The current popular methods for decision making and project optimisation in mine ventilation contain a number of deficiencies as they are solely based on either subjective knowledge or objective information.This paper...The current popular methods for decision making and project optimisation in mine ventilation contain a number of deficiencies as they are solely based on either subjective knowledge or objective information.This paper presents a new approach to rank the alternatives by G1-coefficient of variation method.The focus of this approach is the use of the combination weighing,which is able to compensate for the deficiencies in the method of evaluation index single weighing.In the case study,an appropriate evaluation index system was established to determine the evaluation value of each ventilation mode.Then the proposed approach was used to select the best development face ventilation mode.The result shows that the proposed approach is able to rank the alternative development face ventilation mode reasonably,the combination weighing method had the advantages of both subjective and objective weighing methods in that it took into consideration of both the experience and wisdom of experts,and the new changes in objective conditions.This approach provides a more reasonable and reliable procedure to analyse and evaluate different ventilation modes.展开更多
失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内...失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内部流动特性分析可知,0.70倍设计流量(0.70Q_(d))和0.65Q_(d)是失速发展阶段的典型工况,流场的周向均匀性存在不同程度的破坏。2个典型失速工况下,随着进口含气率的增加,泵的性能下降但下降幅度相比设计工况和深度失速工况小,气相主要附着在叶片压力侧前缘附近且附着面积逐渐增大,失速流道压力侧前缘的相对速度角增大,流动方向整体向吸力侧偏移,使得吸力侧前缘冲角减小,抑制了吸力侧前缘分离涡和中间位置漩涡的融合,进而抑制了失速的发生。引入流量变异系数(coefficient of variance,CV)定量分析流场的周向均匀性,随着流场改善,CV值逐渐减小,当模型泵处于失速初生点时,CV值位于1.38%~3.69%。少量气体加入使得失速发展阶段离心泵性能下降幅度减小且抑制失速发生。研究结果可为拓宽离心泵的高效区和提高安全稳定运行提供参考。展开更多
基金Projects(51504286,51374242)supported by the National Natural Science Foundation of ChinaProject(2015M572270)supported by China Postdoctoral Science FoundationProject(2015RS4004)supported by the Science and Technology Plan of Hunan Province,China
文摘The current popular methods for decision making and project optimisation in mine ventilation contain a number of deficiencies as they are solely based on either subjective knowledge or objective information.This paper presents a new approach to rank the alternatives by G1-coefficient of variation method.The focus of this approach is the use of the combination weighing,which is able to compensate for the deficiencies in the method of evaluation index single weighing.In the case study,an appropriate evaluation index system was established to determine the evaluation value of each ventilation mode.Then the proposed approach was used to select the best development face ventilation mode.The result shows that the proposed approach is able to rank the alternative development face ventilation mode reasonably,the combination weighing method had the advantages of both subjective and objective weighing methods in that it took into consideration of both the experience and wisdom of experts,and the new changes in objective conditions.This approach provides a more reasonable and reliable procedure to analyse and evaluate different ventilation modes.
文摘失速工况下,气液两相流离心泵的内部流动极为复杂。为探究不同进口含气率对离心泵失速工况流动特性的影响,该研究基于欧拉-欧拉非均相流模型和SST k-ω湍流模型,分析了进口含气率对离心泵性能的影响规律。纯水条件下,基于性能曲线和内部流动特性分析可知,0.70倍设计流量(0.70Q_(d))和0.65Q_(d)是失速发展阶段的典型工况,流场的周向均匀性存在不同程度的破坏。2个典型失速工况下,随着进口含气率的增加,泵的性能下降但下降幅度相比设计工况和深度失速工况小,气相主要附着在叶片压力侧前缘附近且附着面积逐渐增大,失速流道压力侧前缘的相对速度角增大,流动方向整体向吸力侧偏移,使得吸力侧前缘冲角减小,抑制了吸力侧前缘分离涡和中间位置漩涡的融合,进而抑制了失速的发生。引入流量变异系数(coefficient of variance,CV)定量分析流场的周向均匀性,随着流场改善,CV值逐渐减小,当模型泵处于失速初生点时,CV值位于1.38%~3.69%。少量气体加入使得失速发展阶段离心泵性能下降幅度减小且抑制失速发生。研究结果可为拓宽离心泵的高效区和提高安全稳定运行提供参考。
