Kabelbrandssimulering i Fire Dynamics Simulator (FDS) med lagrangianska partiklar
Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
For this project it has been studied if cable fires can be simulated in the Fire Dynamics Simulator (FDS) with the use of the sub-model Lagrangian particles. A full scale test from the cable fire research project called Cable Heat Release, Ignition and spread in Tray Installations During Fire (CHRISTIFIRE) has been used as a reference for the simulations (U.S.NRC. 2013. CHRISTIFIRE (NUREG/CR-7010), vol. 2). This test consisted of a 7.3 m long, 2.3 m wide and 2.4 m high corridor with three levels of cable trays along one of the walls. The cables were ignited with a 40 kW propane burner which was placed 40 cm from the entrance and 20 cm beneath the lowest cable tray.The corridor test from CHRISTIFIRE was modelled in FDS and the cables were constructed of Lagrangian particles with properties from the cable used during the actual corridor-test. A simplified flame spread-model was used in which each cable was given a heat release rate per unit area (HRRPUA), an ignition temperature and a burn time. The ignition temperature was taken from small scale tests with a pyrolysis combustion flow calorimeter (PCFC) which were conducted as a part of CHRISTIFIRE. The HRRPUA was taken from bench scale cone calorimetry studies of the same cable which was also done in CHRISTIFIRE. The burn time was calculated by hand with the use of data from these tests and information about the amount of combustible material on the cable. Three different ways of modelling the cable particles was tested in order to determine which gave the most realistic result.Sensitivity analyses were made with respect to the parameters HRRPUA, burn time, ignition temperature and grid size. In order to evaluate the results from the simulations, they were compared against the HRR-curve from the full scale test and the αt2-fires which are presented in Boverkets allmänna råd om analytisk dimensionering av byggnaders brandskydd (BBRAD3). The αt2-fires are to be used when analytically verifying the construction regulations defined by Boverket. However they are commonly used as a general way to model the fire in FDS simulations since they are considered tested. For the type of cable fires studied in this project however, the αt2-fires present a very conservative HRR-curve, both in growth and in maximum HRR. If the fire is too conservative, the whole simulation and the succeeding analysis is in danger of losing its credibility.The results from this project shows that in the particular case which was studied, the model with Lagrangian particles present a HRR-curve which is very similar to the original one from U.S.NRC’s full scale test and much more accurate than the αt2-fires.
Place, publisher, year, edition, pages
2016. , 58 p.
Teknik, Fire dynamics simulator, FDS, kabelbrand, kabelbränder, Lagrangian particles, lagrangianska partiklar, kabelbrandssimulering, CHRISTIFIRE
IdentifiersURN: urn:nbn:se:ltu:diva-44630Local ID: 266c9d72-dd8e-4074-96f4-3e73eef6ec27OAI: oai:DiVA.org:ltu-44630DiVA: diva2:1017909
Subject / course
Student thesis, at least 15 credits
Fire Protection Engineer, bachelor's level
Validerat; 20160110 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved