Multi-orifice cross-flow jet mixers(MOCJMs)are used in various industrial applications due to their excellent mixing efficiency,but few studies have focused on the micromixing performance of MOCJMs.Herein,the flow cha...Multi-orifice cross-flow jet mixers(MOCJMs)are used in various industrial applications due to their excellent mixing efficiency,but few studies have focused on the micromixing performance of MOCJMs.Herein,the flow characteristics and micromixing performance inside the MOCJM were investigated using experiments and computational fluid dynamics(CFD)simulations based on the Villermaux/Dushman system and the finite-rate/modified eddy-dissipation model.The optimal A value was correlated with the characteristic parameters of MOCJMs to develop a CFD calculation method applicable to the study of the micromixing performance of the MOCJMs.Then the micromixing efficiency was evaluated using the segregation index XS,and the effects of operational and geometric parameters such as mixing flow Reynolds number(ReM),flow ratio(RF),total jet area(ST),the number of jet orifices(n),and outlet configuration on the micromixing efficiency were investigated.It was found that the intensive turbulent region generated by interactions between jets,as well as between jets and crossflows,facilitated rapid reactions.XS decreased with increasing ReM and decreasing RF.Furthermore,MOCJMs with lower ST,four jet orifices,and the narrower outlet configuration demonstrated a better micromixing efficiency.This study contributes to a deeper understanding of the micromixing performance of MOCJMs and provides valuable guidance for their design,optimization,and industrial application.展开更多
The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only...The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.展开更多
Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)softwar...Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.展开更多
This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric mixer.Fluid rheology was described by the power law rheologi...This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric mixer.Fluid rheology was described by the power law rheological model.Computational fluid dynamics was employed to simulate the velocity field and shear rate inside the stirred tank.The influence mechanism of the rotational modes,height difference between impellers,impeller eccentricities,and impeller types on the flow field have been well investigated.We studied the performance of different dual-shaft eccentric mixers at the constant power input with its fluid velocity profiles,average shear strain rate,mixing time and mixing energy.The counter-rotation mode shows better mixing performance than co-rotation mode,and greater eccentricity can shorten mixing time on the basis of same stirred condition.To intensify the hydrodynamic interaction between impellers and enhance the overall mixing performance of the dual shaft eccentric mixers,it is critical to have a reasonable combination of impellers and an appropriate spatial position of impellers.展开更多
Based on the analyses of the reported Gilbert mixers operating at low supply vol tage,a down-conversion mixer and an up-conversion mixer for 2.4GHz bluetooth transceiver are presented with the modified low voltage de...Based on the analyses of the reported Gilbert mixers operating at low supply vol tage,a down-conversion mixer and an up-conversion mixer for 2.4GHz bluetooth transceiver are presented with the modified low voltage design techniques,respe ctively.Feedback and current mirror techniques suitable for low voltage operatio n are used to improve the linearity of the up-conversion mixer,and folded-casc ode output stage is adopted to optimize the noise and conversion gain of the dow n-conversion mixer operating at low voltage.Based on 0.35μm CMOS technology,s imulations are performed with 2V supply voltage.The results show that 20dBm thir d-order intercept point (IIP3),87mV output signal amplitude are achieved for up -conversion mixer with about 3mA current;while 20dB conversion gain (CG),6.5nV /Hz input-referred noise,4.4dBm IIP3 are obtained for down-conversion mixer with about 3.5mA current.展开更多
A down-conversion mixer and an up-conversion mixer for 2.4GHz WLAN transceivers are presented.The down-conversion mixer uses a class-AB input stage to get high linearity and to realize input impedance matching and sin...A down-conversion mixer and an up-conversion mixer for 2.4GHz WLAN transceivers are presented.The down-conversion mixer uses a class-AB input stage to get high linearity and to realize input impedance matching and single-ended to differential conversion.The mixers are implemented in 0.18μm CMOS process.The measured results are given to show their performance.展开更多
This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine(PBT)-helical ribbon...This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine(PBT)-helical ribbon(HR)and inner-outer HR operated in laminar regime were studied experimentally and numerically. The interaction implies synergistic and interference effects, which was revealed through the investigation of axial circulation rate, energy dissipation rate and power consumption. The influence factors including rotational speed ratio,rotating mode and impeller configuration were explored systematically. Quantitative analysis of power consumption involves three parameters: rate of variation in power consumption, interactive mode and ratio of power consumption. Analysis indicated that some important properties were embodied in the power curve.These properties are one-way and two-way interactions, critical speed ratio and dominant impeller. Finally, a new suggestion for power estimation was given.展开更多
The present study is concerned with the computational fluid dynamics(CFD)simulation of turbulent dispersion of immiscible liquids,namely,water–silicone oil and water–benzene through Kenics static mixers using the Eu...The present study is concerned with the computational fluid dynamics(CFD)simulation of turbulent dispersion of immiscible liquids,namely,water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software.To study the droplet size distribution(DSD),the Eulerian formulation incorporating a population balance model(PBM)was employed.For the Eulerian–Lagrangian approach,a discrete phase model(DPM)in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution(RTD)of droplets.In both approaches,a shear stress transport(SST)k-ωturbulence model was used.For validation purposes,the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor,Sauter mean diameter and the mean residence time.The reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean diameter.In addition,the influence of important geometrical and operational parameters,including the number of mixing elements and Weber number,was studied.It was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.展开更多
The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160.The performance of the new mixer is compared with those of ...The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160.The performance of the new mixer is compared with those of Kenics,SMX,and Komax static mixers.The pressure drop ratio(Z-factor),coefficient of variation(CoV),and extensional efficiency(α)features have been used to evaluate power consumption,distributive mixing,and dispersive mixing performances,respectively,in all mixers.The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation.CFD results are consistent with measured data and those obtained by available correlations in the literature.The new mixer shows a superior mixing performance compared to the other mixers.展开更多
The mechanically stirred internal loop airlift reactors equipped with or without static mixers are devised for intensification of gas-liquid mass transfer rate. The influences of superficial gas velocity, agitation o...The mechanically stirred internal loop airlift reactors equipped with or without static mixers are devised for intensification of gas-liquid mass transfer rate. The influences of superficial gas velocity, agitation or static mixers on gas hold-up, mixing time, liquid circulating velocity and volumetric mass transfer coefficient have been investigated with tap water and carboxymethyl cellulose (CMC) aqueous solution. The experimental results indicate that mechanical agitation is more efficacious than static mixer in highly viscous media for improving mass transfer in airlift reactors. The empirical correlation of volumetric mass transfer coefficient with apparent viscosity, and energy consumption for mechanical agitation and aeration is developed.展开更多
1 INTRODUCTIONUse of static mixers to process non-Newtonian fluids is quite commn.Data on thepressure drop of non-Newtonian fluids in Kenics static mixers are very useful in thedesign and engineering application of su...1 INTRODUCTIONUse of static mixers to process non-Newtonian fluids is quite commn.Data on thepressure drop of non-Newtonian fluids in Kenics static mixers are very useful in thedesign and engineering application of such mixers.However,only a few studies con-cerned with the pressure drop of non-Newtonian fluid flow in static ndxers can befound in literature.Wilkinson and Cliff presented pressure drop data for aqueousglycerine solutions(Newtonian fluids)and aqueous 1% polyacrylamide solution showingviscoelastic behavior.They found no difference between the friction factors of展开更多
This paper presents the design and simulation of several fixed-tuned sub-harmonic mixers cover frequencies from 110 GH to 130 GHz, 215 GH to 235 GHz, 310 GH to 350 GHz, and 400 GH to 440 GHz. Among them, 120 GHz, 225 ...This paper presents the design and simulation of several fixed-tuned sub-harmonic mixers cover frequencies from 110 GH to 130 GHz, 215 GH to 235 GHz, 310 GH to 350 GHz, and 400 GH to 440 GHz. Among them, 120 GHz, 225 GHz, 330 GHz subharmonic mixers are designed with flip-chipped planar schottky diode mounted onto a suspended quartz-based substrate, the 225 GHz and 425 GHz subharmonic mixers are GaAs membrane integrated, and the 115 GHz subharmonic mixer has been fabricated and tested already.展开更多
