Venturi multiphase flow measurement based active slug control

Riser slug flow poses a significant challenge to offshore oil production systems, most especially for oil fields in their later life. Active control of slugging through choking has been proven a practical approach in eliminating riser slug flow in oil production pipeline-riser systems. However, existing conventional active slug control systems may reduce oil production significantly due to excessive over choking. Again, some of the existing active slug flow control systems rely on seabed measurements, which are difficult to maintain, costly to install, unreliable, and seldom readily available. This study is an experimental investigation of the feasibility of active riser slug control by taking topside differential pressure measurement from the inlet of the venturi flow meter to the throat. Experimental results indicate that under active slug flow control, the system was able to eliminate slug flow at a higher valve opening when compared to manual choking. A valve opening of 24% with riser base pressure at 2.85 bar from open loop unstable of 23% was recorded, which is superior to manual choking which maintained flow stability up to 21% valve opening with riser base pressure of 3.8 bar

Statistical process monitoring of a multiphase flow facility

Industrial needs are evolving fast towards more flexible manufacture schemes. As a consequence, it is often required to adapt the plant production to the demand, which can be volatile depending on the application. This is why it is important to develop tools that can monitor the condition of the process working under varying operational conditions. Canonical Variate Analysis (CVA) is a multivariate data driven methodology which has been demonstrated to be superior to other methods, particularly under dynamically changing operational conditions. These comparative studies normally use computer simulated data in benchmark case studies such as the Tennessee Eastman Process Plant (Ricker, N.L. Tennessee Eastman Challenge Archive, Available at 〈http://depts.washington.edu/control/LARRY/TE/download.html〉 Accessed 21.03.2014). The aim of this work is to provide a benchmark case to demonstrate the ability of different monitoring techniques to detect and diagnose artificially seeded faults in an industrial scale multiphase flow experimental rig. The changing operational conditions, the size and complexity of the test rig make this case study an ideal candidate for a benchmark case that provides a test bed for the evaluation of novel multivariate process monitoring techniques performance using real experimental data. In this paper, the capabilities of CVA to detect and diagnose faults in a real system working under changing operating conditions are assessed and compared with other methodologies. The results obtained demonstrate that CVA can be effectively applied for the detection and diagnosis of faults in real complex systems, and reinforce the idea that the performance of CVA is superior to other algorithms

Active disturbance rejection control of a longitudinal tunnel ventilation system

This paper proposes an innovative approach for controlling pollutant release in a long-distance tunnel via longitudinal ventilation. Enhanced by an active disturbance rejection control (ADRC) method, a ventilation controller is developed to regulate the forced air ventilation in a road tunnel. As a result, the pollutants (particulate matter and carbon monoxide) are reduced by actively regulating the air flow rate through the tunnel. The key contribution of this study lies in the development of an extended state observer that can track the system disturbance and provide the system with compensation via a nonlinear state feedback controller equipped by the ADRC. The proposed method enhances the disturbance attenuation capability in the ventilation system and keeps the pollutant concentration within the legitimate limit in the tunnel. In addition to providing a safe and clean environment for passengers, the improved tunnel ventilation can also achieve better energy saving as the air flow rate is optimized

Locally Resonant Metagrating by Elastic Impedance Modulation

The optical and acoustic metagratings have addressed the limitations of low-efficiency wave manipulation and high-complexity fabrication of metamaterials and metasurfaces. In this research, we introduce the concept of elastic metagrating and present the theoretical and experimental demonstration of locally resonant elastic metagrating (LREM). Remarkably, the LREM, with dimensions two orders of magnitude smaller than the relevant wavelength, overcomes the size limitations of conventional metagratings and offers a unique design paradigm for highly efficient wave manipulation with an extremely compact structure in elastic wave systems. Based on a distinctive elastic impedance engineering with hybridization of intrinsic evanescent waves, the proposed LREM achieves wide-angle perfect absorption. This tackles a fundamental challenge faced by all elastic metastructures designed for wave manipulation, which consists in the unavoidable vibration modes in finite structures hindering their implementations in real-world applications

Mechanism of tissue transglutaminase upregulation and its role in ovarian cancer metastasis

