The paper presents the design and development of a low-temperature Stirling engine with the external heat supply, intended for autonomous cogeneration power systems. The engine utilizes thermal energy from a solar collector, which heats the working fluid to temperatures ranging from 90 to 100 °C. A key innovation of the proposed system lies in the significantly increased swept volume of the displacer, which exceeds the volume of the power piston by a factor of 20 to 40. This configuration enables a stable engine operation under relatively low temperature differentials between the heater and the cooler. Experimental investigations, supported by numerical modeling, confirm the feasibility and efficiency of the proposed design. Under operating conditions with a temperature differential of approximately 65 to 75 °C and a working fluid pressure up to 0.3 MPa, the engine demonstrates a mechanical output ranging from 5 to 15 W and a corresponding thermal efficiency of 2 to 4
Cast alloy steel grade 35KhGSL is widely utilized in various industries. Sometimes, wear resistance and hardness become highly essential for different machine parts. Additions of ultradispersed powders in melt as modifiers, external impact on crystallizing alloy are two important approaches to enhance the mechanical characteristic. In this work, a combination of ultrafine modifier in the form of titanium carbide TiC and mechanical vibration was used for the first time on cast alloy steel grade 35KhGSL in order to study changes in hardness and wear resistance. The method of introducing a modifying additive into the melt is indicated. The analysis has been carried out based on hardness, tribological properties, and microstructural characterization. The microstructural was analyzed using metallographic microscope and scanning electron microscope (SEM) analysis. In addition, the Vickers microhardness values were measured, and dry abrasion test was conducted to check the steel's variation in hardness and tribological characteristic after treatment. The combination of mechanical vibration of the crystallizing melt with the simultaneous introduction of titanium carbide powder maximized the hardness of 285 HV (by 36
The paper presents the spectral mode analysis of the proposed fiber-optic security system (FOSS) and achievements in processing the data from fiber-optic sensors, design and operating principles of the proposed system. The paper focuses on the cost reduction and simplification the FOSS design, while maintaining its high efficiency. The use of single-mode optical fiber of the G.652 type, allows increasing the protected perimeter length up to 40 km, providing the resistance to external influences. The proposed software is used to analyze changes in the light spot, recording mechanical effects in real time. The program supports several operating modes, including automatic adaptation to changing conditions, which minimizes the number of false positives. The FOSS demonstrates the high accuracy in laboratory conditions, which confirms its potential for use in the protection of extended objects.
This paper examines the behavior of environmentally hazardous hexavalent chromium (Cr(VI)) during the production of chromium-containing ferroalloys. Based on the evaluation of changes in Gibbs free energy, the oxidation of trivalent chromium in ore at the top of the smelting furnace to hexavalent chromium is shown to be possible due to interaction with atmospheric oxygen in the workshop and lime added during the process. It is hypothesized that the likelihood of Cr(VI) formation inside the furnace itself is low, due to the strictly reducing nature of the ferrochrome production process. The presence of Cr(VI) in slags is believed to result from the interaction of relic ore minerals containing trivalent chromium, such as Cr₂FeO₄ and Cr₂MgO₄, with atmospheric oxygen during slag tapping and transportation in ladles to waste disposal areas. Comprehensive thermodynamic modeling involving industrial slags and carbonaceous reducers has demonstrated the feasibility of converting all chromium and iron oxides into a metal phase consisting of chromium and iron carbides, similar to carbon-rich ferrochrome. It is recommended to agglomerate slag wastes containing Cr(VI) with bitumen prior to smelting. Bitumen serves not only as a binder but also as a reducing agent. Experiments conducted in a high-temperature furnace have confirmed the feasibility of implementing this technology in industrial conditions.
Concepts such as reuse, repurposing, upcycling, remanufacturing, and re-powering can be applied to the reuse of combustion engines from passenger cars and trucks in stationary or mobile machines, such as power generators. Technical, economic, environmental, and research analyses indicate that such solutions may be justified; however, their implementation is limited by homologation and emission regulations. In most countries, there are no specific rules governing emissions from power generator engines, while in the European Union, such engines are categorized as mobile generators (portable or trailer-mounted) subject to Stage V (Reg. 2016/1628/EU), stationary generators (permanently installed) subject to the MCP Directive (2015/2193/EU), and emergency generators (limited operation) partially exempt from MCP but requiring registration. Consequently, engines recovered from road vehicles do not meet formal or technical emission compliance requirements for power generators and can only be used under conditional approval for research, experimental, or temporary purposes. This reveals a paradox of modern environmental policy: although reusing functional engines from dismantled vehicles could embody the principles of a circular economy, restrictive emission standards (Stage V, MCP, NSPS) effectively prevent such technological recycling. Addressing this issue requires legislative action and the development of simplified testing methods for used engines in new applications. This article is the first to systematically demonstrate that current Stage V, MCP and NSPS emission frameworks create a regulatory paradox that prevents the circular-economy reuse of functional automotive engines, and it proposes a dedicated secondary type-approval pathway enabling their legal and environmentally controlled application in power generators.