How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.A typical multistage rotor-stator mixer(MRSM)equipped with a di...How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.A typical multistage rotor-stator mixer(MRSM)equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation,considering the influence factors associated with different geometric parameters of both MRSM and the distributor.The mixing index and power consumption are used to evaluate the performance of the mixers.The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate,rotor speed,the number of mixing units.Adopting the optimized mixer with the distributor(X1-T1),the mixing index increases to 0.85(obviously higher than 0.46 for the mixer T1 without a distributor),meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect.It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption.These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.展开更多
We investigate the performances of the pairwise correlations(PCs) in different quantum networks consisting of fourwave mixers(FWMs) and beamsplitters(BSs). PCs with quantum correlation in different quantum netwo...We investigate the performances of the pairwise correlations(PCs) in different quantum networks consisting of fourwave mixers(FWMs) and beamsplitters(BSs). PCs with quantum correlation in different quantum networks can be verified by calculating the degree of relative intensity squeezing for any pair of all the output fields. More interestingly, the quantum correlation recovery and enhancement are present in the FWM+BS network and the repulsion effect phenomena(signal(idler)-frequency mode cannot be quantum correlated with the other two idler(signal)-frequency modes simultaneously)between the PCs with quantum correlation are predicted in the FWM + FWM and FWM + FWM + FWM networks. Our results presented here pave the way for the manipulation of the quantum correlation in quantum networks.展开更多
We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-...We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.展开更多
This paper presents a 220-GHz-band 7-m wireless link with a 45-Gbps transmission data rate by using 16 quadrature amplitude modulation(16-QAM).Super-heterodyne transceiver modules are developed for transmission and re...This paper presents a 220-GHz-band 7-m wireless link with a 45-Gbps transmission data rate by using 16 quadrature amplitude modulation(16-QAM).Super-heterodyne transceiver modules are developed for transmission and reception of the modulated signals,which consist of a Schottky barrier diodes(SBD)based sub-harmonic mixer(SHM),an InP HEMT low noise amplifier(LNA),a waveguide band-pass filter(BPF),and a 108-GHz local oscillator(LO)multiplier chain.The transmitter features a peak transmit power of 1.41 dBm,and the IF frequency varies from 5 GHz to 20 GHz.Besides,the receiver features a conversion gain of 9.3 dB in average and a noise temperature of 3052.8 K.The measured results indicate that the transceiver modules enable data transmission of a 45-Gbps 16-QAM signal with Signal-Noise-Ratio(SNR)from 11.59 dB to 15.36 dB in a 7-m line-of-sight channel.展开更多
We propose a convenient way of evaluating the mixing performance of static mixers used for round pipe by conducting flow visualization experiments under the turbulent region and using water as the main stream. A fluor...We propose a convenient way of evaluating the mixing performance of static mixers used for round pipe by conducting flow visualization experiments under the turbulent region and using water as the main stream. A fluorescent pigment, glycerin, two carboxymethyl cellulose solutions, and rapeseed oil were each injected upstream of the mixer. Three static mixer conditions were tested: 1) no static mixer;2) a Kenics-type static mixer;and 3) a multi-stacked elements (MSE) static mixer. The mixing trend downstream of the mixer in each condition and with each injection fluid was monitored using a laser and high-speed video camera system to obtain cross-sectional images. We propose suitable indexes based on the images obtained for quantitative evaluations of the mixing characteristics of static mixers.展开更多
Mixers in the communication system provide the possibility of encoding and decoding radio-frequency EM waves with signals through the help of local oscillators. A mixer with capability of high conversion gain, good is...Mixers in the communication system provide the possibility of encoding and decoding radio-frequency EM waves with signals through the help of local oscillators. A mixer with capability of high conversion gain, good isolation, and good linearity is comparably appreciated. Extensively wide ranges of frequencies, from 5.0 to 18.0 GHz, are to be examined addressing the promising functions of mixers in this study. A TSMC 0.18 μm CMOS model implanted in Agilent ADS is used for the circuit designs. Generated from Gilbert Cell Mixer, the modified circuits take advantage of extra active and passive devices to optimize the conversion gains. Characteristics of high conversion gain over 20 dB or even higher (as high as 29.842 dB at -40 mW RF power at working frequency 6 GHz) and low noise figures (NF) are shown.展开更多
Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its d...Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.展开更多
The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environmen...The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.展开更多
基金the financial support from the Shanghai Sailing Program,China(21YF1409500)the National Natural Science Foundation of China(22308100,22308105)+1 种基金the State Key Laboratory of Chemical Engineering(SKL-ChE-23Z01)the National Science Fund for Distinguished Young Scholars of China(22225804).
