Design Of Real Systems Research Articles

A hydrate-based post-combustion capture system integrated with cold energy: Thermodynamic analysis, process modeling and energy optimization

Carbon capture is a crucial part of global warming mitigation. Carbon capture via clathrate hydrate is an attractive approach due to its high capture capacity, high carbon dioxide purity, water-based benign process, ease of recycling, and robustness to contaminants. In this work, we propose a two-stage hydrate-based carbon dioxide separation system integrated with cold energy for carbon capture from flue gases. A thermodynamic cycle consisting of two sub-cycles was constructed to simulate the process. Operating conditions were optimized within the range of 274.15–282.15 K and 0.1–28.04 MPa, resulting in the lowest electricity consumption of 2.22 MJ/kg CO2 with 95.24 mol% CO2 purity and 65.97 % CO2 recovery. A higher CO2 recovery rate can be achieved by recycling the residual gas of Sub-cycle 2. Gas compression to the high operating pressure (16.01 MPa) is the major contributor to electricity consumption. By incorporating 100 % expansion work recovery from the high-pressure gases, the electricity consumption can be reduced to 0.43 MJ/kg CO2 (i.e., 0.119 kWh/kg CO2). A more realistic scenario assuming 80 % compression/pumping efficiency and 90 % expansion work recovery gives an electricity consumption of 1.16 MJ/kg CO2 (i.e., 0.322 kWh/kg CO2), representing an energy penalty of 33.1 % for a coal-fired power plant. Future direction for further improvement could be a paradigm shift to hydrate process with thermodynamic promoters, which can potentially reduce the operation pressure by over 90 % and thus cut down the energy consumption dramatically. This work established a framework to simulate the hydrate-based carbon capture process, evaluated its minimum energy consumption and examined how operating conditions affect the separation performance. The results could offer valuable guidelines for the design and optimization of real hydrate-based carbon capture systems.

Educational design and modelling of electro-hydraulic control system machine tool motion

Purpose. To present the design and modeling technology of real electrohydraulic systems, for use in the educational process of a higher educational institution, and the prospects of the proposed approach in the training of technical specialists. As an example, the model of the motion control system of the hydraulic cylinder of the device for fixing parts on the working table of a milling machine, created on the basis of components of the Festo company, is considered. The methods. The methodological basis of the work is a systematic approach, which consists in the use of modern FluidSim software - comprehensive software for creating, modeling and studying, including electro-hydraulic circuits and educational equipment of the Festo company, which allows students to acquire and develop practical skills and at the same time simulate a real working environment . Additional advantages of computer and physical modeling in the educational process are the interactive component, which facilitates the visualization of educational material and improves the process of problem solving. Findings. Taking into account the pedagogical features inherent in the world trends in technical education, the application of a comprehensive approach using computer and physical modeling in the training of technical specialists in the design of electrohydraulic systems is justified in the educational process. The sequence and results of the students' work on one of the options for the implementation of the educational project – the control system for the motion of the hydraulic cylinder of the device for fixing parts on the work table of the milling machine – have been demonstrated. The result of the proposed approach is also an increase in students' motivation, the achievement of a higher level of practical knowledge and skills compared to the traditional model of education. The originality. A modified algorithm for the formation of an extended model of mastering educational material from electro-hydraulic devices and systems with the use of modern software and equipment has been developed. Which allows students to acquire and develop practical skills and at the same time simulate a real working environment. Practical implementation. The materials of the work can serve as a basis for using the proposed integrated approach, which will improve the process of learning and teaching electrohydraulics, ensuring a higher level of learning outcomes, especially in terms of acquiring practical knowledge and skills.

