Vol 21, No 1 (2022)
- Year: 2022
- Articles: 10
- URL: https://journals.ssau.ru/vestnik/issue/view/538
Full Issue
AIRCRAFT AND SPACE ROCKET ENGINEERING
Isotopy of spacecraft compartment hull shapes
Abstract
The goal of the work is to research the case of isotopy of spacecraft compartments in the problem of on-board equipment location. A definition of this engineering topological property is given in the article. The most frequently used spacecraft compartment hull shapes and various compositions of their casings are considered. Also, general strategies of taking decisions that determine the choice of modeling technologies and performance factors are discussed. A method of comparing various layouts on the strength of the object location performance factors was developed. The problem of on-board equipment accommodation is solved. Generalized mathematical models of performance factors are presented. Design models and diagrams are constructed. The results obtained make it possible to upgrade algorithms of accommodation.
7-13
Influence of space vehicle remote power supply on thermal regimes of solar batteries
Abstract
The issues of ensuring the functioning of an additional energy-receiving channel for the onboard power supply system of a low-orbit spacecraft are considered. To compensate for the shortage of electricity on board the spacecraft, various options for remote power supply from the system of space power stations transmitting energy to the solar battery by laser radiation during periods of its forced inactivity are possible. Long shadow-sunlight periods of time are a distinctive feature of functioning of low-orbit spacecraft. During these periods the solar battery is idle, and, in addition, even in the daylight portion of the spacecraft's orbit, the energy output from the spacecraft may be reduced to almost zero during the operation of some special systems that require special modes of spacecraft orientation. Reception of energy from a CES with energy flux density higher than that of the solar flux may lead to overheating of the solar battery panel of conventional design, a decrease in its efficiency and even to its failure. Therefore, the analysis of thermal modes of reception and conversion of laser radiation energy which affect the energy efficiency of the solar battery is an important aspect of remote power supply. Relationships of a mathematical model for estimating the available power supply from the solar battery operating in the mode of optimizing control of its power are proposed. The results of approbation of the model for maintaining the safe thermal mode of the solar battery panels during remote power supply of the spacecraft are presented.
14-23
MECHANICAL ENGINEERING
Reconstruction of fan blade dynamic loading prior to its fracture
Abstract
To maintain the functionality of fan blades, it is important to know the distribution of dynamic stresses in the blade, their amplitude and vibration frequency. Understanding of the dynamic loading pattern will allow us to determine under what conditions the engine was operated, to identify and prevent emergencies that could lead to the blade fracture. The purpose of this work is to understand the cause of the fan blade fracture that occurred during the engine ground start. Due to fractographic analysis of blade fragments it was revealed that the fracture occurred due to the initiation of fatigue cracks in blades. The place of crack initiation and parameters of crack growth were established, spectral analysis of the fracture was carried out. To establish the reason of fatigue crack initiation it was necessary to determine the dynamic state of the blades during their destruction. The sections of the second stage of stable crack growth, during which fatigue striations are formed, were determined using the fractographic method. Using the spacing of the fatigue striations and Paris's law, the crack stress intensity range was determined. Modeling of crack propagation in the blade was carried out to define the stress state. The ability to determine the stress intensity factor at each step of crack growth and its comparison with research data made this work possible. The simulation showed under what conditions manifold increase in stresses occurs and made it possible to obtain the expected value of vibration amplitude. Additional modal analysis showed a resonant form that caused the fatigue nature of crack propagation. The demonstrated approach established crack growth conditions and revealed the cause of blade fracture.
24-33
Strength calculation of parts based on stress state stiffness
Abstract
In the framework of this research it is shown that strength calculation of the most critical parts requires taking into account the parameter of stress state stiffness determined by the G. A. Smirnov-Alyaev. A method for estimating the level of strain of parts and diagnosing the most critical zones of parts based on dimensionless energy and complex criteria is proposed. The effectiveness of the method that can be used not only to diagnose critical zones, but also to optimize the geometric parameters of the design of critical parts, is shown.
34-41
Gasdynamic and strength improvement of the axial flow turbine of a helicopter gas turbine engine
Abstract
The article presents the results of the development of proposals to increase the safety margin of the blades and the efficiency of a single-stage axial flow turbine compressor of a small-sized turbo-shaft engine being modernized with the use of multidiscipline optimization methods. Analysis of the initial version of the turbine showed that the margin of safety of the working blades is significantly lower than that required by the strength standards. To eliminate the problem encountered the task of blade development was initially solved only according to strength characteristics, without taking into account gas dynamic processes. As a result, the geometry of the working blades that met the strength requirements was obtained. It was used as a starting point for solving the joint task of optimizing the blading, taking into account gas dynamic and deformation processes. As a result of joint optimization, a turbine version meeting the strength standards was obtained, although we had to slightly reduce the efficiency of the turbine by 0,2%.