文摘Multi-orifice cross-flow jet mixers(MOCJMs)are used in various industrial applications due to their excellent mixing efficiency,but few studies have focused on the micromixing performance of MOCJMs.Herein,the flow characteristics and micromixing performance inside the MOCJM were investigated using experiments and computational fluid dynamics(CFD)simulations based on the Villermaux/Dushman system and the finite-rate/modified eddy-dissipation model.The optimal A value was correlated with the characteristic parameters of MOCJMs to develop a CFD calculation method applicable to the study of the micromixing performance of the MOCJMs.Then the micromixing efficiency was evaluated using the segregation index XS,and the effects of operational and geometric parameters such as mixing flow Reynolds number(ReM),flow ratio(RF),total jet area(ST),the number of jet orifices(n),and outlet configuration on the micromixing efficiency were investigated.It was found that the intensive turbulent region generated by interactions between jets,as well as between jets and crossflows,facilitated rapid reactions.XS decreased with increasing ReM and decreasing RF.Furthermore,MOCJMs with lower ST,four jet orifices,and the narrower outlet configuration demonstrated a better micromixing efficiency.This study contributes to a deeper understanding of the micromixing performance of MOCJMs and provides valuable guidance for their design,optimization,and industrial application.
基金wasfinancially aided by the National Natural Science Foundation of China(52276122).
文摘The proper selection of a relevant mixer generally requires an effective assessment of several models against theapplication requirements. This is a complex task, as traditional evaluation methods generally focus only on a single aspect of performance, such as pressure loss, mixing characteristics, or heat transfer. This study assesses aurea-based selective catalytic reduction (SCR) system installed on a ship, where the installation space is limitedand the distance between the urea aqueous solution injection position and the reactor is low;therefore, the staticmixer installed in this pipeline has special performance requirements. In particular, four evaluation indices areused in this study: The B value, C value, pressure loss correction factor (Z′), and the ratio of the required distanceto the equivalent diameter of the pipe (LV/D) when the velocity field after the mixer attains uniformity. Six typesof static mixers were simulated with varying concentrations, flow speeds, and positions. A fuzzy comprehensiveevaluation method was introduced to evaluate and compare the related advantages and disadvantages. The resultsshowed that 1) mixing performance was related to the shape of the mixer and had no direct relationship with flowvelocity. 2) For the same mixer position, the lower the urea concentration, the greater the difficulty of evenly mixing the solution. 3) At a constant urea concentration, the mixing performance improved when the mixer was closer to the injection inlet. 4) The installation of a GK mixer in the SCR system of a 9L20C diesel engine was best.
