This study investigates the combustion behavior of hydrogen–air mixtures in a closed chamber at reduced initial pressure, focusing on applications in thermal energy methods (TEMs) for plastic processing. The primary goal was to develop and validate a numerical model capable of accurately predicting pressure and temperature profiles over time. By employing ANSYS Fluent 2024 R2 and the GRI-Mech 3.0 mechanism, a detailed combustion model was constructed and validated against experimental data, adhering to the standards outlined in EN 15967: 2011. Subsequent simulations under low-pressure conditions revealed consistent flame front propagation and turbulent flow patterns, crucial factors for achieving stable temperature distributions and optimal part placement. This validated model provides a valuable tool for predicting combustion effects, enhancing safety, and optimizing the performance of hydrogen-fueled TEM processes. By leveraging hydrogen as a clean and sustainable energy source, this research contributes to a more environmentally friendly approach to plastic processing. Future studies will delve into the combustion of hydrogen–air mixtures in the presence of plastic parts to further refine the efficiency and effectiveness of TEM processes.

The research subject is a digital twin of the process of filling the tank with gas mixture components. The aim is to justified choose the digital twin model of the tank filling process with a gas mixture. The task of the study consists of the analysis of construction methods and the operation modes of the digital twin as well as selecting the operation settings of the digital twin model, which ensure a rational reproduction of the gas-dynamic non-stationary of the tank filling process with a component of the gas mixture. The following results were obtained. In accordance with the digitalization concept of modern production, the need to build digital twins for individual physical and chemical processes is substantiated in relation to the researched thermal pulse processing technology. The specifics of the operation of the fuel mixture generator using the critical hole method are determined and the corresponding defining equations for the dosing of gas mixture components and the tank filling time are given for constructing a control system using a digital twin of the process. Existing methods of building digital twins similar to the system under study are analyzed. For further use in the structure of a digital twin of a separate tank filling subsystem, a component of the gas mixture, a finite-element model of gas-dynamic unsteady flow was built and a numerical study was conducted using the ANSYS Fluent software. The dependence on the tank filling time of such basic parameters of the process under study as pressure, temperature, and filled mass of the gas mixture was determined. Reasoned feasibility and developed reduced-order model (ROM model ANSYS Fluent) and used in ANSYS Twin Builder to build a digital twin. Developed and analyzed examples of digital twins of the system of filling the tank with a gas mixture using standard elements of the Twin Builder and Modelica libraries.

The object of this study are ways to ensure the speed and repeatability of the valve for the release of combustion products from the thermal-pulse unit, which are the most important parameters that enable the precision of the finishing treatment with detonating gas mixtures. The study is aimed at analyzing the process of releasing combustion products in the valve of the proposed design; identification of factors that affect the speed of its opening; establishing the nature of the change in gas dynamic parameters in the combustion chamber. Experimental studies were carried out on a specialized bench simulating the operation of a valve with pressure measurement in gas cavities and controlling the movement of a movable glass of the valve with an incremental encoder. Information on the position of the movable cup is obtained in real time with a decisive ability of 3 microns. The experimental study showed that an increase in the response rate of the valve of the design under consideration to the values required for precision thermal pulse treatment (0.01 s) is possible subject to the use of compressed air. To study the flow processes of high-temperature gases during the operation of the controlled outlet valve, partially immersed in water, a numerical model has been built. A feature of the model is to take into account the real values of the friction force acting on the moving part of the valve, due to the introduction of resistance force acting on the movable glass. The magnitude of this force under the specified initial conditions is assigned from the condition of ensuring the coincidence between the estimated opening time of the valve and its average value obtained from full-scale experiments. For the range of design conditions, based on the lower limit of the working pressure of the combustion products, the water level is determined in the chamber of the thermal pulse equipment, on which the valve must be partially immersed for safe operation

This study investigates the combustion of a hydrogen-air mixture at low initial pressure in a closed chamber, focusing on thermal energy methods (TEM) used for processing thermoplastics. This study aims to develop and validate a numerical model capable of predicting critical combustion parameters, specifically, the pressure and temperature distribution profiles over time, to ensure safe and efficient TEM processing. The tasks included constructing and validating the hydrogen-air combustion model using experimental data for high accuracy and applicability in TEM systems. The methods involved numerical simulation of the hydrogen-air mixture combustion in ANSYS Fluent using the GRI-Mech 3.0 mechanism, employing fourth-degree polynomial functions to define the thermodynamic properties of the species. Validation against previous experimental data yielded highly accurate results with peak pressure deviations of less than 3%. The following validation, the model was applied to simulate combustion in an industrial TEM chamber, which is representative of real operational conditions. Results showed consistent flame front development, including the formation of turbulent cellular structures, which are essential for achieving optimal temperature distribution and stability within the chamber. These insights allow for strategic part placement to maximize processing quality, which is especially important when using low-pressure hydrogen-air mixtures. In conclusion, the validated model emphasizes the potential of green hydrogen-based fuels as eco-friendly alternatives for energy-intensive industrial processes, thereby advancing climate-neutral manufacturing. Future work will expand on combustion studies using plastic parts in TEM chambers to improve processing precision and safety for broader adoption in sustainable thermoplastics manufacturing.

The subject of this article is the computational analysis of the effect of nozzle geometry on gas dynamics and particle acceleration in cold gas dynamic spraying (CGDS). This study aims to compare the performance of conventional conical nozzles and Method of Characteristics (MOC)-based bell-shaped nozzles in accelerating particles to the critical velocities required for effective coating deposition. The tasks to be solved are as follows: design and model conical and MOC nozzles; conduct CFD simulations of compressible two-phase gas–particle flows in both geometries; analyze velocity, pressure, and temperature distributions along the nozzle and jet regions; and evaluate particle acceleration and velocity distribution for aluminum powder. The following methods were used: numerical modeling of gas–particle flow employing the Navier–Stokes equations with the RNG k–ε turbulence model in ANSYS Fluent 2025 R1, along with Lagrangian particle tracking; computational design of nozzles using MATLAB code based on the Method of Characteristics; and comparison of flow fields and particle dynamics between nozzle configurations. The results show that both nozzles operate under underexpanded jet conditions, but the MOC nozzle accelerates the carrier gas and particles earlier, resulting in more uniform velocity fields and reduced velocity lag between the gas and the dispersed phase. For 25 µm aluminum particles, the MOC nozzle achieves higher particle velocities than the conical nozzle, indicating greater potential for plastic deformation and improved coating adhesion. Additionally, higher exit gas velocities and more stable jet structures were observed in the MOC nozzle, despite the presence of more pronounced boundary-layer vorticity. Conclusions. The scientific novelty of the results lies in establishing the gas-flow acceleration patterns with aluminum powder particles in conical and MOC-based nozzles, optimized for aluminum deposition at 2.5 MPa gas pressure and 650 °C. The MOC-based nozzle enables earlier gas expansion and a more stable free-jet structure, thereby achieving a higher, significantly more uniform powder particle velocity than the conical nozzle under identical spraying conditions.