Electrical treatment of waxy model oil to improve its cold mobility

Wax precipitation at low temperatures can pose significant flow assurance challenges during offshore transportation of waxy crude oils. The sharp increase of viscosity due to wax precipitation increases the pressure drop and thus raises the capital and operating cost of transportation. Conventional methods of lowering the viscosity of waxy oils include adding chemicals or externally heating the pipeline, both of which are energy-costly and carbon-intensive. Therefore, there is a need to develop economic and eco-friendly solutions to improve the cold mobility of waxy oils. Previous studies have demonstrated that the electrical treatment of waxy crude oil can significantly lower its viscosity at a relatively low energy cost. Previous research mainly focused on demonstrating the electrorheological behaviors of waxy crude oils, and it has been believed that charged particles in the crude oils, such as resins and asphaltenes, play a critical role in reducing the viscosity of waxy crude oils under electric fields. It remains unknown the performance of electrical treatment on waxy oils in the absence of resins and asphaltenes. To fill in this gap, in this research, the electrorheological responses of waxy model oil systems consisting of mineral oil, decane, and paraffin wax were investigated by a DHR-20 rheometer equipped with an Electro-Rheology accessory. The sample’s viscosity was monitored in three consecutive 10-minute stages: before, during, and after the application of DC electrical fields ranging from 0 to 3.5 kV/mm. Significant viscosity reductions were observed in nearly all model systems, and the maximum viscosity reduction of 82.9% was obtained at 22 °C by applying a 3.5 kV/mm electric field. The magnitude of viscosity reduction depends on several factors, including electric field strength, temperature, and the amount of precipitated wax. Furthermore, the addition of 1wt% n-decane was found to significantly enhance the effectiveness of the electric treatment, increasing the viscosity reduction by nearly 40%. These findings challenge the widely accepted theories in the literature that resins and asphaltene play a critical role in reducing the viscosity of waxy crude oil by electrical treatments and could potentially aid future research in better understanding the underlying mechanisms behind the negative electric effects on the viscosity of waxy crude oils.Petroleum and Geosystems Engineerin

Jet trails and Mach cones: The interaction of microquasars with the ISM

A sub-set of microquasars exhibit high peculiar velocity with respect to the local standard of rest due to the kicks they receive when being born in supernovae. The interaction between the radio plasma released by microquasar jets from such high-velocity binaries with the ISM must lead to the production of trails and bow shocks similar to what is observed in narrow-angle tailed radio galaxies and pulsar wind nebulae. We present a set of numerical simulations of this interaction that illuminate the long term dynamical evolution and the observational properties of these microquasar bow shock nebulae and trails. We find that this interaction always produces a structure that consists of a bow shock, a trailing neck, and an expanding bubble. Using our simulations to model emission, we predict that the shock surrounding the bubble and the neck should be visible in H{\alpha} emission, the interior of the bubble should be visible in synchrotron radio emission, and only the bow shock is likely to be detectable in X-ray emission. We construct an analytic model for the evolution of the neck and bubble shape and compare this model with observations of X-ray binary SAX J1712.6-3739.Comment: 33 pages, 13 figures, 1 table; Accepted to Ap

Design, Modeling and Control of a 3D Printed Monolithic Soft Robotic Finger with Embedded Pneumatic Sensing Chambers

IEEE This paper presents a directly 3D printed soft monolithic robotic finger with embedded soft pneumatic sensing chambers (PSC) as position and touch sensors. The monolithic finger was fabricated using a low-cost and open-source fused deposition modeling (FDM) 3D printer that employs an off-the-shelf soft and flexible commercially available thermoplastic polyurethane (TPU). A single soft hinge with an embedded PSC was optimized using finite element modeling (FEM) and a hyperelastic material model to obtain a linear relationship between the internal change in the volume of its PSC and the corresponding input mechanical modality, to minimize its bending stiffness and to maximize its internal volume. The soft hinges with embedded PSCs have several advantages, such as fast response to very small changes in their internal volume (~0.0026ml/°), linearity, negligible hysteresis, repeatability, reliability, long lifetime and low power consumption. Also, the flexion of the soft robotic finger was predicted using a geometric model for use in real-time control. The real-time position and pressure/force control of the soft robotic finger were achieved using feedback signals from the soft hinges and the touch PSC embedded in the tip of the finger. This study contributes to the development of seamlessly embedding optimized sensing elements in the monolithic topology of a soft robotic system and controlling the robotic system using the feedback data provided by the sensing elements to validate their performance

