No abstract

Baking treatment is one of the most important processes of cigarette production, which can significantly enhance quality of tobacco. Theoretical and numerical investigation on temperature distribution in a cigarette oven during baking was carried out. The finite volume method was used to simulate the flow field. The relationship between the uniformity of temperature field and impeller?s speed was given finally, which is helpful to optimize cigarette oven with better quality and less energy consumption.

Standard bar of ventilation is the equipment extensively used in the tobacco industry to calibrate the variety of testing machines. The bar?s performance that is usually affected by ambient conditions is numerically studied in this paper. Firstly, the geometry of standard bar is obtained by an optical microscopic 3-D measurement. Then, Solidworks is used to build the 3-D model of standard bar and Gambit is used to mesh the model. Finally, the performance of standard bar under variant ambient conditions is analyzed by Fluent. Compared with the experimental data, the numerical results are found to be quite accurate, and it is found that the ventilation rate increases linearly as temperature rise and decreases non-linearly with the growth of pressure.

Obstructive sleep apnea (OSA) is a common disorder which may need to be treated by the upper respiratory tract (URT) surgery. To increase the success rate of the URT surgery, it is crucial to understand the flow features in the URT models. In this work, the turbulent flow characteristics in four 3D anatomically accurate URT models reconstructed from two OSA subjects with successful and failed surgery are numerically studied by the large-eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS). The features of velocity fields, pressure fields, and wall shear stress fields as well as the spectral analysis of wall shear stress between successful and failed surgery are explored. The results indicate that LES is capable of capturing flow patterns and flow oscillation and is effective for OSA surgery prediction. Even if the unsteady RANS can obtain the correct pressure drop across the airways, it may not be appropriate to be used for surgery prediction. Moreover, it is found that the quality of oscillating signal of wall shear stress is a key factor in surgery prediction. In a successful surgery, the wall shear stress oscillation is always strong, and the oscillating signal can perform a dominant frequency near 3~5 Hz, while in a failed surgery it does not show this clear intrinsic property. The results not only will gain new insights in the URT surgical planning but also will improve the prediction of surgical outcome for OSA patients.