Efficiency analysis of a novel reversible solid oxide cell system with the secondary utilization of the stack off-gas: A model-based study

Systems with reversible solid oxide cells (rSOCs) can potentially overcome the spatio-temporal mismatch between intermittent generation from renewables and continuous electricity demand by operating bi-directionally. Achieving high energy conversion efficiency is one of the critical design objectives for a typical rSOC system. However, only a few papers discuss the effect of parameters and system processes on efficiency, and thermal management designs considering gas flow rates of the fuel and air loops are not yet seen. This work presents a novel rSOC-based system that employs a heat recovery unit for absorbing thermal energy as parasitic power gain and a water-gas heat exchanger instead of the electric evaporator to utilize the stack off-gas secondarily. Modeling and efficiency analysis of such a system is performed using a physically finite element method-based rSOC stack model coupled with extra auxiliary component models. Results indicate that efficiencies of 92%, 71.1%, and 62.4% can be achieved at 1,023 K and 1.23 bar in electrolysis, discharge, and the round-trip, respectively. The parasitic gain can significantly improve system efficiency and output performance and reduce the power loss in regulating the temperature uniformity of the stack with increased airflow. The outcomes can serve as guidelines for the thermal management design of real rSOC systems and control strategies optimization.

Encoding fidelity of binocular receptive fields with internal noise in the presence of external variability from natural scenes

Characterizing the properties of receptive fields that are involved in encoding behaviorally-relevant latent variables (binocular disparity, motion) is a focus of visual neuroscience research. The factors that determine which receptive field properties are most useful for encoding a particular latent variable in natural scenes are not well-understood. Here, using a stereo-image database with groundtruth disparity information at each pixel and a nonlinear-linear-nonlinear subunit modeling framework, we examine how external variability and internal noise jointly determine the binocular receptive field properties that are most useful for encoding binocular disparity in natural scenes. We compute the encoding fidelity, as indexed by Fisher information, of binocular receptive field pairs across preferred spatial frequency (SF) and differences in preferred phase disparity (binocular phase shift). Two major findings emerge. First, stimulus disparity and external variability (image and depth variability) determine the usefulness of different encoding subspaces, as defined by the preferred SFs of the binocular receptive field pairs. The most useful preferred SF decreases with stimulus disparity but increases with local depth variability. Second, internal noise determines the usefulness within the encoding subspaces of different basis elements, as defined by the binocular phase shifts of the receptive fields. In particular, with internal noise, encoding fidelity varies with the particular receptive field pairs within the subspace. Non-orthogonal receptive fields are most useful, a result that deviates from the quadrature-pairs posited by the disparity energy model. Most subunit modeling frameworks do not inject noise into the individual subunit responses. This modeling choice renders all subunit receptive field pairs spanning a subspace computationally equivalent. Incorporating subunit response noise makes more specific predictions regarding the particular receptive fields that are most useful for encoding a particular latent variable. The current modeling efforts bring us closer to understanding the principles governing the design of real neural systems in natural scenes.

An efficient routing strategy for coupled spatial networks

The study of traffic dynamics on couple networks is important for the design and management of many real systems. In this paper, an efficient routing strategy on coupled spatial networks is proposed, considering both traffic characteristics and network topology information. With the routing strategy, the traffic capacity can be greatly improved in both scenarios of identical and heterogeneous node capacity allocation. Heterogeneous allocation strategy of node delivery capacity performs better than identical capacity allocation strategy. The study can help to improve the performance of real-world multi-modal traffic systems.

SCO2 power plants for waste heat recovery: design optimization and part-load operation strategies

