Improved Solids Conveying Model for Single Screw Extruders

In the proposed project an improved solids conveying model for single screw extruders regarding the relevant material properties will be developed. For the determination of the beginning of the following zone the most exact pressure- and temperature calculations are necessary. In this case the existing solids conveying models still show relative significant deficiences. The reason is that the existing solids conveying models assume constant pressure anisotropy coefficients and in most of the cases constant internal and external coefficients of friction. As a matter of fact the pressure anisotropy coefficients are a function of the pressure and temperature, the coefficients of friction in addition are a function of velocity. The majority of solids conveying models assume plug flow, this is obviously not always the case, especially in the case of greater channel depths. The pressure build-up perpendicular to the screw flights is incorrectly considered linearly. The shearing conditions at the inner barrel surface of grooved feed zones are described not in all cases exactly. Based on new knowledge the modelling of the solids conveying zone will be improved for smooth as well as grooved feed zones. The necessary coefficients of friction will be measured with the new developed shearing apparatus at common pressures in the extruder technique. This shearing apparatus matches the working principles of a vertical arranged solids conveying extruder. The pressure anisotropy coefficients will be measured with an existing testing apparatus. The calculation results will be compared with the experiments of the solids conveying extruder. The pressure profiles in the solids conveying zone can be exactly measured with the help of a special pressure measuring technique. With interchangeable cylinder inserts various smooth as well as grooved inner barrel surfaces can be investigated. Furthermore, the interaction of the solids conveying zone with the following zones is considered.

In the proposed project an improved solids conveying model for single screw extruders regarding the relevant material properties will be developed. For the determination of the beginning of the following zone the most exact pressure- and temperature calculations are necessary. In this case the existing solids conveying models still show relative significant deficiences. The reason is that the existing solids conveying models assume constant pressure anisotropy coefficients and in most of the cases constant internal and external coefficients of friction. As a matter of fact the pressure anisotropy coefficients are a function of the pressure and temperature, the coefficients of friction in addition are a function of velocity. The majority of solids conveying models assume plug flow, this is obviously not always the case, especially in the case of greater channel depths. The pressure build-up perpendicular to the screw flights is incorrectly considered linearly. The shearing conditions at the inner barrel surface of grooved feed zones are described not in all cases exactly. Based on new knowledge the modelling of the solids conveying zone will be improved for smooth as well as grooved feed zones. The necessary coefficients of friction will be measured with the new developed shearing apparatus at common pressures in the extruder technique. This shearing apparatus matches the working principles of a vertical arranged solids conveying extruder. The pressure anisotropy coefficients will be measured with an existing testing apparatus. The calculation results will be compared with the experiments of the solids conveying extruder. The pressure profiles in the solids conveying zone can be exactly measured with the help of a special pressure measuring technique. With interchangeable cylinder inserts various smooth as well as grooved inner barrel surfaces can be investigated. Furthermore, the interaction of the solids conveying zone with the following zones is considered.