MG300/700-WD2型窄机身大功率电牵引采煤机设计

主要针对目前可配套SGZ630刮板输送机的中厚煤层电牵引采煤机截割功率偏低、牵引力偏小及智能化功能欠缺等不足,通过整机扩容和优化、配套性能、可变机面高度、智能化系统、带负载敏感比例阀液压系统和防转防松型铰接销轴等方面的研究,设计了最小可配套SGZ630刮板输送机的MG300/700-WD2型窄机身大功率智能化电牵引采煤机,为经济性开采的中小矿井提供了一款新的设备。

凉水井矿中厚煤层年产6Mt工作面国产设备选型

基于凉水井煤矿中厚煤层开采实践,采用理论分析与数值模拟方法对工作面年产6Mt国产综采设备选型关键技术进行分析论证。研究结果表明:凉水井煤矿可通过提高设备综合开机率、优化工作面长度、增加割煤作业时间来提高工作面产量,确定液压支架型号为ZY12000/20/40D,支架结构简单、实用、可靠。采用高压变频软启动刮板输送机,具有可靠性高、节能、维护方便等优点。采用大功率、矮机身采煤机,采煤机总装机功率达到2150k W,机面高度1549mm,适用于中厚煤层条件,保证了采煤机的割煤速度与开机率。

MG200/450-WD型薄煤层滚筒采煤机

介绍MG200/450-WD型滚筒采煤机的主要技术特点及其在大同煤矿集团公司井下应用情况,显示出该采煤机技术先进,可望成为我国薄煤层开采的主力机型。

三软煤层中选取采煤机主参数注意的问题

介绍三软煤层的特点及采煤机在三软煤层中的使用工况 ,提出了采煤机在三软煤层配套及使用中的注意事项 ,为三软煤层综采配套采煤机的选型提供了理论分析和参考意见。

Research on temperature rise of hoisting machine disk brake

A mathematical model and finite element model for analysis of temperature rise of the hoisting machine brake sys- tem was constructed, limit conditions were defined, and the law of temperature rise of brake shoes during emergent brake course was analyzed and calculated by using finite element software. By analyzing the calculation results, the law of tempera- ture change of surface of brake disk and shoes during the braking process was found. The law of brake shoes surface tempera- ture distribution and the law of temperature change along with thickness of brake shoes at brake time 0.5 s, 1.0 s and 1.5 s was analyzed. A hoisting machine emergent braking test was carried out. Finally, the author concluded that velocity rebound in the process of hoisting machine emergent brake is due to decreased friction coefficient caused by the temperature rise of the brake shoes surface.

Spatiotemporal features and possible mechanisms of seasonal changes in sea surface height south of Japan

Variations of sea surface height （SSH） in the Kuroshio south of Japan are addressed by analyzing 19-year （1993-2011） altimetry data from AVISO. Regionally averaged time series of observed SSH had a rising linear trend at 2.64＋0.72 mrn/a in this period. By analyzing the power spectra, several periods were recognized in temporal SSH variations, including those around 90 and 360 days. The seasonal cycle of SSH was minimum in winter （February） and maximum in summer （August）, with peak-to-peak amplitude about 20.0 cm. The spatial distribution of linear trends was inhomogeneous, with a rising linear trend along the coastline and a tripole structure offshore. Spatial distributions of standard deviation of seasonal SSH show very dynamic activities in the southeast of Kyushu and south of Honshu. Seasonal variations of observed SSH are partially explained by surface buoyancy forcing, local wind forcing and the steric component related to subsurface water beneath the mixed layer. Results show different spatial distributions of correlation coefficient and estimation skill between seasonally observed and modeled SSH, which are calculated from surface buoyancy flux, local wind forcing and the steric component related to subsurface water. Of those three, the surface buoyancy flux has a greater contribution to variations of observed SSH on the seasonal time scale south of Japan.

