Papers by Keyword: Gas-Solid Two Phase Flow

Abstract: In order to set solid particle phase distributed uniformly in the whole detection space， the McClements model and Bouguer -Lambert -Beer law model were applied to formulate the ultrasonic attenuation properties of gas-solid flow for pneumatic conveying fly ash. The theoretical relation between the ultrasonic attenuation coefficients and the flow parameters of gas/ solids two-phase flow was established. By numerical simulations, the alteration laws of the ultrasonic attenuation coefficients with particle volume fraction， ultrasonic frequency and particle size were analyzed. The results show that the higher the ultrasonic frequency was, the greater the attenuation coefficients were. The ultrasonic attenuation coefficients linearly increased with the increasing of the solid particles volume fraction. If some fixed frequency was chosen， the slopes of attenuation -volume fractions curves can be confirmed by just testing ultrasonic attenuation coefficients under two volume fractions. So that testing of particle volume fraction corresponding to arbitrarily ultrasonic attenuation coefficients can be achieved. If the fly ash particle sizes were in the domain of 10 -200 μm with the same volume fraction， the ultrasonic attenuation coefficients monotonically decreased with the increasing of the particle size. But if the fly ash particle size was higher than 200 μm， the ultrasonic attenuation coefficients were no longer sensitive to the solids particle size.

Abstract: In order to measure average velocity of Gas-Solid Two Phase Flow in pipelines real time and accurate, to develop the gas-solid two-phase flow average velocity meter based on direct measurement method and the secondary system. The paper introduces the working principle of the system and analyzes the factors that affect the accurate measurement. To further study the performance and continuous improve its structural design, an aerodynamic testing system was established. The device performance tests were carried out. In addition, the cold and hot industrials test were carried out in the industrial field.Practical application and test results showed that the device performance is well to achieve the industrial pipeline gas-solid two-phase flow average velocity long-term, stable and accurate measurement, and measurement error <2%.It has many features: simple structure, reliability, small flow resistance, easy installation, low maintenance costs, long life, a short straight pipe required. It can measure the gas-solid two-phase flow average velocity with high or low concentrations, and suitable for round, rectangular cross-section pipe installation. The measuring device has been used in dozens of power plant boiler, and a national invention patent and significant economic and social benefits to be achieved.

Abstract: Gas-solid two-phase flow of the quick-contact cyclone reactor used in FCC was simulated with the multi fluid Eulerian model, especially the velocity field and volume fraction of solid in the mixing chamber was researched. The results show that flow pattern and catalyst particles concentration are non-uniform in the direction of axial, radial and tangential. The tangential gas admission increases turbulent intensity, it has a great benefit on spreading the catalyst particles uniformly, enhancing gas-solid contact effect. This work could offer a base for the structure optimization of the quick-contact reactor.

Abstract: Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.

Abstract: Air drilling technology has been widely used in the oil and gas exploration, coal, geothermal, geological exploration, nuclear industry and other fields due to its high drilling rate and low cost. However, the design of the pneumatic conveying system for the mineral detritus is still largely based on empiricism. The paper was set in the background of gas drilling, mainly studied the gas-solids two-phase flow characteristics in 90 degree bent annular pipe and backward-facing step of an annular pipe, which are very important parts of air drilling. They refer to the bent part and backward-facing step of an annular channel formed by the drill pipe and the borehole wall. A detailed numerical simulation and experimental studies were carried out for the flow structure and pressure losses of gas-solid two-phase in the annular pipe of gas drilling. Since a unified theory has not been developed for the two-phase flow in annular pipe, a lot of experimental work should be conducted. In the experimental research, the paper independently designed and built an annular pipe pneumatic conveying system with 90 degree bend and backward-facing step, including designing material screw feeder, material receiving hopper, pipeline, control system, data acquisition system, and etc. As known, many parameters, such as gas velocity, diameter and density of the particle, and solids loading ratio, can influence the conveying process. How these primordial influence factors act on the pressure losses of two-phase flow in annular pipe was analyzed in this paper. In the numerical simulation research, turbulent two-phase flow calculations were performed with a commercial CFD computer code referred to as FLUENT to study the gas-solid two phase flow in the sections of backward-facing step and 90 degree bent pipe respectively by using Euler-Lagrange method. The RNG κ-ε model and stochastic tracking were involved in the calculation of turbulence dispersion of two phases. The discrete phase model was performed for the solid phase. In the end, the numerical study 3-D results were translated to 1-D results using the standard averaging transformation to compare with experimental results. Predicted results obtained for pressure drop and velocity variations in full developed flows in the cases examined are in good qualitative agreement and are not in quantitative agreement with experimental data. The deviations between the simulations and experimental data lie in the range of 20%-30%. These results suggest commercial CFD codes such as FLUENT can be used productively for investigations into gas-solid two-phase flow phenomena and as an aid in pneumatic conveying design. The studies of the two-phase flow characteristics in the paper will contribute to reliable determination of the optimal condition of pneumatic conveying in gas drilling.

