Operating Data (operating + data)

Distribution by Scientific Domains

Selected Abstracts

A study on a new AVR parameter tuning concept using on-line measured data with the real-time simulator

Joong-Moon Kim
Abstract Automatic voltage regulator (AVR) parameter tuning for voltage control of power system generators has generally been performed with the analytic methods and the simulation methods, which mostly depend on off-line linear mathematical models of power system. However, due to the nonlinear nature of power system, the mathematical models of the excitation system may not be correct. So the excitation control system performances with the parameter set that is tuned by using the mathematical model, may not be appropriate for some operating conditions. This paper presents an AVR parameter tuning method using on-line measured data of the excitation control system with parameter optimization technique. As this method utilizes on-line operating data, it can overcome the limitation of model uncertainty problems of conventional method. To validate the proposed tuning concept, a scaled model excitation system is connected to the real-time power system simulator, and the proposed tuning concept is tested. Copyright 2006 John Wiley & Sons, Ltd. [source]

Evaluation of controller performance,use of models derived by subspace identification

S. Bezergianni
Abstract A new approach is presented for the estimation of the controller, process, and disturbance models necessary for the calculation of the relative variance index, which was introduced in an earlier paper (Control Eng. Practice 2000; 8:791,797), for the performance of SISO controllers. It involves the use of dynamically, sufficiently rich segments from the normal operating data and the use of the subspace identification technique to estimate the systems mentioned above. This approach improves the estimation accuracy of the performance index in relation to the method presented previously. The estimated models enable the comparison of the present controller performance with that of optimally tuned PI or IMC controllers. This helps identify the potential benefits of either retuning or redesigning the assessed controller. Copyright 2002 John Wiley & Sons, Ltd. [source]

Exergy analysis of a coal-based 210 MW thermal power plant

S. Sengupta
Abstract In the present work, exergy analysis of a coal-based thermal power plant is done using the design data from a 210 MW thermal power plant under operation in India. The entire plant cycle is split up into three zones for the analysis: (1) only the turbo-generator with its inlets and outlets, (2) turbo-generator, condenser, feed pumps and the regenerative heaters, (3) the entire cycle with boiler, turbo-generator, condenser, feed pumps, regenerative heaters and the plant auxiliaries. It helps to find out the contributions of different parts of the plant towards exergy destruction. The exergy efficiency is calculated using the operating data from the plant at different conditions, viz. at different loads, different condenser pressures, with and without regenerative heaters and with different settings of the turbine governing. The load variation is studied with the data at 100, 75, 60 and 40% of full load. Effects of two different condenser pressures, i.e. 76 and 89 mmHg (abs.), are studied. Effect of regeneration on exergy efficiency is studied by successively removing the high pressure regenerative heaters out of operation. The turbine governing system has been kept at constant pressure and sliding pressure modes to study their effects. It is observed that the major source of irreversibility in the power cycle is the boiler, which contributes to an exergy destruction of the order of 60%. Part load operation increases the irreversibilities in the cycle and the effect is more pronounced with the reduction of the load. Increase in the condenser back pressure decreases the exergy efficiency. Successive withdrawal of the high pressure heaters show a gradual increment in the exergy efficiency for the control volume excluding the boiler, while a decrease in exergy efficiency when the whole plant including the boiler is considered. Keeping the main steam pressure before the turbine control valves in sliding mode improves the exergy efficiencies in case of part load operation. Copyright 2006 John Wiley & Sons, Ltd. [source]

Overall efficiency evaluation of commercial distillation columns with valve and dualflow trays

AICHE JOURNAL, Issue 9 2010
T. L. Domingues
Abstract The main objective of this work is to establish appropriated ways for estimating the overall efficiencies of industrial distillation columns with valve trays with downcomer and dualflow trays. The knowledge of efficiencies has fundamental importance in the design and performance evaluation of distillation columns. Searching in the literature, a tree of alternatives was identified to compose the tray efficiency model, depending on the mass transfer models, the liquid distribution and vapor flow models on the tray, the liquid entrainment model, the multicomponent mixture equilibrium model, the physical properties models, the height of froth on the tray model and the efficiency definition. In this work, different methods to predict the overall efficiency of distillation columns with valve and dualflow trays were composed and compared with data from three commercial distillation columns under different operating conditions. The models were inserted in the Aspen Plus 12.1 simulator, in Fortran language, together with tray geometrical data, fluid properties and operating data of the distillation columns. For each column, the best thermodynamic package was chosen by checking the temperature profile and overhead and bottom compositions obtained via simulation against the corresponding actual data of industrial columns. A modification in the fraction of holes evaluation that is jetting parameter of the Garcia's hydraulic model of dispersion above the tray was proposed. This modification produced better results than the original model to predict the fraction of holes that are jetting and in the efficiency of dualflow trays and similar results to Garcia model in the efficiency evaluation of valve trays. 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Nonstationary fault detection and diagnosis for multimode processes

AICHE JOURNAL, Issue 1 2010
Jialin Liu
Abstract Fault isolation based on data-driven approaches usually assume the abnormal event data will be formed into a new operating region, measuring the differences between normal and faulty states to identify the faulty variables. In practice, operators intervene in processes when they are aware of abnormalities occurring. The process behavior is nonstationary, whereas the operators are trying to bring it back to normal states. Therefore, the faulty variables have to be located in the first place when the process leaves its normal operating regions. For an industrial process, multiple normal operations are common. On the basis of the assumption that the operating data follow a Gaussian distribution within an operating region, the Gaussian mixture model is employed to extract a series of operating modes from the historical process data. The local statistic T2 and its normalized contribution chart have been derived for detecting abnormalities early and isolating faulty variables in this article. 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Analysis of management actions, human behavior, and process reliability in chemical plants.

