Vol 20, No 1 (2021)

The paper presents a new correlation-regression model of estimating the turbofan engine weight considering the effect of the engine’s design schemes and dimensions. The purpose of this study was to improve the efficiency of the conceptual design process for aircraft gas turbine engines. Information on 183 modern turbofan engines was gathered using the available sources: publications, official websites, reference books etc. The statistic information included the values of the total engine air flow, the total turbine inlet gas temperature, the overall pressure ratio and the bypass ratio, as well as information on the structural layout of each engine. The engines and the related statistics were classified according to their structural layout and size. Size classification was based on the value of the compressor outlet air flow through the gas generator given by the parameters behind the compressor. Depending on the value of this criterion, the engines were divided into three groups: small-sized, medium-sized gas turbine engines, and large gas turbine engines. In terms of the structural layout, all engines were divided into three groups: turbofan engines without a mixing chamber, engines with a mixing chamber and afterburning turbofan engines. Statistical factors of the improved weight model were found for the respective groups of engines, considering their design and size. The coefficients of the developed model were determined by minimizing the standard deviations. Regression analysis was carried out to assess the quality of the developed model. The relative average error of approximation of the developed model was 8%, the correlation coefficient was 0,99, and the standard deviation was 10,2%. The model was found to be relevant and reliable according to Fisher's test. The obtained model can be used to assess the engine weight at the stage of conceptual design and for its optimization as part of an aircraft.

A method is proposed for assessing the results of adjustment maneuvers for a nanosatellite (NS) with an electrothermal propulsion system (ETPS). Using the example of the SamSat-M nanosatellite under development, common causes of maneuvering errors associated with deviations in the manufacturing of the propulsion system are revealed. Probabalistic analysis of the NS maneuvering process was carried out. The design parameters of the ETPS are considered as random factors. Statistical models of the distributions of all random factors are assumed to be equally probable, which is the worst-case scenario, since the true distributions of the design parameters of the ETPS are unknown. The methodological basis of the study is the method of statistical modeling (Monte Carlo method) followed by the use of regression and factor analysis, on the basis of which the influence of the scatter of each of the design parameters on the controlled parameters is determined. Requirements for the design parameters of the ETPS that affect the spread of the projections of the velocity growth vector of the NS and the arising angular motion have been formulated. The presented results can be used to assess the influence of production deviations in the design parameters of propulsion systems on the nature of spacecraft motion, as well as to state requirements for the spread of design parameters to ensure the achievement of the objective.

In the article the authors present a method of restrained elastomer bending of aircraft sheet parts with curved sides. Manufacturing of a part is carried out in two transitions; as a result of the first transition a part with thinning in the radial part is obtained, the second transition is carried out on the mold block of reduced height, as a result of which the resulting wave of excess material deforms along the radius of the bending mandrel. In the finished part, we can observe an increase in the thickness of the workpiece in the zone of the bend radius. Numerical studies of the process were conducted using the ANSYS/LS-DYNA software complex. As part of the study, the process flow model was worked out, the distribution of thickness of the material of the part over the entire surface under consideration was obtained, and graphs were plotted showing the elastomer pressure distributions and the deformation of the material of the part at characteristic points.

The article considers the challenge of studying the mechanical properties of composite sandwich constructions at the interface between the base layers and the lightweight core. The results of strength tests are presented for specimens of sandwich-core panels with coats made of high-strength carbon fiber-reinforced plastics (CFRP) and polymer honeycomb core considering various loading conditions. It is noted that a discrepancy in the values of shear stresses occurs in four-point bending and shear tests due to the complex stress-strain state of the specimens during bending. In order to interpret the experimental data, numerical analysis of the area of contact interaction between the coats and the filler of the sandwich-core composite structures is carried out. It is noted that in the presence of significant normal stresses in the adhesive coat the base layers separate from the core during shear tests and there is underestimation of the values of shear stresses by about 20%. Recommendations for the assignment of ultimate shear stresses for the use in practical design of sandwich-core composite constructions are put forward.