Statement of the problem in a general form. Modernization of medium- and high-speed diesel engines at the current stage is reduced to increasing their energy efficiency with simultaneous strengthening of environmental requirements to combat global warming. This process involves not only a change in the structure and technical characteristics of vehicles, but also a transition to the use of alternative types of fuel. In our paper, we explore the key technical aspects of this transition, including fuel systems and their adaptation to the new requirements of today's medium- and highspeed diesel engines. The results of our research will reveal important information about the improvement of diesel fuel systems, contributing to the improvement of their operational efficiency and compliance with the new standards.

Formulation of the problem. The resource of a marine diesel engine before overhaul depends mainly on the state of the crank mechanism, and the crankshaft is the main link in this mechanism. Crankshafts are among the most critical parts of engines and are operated under conditions of variable loads. Shaft journals are subject to sliding friction at high speeds and high specific pressures. The crankshaft is one of the most important expensive engine parts (its cost is more than 10% of the cost of the entire engine) - to a large extent determines its resource [1-3]. During the operation of such complex and expensive units as internal combustion engines, sudden failures occur, which are caused by parts with defects that require replacement or restoration, and in most cases the necessary technologies for this are not available.

When modeling connected kinematic pairs in mechanical engineering, when designing complex connected surfaces, including ship hardware, it became necessary to develop fundamentally new methods for forming connected conical surfaces that exclude interference during design.

Of all, when calculating structures in which a cantilever beam is used as an elastic element, it is not correct to solve this equation for the finite section by successive approximation of the transcendental equation. The exact solution of the differential equation leads to the transcendental equation in elliptic integrals of the 1st kind. From this equation, it is possible to determine the angle of rotation of the final section θk by the method of successive approximations, that is, in fact, by selection. For practical purposes, for example, when designing elastic elements of variable stiffness, it is necessary to have an explicit formula for the dependence of vertical displacement on the applied force. We differentiate the dependence of the reduced vertical displacement of the beam’s end on the reduced load. Then we will take the inverse value from it. As a result, we get a graph of the reduced stiffness, which fits almost perfectly into the square parabola y = 3 + x2. The internal energy of deformation of the previously unloaded and undeformed cantilever beam was determined. In order to verify this mathematical model, a comparison of the results of the nonlinear calculation with the results of the finite element calculations based on the traditional model and the one proposed in the work was performed. It was established that formulas (1) - (4) can be used when the displacement of the rod element does not exceed 80% of its length, which is a very significant geometric nonlinearity. The size of the stiffness matrix in the finite element method (FEM) is determined by the degree of discretization of the system. In practical tasks, the number of elements in the stiffness matrix is calculated by hundreds of thousands or millions. It is always a highly sparse matrix with a large number of zero elements.

Currently, there are two trends in the development of vaporcompression refrigeration systems (VCRSs). First, the use of "natural" refrigerants (propane R290, isobutane R600a), which contributes both to an increase in the cooling coefficient of vapor compression refrigeration equipment and to a decrease in greenhouse gas (GHG) emission [1]. However, the list of refrigerants for marine refrigeration is limited therefore this task is complex [2, 3]. The prospect “natural” R600a and R290 are forbidden to be used in the vessel’s refrigeration equipment (except the cases when the mass of the refrigerant charge is less than 150 g), as they are class A3 hazard refrigerants (fire hazardous) [4]. The second is the use of nano additives to the working fluids of vapor compression refrigeration systems to increase their efficiency without modernization.

Основними генераторами енергії на суднах морського та внутрішнього водного транспорту є двигуні внутрішнього згоряння (дизелі). Однієї з систем, що забезпечують їх функціонування, є система мащення. Двотактні суднові дизелі використовують дві системи мащення – лубрікаторну (за допомогою якої мастило подається на стінки циліндрової втулки) та циркуляційну (мастило в якої спрямовується до підшипників колінчатого валу). Чотиритактні (середньообертові) дизелі комплектуються лише циркуляційною системою мащення, в якої мастило потрапляє до всіх контактних вузлів дизеля, основними з яких є пари тертя поршневе кільце – втулка циліндра та вкладиш підшипника – колінчатий вал

Marine diesel engines (as the main component of a marine power plant) are sources of environmental pollution with exhaust gases, which include toxic components: carbon dioxide CO, hydrocarbons CnHm, soot C, sulfur oxides SOX, nitrogen oxides NOX [1-3]. Nitrogen oxides NOX occupy the first place among harmful emissions in almost all operating modes of diesel engines, regardless of their type, size and design features. Emission of nitrogen oxides with exhaust gases marine diesel engines is regulated by the requirements of Annex VI MARPOL. In accordance with the Tier-I, Tier-II, Tier-III standards (which apply to diesel engines of ships built after 2000, 2011 and 2016), the maximum amount of NOX in exhaust gases should not exceed the values determined by special expressions

In modern conditions, the market needs changes in the logistics of food supplies (feed and grain) based on an assessment of the capabilities of producers, ports and other types of transport. In addition, the elevator capacity within the country should allow the necessary reserves to be accumulated. If we estimate the export potential of agricultural enterprises located in a 300-kilometer zone, from where grain can be efficiently delivered by road transport to the ports of the Sea of Azov (Mariupol and Berdyansk), it amounts to 3.2...3.5 million tons [1]. For the period from July 2020 to May 2021, grain exports (excluding processed products) from Mariupol and Berdyansk amounted to 2.3 million tons through the ports of the Sea of Azov, including the Mariupol port

The problem of reducing greenhouse gas (GHG) emissions in the maritime sector are currently important. The share of shipping emissions in global anthropogenic emissions was 2.89% in 2018 [1]. The main contribution to GHG emissions (indirect emission) on the marine fleet generates the main and auxiliary engines, and boilers during fuel combustion as well as incinerators [1, 2]. However, marine merchant and passenger ships have another significant source of direct GHG emissions, which is currently not directly regulated and considered as not mandatory inventory – hydrofluorocarbons (HFCs) refrigerants emissions from refrigeration and air conditioning systems. It should be highlighted, that reduction of the direct GHG emissions for marine refrigeration systems is the most difficult among all types of refrigeration systems.

The problem of increasing of combustion efficiency for a heat engine (diesel, gas turbine, etc.) has been solved for about a century, because economic, power and environmental indicators depend on it. In addition, which is no less important in relation to the stated indicators, the efficiency of combustion and the rate of fuel burnout in the specified coordinates at the designated time interval in the combustion chamber determine strict requirements for the used fuels in terms of thermophysical parameters that affect atomization, evaporation, and mixing with oxidizer . Hence, there are restrictions on the use of alternative fuels for heat engines, such as gas condensate, etc.