Experimental test and theoretical calculation of the fracture height limit of gas pipe flow to Darcy flow

Low-speed flow experiments in which ultra-fine copper tubes are used to simulate micro-fractures in carbonate strata are conducted to analyze the variations of gas flow state in fractures of different fracture heights,determine flow state transition limit and transition interval,and establish the calculation method of flow state transition limit.The results show that the ideal Hagen-Poiseuille flow is the main form of gas flow in large fractures.Due to the decrease of fracture height,the gas flow in the fracture changes from Hagen-Poiseuille flow with ideal smooth seam surface to non-Hagen-Poiseuille flow,and the critical point of the transition is the boundary of flow state transition.After the fracture height continues to decrease to a certain extent below the boundary of the flow state transition fracture height,the form of gas flow gradually changes to the ideal Darcy flow,thus the transition interval of the gas flow state in the closing process of fracture can be determined.Based on the three-dimensional microconvex body scanning of the fracture surface,the material properties of fracture and properties of fluid in the fracture,a method for calculating the boundary of flow state transition is established.The experimental test and theoretical calculation show that the limit of the fracture height for the transition from pipe flow to Darcy flow is about twice the sum of the maximum height of the microconvex bodies on the upper and lower sides of the fracture.

限流式统一潮流控制器的动态分析与实验

限流式统一潮流控制器(UPFC)是一种可以有效应对系统短路电流冲击的新型柔性交流输电系统(FACTS)装置。文中分析了系统短路时限流式UPFC的详细动态过程和限流工作原理,建立了故障下的数学模型。以系统限流指标、直流电容电压限值和绝缘栅双极型晶体管(IGBT)电流限值3个条件为依据,给出了直流限流电感的计算方法和选取原则。100V/3kVA限流式UPFC实验装置平台的实验结果证实了限流动态过程分析的合理性和限流式UPFC的有效性。

气体管流到达西流的缝高界限实验测试与理论计算

采用超细铜管模拟碳酸盐岩地层中微裂缝,开展低速流动实验,分析气体在不同缝高裂缝中的流动状态变化,确定流动状态转换界限及转换区间,建立流动状态转换界限计算方法。研究表明,气体在缝高较大裂缝中的流动形式以理想的哈根-泊肃叶流动为主。由于缝高的减小,气体在裂缝中的流动从以理想光滑缝面的哈根-泊肃叶流动为主向非哈根-泊肃叶流动为主转换,转换的临界点即为流动状态转换界限。裂缝缝高在流动状态转换缝高界限以下继续减小到一定程度后,气体流动形式逐渐向理想的达西流动转换,从而可以确定裂缝在闭合过程中流动状态的转换区间。综合裂缝面的三维微凸体扫描结果、裂缝的材料性质及流体性质,建立了流动状态转换界限计算方法。实验测试和理论计算表明:从管流到达西流的缝高界限约为裂缝上、下两面微凸体最大高度之和的2倍。

反应堆压力容器下降段水-蒸汽CCFL实验与模型研究

为探究反应堆压力容器下降段在喷放末期冷段安注过程中的水-蒸汽逆流特性,建立下降段逆向流动限制(CCFL)模型,开展了基于压力容器模化本体的下降段CCFL实验研究以及建模分析。通过实验研究获得了不同入口安注水流量、安注水过冷度、堆芯蒸汽流量等条件下的下降段环腔内的安注特性数据,并基于实验数据进行了CCFL建模分析。结果表明,开始发生CCFL的蒸汽无量纲流速与入口安注水无量纲流速呈现正相关,基于无量纲流速建立的模型斜率与入口安注水无量纲流速呈现高度指数关联。本文建立了适用于从不发生CCFL至不完全CCFL,再到完全CCFL的下降段水-蒸汽气液逆流全过程预测模型。

石炭沟河下煤层安全开采厚度模拟

通过分析杉木树煤矿的水文地质条件,应用物理相似和数值模拟实验方法,模拟开采引起覆岩冒裂带发育高度、范围和地表裂缝情况;结合F-RFPA2D数值试验模拟固液耦合条件下开采引起覆岩导水裂缝带的高度及其发展形态和渗流过程。实验结果显示,采高2 m时导水裂隙带高度为70 m对采区覆岩和河床破坏较小,可以实现石炭沟河下安全采煤。