Vol 22, No 4 (2021)

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.

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.

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.