Vol 22, No 1 (2023)

The article considers the problem of optimizing a long-haul aircraft flight under uncertainty of objectives and tasks. Based on the analysis of the well-known flight mode selection criterion, two main objectives of the flight were identified – minimizing fuel consumption and flight endurance. The study of this criterion based on a multi-purpose approach made it possible to develop an analytical model of the performance indicator containing two objective functions and a weight coefficient as a measure of comparative importance between the identified objectives. It is shown that the weight coefficient in the tasks of flight efficiency research is a measure of the uncertainty of the tasks. Consideration of the weight coefficient role in the optimization problem objective function made it possible to develop operational and trajectory methods for selecting flight modes. In the developed statement of the problem, the problems of cruise flight optimization and climb and descent modes are considered. The paper introduces the concept of the optimal cruise range as a vertical separation criterion, which allows you to rationally design the flight path at different flight levels under the uncertainty of tasks. The procedure for researching the efficiency and optimization of flight has been conducted and demonstrated by the method of mathematical modeling. The results of optimizing the flight mode are compared with the typical flight modes recommended by the flight manual. The introduced methods of flight efficiency investigation can be helpful in developing recommendations of long-haul aircraft operation. The methods and principles of a multi-purpose approach, operations research and decision theory were used in the paper. The long-haul aircraft IL-96-300 was selected as the object of research.

The paper presents the results of one of the stages of creating a model of assessing and forecasting the operating characteristics of a transonic compressor due to erosive wear. A numerical model of a transonic compressor stage is constructed and verified to substantiate its applicability in calculating various degrees of blade erosive wear. The article contains a review of the basic approaches for turbulence simulation, their application area and basic features connected with 3D-flow simulation in turbomachines. The parameters and settings of the numerical model are shown. The CFD-obtained results are presented and compared with the experimental data and results of other researchers. By this comparison the accuracy of the CFD-obtained overall performance and the quality of modeling local processes are determined. Possible ways of improving the model’s accuracy are also specified.

The features of a nonlinear model of the “indenter-coating” tribosystem of a tribometer are considered. It is shown that with an increase in the amplitude of harmonic perturbation, the dynamic system goes through the stage of doubling the cycle and passes into the regime of deterministic chaos. At the exit from chaos, it is possible to establish various synergistic regimes that stably retain their parameters even with a multiple decrease in the amplitude of the disturbance. A block diagram of the implementation of the evolutionary model is presented. As a result of the formation of equilibrium roughness, the motion of the system is a strange attractor. To substantiate the randomness of the strange attractor, an analysis of the amplitude-frequency characteristic of the ideal regenerative delay element with a gain factor less than unity, was carried out. The physical meaning of the strange attractor is that in a cyclic mode, a nonlinear dynamic system whose cycle time exceeds the period of natural oscillations by more than two orders of magnitude cannot come to the beginning of a new cycle with exactly the same parameters as to the beginning of the current cycle.

Numerical modeling for the purpose of receiving the temperature field of cooled rotor blades and its improvement is an integral process of modern design of gas turbine engines since the issue of cooling at gas temperature at the combustion chamber outlet over 1800-2000 K is becoming one of the key ones. To ensure the specified parameters of turbine operation during its design, it is necessary to obtain reliable calculation data. The article presents an algorithm for forming a calculation model to determine the thermal state of the working blade of a high-temperature high-pressure gas turbine in the Ansys program. The process of preparation of geometric and grid models is described, the boundary conditions used to set up the project in Ansys CFX Pre are given. A method for determining the cooling efficiency factor using Ansys CFX Post is also presented. The distributions of the temperature field and the coefficient of cooling efficiency over the surfaces of the blade to be cooled are obtained. Integral values of the coefficient of cooling efficiency for the designed blade at various cooling air flow rates were compared with statistical data. On the basis of the comparison a conclusion was made that the working blade considered in the work corresponds to the modern level of cooling efficiency.

The paper discusses the features of machining of a compressor blade airfoil. The problem of airfoil deformations under the action of residual stresses that negatively affect the accuracy of the relative position of the airfoil relative to the blade root is discussed. Methods of compensating for the effect of permanent deformations on the accuracy in blade machining and the impossibility of using this approach when the compressor blade is included in the duplex mode technology of electrochemical machining are specified. The analysis of the pattern of electrochemical machining of the blade airfoil with adjustment of the auxiliary technological base developed by the authors and the use of segmented electrodes showed the effectiveness of its use in order to compensate for airfoil deformations. We suggest measuring the interelectrode gaps in the machining chamber after refixturing the base in order to reduce the total machining time. We also suggest using the modernized electrochemical machining scheme when designing a CNC machine for the machining of a blade airfoil.