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The tracer method has been adopted to study stratified–dispersed flow in a horizontal pipe, 80 mm in diameter and 50 m long, operating at 5 Bar with nitrogen–water mixtures. The use of the tracer method in a horizontal pipe required the development of a specially designed test section, the related electronics and a data acquisition system. It has also been necessary to develop a tracer injection system, which has been designed in order to obtain uniform tracer concentration in the liquid film immediately after its injection. The main flow parameters which can be measured with the present experimental set-up are the circumferential distribution of the film height, flow rate and tracer concentration, the rates of droplet entrainment and deposition and the split of the liquid phase between the wall layer and the entrained droplets. The average tracer concentration data have been interpreted with a new three-field model of the liquid phase in the stratified–dispersed flow pattern. In the present formulation, the model holds for steady, fully developed flow conditions and is based on a one-dimensional description of the flow system. The data cover a limited number of flow conditions.

A test section consisting of a circumferential array of conductance probes has been developed to measure the thickness distribution around the pipe wall of a liquid layer flowing in near horizontal pipes. When the film thickness is known, the array can be employed to measure the local film flow rate by injecting a high conductivity tracer into the liquid flowing at pipe wall. The test section consists of a short pipe made of a non-conducting material installed in a flow rig designed to operate at an appreciable pressure (40 bar). The flow loop is made of metallic pipes connected to the electrical earth. The conductance probes are made of three parallel, rigid wires spaced along the flow direction and are used to measure the height or the electrical conductivity of the liquid layer. The three-electrode geometry is aimed at minimizing current losses toward earth. The simultaneous operation of all the probes of the array, without multiplexing, allows a substantial reduction of current dispersion and a good circumferential resolution of film thickness or conductivity measurements. The probe geometry may generate an appreciable disturbance to the gas–liquid interface. This aspect of the proposed method has been studied with an experimental and numerical investigation relative to free falling liquid layers.

There is a high industrial interest today in the development of accurate measurement techniques to support the modelling of gas-liquid flow phenomena. When dealing with stratified flow in horizontal or inclined pipes, the main problem is that in the range of medium to large gas velocities there are very few data available for the development or validation of flow models. These data should include the measurement of the pressure gradient, the circumferential liquid film distribution, the liquid hold-up and the fraction of entrained droplets. This work describes the development and experimentation of a measurement set-up for generating these data at flow conditions as close as possible to those of industrial interest, in terms of pipe diameter and physical properties of the fluid. This paper focuses on the measurement technique, which is based on conductivity measurements by arrays of needle-shaped electrodes, and illustrates one practical implementation and its validation.

This paper shows the experimental results that have been performed to identify transitions from Slug flow in horizontal pipes. The flow patterns were identified by the analysis of local and cross section averaged signals of liquid hold-up collected by conductivity probes. New mechanisms were suggested to identify the boundaries of the Slug flow regimes. A new approach to identify the range of existence of Slug flow in long pipelines is also suggested.

The basin of the River Arno is a flood-prone area where flooding events have caused damage valued at more than 100 billion euro in the last 40 years. At present, the occurrence of an event similar to the 1966 flood of Firenze (Florence) would result in damage costing over 15.5 billion euro. Therefore, the use of flood forecasting and early warning systems is mandatory to reduce the economic losses and the risk for people. In this work, a flood forecasting model is presented that exploits the real-time information available for the basin (rainfall data, hydrometric data and information on dam operation) to predict the water-level evolution. The model is based on artificial neural networks, which were successfully used in previous works to predict floods in an unregulated basin and to predict water-level evolution in the Arno basin under low flow conditions. Accurate predictions are obtained using a two-year data set and a special treatment of input data; which allows a balance to be found between ...

In this work, we analyzed pollution in the river Arno using a non-steady advection-dispersion-reaction equation (ADRE) calibrated on experimental data. We examined the influence different pollution control strategies have on dissolved oxygen (DO). We considered (i) flow rate variation; (ii) local oxygenation at critical points; (iii) dynamic modification of wastewater load. Results indicate first, that reservoir management is effective in reducing pollution; second, that local oxygenation is necessary to ensure that DO does not fall below safety levels; and finally, that tuning wastewater loads appears to be impractical to manage the river quality given the stringent limitations it would impose on the industrial effluents.

