A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and tempera...A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and temperature distribution were investigated. A thermal measurement was conducted on a rotary kiln (4.5m in diameter, 90m in length) with four-air channel coal burner to determine the boundary conditions and to verify the simulation results. The calculation result shows that the distribution of velocity near burner exit is saddle-like; recirculation zones near nozzle and wall are useful for mixture primary air with coal and high temperature fume. A little central airflow can avoid coal backing up and cool nozzle. Adjusting the ratio of internal airflow to outer airflow is an effective and major means to regulate flame and temperature distribution in sintering region. Large whirlcone angle can intensify disturbution range at flame root to accelerate ignition and mixture. Large coal size can reduce high temperature region and result in coal combusting insufficiently. Too much combustion air will lengthen flame and increase heat loss.展开更多
An embedded underground coal seam carries channel waves of low seismic velocity along a stratigraphic rock-coal-rock sequence.In a homogeneous and isotropic seam, seismic waves propagate as trapped waves within the se...An embedded underground coal seam carries channel waves of low seismic velocity along a stratigraphic rock-coal-rock sequence.In a homogeneous and isotropic seam, seismic waves propagate as trapped waves within the seam, which leads to propagation of channel waves.We describe how to set up a field test for transmission in order to acquire channel waves in a coal seam.Because channel wave signals are non-stationary in their frequencies and amplitudes, a necessary velocity spectrum and wavelet transformation analysis are applied to interpret the characteristics of channel waves.The advantage of using a wavelet transformation is that different resolutions can be obtained at different times and different frequencies.According to analysis of the seismic signals acquired in the S7 sensor hole, it was clearly shown that the characteristics of channel waves are lower frequencies and attenuation which can guide an effective wave for detecting voids, boundaries and faults in coal seams with strong roofs and floors.展开更多
In this paper, the numerical simulation on the flow field of a four-channel coal burner was investigated with Fluent software. The three-dimension model was created with UG software. The structure was meshed by using ...In this paper, the numerical simulation on the flow field of a four-channel coal burner was investigated with Fluent software. The three-dimension model was created with UG software. The structure was meshed by using Gambit software. The realizable K-ε turbulence model and simple method were adopted. The variation of the inner flow field of the burner was studied and analyzed. The results simulated to the burner by the realizable K-ε turbulence model show that the contours of theflowfield accord with the actual condition and the realizable K-ε model is proved to be feasible and the results of simulation are creditable. That will have important significance to the improvement of the structure and parameter optimization of the four-channel coal burner in the future.展开更多
To facilitate investigation of the effect of imperfect elastic dissipation on thepropagation of Rayleigh-type channel waves and use of their quality factors in investigationsof the properties of coal seams, a simple m...To facilitate investigation of the effect of imperfect elastic dissipation on thepropagation of Rayleigh-type channel waves and use of their quality factors in investigationsof the properties of coal seams, a simple method for calculating the quality factor QR isproposed in this paper. Introduction of complex velocities into the dispersion function allowscalculation of the dispersion function of Rayleigh-type channel waves in coal seams. By thecontrol variable method, we analyzed changes in QR with changes in coal seam thickness andP- and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical resultsshow that the trend of the QR curve is consistent with the group velocity curve. The minimumQR value occurs at the Airy phase frequency; the Airy phase frequency decreases as coal seamthickness increases. The value of QR increases with increasing Qs2 （quality factor for S wavein coal seam）. We can compensate for the absorption of Rayleigh-type channel waves usingthe computed QR curve. Inversion of the QR curve can also be used to predict the thicknessesand litholoeies of coal seams.展开更多
From an analysis of the status of coal mine underground wireless communication, the application of UWB wireless communication system to underground coal mine is proposed. The basic composition of an UWB communication ...From an analysis of the status of coal mine underground wireless communication, the application of UWB wireless communication system to underground coal mine is proposed. The basic composition of an UWB communication system and application in underground coal mines are introduced. The analyses show that, because of the transmission power being non-limitted in underground coal mines, the use of UWB in coal mines cannot only realize wireless access services of short distance high rate application for transmission of video monitoring signals, but also realize wireless access services of long distance low rate applications for mobile telephones in underground coal mines and parameters of working conditions monitoring, etc. It is emphasized on the simulation of a TH-PPM UWB communication system with traditional underground broadband model and ground CM1, CM3 model. It is shown that the traditional underground broadband model and ground CM1, CM3 models are not applicable to the UWB communication system in underground coal mines. It is necessary to conduct research on the propagation characteristics of UWB in coal mine tunnels, given the characteristics of the underground environment and to find the appropriate UWB model for underground coal mines.展开更多
The exact shape and size of the gasification channel during underground coal gasification(UGC) are of vital importance for the safety and stability of the upper parts of the geological formation.In practice existing g...The exact shape and size of the gasification channel during underground coal gasification(UGC) are of vital importance for the safety and stability of the upper parts of the geological formation.In practice existing geological measurements are insufficient to obtain such information because the coal seam is typically deeply buried and the geological conditions are often complex.This paper introduces a cylindrical model for the gasification channel.The rock and soil masses are assumed to be homogeneous and isotropic and the effect of seepage on the temperature field was neglected.The theory of heat conduction was used to write the equation predicting the temperature field around the gasification channel.The idea of an excess temperature was introduced to solve the equations.Applying this model to UCG in the field for an influence radius,r,of 70 m gave the model parameters,u1,2,3...,of 2.4,5.5,8.7...By adjusting the radius(2,4,or 6 m) reasonable temperatures of the gasification channel were found for 4 m.The temperature distribution in the vertical direction,and the combustion volume,were also calculated.Comparison to field measurements shows that the results obtained from the proposed model are very close to practice.展开更多
文摘A 3-D numerical simulation with CFX software on physical field of multi-air channel coal burner in rotary kiln was carried out. The effects of various operational and structural parameters on flame feature and temperature distribution were investigated. A thermal measurement was conducted on a rotary kiln (4.5m in diameter, 90m in length) with four-air channel coal burner to determine the boundary conditions and to verify the simulation results. The calculation result shows that the distribution of velocity near burner exit is saddle-like; recirculation zones near nozzle and wall are useful for mixture primary air with coal and high temperature fume. A little central airflow can avoid coal backing up and cool nozzle. Adjusting the ratio of internal airflow to outer airflow is an effective and major means to regulate flame and temperature distribution in sintering region. Large whirlcone angle can intensify disturbution range at flame root to accelerate ignition and mixture. Large coal size can reduce high temperature region and result in coal combusting insufficiently. Too much combustion air will lengthen flame and increase heat loss.
