Unsteady two-phase flow instrumentation and measurement
The performance of a transverse field electromagnetic flowmeter in a steady two-phase flow was investigated analytically for a disperse and an annular flow regime. In both cases the flowmeter output voltage was found to be proportional to the mean velocity of the liquid phase. Experiments in a steady air-water mixture showed good agreement with the analysis. An impedance void fraction meter was designed and built to conduct measurements of unsteady void fractions. Short electrodes excited by voltages of opposite polarity were used in combination with a highly sensitive signal processor. The steady state calibration indicated that the meter was somewhat sensitive to the void fraction distribution for the bubbly flow regime. However, the transition to a churn turbulent regime greatly affected the meter steady state response. The dynamic capability of the void fraction meter was estimated by comparison of the statistical properties of the voltage fluctuations in a nominally steady bubbly flow with those of a shot-noise process. Also some properties of the disperse phase could be inferred from the statistical analysis. Two void fraction meters were used to measure the propagation speed of kinematic shocks in an air-water bubbly mixture for various void fractions and water flow rates. Measurements of the propagation speed of shocks of decreasing strength provided a good verification of the kinematic wave theory. The shock thicknesses could also be determined leading to the conclusion that an important diffusion mechanism was responsible for arresting the steepening of the wave. Cross-correlations of the fluctuating voltage of two void fraction meters in a steady bubbly flow were determined. The speed measured by this technique was identified as the infinitesimal wave speed of the void fraction and not the velocity of the dispersed phase as postulated by some authors. The cross spectral density revealed that the waves present in these disturbances were non-dispersive.
- OSTI ID:
- 5470682
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
420400* -- Engineering-- Heat Transfer & Fluid Flow
AIR
DATA
EXPERIMENTAL DATA
FLOW RATE
FLOWMETERS
FLUID FLOW
FLUIDS
GASES
HYDROGEN COMPOUNDS
INFORMATION
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
METERS
NUMERICAL DATA
OXYGEN COMPOUNDS
PERFORMANCE
SHOCK WAVES
THEORETICAL DATA
TWO-PHASE FLOW
VOID FRACTION
WATER
WAVE PROPAGATION