The pollution in the river Arno downstream of the city of Florence is a severe environmental problem during low-flow periods when the river flow rate is insufficient to support the natural waste assimilation mechanisms which include degradation, transport, and mixing. Forecasting the river flow rate during these low-flow periods is crucial for water quality management. In this paper a neural network model is presented for forecasting river flow for up to 6 days. The model uses basin-averaged rainfall measurements, water level, and hydropower production data. It is necessary to use hydropower production data since during low-flow periods the water discharged into the river from reservoirs can be a major fraction of total flow rate. Model predictions were found to be accurate with root-mean-square error on the predicted river flow rate less then 8% over the entire time horizon of prediction. This model will be useful for managing the water quality in the river when employed with river quality models.

A neural network model was developed to analyze and forecast the behavior of the river Tagliamento, in Italy, during heavy rain periods. The model makes use of distributed rainfall information coming from several rain gauges in the mountain district and predicts the water level of the river at the section closing the mountain district. The water level at the closing section in the hours preceding the event was used to characterize the behavior of the river system subject to the rainfall perturbation. Model predictions are very accurate (i.e., mean square error is less than 4%) when the model is used with a 1-hour time horizon. Increasing the time horizon, thus making the model suitable for flood forecasting, decreases the accuracy of the model. A limiting time horizon is found corresponding to the minimum time lag between the water level at the closing section and the rainfall, which is characteristic of each flooding event and depends on the rainfall and on the state of saturation of the basin. Performance of the model remains satisfactory up to 5 hours. A model of this type using just rainfall and water level information does not appear to be capable of predicting beyond this time limit.

A leak detection system for pipelines was developed by using artificial neural networks (ANN) for leak sizing and location and by processing the field data. This system can detect and locate leaks down to 1% of flow rates in pipelines carrying hazardous materials in about 100 s. A reference pipeline was considered for practical implementation of the package. The ability of the package to withstand spurious alarms in the event of operational transients was tested. The compressibility effect, due to packing of the liquid in the pipeline, causes many such spurious alarms. Adequate preprocessing of the data was performed by using a computer code in conjunction with the ANN to compensate for the operational variations and to prevent spurious alarms. The package detects leaks as small as 1% of the inlet flow rate and correctly predicts the leaking segment of pipeline with a probability of success that is greater than 50% for the smallest leak. In all cases, the timely response of the system was seen as a major advantage.

Laser sensing enables aerial detection of natural gas pipeline leaks without need to fly through a hazardous gas plume. This paper describes adaptations of commercial laser-based methane sensing technology that provide relatively low-cost lightweight and battery-powered aerial leak sensors. The underlying technology is near-infrared Standoff Tunable Diode Laser Absorption Spectroscopy (sTDLAS). In one configuration, currently in commercial operation for pipeline surveillance, sTDLAS is combined with automated data reduction, alerting, navigation, and video imagery, integrated into a single-engine single-pilot light fixed-wing aircraft or helicopter platform. In a novel configuration for mapping landfill methane emissions, a miniaturized ultra-lightweight sTDLAS sensor flies aboard a small quad-rotor unmanned aerial vehicle (UAV).

This paper describes a method for computing: (1) the chemical composition of the first drop of condensate which forms at dew-point temperature through expansion of superheated steam, and (2) the saturation index of the drop with respect to relevant solid phases, such as halite, amorphous silica, boric acid, borax and sal ammoniac. Boiling-point elevation is taken into account in these calculations. Preliminary application to some wells in the Larderello geothermal field indicate that: (1) the high concentration of HCl in the steam causes both the low pH and very high TDS of the first drop; (2) the lower the dew-point temperature, the higher the TDS of the first drop; (3) for a given chemical composition, the lower the steam pressure, the higher the risk of corrosion and scaling in the steam path.

The design of two-phase flow lines for geothermal applications requires reliable information about main flow parameters. In the present work a one-dimensional, steady-state model for the computation of hold-up and pressure losses in horizontal and near-horizontal pipes is presented. The model is based on a mechanistic analysis of Stratified, Intermittent and Bubbly flow. The model has been implemented in the two-phase flow simulator, HORF, which has been developed in order to predict pressure losses relative to pipeline flow of geothermal brines. It is shown that the predictions are in very good agreement with field data obtained at Latera geothermal field, in Italy, relative to a flow line 2400 m long, and 18“ nominal diameter.