CALPHAD-aided design of high entropy alloy to achieve high strength via precipitate strengthening

Designing high entropy alloys(HEAs) with high strength and excellent ductility has attracted extensive scientific interest. In the present work, the CALPHAD(calculation of phase diagrams) method was applied to guide the design of an(FeCoNi)92Al2.5Ti5.5 HEA strengthened by precipitation hardening. The grain size as well as the size and volume fraction of the precipitates was tailored via a thermomechanical process to optimize the mechanical properties.The uniformly dispersed nano-precipitates are Ni3(Al,Ti)-type precipitates with an L12 ordered structure presenting a fully coherent interface with the face-centered cubic(FCC) matrix.The yield strength of the alloy increases from 338.3 to1355.9 MPa and the ultimate tensile strength increases from 759.3 to 1488.1 MPa, while the elongation maintains a reasonable value of 8.1%. The striking enhancement of strength is mainly caused by the precipitate’s hardening mechanism,which is evaluated quantitatively by various analytical models.The deformation-induced microbands and the coherent precipitates sheared by dislocations are the deformation and strengthening mechanisms contributing to the superior combination of ductility and strength in the present HEA.This investigation demonstrates that the CALPHAD method is beneficial to the design and optimization of HEAs.

Experimental Research of Surface Roughness Effects on Highly-Loaded Compressor Cascade Aerodynamics

Aircraft engines deteriorate during continuous operation under the action of external factors including fouling, corrosion, and abrasion. The increased surface roughness of compressor passage walls limits airflow and leads to flow loss. However, the partial increase of roughness may also restrain flow separation and reduce flow loss. It is necessary to explore methods that will lower compressor deterioration, thereby improving the overall performance. The experimental research on the effects of surface roughness on highly loaded compressor cascade aerodynamics has been conducted in a low-speed linear cascade wind tunnel. The different levels of roughness are arranged on the suction surface and pressure surface, respectively. Ink-trace flow visualization has been used to measure the flow field on the walls of cascades, and a five-hole probe has been traversed across one pitch at the outlet. By comparing the total pressure loss coefficient, the distributions of the secondary-flow speed vector, and flow fields of various cases, the effects of surface roughness on the aerodynamics of a highly loaded compressor cascade are analyzed and discussed. The results show that adding surface roughness on the suction surface and pressure surface make the loss decrease in most cases. Increasing the surface roughness on the suction surface causes reduced flow speed near the blade, which helps to decrease mixing loss at the cascades outlet. Meanwhile, adding surface roughness on the suction surface restrains flow separation, leading to less flow loss. Various levels of surface roughness mostly weaken the flow turning capacity to various degrees, except in specific cases.

Enhanced mechanical properties in oxide-dispersion-strengthened alloys achieved via interface segregation of cation dopants

With significantly enhanced irradiation resistance,high-temperature strength,and creep resistance,oxide-dispersion-strengthened tungsten(ODS-W)alloys present tremendous potential for high-temperature applications.However,the oxide particles tend to segregate at W grain boundary and grow up(even to micron),greatly suppressing their strengthening effect.It is always a great challenge to effectively refine and disperse the oxide particles at W grain boundary.Here,we successfully developed a new type of cation-doped W-Y2O3 alloy via a wet chemical method and subsequent low-temperature sintering.It was found that proper cation doping could not only significantly refine the intergranular Y2O3 second phase particles but also dramatically improve the sinterability of W matrix.These doping effects,as a result,simultaneously enhance the strength and ductility of the W-Y2O3 alloy.It was confirmed that the segregation of cation dopants at the W/Y2O3 interface is the origin of these doping effects.Furthermore,X-ray photoemission spectra(XPS)analyses confirmed that cation dopant segregation also obviously affects the chemical bonding(i.e.,W–O bond)along the W/Y2O3 interface.As a result,the ratelimiting mechanism for W grain growth is influenced remarkably,explaining well the difference of W grain size in various cation-doped W-Y2O3 alloys.For the refinement of intergranular Y2O3 particles,it can be understood well from both thermodynamic and kinetic views.Detailedly,W/Y2O3 interfacial energy and atom mobility for Y2O3 coarsening are all limited by cation dopant segregation.More importantly,this cation-doping approach can also be applicable to other ODS alloys for enhancing their comprehensive mechanical properties.