For reasons of health protection and functional safety, finely dispersed oil particles have to be separated from gases, mostly from the air, at many workplaces. Special oil filters, also known as coalescence filters, are used for this purpose. There are two main application scenarios: On the one hand, the separation of oil mist and oil-containing emulsion mist from air or other gases at ambient pressure, and on the other hand, the preparation of compressed air. The problem with these so-called coalescence filters is the high pressure loss, which is associated with increased energy consumption, and a reduced degree of separation.
The aim of the BiGOFil project is to develop an oil mist filter that increases the degree of separation with a lower pressure loss. To increase oil separation, non-round, profiled bicomponent fibers with oil ducts are being developed. A fleece is produced from these, which is used as a filter medium in the newly developed coalescence filter. Simulations of the fiber production process and the filtration process on the micro and macro scale are being developed in parallel to the development of the filter. At the end of the project, a prototype of a new type of coalescence filter is available. In addition to the filter as a product, an extension of the GeoDict simulation software for the simulation of filters, which is sold as a product, is being developed within the project.
At the Institute for Flow in Additively Manufactured Porous Media (ISAPS) at HHN, models and simulations of the coalescence of oil droplets on the microscale are carried through, in which the individual fibers and the oil droplets are resolved. Since only the smallest sections of a filter can be considered on the microscale due to the small size of oil droplets and the small fiber diameter, we will develop an oil source term that accounts for the deposition of the oil droplets on the new fibers. This is included in a flow simulation on the filter scale, in which the complete filter (including possibly several different filter layers) can be described.
The micro- and macro-scale flow models are validated by measuring the pressure loss and fraction separation efficiency on our oil mist test bench for both the new filter material and the new filter. The validated models are used to optimize the filter material on the microscale and the filter structure (possible sequence of several filter layers and the shape of the filter) on the macro scale. The tests on the test bench not only serve to validate the model, but are also required for the technical evaluation and iterative improvement of the filter.