Air-water slug flow at atmospheric conditions in horizontal pipes of 31 and 53 mm i.d. has been characterized experimentally with local (optical) and cross-sectional (conductance) probes. The objective of the work is to improve the description of slug flow and the closure relations required in mean kinematic slug flow models. Local measurements include the radial void fraction distribution in the slugs, the size of the dispersed bubbles in the slug and the aeration of the liquid layer under the slug bubble. From cross-sectional holdup measurements, slug lengths and frequencies are determined, as well as the length of the highly aerated mixing zone in the front of the slugs. Measured values of film holdup at the tail of the slug bubbles and of slug frequency are compared with a physical model of slug flow derived from the work of Dukler & Hubbard.

Air/water slug flow in 53 and 90 mm i.d. horizontal pipes has been investigated for a large range of gas and liquid velocities. For this purpose a special instrumentation with simultaneous data acquisition and analysis has been developed. This has been used to determine the mean slug characteristics (length, holdup and velocity) and their statistical distributions.

For fully-developed two-phase flows, maps that correlate experimental and semi-empirical expressions for flow regimes are widely used. For calculations of the various important two-phase flow parameters, this in turn requires correlations for various interfacial and wall interaction effects that are flow regime dependent. For many systems of practical interest, however, the evolution of flow regimes (such as slug flow in oil–gas pipelines) is of interest because the development lengths are long and flow regimes may change in regions where pipeline inclination changes due to the terrain. It is shown here that for slow transients in near-horizontal pipes, the one-dimensional multi-field model, when solved with sufficient resolution, does not require flow regimes to be specified or flow regime dependent closure relationships. The formulation predicts the development of flow regimes and various flow parameters without the need for maps, or the need to change closure relationships. To accomplish this, the model includes four fields, i.e. continuous and dispersed liquid, continuous and dispersed gas, as well as a set of appropriate closure relationships from the literature. For the main application considered here, i.e. slow transients in oil–gas pipelines, order of magnitude analyses indicate that certain inertial terms in the model are very small and can be neglected in comparison to the others. Advantage is taken of this to simplify both the structure of the mathematical problem and the solution procedure, which is sufficiently accurate that mass is conserved for each of the four fields. Furthermore, the calculations require high spatial resolution, so a fast, easily-parallelizable numerical procedure has been applied. The results indicate that the development of certain flow regimes, including transitions from bubbly to stratified flow and vice versa, slug flow including slug frequency and length, and the evolution of these parameters along a pipeline are well predicted by the model when compared to experimental data. As part of the validation it is also shown that the model predicts, without need to change closure relationships, flow regimes in fully-developed near-horizontal two-phase flows in good agreement with existing flow regime maps. This suggests that for slow transients in flows for which one-dimensional effects dominate, predictions can be made without requirements for flow regime maps and closure relationships that depend on them.

In stratified gas–liquid horizontal pipe flow, growing long wavelength waves may reach the top of the pipe and form a slug flow, or evolve into roll-waves. At certain flow conditions, slugs may grow to become extremely long, e.g. 500 pipe diameter. The existence of long slugs may cause operational upsets and a reduction in the flow efficiency. Therefore, predicting the flow conditions at which the long slugs appear contributes to a better design and management of the flow to maximize the flow efficiency. In this paper, we introduce a wave transition model from stratified flow to slug flow or roll-wave regimes. The model tracks the wave crest along the pipe. If the crest overtakes the downstream wave end before hitting the top of the pipe, a roll-wave is formed, otherwise a slug. For model validation we performed measurements in air–water horizontal pipe flow facilities with internal diameters of 0.052 and 0.06 m. Furthermore, we made numerical calculations using a transient one-dimensional multiphase flow simulator (MAST) which adopts a four-field model. The model presented in this paper successfully predicts the evolution of waves and their transition into either slugs or roll-waves. It also predicts the formation time of slugs and roll-waves with a satisfactory agreement.

