The paper presents the results of simulation of loss coefficient and the angle of flow at the outlet of diffuser in centrifugal compressor vaneless diffusers. The calculation was performed in a wide range of design and gas-dynamic parameters by means of neural networks. Also, an analysis performed by CFD (Computational Fluid Dynamics) methods is presented. In order to obtain mathematical models, a data sampling was used for vaneless diffusers with the following characteristics: relative width is b 2 / D 2 = 0.014 – 0.1, outlet relative diameter is D4 / D2 = 1.4 – 2.0, inlet flow angle is 2 α2 = 10 – 90 º, velocity coefficient is λ c2 = 0.39 – 0.82, Reynolds numbers corresponding to them are Re b2 = 87 500 - 1 030 000. In order to improve the accuracy of simulating using neural networks, various recommendations on the preparation and processing of initial data were collected and tested: identification of conflict samples and outliers, data normalization, improving the quality of the neural networks training under the insufficient amount of sampling, etc. Application of the listed recommendations and an essential expansion of mathematical models definition significantly improved the accuracy of simulating. A simulation experiment based on neural models for studying the influence of dimensions, diffuser shape, and similarity criteria made it possible to check the physical adequacy of mathematical models, to obtain new data on energy conversion processes and to establish a number of recommendations on the optimal design of vaneless diffusers.

Objective. The aim of the study is to generalize the accumulated experience of fuzzy situational control based on a compositional hybrid model of a complex technical system in the form of an algorithm and, on this basis, to form recommendations on the methodology for the formation and identification of situations, determining parameters and solutions for managing a complex technical system under conditions incomplete data to improve the accuracy of control decisions. Method. The use of a compositional hybrid model solves the problem of describing and modeling the system in conditions of incomplete data and the impossibility of obtaining information about the entire range of the system's operation. Fuzzy situational control makes it possible to develop control decisions in accordance with the chosen control strategy and take into account the specifics of the system thanks to the compositional model. Result. An algorithm for fuzzy situational control of complex technical systems based on compositional hybrid models is proposed. The stages, features, advantages and disadvantages of fuzzy situational control for this type of systems are considered. The procedure for determining and unambiguously identifying emerging fuzzy situations for the system is given, and a method for analyzing and developing typical control strategies is also considered. The compositional hybrid model of a complex technical system considered in the article describes the operation of the experimental compressor unit ETsK-55. Conclusion. The main advantages of the developed fuzzy situational method for managing complex technical systems include: integration of the control system with existing elements of the system; better use of available resources; adaptability and reliability of a control method based on fuzzy situational networks and a composite hybrid model of the system. Management strategies have been defined to meet the customer's requirements for product quality, as well as the safety of personnel and equipment, trouble-free production and saving resources.