Finite-time active fuzzy sliding mode approach for deep surge control in nonlinear disturbed compressor system with uncertainty in charactrisitic curve

In this paper, a novel active control approach is designed for surge instability in the compressor system using the finite-time fuzzy sliding mode scheme. The primary novelty of this study lies in the development of a finite-time fuzzy sliding mode control for the surge instability in a compressor system in the presence of disturbance and uncertainty in the characteristic curve of the compressor and also throttle valve. To ensure the stability of the closed-loop system in Lyapunov\u27s concept, a finite time active control method is proposed based on fuzzy estimation method and robust adaptive and sliding mode methods. Achieving finite time stability and rapid elimination of deep surge instability occurs through a fast sliding mode design, while fuzzy and adaptive techniques are used to estimate uncertainty and nonlinear terms, as well as to obtain optimal estimation weights. The simulation results in MATLAB environment and comparison show that the suggested method provides better quality control in terms of surge suppression, robustness, and overcoming uncertainty and disturbance effects

Model Predictive Anti-Surge Control of Centrifugal Compressors with Variable-Speed Drives

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Performance analysis of deterministic, min-max and multi-stage NMPC applied to a subsea gas compression system

In recent years, subsea technologies have become more reliable. New projects emerged and an increase of investment in the area is expected in the following years. However, subsea installations are becoming more complex and smart decision making controllers are necessary to reduce operational costs and increase process reliability. Besides, the presence of uncertainties makes the development of controllers that can handle operation in an uncertain environment imperative. A prominent subsea technology is the subsea compression, which has been recently delivered in the North Sea. Åsgard eld compression system design was based on topside design. Therefore, surge avoidance strategy is necessary in order to operate without major issues in presence of disturbances and uncertainties. If surge occurs, compression system operation is strongly a ected, leading even to compressors breakage. Thus, in this work, Nonlinear Model Predictive Controls (NMPC), such as deterministic, o ine min-max and multi-stage were employed to a subsea compression system to evaluate controllers performance and closed-loop robustness in an environment with unknown disturbances a ecting upstream pressure. For performance assessment, indicators that consider set-point tracking, constraint violation, gas production, energy consumption, and production e ciency were employed. Deterministic NMPC was the most e cient controller, but constraint violation was detected. Although o ine min-max operation managed to handle constraint violation, it proved to be overly conservative. Multi-stage NMPC controller was able to also handle constraint violation, while being less conservative than o ine min-max NMPC.Recentemente, tecnologias subsea têm se tornado mais con áveis. Novos projetos foram elaborados e, nos próximos anos, um grande volume de investimentos é esperado na área. No entanto, instalações subsea têm se tornado cada vez mais complexas e controladores capazes de tomar decisões de forma inteligente são necessários para redução de custos e aumento da con abilidade. No entanto, devido à presença de incertezas em operações subsea, novos controladores capazes de operar em um ambiente incerto devem ser desenvolvidos. No Mar do Norte, uma tecnologia promissora de compressão subsea de gás começou recentemente a operar. No campo de Asgard, o projeto do sistema de compressão foi baseado em instalações topside. Devido a isso, estratégias anti-surge são necessárias para que o sistema possa operar sem maiores problemas frente à presença de perturbações e incertezas. Caso a operação entre em surge, o sistema de compressão pode ser afetado ocasionando a quebra do compressor. Devido a isso, foram avaliados o desempenho e a robustez de um sistema de compressão subsea quando controlado por um NMPC determinístico, o ine min-max e multi-estágio. Indicadores que levam em consideração o desempenho do controle de set-point, violação de restrições, produção de gás, consumo energético e e ciência na produção foram utilizados para avaliação dos controladores. O NMPC determinístico foi a solução mais e ciente, no entanto violações nas restrições foram detectadas. Apesar do controlador min-max conseguir impedir que restrições sejam violadas, ele teve um desempenho conservativo. Já o controlador NMPC multiestágio também conseguiu lidar com a restrição do processo, apresentando um desempenho menos conservativo que a solução NMPC o ine min-max

Development and Application of a Digital Twin for Chiller Plant Performance Assessment