文摘Two types of tightly coupled Selective Catalytic Reduction(SCR)mixers were designed in this study,namely Mixer 1 integrated with an SCR catalyst and Mixer 2 arranged separately.Computational Fluid Dynamics(CFD)software was utilized to model the gas flow,spraying,and pyrolysis reaction of the aqueous urea solution in the tightly coupled SCR system.The parameters of gas flow velocity uniformity and ammonia distribution uniformity were simulated and calculated for both Mixer 1 and Mixer 2 in the tightly coupled SCR system to compare their advantages and disadvantages.The simulation results indicated that Mixer 1 exhibited a gas velocity uniformity of 0.972 and an ammonia distribution uniformity of 0.817,whereas Mixer 2 demonstrated a gas velocity uniformity of 0.988 and an ammonia distribution uniformity of 0.964.Mixer 2 performed better in the simulation analysis.Furthermore,a 3D-printed prototype of Mixer 2 was manufactured and installed on an engine test bench to investigate ammonia distribution uniformity and NOX conversion efficiency.The experimental investigations yielded the following findings:1)The ammonia distribution uniformity of Mixer 2 was measured as 0.976,which closely aligned with the simulation result of 0.964,with a deviation of 1.2%from the model calculations;2)As exhaust temperature increased,the ammonia distribution uniformity gradually improved,while an increase in exhaust flow rate resulted in a decrease in ammonia distribution uniformity;3)When utilizing Mixer 2,the NOX conversion efficiency reached 84.7%at an exhaust temperature of 200°C and 97.4%at 250°C.Within the exhaust temperature range of 300°C to 450°C,the NOX conversion efficiency remained above 98%.This study proposed two innovative mixer structures,conducted simulation analysis,and performed performance testing.The research outcomes indicated that the separately arranged Mixer 2 exhibited superior performance.The tightly coupled SCR systemequippedwith Mixer 2 achieved excellent levels of gas velocity uniformity,ammonia distribution uniformity,and NOX conversion efficiency.These findings can serve as valuable references for the design and development of ultra-low emission after-treatment systems for diesel engines in the field of diesel engine aftertreatment.
基金supported by the National Natural Science Foundation of China(22078030,52021004)National Natural Science Foundation of Chongqing(2022NSCQ-LZX0271)+2 种基金Fundamental Research Funds for the Central Universities(2022CDJQY-005)National Key Research and Development Project(2019YFC1905802,2022YFC3901204)Key Project of Independent Research Project of State Key Laboratory of coal mine disaster dynamics and control(2011DA105287-zd201902).
文摘This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric mixer.Fluid rheology was described by the power law rheological model.Computational fluid dynamics was employed to simulate the velocity field and shear rate inside the stirred tank.The influence mechanism of the rotational modes,height difference between impellers,impeller eccentricities,and impeller types on the flow field have been well investigated.We studied the performance of different dual-shaft eccentric mixers at the constant power input with its fluid velocity profiles,average shear strain rate,mixing time and mixing energy.The counter-rotation mode shows better mixing performance than co-rotation mode,and greater eccentricity can shorten mixing time on the basis of same stirred condition.To intensify the hydrodynamic interaction between impellers and enhance the overall mixing performance of the dual shaft eccentric mixers,it is critical to have a reasonable combination of impellers and an appropriate spatial position of impellers.
文摘Based on the analyses of the reported Gilbert mixers operating at low supply vol tage,a down-conversion mixer and an up-conversion mixer for 2.4GHz bluetooth transceiver are presented with the modified low voltage design techniques,respe ctively.Feedback and current mirror techniques suitable for low voltage operatio n are used to improve the linearity of the up-conversion mixer,and folded-casc ode output stage is adopted to optimize the noise and conversion gain of the dow n-conversion mixer operating at low voltage.Based on 0.35μm CMOS technology,s imulations are performed with 2V supply voltage.The results show that 20dBm thir d-order intercept point (IIP3),87mV output signal amplitude are achieved for up -conversion mixer with about 3mA current;while 20dB conversion gain (CG),6.5nV /Hz input-referred noise,4.4dBm IIP3 are obtained for down-conversion mixer with about 3.5mA current.
文摘A down-conversion mixer and an up-conversion mixer for 2.4GHz WLAN transceivers are presented.The down-conversion mixer uses a class-AB input stage to get high linearity and to realize input impedance matching and single-ended to differential conversion.The mixers are implemented in 0.18μm CMOS process.The measured results are given to show their performance.
