The accurate measurement of volume fraction of oil-water two-phase flow on line is important in the oil field.This paper presents a new coaxial conductivity sensor for measuring the volume fraction of oil-water two-ph...The accurate measurement of volume fraction of oil-water two-phase flow on line is important in the oil field.This paper presents a new coaxial conductivity sensor for measuring the volume fraction of oil-water two-phase flow.This structure may get the more uniform sensitivity field and the vertical installation may get the more axial symmetry of the flow field,which improve the measurement accuracy.In order to minimize the influence of the edge effect,guard electrodes were designed.An anti-edge effect degree Ae was defined to optimize the length of the guard electrode.Different models of effective conductivity of two materials were used in calculating the oil volume fraction of oil-water two-phase flow.The experimental results indicate that Maxwell model is the best model under the condition of oil volume fraction less than 50%and the mean value of the calculation results using Maxwell model and Bruggeman model possesses higher accuracy in the range of oil volume fraction(50%-70%).The experimental results show that the sensor obtains similar measurement performance in both vertical upward and downward flow conditions.The accuracy of the sensor system is 2%when the oil volume fraction less than 50%,and the accuracy is about 5%when the oil volume fraction between 50%and 70%.展开更多
This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put ...This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.展开更多
Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety application...Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety applications.They can even be employed in mining Internet of things if the power consumption can be lowered down to few milliwatts.Many researches of nanomaterialsbased conductive-type methane sensors have been reported recently.This review intends to present a comprehensive and critical summary on the recent progresses in the nanomaterials-based conductive-type methane sensors field.Many excellent methane-sensitive nanomaterials will be present,such as SnO2,ZnO,TiO2,WO3,carbon nanotubes,graphene,rare earth metal-based perovskite oxides and their hybrids.Particular attention is given to the synthetic methods of the nanomaterials,sensing mechanisms of the nanomaterials and the relationship between the sensing performance and the structures and components of the nanomaterials.Finally,the future trends and perspectives of nanomaterials-based conductive-type methane sensors are proposed.展开更多
In the research of 2D flexible tactile sensor matrix,pressure-sensitive conductive rubber was developed and tested in which carbon black was used as its conductive phase and silicon rubber as its matrix layer.Experime...In the research of 2D flexible tactile sensor matrix,pressure-sensitive conductive rubber was developed and tested in which carbon black was used as its conductive phase and silicon rubber as its matrix layer.Experiments were undertaken and the resultant data were used for its piezoresistive characteristics investigation for two kinds of electrode connection configurations,the surface directive connection and embedded connection.It is found that due to the rather strong nonlinearity of the piezoresistive characteristic curves obtained,a higher correlation relationship can be obtained by means of quadratic polynomial fitting.It also showed that the embedded electrode assembling has higher fitting accuracy while the surface directive connection has better mechanical sensitivity.展开更多
Most traditional electrode-based conductivity sensors are made from dense,non-porous,pure platinum material,which tends to accumulate bubbles and contaminants on the surface during testing,limiting the sensitivity and...Most traditional electrode-based conductivity sensors are made from dense,non-porous,pure platinum material,which tends to accumulate bubbles and contaminants on the surface during testing,limiting the sensitivity and stability of the sensors and posing a challenge to the precise detection of marine ions in applications.Pt black is one of the key materials utilized to enhance the interaction between electrodes and tissues due to its excellent electrochemical stabilization properties.However,its practical application is still limited by the properties of the material itself and the lack of suitable material modification techniques.Inspired by the high stability and sensitivity of Pt-black modifications in neural microelectrodes for brain research,this study developed a combined ultrasound and pulse plating technique to deposit a cauliflower-like platinum black(CF-Ptblack)layer on a bare platinum substrate.Compared with bare Pt,the prepared Pt black exhibits significant advantages:superhydrophilicity(contact angle of 34.52°),a 0.7-times reduction in impedance,a 3.54-times increase in charge storage capacity,and excellent mechanical and electrochemical stability.When utilized in marine conductivity sensors,Pt blackmodified electrodes improve the sensor accuracy from 0.0025 to 0.0012 mS/cm and reduce the response time by 160 s.These properties make Pt black an excellent candidate for highprecision ion detection,biosensing,and neural recording.展开更多
