COMPUTATIONAL AND EXPERIMENTAL STUDIES OF THE AREA OF SUSTAINABLE COMBUSTION OF NATURAL GAS WITH AIR

One of the rational ways of creating low-emission combustion chambers is the organization of low-temperature lean combustion with external heating of the components before they are fed into the combustion chamber. When organizing lowtemperature lean combustion with large excess air ratios, problems may arise with ensuring a stable position of the flame front. Combustion stability to a large extent depends on the ratio of the average flow rate and the rate of turbulent combustion. The rate of turbulent combustion depends on the composition, pressure and temperature of the components supply and the degree of turbulence in the combustion chamber. The average flow rate depends on the excess air ratio (oxidizer and fuel consumption) and the geometric dimensions of the chamber. Earlier it was shown that when developing a low-emission combustion chamber with low-temperature lean combustion, it is advantageous to use the relative flow rate as a generalized characteristic of the intra-chamber process, which takes into account the consumption, geometric and thermodynamic parameters in the combustion chamber. This work is devoted to the analysis of stable combustion of a fuel composition natural gas + air based on the experimental data available in the public domain by the authors from the University of Michigan (USA). With the help of the methods developed by the authors, the experimental data on the limiting feed rates of the components into the atmospheric burner were processed. The limiting flow rates of air and natural gas, the limiting values of the excess air ratio, the longitudinal values of the speed of the fuel-air mixture and the limiting values of the relative flow rate are obtained and analyzed. Areas of stable combustion by the listed parameters at different degrees of air swirl are graphically presented.

DESIGN OF THE MOUNTING BRACKET FOR THE OPTICAL SOLAR SENSOR OF THE SPACECRAFT USING TOPOLOGICAL OPTIMIZATION

Object of the research is a bracket of solar sensor mounting of spacecraft. Goal of the research is to reduce mass of the spacecraft bracket subject to strength and thermal resistance considerations. Mass reduction is carried using topology optimization based on SIMP-material model (Solid Isotropic Material with Penalization). Optimization problem statement is compliance(or strain energy) minimization subject to volume constraint. For strength and thermal analysis finite element method is used implemented in Ansys Workbench 18.2 software. As result of topology optimization, a material distribution data inside a design domain is obtained for different volume fractions. Based on that result new CAD-model has been developed using Siemens NX software which taking into account manufacturing constraints and providing manufacturing of the designed part using machining. Structural analysis performed for two load cases corresponds to launch regime and maximum lateral acceleration has shown that optimized structure has sufficient strength. Thermal analysis performed in Steady State Thermal software module has shown that thermal resistance requirement also met. As result of proposed research bracket mass reduction of 2.5 times has been achieved. Directions of future work has been outlined. Improvement of proposed method may consist from incorporating of coupled thermal-structure analysis into topology optimization process.

NUMERICAL INVESTIGATION OF A TONE NOISE OF THE FAN WITH CASING TREATMENT

Numerical investigation of influence of a slot-type casing treatment on acoustic and aerodynamic characteristics of the fan of ultra-high bypass ratio turbofan is presented. The investigation was performed using NUMECA FINE/Turbo solver. NLH harmonic method was used to simulate the effect of casing treatment on unsteady flow field in the turbomachine. Two operational conditions were investigated – “sideline” and “approach”. The attention for the first operational condition was paid for aerodynamic characteristics. Significant influence of casing treatment on them was found especially near the surge line. At the “approach” operational conditions the attention was paid for the proper calculation of tone noise. It was shown that the installation of casing treatment leads to decrease of power of tone noise radiated through the inlet. However the power of the tone noise, radiated through the nozzle, and also the overall power of tone noise increase.

IMPROVEMENT OF NUMERICAL METHODS FOR CALCULATING HYDRO-MECHANICAL DEVICES OF AIRCRAFT AUTOMATION

The article is devoted to the consideration of the main problems of mathematical modeling and the most rational presentation of the results of numerical research of hydro-mechanical regulators of aircraft at the stage of practical design. Traditionally, the analysis and synthesis of hydraulic automation devices of aviation systems are performed on the basis of linear frequency methods of the theory of automatic control, which allow us to obtain approximate characteristics: accuracy, stability, controllability. The main task in this case is to develop such assumptions and solutions that would allow solving the problem in an analytical form. However, the number of nonlinear problems completed by analytical methods is negligible. In such a situation, computer modeling becomes an alternative. Mechanization and partial automation of the computational experiment led to qualitative changes in the simulation results and allowed us to obtain generalized diagrams of the dynamic state of the studied systems. Using a specific example, the issues of algorithmic modeling, analysis and numerical study of the dynamic characteristics of the automatic control system of aircraft on transient modes are considered. The paper clearly demonstrates how the application of the generalized variables method helps to present the results of numerical experiments in a rational form and to determine the influence of parametric complexes on the main characteristics and to construct generalized dynamic characteristics according to the main quality criteria