Abstract: The paper takes gas/solid two-phase flow cross-correlation measurement system as the research object, adopts the method of computer simulation to research the measuring mechanism of cross-correlation velocity. By using Monte-Carlo method, the gas/solid two-phase flow model is established; and it is used to study the multiple factors affecting the system measurement performance such as sensor geometry, the distance of two sensors along the pipeline axis, the particle size and velocity, solidification flow pattern, non-solidification flow pattern, etc.

Abstract: Gas-sold two-phase flow is a typical and complex flow form in the natural world and the industrial process. The accurate measurement of the parameters is the key problem for improving the industry control quality and promoting enterprise economic benefit. Three-dimensional finite element simulation of spiral electrodes capacitance sensor was put up by ANSYS in this paper. The results from simulation show that spiral electrode capacitance sensor has an obvious advantage. The sensor has uniform sensing filled, and the capacitance value has nothing to do with flow pattern which is only related to solid concentration change. There is good linear correlation between capacitance value and solid concentration. Relationship graph between capacitance value and solid concentration was obtained by calculated. In addition, with the FEM the qualitative analyses to the effect of each structural parameter of the capacitance transducer on its capability were made. These can provide bases and supports for optimum design of this kind of sensors. Comparing with ECT, it is a simply and easy-implemented method of concentration measurement using spiral electrode capacitance sensor.

Abstract: In order to obtain flow rule and separation mechanism of garbage mixture particle in pneumatic separator, under the conditions of certain parameters and boundary, gas-solid two-phase flow mathematic model of garbage mixture particle was set up, FLUENT software was used to simulation and analyze the flow field of improved pneumatic separator, the separate track of particle in improved pneumatic separator was gained and performance of improved pneumatic separator was forecasted. Numerical simulation results show that the improved pneumatic separator has stable variation of pressure and velocity field. There not exist internal turbulence and back-mixing phenomenon and three particles with different qualities can be separated effectively. The numerical methods can be further optimized pneumatic separator and important theoretical foundation and technology method are provided for improving the structure and performance of pneumatic separator.

Abstract: The implementation of the kinetic theory for granular flows added strength to the two-phase flow model in the mini-riser. This model uses simulating and calculating commercial software of Fluent to simulate the mini-riser with 0.012m ID and 3m height. Euler-Euler two fluid model was adopted in two dimensional numerical simulation, according to kinetic theory，the solid stress was calculated based on granular temperature and granular viscosity obtained through simulation which could be used to describe the collision between particles. Simulation results, such as solid phase fraction and solid phase velocity, under different operational conditions basically agree well with the experimental measurement.

Abstract: This paper proposed the design and experimental evaluation of a radiometric instrumentation system which was developed for measuring the volume concentration and phase distribution of pulverized coal in a pneumatic conveying pipeline.The system employed point γ-ray source with 180° plane angle of emergence source collimator, γ-ray detector multi-element independent each other annular arrayed out of the sensor conduct wall,every detector element was standardized singly,in order accommodate the inhomogeneity of the pulverized coal distribution in the pipeline.the instrument system would be able to determine the volume concentrition independently of the flow pattern while obtain the distribution information of pulverized coal in the conveying pipeline cross section. The static experment improved that the solution was correct in principle.