This study aimed to obtain the production profiles of oil-in-water flow under low flow rate and high water-cut conditions in oil wells.A combination production profile logging composed of an arc-type conductance senso...This study aimed to obtain the production profiles of oil-in-water flow under low flow rate and high water-cut conditions in oil wells.A combination production profile logging composed of an arc-type conductance sensor(ATCS)and a cross-correlation flow meter(CFM)with a center body is proposed and experimentally evaluated.The ATCS is designed for water holdup measurement,whereas the CFM with a center body is proposed to obtain the mixture velocity.Then,a drift-flux model based on flow patterns is established to predict the individual-phase superficial velocity of oil-in-water flows.Results show that the ATCS possesses high resolution in water holdup measurement and that flow pattern information can be deduced from its signal through nonlinear time series analysis.The CFM can enhance the correlation of upstream and downstream signals and simplify the relationship between the cross-correlation velocity and mixture velocity.On the basis of the drift-flux model,individual-phase superficial velocities can be predicted with high accuracy for different flow patterns.展开更多
This work investigated the potential of metal oxide semiconductor(MOS)gas sensors for environmental monitoring of methane.Calibrations were performed under controlled conditions in the lab,and under semi-controlled co...This work investigated the potential of metal oxide semiconductor(MOS)gas sensors for environmental monitoring of methane.Calibrations were performed under controlled conditions in the lab,and under semi-controlled conditions in the field,using a modified head space chamber set-up.Concentrations up to±300 ppm methane were tested.The relationship between sensor conductance and methane concentrations could be very well described using principles from adsorption theory.The adjustable parameters were background conductance G_(0),a sensitivity constant S and a non-ideality coefficient n,where n has a non-rational value between 0 and 1.Sensor behaviour was very different in dry air than in humid air,with the background conductance increasing approximately tenfold and sensitivity decreasing between 20 fold and 80 fold,while the non-ideality coefficient increased from±0.4 to±0.6.Nevertheless,at high methane concentrations comparable conductance values were recorded in dry and humid air.The standard deviation of predicted values was 1.6μS.for the least well described dataset.Using the corresponding calibration curve,a detection limit of 11 ppm is calculated for humid ambient air.This values suggests that MOS sensor are adequately sensitive to be used for methane detection in an agricultural context.展开更多
Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.C...Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.Conventional TCDs use steady-state resistance(i.e.,temperature)measurements of a micro-heater.In this work,we developed a new measurement method and hardware configuration based on the processing of the transient response of a low thermal mass TCD to an electric current step.The method was implemented for a 100-μm-long and 1-μm-thick micro-fabricated bridge that consisted of doped polysilicon conductive film passivated with a 200-nm silicon nitride layer.Transient resistance variations of theμTCD in response to a square current pulse were studied in multiple mixtures of dilute gases in nitrogen.Simulations and experimental results are presented and compared for the time resolved and steady-state regime of the sensor response.Thermal analysis and simulation show that the sensor response is exponential in the transient state,that the time constant of this exponential variation was a linear function of the thermal conductivity of the gas ambient,and that the sensor was able to quantify the mixture composition.The level of detection in nitrogen was estimated to be from 25 ppm for helium to 178 ppm for carbon dioxide.With this novel approach,the sensor requires approximately 3.6 nJ for a single measurement and needs only 300μs of sampling time.This is less than the energy and time required for steady-state DC measurements.展开更多
基金supported by National Natural Science Foundation of China(Grant No.61072101)Program for New Century Excellent Talents in University(Grant No.NCET-10-0621)the Independent Innovation Foundation of Tianjin University
文摘The accurate measurement of volume fraction of oil-water two-phase flow on line is important in the oil field.This paper presents a new coaxial conductivity sensor for measuring the volume fraction of oil-water two-phase flow.This structure may get the more uniform sensitivity field and the vertical installation may get the more axial symmetry of the flow field,which improve the measurement accuracy.In order to minimize the influence of the edge effect,guard electrodes were designed.An anti-edge effect degree Ae was defined to optimize the length of the guard electrode.Different models of effective conductivity of two materials were used in calculating the oil volume fraction of oil-water two-phase flow.The experimental results indicate that Maxwell model is the best model under the condition of oil volume fraction less than 50%and the mean value of the calculation results using Maxwell model and Bruggeman model possesses higher accuracy in the range of oil volume fraction(50%-70%).The experimental results show that the sensor obtains similar measurement performance in both vertical upward and downward flow conditions.The accuracy of the sensor system is 2%when the oil volume fraction less than 50%,and the accuracy is about 5%when the oil volume fraction between 50%and 70%.