• We optimized five sCO 2 cycle configurations for waste heat recovery application. • Optimal plants reach efficiency higher than ORC (>27%) with similar specific cost (2000$/kW) • Simple recuperative cycle with bypass (SRBC) is selected as the optimal configuration. • We studied the different part-load strategies for this optimal configuration (SRBC) • Variable inventory part load strategy is more efficient than constant inventory strategy. This paper focuses on the potential of supercritical carbon dioxide closed cycle for waste heat recovery applications. The valorization of waste heat released from glass, steel and cement production facilities is recognized as one of the most effective solutions for the reduction of carbon footprint of the industrial sector. Common solutions rely on steam Rankine cycles and organic Rankine cycles while only few sCO 2 power plants have been manufactured and operated so far as this technology has not yet reached the technical and commercial maturity. In spite of the large interest on sCO 2 power plant from industry, institutions and academia, the role of this solution in future waste heat recovery applications is still unclear, highlighting the need of research studies focused on the performance assessment of these novel systems in both design and off-design conditions. This paper aims at bridging the gap between preliminary numerical studies and the design of real power systems by focusing on different aspects scarcely investigated in literature. The first section of this study deals with cycle design and provides a full description of the numerical complexity related to sCO 2 power plant optimization, with a detailed description of the assumptions and the models implemented for the design of cycle components. Five different cycle configurations for the exploitation of a heat source consisting of a 50 kg/s stream of flue gas at 550 °C have been analyzed and optimized: results are presented with a set of sensitivity analyses and the most promising configurations are analyzed from both a thermodynamic and a techno-economic perspective. Simple recuperative cycle, simple recuperative cycle with recuperator bypass and turbine split flow configurations are compared in detail proving that sCO 2 technology can reach overall efficiencies up to 27.5%, a value higher than ORC for the same power output (around 6 MW el ), and with a similar specific cost (2000 $/kW). Simple recuperative cycle with recuperator bypass is selected as the most promising configuration and it is further studied in off design conditions in the second section of the paper. Five different part-load strategies have been implemented allowing to assess the part-load performance of the selected cycle, considering both variable CO 2 inventory and constant CO 2 inventory systems. Results highlight that sCO 2 recuperative cycles equipped with a CO 2 storage vessel present a very high and almost constant efficiency down to 50% of the normalized flue gases mass flow rate, while a lower efficiency is expected for constant inventory systems. Both solutions can be operated down to 30% load with no difficulties on system components and with a minimum plant efficiency still competitive against ORC technology.

Numerical simulation of ammonia/methane/air combustion using reduced chemical kinetics models

Ammonia appears to be a potential alternative fuel that can be used as a hydrogen vector and fuel for gas turbines and internal combustion engines. Chemical mechanisms of ammonia combustion are important for the development of ammonia combustion systems, but also as a mean of investigation of harmful NOx emissions, so they can be minimized. Despite of large body of experimental and modelling work on the topic of ammonia combustion, there is still need for additional investigation of combustion kinetics.The object of this work is further numerical study of ammonia combustion chemistry under conditions resembling industrial ones. After literature review, three mechanisms of ammonia combustion that also include carbon chemistry are used for simulation of experimental premixed swirl burner with the aim of evaluating their performance. San Diego mechanism, that was also the most detailed one, proved to be the best in terms of emissions, but neither one of the models was able to accurately reproduce CO emission after equivalence ratio went beyond 0.81. It was also observed that oxygen is excessively consumed. This study contributes to the current knowledge by providing new insights in ammonia burning conditions closely resembling those in industrial applications, and consequently is expected that insights obtained will help in the design of real industrial burning systems.

Global dynamics perspective on macro- to nano-mechanics

In about the last two decades, global nonlinear dynamics has been evolving in a revolutionary way, with the development of sophisticated techniques employing concepts/tools of dynamical systems, bifurcation, and chaos theory, and applications to a wide variety of mechanical/structural systems. The relevant achievements entail a substantial change of perspective in dealing with vibration problems and are ready to meaningfully affect the analysis, control, and design of systems at different scales, in multiphysics contexts too. After properly framing the subject within some main stages of developments of nonlinear dynamics in solid/structural mechanics, as occurred over the last 40 years, the article focuses on highlighting the role played by global analysis in unveiling the nonlinear response and actual safety of engineering systems in different environments. Reduced order models of macro-/micro-structures are considered. Global dynamics of a laminated plate with von Karman nonlinearities, shear deformability, and full thermomechanical coupling allows to highlight the meaningful effects entailed by the slow transient thermal dynamics on the fast steady mechanical responses. An atomic force microcantilever is referred to for highlighting the severe worsening of overall stability associated with the application of an external feedback control and the importance of global dynamics for conceiving and effectively implementing a control procedure aimed at enhancing engineering safety. The last part of the article dwells on the general role that a global dynamics perspective is expected to play in the safe design of real systems, in the near future, focusing on how properly exploiting concepts and tools of dynamical integrity to evaluate response robustness in the presence of unavoidable imperfections, and to improve the system’s actual load carrying capacity.

