【作者】 王彬；

【导师】 吴双应；

【作者基本信息】 重庆大学 ， 工程热物理， 2007， 硕士

【摘要】 雾化通常指通过物理方法将一定体积的液体在气体的冲击作用下破碎为弥散微细液滴群的过程。雾化的主要目的是使液体产生高的表面积与质量比,雾化产生的条件是液体与周围气体之间存在较高的相对速度。雾化技术几乎已经涵盖所有的工业领域,如交通运输、农业生产,以及人民的日常生活。除了各种燃料(气体、液体和固体燃料)的燃烧外,雾化技术还在非燃烧工业如催化造粒、食品加工、粉末涂覆、农药喷洒等方面也有着广泛的应用。压力雾化器是利用压力使液体碎裂成为雾滴,该雾化器具有结构简单、加工制造容易、安装操作方便、雾化粒度较均匀、工作能耗低、雾炬张角适中,以及对雾化后加工装置(喷雾干燥塔)中的流场影响小等优点,已被广泛应用于实际生产中。本文的主要研究内容有:简要介绍了喷嘴及其技术的发展历史、研究背景。着重对该技术在造粒方面的应用作了介绍,并对雾化机理及其研究状况作了详细的综述。造粒是利用压力式雾化装置将原料液分散成细小雾滴,并与冷空气在造粒塔内充分进行热量交换,最终达到凝固冷却产品的目的。产品可以根据需要生产成细粉状、颗粒状、空心球状或团聚状。可通过改变喷嘴的内部结构得到所需要的喷液量和雾滴尺寸。为解决某化工厂在实际生产中存在的堵塞问题,设计制造了一种喷枪,用来替代造粒机造粒,并将生产中存在的物料粘壁性问题作为选择雾化角的依据之一。从理论上通过对造粒塔中单颗粒的运动进行受力分析,建立了颗粒运动速率方程,并结合单颗粒与气流间的Ranz和Marshall传热关联式建立了颗粒的对流换热模型。以此模型为基础,对颗粒的运动和温度变化进行了数值模拟,讨论了在不同颗粒直径下雾化角的取值及不同雾化角下颗粒温度的变化规律。在实验方面,本文以纯水为雾化介质,系统地研究了压力式喷嘴喷雾特性;测得了喷嘴流量、喷雾角随压力的变化关系,对喷嘴的雾化质量进行评价。以此为基础对设计进行了校正,对实际工程具有一定的指导意义。更多还原

【Abstract】 Atomization is a process in which liquid is broken into pieces under the impact of gas by physical method. The main purpose of atomization is to get high ratio of surface area and quality. When high relative speed arises between the liquid and surroundings gas, atomization will generate. The atomization technique is widely used both in the combustion of various fuels and the unburnable industrial field such as granulation, food processing, power spray and agrochemical to spray aspect. The principle of pressure atomizer is using pressure to make liquid into fog. It has simple structure and it is manufactured, installed and operated conveniently. The atomizer’s energy consume is low and it has little infection on the manufacture equipment after atomization process. The grain obtained is even and atomization angle is moderate. Beacause of so many advantages the pressure atomizer have already been applied extensively in production.The main contents of this paper are:The development history and research background of nozzle are introduced. Then the application of the technology to granular is instructed, and the atomization mechanism and its research status are explained in detail.The granular is a process in which liquid is seperated into small droplets by use of the pressure atomizer, and those droplets are cooled by cold air in granular tower to achieve solidification in the end. The product can be made into small powder, granular, hollow globosity and reunite according to the actual requiements. In order to get the right drop size, the internal structure of atomizer can be changed.In order to solve the jam problem in actual product, a spray-gun is designed to replace granular machine, and the question which is materials stick to the wall as one of important roles to alter the atomizing angle. Through the force analysis of the particle movement and combining the heat transfer correlations of Ranz and Marshall between single particle and air current in granular tower, the velocity equation of the particle movement and the model of the particle convective heat transfer are build. The numerical simulation of the particle movement and temperature variation has been achieved. The atomizing angle on different particle diameter and the temperature variation on different atomizing angle have been discussed. Water is used as working fluid of atomization in this paper. The spray characteristics of pressure nozzle are investigated systemeticly. The relation between nozzle flow capacity, spray angle and pressure is measured and the atomization quality of the nozzle is evaluated. The designing of nozzle is corrected on the basis of the experiment results. The conclusions of this paper have great instructive meaning to the actual engineering.更多还原