Control Of Thermal Processes Research Articles

3D Digital Modeling Technology for Thermal Power Plant Boilers Based on Digital Twins

With the rapid advancement of Digital Twins (DTs) technologies, they have emerged as viable solutions for enhancing the control and optimization of thermal power combustion processes. This paper presents a pioneering approach that leverages DTs to revolutionize the combustion process control system within thermal power generating units. Focused on bridging the physical and digital realms, our research establishes DTs of the combustion process control system (CPCS), situated within the Networked Control System Laboratory (NCSLab). We propose a novel five-dimensional (5D) DTs model encompassing the physical, data, service, connection, and virtual models, thereby facilitating a comprehensive fusion of physical and digital information. By analyzing the demands and technical intricacies of the combustion process control system, we design and implement a virtual 3D model, enriching the visualization and analytical capabilities of the DT environment. Furthermore, through controlled experiments on the combustion process and rigorous comparison with offline simulations, we validate the efficacy and feasibility of our approach. Importantly, our research opens avenues for future exploration, particularly in harnessing industrial real-time data to drive the virtual 3D model. Through the integration of Artificial Intelligence (AI) techniques such as Deep Learning, we elevate the capabilities of our DT framework. This enhanced predictive analytics, dynamic optimization, human–machine interaction, and virtual model realism. This research contributes to the advancement of DT technology in the context of thermal power plants and holds promise for driving innovation and efficiency across diverse industrial sectors.

Towards Understanding and Control of Thermal Processes in Lithium-Ion Batteries

Despite lithium-ion batteries (LIBs) being state-of-the-art commercial rechargeable batteries, there are still significant challenges. For example, heat generation during cycling can lead to performance degradation and safety issues1-2. During the process of charging and discharging, the heat that is generated from the chemical reactions taking placing is ideally distributed uniformly in space, to dissipate out the cell easily. However, in practice, heat generation tends to be heterogeneous throughout the battery, leading to localized overheating3. This phenomenon can result in e.g. decomposition of the solid-state electrolyte interphase (SEI) layer, triggering electrode reactions with the electrolyte and degradation of the electrolyte (producing combustible gases) and even melting of the separator4. Hence, comprehending the origins of temperature generation and its heterogeneity is crucial.To address this challenge, operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are applied to monitor the structural changes in the electrode materials during charge and discharge, while simultaneous temperature measurements are conducted using a thermal camera, as such obtaining spatial resolved structure/temperature/performance relationships. We have focused on state-of-the-art nickel rich NMC (Nickel Manganese Cobalt Oxide) versus graphite batteries and by comparing the structural changes of the electrode materials during cycling in ‘hot’ versus ‘cool’ areas of the electrode and battery, we were able to establish a structure-temperature relationships, on top of the electrochemical structure-performance relationships and as such unravel “heat-generation” process and reactions. The real-time temperature distribution was compared to the computational models using COMSOL, and insights in thermal processes and their possible control measures could be obtained.References Lain, M. & Kendrick, E. Understanding the limitations of lithium-ion batteries at high rates. Journal of Power Sources. Volume 493, 229690 (2021).Ma, S., et al. Temperature effect and thermal impact in lithium-ion batteries: A review. Progress in Natural Science: Materials International. Volume 28, Issue 6, Pages 653-666 (2018).Rafael, M., et al. Operando Radiography and Multimodal Analysis of Lithium–Sulfur Pouch Cells—Electrolyte Dependent Morphology Evolution at the Cathode. Adv. Energy Mater. 2103432 (2022).Joris, J., et al. A comprehensive review of future thermal management systems for battery electrified vehicles. Journal of Energy Storage 31, 101551(2020).

Technology for Effective Control and Intellectualization of Multifunctional Automated Thermal Process Control Systems

Technology for Effective Control and Intellectualization of Multifunctional Automated Thermal Process Control Systems

Aspects of an induced magnetic field utilization for heat and mass transfer ferromagnetic hybrid nanofluid flow driven by pollutant concentration

