Coupling Tribocharging and Hydrodynamics in Fliuidized Beds

CBET-1601986PI：Sundaresan，Sankaran摩擦充电是指两种材料之间相互机械接触的电荷交换。在许多涉及悬浮在气体中的颗粒流的情况下都能观察到这种现象。一个工业上重要的例子是在流态化化学反应器中进行摩擦充电。在这种反应器中，气体以极高的速度流过颗粒床，颗粒变得“流态化”，颗粒和气体表现为流体混合物。这个项目试图了解摩擦荷电如何影响气粒悬浮液的流体动力学。将开发模型来解释和预测材料特性、湿度和颗粒大小如何影响摩擦荷电动力学和气粒悬浮液的流体动力学。这项研究将是第一次专门关注摩擦荷电和流态化流体力学之间的耦合的研究。这些结果将在涉及气固悬浮液的广泛工业过程中有用，因为摩擦带电会产生重大危险并降低过程效率。该项目将为不同学术水平的学生提供参与研究的机会，包括参加普林斯顿大学暑期实验室学习项目的高中生。该项目的目标是开发和验证一个计算模型，用于解释流体-颗粒流动系统中的摩擦荷电和静电力，了解静电学如何影响流体动力学，以及了解这些系统中的充电瞬变率。该模型将使用一个有效的功函数来描述由于接触颗粒材料的不同、接触颗粒总电荷的不同、接触颗粒尺寸的不同和湿度的不同而引起的电荷转移。有效功函数将被合并到一个模型中，该模型结合了用于解决颗粒接触的离散元方法和用于解决更大尺度流动的计算流体动力学。模型参数将通过振动台实验进行校准。然后，将用系统变化的颗粒材料、大小、湿度和床壁材料的实验来检验该模型对流态化动力学的预测。研究结果将为工业从业者改进涉及颗粒材料的工艺提供有用的信息。

CBET - 1601986PI: Sundaresan, SankaranTribocharging refers to the exchange of electric charge between two materials that make mechanical contact with each other. It is observed in many situations involving flows of particles suspended in a gas. One industrially important example is tribocharging in a fluidized bed chemical reactor. In this kind of reactor, gas flows through a bed of particles at such high rates that the particles become "fluidized," and the particles and gas behave as a fluid mixture. This project seeks to understand how tribocharging affects the fluid dynamics of gas-particle suspensions. Models will be developed to explain and predict how the dynamics of tribocharging and hydrodynamics of gas-particle suspensions are affected by material characteristics, humidity, and particle size. The research will be the first study that focuses specifically on the coupling between tribocharging and fluidization hydrodynamics. The results will be useful in a wide range of industrial processes involving gas-solid suspensions, because tribocharging can create significant hazards and reduce process efficiencies. The project will provide opportunities for students at various academic levels to participate in research, including high-school students who participate in Princeton's summer Laboratory Learning Program.The goals of the project are to develop and validate a computational model that accounts for tribocharging and electrostatic forces in fluid-particle flow systems, to understand how electrostatics affect hydrodynamics, and to understand the transient rate of charging in these systems. The model will use an effective work function for triboelectric charging that captures charge transfer owing to differences in material of contacting particles, differences in overall charge of contacting particles, differences in sizes of the contacting particles and humidity. The effective work function will be incorporated into a model that combines a discrete element method for resolving particle contacts with computational fluid dynamics for resolving larger scales of the flow. Model parameters will be calibrated using vibrated bed experiments. Then, the model's predictions of fluidized bed dynamics will be tested against experiments in which particle material, size, humidity and the wall material of the fluidized bed are systematically varied. Results of the study will provide useful information for industrial practitioners to improve processes involving granular materials.