Atomization of High Viscosity and Suspension Fluids

在加拿大的油砂中，沥青与蒸汽混合，然后将混合物喷入焦化装置，将沥青提炼成合成原油。喷雾特性是该工艺效率的决定因素之一。然而，由于这种流体(沥青-蒸汽混合物)的复杂性，关于这些喷雾的喷雾特性的信息非常有限。已有的关于这类体系的研究，已经用水和空气的混合物或一些油和空气的混合物取代了这种复杂的混合物。沥青-蒸汽混合物是一种悬浮固体颗粒所占比例较大的高粘度流体，用水-气混合物来模拟过于简单。 本研究的目的是描述具有悬浮颗粒的高粘度流体的喷雾特性，特别是实际的沥青-蒸汽混合物，以及煤浆。为了实现这一目标，将开展以下工作。(1)开发了一个雾化和喷雾模型，以预测加拿大油砂中使用的典型喷嘴上悬浮的重油和液体的喷雾形成。(2)对加拿大油砂中使用的喷嘴进行试验性喷雾测试，使用实际流体，如带有悬浮液的沥青和重油。(3)利用所建立的雾化模型对加拿大油砂实际流体的雾化特性进行了预测。使用实验数据微调喷雾模型。(4)用验证后的喷雾计算程序对大型喷嘴的喷雾特性进行了预测。(5)进行参数研究，以改善喷嘴的性能，包括喷雾液滴尺寸和减少喷嘴的磨损。 本研究还旨在解决以下问题：(I)在高度湍动的射流中，是什么触发了气液界面的不稳定性，以及这种不稳定性是如何增长的，从而导致韧带和液滴的形成。(Ii)液体粘度如何影响液团从界面上的破碎？(3)悬浮粒子的存在对雾化过程有何影响？

In Canada's oil sands, bitumen is mixed with steam and the mixture is sprayed into a coker to upgrade bitumen to synthetic crude oil. The spray characteristics is one of the determining factors in the efficiently of this process. However, due to the complexity of this fluid (bitumen-steam mixture), there is very limited information on the spray characteristics of these sprays. The available studies on this type of systems, have replaced this complex mixtures with water and air mixtures or some oil and air mixtures. Bitumen-steam mixture is a highly viscous fluid with large percentage of suspended solid particles, and it is too simplistic to model it with mixture of water-air. The objective of the present proposed research is to characterize sprays of high viscosity fluids with suspended particles, in general, and actual bitumen-steam mixtures, as well as coal slurries, in particular. In order to achieve this objective the following tasks will be pursued. (1) Develop an atomization and spray model to predict the spray formation of heavy oils and liquids with suspensions from typical nozzles used in Canadian oil sands. (2) Conduct experimental spray testing on nozzles used in Canadian oil sands using actual fluids, such as bitumen and heavy oils with suspensions. (3) Use the atomization model developed here to predict spray characters from the Canadian oil sands with actual fluids. Use the experimental data to fine tune the spray model. (4) Use the validated spray code to predict the spray characteristics of large scale nozzles. (5) Perform parametric studies to improve nozzle performance both in terms of spray droplet sizes and also reducing wear and tear of the nozzle. The present research is also aimed at addressing the following questions: (i) In a highly turbulent jet, what triggers the gas-liquid interface instability and how does this instability grow resulting in the formation of ligaments and droplets. (ii) How does the liquid viscosity affect the breakup of liquid masses from an interface? (iii) How the existences of suspended particles effect the atomization process?