Experimental Study of Dispersed Droplets in High-Pressure Annular Flows

1999 ◽  
Vol 121 (4) ◽  
pp. 924-933 ◽  
Author(s):  
T. A. Trabold ◽  
R. Kumar ◽  
P. F. Vassallo
Keyword(s):  
Void Fraction ◽  
High Pressures ◽  
Liquid Droplet ◽  
Droplet Velocity ◽  
Laser Doppler Velocimeter ◽  
Two Phase ◽  
R 134A ◽  
Gamma Densitometer ◽  
Density Ratios ◽  
Hot Film

Local measurements were made in a droplet-laden vapor core in upward R-134a annular flow in a high aspect ratio vertical duct. These detailed measurements are unique in that they were performed at high pressures and low liquid-to-vapor density ratios. Using a gamma densitometer, hot-film anemometer and laser Doppler velocimeter, profiles of void fraction, liquid droplet frequency, and droplet velocity were acquired across the narrow test section dimension. At relatively high flows, the measured void fraction was highest near the wall, due to the thinning of the liquid film. The dip in the void fraction in the vapor core at these flows suggests significant droplet entrainment. The entrainment fractions for these refrigerant flows fall in the range measured for pressurized steam-water systems. The average drop size, calculated from direct measurements of void fraction, droplet velocity, and frequency, compares favorably with previous experimental results from the literature. These data are useful for developing an improved understanding of practical two-phase flows, and for assessment of advanced two-fluid computer codes.

scholarly journals Application of Advanced Diagnostics to Airblast Injector Flows

1989 ◽  
Vol 111 (1) ◽  
pp. 53-62 ◽  
Author(s):  
J. B. McVey ◽  
J. B. Kennedy ◽  
S. Russell
Keyword(s):  
Flux Distribution ◽  
Liquid Droplet ◽  
Laser Doppler Velocimeter ◽  
Fuel Injector ◽  
Two Phase ◽  
Turbine Engine ◽  
Design Procedures ◽  
Phase Doppler Anemometer ◽  
Injector Flows ◽  
Component Phase

Experimental data on the characteristics of the spray produced by a gas turbine engine airblast fuel injector are reported. The data acquired include the mass-flux distribution, measured by use of a high-resolution spray patternator; the gas-phase velocity field, measured by use of a two-component laser-Doppler velocimeter; and the liquid droplet size and velocity distributions, measured by use of a single-component phase-Doppler anemometer. The data are intended for use in assessments of two-phase flow computational methods as applied to combustor design procedures.

Experiments and Modeling in Bubbly Flows at Elevated Pressures

2003 ◽  
Author(s):  
R. Kumar ◽  
T. A. Trabold ◽  
C. C. Maneri
Keyword(s):  
Void Fraction ◽  
Bubble Size ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Bubbly Flows ◽  
Rise Velocity ◽  
Two Phase ◽  
Flow Models ◽  
Gamma Densitometer ◽  
Visualization Techniques

Measurements of local void fraction, rise velocity and bubble diameter have been obtained for cocurrent, wall-heated, upward bubbly flows in a pressurized refrigerant. The instrumentation used was the gamma densitometer and the hot-film anemometer. Departure bubble size and bulk size measurements were also made and correlated with appropriate parameters. Flow visualization techniques have also been used to understand the two-phase flow structure and the behavior of the bubbly flow for different bubble shapes and sizes, and to obtain the rise velocity. Such insight, coupled with quantitative local and averaged data on void fraction and bubble size at different pressures, has aided in developing bubbly flow models applicable to heated two-phase flows at high pressure.

High Pressure Annular Two-Phase Flow in a Narrow Duct: Part II—Three-Field Modeling

2000 ◽  
Vol 122 (2) ◽  
pp. 375-384 ◽  
Author(s):  
Ranganathan Kumar ◽  
Thomas A. Trabold
Keyword(s):  
High Pressure ◽  
Void Fraction ◽  
Annular Flow ◽  
Predictive Capability ◽  
Two Phase ◽  
Modeling Approach ◽  
Field Modeling ◽  
Hot Film ◽  
Vertical Duct ◽  
Narrow Duct

This paper outlines the development of a three-field modeling approach in annular flow and the predictive capability of an analysis code. Models have been developed here or adapted from the literature for the thin film near the wall as well as the droplets in the vapor core, and have been locally applied in a fully developed, two-phase adiabatic boiling annular flow in a duct heated at the inlet at high pressure. Numerical results have been obtained using these models that are required for the closure of the continuity and momentum equations. The two-dimensional predictions are compared with local void fraction and droplet velocity (using a hot film anemometer), and average void fraction (using gamma densitometry) for a refrigerant fluid flowing in a narrow vertical duct with a cross-section aspect ratio of 22.5. Predicted results match the experimental data well for high void fraction annular flows, validating the overall modeling approach. [S0098-2202(00)01002-6]

The Radial Migration of Bubbles in Two-Phase Bubbly Flow in Vertical Pipes

2006 ◽  
Author(s):  
Mohamed E. Shawkat ◽  
Chan Y. Ching ◽  
Mamdouh Shoukri
Keyword(s):  
Void Fraction ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Optical Probe ◽  
Superficial Velocity ◽  
Turbulent Dispersion ◽  
Two Phase ◽  
Two Fluid Model ◽  
Hot Film ◽  
Two Fluid

The radial distribution of bubbles in air-water bubbly flow was experimentally investigated using a dual optical probe and hot-film anemometry. The experiments were performed in a 200mm diameter vertical pipe at liquid superficial velocity in the range of 0.2 to 0.68m/s and gas superficial velocity from 0.005 to 0.18m/s. At low void fraction flows, the radial void fraction profiles show a wall peak. As the void fraction increases the profiles tend to peak at the pipe centreline. The distribution of the net radial interfacial forces for both core and wall peak void distributions was obtained using the two-fluid model. The radial direction of the bubble migration in the pipe core was related to the ratio between the turbulent dispersion and the lift forces. The effect of the pipe diameter on this ratio was investigated.

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