Stabilising slug flow at large valve opening using an intermittent absorber

Slugging is one of the challenges usually encountered in multiphase transportation of oil and gas. It is an intermittent flow of liquid and gas which manifests in pressure and flow fluctuations capable of causing upset in topside process facilities. It can also induce structural defects in pipeline-riser system. The threat of slugging to oil and gas facilities has been known since the early 1970s. This study investigated a new method for slug flow stability analysis and proposed the use of active feedback control and intermittent absorber (a passive device) for hydrodynamic and severe slugging attenuation. The geometry impact on the hydrodynamic slug flow in pipeline-riser systems was established using modelling (LedaFlow and OLGA) and experimental studies. The unit cell model in both software packages, the slug tracking model of OLGA and slug capturing model of LedaFlow were employed for hydrodynamic slug modelling. Three distinct slug regions were reported for a typical pipeline-riser system. The H-region typifies the slug flow regime in the pipeline-riser system due to slug formed in the horizontal pipeline upstream the riser pipe. The V-region represents the slug flow regime due to the riser pipe while the I-region describes slug flow regime where both horizontal and vertical pipes contributes to the dynamics of the slug flow in pipeline-riser system. A simple but yet robust methodology that can be used for pipeline-riser system and slug controller design was proposed. The active feedback control was shown to help stabilise hydrodynamic slug flow at larger valve opening compared with manual valve choking. For the case study, a benefit of up to 5% reduction in riserbase pressure was recorded for the proposed method. This in practical sense means increase in oil production. The analysis also showed that the new slug attenuation device (intermittent absorber) possesses the potential for slug attenuation. Experimental studies showed that the device was able to reduce the magnitude of riserbase pressure fluctuation due to hydrodynamic slugging up to 22%. The absorber enables larger valve opening for both hydrodynamic and severe slugging stabilisation. For severe slugging attenuation for example, a benefit of 9% reduction in riser base pressure was recorded for the case studied. This is of great benefit to the oil and gas industry since this translates to increased oil production. Slug attenuation index (SAI) and pressure benefit index (PBI), have been proposed to quantify the slug attenuation potential and the production benefits of the intermittent absorber respectively. The SAI and the PBI provided consistent results and methods for estimating the slug attenuation potential of the intermittent absorber concept. They could also be used to quantify the slug attenuation benefits of other slug mitigation techniques

Modelling of flows in vertical pipes and its application to multiphase flow metering at high gas content and to the prediction of well performance

Imperial Users onl

Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number

Characterization of microcellular plastics for weight reduction in automotive interior parts