In the growing need for energy and heightened environmental considerations, the effective control and optimization of thermal processes and transferring mass are of utmost importance. Engine oil and water-based nanofluids have emerged as potential solutions for various industrial applications, from energy generation to sophisticated manufacturing. Because of these demands, the current work aims to explore the need and significance of its research field, providing insights into crucial elements of heat and mass transport properties in the presence of hybrid nanofluids. This work investigates the impact of an induced magnetic field, including hybrid nanoparticle circulation across a stretched surface with an endo/exothermic chemical reaction and the concentration of waste discharge effects. The acquired ordinary differential equations (ODEs) were solved using the Runge Kutta Fehlberg 45 technique. The findings show that engine oil leads to effectiveness in heat transfer, while water-based hybrid nanofluid performs better mass transfer. While motor oil works well in an endothermic situation, water-based hybrid nano liquid has a noticeable effect on heat transfer over the activation energy component in an exothermic chemical reaction process. Further, water-based nanofluids exhibit lower pollutant levels than engine oil when exposed to local pollutant external source parameter. These results provide essential guidance for choosing the best nanofluid for a given engineering problem, leading to greater effectiveness and productivity in various applications, including advanced cooling systems, chemical manufacturing, pharmaceuticals, waste treatment, and pollutant dispersion control.

Effects of Wax Components and the Cooling Rate on Crystal Morphology and Mechanical Properties of Wax–Oil Mixtures

Crystal morphologies of different binary and ternary “model mixtures” were investigated using different cooling conditions (with cooling rates from 0.1 to more than 300 °C min–1). Needle-like crystals tend to form in binary mixtures under fast cooling, while uncommon spherulitic crystals were observed in ternary mixtures under slow cooling. These differences in crystal morphology lead to distinct mechanical behavior of the “model mixtures”. As shown by cone penetration tests, mixtures with spherulitic crystals exhibit a lower mechanical strength than those with densely arranged needle-like crystals. In addition, nanoindentation tests demonstrated that Young’s modulus and plasticity limit of mixtures are higher upon faster cooling. Lipstick-shaped cast samples were studied, in which cooling rates are much higher at the surface than at the center. A gradual change in crystal morphology was observed from surface to center, correlating to the hard surface and the soft center as revealed by nanoindentation tests. This work illustrates the relationship between process thermal control, microstructure morphology, and mechanical properties for wax–oil mixtures, paving the way to the monitoring of sensorial properties by control of mixture composition and process control.

Reconstruction of control and application of thermal energy process and its technical, social, symbolic and palaeoenvironmental consequences

Since the discovery of fire use in the archaeological record, the reconstruction of its control and application to the transformation of matter within different human societies has followed a rather complex path owing to the different theoretical frameworks leading to the emergence of the study of fire structures. This special number focuses on methodological approaches and the use of experimental and analytical methods to study late prehistoric societies having different degrees of complexity that evolved in the Mediterranean region. In previous studies, we point out that, “rebuilding to understand”, is a necessary step in the reconstruction of thermal energy processes. However, this approach is also essential for the reconstruction of the history of fire structures at each studied site and must be adapted in relation to the complexity of thermal energy uses in the different kinds of societies concerned. In this article, we use examples from prehistory to show how the analysis of fire structures continues to be problematic. This is due to the epistemological difficulties of this type of study, the complexity of the phenomena and the inadequate cross-validation between different analytical methods. As a consequence, there has been a hyper-specialization and fragmentation of this field of research as well as a lack of systematic studies using a well-established theoretical framework. Finally, the practical inherent problems of our disciplinary approach have reinforced the inductive tradition that frequently neglects the broader theoretical perspective needed to address the issues at stake. In this sense, our approach needs to consider different human modes of appropriation, production and use of thermal energy as well as the strategies implemented by different societies to ensure the reproduction of social systems by the control and application of fire use. Therefore, we need to question the relevance of these issues vis-à-vis the different aspects of each society and cultural structure, at both infrastructural and ideological levels.

Influence of temperature and time modes of polymer pipes welding at low temperatures on the structure and properties of materials of compounds. Part I. Calculation of the heat process

Subject of research: thermal process of welding PE100 saddle branches to polyethylene pipes of existing gas pipelines at low temperatures.
 Purpose of research: development of an effective method for welding saddle branches to polyethylene pipes of gas pipelines at ambient temperatures up to minus 50 C based on thermal process control by introducing preheating into the technological process with subsequent cooling to equalize the temperature and cool the joint under a layer of thermal insulation material of calculated thickness.
 Methods and objects of research: in the first part of the work, the object of study is the non-stationary thermal process of welding. The mathematical model of the thermal process takes into account the heat of the phase transformation of polyethylene in the temperature range, the dependence of thermophysical characteristics on temperature and the degree of crystallinity of the material.
 Main results of research: calculations have determined the welding parameters of the saddle branch, which ensure the flow of the thermal process according to the regularity inherent in welding under conditions of permissible ambient temperature. It is expected that the control of the thermal process will make it possible to obtain a structure of the welded joint material that ensures the strength of the seam corresponding to the strength of the seam obtained by welding under conditions of acceptable temperatures.

