Abstract
This study aims to analyze the influence of different turbulence models in capturing the flow profile in supersonic nozzles as ones used in steam jet ejectors. Based on the recent experiments by T. Sriveerakul.; S. Aphornratana.; K. Chunnanond (International Journal of Thermal Sciences 46 (2007) 812-822) computations were performed using three different turbulence models, a modified RANS model (SST k-ω), a URANS model with Scale Adaptative S imulation - SAS and the large eddy simulation (LES), with three different steam jet operational conditions, the simulation results were compared with experimental data. First, SAS and SST k-ω computations were performed with three meshes with different refinement level on a mesh independency study. It was observed that SAS model was more sensitive with mesh refinement. In less refined mesh the pressure profile obtained was very close to SST k-ω results indicating that mesh refinement and time st ep weren't enough to activate the source term included in ω. With two other meshes a SAS convergence was o bserved while these meshes are refined enough to use LES. LES time average values of the variables under study on the most refined mesh were included in the comparison. Furthermore Mach number plots along the equipment center line showed the shock waves formation and the pressure profile recuperation that occurs in the diffuser. The RANS SST k-ω turbulence model results showed the smallest errors related to the experimental data.
Highlights
Temperature (°C) Pressure (Pa) Temperature(°C) Pressure (Pa). In these three cases was assumed the pressure of 3000 Pa as the back pressure and a pressure profile was obtained along the steam ejector wall to compare with experimental data
A grid resolution study with SST k-ω and SAS model will be discussed followed by a comparison between these models against large eddy simulation (LES) model
The ejector behavior was studied with three different turbulence models, SST k - ω, SAS and LES
Summary
A pressurized fluid flow through the convergent part, the throat and the divergent portion and is exhausted in an ambient as a jet. In this process the fluid reaches supersonic velocities. There are many applications of supersonic nozzles as turbines, dispersers and steam jet ejectors, the latter will be the objective of the present study. These equipments are mechanical components, which allow performing the mixing and/or the recompression of two fluids streams. The fluid with higher total energy is the motive or primary fluid, while the other is the secondary or induced fluid
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