Pores and fractures and their connectivity play a significant role in coalbed methane production.To investigate the growth characteristics and connectivity of pores and fractures in coal parallel and perpendicular to ...Pores and fractures and their connectivity play a significant role in coalbed methane production.To investigate the growth characteristics and connectivity of pores and fractures in coal parallel and perpendicular to the bedding plane,the pores and fractures of high-rank coal samples collected from the southern Qinshui Basin were measured by low-field nuclear magnetic resonance,X-ray-computed tomography and field emission scanning electron microscopy.Then,the determinants of their connectivity were further discussed.The results show that the high-rank coal samples have similar pore size distributions both parallel and perpendicular to the bedding plane.They primarily contain mesopores(2-50 nm in width),followed by macrospores(> 50 nm in width).The research indicated that the high-rank coal connectivity parallel to the bedding plane is significantly better than that perpendicular to the bedding plane.The connectivity of high-rank coal is mainly determined by throats,and the orientation of the pores and fractures.The two connectivity modes in high-rank coal are "pore connectivity," in which the throats are mainly pores with a low coordination number,and "microfissure connectivity",in which the throats are mainly microfissures with a high coordination number.展开更多
Low-expansion superalloys are susceptible to weld solidification cracks and heat,affected zone （HAZ）microflssures. To predict solidification cracking, QBasic procedures were developed and solidification reaction se...Low-expansion superalloys are susceptible to weld solidification cracks and heat,affected zone （HAZ）microflssures. To predict solidification cracking, QBasic procedures were developed and solidification reaction sequence, type, and amount of eutectic product were caiculated As manifested, primary solidification is followed by L→（Y＋ NbC） and L → （Y＋ Laves） eutectic reaction sequentially for G H903 and GH907; hence, the terminal eutectic constitue Y/Laves, While for GH909, intsare made up of Y/NbC and Y/only reaction L → （Y ＋ Laves） occurs and more Y/Laves eutectic forms. Therefore, GH909is more sensitive to solidification cracking. To predict HAZ liquation, cracking Visual FORTRAN procedures were developed, and constitutional liquation of NbC was simulated. As shown, solid dissolution of NbC prior to liquation decreases, and initial liquid film increases with the rate of thermal cycle. Higher rate of thermal cycle promotes the melting of the matrix adjacent to the liquid film and postpones the solidification of the at the eutectic n size and peak rifled indirectly by hot ductility tests.展开更多
基金supported by the Fundamental Research Funds for the Central Universities (No.2017XKQY017)。
文摘Pores and fractures and their connectivity play a significant role in coalbed methane production.To investigate the growth characteristics and connectivity of pores and fractures in coal parallel and perpendicular to the bedding plane,the pores and fractures of high-rank coal samples collected from the southern Qinshui Basin were measured by low-field nuclear magnetic resonance,X-ray-computed tomography and field emission scanning electron microscopy.Then,the determinants of their connectivity were further discussed.The results show that the high-rank coal samples have similar pore size distributions both parallel and perpendicular to the bedding plane.They primarily contain mesopores(2-50 nm in width),followed by macrospores(> 50 nm in width).The research indicated that the high-rank coal connectivity parallel to the bedding plane is significantly better than that perpendicular to the bedding plane.The connectivity of high-rank coal is mainly determined by throats,and the orientation of the pores and fractures.The two connectivity modes in high-rank coal are "pore connectivity," in which the throats are mainly pores with a low coordination number,and "microfissure connectivity",in which the throats are mainly microfissures with a high coordination number.
文摘Low-expansion superalloys are susceptible to weld solidification cracks and heat,affected zone （HAZ）microflssures. To predict solidification cracking, QBasic procedures were developed and solidification reaction sequence, type, and amount of eutectic product were caiculated As manifested, primary solidification is followed by L→（Y＋ NbC） and L → （Y＋ Laves） eutectic reaction sequentially for G H903 and GH907; hence, the terminal eutectic constitue Y/Laves, While for GH909, intsare made up of Y/NbC and Y/only reaction L → （Y ＋ Laves） occurs and more Y/Laves eutectic forms. Therefore, GH909is more sensitive to solidification cracking. To predict HAZ liquation, cracking Visual FORTRAN procedures were developed, and constitutional liquation of NbC was simulated. As shown, solid dissolution of NbC prior to liquation decreases, and initial liquid film increases with the rate of thermal cycle. Higher rate of thermal cycle promotes the melting of the matrix adjacent to the liquid film and postpones the solidification of the at the eutectic n size and peak rifled indirectly by hot ductility tests.
