###### Abstract  
The operation of injection apparatus in self-ignition engines results from the design, manufacturing technology and wear and tear during operation. The technical state of the injector apparatus significantly affects the engine performance, fuel consumption, toxicity and smoke opacity of outlet gases. The most unreliable element of the injection apparatus is the injector nozzle, the quality of which depends on the quality of construction and production, operating conditions and the of the fuels used, etc. One of the design parameters of the injector nozzles, determining the technical state is the geometry of the nozzle holes. An attempt was made to optimize the selection of the dimensions and surface condition of the spray holes to significantly affect the flow properties of the injector nozzles and, consequently, to decide on the size and form of fuel dosed streams to individual cylinders of a self-ignition engine and the quality of fuel atomization. In work, a simulation model was developed, and the pressure losses and the mass fluid of the injected fuel were minimized for selected significant geometric features, taking into account the influence of operating conditions. With the use of Mathematica software, simulation optimization methods and methods based on evolutionary algorithms were elaborated. M pacs: 10.Jm, 11.7341. +
Footnote †: journal: Applied Sci. These are elements with a complex structure, high precision of workmanship and the required high durability. The introduced design changes and modernization of the engines produced require the improvement of the manufacturing technologies used. The purpose of these changes is to increase the maximum combustion pressure and mean effective pressure, reduce specific fuel consumption and increase durability and reliability. The requirements for injector nozzles can be divided into design and technological. Design requirements are related to the functions, operation of the injector nozzle, durability and reliability, as well as interchangeability and standardization. Technological requirements, which determine the quality and cost of execution, include the possibility of obtaining high dimensional accuracy and surface smoothness as well as small errors in shape and position. Studies have shown that many injectors are damaged in the initial period of operation [5; 9]. The reason for such a situation may be the initial unfitness or low durability, which may result from the conditions of production, transport and storage [2; 10]. The analysis of the quality control requirements of the manufactured injectors has shown that they are not very credible and not uniform. The modern state of the technology of producing nozzles does not ensure their hydrodynamic similarity because the dispersion of their geometrical dimensions is difficult to determine by means of industrial quality control methods [2; 9]. One of the design dimensions of nozzles, determining their technical state, and at the same time subject to intensive wear, are the geometric features of the spray hole [9; 11; 12; 13; 14; 15]. Changing the dimensions and condition of the spray hole surface significantly affects the flow properties of injector nozzles, and this, in turn, determines the size and form of fuel jets dosed to individual cylinders of a diesel engine and the quality of fuel atomization. Many investigations have shown that the nozzle hole geometry and its internal flow characteristics play an essential role in the spray formation [2; 12; 16; 17] and combustion process [7; 8; 14; 18]. This article intends to present a simulation model of the injector nozzle structure of a marine engine, which is part of the fuel injection subsystem. The main task is to develop a modern model, considering the latest theoretical and numerical achievements, of a marine engine injector nozzle.