Methanogen consortium metabolism characteristic analysis of Illinois basin by real time monitor method

Microbially Enhance Coalbed Methane technology is used to improve methane content in coalbeds. The methanogen consortium metabolism process is the basic avenue for MECoM to yield methane with some organic compounds in coal. Detailed information about the metabolism process is needed in studying the microbial consortium mechanism. Traditional gas analysis is limited by gas source and test complexity. The real time monitor with Infrared gas sensor breaks the gas analysis limitation. It shows much more detailed information than the traditional analysis method including information about microbial growth factor changes, reaction speeds for environmental changes, the detailed relationship between CH4 and CO2, methane yield and the consumption factor by real time. With these factors, MECoM can be much better evaluated and controlled. Experiments show that inhibitory and incentive effects will influence the whole organic material conversion to methane period. Not until a microbial community achieves a balanced condition, can methane generation reach a stable condition

Gateroad protection mechanism and surrounding rock control for gob-side entry with slender pillar in deep and inclined extra-thick coal seams

The depth of coal mining in the central and eastern China is increasing, the ground pressure is high, the roadway deformation and burst risk is great. Gob-side entry with slender gate pillar (GESGP) is constantly adopted to improve surrounding rock environment. In order to grasp ground pressure behavior of the gob-side entry and develop targeted surrounding rock control measures, field observation and numerical simulation have been carried out against a case of GESGP of 3 m pillar in a ultra thick coal seam of a 800 m cover depth. The results show that: ① Fragmentation and deformation of surrounding rock on the coal pillar side are larger than the other side. Fragmentation and deformation of pillar at the gob side is larger than the other; Although the buried depth is great, the gob is settled and a large amount of overburden load is sustained by it, so the stress is sufficiently transferred to the deep rocks; ② The deformation of the gob-side entry is asymmetrical, the roof sags more on the pillar side than the other, pillar rib top and solid coal side rid middle are greater with deformation occurring mostly at shallow part; ③ Gob is the “escape” passage for entry deformation which is good for slow release of deformation energy and reduction of burst; ④ The range of the pressure relief area is expanded from triangle before excavation to parallelogram after excavation, also the location of the stress concentration area is shifted to the upper right of the entry; ⑤ Interface of the first/second shear failure planes on the pillar and the high stress zone on the upper right of the entry are the key targeted control zones. The surrounding rock control system was put forward that coal pillar reinforcement based on multiple plastic zone development cycles and precise destress of high stress zone. The research can provide research foundation and scientific basis for the adjacent panels and other similar deep and inclined extra-thick coal seams

Energy Evolution Characteristics of Water-Saturated and Dry Anisotropic Coal under True Triaxial Stresses

During deep underground coal mining, water-injection-related engineering methods are generally carried out to reduce the hazards of coal dynamic disasters. The energy evolution characteristics of coal can better describe the deformation and failure processes, as it is more consistent with the in situ behavior of underground mining-induced coal. In this study, experimental efforts have been paid to the energy evolution characteristics of water-saturated and dry anisotropic coal under true triaxial stresses. The effects of water saturation, intermediate stress, and anisotropic weak planes of coal on the true triaxial energy evolution were systematically evaluated. The results show that the overall energy is weakened due to the water adsorption for water-saturated coal samples. The water-weakening effect on the overall energy of water-saturated coal is more pronounced when perpendicular to the bedding plane direction than in the other two cleat directions. The accumulation elastic energy anisotropy index of dry and water-saturated coal samples is higher than 100.00%. Both accumulation and residual elastic energy of dry and water-saturated coal samples show an increasing-then-decreasing trend with intermediate stress increase. The results obtained in this study help understand the in situ behavior of coal during deep underground mining and control coal dynamic disasters

The Research of Mathematical Method and Position Control of Actuator in Power Switchgear

