental investigation has been performed to study the leakage and wear characteristics of carbon seal working at high circumferential speed. To expand the scope of application, two newly designed carbon seals were compared: #1 Carbon Seal(CS1) with the inner diameter of136 mm and including 4 segments, #2 Carbon Seal(CS2) with the inner diameter of 212 mm and including 6 segments. Air leakage tests were firstly conducted in the Medium-speed Seal Test Rig. The pressure ratio changed from 1.04 to 2.02 with the rotating speed varying from 0 to18300 r/min. Of paramount concern was the durability test, including 300 h running time accumulated by three different working conditions, which was separately implemented on each carbon seal.The morphology variation of the friction surface, wear and leakage were recorded. Results indicated that the leakage monotonously increases with the pressure ratio and decreases with the rotating speed. Comparing with CS1, more typical features exist on the friction surface of CS2, which are generated by more severe wear. Continually, leakage characteristics deteriorate. Furthermore, fitted formula has been educed for the life prediction of carbon seal, which could provide some supports for aero-engine design.
基金supported by the Fundamental Research Funds for the Central Universities (No. 2013XZZX005)
文摘Abradable seal rubber has been widely used in aero-engine fans to improve their efficiency by reducing the clearance between rotating and stationary components. To investigate the high-speed scraping behavior between a vulcanized silicone rubber and a Ti-6Al-4V fan blade and evaluate the abradable performance of seal rubber, abrasion tests were conducted at a blade tip velocity of 50–300 m/s with an incursion rate of 100 lm/s. The influences of the blade tip velocity on the wear mechanism and interaction forces were specially analyzed. It is shown that abrasive wear and pattern wear are the predominant wear mechanisms, and pattern wear can be seen as the emergence and propagation of cracks. With an increase of the blade tip velocity, both of the final incursion depth and wear mass loss of seal rubber exhibit growth trends. The gradual changes of rubbing forces with an increase of rubbing time are the characteristic of abrasive wear, and force curves with unstable mutations are a reflection of pattern wear. At a constant incursion rate of 100 lm/s, the maximum values of interaction forces decrease first and then grow with an increase of the blade tip velocity, and the blade tip velocity of 150 m/s becomes the cut-off point between abrasive wear and pattern wear.
基金supports from the National Natural Science Foundation of China (Grant No.11972129)the Natural Science Foundation of Heilongjiang Province (Outstanding Youth Foundation,Grant No.YQ2022A008)the Fundamental Research Funds for the Central Universities.
文摘In this paper,the aero-engine test with inter-shaft bearing fault is carried out,and a dataset is proposed for the first time based on the vibration signal of rotors and casings.First,a test rig based on a real aero-engine is established,driven by motors and equipped with a lubricating system.Then,the aero-engine is disassembled and assembled following the specification process,and the inter-shaft bearing with artificial fault is replaced.Next,the aero-engine test is conducted at 28 groups of high-and low-pressure speeds.Six measuring points are arranged,including two displacement sensors to test the displacement vibration signals of the low-pressure rotor and four acceleration sensors to test the acceleration vibration signals of the casing.The test results are integrated into an inter-shaft bearing fault dataset.Finally,based on the dataset in this paper,frequency spectrum,envelope spectrum,CNN,LSTM,and TST are used for fault diagnosis,and the results are compared with those of CWRU and XJTU datasets.The results show that the characteristic fault frequency cannot be found directly in the spectrum and envelope spectrum corresponding to this paper’s dataset but in CWRU and XJTU datasets.Using CNN,LSTM,and TST for fault diagnosis of the dataset in this paper,the accuracy is 83.13%,85.41%,and 71.07%,respectively,much lower than the diagnosis results of CWRU and XJTU datasets.It can be seen that the dataset in this paper is closer to the actual fault diagnosis situation and is a more challenging dataset.This dataset provides a new benchmark for the validation of fault diagnosis methods.Mendeley data:https://github.com/HouLeiHIT/HIT-dataset.
基金the Science,Research and Innovation Promotion Funding(TSRI)(Grant No.FRB660012/0168)managed under Rajamangala University of Technology Thanyaburi(FRB66E0646O.4).
文摘This study presents the design of a modified attributed control chart based on a double sampling(DS)np chart applied in combination with generalized multiple dependent state(GMDS)sampling to monitor the mean life of the product based on the time truncated life test employing theWeibull distribution.The control chart developed supports the examination of the mean lifespan variation for a particular product in the process of manufacturing.Three control limit levels are used:the warning control limit,inner control limit,and outer control limit.Together,they enhance the capability for variation detection.A genetic algorithm can be used for optimization during the in-control process,whereby the optimal parameters can be established for the proposed control chart.The control chart performance is assessed using the average run length,while the influence of the model parameters upon the control chart solution is assessed via sensitivity analysis based on an orthogonal experimental design withmultiple linear regression.A comparative study was conducted based on the out-of-control average run length,in which the developed control chart offered greater sensitivity in the detection of process shifts while making use of smaller samples on average than is the case for existing control charts.Finally,to exhibit the utility of the developed control chart,this paper presents its application using simulated data with parameters drawn from the real set of data.
基金the Commonwealth of Kentucky,USA through the Energy Independence and Incentives Act of 2007the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,China(Grant No.Z018004).