DEVELOPMENT A MATHEMATICAL MODEL FOR RESEARCHING DYNAMIC PROCESSES IN THE LABYRINTH SEAL OF CENTRIFUGAL COMPRESSOR STAGE

Research of dynamic processes occurring under real operating conditions of centrifugal compressors often require the use of interdisciplinary approaches. This is determined by the character of the processes, which significantly affect each other during the compressor operation. However, when using interdisciplinary approaches, there are difficulties in the numerical implementation. They are associated with the need to take into account all the geometric and physical features of the processes under research, which leads to significant time and computational costs. At this article discusses issues related to the causes of oscillatory processes in the centrifugal compressor stage, in particular, in the labyrinth seal channel. In the article using 2FSI approach allowing to take into account the bilateral interaction of physical process on another. The article discusses issues related to the causes of oscillatory processes in the centrifugal compressor stage, in particular, in the labyrinth seal channel. The computational domain of research is presented, conceptual and mathematical statements are performed, which allow describing, among other things, self-oscillatory processes using the 2FSI approach.

SOLID PROPELLANT REQUIREMENT ANALYSIS FOR JET MOTOR POWDERED FUEL SUPPLY SYSTEMS

The existing sources of the operating fluid used in aviation and rocket-space technology are analyzed. The disadvantages of inert gas cylinders used as a source of the operating fluid of the component supply system in jet engines are considered. An alternative to the gas pressure system is a low temperature solid propellant gas generator (LTGG) with a coolant. Controllable powdery components supply scheme of an air-breathing engine (ramjet) is proposed. The principle of operation of such a feeding scheme is described. To ensure the stability of the output characteristics of the LTGG, a valve system is used. The requirements for the gas source and combustion products (CP) involved in the operating process have been determined. The analysis of the existing methods of cooling the CP is carried out. It was revealed that the low-temperature solid-propellant gas generator with a powdery capacitance coolant meets the most fully the above requirements, the principle of operation, which is based on the heat transfer wave localization effect. Solid propellant with the following composition: 38 % AP + 38 % Octogen + 24 % SKI-NL is selected. The CP temperature, at a pressure in the combustion chamber of 6 MPa, is 1545 K, and the CP gas constant is 459.4 J / kg·K, the condensed phase is absent, and the water vapor content in the operating fluid does not exceed 1.6 %. The combustion of the proposed propellant produces a significant amount of combustible components – 60 % CO, 4 % H2, > 1 % CH4. The use of valves on cold gas ensures the reliability of the controlled supply system of powder components, and, accordingly, the entire engine. Based on the results of the work, conclusions were made about the correspondence of the obtained parameters of solid propellant and LTGG to all the requirements set.

INVESTIGATION OF THE GRID MODEL AND TURBULENCE MODEL PARAMETERS INFLUENCE ON QUALITY OF TURBINE ROTOR BLADE TIP CLEARANCE AREA AERODYNAMIC PROCESSES MODELING

Aerodynamic processes mathematical modeling is carried out using numerical methods. Now the level of development of software numerical methods of three-dimensional gas-dynamic modeling of processes in turbomachinery makes it possible to determine with high accuracy the main characteristics of units at the design stage. It significantly reduces the time and cost of production. This article proposes a methodology for installation and improving the mathematical and grid model of HPT rotor blade to improve the quality of three-dimensional modeling. Aerodynamic processes mathematical modeling in aircraft turbojet engine blade rows is carried out using numerical methods. Grid model settings and turbulence model significantly affect the results qualitative characteristics and the calculations duration. This article proposes a methodology for grid model constructing based on local intense vortex formation and flow mixing places thickening. The influence of the grid and turbulence models parameters are estimated on the kinetic energy losses amount and secondary flows structure. The design model includes the building geometric model, preparation of the grid model and description of the turbulence model. Influence of grid and BSL and SST turbulence models on results of turbine blade aerodynamic calculation is considered in this article. Basic recommendations for the construction of mathematical and grid models in the ANSYS for uncooled rotor blades have been developed.