Indiana University-Purdue University Indianapolis (IUPUI)Ovarian cancer (OC) is a lethal disease due to metastasis and chemoresistance. Our laboratory previously reported that tissue transglutaminase (TG2) is overexpressed in OC and enhances OC peritoneal metastasis. TG2 is a multifunctional protein which catalyzes Ca2+-dependent cross-linking of proteins. The purpose of this study was to explore the mechanism by which TG2 is upregulated in OC and its role in OC progression. We demonstrated that transforming growth factor (TGF)-β1 is secreted in the OC milieu and regulates the expression and function of TG2 primarily through the canonical Smad signaling pathway. Increased TG2 expression level correlates with a mesenchymal phenotype of OC cells, suggesting that TGF-β1 induced TG2 promotes epithelial-to-mesenchymal transition (EMT). TG2 induces EMT by negatively regulating E-cadherin expression. TG2 modulates E-cadherin transcriptional suppressor Zeb1 expression by activating NF-κB complex, which leads to increased cell invasiveness in vitro and tumor metastasis in vivo. The N-terminal fibronectin (FN) binding domain of TG2 (tTG 1-140), lacking both enzymatic and GTPase function, induced EMT in OC cells, suggesting the interaction with FN involved in EMT induction. A TGF-β receptor kinase inhibitor, SD-208, blocked TGF-β1 induced TG2 upregulation and EMT in vitro and tumor dissemination in vivo, which confirms the link between TGF-β1 and TG2 in EMT and tumor metastasis. TG2 expression was correlated with the number and size of self-renewing spheroids, the percentage of CD44+CD117+ ovarian cancer stem cells (CSCs) and with the expression level of stem cell specific transcriptional factors Nanog, Oct3/4, and Sox2. These data suggest that TG2 is an important player in the homeostasis of ovarian CSCs, which are critical for OC peritoneal metastasis and chemoresistance. TG2 expression was also increased in CSCs isolated from human ovarian tumors, confirming the implication of TG2 in CSCs homeostasis. Further, we demonstrated that TG2 protects OC cells from cisplatin-induced apoptosis by regulating NF-κB activity. We proposed a model whereby TGF-β-inducible TG2 modulates EMT, metastasis, CSC homeostasis and chemoresistance in OC. These findings contribute to a better understanding of the mechanisms of OC metastasis modulated by TG2

Canonical variate analysis for performance degradation under faulty conditions

Condition monitoring of industrial processes can minimize maintenance and operating costs while increasing the process safety and enhancing the quality of the product. In order to achieve these goals it is necessary not only to detect and diagnose process faults, but also to react to them by scheduling the maintenance and production according to the condition of the process. The objective of this investigation is to test the capabilities of canonical variate analysis (CVA) to estimate performance degradation and predict the behavior of a system affected by faults. Process data was acquired from a large-scale experimental multiphase flow facility operated under changing operational conditions where process faults were seeded. The results suggest that CVA can be used effectively to evaluate how faults affect the process variables in comparison to normal operation. The method also predicted future process behavior after the appearance of faults, modeling the system using data collected during the early stages of degradation

The hydrodynamics of two-phase flows in the injection part of a conventional ejector

The characteristics of two-phase flow through a ‘conventional’ convergent-nozzle in an entrainment chamber of an ejector apparatus are described in this paper. A unique data set comprising 350 data points was generated in an air-water horizontal test-rig. Two sets of flow conditions were established, the first one including high liquid - low gas fluids with void fractions less than 0.55, and the second one involving high gas - low liquid fluids with void fractions greater than 0.75. All considered flow-rates lied within the sub-critical flow region. Two-phase flow pressure drop multiplier based empirical correlations were developed to estimate the total mass flow-rates. In the high liquid region, Morris (1985) correlation was modified, resulting in less than 10% error. In the high gas region, two new correlations were proposed, showing less than 10% and 15% of errors, respectively. The established empirical correlations were related to other available multipliers for different geometric configurations including a Venturi, an orifice plate, a gate valve, and a globe valve and were compared to 20 other void fraction correlations. The Chisholm (1983b) and Huq and Loth (1992) correlations showed the highest similarities to the ones proposed for the high liquid and high gas regions, respectively

Study on transformation of cowpea trypsin inhibitor gene into cauliflower (Brassica oleracea L. var. botrytis)

Cowpea Trypsin Inhibitor (CpTI) gene was transferred into cauliflower by agrobacterium-mediated transformation method, and 14 transgenic cauliflower plants were obtained. Cotyledons and hypocotyls were used as explants. The putative transformants were assayed by PCR and Southern blotting analysis. The results indicated that CpTI gene was transferred into cauliflower successfully. The result of preliminary insect-resistant assay showed that the transgenic plants were more resistant to Pieris rapae than non-transgenic plants. Key Words: African Journal of Biotechnology Vol.4(1) 2005: 45-4