文摘The Kentucky Geological Survey(KGS)1 Hanson Aggregates stratigraphic research well,Carter County,Kentucky,USA,was drilled to a total depth of 1474 m as a field-scale test of potential CO2 storage reservoir properties in the Central Appalachian Basin.Geomechanical properties of the Rose Run sandstone(upper Ordovician Knox group)were tested for its suitability as a storage reservoir.A 9.8-m thick section of the Rose Run was penetrated at 1000 m drilled depth and a whole-diameter core and rotary sidewall cores were taken.Average porosity and permeability measured in core plugs were 9.1%and 44.6 mD,respectively.Maximum vertical stress gradient calculated in the wellbore was 26 MPa/km.Wellbore fractures in dolomites underlying and overlying the Rose Run follow the contemporary N53E Appalachian Basin stress field.The Rose Run elastic geomechanical properties were calibrated to values measured in core plugs to evaluate its fracturing risk as a CO2 storage reservoir.Mean Young’s modulus and Poisson’s ratio values of the Rose Run were 45 GPa and 0.23,respectively,whereas Young’s modulus and Poisson’s ratio values were 77.1 GPa and 0.28,respectively,in the overlying Beekmantown dolomite,suggesting the Rose Run may fracture if overpressured during CO2 injection but be confined by the Beekmantown.Triaxial compressive strength measured in core plugs found the Rose Run and Beekmantown fractured at mean axial stresses of 156.5 MPa and 282.2 MPa,respectively,confirming the Beekmantown as suitable for confining CO2 injected into the Rose Run.A step-rate test was conducted in a mechanically-isolated 18.6-m interval bracketing the Rose Run.Static Rose Run reservoir pressure was 9.3 MPa,and fracture gradient under injection was 13.6 MPa/km,suggesting step-rate testing before CO2 injection,and subsequent pressure monitoring to ensure confinement.As the region around the KGS 1 Hanson Aggregates well is underpressured and adjacent to faulted Precambrian basement,further research is needed to evaluate its induced seismicity risk during CO2 injection.
基金supported by the Research Major Project of China Academy of Railway Sciences Group Co.,Ltd(Grant No.2021YJ270)the China National Railway Group Science and Technology Program(Grant No.N2022T001).
文摘Purpose-Express freight transportation is in rapid development currently.Owing to the higher speed of express freight train,the deformation of the bridge deck worsens the railway line condition under the action of wind and train moving load when the train runs over a long-span bridge.Besides,the blunt car body of vehicle has poor aerodynamic characteristics,bringing a greater challenge on the running stability in the crosswind.Design/methodology/approach-In this study,the aerodynamic force coefficients of express freight vehicles on the bridge are measured by scale model wind tunnel test.The dynamic model of the train-long-span steel truss bridge coupling system is established,and the dynamic response as well as the running safety of vehicle are evaluated.Findings-The results show that wind speed has a significant influence on running safety,which is mainly reflected in the over-limitation of wheel unloading rate.The wind speed limit decreases with train speed,and it reduces to 18.83 m/s when the train speed is 160 km/h.Originality/value-This study deepens the theoretical understanding of the interaction between vehicles and bridges and proposes new methods for analyzing similar engineering problems.It also provides a new theoretical basis for the safety assessment of express freight trains.
基金Acknowledgements The supports provided for the paper by the National Natural Science Foundation of China （Grant No. 50778019） and the Natural Science Foundation of Beijing （Grant No. 8092024） are gratefully appreciated.
文摘The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced firstly. The displacement time histories are then used to analyze the dynamic property such as fundamental frequency of vertical vibration and damping ratio of the test structure, and the acceleration time histories are applied to evaluate the floor vibration serviceability. The floor interaction and comparison of human walking and running are also discussed. Some valuable conclusions are given.
基金Supported by the National Natural Science Fund of China (No.60876028)the key Project of Natural Science Foundation of the Anhui Higher Education Institutions (No.KJ2010A280)
文摘The pattern run-length coding test data compression approach is extended by introducing don't care bit(x) propagation strategy into it.More than one core test sets for testing core-based System-on-Chip(SoC) are unified into a single one,which is compressed by the extended coding technique.A reconfigurable scan test application mechanism is presented,in which test data for multiple cores are scanned and captured jointly to make SoC test application more efficient with low hardware overhead added.The proposed union test technique is applied to an academic SoC embedded by six large ISCAS'89 benchmarks,and to an ITC' 02 benchmark circuit.Experiment results show that compared with the existing schemes in which a core test set is compressed and applied independently of other cores,the proposed scheme can not only improve test data compression/decompression,but also reduce the redundant shift and capture cycles during scan testing,decreasing SoC test application time effectively.
基金supported by the Shenzhen Government R&D Project under Grant No.JC200903160361A
文摘The test vector compression is a key technique to reduce IC test time and cost since the explosion of the test data of system on chip （SoC） in recent years. To reduce the bandwidth requirement between the automatic test equipment （ATE） and the CUT （circuit under test） effectively, a novel VSPTIDR （variable shifting prefix-tail identifier reverse） code for test stimulus data compression is designed. The encoding scheme is defined and analyzed in detail, and the decoder is presented and discussed. While the probability of 0 bits in the test set is greater than 0.92, the compression ratio from VSPTIDR code is better than the frequency-directed run-length （FDR） code, which can be proved by theoretical analysis and experiments. And the on-chip area overhead of VSPTIDR decoder is about 15.75 % less than the FDR decoder.
