The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face se...The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior（steady-state performance and transient performance） of face seals. A numerical finite element method（FEM） model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.展开更多
A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the top...A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.展开更多
This paper elaborates on the magnetic forces between current carrying planar spiral coils. Direct and concentric rings methods are employed in order to calculate the magnetic force between these coils. The results obt...This paper elaborates on the magnetic forces between current carrying planar spiral coils. Direct and concentric rings methods are employed in order to calculate the magnetic force between these coils. The results obtained by two calculation methods show the efficiency of the replaced rings method in both simplicity and calculation time. Simula-tions using the Finite Element Method (FEM) are carried out to analyze the distribution of the magnetic flux density around the coils. Also, coils with precise size have been constructed and tested. The experimental results as well as the results obtained by FEM are used to validate the accuracy of the calculations.展开更多
Gravitation is one of the central forces playing an important role in formation of natural systems like galaxies and planets. Gravitational forces between particles of a gaseous cloud transform the cloud into spherica...Gravitation is one of the central forces playing an important role in formation of natural systems like galaxies and planets. Gravitational forces between particles of a gaseous cloud transform the cloud into spherical shells and disks of higher density during gravitational contraction. The density can reach that of a solid body. The theoretical model was tested to model the formation of a spiral galaxy and Saturn. The formations of a spiral galaxy and Saturn and its disk are simulated using a novel N-body self-gravitational model. It is demonstrated that the formation of the spirals of the galaxy and disk of the planet is the result of gravitational contraction of a slowly rotated particle cloud that has a shape of slightly deformed sphere for Saturn and ellipsoid for the spiral galaxy. For Saturn, the sphere was flattened by a coefficient of 0.8 along the axis of rotation. During the gravitational contraction, the major part of the cloud transformed into a planet and a minor part transformed into a disk. The thin structured disk is a result of the electromagnetic interaction in which the magnetic forces acting on charged particles of the cloud originate from the core of the planet.展开更多
提出新的无向双环网络G(N;±1,±s)的直径求解法——分步法,并得到一种新的直观图——螺旋环,研究了螺旋环的性质,给出无向双环网络的直径d(N;±1,±s)的显式公式,给出N,s都固定的直径算法。给出N固定,2≤s≤N?1这样一...提出新的无向双环网络G(N;±1,±s)的直径求解法——分步法,并得到一种新的直观图——螺旋环,研究了螺旋环的性质,给出无向双环网络的直径d(N;±1,±s)的显式公式,给出N,s都固定的直径算法。给出N固定,2≤s≤N?1这样一族无向双环网络的直径算法。利用VB6.0和SQL Server 2000来仿真2≤s≤N?1,找出了该族无向双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;±1,±s)紧优或几乎紧优。验证了Boesch和Wang等提出的无向双环网络G(N;±1,±S)的直径下界,给出了一个新的直径上界公式。展开更多
基金Supported by National Key Basic Research Program of China(973Program,Grant No.2012CB026003)National Science and Technology Major Project of China(Grant No.ZX06901)
文摘The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior（steady-state performance and transient performance） of face seals. A numerical finite element method（FEM） model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.
基金Supported by the National Natural Science Foundation of China under Grant No 10675099, the Hong Kong Research Council （RGC）, and the Hong Kong Baptist University Faculty Research Fund （FRG）.
文摘A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.
文摘This paper elaborates on the magnetic forces between current carrying planar spiral coils. Direct and concentric rings methods are employed in order to calculate the magnetic force between these coils. The results obtained by two calculation methods show the efficiency of the replaced rings method in both simplicity and calculation time. Simula-tions using the Finite Element Method (FEM) are carried out to analyze the distribution of the magnetic flux density around the coils. Also, coils with precise size have been constructed and tested. The experimental results as well as the results obtained by FEM are used to validate the accuracy of the calculations.
文摘Gravitation is one of the central forces playing an important role in formation of natural systems like galaxies and planets. Gravitational forces between particles of a gaseous cloud transform the cloud into spherical shells and disks of higher density during gravitational contraction. The density can reach that of a solid body. The theoretical model was tested to model the formation of a spiral galaxy and Saturn. The formations of a spiral galaxy and Saturn and its disk are simulated using a novel N-body self-gravitational model. It is demonstrated that the formation of the spirals of the galaxy and disk of the planet is the result of gravitational contraction of a slowly rotated particle cloud that has a shape of slightly deformed sphere for Saturn and ellipsoid for the spiral galaxy. For Saturn, the sphere was flattened by a coefficient of 0.8 along the axis of rotation. During the gravitational contraction, the major part of the cloud transformed into a planet and a minor part transformed into a disk. The thin structured disk is a result of the electromagnetic interaction in which the magnetic forces acting on charged particles of the cloud originate from the core of the planet.
文摘提出新的无向双环网络G(N;±1,±s)的直径求解法——分步法,并得到一种新的直观图——螺旋环,研究了螺旋环的性质,给出无向双环网络的直径d(N;±1,±s)的显式公式,给出N,s都固定的直径算法。给出N固定,2≤s≤N?1这样一族无向双环网络的直径算法。利用VB6.0和SQL Server 2000来仿真2≤s≤N?1,找出了该族无向双环网络直径的分布特点:具有最大值、最小值和中间对称性;对任意N,有不少s使得G(N;±1,±s)紧优或几乎紧优。验证了Boesch和Wang等提出的无向双环网络G(N;±1,±S)的直径下界,给出了一个新的直径上界公式。