I. impact of management actions
Abstract While management and engineering actions have a significant impact on process reliability, these factors have received too little attention in calculating plant risks. In this work, the focus is on understanding and modeling the influence of human behavior patterns on plant safety in two settings. The first, introduced in Part I, involves a framework to estimate the impacts of management and engineering decisions, process operator performance, and processing equipment operations on the failure state of chemical plants. As examples, the impacts of poor training, maintenance problems, operator inabilities, control system failures, and excessive feed quantities, on failure states are studied. The management and engineering team and the operators are found to have significant impacts on process reliability. While the theoretical framework introduced herein is illustrated using hypothetical plant data, it should provide a basis for more quantitative safety analyses. Attempts to obtain operating data in industrial plants for validation of the framework were unsuccessful because of confidentiality and liability issues associated with industrial data. 2007 American Institute of Chemical Engineers Process Saf Prog, 2007 [source]

FCCU simulation based on first principle and artificial neural network models

Maria Mihe
Abstract A first principle model has been developed for the reactor,regenerator system based on construction and operating data from an industrial fluid catalytic cracking unit (FCCU). The first principle model takes into account the main FCCU subsystems: reactor riser, regenerator, stripper, catalyst circulation lines, air blower, wet gas compressor and main fractionator. A five-lump kinetic scheme has been considered for the reactions taking place in the reactor riser. Subsequently, an artificial neural network (ANN) model has been built for the complex FCCU system. The dynamic simulator, based on the previously developed first principle model, served as the source of reliable data for ANN design, training and testing. The ANN developed model was successfully trained and tested. Comparison between first principle and neural network based model leads to a very good match between the two models. Results show the substantial reduction of the computation time featured by the ANN model compared to the first principle model, demonstrating its potential use for real-time implementation in model-based control algorithms. Copyright 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Definition and validation of operating equations for poly(vinyl alcohol)-poly(lactide-co-glycolide) microfiltration membrane-scaffold bioreactors

R.J. Shipley
Abstract The aim of this work is to provide operating data for biodegradable hollow fiber membrane bioreactors. The physicochemical cell culture environment can be controlled with the permeate flowrate, so this aim necessitates the provision of operating equations that enable end-users to set the pressures and feed flowrates to obtain their desired culture environment. In this paper, theoretical expressions for the pure water retentate and permeate flowrates, derived using lubrication theory, are compared against experimental data for a single fiber poly(vinyl alcohol),poly(lactide-co-glycolide) crossflow module to give values for the membrane permeability and slip. Analysis of the width of the boundary layer region where slip effects are important, together with the sensitivity of the retentate and permeate equations to the slip parameter, show that slip is insignificant for these membranes, which have a mean pore diameter of 1.1,m. The experimental data is used to determine a membrane permeability, of k,=,1.86,,10,16,m2, and to validate the model. It was concluded that the operating equation that relates the permeate to feed ratio, c, lumen inlet flowrate, Ql,in, lumen outlet pressure, P1, and ECS outlet pressure, P0, is (1) where A and B are constants that depend on the membrane permeability and geometry (and are given explicitly). Finally, two worked examples are presented to demonstrate how a tissue engineer can use Equation (1) to specify operating conditions for their bioreactor. Biotechnol. Bioeng. 2010;107: 382,392. 2010 Wiley Periodicals, Inc. [source]

Endoscopic transanal resection of rectal tumours using a urological resectoscope , still has a role in selected patients

G. C. Beattie
Abstract Introduction Transanal resection of rectal villous adenomas or adenocarcinomas can be carried out using various modalities such as operative excision, fulguration, laser coagulation or cryotherapy. Transanal endoscopic microsurgery is currently not widely available. Transanal resection can provide effective palliation for locally advanced rectal tumours in patients unfit for abdomino-perineal excision of rectum. A urological resectoscope can be safely and repeatedly used to resect advanced primary or locally recurrent rectal rumours by colorectal surgeons with urological expertise. This study reports our experience of treating rectal lesions with endoscopic transanal resection (ETAR) using the urological resectoscope. Methods Patients were identified from one surgeons' prospectively collected operating data. Charts were retrieved and reviewed. Results Over a 13-year period a total of 43 ETAR procedures were carried out in 20 patients (11 males; mean age 74 years; range 54,92 years) using the urological resectoscope. Twelve (60%) patients had a single resection; 8 (40%) patients required more than one resection; the mean number of procedures per patient was 2.2 (range1,8). The median interval between resections for recurrent disease (excluding planned repeat resections) was 340 days (range 168,2337 days). Histopathology revealed rectal adenoma (with varying degrees of dysplasia) in 11 (55%) patients and adenocarcinoma in 9 (45%). The majority (30; 70%) of resections were carried out in patients with benign disease, with 13 (30%) in patients with rectal adenocarcinoma. Mean operating time per resection was 25 min. Thirteen (30%) resections were carried out under spinal anaesthetic. There was no procedure related mortality. There were no cases of haemorrhage, rectal perforation, ,TUR syndrome' or pelvic sepsis. No patients with benign disease subsequently developed an invasive carcinoma. Conclusions Accepting that this technique provides limited histopathological information regarding extent of resection and tumour clearance, our experience demonstrates that ETAR of rectal tumours using the urological resectoscope can provide a minimally invasive, effective and safe means of treating and palliating patients with benign and malignant rectal disease. There remains a place for this technique in selected patients. [source]