基金Supported by the Shanghai Institute of Technology(10120K146098)Shanghai Municipal Education Commission(1021ZK151009017)
文摘This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine(PBT)-helical ribbon(HR)and inner-outer HR operated in laminar regime were studied experimentally and numerically. The interaction implies synergistic and interference effects, which was revealed through the investigation of axial circulation rate, energy dissipation rate and power consumption. The influence factors including rotational speed ratio,rotating mode and impeller configuration were explored systematically. Quantitative analysis of power consumption involves three parameters: rate of variation in power consumption, interactive mode and ratio of power consumption. Analysis indicated that some important properties were embodied in the power curve.These properties are one-way and two-way interactions, critical speed ratio and dominant impeller. Finally, a new suggestion for power estimation was given.
文摘The present study is concerned with the computational fluid dynamics(CFD)simulation of turbulent dispersion of immiscible liquids,namely,water–silicone oil and water–benzene through Kenics static mixers using the Eulerian–Eulerian and Eulerian–Lagrangian approaches of the ANSYS Fluent 16.0 software.To study the droplet size distribution(DSD),the Eulerian formulation incorporating a population balance model(PBM)was employed.For the Eulerian–Lagrangian approach,a discrete phase model(DPM)in conjunction with the Eulerian approach for continuous phase simulation was used to predict the residence time distribution(RTD)of droplets.In both approaches,a shear stress transport(SST)k-ωturbulence model was used.For validation purposes,the simulated results were compared with the experimental data and theoretical values for the Fanning friction factor,Sauter mean diameter and the mean residence time.The reliability of the computational model was further assessed by comparing the results with the available empirical correlations for Fanning friction factor and Sauter mean diameter.In addition,the influence of important geometrical and operational parameters,including the number of mixing elements and Weber number,was studied.It was found that the proposed models are capable of predicting the performance of the Kenics static mixer reasonably well.
文摘The flow and mixing behavior of two miscible liquids has been studied in an innovative static mixer by using CFD,with Reynolds numbers ranging from 20 to 160.The performance of the new mixer is compared with those of Kenics,SMX,and Komax static mixers.The pressure drop ratio(Z-factor),coefficient of variation(CoV),and extensional efficiency(α)features have been used to evaluate power consumption,distributive mixing,and dispersive mixing performances,respectively,in all mixers.The model is firstly validated based on experimental data measured for the pressure drop ratio and the coefficient of variation.CFD results are consistent with measured data and those obtained by available correlations in the literature.The new mixer shows a superior mixing performance compared to the other mixers.
文摘The mechanically stirred internal loop airlift reactors equipped with or without static mixers are devised for intensification of gas-liquid mass transfer rate. The influences of superficial gas velocity, agitation or static mixers on gas hold-up, mixing time, liquid circulating velocity and volumetric mass transfer coefficient have been investigated with tap water and carboxymethyl cellulose (CMC) aqueous solution. The experimental results indicate that mechanical agitation is more efficacious than static mixer in highly viscous media for improving mass transfer in airlift reactors. The empirical correlation of volumetric mass transfer coefficient with apparent viscosity, and energy consumption for mechanical agitation and aeration is developed.
文摘1 INTRODUCTIONUse of static mixers to process non-Newtonian fluids is quite commn.Data on thepressure drop of non-Newtonian fluids in Kenics static mixers are very useful in thedesign and engineering application of such mixers.However,only a few studies con-cerned with the pressure drop of non-Newtonian fluid flow in static ndxers can befound in literature.Wilkinson and Cliff presented pressure drop data for aqueousglycerine solutions(Newtonian fluids)and aqueous 1% polyacrylamide solution showingviscoelastic behavior.They found no difference between the friction factors of
基金supported by the National Natural Science Foundation of China under Grant No.61301051
文摘This paper presents the design and simulation of several fixed-tuned sub-harmonic mixers cover frequencies from 110 GH to 130 GHz, 215 GH to 235 GHz, 310 GH to 350 GHz, and 400 GH to 440 GHz. Among them, 120 GHz, 225 GHz, 330 GHz subharmonic mixers are designed with flip-chipped planar schottky diode mounted onto a suspended quartz-based substrate, the 225 GHz and 425 GHz subharmonic mixers are GaAs membrane integrated, and the 115 GHz subharmonic mixer has been fabricated and tested already.
