Electrical Engineering

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In multiphase flow, bubbles are produced and collapse on the solid/liquid interface. Bubble collapse can enhance the CO2 corrosion of carbon steel pipe, as shown by coupon surface analysis, corrosion rate measurements and visualization of bubble movement in multiphase flow. Using the electrochemical limiting current density technique, experiments have been carried out to study the effect of bubbles on mass transfer in an electrochemical cell and in slug flow. The limiting current density signal as a function of time and frequency shows the direct influence of bubble movement on mass transfer. It also indicates the difference of mass transfer in fully developed turbulent flow, an electrochemical cell and slug flow. The enhancement of mass transfer coefficient by bubble collapse is considered an important factor that contributes to the increased corrosion rate in multiphase flow. © 2000 by NACE International.

World University root node

(SoE) School of Engineering

NACE - International Corrosion Conference Series

Effect of bubbles on mass transfer in multiphase flow

Tracking of multiple targets by using only the bearing information is an important problem in passive sensing scenarios such as passive sonar or infrared seeker applications. In this paper, a new algorithm is presented to adaptively estimate the DOA's of multiple moving targets when Linear Equispace Array (LES) is used for making the measurements. These algorithms are based on Differential MUSIC method. The results obtained by these algorithms are then applied as input to a Non-Linear state linear Measurement unscented filter. The unscented filter based tracker is compared with the EKF based tracker. Simulation results show that the former is superior to the latter.

Proceedings of the IEEE International Conference on Industrial Technology

Passive target tracking by unscented filters

Corrosion rates at the top and bottom of the pipe have been measured in wet gas multiphase flow at carbon dioxide partial pressures of 0.46 MPa and 0.79 MPa and temperatures of 40 C and 60 C in a high pressure 10-cm diameter system. Gas velocities up to 30 m/s and liquid velocities up to 0.5 m/s were used. The liquid consisted of a mixture of de-ionized water and low viscosity oil at two water cuts of 80% and 40%, and carbon dioxide was used in the gas phase. Corrosion inhibition studies were carried out at 50 ppm and 100 ppm dosage levels. The inhibitor used was an oleic imidazoline active compound dissolved in isopropyl alcohol and water. The corrosion rate was found to increase with increase in gas velocity, liquid velocity, temperature and CO2 partial pressure. The corrosion rate at the top of the pipe is negligible up to a gas velocity of 20 m/s. However, at a gas velocity of 30 m/s, there is substantial and measurable corrosion at the top of the pipe. This was attributed to wave spreading. Addition of inhibitors reduced the corrosion rate at the top and bottom of the pipe significantly. However, the corrosion rates are not negligible. © 2000 by NACE International.

Inhibition of multiphase wet gas corrosion

This paper presents the experimental results for CO2 corrosion of C-1018 carbon steel in a multiphase flow system using electrochemical noise measurement. A unique biased ZRA mode electrochemical noise technique is utilized to study the corrosion processes and detect localized corrosion preferentially on a single electrode due to external polarization of the bias voltage under extended exposure times. For full pipe flow at 0.55 m/s liquid velocity, the experimental results show that both noise resistance Rn and noise impedance Rosn can be related to the corrosion activity. The trends of Rn and Rosn at different experimental times are also consistent with the results obtained from EIS experiments. The experimental results at slug flow of Froude Numbers of 6 and 9 show that the magnitude of current noise increases with the increase of flow turbulence, Compared to slug flow, the current noise fluctuation for full pipe flow is much lower. © 2000 by NACE International.

Corrosion monitoring using electrochemical noise measurement with bias voltage

We reconsider the mode of operation of a Marx bank circuit and analyze the secondary breakdown of transistors with shorted emitter-base. The mechanism of breakdown of the transistor when a fast rising voltage pulse is applied across is investigated. The device exhibits chaotic behavior at the breakdown point where it can go into two possible modes of breakdown. A new explanation for the working of the circuit consistent with the experimental observations is proposed.