基金Project B2532532 supported by the U.S. Mine Safety and Health Administration
文摘An embedded underground coal seam carries channel waves of low seismic velocity along a stratigraphic rock-coal-rock sequence.In a homogeneous and isotropic seam, seismic waves propagate as trapped waves within the seam, which leads to propagation of channel waves.We describe how to set up a field test for transmission in order to acquire channel waves in a coal seam.Because channel wave signals are non-stationary in their frequencies and amplitudes, a necessary velocity spectrum and wavelet transformation analysis are applied to interpret the characteristics of channel waves.The advantage of using a wavelet transformation is that different resolutions can be obtained at different times and different frequencies.According to analysis of the seismic signals acquired in the S7 sensor hole, it was clearly shown that the characteristics of channel waves are lower frequencies and attenuation which can guide an effective wave for detecting voids, boundaries and faults in coal seams with strong roofs and floors.
文摘In this paper, the numerical simulation on the flow field of a four-channel coal burner was investigated with Fluent software. The three-dimension model was created with UG software. The structure was meshed by using Gambit software. The realizable K-ε turbulence model and simple method were adopted. The variation of the inner flow field of the burner was studied and analyzed. The results simulated to the burner by the realizable K-ε turbulence model show that the contours of theflowfield accord with the actual condition and the realizable K-ε model is proved to be feasible and the results of simulation are creditable. That will have important significance to the improvement of the structure and parameter optimization of the four-channel coal burner in the future.
基金This work is supported by the National Natural Science Foundation of China （No. 41140033）.
文摘To facilitate investigation of the effect of imperfect elastic dissipation on thepropagation of Rayleigh-type channel waves and use of their quality factors in investigationsof the properties of coal seams, a simple method for calculating the quality factor QR isproposed in this paper. Introduction of complex velocities into the dispersion function allowscalculation of the dispersion function of Rayleigh-type channel waves in coal seams. By thecontrol variable method, we analyzed changes in QR with changes in coal seam thickness andP- and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical resultsshow that the trend of the QR curve is consistent with the group velocity curve. The minimumQR value occurs at the Airy phase frequency; the Airy phase frequency decreases as coal seamthickness increases. The value of QR increases with increasing Qs2 （quality factor for S wavein coal seam）. We can compensate for the absorption of Rayleigh-type channel waves usingthe computed QR curve. Inversion of the QR curve can also be used to predict the thicknessesand litholoeies of coal seams.
基金Project OC4501 supported by the Scientific Research Fund of China University of Mining & Technology
文摘From an analysis of the status of coal mine underground wireless communication, the application of UWB wireless communication system to underground coal mine is proposed. The basic composition of an UWB communication system and application in underground coal mines are introduced. The analyses show that, because of the transmission power being non-limitted in underground coal mines, the use of UWB in coal mines cannot only realize wireless access services of short distance high rate application for transmission of video monitoring signals, but also realize wireless access services of long distance low rate applications for mobile telephones in underground coal mines and parameters of working conditions monitoring, etc. It is emphasized on the simulation of a TH-PPM UWB communication system with traditional underground broadband model and ground CM1, CM3 model. It is shown that the traditional underground broadband model and ground CM1, CM3 models are not applicable to the UWB communication system in underground coal mines. It is necessary to conduct research on the propagation characteristics of UWB in coal mine tunnels, given the characteristics of the underground environment and to find the appropriate UWB model for underground coal mines.
基金supported by a grant from the Major State Basic Research and Development Program of China (No. 2007CB714102)sponsored by the Fundamental Research Funds for the Central Universities (No. 2009B00714)
文摘The exact shape and size of the gasification channel during underground coal gasification(UGC) are of vital importance for the safety and stability of the upper parts of the geological formation.In practice existing geological measurements are insufficient to obtain such information because the coal seam is typically deeply buried and the geological conditions are often complex.This paper introduces a cylindrical model for the gasification channel.The rock and soil masses are assumed to be homogeneous and isotropic and the effect of seepage on the temperature field was neglected.The theory of heat conduction was used to write the equation predicting the temperature field around the gasification channel.The idea of an excess temperature was introduced to solve the equations.Applying this model to UCG in the field for an influence radius,r,of 70 m gave the model parameters,u1,2,3...,of 2.4,5.5,8.7...By adjusting the radius(2,4,or 6 m) reasonable temperatures of the gasification channel were found for 4 m.The temperature distribution in the vertical direction,and the combustion volume,were also calculated.Comparison to field measurements shows that the results obtained from the proposed model are very close to practice.