文摘This paper analysis the developing of expendable conductivity temperature depth measuring system(XCTD)and introduce its principle of measuring about temperature,salinity and depth of ocean.Some key techniques are put forward.According to the real needs of XCTD,conductivity sensor with high sensitivity is designed by principle of electromagnetic induce,the ocean conductivity from induced electromotive force has been calculated.Adding temperature correction circuit would help to reduce error of conductivity measurement because of sharply changing temperature.Advanced temperature measuring circuit of high precision and the constant current source is used to weaken effect of self-heating of resistance and fluctuation of the source.On respect of remote data transmission,LVDS is a good choice for the purpose of guarantee the quality of data transmitted and the transmission distance is reaching to thousand meters in the seawater.Modular programming method is also brought into this research aimed at improve the stability,reliability and maintainability of the whole measuring system.In February,2015,the trials in South China Sea demonstrate that the developed XCTD realize effective measurement at a speed of 6 knots and detection depth at 800 m.The consistency coefficient of the acquired data is greater than 0.99 and the success rate of probe launching is above 90%.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.2020QN69)。
文摘Methane is an explosive gas in coalmines and needs to be monitored by methane sensors.Conductivetype methane sensors are small,simple and stable,and they are very promising for mining safety or home safety applications.They can even be employed in mining Internet of things if the power consumption can be lowered down to few milliwatts.Many researches of nanomaterialsbased conductive-type methane sensors have been reported recently.This review intends to present a comprehensive and critical summary on the recent progresses in the nanomaterials-based conductive-type methane sensors field.Many excellent methane-sensitive nanomaterials will be present,such as SnO2,ZnO,TiO2,WO3,carbon nanotubes,graphene,rare earth metal-based perovskite oxides and their hybrids.Particular attention is given to the synthetic methods of the nanomaterials,sensing mechanisms of the nanomaterials and the relationship between the sensing performance and the structures and components of the nanomaterials.Finally,the future trends and perspectives of nanomaterials-based conductive-type methane sensors are proposed.
基金Funded by the National Natural Science Foundation of China(No.60672024)National High Technology Research and Development Program of China (No.2007AA04Z220)
文摘In the research of 2D flexible tactile sensor matrix,pressure-sensitive conductive rubber was developed and tested in which carbon black was used as its conductive phase and silicon rubber as its matrix layer.Experiments were undertaken and the resultant data were used for its piezoresistive characteristics investigation for two kinds of electrode connection configurations,the surface directive connection and embedded connection.It is found that due to the rather strong nonlinearity of the piezoresistive characteristic curves obtained,a higher correlation relationship can be obtained by means of quadratic polynomial fitting.It also showed that the embedded electrode assembling has higher fitting accuracy while the surface directive connection has better mechanical sensitivity.
基金supported by the National Key Research and Development Program of China(2023YFB3208004)Xiamen Marine Development Bureau Project(22CFW010HJ12)+2 种基金Key R&D Plan of Hainan Province(ZDYF2023GXJS013)National Key Research and Development Program of China(2022YFB3205300)Postgraduate Research Innovation Project of Shanxi Province(2024KY583)。
文摘Most traditional electrode-based conductivity sensors are made from dense,non-porous,pure platinum material,which tends to accumulate bubbles and contaminants on the surface during testing,limiting the sensitivity and stability of the sensors and posing a challenge to the precise detection of marine ions in applications.Pt black is one of the key materials utilized to enhance the interaction between electrodes and tissues due to its excellent electrochemical stabilization properties.However,its practical application is still limited by the properties of the material itself and the lack of suitable material modification techniques.Inspired by the high stability and sensitivity of Pt-black modifications in neural microelectrodes for brain research,this study developed a combined ultrasound and pulse plating technique to deposit a cauliflower-like platinum black(CF-Ptblack)layer on a bare platinum substrate.Compared with bare Pt,the prepared Pt black exhibits significant advantages:superhydrophilicity(contact angle of 34.52°),a 0.7-times reduction in impedance,a 3.54-times increase in charge storage capacity,and excellent mechanical and electrochemical stability.When utilized in marine conductivity sensors,Pt blackmodified electrodes improve the sensor accuracy from 0.0025 to 0.0012 mS/cm and reduce the response time by 160 s.These properties make Pt black an excellent candidate for highprecision ion detection,biosensing,and neural recording.