Solid-State Electronics

Breakdown of transistors in Marx bank circuit

This communication reports the effects of multiphase flow on the corrosion products formed on the surface of 1018 C-steel coupons in oil and gas lines. The main objective of this paper is to understand the effects of multiphase flow (full pipe and slug flow Fr. No. 6 and 9 at various flow and oil-water mixtures) on the morphology and the porosity of the C-steel coupon subjected to a horizontal test loop. The corrosion product layer formed on the surface of the steel coupons were analyzed using Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy (EDS), X-ray mapping, Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). Detailed porosity calculation has been carried out using metallographic software. The porosity increases as the flow velocity is increased. The corrosion product layer is primarily made of iron carbonate crystals along with Na and CI as indicated by EDS measurements. Detailed XPS analysis show the deterioration of inhibitor film as the flow is increased from full pipe (Fr = 0) to slug flow (Fr = 6). XPS shakeup satellite lines in the N (1s) spectra have been useful in the analysis. © 2000 by NACE International.

Surface chemical and morphological changes in corrosion product layers and inhibitors in CO2 corrosion in multiphase flowlines

Corrosion Experiments were carried out under iron carbonate scale-forming conditions in a large diameter, multiphase flow system. Both oil/water and oil/water/gas slug flows were studied at pressures up to 0.79 MPa and temperatures of 60 °C and 80 °C. It was found that with increasing iron concentration, the corrosion rates were reduced to negligible values in oil/water flows. However, significant corrosion was seen in slug flow with clear evidence of damage to the corrosion product layer due to impact and possible collapse of gas bubbles and a considerable reduction in the layer thickness. Details of corrosion rates and corrosion coupon surface analysis are presented. © 1999 by NACE International.

Effect of multiphase slug flow on the stability of corrosion product layer

The design, fabrication, and testing of a fractional h.p. permanent magnet synchronous motor (PMSM) are reported in this paper. The stator has been fitted with a balanced three-phase mush winding. Moreover, the performance analysis using Maxwell Field Simulator has been included. The test results of the motor with a fan load confirms the satisfactory operation of the machine designed in this paper. © 1999 Taylor & Francis.

Electric Machines and Power Systems

Design of a permanent magnet synchronous motor

Multiphase oil/water/gas flow regime transition studies are carried out in a 10-cm Id., 18-m long pipe at inclinations of ±2 deg at system pressures between 0 to 0.79 MPa. The results are compared to those of other researchers, and the ejfects of pressure, inclination, and liquid viscosity are shown. The water cut of the liquid has some effects on the transition from stratified to slug flow. Increasing the water cut results in the transition occurring at higher liquid velocity at the same gas velocity. Water cut has little effect on the slug/annular transition for low viscosity oil used. The system pressure has a moderate effect on the transition from stratified to slug and slug to annular. For the transition from stratified to slug, increasing the system pressure requires higher liquid velocity. The transition from slug to annular occurs at lower liquid velocity with increasing the system pressures. The inclination of the pipe has little effect on the transition from slug to annular flow. Increasing the inclination causes the transition to occur at approximately the same gas velocity at the same liquid velocity. The experimental results show a good agreement with Wilkens' model. © 1999 by ASME.

Journal of Energy Resources Technology, Transactions of the ASME

Investigation of flow regime transitions in large-diameter inclined pipes

This paper presents results of an imidazoline based inhibitor using the Electrochemical Noise (ECN) and Electrochemical Impedance Spectroscopy (EIS) techniques in a multiphase flow pipeline. ECN and EIS measurements were made simultaneously in a 101.6mm I.D., 15m long acrylic pipeline using saltwater and carbon dioxide mixtures. Full pipe flow was studied for liquid velocity of 1.25 m/s and slug flow for Froude numbers 6 and 9. Experiments were carried out at a constant pressure of 136kPa and temperature of 40°C. The ECN signals and EIS spectra of blank and inhibition tests were obtained. The ECN technique is able to monitor the inhibitor film formation continuously. The current noise fluctuation is correlated to the corrosion rate for both blank test and inhibitor test. The higher current fluctuation indicates higher corrosion rates. Different EIS spectra were obtained for blank and inhibitor studies. The simple charge transfer process was seen to occur for blank tests while charge transfer and diffusion processes were taking place under inhibitor effects. © 1999 by NACE International.