Hydraulic optimisation of multiple flow control locations for the design of local real time control systems

ABSTRACT Local real-time control (RTC) represents a potentially cost-effective solution for stormwater management in urban drainage systems. Existing methodologies to select the location of flow control devices (FCDs) are limited to single gate systems and are based on analysis of activated storage volume capacity, without considering hydrodynamic processes or rainfall characteristics. In this paper, a new genetic algorithm (GA)–based methodology is developed to determine the optimal location of multiple FCDs in urban drainage networks, when assessing RTC performance through hydraulic analysis. The methodology is tested on a case study network, where a high number of possible FCD location arrangements are tested and compared, and the RTC effectiveness in reducing combined sewer overflows has been evaluated over a range of design storm events. Results demonstrate the capability of the proposed method in selecting robust FCD placement strategies, for example when designing local RTC systems to meet specific performance criteria.

Rotating Detonation Rocket Engine Operability Under Varied Pressure Drop Injection

Rotating detonation rocket engine (RDRE) experiments have so far been limited to injectors with high pressure drop to limit injector–plenum coupling. However, this corresponds to a reduction in the potential performance benefits of RDREs. To investigate this phenomenon, two injection configurations with different total injection areas are compared with respect to overall engine operability, global performance, and steady-state wave propagation. Notably, the increased area corresponds with a three to four times decrease in pressure drop, with negligible effects on operability and performance. The RDRE is found to operate in a detonative mode for both injectors across equivalence ratios between 0.6 and 2.5, and total mass flows between 0.09 and . The steady-state wave propagation varies significantly between the two injectors, with low pressure drop injection sustaining fewer waves traveling at higher velocities at the maximum performance conditions, but in all other conditions promoted lower wave speeds and counter-propagating behavior, denoting a breakdown in the steady wave propagation. This breakdown is likely due to increased injector–plenum coupling. These results provide insight into the effects of reduced pressure drop on the operation of an RDRE, and indicate challenges that must be overcome in the design of real systems that include RDREs.

Performance assessment of industrial-sized solid oxide cells operated in a reversible mode: Detailed numerical and experimental study

Reversible solid oxide cells (rSOCs) present a unique possibility in comparison to other available technologies to generate electricity, heat and valuable fuels in one system, in a highly-efficient manner. The major issue hindering their commercialization are system reliability and durability. A detailed understanding of the processes and mechanisms that occur within rSOCs of industrial-size, is of critical importance for addressing this challenge. This study provides in-depth insight into behavior of large planar rSOCs based on a comprehensive experimental and numerical study. All the numerical data obtained are validated with the in-house made cells and experiments. The sensitivity analysis, which covers a wide range of operating conditions relevant for industrial-sized systems, such as varying operating temperature, H2/H2O-ratio, operating current etc., provides very good accordance of the cell performance measured and simulated. It reveals that lowering fuel volume and thus causing fuel starvation has more pronounced effect in an electrolysis mode, which is visible in both the low-frequency and the middle-frequency range. Moreover, both co- and counter-flow are appropriate for the reversible operation. However, more uniform current density distribution is achievable for the counter-flow, which is of crucial importance for the real system design. The most accurate performance prediction can be achieved when dividing the cell into 15 segments. Slightly lower accuracy is reached by logarithmic averaging the fuel compositions, thus reducing the calculation time required. A computationally- and time-efficient model with very precise performance prediction for industrial-sized cells is thus developed and validated.