基金financially supported by the National Natural Science Foundation of China (22090034, 21776179)the Major Science and Technology Project of Xinjiang Bingtuan(2020AA004)the Major Project of Shihezi City(2020ZD002)
文摘How to achieve uniform mixing of highly viscous fluids with low energy consumption is a major industry demand and one of the hot spots of mixing research.A typical multistage rotor-stator mixer(MRSM)equipped with a distributor was investigated to disclose the effects on the mixing performance and power consumption for highly viscous fluids via numerical simulation,considering the influence factors associated with different geometric parameters of both MRSM and the distributor.The mixing index and power consumption are used to evaluate the performance of the mixers.The dimensionless correlations for the mixing index and the power consumption are established considering the factors including the flow rate,rotor speed,the number of mixing units.Adopting the optimized mixer with the distributor(X1-T1),the mixing index increases to 0.85(obviously higher than 0.46 for the mixer T1 without a distributor),meanwhile the corresponding power consumption is about 1/5 of that of T1 achieving the same mixing effect.It illustrates that the distributor can significantly improve the mixing of highly viscous fluids in the MRSM without the cost of large power consumption.These results would provide a guidance on the design and optimization of multistage rotor-stator mixers in industrial applications.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.91436211,11374104,and 10974057)the Natural Science Foundation of Shanghai,China(Grant No.17ZR1442900)+5 种基金the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20130076110011)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,the Program for New Century Excellent Talents in University,China(Grant No.NCET-10-0383)the Shu Guang Project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation,China(Grant No.11SG26)the Shanghai Pujiang Program,China(Grant No.09PJ1404400)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry,National Basic Research Program of China(Grant No.2016YFA0302103)the Program of State Key Laboratory of Advanced 207 Optical Communication Systems and Networks,China(Grant No.2016GZKF0JT003)
文摘We investigate the performances of the pairwise correlations(PCs) in different quantum networks consisting of fourwave mixers(FWMs) and beamsplitters(BSs). PCs with quantum correlation in different quantum networks can be verified by calculating the degree of relative intensity squeezing for any pair of all the output fields. More interestingly, the quantum correlation recovery and enhancement are present in the FWM+BS network and the repulsion effect phenomena(signal(idler)-frequency mode cannot be quantum correlated with the other two idler(signal)-frequency modes simultaneously)between the PCs with quantum correlation are predicted in the FWM + FWM and FWM + FWM + FWM networks. Our results presented here pave the way for the manipulation of the quantum correlation in quantum networks.
基金Project supported by the Chinese Academy of Sciences(Grant Nos.GJJSTD20180003 and QYZDJ-SSW-SLH043)the National Key Basic Research and Development Program of China(Grant Nos.2017YFA0304003 and 2018YFA0404701)+1 种基金the National Natural Science Foundation of China(Grant Nos.11603081,11673073,U1831202,and 11873099)PICS projects between the CAS and the CNRS.
文摘We report on the investigation of optimal bias region of a wide-band superconducting hot electron bolometer(HEB)mixer in terms of noise temperature performance for multi-pixel heterodyne receiver application in the 5-meter Dome A Terahertz Explorer(DATE5)telescope.By evaluating the double sideband(DSB)receiver noise temperature(Trec)across a wide frequency range from 0.2 THz to 1.34 THz and with a large number of bias points,a broad optimal bias region has been observed,illustrating a good bias applicability for multipixel application since the performance of the HEB mixer is uniquely determined by each bias point.The noise temperature of the HEB mixer has been analyzed by calibrating the noise contribution of all RF components,whose transmissions have been measured by a time-domain spectroscopy.The corrected noise temperature distribution shows a frequency independence relation.The dependence of the optimal bias region on the bath temperature of the HEB mixer has also been investigated,the bath temperature has limited effect on the lowest receiver noise temperature until 7 K,however the optimal bias region deteriorates obviously with increasing bath temperature.
