对掘进工作面依炸药量计算风量的实用法

探讨了采用压入式通风的掘进工作面依据炸药量计算风量简化式的由来及据实计算应用问题。

基于网络解算的矿井通风及通风设施研究

矿井通风系统对矿井安全地开拓开采起着重要作用。以山西马脊梁煤矿为研究对象,根据矿井西部侏罗系煤炭井田封闭收缩计划,结合3DVent软件,对矿井收缩封闭前后的风量变化进行了分析,发现当西部二号风井停用后,矿井的行人副斜井、进风斜井和副立井处的风量会受到较大的影响。之后,开展了风量短路实验,定量地分析了短路前后井下各用风地点的风量变化以及一号风井和三号风井处主要通风机的风量及风压变化。最后结合风量解算结果以及风量短路实验结果,建立了一种新型的增阻风门设施,以增加进风井的风阻,从而达到满足矿井用风量的目的。

3DVent软件风量模拟在调节风门优化设计中的应用

完善的通风系统可保障矿井安全地进行开拓开采。采用3DVent软件对马脊梁煤矿封闭期间运用的西部二号风井处主要通风机停工前后的风量变化进行了分析,发现当西部二号风井处的主要通风机停用后,行人副斜井、进风斜井、副立井以及1136大巷处的风量会受到明显地影响,西部一号风井和三号风井处主要通风机的风压会减小。由此,建立了一种新型的两用调节风门设施,既可用于井下的增阻调节,也可用于井下掘进和回采时的风量调节。

巷道式通风在特长瓦斯隧道施工中的应用

随着昭通高速路网逐渐发展、完善,昭泸、宜毕、宜昭等多条高速也相继建设起来,公路建设多穿越高山峡谷地区,长隧道、特长隧道成为公路施工常设结构。结合四川宜宾至云南昭通高速公路工程在建的特长瓦斯隧道——新场隧道施工实例,对该特长隧道通风进行优化,研究通风方案及原理、通风检算、通风管理方案入手,进行了分析。结论证实,新场隧道通风方案采用隧道超前段风袋、隧道正洞与回风巷道共同组成新型巷道式循环通风系统,以提高送风排风效率,同时通过通风设备防爆改装,配合甲烷传感器及风速传感器等实时监控,施工方案科学合理、安全可靠,保证了隧道施工安全。

井下通风网络分析与方案优化

为解决传统矿井通风系统无法满足矿井扩产需求,在以老矿井为例分析其通风现状的基础上,对当前井下通风系统进行测定和评价,并针对其所存在的问题初步提出整改建议;最后,在上述分析的基础上对工作面的需风量进行重新核算,并提出三套优化方案,最终确定方案二为最佳方案。

亿隆煤业通风系统优化改造

针对亿隆煤业矿井通风阻力较大、总回风量不足的问题,建立了矿井约束型风量解算模型,从理论上证明了通风量不足的问题,以此为基础,提出将3号煤层回风大巷断面从18 m2扩大至22 m2。优化后的通风系统下巷道通风阻力及风速均满足安全生产的标准,实现了进风系统和回风系统风流的平衡,确保了各工序的顺利进行。

A Physics-Based Dual-Frequency Approach for Altimeter Wind Speed Retrieval

The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study.

Fluent-based numerical simulation of flow centrifugal fan

Testing centrifugal fan flow field by physical laboratory is difficult because the testing system is complex and the workload is heavy, and the results observed by naked-eye deviates far from the actual value. To address this problem, the computational fluid dynamics software FLUENT was applied to establish three-dimensional model of the centrifugal fan. The numeral model was verified by comparing simulation data to experimental data. The pressure centrifugal fan and the speed changes in distribution in centrifugal fan was simulated by computational fluid dynamics soft-ware FLUENT. The simulation results show that the gas flow velocity in the impeller increases with impeller radius increase. Static pressure gradually increases when gas from the fan access is imported through fan impeller leaving fans.

Retrieval algorithm of sea surface wind vectors for WindSat based on a simple forward model

WindSat/Coriolis is the first satellite-borne polarimetric microwave radiometer, which aims to improve the potential of polarimetric microwave radiometry for measuring sea surface wind vectors from space. In this paper, a wind vector retrieval algorithm based on a novel and simple forward model was developed for WindSat. The retrieval algorithm of sea surface wind speed was developed using multiple linear regression based on the simulation dataset of the novel forward model. Sea surface wind directions that minimize the difference between simulated and measured values of the third and fourth Stokes parameters were found using maximum likelihood estimation, by which a group of ambiguous wind directions was obtained. A median filter was then used to remove ambiguity of wind direction. Evaluated with sea surface wind speed and direction data from the U.S. National Data Buoy Center （NDBC）, root mean square errors are 1.2 rn/s and 30~ for retrieved wind speed and wind direction, respectively. The evaluation results suggest that the simple forward model and the retrieval algorithm are practicable for near-real time applications, without reducing accuracy.

Genetic Optimization Algorithm of PID Decoupling Control for VAV Air-Conditioning System

Variable-air-volume (VAV) air-conditioning system is a multi-variable system and has multi coupling control loops. While all of the control loops are working together, they interfere and influence each other. A multivariable decoupling PID controller is designed for VAV air-conditioning system. Diagonal matrix decoupling method is employed to eliminate the coupling between the loop of supply air temperature and that of thermal-space air temperature. The PID controller parameters are optimized by means of an improved genetic algorithm in floating point representations to obtain better performance. The population in the improved genetic algorithm mutates before crossover, which is helpful for the convergence. Additionally the micro mutation algorithm is proposed and applied to improve the convergence during the later evolution. To search the best parameters, the optimized parameters ranges should be amplified 10 times the initial ideal parameters. The simulation and experiment results show that the decoupling control system is effective and feasible. The method can overcome the strong coupling feature of the system and has shorter governing time and less over-shoot than non-optimization PID control.

Connecting Wind Turbine Generator to Distribution Power Grid--A Preload Flow Calculation Stage

A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.

Lower Partial Moments as Measures of Perceived Risk： An Experimental Study in China

The paper reports an experiment in China on individual investors＇ risk perception. The main findings are similar with the results in Matthias （2000）, but the absolute value of correlation coefficients between risk measures and risk ratings are higher.