Experimental comparison of slalom concepts
Pirttikangas, Ella (2018)
Pirttikangas, Ella
Åbo Akademi
2018
Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2018102938981
https://urn.fi/URN:NBN:fi-fe2018102938981
Tiivistelmä
Studies on paper and board machine runnability began in the late 20th century and most of the studies focused on machine speed increase. Today, the most high-speed paper machines have a single-run construction and machine speeds can reach speeds over 2000 m/min. Runnability equipment is developed to enable the high velocities and the objective is to diminish the negative effects associated with the machine speed increase. Currently, studies focus on energy and cost efficiency, where finding the optimum solution for the certain framework is required.
The objective of the thesis was to study the forces and the phenomena at a single-run paper or board machine, which causes harmful effects on the web. In the thesis, a selection of runnability concepts are compared at different machine speeds and the comparison analyses their functionality, energy consumption and cost. The concepts were tested at pilot scale in the Technology Centre of Valmet in Raisio.
The comparison of the functionality focused on how the different concepts stabilised the web at the closing nip and over the rotation of the bottom cylinder. The comparison concluded that the existence of a surface pattern was beneficial both for the closing nip over pressures as well as the support over the rotation. Furthermore, having a stabiliser nozzle targeting the closing nip was useful especially at low machine speeds and the suction roll concepts were found to be over dimensioned at machine speeds below 1400 m/min.
The energy consumption and cost evaluation, combined with the functionality analysis suggests that the concepts using a suction roll are the most fitting for higher velocities, as the functionality of the concepts with the passive bottom rolls decrease or the operational cost become higher compared to the suction roll concepts.
The objective of the thesis was to study the forces and the phenomena at a single-run paper or board machine, which causes harmful effects on the web. In the thesis, a selection of runnability concepts are compared at different machine speeds and the comparison analyses their functionality, energy consumption and cost. The concepts were tested at pilot scale in the Technology Centre of Valmet in Raisio.
The comparison of the functionality focused on how the different concepts stabilised the web at the closing nip and over the rotation of the bottom cylinder. The comparison concluded that the existence of a surface pattern was beneficial both for the closing nip over pressures as well as the support over the rotation. Furthermore, having a stabiliser nozzle targeting the closing nip was useful especially at low machine speeds and the suction roll concepts were found to be over dimensioned at machine speeds below 1400 m/min.
The energy consumption and cost evaluation, combined with the functionality analysis suggests that the concepts using a suction roll are the most fitting for higher velocities, as the functionality of the concepts with the passive bottom rolls decrease or the operational cost become higher compared to the suction roll concepts.