Numerical modeling of dust particle trajectories in a cyclonic vacuum cleaner and determination of dust collection efficiency

Cleaning is a term which has started with the existence of human being and has been coming since today. Not only the personal cleaning but also cleaning of the living space are crucial parameters for human health. In ancient times, people have not attached importance to the cleaning and because of the health problems resulted from not to cleaning, they had lost their lives in early ages. Due to the increasing knowledge and experiences, cleaning and hygiene terms have been adopted by society and the average life expectancies have been increased. Moreover, people have given more attention to the cleaning because of decontamination of their living spaces from viruses and bacterias. By doing this, they have found the fundamentals of cleaning habit. Coming from the ancient times to nowadays, cleaning by hand has changed the roles with besom; moreover, vacuum cleaners which are used today have been invented. With the invention of a vacuum cleaner, living areas have been sterilized more. By development of technology, the vacuum cleaners have been also improved in their subcategories. Today, many vacuum cleaners developed with new technologies have been substituted with old ones. For instance, bagless vacuum cleaners, water – filtered vacuum cleaners, robotic vacuum cleaners, etc. are the machines that have cutting – edge technologies. Nowadays, there are many electrical vacuum cleaners which are used in homes commonly. The bagless and bagged vacuum cleaners are the most commonly used vacuum cleaner types chosen by users. Although there are many advantages of bagged and bagless vacuum cleaners, they have plenty of disadvantages. While the bagged vacuum cleaners have many disadvantages such as changing the dust bag, dust leakage while changing the dust bag, bagless vacuum cleaners are advantageous in order not to have any dust bag and renewal cost of the dust bag. The bagless vacuum cleaners have been gaining popularity on the occasion of the advantages in the recent days. Due to the increasing popularity and complexity of working principles of bagless or cyclonic vacuum cleaners, determination of particle trajectories and collection efficiency of dustbin have been chosen as the topic of the thesis. By conducting experimental and numerical studies, the singular collection efficiency of a cyclonic vacuum cleaner dustbin has been determined and compared to the new designs. The thesis is composed of experimental and numerical analysis to determine the particle trajectories in a cyclonic vacuum cleaner dustbin and its collection efficiency without considering the effects of the filters. Experimental studies have been carried out by using dustbin, in particular. Numerical studies have been carried out by using a commercial code, Ansys Fluent and all the geometries that have been used in the study have been meshed by using Ansys ICEM – CFD tool. Before starting experimental and numerical studies, a deep literature research had been done to gain knowledge and understand the principles of the cyclones. In the literature research, many useful things had been found related to experimental and numerical studies. After the literature research had been done, the turbulent flow of the particles and turbulence models were examined. The turbulence and its governing equations have been explained in detail and the boundary layers arose from turbulence have been examined. A deep research about choosing turbulence models and their backgrounds have been conducted. Moreover, many types of research including the turbulence models which are used commonly in commercial codes have been done but some kind of models that are independent of mesh have not been taken into account because of not related with the thesis. In addition to literature researches about turbulence and its models, discrete phase modeling, which is the main part of the thesis, has also been investigated. The general theory of DPM, particle – wall treatment, turbulent dispersion of the particles and particle injection have been examined. The particles have been injected into the geometries, which have been designed newly, at the same speed rate of the inlet air flow velocity and flow rate. Because of the steady CFD analysis, the DPM analysis has also done as steady. The number of injected particles is proportional to the mesh size of the inlet surface and the particle trajectories have been determined. After determining the trajectories of the particles, the collection efficiency of the dustbin has been determined by DPM analysis. In order to conduct the numerical analysis, some parameters have to be defined. Because of this, the S7534 type cyclonic vacuum cleaner has been chosen for both experimental and numerical analysis. Firstly, a wide range of motors, starting the input power from 800 to 1600W, have been used to determine the air flow rate of the vacuum cleaner. After choosing nine vacuum cleaner motors, they have been tested in order to identify the air flow rates. Because of the complexity of the thesis, the number of the motors has been decreased to three. If the number of the motors, in other words, flow rates, there would have been too many data and numerical analysis including three different geometries. The flow rates of the motors are really very important for both experimental and numerical analysis. After determining each flow rates, a wind tunnel has been used to determine the pressure drop across the inlets and outlets of the filters and dustbin. These data have been used for numerical analysis of porous media in a dustbin. Furthermore, a high – speed camera has been used to determine the particle trajectories in real. The high – speed camera has recorded 13.5 seconds of particle motion in the dustbin which has had 4.5 GB file size. The final step of the experimental study is a determination of collection efficiency of the dustbin by using digital scales which has 0.01% precision. In the numerical analysis part of the thesis, plenty of studies has been carried out. Firstly, the flow area of the original dustbin geometry has been subtracted from the solid body by using a 3D modeling software, Siemens NX 9.0. After that, new simple geometries have been designed by considering the original one. Before starting the numerical analysis for the original dustbin geometry, a mesh independence study had been conducted in order to shorten the computational time and effort. By doing this study, the appropriate mesh type and size has been identified and applied to the other geometries. In order to obtain a reliable result from the numerical analysis, the coefficients of the porous media have to be determined. To find these coefficients, the experimental data have been used. After identifying these values, CFD analysis has been done for each geometry. To find the particle trajectories and collection efficiencies of each geometry, DPM analysis has been conducted. However, to apply DPM analysis some coefficients have to be determined. To determine these values, some calculations have been done using Excel. These coefficients are named as spread parameter and mean particle diameter. After this study, all coefficients have been determined and DPM analysis for each geometry on each flow rates have been conducted and collection efficiencies have been calculated numerically. In the final step of the thesis, numerical results have been compared to experimental values and have been matched accurately.