Production of fine grain limestone by means of focusing and rounding water jets

为了明确水射流和磨粒射流聚焦和（或）圆磨对石灰石破碎的适用性，进行了实验研究，为今后水射流磨机的设计提供了基础数据。本文对水射流磨机的可行性进行了实验研究，主要包括以下四个部分：用冲击力测量法估算水射流的入射速度。为了阐明岩石的破裂机理，提出了一种评价岩石表面水射流结构的实用方法。分析了水射流正常撞击平面目标所产生的合力，从而估计了柱状水射流的入射速度和表观密度。水射流冲击岩石的侵蚀特性。提出了一种适用于分析低速水射流正常撞击岩石表面破碎切割过程的理论。非遍历和遍历两种情况都被考虑。磨料水射流破碎性能研究。细粒岩石受到圆柱形水射流的加速，撞击固体目标。分析了细粒岩石的破碎性能，以及固体目标：铝、低碳钢、硬质金属、氧化铝和锆的侵蚀剖面。coanda喷嘴内部流动及其对粘性粉末分散的影响。本文所研究的康达喷嘴是一种形状类似拉瓦尔喷嘴的喷射泵。用单斜热线风速仪测量了三维平均流量，表明雷诺应力对粘性粉末的分散作用远大于剪切应力。

In order to make clear the applicability of water jet and abrasive jet of focusing and/or rounding to the fragmentation of limestone, the experimental study has been performed and the fundamental data have been presented for the future design of water jet mill. The present experimental study on the possibility of water jet mill consists of four parts as follows :1. Estimation of incident velocity of water jets by means of impact force measurement.A practical method to evaluate the structure of water jets impinging onto the rock surface has been presented for the clarification of the fracture mechanism of rock. The impact force that is the resultant force imposed upon a plain-target by water jet impinging normally has been analyzed to estimate the incident velocity and the apparenet density of cylindrical water jets.2. Erosion characteristics of rock by water jet impingement.A theory is presented which is applicable to the analysis of erosion process in fragmentation and cutting of rock by a relatively low speed water jet impinging normally onto a rock surface. Both nontraversing and traversing cases are considered.3. Fragmentation performance of abrasive-water jet.Fine grain rocks have been accelerated by cylindrical water jet and impinged against a solid target. The fragmentation performance of fine grain rocks has been analyzed as well as the erosion profile of solid targets : aluminium, mild steel, hard metal, alumina and zirconium.4. Internal flow of coanda nozzle and effect on dispersion of cohesive powders.Coanda nozzle studied in this work is classified as a jet pump with a shape resembling the Laval nozzle. Three-dimensional mean flow has been measured by a single inclined hot-wire anemometer, and it has been clarified that Reynolds stress plays an important roll in dispersing cohesive powders is much greater than the shear stress.