---A series of studies is presented in which an electrical-impedance tomography (EX") system is validated for two-phase flow measurements. The EIT system, developed at Sandia National Laboratories, is described along with the computer algorithm used for reconstructing phase volume fraction profiles. The algorithm is first tested using numerical data and experimental phantom 1

Gamma-densitometry tomography (GDT) experiments have been performed to measure gas holdup spatial variations in two bubble columns: a 0.19 m inside diameter Lucite column and a 0.48 m inside diameter stainless steel vessel. Air and water were used for the measurements. Horizontal scans at one vertical position in each column were made for several air flow rates. An axisymmetric tomographic reconstruction algorithm based on the Abel transform has been used to calculate the time averaged gas holdup radial variation. Integration of these profiles over the column cross section has yielded area-averaged gas holdup results, which have been compared with volume-averaged gas holdups determined from differential pressure measurements and from the rise in the aidwater interface during gas flow. The results agree reasonably well. INTRODUCTIONBubble-column reactors are used extensively by chemical manufacturers to perform a wide variety of gas/liquid or gas/liquid/solid reactions such as oxidation, hydrogenation, chlorination, aerobic fermentation and coal liquefaction (Shah and Deckwer, 1983). Bubble-column reactors are generally tall, cylindrical vessels filled with liquid, sometimes laden with a solid catalyst, c through which a gas is injected using a sparger at or near the bottom. The gas reacts with the liquid or catalyst to form a desired product, either a gas or a liquid, that is continuously removed from the vessel. Pressures and temperatures are controlled during the reaction to optimize product distribution. One of the main benefits of slurry-phase bubble-column reactors used in catalytic reactions is the ability of the liquid phase to provide an efficient heat sink for highly exothermic reactions. Under industrial conditions, the pressure, temperature, inlet gas velocity, and column diameter may be increased, to maximize total product production rates. The effects of increasing these parameters on the multiphase flow phenomenology must be considered when attempting to scale laboratory reactors to industrial sizes and operating conditions. Development and application of noninvasive tomographic diagnostics capable of measuring gas holdup (ratio of local gas volume to total volume) spatial distributions in full-scale reactors will greatly facilitate current efforts to predict reactor performance.Gamma densitometry has been applied for measurement of local density in multiphase flows for some time (e.g., Petrick and Swanson, 1958;Swift et al., 1978;Chan and Banerjee, 1981).Standard gamma densitometry measures gamma attenuation integrated along a path through the medium, and thus lacks spatial resolution. However, spatially resolved measurements can be made by applying tomographic reconstruction algorithms to the results of measurements along many different paths. Although gamma-densitometry tomography (GDT) can measure spatially resolved gas holdup in a gas/liquid flow, neither instantaneous gas holdup nor bubble size distributions can be measured due to the time required for data acquisition. Several groups...

---Experiments are presented in which electrical-impedance tomography (EIT) and gammadensitometry tomography (GDT) measurements were combined to simultaneously measure the solid, liqui~and gas radial distributions in a vertical three-phase flow. The experimental testbed was a 19.05-cm diameter bubble column in which gas is injected at the bottom and exits out the top while the liquid and solid phases recirculate. The gas phase was air and the liquid phase was deionized water with added electrolytes. Four different particle classes were investigated for the solid phase: 40-100 pm and 120-200 pm glass beads (2.41 g/cm3), and 170-260pm and 200-700pm polystyrene beads (1.04 g/cm3), Superficial gas velocities of 3 to 30 cmk and solid volume fractions up to 0.30 were examined. For all experimental conditions investigated, the gas distribution showed only a weak dependence on both . particle size and density. Average gas volume fraction as a fimction of supert3cial gas velocity can be described to within &O.04by a curve passing through the center of the data. For most cases the solid particles appeared to be radially uniformly dispersed in the liquid.

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Understanding fuel-injection processes is important for improving combustion in compression-ignition engines. To understand and model injection processes in detail, it is necessary to measure the instantaneous mass flow rate of fuel through each orifice of the injector nozzle. Due to constraints from injector design and operation, injection rate is typically measured downstream from the orifice exit. Measuring injection rate from a multi-orifice nozzle adds several geometric constraints, particularly when measuring fuel flow from a single orifice. The injection ratemeter discussed in this paper is designed to fit inside an optical research engine so that the injection rate can be measured without having to place the injector in an external fixture. The injection rate is calculated from a measurement of the momentum flux of a jet of fuel impinging upon the surface of a piezoelectric force (or pressure) transducer, combined with a measurement of the quantity of fuel injected, as demonstrated previously [1–3]. The ratemeter includes a thermal shield to limit the effects of temperature fluctuations on the transducer output. Data were acquired for one injector nozzle at several different injection durations and compared to results from literature for similar injector designs. Estimates for the uncertainty of the measured injection rates are provided and the calibration technique used is presented.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.