Besides the know-how and experience existing in HAVER & BOECKER OHG, the GeoDict software from Math2Market GmbH is intensively used to determine which wire cloth configuration suits the best for the specific field of application. By simulating different cases, it is possible to optimize existing wire cloth specifications and develop new ones.
Geometrical characteristics such as type of weave, wire diameter and mesh counts have an enormous impact on the specific flow and filtration properties of a wire cloth. Using specific cloth parameters resulting from the type of weave, aperture width, pitch and wire diameter, HAVER & BOECKER can depict the structure of single-layer and multiple-layer cloths as a real 3D model (Fig. 1) using GeoDict. Geometric parameters such as the pore size distribution and bubble point are then determined with the PoroDict module of GeoDict. The behaviour of the respective cloth or cloth laminate in various fluids such as air, water and fuel as a function of flow rate or differential pressure is predicted by the FlowDict module.
The simulation of the calibration process is demonstrated here by digitally compressing the media. The wire diameter, pore sizes and the permeability of the structure are changed by calibration. The simulations predict the difference of these properties before and after the calibration process.
Moreover, filtration experiments are carried out at the IUTA in Duisburg using the single-pass filtration test rig MFP 1000 from Palas GmbH. The tests use ISO A2 fine test dust particles. For finding the pressure drop of the clean media, the samples are measured only under air flow, i.e. without injection of dust particles. Afterwards, the particles are injected with the air flow. For defining the standard deviation, the particle size distribution in the air was measured four times in the upstream flow and three times in the downstream flow of the filter media. In other words, three samples for each kind of filter media were used in the experiments to ensure the confidence in the accuracy of the results. The filtration tests are conducted for roughly 75 seconds. The accuracy of this filtration time may vary due to the time the user needs to adjust the sample and later to take the sample out of the apparatus.
The filtration of solid particles from the fluid is also simulated. Filter life-time simulations were carried out using single-pass filtration parameters, i.e. with a constant contaminant concentration. The simulated quantities are the pressure drop, filter efficiency and count/mass of the deposited solid particles as a function of time. Furthermore, the deposited volume of particles and the pressure drop are animated as a function of time. In these simulations, the solid particles are spherical. Simulations are done by HAVER & BOECKER and in consultation with Math2Market. One of the challenges is to find out a precise distribution for the restitution coefficient of different particle sizes when impacting the surface. As restitution coefficient is a function of material properties, impact velocity and angle, particle size and shape, it can have a considerable effect on the filtration results when considering it in the collision models.
The results, namely the filter efficiency and pressure drop, obtained from the simulations are compared and validated with the experimental data. Using the proposed modeling and simulation technique, it is possible to predict the flow and filtration behavior of woven media and to optimize the micro-structure which suits the best for the specific applications...
Session: G15 - Filter Medium Design
Day: 24 October 2019
Time: 10:45 - 12:00 h