ENI E&P in 1993 launched an R&D project on production boosting using multiphase jet pumps. In these devices a high pressure oil or gas well can be used to enhance both the production and the total recovery from a depleted well. The multiphase ejector is characterized by a simple design, absence of moving parts and small dimensions, coupled with a high degree of reliability and low cost. The main disadvantages related to the use of multiphase ejectors are due to the lack of reliable design methods and to the sharp decrease of the performance when operative conditions change. In the last three years the ejector technology can be considered a standard for ENI resulted in several successful installations worldwide: -West Africa (onshore oil wells)-GOM (offshore, condensate gas )-Italy and Mediterranean Sea (onshore and offshore, wet and dry gases) In the present work a status of these installations is reported, pointing out the following main items: -design and installation peculiarities-predicted and measured performances-optimisation actions performed during the considered period The results of this review have been used to identify the new strategies on ejector design and operability, which will be also reported. In particular, new design to increase productivity and component operability life is described, together with laboratory test results

Abstract A high pressure oil or gas well can be used to enhance both the production and the total recovery from a depleted well using a multiphase ejector. This device does not require any power supply and is characterized by a simple design, absence of moving parts and small dimensions, coupled with a high degree of reliability and low cost. The main disadvantages related with the use of multiphase ejectors are due to the lack of reliable design methods and to the sharp decrease of the performance when operative conditions change. In August 2002 a multiphase ejector has been installed in Allegheny TLP, GOM, to boost the production from a depleted well. In the present paper the design method and the results of field tests of the Allegheny ejector are presented. From a practical view-point the main result of this installation has been an increase of production of 1300 BOPD with an investiment of less than 50,000 USD. Introduction The ejector or Jet Pump, JP, is an artificial lift method which does not require any power supply and is characterized by a simple structural design, absence of moving parts and small dimensions, which allows easy installation and management procedures during fields operations, coupled with a high degree of reliability and low cost of installation, compared with other boosting systems. On the other hand, the ejector is a low-efficiency device: just a small fraction of the power fluid energy (approximately 20-30%) is actually transferred to the low pressure fluid (however it should be remarked that in many cases this energy would be lost through a choke valve). When the ejector is fed with multiphase fluids, significant modelling problems arise and no established methods are available for the design of multiphase ejectors. Design problems are increased by fluid properties changes during field evolution. To cope with all these problems and extend the operative life of the ejector, an advanced multiphase ejector has been developed in order to optimise some of the main geometrical parameters and improve the ejector performances at varying operative conditions. In this paper, the realization and field application of this multiphase ejector are described. Fig. 1 shows the main components of a JP: the nozzle, the mixing chamber followed by the mixing duct and the diffuser sections. Power fluid, at an injection pressure Pd is forced through the nozzle. As the fluid accelerates because of the area reduction, its kinetic energy increases and the pressure decreases to the value Pn at the nozzle exit section. The power and the produced fluids then enter the mixing chamber were pressure reaches its minimum value, Ps. In the mixing chamber, mixing duct and diffuser the pressure increases and the gas-liquid mixture leaves the ejector at a pressure Pl. The main concern about actual multiphase ejectors is the limited capability of the hardware to be adjusted when boundary conditions change (i.e. well depletion, water cut and/or GOR variation, production profiles). To this aim, the present multiphase ejector has been designed to be adaptable in terms of

Increasingly stringent HS&E requirements inevitably leads to an improvement in the predictive risk analysis tools used to estimate the HS&E consequences of a major accident. One potentially major accident, associated with the exploration and exploitation of hydrocarbon fields, is a blow-out e.g. an uncontrolled release of formation fluid from the reservoir. In the event of a blow-out it is essential to implement the blow-out contingency plan as quickly as possible to minimise the potential damage, particularly for onshore wells where the oil and gas is dispersed into the atmosphere and over the land. To improve the evaluation of the safety and environmental consequences of a blow-out the Agip Division commissioned a multi-disciplinary R&D project. This project utilises technical and scientific support from EniTecnologie, TEA Sistemi and TEMARS companies. The main objective of this project is the development, assessment and validation of an integrated methodology for the evaluation of the safety and environmental consequences of a blow-out. The extension of the contaminated area, the gas and oil droplets concentration distribution and the oil and gas discharge flow-rates from the well are the main deliverables from the methodology. As the primary use of this methodology would be in the management of the emergency response to a blow-out it is essential to optimise the response time. Subsequently, the following predictive approaches were developed and validated against actual blow-outs: A "One Minute" estimation tool; A "Ten Minute" estimation software; A "Best Estimation" approach. To better characterise the oil droplet field from the wellhead to the environment "ad hoc" experimental work is undertaken to reproduce the real conditions associated with a blow-out.