M6 formalism – generalization of the laser beam quality factor M2 to the 3D domain

Abstract Here we define a theoretical basis for the generalization of the beam quality factor M2 to three-dimensional (3D) space, which we call M6 formalism. The formalism is established through the use of examples of multifocal and Axicon optical systems to illustrate discrete and continuous axial beam shaping, respectively. For the continuous case, we expand the definition of the Rayleigh range to incorporate a quality factor having both axial and transverse components M add 2 $M_{{\rm{add}}}^2$ and M2. Using geometrical ray tracing simulations, a proportion factor C is found to empirically describe the axial quality factor M z 2 $M_z^2$ of an optical setup including an Axicon and a paraxial focusing lens with a Gaussian single mode input beam. Using our M6 formalism depth of focus (DOF) ranges are calculated for higher M2 beams, and are shown to be in good agreement with the simulated DOF range, demonstrating the usefulness of the M6 formalism for the design of real optical systems.

Reliability and sensitivity analysis of a retrial machine repair problem with warm standbys and imperfect coverage

This study aims at proposing system reliability and sensitivity analysis of a retrial machine repair problem with warm standbys and imperfect coverage. When an operating or warm standby machine fails, it may be immediately detected, located, and replaced with a coverage probability by a standby if one is available. The Laplace transform technique is adopted to derive two system performance measures, system reliability and mean time to system failure (MTTF). Sensitivity analysis and relative sensitivity are then executed. In order to realize how each system parameter affects performance measures, extensive numerical experiments are designed and the important results are outlined. The results of this study provide a valuable reference for the good design of related real world systems.

Kalman filter and satellite attitude control system analytical design

The article considers a certain form of suboptimal Kalman-Bucy filter (KBF), with bounded grows of memory (FBGM) and its application for satellite control system analytical design. The FBGM is robust and simple. Due to these qualities it can be easily practically implemented. This is especially important for airspace applications, where on-board computers (OBC), despite of the huge progress achieved in their characteristics, still have restricted resources. Since FBGM in the steady state can be made optimal KBF, it is used for, so called, analytical design (AD) of ACS, to estimate its potentially achievable performance in an idealistic case. This case assumes that all restrictions and constraints are removed and not taking into account as for the real system design process. Various schemes of filter usage in conjunction with the controller in closed negative feedback control loop are discussed. The emphasis is on analytical design; however, taking into account engineering aspects, the solution found can be implemented in real system as well.

Fair Energy-Efficient Resource Allocation for Downlink NOMA Heterogeneous Networks

The increasing in energy consumptions of the current wireless networks, leads towards designing energy-efficient 5G networks. The application of non-orthogonal multiple access (NOMA) in the heterogeneous networks (HetNets) improves the spectrum utilization with the cost of efficient resource allocation. Hence, this article proposes optimal user-pairing and power allocation solutions towards achieving fair energy-efficient resource allocation in downlink femtocell NOMA-HetNets. In the proposed optimization process, the considered constraints are the user's transmission rate, transmit power budget at the base station (BS), and the interference. The energy consumption of both the transmitter and the receiver are considered to simulate the real system design. The Greedy Algorithm (GA) is used to achieve a low-complex optimal solution during the user-pairing process. Simultaneously, the max-min energy efficiency optimization approach is employed to maximize the minimum energy efficiency of the femtocell users to achieve the optimal power allocation solution. The mathematical formulation of the max-min energy efficiency is a non-convex fractional programming problem and is intractable. Thus, the fractional programming theory is adopted to transform the problem into a sequence of subtractive form, followed by the Sequential Convex Programming (SCP) approach to determine the optimal solution. Simulation results show that the proposed NOMA with optimal power allocation method using SCP and GA (NOMA-SCP-GA) achieves fair energy efficiency performance with lower complexity compared to the benchmark methods. Moreover, the minimum energy efficiency of the femtocell user is 38.22% higher than NOMA with Difference of Convex programming (NOMA-DC). The NOMA-SCP-GA method can assure 5G capability demands.