Multi-wavelength pyrometry as an in situ diagnostic tool in metal additive manufacturing: Detecting sintering and liquid phase transitions in electron beam powder bed fusion

Radiation thermometry techniques have been implemented to measure thermal signatures in powder bed fusion (PBF) additive manufacturing (AM), including the use of imaging devices with a large field of view, to measure large areas of the powder bed with spatial discrimination, and those considered single spot devices that measure signatures from a small region. Traditionally, these techniques can be categorized as single-color (brightness) or two-color (ratio) pyrometry; imaging devices are single-color while spot devices can be either. Both techniques can be used to infer a target temperature using a priori knowledge of the emissivity or employing the graybody assumption of constant emissivity across the spectrum. However, the dynamics of PBF AM, where a concentrated heat source is employed to selectively melt powder material, lead to complex material phase transitions under non-equilibrium solidification conditions. This makes it challenging to measure accurate thermal signatures because the emissivity of the target is also constantly varying as the PBF process unfolds. In this work, we employed an established technique of multi-wavelength pyrometry in an electron beam powder bed fusion (PBF-EB) system to continuously measure temperatures and the thermal emissive behavior during sintering and melting of an Inconel 625 powder that was subjected to preheating by direct scanning with the electron beam. The measurements displayed distinctive changes in signal strength or emissivity (in the wavelength range between 1080 nm and 1640 nm) that indicated the material phase change from loose to sintered powder to molten material and finally to solidified material; these changes in signal strength/emissivity were correlated with electron microscopy observations. This work highlights the suitability of multi-wavelength (MW) pyrometry as an in situ diagnostic tool to identify thermal process signatures (i.e., absolute temperatures), and the radiative emissive behavior of the materials being processed. Several demonstrations of the use of this MW pyrometry technique as a diagnostic tool are provided, illustrating its ability to sense signal strength/emissivity differences as the material experiences changes due to its temperature, phase, morphology, and chemistry. Although spatial and temporal improvements in the technique can be pursued, the sensitivity of the approach is demonstrated, as an example, in the ability to capture the passing thermal wavefronts arising from the scanning electron beam. It is anticipated that this technique and the information it provides can be leveraged in the development of advanced techniques for thermal monitoring and process control in PBF.

Optimal control of thermal and wave processes in composite materials

The paper indicates the approach and the corresponding to it method of penalty functions for analyzing the problems of optimal control of thermal and wave processes in structural elements made of composite materials (composites). An object that is quite common in the industrial sphere, the structure of which is a set of layers (phases) of unidirectional composites — layered composites, is considered. When solving problems related to the analysis and description of the states of composites, quantitative characteristics of layers that are not functions of the coordinates of the points of the medium are usually used in order not to solve the corresponding problems for an inhomogeneous medium. Such functions are elements of Sobolev spaces, first of all, functions summable with a square. The convenience lies in the fact that when finding the conditions for solvability of initial-boundary value problems of various types (in most cases, such problems are the basis of mathematical models of many physical processes), it is possible to reduce to operator-difference systems, for which it is easy to construct a priori estimates of weak solutions. The next step after establishing the weak solvability of the initial-boundary value problem of the thermal or wave process in composites is the formulation and solution of the problem of optimal control of these processes. The proposed method of penalty functions on the example of solving such problems is a general method. It is applicable with slight modifications also not only in the case of elliptic, parabolic and other problems (including nonlinear) for scalar functions, but also for vector functions. An example of the latter is the Navier–Stokes system, widely used in the description of network-like hydrodynamic processes, considered in Sobolev spaces, the elements of which are functions with carriers on n-dimensional network-like domains, n greater or equal to 2.

