Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hi...Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.展开更多
Detailed parametric study of three-dimensional gas-particle multiphase flow characteristics in U-beam tube bundle inertial separators was conducted by numerical simulation. The carrier phase was treated in the Euleria...Detailed parametric study of three-dimensional gas-particle multiphase flow characteristics in U-beam tube bundle inertial separators was conducted by numerical simulation. The carrier phase was treated in the Eulerian frame, the particles were tracked in the Lagrangian frame, and particle-wall collision was considered. Simulation carried out at different inflow rate and mass loading ratios revealed the pressure losses in the separators, velocity field of the gas phase, and the trajectories of particles. The study results revealed the multiphase flow-dynamic features of the separators, and the relationship between separator pressure losses and different inlet velocity. The numerical simulation can provide basis both for optimal design of impacting-inertial separator used in circulating fluidized bed boiler; and for study of gas-particle multiphase circumfluence flow.展开更多
A closed orientable Haken 3-manifold containing a non separating incompressible closed surface has two canonical Heegaard splittings, which are called self-amalgamation and bilateral self-amalgamation.Heegaard distanc...A closed orientable Haken 3-manifold containing a non separating incompressible closed surface has two canonical Heegaard splittings, which are called self-amalgamation and bilateral self-amalgamation.Heegaard distance introduced by Hempel is a useful index in studying Heegaard splitting. This paper studies the stabilization problem for the bilateral self-amalgamation, and proves that if the distance of bilateral selfamalgamation of a Heegaard splitting is at least 9, then it is unstabilized, weakly reducible and irreducible.展开更多
文摘Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.
文摘Detailed parametric study of three-dimensional gas-particle multiphase flow characteristics in U-beam tube bundle inertial separators was conducted by numerical simulation. The carrier phase was treated in the Eulerian frame, the particles were tracked in the Lagrangian frame, and particle-wall collision was considered. Simulation carried out at different inflow rate and mass loading ratios revealed the pressure losses in the separators, velocity field of the gas phase, and the trajectories of particles. The study results revealed the multiphase flow-dynamic features of the separators, and the relationship between separator pressure losses and different inlet velocity. The numerical simulation can provide basis both for optimal design of impacting-inertial separator used in circulating fluidized bed boiler; and for study of gas-particle multiphase circumfluence flow.
基金supported by National Natural Science Foundation of China(Grant Nos.11271058 and 11371076)the Fundamental Research Funds for the Central Universities(Grant No.DUT14ZD208)
文摘A closed orientable Haken 3-manifold containing a non separating incompressible closed surface has two canonical Heegaard splittings, which are called self-amalgamation and bilateral self-amalgamation.Heegaard distance introduced by Hempel is a useful index in studying Heegaard splitting. This paper studies the stabilization problem for the bilateral self-amalgamation, and proves that if the distance of bilateral selfamalgamation of a Heegaard splitting is at least 9, then it is unstabilized, weakly reducible and irreducible.
