Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load tran...Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load transport rate by adopting the sedimentation pit method and resolving such key problems as weighing and desilting, which can achieve long-time, all-weather and real-time telemeasurement of the bed load transport rate of plain rivers, estuaries and coasts. Both laboratory and field tests show that this monitor is reasonable in design, stable in properties and convenient in measurement, and it can be used to monitor the bed load transport rate in practical projects.展开更多
Due to the nature of coal bed,slack coal production is inevitable in gas recovery sby water drainage.When coalbed methane(CBM)wells are reentered after low energy exploitation and shut-in,the negative effect of slack ...Due to the nature of coal bed,slack coal production is inevitable in gas recovery sby water drainage.When coalbed methane(CBM)wells are reentered after low energy exploitation and shut-in,the negative effect of slack coal production on productivity of CBM is irreversible.In this paper,the CBM occurrence characteristics and multi-lateral horizontal well trajectory in the Qinshui Basin,Shanxi Province,were analyzed.In the multi-lateral horizontal wells,the expected gas production rate could not be reached and the production rate after shut-in maintenance could not restore to the level before shut-in.The reason for these issues is that migration pathways in the reservoirs are blocked by slack coal deposits,while formation water and slack coal deposit accumulated at the troughs of horizontal sections enlarge the resistance for gas to flow into the bottom hole.Furthermore,three key technologies to deal with slack coal blockage were proposed.Firstly,CBM horizontal well trajectory should follow the principle of keeping the wellbores smooth and updip instead of being“wavy”,on the premise of guaranteeing CBM drilling rate.Secondly,the cavities of production wells,as an important part of multi-lateral horizontal wells,are capable of settling sand,and can be used for gaseliquidesolid separation.And thirdly,a tree-like horizontal well with its main hole set on stable seam top or floor,provides a stable well flushing passage for coal powder.This research provides a useful attempt in solving the problem of slack coal production in gas recovery by water drainage.展开更多
A fluid dynamic model of a bubbling fluidized-bed coal gasifier is presented considering two-phase theory of fluidization. The effects of the gasifier temperature and bed particle size on the hydrodynamic char- acteri...A fluid dynamic model of a bubbling fluidized-bed coal gasifier is presented considering two-phase theory of fluidization. The effects of the gasifier temperature and bed particle size on the hydrodynamic char- acteristics of both the bubble and emulsion phases of the gasifier bed are studied. The bubble diameter, bubble velocity, and bubble area fraction are evaluated for the bubble phase, whereas the gas velocity and porosity are studied for the emulsion phase, along the height of the bed. Finally, the rate of inter-phase gas exchange from the emulsion phase to bubble phase is calculated under different operating conditions.展开更多
In the catastrophe theory of nonlinear science, the intensity of water flow Θ and the coefficient of non uniform sediment m are regarded as two bound variables, and the intensity of bed load transport Φ as th...In the catastrophe theory of nonlinear science, the intensity of water flow Θ and the coefficient of non uniform sediment m are regarded as two bound variables, and the intensity of bed load transport Φ as the state variable in the motion of non uniform sediment in cusp catastrophe model. Based on the standard equation of the cusp catastrophe theory, the relation equation between the intensity of bed load transport Φ and the intensity of water flow Θ has been derived by used coordinate transform and topology transform. The equation of bed load transport rate was built on the cusp catastrophe theory of nonlinear science. The others are applied to verify this equation, that the results calculated by the cusp catastrophe equation agree well with the other equations. This indicates that the cusp catastrophe equation is reasonable, and the results fully reflect the characteristics of threshold motion and transport of non uniform sediment. The purpose of this paper is to explore the incipient motion and transport laws of non uniform sediment from the viewpoint of nonlinear science.展开更多
In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents...In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents a study investigating gas-solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measure- ments showed good agreement as to the non-uniform distribution of the gas-solid flow, which occurred mainly across the three cyclones on one side： the middle cyclones on both sides had higher particle veloc- ities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.展开更多
To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer （Eso）, solids circulation rate （Gs） and gas bypassing fraction （from down-comer to riser ...To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer （Eso）, solids circulation rate （Gs） and gas bypassing fraction （from down-comer to riser y^R, and from riser to down-comer yRD） were experimentally studied. The effects of gas velocities in the riser and in the down-comer （UR and UD）, orifice diameter in the draft tube （dor）, and draft tube height （HR） were investigated. Experimental results showed that increase of gas velocities led to increase in Gs and yDR, and slight decrease in yeD. Larger orifice diameter on the draft tube led to higher 8sD, Gs and yDR, but had insignificant influence on YRD. with increasing draft tube height, both Gs and YDR first increased and then decreased, while yRD first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values.展开更多
基金supported by the special program to enhance the navigation capacity of the Golden Waterway funded by the Ministry of Transport of the People’s Republic of China"Research on Key Techniques to Monitor and Simulate the River Flow and Sediment Transport"(Grant No.2011-328-746-40)
文摘Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load transport rate by adopting the sedimentation pit method and resolving such key problems as weighing and desilting, which can achieve long-time, all-weather and real-time telemeasurement of the bed load transport rate of plain rivers, estuaries and coasts. Both laboratory and field tests show that this monitor is reasonable in design, stable in properties and convenient in measurement, and it can be used to monitor the bed load transport rate in practical projects.