Flame retardant nylon 6 nanocomposite fibers : processing and characterization

One type of engineering thermoplastic polymers that has significant commercial application is nylon. However, flammability and melt dripping is a major problem for polymers like nylon 6 because it can cause fire to spread to other flammable objects and escalate the fire in a short amount of time. Although high performance inherently flame-retardant (FR) fibers have been discovered and various durable FR finishes for nylon have been developed, cost-effective flame retardant nylon and nylon blend fabrics remain a challenge. The goal of this research is to develop non-drip inherently FR nylon 6 fibers as a cost-effective alternative for use in high volume FR fabrics. In this dissertation, a cost effective alternative of producing non-drip inherently flame retardant nylon 6 fibers with balanced performances was developed based on polymer nanocomposite systems incorporating intumescent FR and nanoclay additives. Nanoclay was added to the system to reduce FR particle loading and capitalize on the synergistic effect between nanoclay and intumescent additives. Adequate dispersion of the additives with exfoliation of the nanoclay platelets was observed using TEM and XRD. Injection molding was used as a tool for screening the performance of the nanocomposite formulations in bulk form before the fiber spinning process. Results of injection molded FR PA6 nanocomposites suggest that although a good FR performance could be achieved, mechanical properties, especially ductility, were significantly compromised. To solve this problem, rubber toughening was achieved using a thermoplastic elastomer with significant success in recovering material ductility without compromising FR performance. Ultra-sonication of the FR additives prior the fiber spinning could effectively reduce the FR particle size distribution. Single fiber tensile tests show that PA6/FR/elastomer/nanoclay formulation is able to improve both the tenacity and elongation at break from the original PA6/FR system. Moreover, flammability tests suggest that the nanocomposite FR fibers have significantly lower heat release properties and are able to retain a fibrous shape after combustion indicating the non-dripping property. Therefore, our experiments have yielded improved non-drip FR properties in PA6 through the infusion of nanoclay and non-halogenated intumescent particles (FR) via co-rotating twin-screw extrusion. One major implication of these results is that with the new non-drip FR nylon 6 fiber, it would be possible to achieve blends with higher nylon content than customary and not compromise the FR performance of the fabric, thus providing a cost effective solution for high-volume applications.Materials Science and Engineerin

Effects of injection pressure variation on mixing in a cold supersonic combustor with kerosene fuel

Abstract: Spray jet in cold kerosene-fueled supersonic flow has been characterized under different injection pressures to assess the effects of the pressure variation on the mixing between incident shock wave and transverse cavity injection. Based on the real scramjet combustor, a detailed computational fluid dynamics model is developed. The injection pressures are specified as 0.5, 1.0, 2.0, 3.0 and 4.0 MPa, respectively, with the other constant operation parameters (such as the injection diameter, angle and velocity). A three dimensional Couple Level Set & Volume of Fluids approach incorporating an improved Kelvin-Helmholtz & Rayleigh-Taylor model is used to investigate the interaction between kerosene and supersonic air. The numerical simulations primarily concentrate on penetration depth, span expansion area, angle of shock wave and sauter mean diameter distribution of the kerosene droplets with/without evaporation. Validation has been implemented by comparing the calculated against the measured in literature with good qualitative agreement. Results show that the penetration depth, span-wise angle and expansion area of the transverse cavity jet are all increased with the injection pressure. However, when the injection pressure is further increased, the value in either penetration depth or expansion area increases appreciably. This study demonstrates the feasibility and effectiveness of the combination of Couple Level Set & Volume of Fluids approach and an improved Kelvin-Helmholtz & Rayleigh-Taylor model, in turn providing insights into scramjet design improvement

Dystrophin conferral using human endothelium expressing HLA-E in the non-immunosuppressive murine model of Duchenne muscular dystrophy

Human leukocyte antigen (HLA)-E is a non-classical major histocompatibility complex class I (Ib) molecule, which plays an important role in immunosuppression. In this study, we investigated the immunomodulating effect of HLA-E in a xenogeneic system, using human placental artery-derived endothelial (hPAE) cells expressing HLA-E in a mouse model. In vitro cell lysis analysis by primed lymphocytes in combination with siRNA transfection showed that HLA-E is necessary for inhibition of the immune response. Similarly, in vivo cell implantation analysis with siRNA-mediated down-regulation of HLA-E demonstrates that HLA-E is involved in immunosuppression. As hPAE cells efficiently transdifferentiate into myoblasts/myocytes in vitro, we transplanted the cells into mdx mice, a model of Duchenne muscular dystrophy. hPAE cells conferred dystrophin to myocytes of the ‘immunocompetent' mdx mice with extremely high efficiency. These findings suggest that HLA-E-expressing cells with a myogenic potential represent a promising source for cell-based therapy of patients with muscular dystrophy