Leonid V Plotnikov

The aim of this study was to experimentally investigate the effect of the intake valve lift and the number of active valves on the in-cylinder jet structure and flow resistance of a piston engine under steady-flow conditions over a wide range of air flow rates using Particle Image Velocimetry (PIV). The experiments were performed on an optical model of a piston engine cylinder equipped with a transparent cylinder and a valvetrain with two poppet valves. The model has no moving piston, and the measurement plane corresponds to the bottom dead center position of the prototype engine. The valve lift was varied within the range 0–12 mm, and either one or both intake valves could be activated, thereby replicating the geometry of a naturally aspirated spark-ignition gasoline engine with a bore/stroke ratio of 82/71. High-resolution flow-field images were acquired by PIV in two mutually perpendicular cross-sections at volumetric flow rates of 50–113 m³/h, with local flow velocities in the measurement plane ranging from 15 to 55 m/s. The results are discussed in terms of the jet structure, the vortex formation intensity, the turbulence intensity and the size of low-velocity regions. They characterize the flow resistance of the intake tract for each configuration. Numerical simulations of the engine working cycle were performed in Diesel-RK to complement the experimental data. Simulations were performed for the symmetric valve configurations at crankshaft speeds of 1000, 3000 and 6000 min⁻¹. The calculated air flow rates ranged from 16.8 to 124.5 m³/h, thus covering the experimental range of 50–113 m³/h. The optimal valvetrain configuration among those tested depends on the airflow rate under steady-flow conditions. The single valve with a 6 mm lift provides the lowest flow resistance and the most uniform jet structure among the configurations tested at 50 m³/h. The single 6 mm lift and the asymmetric 6/12 mm configuration give comparable results at 79 m³/h. The asymmetric 6/12 mm configuration is the most effective at 97 m³/h. Two valves fully open to 12 mm provide the most uniform filling at 113 m³/h. The simulation reproduces the same general trend for the symmetric configurations as the crankshaft speed increases from 1000 to 6000 min⁻¹.

Additive manufacturing has become an important technology for turbomachinery blades because it enables lightweight components of high geometric complexity and allows the external shell and internal infill to be designed separately. However, published studies on blade internal structures remain fragmented because different works consider different cell types, materials, optimization formulations, and evaluation criteria, which complicates cross-study comparison. This review synthesizes 47 sources and classifies internal structures according to the method of geometric definition, distinguishing 2D parametric structures (class A1), 3D parametric strut-based and TPMS-based structures (class A2), free-topology structures obtained by topology optimization or generative design (class B), and hybrid structures combining parametric infill with free topology (class AB). Comparative analysis based on normalized data extracted from 17 studies is used to examine the effects of these structure classes on natural frequencies, stress state, thermal state, and fatigue life. The review is complemented by a structured study-by-study summary, which systematizes the studies used in the review discussion in terms of component type, material, additive-manufacturing process, internal-structure class, analysis method, investigated indicators, main results, and limitations. The available evidence indicates that class A1 structures are used mainly for mass reduction in narrow internal cavities, class B structures are especially effective for targeted material redistribution and often provide the largest increase in lower natural frequencies, whereas TPMS-based structures appear particularly promising for thermal-state-related applications. At the same time, fatigue life and manufacturing accuracy remain among the least studied and least experimentally validated characteristics.

RELEVANCE of the study is since improving the efficient, economic and environmental performance of reciprocating engines (ICE) powered by alternative gaseous fuels remains an important task for the development of mechanical engineering and energy. Therefore, the creation of mathematical models of the working cycle of ICEs operating on different gases and improving their energy efficiency is relevant for science, technology and technology. The PURPOSE of the study was to increase the efficiency and energy efficiency of an ICE-based electric generator by optimizing its operating cycle parameters after replacing the base fuel (propane-butane) with synthesis gas based on numerical modeling. METHODS. The object of the study was a 1 kW electric generator based on a single-cylinder ICE with external mixing. The article describes the main approaches to creating a mathematical model of the engine operating cycle, the physicochemical properties of the base fuel (propane-butane) and a new laboratory synthesis gas. The simulation results are verified through experimental studies. The differences between simulation and the experiments for the key parameters (power, efficiency, air and fuel consumption) did not exceed 4.0%. The efficiency of the ICE was chosen as a key criterion for optimizing the operating cycle. RESULTS. Data on the performance of an ICE powered by propane-butane and synthesis gas for different operating cycle parameters (compression ratio, excess air ratio, ignition timing angle, gas exchange system resistance) were obtained based on mathematical modeling. CONCLUSION. It is shown that replacing propane-butane fuel with synthesis gas causes a decrease in engine efficiency of up to 33% (the efficiency of the basic ICE was 0.179 versus an efficiency equal to 0.119 for the efficiency of the converted ICE for a power of 0.59 kW). As a result of optimization, the efficiency of the converted syngas engine was 6.1% higher than that of the base propane-butane ICE, and the power drop did not exceed 8%. Thus, careful refinement of the operating cycle parameters makes it possible to increase the energy efficiency of a synthesis gas engine to the level of an ICE running on traditional fuels.