Применение оптимального управления при определении режима обработки материалов концентрированными потоками энергии: краткий обзор

The analysis of approaches and ways of determining the processing mode (mechanical, local thermal, welding, thermal cutting, etc.) is given. It is shown that the task of determining the processing mode is the reverse, characterized by a violation of the causal relationship inherent in the real thermal process. Methods and principles of optimal control theory are more effective methods for solving inverse problems. The first problems of optimal control of thermal processes of processing materials with concentrated energy flows were posed and solved in 1976 at the Baykov Institute of Metallurgy of the USSR Academy of Sciences as one-dimensional problems of thermal conductivity. Two- and three-dimensional optimal control problems were posed later and solved using the same methods of the theory of optimal control of systems with distributed parameters. The application of the principles of optimal control and the capabilities of modern computer technology make it possible to reduce the number of field experiments in determining the processing mode and increase the efficiency of the technological processes being developed.

Dimensional reduction of a 3D thermoelectric model to create a reliable and time-efficient 2D model representing an aluminum electrolysis cell

In order to optimize the use of their assets, aluminum smelters aim at increasing the line current. In addition, the fluctuations of the energy market push the industry to exploit power modulation strategies. These variable operating conditions directly affect the thickness of the protective layer (ledge) inside the electrolysis cell. Continuous monitoring of the energy balance is therefore of utmost importance, although physical measurements are difficult due to the hostile environment. The 3D thermoelectric slice digital model is the most frequently used to solve the energy balance, but its high computation time prevents it from being used in a control system. For the first time, the creation of a novel 2D model from an existing 3D slice model is proposed for online thermal diagnosis and process control purposes. The creation starts with a detailed dimensional reduction protocol, which is a significant industrial contribution since it can be applied to any industries relying on 3D physical models. The rigorous methodology developed involves the identification of adjustable parameters that are inserted in the 2D model to minimize deviations caused by physical differences between models and ensure its reliability. Once calibrated, the 2D model is tested using a ± 5% input current variation. The results show minor differences (below 1%) between 3D and 2D models for the predicted behavior of the heat losses distribution and generated heat distribution. Side ledge profiles are very close in both models, the largest difference (1.8 cm) being in an acceptable range for this key operational parameter. During all simulations, the 2D model computing time was 40 to 60 times faster than the 3D model. With the 4.0 era, this is a reliable and time-efficient tool for industries wishing to turn to digital twins.

On an iterative method for solving optimal control problems for an elliptic type system

An important class of applied problems is that of optimal control of some objects’ state. It is required to select control actions in such a way as to achieve desired effect. We deal with distributed systems, since their state is described by a partial differential equation. In this paper we study an iterative process for solving the problem of optimal control for an elliptic type system. Similar problem arises during the control of thermal processes. The quality of system state control is estimated by a given quality functional defined on the solution of the Dirichlet problem for an elliptic equation. One of the most important classes of thermal process control problems is temperature control, which means maintaining given temperature in the computational domain due to certain thermal effects. Here, a distributed internal heat source acts as a control. In the paper, we study statement correctness of the optimal control problem with a regularized functional. More precisely, we examine control problem for a system described by an elliptic type equation and formulate its optimality condition in the form of a system of equations for initial and conjugate states. An iterative method is proposed for solving the optimal control problem of an elliptic type system. Convergence of the iterative process is studied, and the rate of convergence is estimated.

Thermal process monitoring and control for a near-net-shape Wire and Arc Additive Manufacturing

Wire and Arc Additive Manufacturing (WAAM) is a promising technology for the fabrication of large metal parts. During the process, the wire electrode is melted continuously or in a pulsating mode and deposited layer-by-layer onto a substrate. Due to the recurring energy input into the part during WAAM, adequate thermal management is crucial. The temperature distribution, especially the interlayer temperature in the part, is determined by the parameter settings as well as by the dwell times and can be monitored. This paper presents the cause-effect relationships between the interlayer temperature and the dwell times to enable a suitable temperature management. Thermal imaging was implemented during the manufacturing process, allowing the analysis of different interlayer dwell times and their effect on the interlayer temperatures. In addition, the influence of the temperature management on the geometric quality characteristics of the part was investigated. It was observed that a constant interlayer dwell time led to geometric irregularities in the part height and width. Monitoring the interlayer temperature is crucial in WAAM in order to maintain a constant temperature level along multiple layers for meeting the requirements for the geometry of the part and enabling near-net-shape manufacturing.