Precoding for Flexible High Throughput Satellites: Hot-Spot Scenario

Motivated by the need of resource flexibility in high throughput satellite systems, a hot-spot cell configuration is introduced and analyzed in terms of throughput performance. Cell partitioning and user scheduling are also addressed in conjunction with the application of different types of linear precoding algorithms. The analysis is based on a real satellite system design and uses a system simulation approach, encompassing the random user distribution inside the hot-spot cell area. Results provide guidelines on the design of the hot-spot cell partitioning and show the achievable gains of precoding with respect to conventional, non precoded, transmission.

Design of Multimedia Engineering Teaching System Based On Internet of Things Technology

In order to improve the multimedia control performance of teaching, a multimedia engineering teaching system design model based on internet of things technology is proposed. The overall structure model of the real estate engineering multimedia teaching system design is constructed based on the embedded ARM core. The system integration control is implemented through the decentralised control method, and the overall design framework of the real estate engineering teaching system is carried out. The internet of things networking technology is used for system network design, the VIX bus technology is used to carry out real estate engineering teaching data communication and information processing, and the software design of the multimedia engineering teaching system is realised in embedded environment. The test results show that adopting this method to design the multimedia engineering teaching system can provide better robustness, stronger human-computer interaction, and can realise multimedia integrated control of teaching system.

Design of multimedia engineering teaching system based on internet of things technology

In order to improve the multimedia control performance of teaching, a multimedia engineering teaching system design model based on internet of things technology is proposed. The overall structure model of the real estate engineering multimedia teaching system design is constructed based on the embedded ARM core. The system integration control is implemented through the decentralised control method, and the overall design framework of the real estate engineering teaching system is carried out. The internet of things networking technology is used for system network design, the VIX bus technology is used to carry out real estate engineering teaching data communication and information processing, and the software design of the multimedia engineering teaching system is realised in embedded environment. The test results show that adopting this method to design the multimedia engineering teaching system can provide better robustness, stronger human-computer interaction, and can realise multimedia integrated control of teaching system.

Numerical optimization strategy for multi-lens imaging systems containing freeform surfaces.

With progress in freeform technology, freeform components are entering real system designs. Although freeform surfaces increase the degrees of freedom of systems, optimization strategies for placing multiple freeforms are still underdeveloped. We therefore investigated strategies for placing freeforms to achieve significant improvement in system performance for optical imaging systems. For demonstrating our findings and supporting our observations, we have chosen a Scheimpflug system and a lithography system. Several aspects are investigated and implemented in optimization strategies. These strategies are used to optimize and demonstrate the performance on selected examples, i.e., multi-lens imaging systems containing one or two freeforms. Finally, we describe a workflow to guide the design process from start to the end for implementing freeforms in order to achieve improved system performance.

Calibration for Channel Reciprocity in Industrial Massive MIMO Antenna Systems

Massive multiple input multiple output (MIMO) antenna systems have received a great deal of interest due to their applicability to industrial network systems. One of the major obstacles that reducing the performance of massive MIMO system is reference signal (RS) overhead which can be increased as the number of transmitter antenna increases in frequency division duplexing (FDD) system. Using channel reciprocity in time division duplexing (TDD) system can significantly increase the RS overhead performance using channel reciprocity. However, to use the channel reciprocity, channel calibration is a significant challenge to overcome in real system design. There are various base station (BS) calibration methods that have already successfully applied to the current BS, while there are few methods for the calibration of distributed user entities (UEs) and/or industrial Internet of things (IIoT) devices. In this paper, we propose a distributed UE RF calibration method of massive MIMO systems that uses the power headroom report. The power headroom is typically reported from the UEs and/or IIoT devices to the BS periodically or aperiodically. By including additional amplitude RF impairment information in the power headroom report, we can successfully transfer the necessary information from UE to BS. The proposed scheme does not require additional feedback, and is in compliance with current standards. There are five schemes based on the kind of information transferred to BS and the way of making a calibration factor that can be multiplied to the estimated channel. Numerical analysis shows that the proposed schemes can significantly increase the spectral efficiency with little system burden, and thus can be a core technology for the realization of massive MIMO for industrial network systems.