42-56
The nature of change in the residual stress-strain state of dovetail lock joints, taking into account nonlinear strains
Abstract
A general algorithm for calculating residual stresses based on the method of successive loadings is presented. The process of formation of residual stresses and strains in dovetail lock joints during its loading by centrifugal forces and subsequent unloading is simulated. The problem is solved in non-linear statement taking into account the elasticity, plasticity and creep strains. The fields of residual stresses and deformations in the grooves of the disk are obtained. The numerical solution of the problem was performed by the finite element method in the ANSYS software package. The influence of the opening angle α on the nature of plastic strain zoning is analyzed. The opening angle α was changed in the range from 45° to 70°. It was established that with the development of creep strain, there is a change in the zone of nonlinear deformations and the nature of the distribution of residual stresses in the zone of the concentrator. The dependences of the value of maximum residual stresses on the opening angle α, as well as their variation over time, are obtained.
57-66
On the efficiency of using the Navier-Stokes approximation in thermogasdynamic calculation of low-thrust liquid-propellant rocket engines at low Reynolds numbers
Abstract
A numerical method for thermogasdynamic calculation of low-thrust liquid rocket engines is presented. These engines are used as end organs of the system of space attitude control for nanosatellites and small spacecraft. The method is based on the use of the TERRA software package for thermodynamic calculation and the Ansys CFX software package for gas-dynamic calculation using the Navier-Stokes equations. The results of the thermogasdynamic calculation, as well as the flow pattern of the working fluid in the chamber, are presented. The results of validating the described method are also presented. Its capabilities and limitations are analyzed. The validation procedure is based on the comparison with the results of experimental data on the Reynolds number and the momentum thickness.
67-80
Mathematical model for calculating pressure in a pulsating combustion chamber
Abstract
Due to insufficient knowledge of the processes occurring in the chambers of pulsating combustion, as well as lack of mathematical dependencies that make it possible to fully describe the parameters of such chambers, the authors of this article present a model for calculating pressure fluctuations as a function of time. The resulting dependence is based on the fact that the combustion of fuel takes place according to an isochoric cycle, whereas the outflow of gas through a resonant tube is an isothermal process. The conditions for applying the mathematical model and its features are described. With the help of the above dependence, it is possible to trace the dynamics of pressure changes during the operation of a pulsating combustion chamber with different geometric parameters. A program is presented that implements the obtained dependence for calculating and comparing the obtained theoretical data with the studies of other authors.
81-90
Increasing the sensitivity and expanding the functionality of bipolar analysis of rotary machine vibrations
Abstract
Vibration-acoustic diagnostics of rotary machine defects is the most effective method for non-destructive testing of their technical condition. Practice shows that its successful use largely depends on a set of available methods for analyzing vibration processes. Gears are the most common and heavy-duty components that largely determine the overall vibratory condition of a machine. There is quite a variety of methods for vibration-based diagnostics of gear defects. They include an interesting method of bipolar analysis which consists in separate analysis of the positive and negative parts of a vibration signal with subsequent formation of the diagnostic indicator in the form of differences, ratios, etc. The method is aimed at assessing the quality of gearbox assembly by the position of the tooth contact pattern. Limited area of use and low sensitivity is a disadvantage of this method. The paper shows that the use of broadband vibration maxima in the application of bipolar analysis in vibration-based diagnostics of rotary machine defects significantly increases its efficiency. Using the example of wear of tooth flanks in the “sun gear – satellite gears” pair and the value of the backlash in the differential gearbox of a turboprop engine, it was found to be ensured by increasing the sensitivity of the method and expanding its functionality. In our analysis, we used statistics of gearboxes with different degrees of wear of the tooth flanks and repaired gearboxes with different backlashes. In this case, a wide set of well-known diagnostic indicators can be used: intensity of n-dimensional vectors of informative series, parameters of individual harmonics, amplitude modulation depth, probabilistic characteristics in selected frequency bands, dimensionless discriminants, cepstra, etc. The paper presents some examples of these methods.
91-98
Model of virtual balancing of rigid rotors
Abstract
Rotor imbalances have a significant impact on the level of their vibration and reliability. Reduction of rotor imbalances is achieved through static and dynamic balancing that we propose to accomplish by virtual balancing of rigid rotors in two stages. At the first stage mutual orientation of the rotor parts is calculated to compensate their imbalances and couple unbalance. At the second stage the values of the masses and angular coordinates of two correction weights that allow eliminating the residual imbalance of the rotor are determined. The correction weights are placed in two balancing planes of the rotor. A model of virtual balancing is proposed to implement the balancing stages. The model makes it possible to determine the relative angular positions of the rotor parts, the values of the mass of two correction weights and their angular coordinates in the balancing planes. The effectiveness of using the proposed model was verified by performing calculations using the finite element model (FEM) of the rotor in the ANSYS software package. In the course of the study, data were obtained on the values of vibration velocities on the rotor supports. The results obtained show a significant reduction in the vibration velocities of the supports, amounting to 80% of their initial value.
99-109