A set of experiments has been performed to analyse gas-phase distribution in horizontal bubble flow. The experimental data have been obtained by means of conductance probes and include measurements of the local void fraction and the bubble diameter and velocity. Present observations show large variations of the local void fraction and the bubble size moving from the top to the bottom of the pipe, with local maxima located close to the upper pipe wall. Measurements also show that, at the boundary of the dispersed bubble flow regime, the bubble size, and therefore the surface available for heat and mass transfer, changes abruptly for small variations of the liquid or gas flowrate. This change allows the transition between the dispersed and the elongated bubble regimes to be identified with good precision. Present data make it possible to develop a new correlation for the maximum bubble size in dispersed bubble flow.

This study investigates the use of low-temperature catalytic oxidation for the removal of H 2 S from tail gases originating from geothermal plants, with special focus on the effect of water on the overall performance of the activated carbon catalyst. It is shown that water strongly influences the reaction rate and the total amount of sulfur that can be adsorbed on the catalyst prior to regeneration. It is suggested that the reaction takes place in a thin water layer, inside the carbon pores, from the reaction of dissolved H 2 S with chemisorbed oxygen.

In vertical annular flow, the motion of droplets in the gas core is dominated either by a diffusion mechanism, when the droplet size is small, or by inertial effects when droplets are large. These two mechanisms have to be considered when predicting deposition rates. Furthermore, since droplet-droplet interactions influence droplet motion, a deposition model should also account for collisions and coalescence among droplets. After reviewing the available deposition models, the effect of coalescence on droplet motion is theoretically analyzed. The results demonstrate that coalescence extends droplets residence time in the gas core thus decreasing the deposition coefficient. On the basis of these results, a new deposition model which accounts for the two deposition mechanisms and includes the effect of coalescence is proposed and compared against existing experimental data.

The dispersion of particles in turbulent duct flow under the influence of electrostatic fields is studied using direct numerical simulation. In this new approach, particles are moved in the temporally and spatially varying turbulent flow field under the influence of electrostatic and gravitational body forces, as well as fluid dynamic drag. The simulations agree well with previously performed experiments (done in geometries typical of wire-plate and plate-plate electrostatic precipitators) not only in the overall collection efficiency of particles, but in particle concentration profiles at various axial locations in the flow direction. This gives confidence in the technique that may be used to study different precipitator geometries and flow field configurations, supplementing costly and difficult experiments. Furthermore, information is obtained at a much more detailed level than is possible via experiments, allowing insights into the mechanisms dominating particle collection.

A linear stability analysis has been performed to investigate the stability of liquid flow down an inclined circular tube. To this purpose, approximate solutions which describe laminar and turbulent steady flow down an inclined tube have been developed first. The stability analysis has then been performed by an integral method. The results of the present investigation indicate that, in general, flow in a tube is more stable than in a channel and, in particular, there is a value of the liquid height at which the flow is always stable.

The aeration of a liquid body advancing over a slow moving liquid layer in a pipe has been experimentally investigated with a conductance method. The 50 mm i.d. pipe section was close to horizontal and the fluids were air and water at atmospheric conditions. It has been found that net gas entrainment only occurs when the relative velocity between the advancing front and the liquid layer is greater than a limiting value. The rate of gas entrainment is proportional to the relative velocity between the advancing slug and the liquid layer, and to the interfacial width of the layer. Measured pressure drops, film heights and gas volume fractions in the advancing slug agree well with available correlations or with similar measurements taken under conditions of fully developed slug flow.

The derivation of a correlation for drop size in annular flow based on a mechanistic model is presented. Optimum values of four constants were obtained by a fit to measured data over a wide range of gas and liquid flow rates, physical properties and pipe diameter.

The main characteristics of CWF (coal-water fuel) sprays produced by an internal mixing twin fluid atomizer are analyzed. Drop size and concentration have been determined by a laser light diffraction method (Malvern) and a high-speed photographic technique. The combined use of different experimental methods, along with the numerical inversion of line-of-sight measurements, allows a reliable characterization of the spray structure along radial and axial coordinates. The mean drop size depends essentially on the dynamic head of the atomizing air, the surface tension, and the coal particle size distribution of the slurry fuel. No clear effect of the CWF's apparent viscosity has been detected. The equation developed to correlate mean drop size takes all relevant factors into account and was derived for a nozzle operating with sonic flow in the exit ports.