Transient effects such as overvoltage and inrush currents will be caused due to opening and closing the switchgear at random phase. Phase-controlled technology present in recent years, which is restricted by the operation dispersion of actuator, can limit the transient effects. And the dispersion of the switchgear with a permanent magnetic actuator (PMA) is small. Therefore, the research of mathematical method and position control in this paper is based on the PMA. Firstly, the dynamic mathematical method and simulation system established in MATLAB are used to improve the design of the PMA owing same type. Secondly, simulation with the use of improved fuzzy algorithm is carried out. And an optimized self-adaptive fuzzy algorithm is obtained in the simulation process which can be used to trace the given displacement curve. Finally, a large number of tracing experiments have been done on the 35 kV breaker prototype to verify the effectiveness of the algorithm. In the experiments, the closing time of breaker can be stabilized within ±0.5 ms when capacitor voltage and capacitance change. These results prove that the mathematical model and the fuzzy algorithm are effective and practical

Experimental Study on Fragmentation Behavior of Specimen with Rockbolts

The effect of rockbolt density on fractured specimens and the distribution law of fragments were studied using the fractal method. The results show that with the increase of rockbolt density, the strength of specimens is improved. Its degree of fragmentation is increased, but the average size of fragments is decreased. The fragmentation and surface fractal dimensions are increased, their difference value is 1 in theory, but the value is slightly less than 1 in practical application due to the uncertain factors such as anisotropy of specimen. There is a positive correlation between the deformation of surrounding rock and its fractal dimension. The surface fractal dimension of surrounding rock can give a quantitative description of its degree of fragmentation and can give a comprehensive reflection to the roof stability. The support mechanism of rockblots can be understood as improving the probability of refragmentation of fragments, making its distribution gradation close to the optimal one with minimum porosity, thus reducing the deformation of surrounding rock

The Application of NdFeB in the Magnetic Force Actuator

In this paper, NdFeB is used to design a new type of magnetic force actuator (MFA) with simple structure and high reliability. The permanent magnets are fixed on the static iron-core to generate a magnetic field, while the movable part locates within the magnetic field. It can drive the arc extinguishing unit powered by the Lorentz force, and this can be applied to the operation of the long-stroke high voltage circuit breaker (HVCB). At the open and closed position, the PMs generate holding force for the moving iron-core to keep the static state. Then, the finite element method(FEM) and prototype test are adopted to study the properties of PM and characteristics of the actuator. The simulation concludes that the material type and structure size of PM, end cap material and processing deviation of the actuator will impact the static characteristic of the actuator. The results of the test on prototype show that MFA using NdFeB can achieve the high power output, which is conductive for electronic control as well as the displacement tracking. Due to its stable performance, NdFeB is reliable in the running of the magnetic force actuator. DOI: http://dx.doi.org/10.11591/telkomnika.v10i6.141

Research on Influence Factors and Acceleration Methods of Current Commutation

The vacuum interrupter is widely used due to the advantages of no arc-extinguishing medium and high insulation strength. However, the arc voltage generated by the commonly used CuCr contacts is low. In hybrid DC circuit breakers (DCCB), hybrid automatic transfer switches (ATS), medium voltage compound switches and other fields, it is difficult to rely on vacuum arc to complete natural commutation, which restricts the development of hybrid switches. In order to understand the current commutation process deeply, the influence of internal and external factors on the current commutation is analyzed by experiments. The coupling mathematical model of arc-commutated branch is established. The criterion for the success of current commutation is summarized. The parameters of the arc model are reconstructed through repeated breaking experiments to explore the influence of internal factors on the arc characteristics. Based on this, the influence law of arc current, contacts gap and transverse magnetic field (TMF) is analyzed. An acceleration method of current commutation is proposed. A prototype for accelerating experiments with an electromagnetic repulsion mechanism and TMF is developed. The commutated branch equivalent to practical applications is built. The experimental results show that the commutation time is effectively shortened and meets the requirements of practical applications through the acceleration method, which provides new thought for the development of hybrid switches

Vacuum Large Current Parallel Transfer Numerical Analysis

The stable operation and reliable breaking of large generator current are a difficult problem in power system. It can be solved successfully by the parallel interrupters and proper timing sequence with phase-control technology, in which the strategy of breaker’s control is decided by the time of both the first-opening phase and second-opening phase. The precise transfer current’s model can provide the proper timing sequence to break the generator circuit breaker. By analysis of the transfer current’s experiments and data, the real vacuum arc resistance and precise correctional model in the large transfer current’s process are obtained in this paper. The transfer time calculated by the correctional model of transfer current is very close to the actual transfer time. It can provide guidance for planning proper timing sequence and breaking the vacuum generator circuit breaker with the parallel interrupters