Digital twin-driven multi-variable process control of thermal manufacturing processes

Thermal manufacturing processes are complicated to the extent that they require sophisticated performance optimization. However, their implemented form often lacks advanced control strategies. This research proposes digital twins (DTs) that generalize the concept of process control towards multivariable performance optimization. To achieve this, data-driven models are used to describe the mathematical link between the process parameters and the performance indicators (KPIs), while they are all defined based on the spatiotemporal profile of the temperature field. The control strategy is then designed based on time and quality criteria, while the control enforcement is regarded in real-time manner, so that the DT concept is validated. The performance of the process models is examined through aggregation of modelling details from physics-based models from an LPBF process, including delays and dynamics. The current proposed framework seems to close the gap between the theoretical and data driven models with respect to process modelling and control efficiency.

Optimal control of inverse thermal processes in a parabolic equation with nonlinear deviations in time

Optimal control of inverse thermal processes in a parabolic equation with nonlinear deviations in time

Reference Model Control of the Time Delayed Double Integrator

This paper illustrates the reference model-based dead-time compensator (RM-DTC) recently developed for first-order time-delayed systems using a real-time example, and extends this novel approach for a time-delayed double integrator system. RM-DTC enables fully decoupled setpoint tracking and disturbance reconstruction and compensation. The overall structure of RM-DTC includes feedforward control using either a transfer function based implementation or the primary loop which produces a filtered inverse of the model transfer function. The setpoint feedforward is complemented by a disturbance-observer-based input disturbance reconstruction that also uses the filtered inverse of the plant model. The reference models of setpoint and input disturbance feedforward control allow the introduction of a stabilising PD controller without compromising the nominally independent dynamics of setpoint tracking and disturbance rejection. The main advantage of retaining the full functionality of disturbance reconstruction in RM-DTC is that it enables monitoring and diagnostics of the controlled process, which is important in terms of full automation of running processes representing the fundamental goal of the Industry 4.0 campaign. This surpasses the approaches based on internal model control, which have been modified for unstable systems to achieve internal stability by eliminating the reconstructed disturbance signal from the control loop. The excellent properties of RM -DTCs are illustrated by simulation and real-time control of thermal process.

On a Time-Optimal Control of Thermal Processes in a Boundary Value Problem

On a Time-Optimal Control of Thermal Processes in a Boundary Value Problem

Design and implementation of virtual experiment for complex control system: A case study of thermal control process

Online experimental systems that include remote and virtual experiments based on the Internet has become a new form of experiment in engineering education. This paper proposes a virtual experiment for the complex process control system. It is based on the networked control system laboratory (NCSLab), which provides a reliable framework for virtual thermal experiment. Taking the combustion system of 1000 MW ultra-supercritical coal-fired once-through boiler-turbine units as an example, the framework and the implementation process of the online system are given in this paper. A new presentation form for complex processes control experiment is provided, which could be a solution for simulating physical experimental equipment in virtual environments. The potential danger in practical experiments could be avoided. Additionally, the real-time operation for complex control systems could be presented in a 3D scene. Meanwhile, the flexibility and efficiency could be increased in engineering experimental education. Moreover, using the experiment evaluation method, the references and feedback for teaching and assessment are provided in this paper.

On the solvability of the tracking problem in the optimization of the thermal process by moving point controls

In the present article we investigate problems of tracking in the moving point control of thermal processes described by Fredholm integro-differential equations in partial derivatives with the Fredholm integral operator, in the case when the functions of point sources are nonlinear with respect to the control function. It is found that optimal controls are defined as solutions to a system of linear integral equations, and an algorithm for constructing its solution is developed. Sufficient conditions for the unique solvability of the tracking problem are found and an algorithm for constructing a complete solution to the nonlinear optimization problem was indicated.

Self-adaptive field manipulation with thermal logic material

Emerging thermal metamaterials have been deployed to realize advanced thermal field manipulations and opened up the possibilities of flexible control of thermal processes. However, the state-of-art thermal metamaterials only possess fixed and passive functionalities, and the artificial interventions of structural adjustments are also inescapable. In this paper, we propose a class of thermal logic material to overcome such long-standing problems. The proof-of-concept scheme can be created with varied configurations of shape memory alloy (SMA) and conventional thermal media. Thanks to the shape changes of SMA and multifarious medium configurations, self-adaptive switching between thermal transparency and obvious signature can be observed under appropriate working-temperature ranges of SMA with the logic operations of AND, NOR, and XOR-NOT gates. The findings provide a constructive paradigm of creating logic operations in thermal field, and might further pave the way of intelligent thermal manipulation and management with varied configurations of thermal logic gates.