The void fraction in liquid slugs has been determined for air—water fiow in horizontal and near-horizontal pipes by a newly-developed conductance probe technique. A semi-empirical correlation has been developed and compared with the present measurements and available data. This correlation predicts reasonably well the observed effects of diameter, inclination and physical properties.

Measurements of the effect of liquid viscosity on the initiation of roll waves in a horizontal gas-liquid flow are presented. These results are interpreted by an analysis based on the calculation of the growth of long wavelength disturbances.

A mathematical description of droplet entrainment and deposition is presented. This enables both unidirectional deposition and interchange experiments to be analysed. This approach permits description of deposition by both the diffusion like mechanism conventionally used and by the direct impaction mechanism which has recently been identified. A criterion has been derived to differentiate between the two mechanisms of deposition based on the balance between the initial drop momentum and the drag force of a turbulent eddy. The transition criterion has been substantiated with experimental data derived from unidirectional deposition experiments. A preliminary examination of interchange data has been carried out.

The point of onset of large disturbance waves and droplet entrapment has been determined for the annular downward flow of air-water mixtures in a 24 mm ID tube. Experimental results are in a good qualitative agreement with the previous work by Webb and Hewitt1. These results indicate that 1the critical gas velocity at the onset of entrainment is lower than the value predicted by available correlations 2the critical gas velocity continuously decreases at increasing the liquid Reynolds number 3below a liquid Reynolds number of 270 no entrainment occurs even at gas velocities as high as 80 m/sec A correlation for the critical gas velocity which is based on a simple physical model of atomization, is also proposed.

A liquid hold-up gauge based on the measurement of the electrical impedance has been developed for application in gas-liquid pipe flow. The gauge consists of two ring electrodes mounted flush to the pipe wall. The impedance (capacitance or conductance) seen by the electrodes depends on the distance between them and on the liquid hold-up. For distances above three tube diameters, the impedance is independent of the flow configuration for all separated flow patterns and, with good approximation, also for intermittent flows. Moreover, capacitance or conductance are linearly related to the liquid hold-up. The impedance under bubble flow conditions closely follows the theoretical predictions due to Maxwell. Also for the other flow configurations (annular, stratified, intermittent) the results of static and/or dynamic calibration agree closely with theoretical models.

New measurements are presented for film height and pressure drop for vertical gas-liquid annular flows. Improved methods for predicting the film height and interfacial friction factor are developed for situations in which the liquid film flow rate is known.

Previous investigations in this laboratory on the structure of diffusion flames formed over a liquid fuel surface with a parallel oxidizer flow have been completed with the identification of the soot field. To this purpose the standard laser light scattering-extinction technique used by a number of authors has been adopted. Measurements of fluorescence and UV absorption are also reported. According to present measurements the flame can be divided into three zones: the fluorescence zone, where polycyclic aromatic hydrocarbons (PAH) are formed, the soot zone and the combustion zone. Soot inception seems to occur close to the high temperature combustion zone, but present measuremenls of the number density of soot particles may also indicate that soot is generated at lower temperatures, within the fluorescence zone.

Downward annular two-phase flow (air-water) has been examined experimentally. Statistical methods have been applied to calculate the flowrates associated with the hypothetical substrate flow and large wave flow. Agreement with actual Jiquid flowrates under varying gas flows is good. The constant thickness assumption is shown to give significant error. Main characteristics of large waves have also been determined. L'ecoulement biphasique annulaire descendant (air-eau) a ete etudie experimentalement. Des methodes statistiques ont ete appliquees aux calculs des debits associes a l'ecoulement hypothetique du substrat et a l'ecoulement de grandes ondulations. L'accord avec les debits reels en presence de differents ecoulements gazeux est bon. L'hypothese d'une epaisseur constante s'est averee impliquer une erreur importante. Les principales caracteristiques des grandes ondulations ont egalement ete determinees.

A theoretical model has been developed to simulate the reacting boundary layer flow over a horizontal fuel surface. This model is based on the assumption that molecular diffusivities are equal for all species and on an approximate formulation of the heat balance equation. Fuel oxidation has been assumed to be infinitely fast.