As the complexity of industrial equipment continues to increase, the management of the individual machines and integrated operations becomes difficult without computer tools. The availability of streaming data from manufacturing floors, plant operations, and deployed fleets can be overwhelming to analyze, although it provides opportunities to improve performance. The use of dedicated monitoring systems in the plant and field to troubleshoot machinery can be integrated within a product lifecycle management (PLM) architecture to offer greater features. PLM offers virtual processes and software tools for the design, analysis, monitoring, and support of engineering systems and products. Within this paradigm, a digital twin can estimate system behavior based on the assembled physical models and the operating data for preventive maintenance efforts. PLM software can store computer-aided-design, computer-aided-engineering, advanced manufacturing, and data in cloud form for remote access. Integrating physical and performance data into a single database provides flexibility and adaptability while allowing distant commanding and health monitoring of dynamic systems. The recent attention on global warming, and the minimization of energy consumption can be partially addressed by examining those economic sectors that use large quantities of electric power. Across the United States, heating, ventilation, and air conditioning (HVAC) systems use a collective $14 Billion of resources to control the temperature of commercial and residential spaces. A typical commercial HVAC system consists of a chiller plant, water pumps for fluid circulation, multiple heat exchangers, and iii forced air blowers. In this research project, a digital twin is created for a single compressor chilled water-based HVAC system using a multi-disciplinary CAE software package. The system level models are assembled to describe a 1400 ton chiller located in the East-side chiller plant on the Clemson University (Clemson, SC) campus. The dynamic models that estimate the fluid pressures, temperatures, and flow rates, as well as the electrical and mechanical power consumption, are validated against the operating data streamed through the OptiCX System. To demonstrate the capabilities of this digital twin tool in a preventive maintenance mode, various degradations are virtually investigated in the chiller plant\u27s components. The mechanical pump efficiency, electric pump motor friction, pipe blockage, air flow rate sensor, and the expansion valve opening were degraded by 3% to 5%, which impacted component behavior and system performance. The analysis of these predicted plant signals helped to establish preventive maintenance thresholds on these components, which should promote improved plant reliability. A digital twin provides additional flexibility than stand-alone monitoring technologies due to the capability of simulating customized scenarios for analyzing failure-prone conditions and overall equipment effectiveness (OEE). The PLM-based digital twin offers a design and prognostic platform for HVAC systems

Development of dry coal feeders

Design and fabrication of equipment of feed coal into pressurized environments were investigated. Concepts were selected based on feeder system performance and economic projections. These systems include: two approaches using rotating components, a gas or steam driven ejector, and a modified standpipe feeder concept. Results of development testing of critical components, design procedures, and performance prediction techniques are reviewed

Modeling Axisymmetric Centrifugal Compressor Characteristics from First Principles

Turbochargers are a vital component for aiding engine manufacturers in meeting the latest emissions standards. However, their range of operation is limited for low mass flows by compressor surge. Operation in surge results in pressure and mass flow oscillations that are often damaging to the compressor and its installation. Since surge is a highly complex flow regime, full unsteady 3D models are generally too computationally expensive to run. The majority of current low-dimensional surge models use a cubic compressor characteristic that needs to be fitted to experimental data. Therefore, each time a compressor is studied using these models, costly experimental testing is required.In this paper, a new technique for obtaining an axisymmetric centrifugal compressor characteristic is presented. This characteristic is built using the equations of mass, momentum and energy from first principles in order to provide a more complete model than those currently obtained via experimental data. This approach enables us to explain the resulting cubic-like shape of the characteristic and hence to identify impeller inlet stall as a route into surge. The characteristic is used within a quasi-steady, map-based surge model in order to demonstrate its ability to predict the onset of surge while only providing geometric data as input. Validation is provided for this model by discussion of the qualitative flow dynamics and a good fit to experimental data, especially for low impeller speeds and pressure ratios

Engineering study of the rotary-vee engine concept

The applicable thermodynamic cycle and performance considerations when the rotary-vee mechanism is used as an internal combustion (I.C.) heat engine are reviewed. Included is a simplified kinematic analysis and studies of the effects of design parameters on the critical pressures, torques and parasitic losses. A discussion of the principal findings is presented