Vol 22, No 4 (2021)

Hydrodynamic surfaces with midsection in the form of Lame curve

Karnevich V.V.

Abstract

General representation of ship geometry is given by the method of slicing the ship hull by three mutually perpendicular planes: vertical symmetry plane which runs along the middle of hull width, horizontal plane which divides the hull into underwater and abovewater parts, and vertical plane perpendicular to the other two which coincides with midsection. By taking the same three predefined sections of the theoretical hull shape, it is possible to obtain three algebraic surfaces of different order, which are called hydrodynamic in this article. By introducing alphabetic parameters to signify orders of ship skeleton main curves and then by giving them various numerical values, it is possible to consider a large number of hull shapes, having only three explicit surface equations. Method of deriving the equations, obtained by other authors, using only three explicit algebraic equations is demonstrated. The proposed technique is illustrated on six new ship hull shapes.

RUDN Journal of Engineering Research. 2021;22(4):323-328
pages 323-328 views

Analysis of antifreeze properties before and after their operation in engine

Telkov O.I., Kosmacheva A.D., Khodyakov A.A., Khlopkov S.V., Danilov I.K.

Abstract

The results of diagnostics of antifreeze indicators before and after their operation in an internal combustion engine are presented. The chosen direction of research is relevant, since it allows one to predict not only the change in the properties of antifreeze during its operation, but also to obtain evidence of the course of metal corrosion processes. The purpose of the study - to conduct control tests of antifreezes before and after their operation in an internal combustion engine, that ensures the maintenance of the power unit in good condition. The objects of study were fresh AGA Z-40-G12++ antifreeze (release of 2021; A-21) and coolant AGA Z-40-G12+ (release of 2012; AE-12) after its operation for several years. It is shown that the pH, density, viscosity, electrical conductivity of the coolant samples before and after its operation are different. It was found that the course of the dependences of electrical conductivity σ on temperature t for samples A-21 and AE-12 is the same. The dependence of σ on t is described by a polynomial (quadratic) model. It has been suggested that higher values of the AE-12 hydrogen index may indicate the occurrence of electrochemical corrosion of metals, which, in the process of contact with antifreeze, form short-circuited galvanic pairs. With the help of a complete factorial experiment, it was demonstrated that higher pH values of used antifreeze can be a reflection of the degradation of the properties of monoethylene glycol and the ongoing processes of metal corrosion.

RUDN Journal of Engineering Research. 2021;22(4):329-338
pages 329-338 views

Features of modeling a highly efficient multistage vapor compression heat pump unit

Antipov Y.A., Shatalova I.I., Shkarin K.V., Lapin M.V., Sokolov D.A., Grinin A.O., Toptygin K.P.

Abstract

The increase in the cost of fuel and energy resource and the deterioration of the environment from the combustion of traditional fossil fuel, have led to a great interest in energy-saving technology by using secondary energy resources in the thermal energy of industrial, housing and communal services using heat pump units in Russia and abroad. This paper analyzes the well-known two-stage heat pump units, and reveals their advantages in comparison with single-stage. The modeling of a highly efficient multistage vapor compression heat pump unit is proposed. Moreover, a method for calculating a multistage heat pump unit with a high coefficient of performance is presented. In addition, an example of calculating the thermodynamic cycle of a four-stage heat pump unit is presented. The influence of the number of stages on the increase in coefficient of performance in relation to a single-stage heat pump unit, the effect of the temperature difference between the temperature of the high-potential heat source and the temperature of the low-potential heat source on the coefficient of performance were analyzed. In addition, the influence of the initial value of the temperature of the high-potential heat source before heating during the course in the heat pump unit on the value of coefficient of performance for a different number of stages is analyzed under the condition of a constant difference between the heating temperature of the high-potential heat source at the outlet of the heat pump unit and the temperature of the low-potential heat source.

RUDN Journal of Engineering Research. 2021;22(4):339-347
pages 339-347 views

Development of a composite structure for biomechanical purposes

Borisov I.M., Reznik S.V.

Abstract

The development of a new design of a leg prosthesis for interaction with inclined surfaces is of interest to provide a new level of comfort for people with disabilities. Based on the analogues and modern works in the prosthetics sphere, tree concepts of the prosthesis design are proposed. Spatial models of surfaces and solid models have been created. To confirm the operability of structures and determine the stress-strain state that occurs when interacting with a surface having a slope of 15° relative to the horizontal plane, the finite element method is used on spatial models of four variants of geometry. A comparative analysis of various variants of the prosthesis design under the same conditions is carried out. The results obtained showed that this design solution is workable, suitable for production and for 14.4% more efficient than standard designs with one slot in the spring element and 44.5% more efficient than designs without slots in the spring elements.

RUDN Journal of Engineering Research. 2021;22(4):348-354
pages 348-354 views

On the way to autonomous navigation

Volodin A.B., Presnov S.V., Yakunchikov V.V.

Abstract

The national aspects of readiness and the tasks of introducing autonomous (unmanned) navigation in the near future are considered. The purpose of the study - identification of economic benefits and risks, problem areas of implementation of autonomous navigation technologies. The economic benefit is based on a reduction in the costs of paying the crew of the ship, living on board it, reducing losses from accidents. If the question “what?” has already been answered - the installation of autonomous navigation systems is available for naval vessels today, then the question “why?” has not yet been resolved. If the main benefit is expected from a reduction in crew, then a noticeable reduction in crew is possible only for newly built and relatively modern vessels with an auto- mation level of at least AUT2, the share of which under the flag of the Russian Navy is about 15%. At the same time, the modernization of existing inland navigation vessels into autonomous vessels is now available for less than 2% of the river transport fleet (vessels with an automation level of A1), which suggests that autonomous inland water transport only has to be built. The risks also include the slow pace of construction of new ships, as well as retraining and further employment with a massive reduction in the crew of ships. Foreign and domestic experience of the initial stage of autonomous navigation implementation is considered.

RUDN Journal of Engineering Research. 2021;22(4):355-363
pages 355-363 views

General planetary vehicle and industrial space necklace “Orbit” as an alternative to rocket near space exploration

Unitsky A.E., Pronkevich S.A., Artyushevsky S.V., Looksha V.V.

Abstract

The paper presents an alternative to rockets − general planetary vehicle (GPV) and industrial space necklace “Orbit” (ISN “Orbit”), which are a single complex necessary for the non-rocket near space exploration. The authors analyzed the conceptual design of the GPV and ISN “Orbit”, described their main characteristics, compared the impact of the GPV and launch vehicles on the Earthэs ecology. The principle of the GPV movement is based on centrifugal forces arising from the GPV acceleration in the plane of the equator. This is the main difference from rocket engines, which principle of operation is set up on the use of jet motion. The differentiation in the operation principles of the GPV and launch vehicles leads to serious variety in the energy required to lift the GPV to the near-Earth orbit and, accordingly, the variety in cost per payload ton. The concept of the ISN “Orbit” is described. The complex should serve as a basis for the removal of harmful industry to the near-Earth orbit and become a launching pad for active expansion into space. The GPV and ISN “Orbit” are effective means for the complex and progressive solution of environmental problems on Earth and productive implementation of space direction.

RUDN Journal of Engineering Research. 2021;22(4):364-372
pages 364-372 views

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