Progress in the development of the steam turbines brings about a renewal of interest in wetness associated problems. In turbine steam expansion, the vapour first supercools and then condenses spontaneously to become a two phase mixture. The flow initially is single phase but after Wilson point water droplets are developed and there is a non equilibrium two phase flow. The formation and behavior of the liquid create problems that lower the performance of the turbine wet stage and the mechanisms underlying this are insufficiently understood. This growing droplets release their latent heat to the flow and this heat addition to the supersonic flow cause a pressure rise called condensation shock. Because of irreversible heat transfer in this region the entropy will increase tremendously. Removal of condensates from wet steam flow in the last stage of steam turbines significantly promotes stage efficiency and prevents erosion of rotors. The following study investigates the spraying water droplets at inlet and at throat of mini Laval nozzle and their effects on nucleation rate and condensation shock. According to the results, the nucleation rate is considerably suppressed and therefore the condensation shock nearly disappeared. In other words the injecting droplets would decrease the thermodynamic losses or improve the turbine efficiency.
- Nanotechnology Institute
The Effects of Water Injections in Wet Steam Flow in Different Regions of a Mini Laval Nozzle
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Mahpeykar, MR, Amirirad, E, & Lakzian, E. "The Effects of Water Injections in Wet Steam Flow in Different Regions of a Mini Laval Nozzle." Proceedings of the ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. ASME 2008 6th International Conference on Nanochannels, Microchannels, and Minichannels. Darmstadt, Germany. June 23–25, 2008. pp. 355-361. ASME. https://doi.org/10.1115/ICNMM2008-62252
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