Research on the Installation Location of the Vortex Probe for Gas-liquid Two-phase Flow with Low Liquid Fraction

Massive droplets can be generated to form two-phase flow in steam turbines, leading to erosion issues to the blades and reduces the reliability of the components. A condensing two-phase flow model was developed to assess the flow structure and loss considering the nonequilibrium condensation phenomenon due to the high expansion behaviour in the transonic flow in linear blade cascades. A novel dehumidification strategy was proposed by introducing turbulent disturbances on the suction side. The results show that the Wilson point of the nonequilibrium condensation process was delayed by increasing the inlet superheated level at the entrance of the blade cascade. With an increase in the inlet superheated level of 25 K, the liquid fraction and condensation loss significantly reduced by 79% and 73%, respectively. The newly designed turbine blades not only remarkably kept the liquid phase region away from the blade walls but also significantly reduced 28.1% averaged liquid fraction and 47.5% condensation loss compared to the original geometry. The results provide an insight to understand the formation and evaporation of the condensed droplets inside steam turbines.

Download Full-text

Prediction of the entrained liquid fraction in vertical annular gas–liquid two-phase flow

International Journal of Multiphase Flow ◽

10.1016/j.ijmultiphaseflow.2009.11.011 ◽

2010 ◽

Vol 36 (4) ◽

pp. 293-302 ◽

Cited By ~ 37

Author(s):

Andrea Cioncolini ◽

John R. Thome

Keyword(s):

Two Phase Flow ◽

Liquid Fraction ◽

Phase Flow ◽

Two Phase

Download Full-text

Gas-Liquid Two-Phase Flow in Hot Embossed Square Microchannels

Volume 11: Micro and Nano Systems, Parts A and B ◽

10.1115/imece2007-42158 ◽

2007 ◽

Author(s):

Namwon Kim ◽

Estelle T. Evans ◽

Daniel S. Park ◽

Dimitris E. Nikitopoulos ◽

Steven A. Soper ◽

...

Keyword(s):

Weber Number ◽

Gas Flow ◽

Two Phase Flow ◽

Liquid Fraction ◽

Scaling Law ◽

Phase Flow ◽

Two Phase ◽

Flow Rates ◽

Homogeneous Liquid ◽

Bubble Length

An experimental study was conducted to investigate the characteristics of gas-liquid two-phase flow in 200 μm square microchannels thermoformed in polymer chips. Polymer microfluidic chips were replicated using hot embossing of poly(methyl methacrylate) (PMMA) with micromachined brass mold inserts. The thermoformed microchannels in polymer chips typically had greater surface roughnesses compared to microchannels etched in the silicon substrate. Two more different polymer chips, a direct micromachined PMMA chip and a chip hot embossed with a LIGA nickel mold insert, were fabricated to compare surface characteristics of the sidewalls and bottoms of fabricated microchannels. Deionized water and dry air were injected separately into the chips at superficial velocities of jL = 0.005 – 0.11 m/s for the liquid and jG = 0.003 – 16.67 m/s for the gas. Capillary bubbly, plug, plug-annular, annular, and dry flows were observed in the microchannels. Two-phase flow pattern maps and transitions between flow regimes were determined for fixed values of the homogeneous liquid fraction defined as βL = QL/(QL + QG) where QL and QG are the liquid and gas flow rates, and the liquid Weber number fraction defined as γL = WeL/(WeL + WeG) where WeL and WeG are the liquid and gas Weber number. The surface roughness in submicron range showed minor effect in comparison with the previous work in terms of the gas-liquid two-phase flow patterns and transitions between flow regimes. Dimensionless bubble sizes scaled by the width of observation microchannel were plotted against the homogeneous liquid fraction (βL). A scaling law for the bubble length developed for the previous work with T-junctions was applicable to the present work used the cross junction for generation of segmented flow. With a fixed value of the fitting parameter, scaling law showed a good agreement with the experimental data. Deviation of the scaled bubble length from predicted bubble length line and irregularity of bubble length with a fixed homogeneous liquid fraction increased with higher gas flow rates.

Download Full-text