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Study of divergence angle influence for sonic nozzle in non-equilibrium condensation
Balasubramanian Dhandapani,이장창 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6
The condensation happens generally in a nozzle during expansion of compressed steam from convergent to the divergent part of the nozzle. The divergence angle is the angle measured from the throat of the nozzle to the outlet. In this paper, the outlet is kept constant and the throat diameter is varied. In turn, the divergence angle of the sonic nozzle is altered. The effect of divergence angle on condensation phenomena is investigated with wet steam in a sonic nozzle. For analyzing the wet steam properties, the non-equilibrium condensation model is used. This model is the classical nucleation theory coupled with the droplet growth rate equation. The base nozzle is designed with the throat diameter of 4.5 mm and other dimensions are calculated according to ASME nozzle formulas. Furthermore, the chosen divergence angles are 3°, 4.2°, and 6° for which the throat diameters are 4.5 mm, 3 mm, and 1.5 mm, respectively. As the divergence angle is gradually increased, the position of maximum Mach number of the flow moves upstream, the static temperature of the flow near the throat reaches the lower value, and the droplet nucleation rate is increased. The condensation shock gets gradually stronger with decreasing the divergence angle.
EFFECT OF NON-EQUILIBRIUM CONDENSATION OF WET STEAM IN THE MODIFIED SONIC NOZZLE
Balasubramanian Dhandapani,Jang-Chang Lee(이장창) 한국전산유체공학회 2020 한국전산유체공학회지 Vol.25 No.4
The non-equilibrium condensation effects of steam in the modified sonic nozzle are investigated. The modified sonic nozzle in this paper is based on the sonic nozzle of ASME where the flow velocity reaches Mach number one at the throat and where the pressure ratio of inlet/outlet(P1/P3) is operated with greater than two to achieve sonic state. As the superheated dry steam accelerates through the nozzle, the condensation of steam occurs and then the steam becomes the wet steam which is two phases mixture with saturated vapor and liquid droplets. The numerical modeling of the non-equilibrium condensation in the modified sonic nozzle is obtained by solving two transport equations based on the classical nucleation theory with the droplet growth law of Hill. The numerical results show that the Mach number reaches 1.2 immediately after throat, the droplet nucleation rate increases rapidly with increasing subcooling level(ΔT), and the liquid mass fraction increases gradually downstream of nozzle. Also the condensation effects in the modified sonic nozzle is compared internally with its different thermal choking ratio’s and with dry steam cases for better realization of the modified sonic nozzle.