All articles. Vestnik MGTU

Estimation of the bearing capacity of a threaded pair made of needle-punched frame/pyrocarbon matrix-based carbon-carbon composite materials

Thu, 15 Oct 2026 00:00:00 +0400

The paper describes experimental investigation of the bearing capacity of threaded fasteners made of carbon-carbon composite materials based on a needle-punched frame and a pyrocarbon matrix. The bearing capacity of a single-screw threaded pair under normal as well as extreme temperatures was estimated. The strain diagrams were obtained and processed. In the experiment simulating loading on one turn of a threaded joint, dependence of the shear strength of the material depending on the shear area size was studied. The scale effect influence on the shear strength of the material was determined. The results obtained were compared to those obtained for threaded fasteners made of spatially reinforced carbon-carbon composite materials.
EDN: KULPPZ, https://elibrary/kulppz

Experimental determination of the friction force in a low-speed, long-stroke, grease-free stage

Mon, 19 Oct 2026 00:00:00 +0400

It is determined that the mechanical losses in the slow-speed stage, despite the large pressure drop (? = 100), are less than the mechanical losses in high-speed compressors. It is recommended to take the power spent on overcoming the friction forces in the sleeve cylinder piston seal equal to 10–15 % of the indicator power of the stage. Since there is only one friction unit in the low-speed stage, the power required to overcome mechanical friction is equal to the power expended to overcome the friction forces in the sleeve cylinder piston seal. The mechanical efficiency of the slow-speed stage is in the range of 0.89–0.92, which corresponds to the mechanical efficiency of high-performance gas engine compressors having a common shaft with a drive. The total isothermal efficiency of a low-speed long-stroke stage lies in the range of 0.50–0.95, while for high-speed compressors the total isothermal efficiency lies in the range of 0.60–0.75. The friction force caused by the forces of the material’s own elasticity and expander pressure was also determined for various cylinder diameters.
EDN: VSACVC, https://elibrary/vsacvc

Physicochemical analysis and modeling of combustion processes of mixed fuels in a diesel engine

Mon, 19 Oct 2026 00:00:00 +0400

The article presents a comprehensive numerical mathematical modeling of the combustion processes of composite fuels in a diesel engine. The research focuses on a detailed thermodynamic and kinetic analysis of the combustion of both traditional diesel fuel and its blends with ethanol and oleic acid, representing vegetable oils. The calculation of key parameters was carried out under conditions of competitive chemical reactions for oxygen: changes in internal energy and entropy, reaction initiation temperature, and combustion rates. The modeling was performed considering the polytropic character of the process and the changing temperature. It is shown that the introduction of ethanol increases the overall combustion rate of the mixture compared to pure diesel fuel. At the same time, the addition of oleic acid leads to a non-linear decrease in the process rate, although the effect is partially compensated by the temperature rise in the combustion chamber. The obtained results are of practical value for optimizing the composition of composite fuels and adjusting the operating parameters of a diesel engine to improve its efficiency and environmental performance.
EDN: PAXHRF, https://elibrary/paxhrf