Volume 17, Issue 3 (2017)                   Modares Mechanical Engineering 2017, 17(3): 19-30 | Back to browse issues page

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Faghih Aliabadi M A, Mahpeykar M R. Comparison between polydispersed and monodispersed models on condensing water-vapor flow in a supersonic convergent-divergent nozzle. Modares Mechanical Engineering. 2017; 17 (3) :19-30
URL: http://journals.modares.ac.ir/article-15-9609-en.html
1- Department of Mechanical Engineering, ّّّFerdowsi University of Mashhad
2- Professor- FUM
Abstract:   (1581 Views)
The supercooled steam in low pressure turbines creates the nucleation phenomenon. In most modeling approaches, to reduce the computation time a monodispersed model is used. However, experimental evidence even on one dimensional condensing flow demonstrates the existence of droplets with several sizes. In this paper to develop the modeling of the droplets more realistic, a polydispersed model is used along with the one dimensional HHL Riemann solver. In this study, a simple method is proposed for polydispersed model in Eulerian-Eulerian method. In this scheme, first, a number of elements are considered in the nucleation region and the droplets formed in each of the elements are put into a group. Then the new droplets formed in consecutive elements are distributed based on the ratio between the number of droplets in each group available for merging constrained by having the same number of groups. These groups grow individually until the end of the nozzle and each group has their own wetness, temperature, number of droplets and radius. Based on the results of the proposed polydispersed, the nucleation rate and the number of droplets are found to be more than the results of the monodispersed model, but the average droplet radius is less, with 10% differences is closer to the empirical radius of the Moore nozzle. The pressure distributions for both models have good agreement with experimental data, but in overall, the results of the proposed polydispersed method is significantly closer to experimental results especially with regards to the droplet radius.
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Article Type: Research Article | Subject: Two & Multi Phase Flow
Received: 2016/12/7 | Accepted: 2017/01/30 | Published: 2017/02/27

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