基金National Natural Science Foundation of China(No.61871072).
文摘This paper presents a 220-GHz-band 7-m wireless link with a 45-Gbps transmission data rate by using 16 quadrature amplitude modulation(16-QAM).Super-heterodyne transceiver modules are developed for transmission and reception of the modulated signals,which consist of a Schottky barrier diodes(SBD)based sub-harmonic mixer(SHM),an InP HEMT low noise amplifier(LNA),a waveguide band-pass filter(BPF),and a 108-GHz local oscillator(LO)multiplier chain.The transmitter features a peak transmit power of 1.41 dBm,and the IF frequency varies from 5 GHz to 20 GHz.Besides,the receiver features a conversion gain of 9.3 dB in average and a noise temperature of 3052.8 K.The measured results indicate that the transceiver modules enable data transmission of a 45-Gbps 16-QAM signal with Signal-Noise-Ratio(SNR)from 11.59 dB to 15.36 dB in a 7-m line-of-sight channel.
文摘We propose a convenient way of evaluating the mixing performance of static mixers used for round pipe by conducting flow visualization experiments under the turbulent region and using water as the main stream. A fluorescent pigment, glycerin, two carboxymethyl cellulose solutions, and rapeseed oil were each injected upstream of the mixer. Three static mixer conditions were tested: 1) no static mixer;2) a Kenics-type static mixer;and 3) a multi-stacked elements (MSE) static mixer. The mixing trend downstream of the mixer in each condition and with each injection fluid was monitored using a laser and high-speed video camera system to obtain cross-sectional images. We propose suitable indexes based on the images obtained for quantitative evaluations of the mixing characteristics of static mixers.
文摘Mixers in the communication system provide the possibility of encoding and decoding radio-frequency EM waves with signals through the help of local oscillators. A mixer with capability of high conversion gain, good isolation, and good linearity is comparably appreciated. Extensively wide ranges of frequencies, from 5.0 to 18.0 GHz, are to be examined addressing the promising functions of mixers in this study. A TSMC 0.18 μm CMOS model implanted in Agilent ADS is used for the circuit designs. Generated from Gilbert Cell Mixer, the modified circuits take advantage of extra active and passive devices to optimize the conversion gains. Characteristics of high conversion gain over 20 dB or even higher (as high as 29.842 dB at -40 mW RF power at working frequency 6 GHz) and low noise figures (NF) are shown.
基金supported by the National Natural Science Foundation of China(22078278)Hunan Innovative Talent Project(2022RC1111)+2 种基金Hunan Provincial Education Bureau Foundation(22A0131)Hunan Province Higher Education Key Laboratory of Green Catalysis and Industrial Reaction Process IntensificationFurong Plan Provincial Enterprise Technology Innovation and Entrepreneurship Team.
文摘Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.
基金Project supported in part by the National Key Research and Development Program of China(Grant Nos.2023YFA1608201 and 2023YFF0722301)the National Natural Science Foundation of China(Grant Nos.11925304,12020101002,12333013,12273119,and 12103093)supported by grant from the Russian Science Foundation(Grant No.23-7900019)。
文摘The terahertz band,a unique segment of the electromagnetic spectrum,is crucial for observing the cold,dark universe and plays a pivotal role in cutting-edge scientific research,including the study of cosmic environments that support life and imaging black holes.High-sensitivity superconductor–insulator–superconductor(SIS)mixers are essential detectors for terahertz astronomical telescopes and interferometric arrays.Compared to the commonly used classical Nb/AlO_(x)/Nb superconducting tunnel junction,the Nb/AlN/NbN hybrid superconducting tunnel junction has a higher energy gap voltage and can achieve a higher critical current density.This makes it particularly promising for the development of ultra-wideband,high-sensitivity coherent detectors or mixers in various scientific research fields.In this paper,we present a superconducting SIS mixer based on Nb/AlN/NbN parallel-connected twin junctions(PCTJ),which has a bandwidth extending up to490 GHz–720 GHz.The best achieved double-sideband(DSB)noise temperature(sensitivity)is below three times the quantum noise level.