The present PhD thesis is framed within the Industrial Doctorate Plan promoted by the Generalitat de Catalunya and has been developed in cooperation between the Universitat Politècnica de Catalunya-BarcelonaTech, the Centre Català del Plàstic, SEAT SA and Volkswagen AG. The research project has as main objective the characterization of microcellular plastics obtained by injection molding, motivated by a concern to reduce weight, cost and carbon footprint in automotive plastic parts. First, cylindrical bars and square plates made of Acrylonitrile-Butadiene-Styrene (ABS) and 20% Glass Fiber reinforced-Polypropylene (PP 20GF) were injection molded and foamed through the MuCell® technology. Shot volume was found as the most influencing parameter on cell structure and tensile and flexural properties. The effect of mold temperature and injection speed was secondary and not statistically significant for the mechanical performance. Tensile and flexural properties decreased almost linearly with the apparent density, whereas impact resistance was strongly reduced during foaming. Glass fibers contributed to partially overcome the loss of properties due to the reduction in density. Cells act as crack arrestors by blunting the crack tip. However, once the crack is propagating, cells acting as stress concentrators lead to a decrease in fracture toughness. Because of the low amount of blowing agent injected during the foaming process, no significant changes in the thermal properties were determined as compared to that of the solid counterpart. Simulation of the microcellular injection molding process with Moldex 3D® software and prediction models of the mechanical properties based on the apparent density and morphological characteristics provided a good approach to the experimental results. On the other hand, the Core Back tool technology was also employed in this study. By pulling the core and increasing the final thickness of the part, the apparent density decreased but the bending stiffness was greatly enhanced. Finally, a new alternative foaming technology, called IQ Foam® and developed by Volkswagen AG, was used to produce rectangular plates and compare their properties to that of the obtained by MuCell® process. By using a minimum amount of blowing agent, foamed plastic parts through IQ Foam® obtained through this process exhibited thicker solid skins and lower cell densities, but consequently higher mechanical properties. Additional benefits such as cost-effectiveness, easy-to-use and machine-independence are also offered by this new emerging technology.La presente tesis doctoral se enmarca dentro del Plan de Doctorats Industrials convocado por la Generalitat de Catalunya y se ha desarrollado como colaboración entre la Universitat Politècnica de Catalunya-BarcelonaTech, el Centre Català del Plàstic, SEAT SA y Volkswagen AG. El proyecto de investigación tiene como principal objetivo la caracterización de plásticos microcelulares, motivado por el interés en reducir peso, coste e impacto ambiental en piezas de plástico de automoción. En primer lugar, se obtuvieron mediante moldeo por inyección barras cilíndricas y placas cuadradas fabricadas con Acrilonitrilo-Butadieno-Estireno (ABS) y Polipropileno reforzado con un 20% de fibra de vidrio (PP 20GF), espumadas con la tecnología MuCell®. El volumen de dosificación es el parámetro más influyente sobre la estructura celular y las propiedades a tracción y a flexión. El efecto de la temperatura de molde y velocidad de inyección, en cambio, es secundario y no introduce variaciones estadísticamente significativas sobre el rendimiento mecánico. Las propiedades a tracción y flexión se reducen de manera prácticamente lineal con la disminución de densidad, mientras que la resistencia a impacto decrece drásticamente debido a la espumación. El efecto reforzante de las fibras de vidrio contribuye a compensar parcialmente la caída de propiedades debido a la reducción de densidad. Las celdas tienden a enromar el frente de grieta, retrasando así el inicio de propagación. Sin embargo, una vez la grieta comienza a propagar, las celdas actúan como concentradores de tensión provocando una disminución en la tenacidad a fractura. El reducido contenido de agente espumante inyectado durante el proceso de espumación no es suficiente para producir cambios en las propiedades térmicas en comparación con las del material macizo. La simulación del proceso de inyección microcelular con el software Moldex 3D® y los modelos de predicción de propiedades mecánicas basados en la densidad y características morfológicas proporcionaron valores cercanos a los obtenidos experimentalmente. Por otro lado, en este trabajo también se estudió el efecto de la tecnología de molde Core Back en combinación con el proceso de espumado mediante moldeo por inyección. A través del movimiento de la cavidad y el aumento del espesor final de la pieza inyectada, la densidad aparente se reduce al mismo tiempo que la rigidez a flexión se incrementa considerablemente. Finalmente, una nueva tecnología de espumación desarrollada por Volkswagen AG, llamada IQ Foam®, se utilizó para la inyección de placas rectangulares y la comparación de sus propiedades con las de placas análogas obtenidas mediante el proceso MuCell®. Mediante la utilización de un contenido mínimo de agente espumante, las placas espumadas con IQ Foam® exhibieron mayores espesores de piel y menores densidades celulares, y por tanto, propiedades mecánicas ligeramente superiores. Esta nueva tecnología ofrece también otras ventajas, como una menor inversión inicial, facilidad de operación y posibilidad de utilización en cualquier máquina de inyección convencional

Response of a slotted plate flow meter to horizontal two phase flow

The slotted plate flow meter has been widely tested as an obstruction flow meter during the past several years. It has been tested for both single-phase flows as well as for two-phase flows. Previous studies have revealed that the slotted plate flow meter is always better in performance and accuracy than the standard orifice plate flow meter. This study is primarily based on how a slotted plate responds to horizontal two-phase flow with air and water being used as the working fluids. The plates under consideration are those with beta ratios of 0.43 and 0.467. Experiments have been performed with six different configurations of the slotted plate test sections. The performances of the slotted plate flow meters will be compared to that of a standard orifice plate flow meter and then with a venturi. The effects of varying the upstream quality of the two-phase flow on the differential pressure and the coefficient of discharge of the slotted plates, the standard orifice plate and the venturi will be evaluated. Response characteristics at low differential pressures will be investigated. Tests for repeatability will be performed by studying the effects of the gas Reynolds number and the upstream quality on the differential pressure. The differential pressures across the slotted plates, the standard orifice plate and the venturi will be compared. Reproducibility will be evaluated by comparing the data obtained from all six different configurations. One of the main objectives of this study is to arrive at the best suitable procedure for accurately measuring the flow rate of two-phase flow using the slotted plate flow meter