Vol 19, No 1 (2020)

It is shown that analyzing the signals from “standard” sensors of gas-turbine engine shaft speed we can resolve some issues of diagnostics of the technical condition of the reduction gearbox without installing any additional vibration transducers. It was found, in particular, that the vibration spectrum component generated by the wear of the differential reduction device’s gear teeth causing resonant oscillations of the turbocharger blades produces torsional vibration at the appropriate frequency. The analysis of the parameters of the instantaneous rotational speed of the reduction gear output link (the shaft of the rear screw) made it possible to obtain some diagnostic indicators of the value of the reduction gear teeth wear on the basis of evaluation of the frequency deviations’ variance. It was established that the value of the diagnostic indicator is linearly dependent on the value of wear. The norm for this indicator was established for the engine under investigation. Significant influence of the load on its level was shown.

The paper deals with ensuring the accuracy of integrity of spacecraft components’ reference surfaces at various stages of design. It is shown that the main problem consists in the fact that the accuracy of integrity of the reference surfaces of the components making up the complex is maintained in the framework of the internal structure of a part. We propose a method of control over ensuring the accuracy of integrity of spacecraft components’ reference surfaces at various stages of design in the framework of their external structures. The method is implemented by introducing the coordinate system of the complex into the scheme of the complex of components that perform interrelated service functions. Concepts and definitions are introduced in the framework of the method that make possible formal representation of accuracy of integrity of the components’ reference surfaces in the form of a set of pairs of points the appropriate annotated dimensions are fixed on. Graphical interpretation of the method at the stages of development of technical requirements for the components is presented. An example of potential implementation of the method at the stage of design documentation development is given.

Dynamic designs of tandem space launch vehicles are calculated according to the standard
OST 92-4548-85. The eigenmodes and eigenfrequencies of the elastic structure are calculated using the MSC Nastran or a similar program. We propose an addition to the existing methods of calculating dynamic designs of liquid-propellant rockets with account for their elasticity applying a method oriented towards operational generation of input data for developing systems of stabilizing their motion. We developed a procedure containing calculation of eigenmodes and eigenfrequencies of missile body elastic modes and the coefficients of impact of the elastic modes and surplus degrees of freedom. To demonstrate the method’s efficiency, in taking down the results for tandem launch vehicles in the analytical form the OST formulas are re-derived. In validating the proposed method of calculating design schemes we obtained results practically coincident with the already applied formulas for the range of tasks under examination. The versatility of the proposed method is illustrated by calculation of coefficients absent from the OST because the factors influencing rocket dynamics are not taken into account in the standard. The proposed method is distinguished by its generality, which allows describing various types of launch vehicles while taking into account all significant factors that influence the dynamics of their motion.

The article presents the results of weight and size optimization of a high-pressure turbine working disk for an augmented turbofan. The issues of modeling the operation of the engine’s first stage with a cover plate providing the delivery of cooling air to the blades are considered. Strength calculation of the stresses arising from the action of centrifugal forces under high-temperature conditions was carried out. A three-dimensional model of the disc was obtained. The finite element method was used. The pattern of temperature distribution in the disk body was obtained on the basis of heat calculation.  Based on the strength calculation, the stresses and strains of the turbine disk were determined.  Maximum stresses in the disc are located at the junction of the disc frontal area and the cooling air feed holes. Plastic deformation is observed in the area of the cavities for cooling air feed. It is shown that the stepped part of the disc should be made of a material with lower heat resistance and a higher value of permissible limit stress. Based on the study, a bimetallic disk design made by powder metallurgy was proposed.

The algorithm of the turn of the spacecraft from an initial arbitrary angular position at an arbitrary angular rate to a solar-oriented attitude is investigated. Minimum essential equipment of the motion control system required for the purpose of ensuring maintenance of solar orientation is defined: a solar sensor, a single-axis angular-rate sensor, low-thrust liquid rocket engines. A solution of the problem of defining the spacecraft angular rate vector by the measurements of the deviation of the optical axis of the solar sensor from the sun vector and the single-axis angular-rate sensor is presented. The conditions under which control action on the rocket engines for the purpose of changing the value of the angular-rate vector for the Sun to get into the field of viewing of the solar sensor or for the spacecraft stabilization are defined. Mathematical modeling of the spacecraft attitude control system with the unknown initial state vector of motion is carried out. The results of mathematical modeling confirmed the efficiency of the proposed algorithm in terms of reducing propellant fuel consumption and high-speed performance. In comparison with the known methods of solving the problem of reducing angular speed (a lengthy process with the use of a magnetic system or a fast process with the use of a three-axis angular-rate sensor and rocket engines) the duration of the process of reducing angular speeds is the same as in normal operation, however, at the same time the problem of bringing spacecraft into the solar –oriented attitude is solved.

In this article we present our solution of the problem of cyclic compression of a single-layer and multi-layer corrugation, as well as of a single-layer multi-span corrugation by the FEM method using Ansys. This problem can be considered as the first part of the general complex nonlinear problem of cyclic compression of a multi-layer multi-span corrugated package with dry friction on the contact surfaces. We conducted an analysis of the known published solutions to this problem, and we discovered inaccuracy of some of them and the physical reason resulting in this unacceptable error. A very large number of published solutions to this problem are generally explained by the presence of successful examples of their practical application in the field of aircraft and rocket engine manufacturing, by the wide possibilities of their use as damping devices in both of these areas, and, for example, in the automotive industry, by their high elastic-friction, strength and performance characteristics. All the known published solutions to this problem were obtained for cyclic compression of a multilayer multi-span package in the region of its elastic deformations and for the same geometric shape of the corrugation. The task of improving the mass characteristics of an engineering unit is quite relevant for the development of shock-proof single-shot damping devices that increase the passive safety of the car – bumper protective devices. This can be solved by using single-layer or two-layer, multi-span packages with an optimally selected geometric shape of the corrugation, deformable in the elastic-plastic region. Therefore, the above-mentioned problems are solved taking into account the elastic-plastic deformation of the corrugations for any of their geometric shapes. The obtained solutions make it possible to construct any loading processes in the field of elastic-hysteresis package loops. We also investigated the influence of the parameters of the corrugated package on its elastic-friction characteristics (including the shape of the corrugation and the presence of gaps between the tapes of the package at the tops of their corrugations).