In this study, the flows in an enclosed annular rotor-stator system with the Reynolds number ranging from 0.75×105 to 3.75×105 and an aspect ratio of 36.5 are investigated using the LES method. Few studies h...In this study, the flows in an enclosed annular rotor-stator system with the Reynolds number ranging from 0.75×105 to 3.75×105 and an aspect ratio of 36.5 are investigated using the LES method. Few studies have explored such a rotor-stator system with this aspect ratio and the flow structure on the rotor side. The mean flow structure varies from a torsional Couette type to a Batchelor type as the Reynolds number increases. The onset of the instability in the B?dewadt layer adjacent to the stator is delayed,whereas it is promoted in the Ekman layer adjacent to the rotor. Both the layers demonstrate rich spiral structures. Turbulent spirals are observed to occur at the rotor disk side that also generates TS-wave-like(Tollmien-Schlichting) structures between adjacent spiral arms. Further, the turbulence at the stator is complex and interesting. Statistically, the turbulence is highly anisotropic near both the rotating and nonrotating disks, which is depicted by the Reynolds stresses.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
This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The ...This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The periphery of the cavity is opened to the atmosphere so that the solid body rotation for infinite discs is not always observed. Emphasis was placed on develop- ment of an asymptotic approach and a step-by-step method to compute the radial distribution of the core swirl ratio and the static pressure on the stator side. The theory also includes the radial and axial velocities in the core region. The numerical simulation has been conducted with the commercial CFD code Fluent 6.1. The k- SST turbulence model is used, with the assumption of 2D-axisymmetric and steady flow. CFD validations have been performed by comparison of the numerical results with the corresponding theoretical results. Numerical and experimental results are in good agreement with analytical solutions.展开更多
In this paper a rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat disks, located coaxially and parallel to each other with ...In this paper a rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat disks, located coaxially and parallel to each other with a gap ranging from 0.1 mm to 0.2 mm between the disks. The upper disk is located on a rotating shaft while the lower disk is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the center line of rotating disk and stationary disk, respectively. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction species transport model by the CFD software ANSYS? Fluent v. 13.0. The effects of upper disk’s spinning speed and gap size are evaluated.展开更多
Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the ef...Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes.To avoid hot mainstream gas ingress,the cavity is usually purged by a stream of sealing flow.The interactions between the external crossflow,cavity flow,and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach.To cope with such a complex issue,a wall-modeled large-eddy simulation(WMLES)approach is adopted in this study.In the simulation,a 20°sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow.It is triggered by a convergent Reynoldsaveraged Navier-Stokes(RANS)result in which the shear stress transport(SST)turbulent model is used.In the WMLES simulation,the Smagoringsky sub-grid scale(SGS)model is applied.A scalar transportation equation is solved to simulate the blending and transportation process in the cavity.The overall flow field characteristics and deviation between RANS and WMLES results are discussed first.Both RANS and WMLES results show a Batchelor flow mode,while distinct deviation is also observed.Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion.The boundary layer vortex and external ingestion are then discussed in detail,highlighting the related flow instabilities.Finally,the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11272183,and 11572176)the National Key Basic Research Programme of China(Grant No.2014CB744801)supported by IHI Corporation
文摘In this study, the flows in an enclosed annular rotor-stator system with the Reynolds number ranging from 0.75×105 to 3.75×105 and an aspect ratio of 36.5 are investigated using the LES method. Few studies have explored such a rotor-stator system with this aspect ratio and the flow structure on the rotor side. The mean flow structure varies from a torsional Couette type to a Batchelor type as the Reynolds number increases. The onset of the instability in the B?dewadt layer adjacent to the stator is delayed,whereas it is promoted in the Ekman layer adjacent to the rotor. Both the layers demonstrate rich spiral structures. Turbulent spirals are observed to occur at the rotor disk side that also generates TS-wave-like(Tollmien-Schlichting) structures between adjacent spiral arms. Further, the turbulence at the stator is complex and interesting. Statistically, the turbulence is highly anisotropic near both the rotating and nonrotating disks, which is depicted by the Reynolds stresses.
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.
文摘This paper deals with an experimental, theoretical and numerical study of a turbulent flow with separated boundary layers between a rotor and a stator. The system is not subjected to any superimposed radial flow. The periphery of the cavity is opened to the atmosphere so that the solid body rotation for infinite discs is not always observed. Emphasis was placed on develop- ment of an asymptotic approach and a step-by-step method to compute the radial distribution of the core swirl ratio and the static pressure on the stator side. The theory also includes the radial and axial velocities in the core region. The numerical simulation has been conducted with the commercial CFD code Fluent 6.1. The k- SST turbulence model is used, with the assumption of 2D-axisymmetric and steady flow. CFD validations have been performed by comparison of the numerical results with the corresponding theoretical results. Numerical and experimental results are in good agreement with analytical solutions.
文摘In this paper a rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat disks, located coaxially and parallel to each other with a gap ranging from 0.1 mm to 0.2 mm between the disks. The upper disk is located on a rotating shaft while the lower disk is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the center line of rotating disk and stationary disk, respectively. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction species transport model by the CFD software ANSYS? Fluent v. 13.0. The effects of upper disk’s spinning speed and gap size are evaluated.
基金This work is supported by the National Natural Science Foundation of China(No.5212201273)the National Science and Technology Major Project of China(No.J2019-III-0003)The CFX software and computation resource supplied by Beijing Super Cloud Computing Center,China are acknowledged.
文摘Rotor-stator cavities are frequently encountered in engineering applications such as gas turbine engines.They are usually subject to an external hot mainstream crossflow which in general is highly swirled under the effect of the nozzle guide vanes.To avoid hot mainstream gas ingress,the cavity is usually purged by a stream of sealing flow.The interactions between the external crossflow,cavity flow,and sealing flow are complicated and involve all scales of turbulent unsteadiness and flow instability which are beyond the resolution of the Reynolds-average approach.To cope with such a complex issue,a wall-modeled large-eddy simulation(WMLES)approach is adopted in this study.In the simulation,a 20°sector model is used and subjected to a uniform pre-swirled external crossflow and a stream of radial sealing flow.It is triggered by a convergent Reynoldsaveraged Navier-Stokes(RANS)result in which the shear stress transport(SST)turbulent model is used.In the WMLES simulation,the Smagoringsky sub-grid scale(SGS)model is applied.A scalar transportation equation is solved to simulate the blending and transportation process in the cavity.The overall flow field characteristics and deviation between RANS and WMLES results are discussed first.Both RANS and WMLES results show a Batchelor flow mode,while distinct deviation is also observed.Deviations in the small-radius region are caused by the insufficiency of the RANS approach in capturing the small-scale vortex structures in the boundary layer while deviations in the large-radius region are caused by the insufficiency of the RANS approach in predicting the external crossflow ingestion.The boundary layer vortex and external ingestion are then discussed in detail,highlighting the related flow instabilities.Finally,the large-flow structures induced by external flow ingress are analyzed using unsteady pressure oscillation signals.