基金supported by the National Natural Science Foundation of China(Nos.51527805 and 11572220)
文摘This study aimed to obtain the production profiles of oil-in-water flow under low flow rate and high water-cut conditions in oil wells.A combination production profile logging composed of an arc-type conductance sensor(ATCS)and a cross-correlation flow meter(CFM)with a center body is proposed and experimentally evaluated.The ATCS is designed for water holdup measurement,whereas the CFM with a center body is proposed to obtain the mixture velocity.Then,a drift-flux model based on flow patterns is established to predict the individual-phase superficial velocity of oil-in-water flows.Results show that the ATCS possesses high resolution in water holdup measurement and that flow pattern information can be deduced from its signal through nonlinear time series analysis.The CFM can enhance the correlation of upstream and downstream signals and simplify the relationship between the cross-correlation velocity and mixture velocity.On the basis of the drift-flux model,individual-phase superficial velocities can be predicted with high accuracy for different flow patterns.
基金supported by the European Union’s Horizon 2020 research and innovation programme[grant agreement No.825325].
文摘This work investigated the potential of metal oxide semiconductor(MOS)gas sensors for environmental monitoring of methane.Calibrations were performed under controlled conditions in the lab,and under semi-controlled conditions in the field,using a modified head space chamber set-up.Concentrations up to±300 ppm methane were tested.The relationship between sensor conductance and methane concentrations could be very well described using principles from adsorption theory.The adjustable parameters were background conductance G_(0),a sensitivity constant S and a non-ideality coefficient n,where n has a non-rational value between 0 and 1.Sensor behaviour was very different in dry air than in humid air,with the background conductance increasing approximately tenfold and sensitivity decreasing between 20 fold and 80 fold,while the non-ideality coefficient increased from±0.4 to±0.6.Nevertheless,at high methane concentrations comparable conductance values were recorded in dry and humid air.The standard deviation of predicted values was 1.6μS.for the least well described dataset.Using the corresponding calibration curve,a detection limit of 11 ppm is calculated for humid ambient air.This values suggests that MOS sensor are adequately sensitive to be used for methane detection in an agricultural context.
基金The sensor that was tested in this work is based on the patents:No.7,911,010,No.8,426,932 and No.8,884,382.
文摘Micro-thermal conductivity detector(μTCD)gas sensors work by detecting changes in the thermal conductivity of the surrounding medium and are used as detectors in many applications such as gas chromatography systems.Conventional TCDs use steady-state resistance(i.e.,temperature)measurements of a micro-heater.In this work,we developed a new measurement method and hardware configuration based on the processing of the transient response of a low thermal mass TCD to an electric current step.The method was implemented for a 100-μm-long and 1-μm-thick micro-fabricated bridge that consisted of doped polysilicon conductive film passivated with a 200-nm silicon nitride layer.Transient resistance variations of theμTCD in response to a square current pulse were studied in multiple mixtures of dilute gases in nitrogen.Simulations and experimental results are presented and compared for the time resolved and steady-state regime of the sensor response.Thermal analysis and simulation show that the sensor response is exponential in the transient state,that the time constant of this exponential variation was a linear function of the thermal conductivity of the gas ambient,and that the sensor was able to quantify the mixture composition.The level of detection in nitrogen was estimated to be from 25 ppm for helium to 178 ppm for carbon dioxide.With this novel approach,the sensor requires approximately 3.6 nJ for a single measurement and needs only 300μs of sampling time.This is less than the energy and time required for steady-state DC measurements.
