In modern conditions, the importance of energy conservation, the use of energy-efficient technologies, and the reduction of fossil fuel resources have become key issues. One possible solution is to develop turbine units based on vortex and jet expansion turbomachines. However, studies in their performance using the computational fluid dynamics (CFD) approach need to be considered more thoroughly, i.e., using the appropriate boundary conditions. Therefore, due to the significant resource costs associated with physical modeling, researching CFD analysis for this type of turbomachine becomes more urgent. The article examines the peculiarities of numerical modeling, particularly the choice of boundary type in the calculation domain. The originality of this study lies in determining the impact of boundary conditions on gas flow within the flow parts and the parameters of channel expansion jet-reactive turbines, as conducted for the first time using the ANSYS CFX software package. The results presented for five different combinations of outlet boundary conditions will be helpful for further optimizing the geometry of jet expansion turbomachines and rationally designing turbogenerators based on them.

The global community, and Ukraine in particular, is showing significant interest in transforming and modernising energy systems to improve efficiency, reliability, and environmental sustainability. A key role in this transformation is played by the decentralisation of energy production and the integration of renewable and/or innovative energy sources into industrial and municipal enterprises. A potential solution lies in the implementation of turbine equipment based on jet-reaction turbines (JRT) at gas distribution stations. However, this type of installation is relatively new and requires further research using various working fluids. The aim of the work is to conduct numerical studies using Computational Fluid Dynamics (CFD) methods and to analyse the parameters obtained for a channel-type JRT using natural gas as the working fluid. Computational modelling of gas-dynamic processes was implemented in the ANSYS CFX software and computing complex for a rotation speed range from 0 to 25,000 rpm. During the study, the dependencies of power, torque, and efficiency on rotor rotation speed were determined. It was established that the maximum power of the installation reaches 204.06 kW, and the highest efficiency is 0.486 at a rotor speed of 25,000 rpm. Analysis of the Mach number distribution confirmed the occurrence of stable supersonic zones in the inlet nozzle and at the inlet to the axial channel at rotor speeds of 20,000 and 25,000 rpm. The results of the work scientifically justify the feasibility of integrating utilisation JRTs into the reduction units of gas distribution stations, gas control points at enterprises, etc. This not only allows critical infrastructure facilities to meet their own energy needs, but also contributes to the overall decentralisation of energy networks and to the strengthening of the state's energy independence, which aligns with sustainable development goals.

The current landscape of energy production and industrial processes increasingly demands highly efficient and reliable equipment. Liquid-vapor jet ejectors (LVJEs), due to their simplicity, absence of moving parts, and ability to handle various working fluids, offer a compelling solution for a range of applications, including vacuum generation, refrigeration, and thermal compression. However, accurate design and optimization of these devices remain challenging due to complex thermodynamic interactions involved. Existing calculation methods often rely on simplified assumptions or empirical correlations, which may limit their applicability and accuracy across different operating conditions and working fluids.This work introduces a novel methodology for calculating LVJEs, enabling precise determination of thermodynamic pa-rameters at key points of their operating cycle through the application of enthalpy-entropy (h,s) diagrams. The proposed meth-odology yields reliable results for calculating LVJE operational parameters and deriving their fundamental geometric dimen-sions across various operating conditions. A significant advantage of this method is its inherent universality, allowing for its application with diverse working fluids and adaptability to a broad spectrum of input parameters.The practical utility of these findings lies in the potential for more accurate design of LVJEs for energy installations, thereby enhancing the efficiency and reliability of technological processes within these devices. Implementation of the devel-oped methodology is expected to significantly improve calculation accuracy and facilitate optimal LVJE design, representing a promising avenue for advancement in the field of power engineering. The subsequent phase of this research involves con-ducting experimental validations to correlate theoretical models with real-world outcomes. This will provide empirical support for the proposed methodology and refine its predictive capabilities.

Енергетика України є основоположною галуззю для розвитку економіки держави та збереження її суверенітету. Суттєвою проблемою сьогодні є розумне використання енергетичних ресурсів Землі. Україна намагається вирішити це питання, про що свідчить реалізована програма «Безпека, енергоефективність, конкурентоспроможність (Енергетична стратегія України до 2035 року)». Предметом вивчення у статті є струминно-реактивні розширювальні машини. Мета роботи: розглянути принцип роботи та особливості конструкції існуючих струминно-реактивних відцентрових розширювальних машин. Завдання: на основі аналізу існуючих струминно-реактивних відцентрових розширювальних машин відокремити особливості конструкції та параметри, що впливають на роботу цих машин. Енергетична галузь переживає серйозні потрясіння. У Німеччині, наприклад, великі атомні та вугільні електростанції в гігаватного масштабу планується закрити в найближчі роки. Багатоступінчасті осьові турбіни переважали протягом останніх ста років на електростанціях класу кілька сотень МВт, і ця архітектура, звичайно, не є відповідним рішенням для утилізації енергії надлишкового тиску пари або газу, з якої можна отримати потужність 1 МВт або навіть нижче 100 кВт. Парові турбіни, що використовувалися до цього часу, вже не підходять для цих завдань. Електроенергія має вироблятися в багатьох невеликих установках у децентралізованій відновлюваній енергетиці і екологічно чистим способом. З цієї причини автори досліджують відомі конструкції турбін, які практично не використовувалися через їх низьку ефективність і майбутні електроприводи. Однак ці незвичайні конструкції турбін можуть підійти для малих та мікромасштабних розподілених електростанцій і міні-ТЕЦ, що використовують як класичні термодинамічні цикли, так і цикли з утилізації сонячного, геотермального тепла, тепла біомаси, продуктів згоряння або потенційної енергії тиску, що втрачається при редукуванні, тому що в цих умовах класичні турбіни (осьові і доцентрові), також мають низку ефективність при більш складній конструкції та собівартості. Обґрунтовано доцільність використання струминно-реактивних відцентрових розширювальних машин із ущільненням у осьовому зазорі. Наукова новизна отриманих результатів полягає в наступному: створено класифікацію струминно-реактивних відцентрових розширювальних машин.

Implementing energy-efficient solutions and developing energy complexes to decentralise power supply are key objectives for enhancing national security in Ukraine and Eastern Europe. This study compares the design, numerical, and experimental parameters of a channel-type jet-reaction turbine. A steam turbogenerator unit and a pilot industrial experimental test bench were developed to conduct full-scale testing of the unit. The article presents experimental data on the operation of a steam turbogenerator unit with a capacity of up to 475 kW, based on a channel-type steam jet-reaction turbine (JRT), and includes the validation of a computational fluid dynamics (CFD) model against the obtained results. For testing, a pilot-scale experimental facility and a turbogenerator were developed. The turbogenerator consists of two parallel-mounted JRTs operating on a single electric generator. During experimental testing, the system achieved an electrical output power of 404 kW at a turbine rotor speed of 25,000 rpm. Numerical modelling of the steam flow in the flow path of the jet-reaction turbine was performed using ANSYS CFX 25 R1 software. The geometry and mesh setup were described, boundary conditions were defined, and computational calculations were performed. The experimental results were compared with those obtained from numerical simulations. In particular, the discrepancy in the determination of the power and torque on the shaft of the jet-reaction turbine between the numerical and full-scale experimental results was 1.6%, and the discrepancy in determining the mass flow rate of steam at the turbine inlet was 1.34%. JRTs show strong potential for the development of energy-efficient, low-power turbogenerators. The research results confirm the feasibility of using such units for decentralised energy supply and recovering secondary energy resources. This contributes to improved energy security, reduces environmental impact, and supports sustainable development goals.