Non-equilibrium Evaporation and Condensation Processes

2021 ◽  
Author(s):  
Yuri B. Zudin
Keyword(s):  
Evaporation And Condensation ◽  
Equilibrium Evaporation ◽  
Non Equilibrium

Numerical Analysis of Spray Dispersion, Evaporation and Combustion in a Single Gas Turbine Combustor

2008 ◽  
Author(s):  
M. Chrigui ◽  
A. Sadiki ◽  
J. Janicka
Keyword(s):  
Reynolds Stress ◽  
Mixture Fraction ◽  
Measurement Techniques ◽  
Reynolds Stress Model ◽  
Scalar Dissipation ◽  
Stress Model ◽  
Vapor Source ◽  
Flamelet Model ◽  
Equilibrium Evaporation ◽  
Non Equilibrium

Spray dispersion, evaporation and combustion have been numerically studied in a complex industrial configuration, which consists in a single annular combustor that was experimentally measured by Rolls-Royce-Deutschland Company. Simulations have been achieved using the Eulerian-Lagrangian approach. The computations of the continuous phase have been performed by means of RANS simulations. Though the k-ε as well as the Reynolds Stress model (Jones-Musonge) have been used for turbulence modeling. The 3D-computations have been performed in a fully two-way coupling. The effects of turbulence on droplets distribution are accounted for using the Markov sequence dispersion model. The equilibrium as well as the non-equilibrium evaporation model have been applied. In order to account for the combustion, the diffusion flame model is chosen. It relies on the computation of the mixture fraction that has been affected by the presence of vapor source terms. For the interaction of the turbulence with the chemistry, the mixture fraction variance has also been solved. For that purpose a presumed beta-PDF function has been considered. The equilibrium and the flamelet chemistry approaches have been used for the generation of the chemistry tables. The performed simulations have also been compared to commercial CFD-codes. From there one observes, that the obtained results using the mentioned sub-models combination agree most favorably with experimental measurements. One noted that the Reynolds Stress model provided smoother temperature distribution compared to k-ε. The flamelet model has been performed using three different scalar dissipation rates. One observes that differences are mainly located at the nozzle exit, where the scalar dissipation rate has got the highest value. Although the comparison between the numerical results and the experimental data was possible only at the combustor exit, due to the limitation on the measurement techniques, one can reiterate that the combination of the following sub-models: thermodynamically consistent model for the turbulence modulation, Langmuir-Knudsen non-equilibrium model for the evaporation, Reynolds Stress Model for the turbulence and flamelet model for the chemistry establish a reliable complete model that seems to allows a better description of reactive multi-phase flow studied in the frame of this work.

scholarly journals Spectroscopic detection of coronal plasma flows in loops undergoing thermal non-equilibrium cycles

2020 ◽  
Vol 634 ◽  
pp. A54 ◽  
Author(s):  
Gabriel Pelouze ◽  
Frédéric Auchère ◽  
Karine Bocchialini ◽  
Clara Froment ◽  
Susanna Parenti ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Line Of Sight ◽  
Doppler Velocity ◽  
Temperature Plasma ◽  
Imaging Spectrometer ◽  
Periodic Flows ◽  
Evaporation And Condensation ◽  
Spatially Resolved ◽  
Euv Imaging ◽  
Non Equilibrium

Context. Long-period intensity pulsations were recently detected in the EUV emission of coronal loops and attributed to cycles of plasma evaporation and condensation driven by thermal non-equilibrium (TNE). Numerical simulations that reproduce this phenomenon also predict the formation of periodic flows of plasma at coronal temperatures along some of the pulsating loops. Aims. We aim to detect these predicted flows of coronal-temperature plasma in pulsating loops. Methods. We used time series of spatially resolved spectra from the EUV imaging spectrometer (EIS) onboard Hinode and tracked the evolution of the Doppler velocity in loops in which intensity pulsations have previously been detected in images of SDO/AIA. Results. We measured signatures of flows that are compatible with the simulations but only for a fraction of the observed events. We demonstrate that this low detection rate can be explained by line of sight ambiguities combined with instrumental limitations, such as low signal-to-noise ratio or insufficient cadence.

Fluid Properties at Gas Turbine Inlet due to Fogging Considering Evaporation and Condensation Phenomena as Well as Icing Risk

2014 ◽  
Author(s):  
Christoph Günther ◽  
Franz Joos
Keyword(s):  
Relative Humidity ◽  
Gas Turbine ◽  
Ambient Air ◽  
Equilibrium Conditions ◽  
Evaporation And Condensation ◽  
The Third ◽  
Ambient Relative Humidity ◽  
Fluid Properties ◽  
Gas Turbine Compressor ◽  
Non Equilibrium

This study reports on numerically calculated thermophysical properties of air entering a gas turbine compressor after passing through an intake duct affected by different cooling techniques. Case of reference is unaffected ambient air (referenced to as unaffected) passing the intake duct. Furthermore ambient air cooled down to wet bulb temperature by (overspray) fogging (referenced to as wet) was considered. The third case shows air cooled down to the same temperature as it was reached in the wet case but by using chillers (referenced to as chilled). Equilibrium and non-equilibrium properties according to the occurring evaporation and condensation phenomena were compared. Equilibrium conditions seems to have a reduced inlet icing risk for the wet case compared to the chilled case. However comparing the wet case to the unaffected case showed a higher icing risk for the wet case at low ambient relative humidity. In contrast to equilibrium conditions a consideration of non-equilibrium conditions resulted in an increased icing risk due to almost negligible condensation rates.

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