文摘Due to the nature of coal bed,slack coal production is inevitable in gas recovery sby water drainage.When coalbed methane(CBM)wells are reentered after low energy exploitation and shut-in,the negative effect of slack coal production on productivity of CBM is irreversible.In this paper,the CBM occurrence characteristics and multi-lateral horizontal well trajectory in the Qinshui Basin,Shanxi Province,were analyzed.In the multi-lateral horizontal wells,the expected gas production rate could not be reached and the production rate after shut-in maintenance could not restore to the level before shut-in.The reason for these issues is that migration pathways in the reservoirs are blocked by slack coal deposits,while formation water and slack coal deposit accumulated at the troughs of horizontal sections enlarge the resistance for gas to flow into the bottom hole.Furthermore,three key technologies to deal with slack coal blockage were proposed.Firstly,CBM horizontal well trajectory should follow the principle of keeping the wellbores smooth and updip instead of being“wavy”,on the premise of guaranteeing CBM drilling rate.Secondly,the cavities of production wells,as an important part of multi-lateral horizontal wells,are capable of settling sand,and can be used for gaseliquidesolid separation.And thirdly,a tree-like horizontal well with its main hole set on stable seam top or floor,provides a stable well flushing passage for coal powder.This research provides a useful attempt in solving the problem of slack coal production in gas recovery by water drainage.
文摘A fluid dynamic model of a bubbling fluidized-bed coal gasifier is presented considering two-phase theory of fluidization. The effects of the gasifier temperature and bed particle size on the hydrodynamic char- acteristics of both the bubble and emulsion phases of the gasifier bed are studied. The bubble diameter, bubble velocity, and bubble area fraction are evaluated for the bubble phase, whereas the gas velocity and porosity are studied for the emulsion phase, along the height of the bed. Finally, the rate of inter-phase gas exchange from the emulsion phase to bubble phase is calculated under different operating conditions.
基金theNinethFiveyearsplanProjectoftheChangjiangGorgesSedimentProblem (No :95 5 4 )andthejointprojectofNationalNaturalScienceFoundationofChinaandtheMinistryofWaterConservancyofChina (No :5 9890 2 0 0 )
文摘In the catastrophe theory of nonlinear science, the intensity of water flow Θ and the coefficient of non uniform sediment m are regarded as two bound variables, and the intensity of bed load transport Φ as the state variable in the motion of non uniform sediment in cusp catastrophe model. Based on the standard equation of the cusp catastrophe theory, the relation equation between the intensity of bed load transport Φ and the intensity of water flow Θ has been derived by used coordinate transform and topology transform. The equation of bed load transport rate was built on the cusp catastrophe theory of nonlinear science. The others are applied to verify this equation, that the results calculated by the cusp catastrophe equation agree well with the other equations. This indicates that the cusp catastrophe equation is reasonable, and the results fully reflect the characteristics of threshold motion and transport of non uniform sediment. The purpose of this paper is to explore the incipient motion and transport laws of non uniform sediment from the viewpoint of nonlinear science.
基金financial support of National Key Technologies R & D Program of China (no. 2006BAA03B01-09)International Cooperation Project of MOST (2011FR60190)
文摘In large-scale circulating fluidized bed （CFB） boilers, it is common to use multiple cyclones in parallel for the capture of solids, assuming that gas-solid flow to be the same in the cyclones. This article presents a study investigating gas-solid flow through six parallel cyclones in a CFB cold test rig. The six cyclones were located asymmetrically on the left and right walls of the riser. Solid volume fraction and particle velocity profiles at the riser outlets and in the horizontal ducts were measured using a fiber optical probe. Cyclone pressure drop and solid circulating rate were measured for each individual cyclone. Measure- ments showed good agreement as to the non-uniform distribution of the gas-solid flow, which occurred mainly across the three cyclones on one side： the middle cyclones on both sides had higher particle veloc- ities. Conversely, the solid volume fractions, solid fluxes and solid circulating rates of the middle cyclones were lower than those of the other four cyclones. The apparent reason for the flow non-uniformity among the cyclones is the significant flow non-uniformity at the riser outlets. Under typical operating conditions, the solid volume fractions at the riser outlets had a deviation of up to 26% whereas the solid circulating rates at the stand pipes, 7%. These results are consistent with most other studies in the literature.
基金the financial support by the Beijing New Star Project on Science&Technology of China under grant no.2009B35
文摘To better understand the hydrodynamic behavior of an internally circulating fluidized bed, solids holdup in the down-comer （Eso）, solids circulation rate （Gs） and gas bypassing fraction （from down-comer to riser y^R, and from riser to down-comer yRD） were experimentally studied. The effects of gas velocities in the riser and in the down-comer （UR and UD）, orifice diameter in the draft tube （dor）, and draft tube height （HR） were investigated. Experimental results showed that increase of gas velocities led to increase in Gs and yDR, and slight decrease in yeD. Larger orifice diameter on the draft tube led to higher 8sD, Gs and yDR, but had insignificant influence on YRD. with increasing draft tube height, both Gs and YDR first increased and then decreased, while yRD first decreased and then increased. Proposed correlations for predicting the hydrodynamic parameters agreed reasonably well with experimental values.