PERM SCIENTIFIC SCHOOL OF BEARINGS FOUNDED BY PROFESSOR BORIS ALEXANDROVICH IVANOV

The article is devoted to the 100th anniversary of the birth of an outstanding teacher and scientist, professor of the Perm Polytechnic Institute (PPI), now PNRPU, Boris AlexandrovichIvanov, one of the founders of the PPI, a participant in the Great Patriotic War. Boris Alexandrovich graduated from the Kazan Aviation Institute and defended his PhD thesis in 1956; since 1957 he became the head of the department"Machine Parts". Since 1963, the department began to develop a scientific direction-the study of the performance of mainly aircraft rolling bearings. After the All-Union Congress on Machine Reliability held in Perm in 1964, Boris Alexandrovich introduced a section on reliability to the course "Machine Parts". In 1965, on his initiative, a section of reliability and friction units was created at NTO MASHPROM, in which the staff of the department held scientific and technical conferences every two years with the wide participation of specialists from different cities of the country. Scientific and technical seminars with reports were held every quarter, mainly from the enterprises of the city. A brilliant lecturer and educator-teacher of young employees, Boris Alexandrovich paid great attention to improving their pedagogical and scientific qualifications, especially supported the independent work of young people. Under the leadership of Boris Alexandrovich, eleven candidate dissertations were completed and successfully defended, he was confirmed in the title of professor and honored worker of the higher school. So the Perm School of Bearing Workers, well-known in the country, was created. Boris Alexandrovich has always remained in the memory of grateful students.

GAS INFLUENCE IN GAPS OF LABYRINTH SEALS ON THE ROTOR DYNAMIC STATE

When transporting natural gas over long distances, it is necessary to build gas compressor stations that compensate for the gas energy losses due to friction. The uninterrupted supply of natural gas to consumers depends on their reliability. Current trends in increasing power with a simultaneous decrease structure stiffness leads to the occurrence of previously unpredictable oscillations of the compressor rotor. The article describes the main causes of compressor rotor vibrations and some methods of dealing with them. Due to the limitations of the considered phenomena with this methods, the article proposes the use multiphysics modeling of gas and structure interaction using the 2FSI approach. Simulation performed for a simplified labyrinthseal compressor rotor model. To solve the problem, the ANSYS software product was chosen, which implements the 2FSI method. The calculations were carried out on a high-performance computing complex PNRPU. For the model structure, an analysis of natural frequencies is performed and a Campbell diagram is constructed. The trajectories analysis of a point on shaft rotation axis at different rotation frequencies of the rotor is carried out. The influence of the imbalance on the dynamics of the system is noted. Further, the results of numerical modeling of the structure taking into account gas dynamics are presented and the results comparison by dynamic modeling of the structure is carried out. To identify the factors influencing the rotor dynamics, taking into account gas dynamics, numerical calculations were carried out with various options for taking into account the effect of gravity and imbalance.

OBJECT-ORIENTED APPROACH IN THE DESIGN OF AIRCRAFT HYDRAULIC AUTOMATION DEVICES

The article proposes a new direction of rationalization of the numerical study of complex hydromechanical devices for automation of control systems, associated with the use of methods of object-oriented technologies (OOT). As is known, simple linear methods are poorly suited for the practical design of technical devices. The static characteristics here are nonlinear, the form and even the content of the models depend on the parameters of the mode, the links can interact with each other (from the permutation of non-linear links – the result can be different), etc. The ideal solution for the synthesis of such systems would be to create complete libraries of elements with the subsequent generation of systems according to certain rules. However, a direct synthesis of nonlinear systems from initial structures is apparently not realistic. Taking into account a large number of factors and phenomena often leads to “tuning” the model to the characteristics of a particular drive, and not to an increase in the accuracy of modeling the hydraulic drive under consideration. To solve specific problems, a certain simplification of the model is permissible, which makes it possible to obtain the desired result with lower computational costs. Compared to traditional methods, the object-oriented classification of hydromechanical devices favorably facilitates the design process, since it becomes possible to flexibly take into account many factors and further study them, as well as solve multi-parameter problems. The concept of standardization in this case is vague: we mean a clear hierarchy of models, the same designations, dimensions, etc., which makes the models the same in form, leaving them unique in essence. Knowing the properties and characteristics of the main elements of the aircraft hydroautomatics systems that make up the synthesized system, it is possible to design systems with predictable properties in advance. In the general case, the problem of selection is reduced to the determination of the parameters according to the corresponding model, provided that the requirements and restrictions are met at this stage.