The main characteristics of diffusion flames formed on a liquid fuel surface with a parallel oxidizer flow have been studied both analytically and experimentally. In the present paper fuel burning rates and temperature and velocity profiles have been determined for various liquid fuels. Experimental results arc in good agreement with the theoretical model previously developed by one of the authors, except for the velocity profiles at low air velocity, which display a pronounced overshoot close to the flame zone. Present results also indicate that main flame characteristics can be controlled by means of the temperature of the liquid fuel contained in the burner and kept constant for long times. Finally, the burner studied in this research appears to be particularly suitable for the analysis of combustion kinetics.

Measurements of liquid hold-up and pressure drop are reported for stratified flow in a slightly inclined (0.65° and 2.1°), 5 cm pipeline. Velocity profiles in the gas phase have been determined for a limited number of flow conditions. Semi-empirical correlations are proposed for the transition to slug flow, the interfacial friction factor and the liquid hold-up.

Resultats de l'analyse de films cinematographiques obtenus avec la methode de la lumiere parallele de Hewitt et Whalley. Correlation des resultats par une equation simple qui peut etre reliee a l'analyse de la rupture d'onde de Taylor

The tracer method, adopted by a number of experiments for the measurement of the rate of liquid interchange between the wall layer and the dispersed phase in a fully developed annular flow, has been critically examined on the basis of a more accurate description of the flow behavior of entrained droplets. The results obtained indicate that this experimental technique can give reliable results in a wide range of flow conditions when the experiments are properly designed. Present measurements of the interchange show that the dimensionless deposition coefficient is a function of the concentration of entrained droplets. This effect appears to be due to the dependence on concentration of droplet size. The rate of entrainment is proportional to the liquid film flowrate and to the gas velocity squared.

The structure of the diffusion flame formed on a liquid fuel surface with a parallel oxidizer flow was studied both analytically and experimentally. Only the case of ethyl alcohol burning in air has been considered in this paper. The temperature and species concentration profiles across the boundary layer were determined by means of fine, carefully calibrated thermocouples and of gas chromatography. The gas analysis yielded the concentrations for the following species: N 2 , C 2 H 5 OH, O 2 , CO 2 , H 2 O, CO, CH 4 , C 2 H 2 +C 2 H 4 , C 2 H 6 , CH 3 CHO, H 2 . The mathematical model is based on the Shvab-Zeldovic formulation of conservation equations with physical properties considered as functions of temperature and species concentration. The agreement obtained between the experimental and theoretical profiles of temperature and of normalized elemental mass fractions of the atomic species N, O, C, H is satisfactory when the fuel diffusivity in nitrogen replaces the actual species and thermal energy diffusivities in the conservation equations.

A mechanistic model of slug flow based on a set of mass and momentum conservation equations and a number of empirical closure relations is presented. It is then shown that a simplified version of the model, which physically corresponds to the flow of long liquid slugs (long slug model, LSM), can be immediately derived from the general model. The LSM is much simpler than the general model; at the same time, the predictions obtained in the two cases are very similar, when the comparison is limited to the computation of the pressure gradient and the mean liquid holdup. The LSM successfully correlates a large set of experimental measurements relative to three pipe diameters (18, 50, and 90 mm), four inclinations (0[degree], [+-]3[degree], 0.3[degree]), and two pipe lengths (17 and 34 m).

A very simple, low-cost gas-liquid flow meter that only employs conventional field instrumentation has been used to monitor severe slugging occurring at the exit of a vertical pipe. This meter was originally developed for conventional oil field applications [1] and is based on the readings of a multiphase orifice and the pressure drops of the gas-liquid mixture flowing in a vertical section of the pipe. Liquid and gas flow rates have been determined by means of semi-empirical equations developed for the specific set of flow parameters (geometry, flow rates, physical properties) adopted in a series of laboratory tests conducted in the Multiphase Flow Laboratory of TEA Sistemi. The transient behavior of the flow system, including the orifice, has also been predicted by means of a 1-D flow simulator [2]. The results of these simulations agree well with the experimental readings, thus providing a powerful method to monitor severe slugging by means of low cost instrumentation, in particular, by replacing a cumbersome instrument such as a gamma-densitometer with a differential pressure transmitter. In field operation, the multiphase orifice used in these experiments can be replaced by a calibrated control valve.