The use of alternative fuels to generate mechanical and thermal energy in engines is a promising and sought-after technological area with its own unique advantages and characteristics. Consequently, enhancing the technical, economic, and environmental efficiency of gas engines fueled by propane-butane mixture and syngas through optimized operating cycle parameters (including valve timing, ignition timing angle, fuel mixture composition, and compression ratio) is a pressing imperative for scientific and energy sectors. The aim of the study was to investigate and compare the performance of an engine with different compression ratios running on a propane-butane mixture and laboratory syngas. The research’s primary originality lies in its joint study of syngas production technology and the evaluation of the efficiency of a mini power plant fueled by the resulting gas and conventional gas. This article presents a description of the experimental setup, data on measuring instruments, technical characteristics of the mini-power plant, the process for obtaining laboratory syngas, the properties of the gaseous fuels used, and experimental methods. Data on air and fuel consumption, as well as engine efficiency at different compression ratios when running on a propane-butane mixture and syngas, were obtained and analyzed. Converting an engine from a propane-butane mixture to syngas results in a reduction in power of almost 30% and efficiency by 13%–33%. Increasing the compression ratio by 0.9 units causes a rise in maximum efficiency from 0.177 to 0.235 for an engine running on a propane-butane mixture and an increase in maximum efficiency from 0.136 to 0.161 for a syngas engine. It has been confirmed that the compression ratio significantly impacts the technical and economic performance of an engine running on gaseous fuel. The obtained results can be used to modernize existing engines for operation on alternative fuels (syngas) and to design new mini-power plants with promising technical, economic, and environmental characteristics.

Conical diffusers perform a variety of critical functions in final products (gas, hydraulic, and wind turbines, ejectors, gasifiers, combustion chambers, etc.). The purpose of this study was to experimentally study the flow distribution features in a vertical conical diffuser with different technical air supply methods to find directions for optimal movement organization. The vertical diffuser (apparatus) consisted of a conical section with an opening angle of 30° and a cylindrical section. The scientific results were obtained based on an experimental stand and the thermal imaging method. The article presents simplified equations of continuity and momentum balance for the system under consideration. Two methods of air supply to the diffuser were investigated: air supply through a single duct and air supply through 4 nozzles installed at different angles of 45°, 60°, and 70°. The experiments were carried out for stationary air movement with volumetric flow consumption through the system from 0.0018 m³/s to 0.006 m³/s. The Reynolds number for the air flow at the diffuser inlet ranged from 10,500 to 106,000. Significant differences in the flow structure for air supply to a diffuser through a single duct and nozzles were identified. The possibility of controlling the flow structure in a vertical diffuser by varying the inclination of the supply nozzles was demonstrated. Four characteristic patterns of air distribution in the diffuser were obtained: firstly, a pronounced central flow through the entire apparatus with a noticeable deviation of the flow to the right side; secondly, a local (from 30 to 75% of the apparatus height), central flow in the diffuser; thirdly, active air movement in the lower part of the diffuser with subsequent flow along the side walls of the apparatus; fourthly, multidirectional flow movement throughout the entire volume of the diffuser.

RELEVANCE of the study is determined by the fact that non-stationary gas-dynamic phenomena in pipelines of complex configuration are widespread in heat exchange and power equipment. Therefore, the study of the level of heat transfer of pulsating air flows in round and triangular pipes with different degrees of turbulence is an urgent and significant task for the development of science and technology. THE PURPOSE. The influence of gas-dynamic nonstationarity (flow pulsations) on the degree of turbulence and the intensity of heat transfer of air flows in straight pipes with different cross-sectional shapes had to be assessed.METHODS. The studies were conducted on a laboratory bench based on the thermal anemometry method and an automated system for collecting and processing experimental data. Rectilinear round and triangular pipes with identical cross-sectional areas were used in the work. Flow pulsations from 3 to 15.8 Hz were generated by means of a rotating damper. The degree of turbulence of pulsating flows varied from 0.03 to 0.15 by installing stationary flat turbulators. The working environment was air with a temperature of 22-24 ^оC moving at a speed of 5 to 75 m/s.RESULTS. Experimental data on instantaneous values of velocity and local heat transfer coefficient of stationary and pulsating air flows with different levels of turbulence in straight pipes with different cross-sectional shapes were obtained. CONCLUSION. It has been established that the presence of gas-dynamic non-stationarity leads to an increase in the degree of turbulence by 47-72% in a round pipe and by 36-86% in a triangular pipe. The presence of gas-dynamic non-stationarity causes an intensification of heat transfer in a round pipe by 2635.5% and by 24-36% in a triangular pipe. It has been shown that a significant increase in the degree of turbulence leads to an increase in the heat transfer coefficient of pulsating flows in a round pipe by 11-16% and, conversely, a decrease in the heat transfer coefficient by 7-24% in a triangular pipe. The obtained results can be used in the design of heat exchangers and gas exchange systems in power machines, as well as in the creation of pulsed action devices and apparatus.