Vol 21, No 2 (2022)

The Engine Air Particle Separator is considered to be the most important element for maintaining the performance of helicopter engines when operating in dusty air conditions. The intensity of erosion of the elements of the gas-air passage of the gas turbine engine depends on many factors: on the hardness and chemical composition of dust particles, on the fractional composition, sand concentration, engine operating condition etc.Therefore, the development of a method for selecting the optimal values of the Engine Air Particle Separator parameters is a complex multi-criteria and multi-factor task. The present document addresses the selection method of optimal values (geometric dimensions) of the Engine Air Particle Separator parameters in aviation gas turbine engines. The methodology includes six main steps. The choice of optimal values of the Engine Air Particle Separator geometrical parameters is accomplished taking into account three partial criteria for the Engine Air Particle Separator efficiency: the degree of air purification, pressure loss and mass. The Engine Air Particle Separator parameters are selected using the Pareto method. An example of choosing the optimal values of the geometric parameters of a cyclone Engine Air Particle Separator is considered.

The gearboxes of aircraft gas turbine engines are their most stressed parts. One of the main gearbox defects is the tooth flank wear that causes resonant oscillations in engine structure elements. This defect is generally assessed using vibroacoustic diagnostics methods. It is noted that the currently existing recommendations on setting limit values for diagnostic indicators do not take into account the type of mathematical models that describe their dependence on the defect size. This can result in its uncontrolled development. We have shown that for the case under consideration, four kinds of mathematical models were earlier obtained to describe dependences of diagnostic indicators on the wear value: linear, power, exponential and combined (linear and exponential) models. The linear model is characterized by a constant rate of change in the level of a diagnostic indicator with the growth of wear. For power and exponential models the growth of wear leads to an increase of the rate of change in the diagnostic indicator value. The combined model is characterized by the presence of two zones of change in the diagnostic indicator intensity with the growth of wear: the constant rate zone and the zone of increasing rate. The use of diagnostic indicators with a continuous increase in their intensity depending on the growth of wear will require ensuring constant control of the gearbox vibration state, which is not always feasible. We give recommendations for setting standard values of the diagnostic indicator intensity for the considered models.

This article provides an overview of the latest developments in the field of hybrid additive manufacturing of metal parts. The concept and various kinds of additive manufacturing are discussed.  Special attention is paid to hybridization of additive technologies and various processes of forming: die forging, deep drawing, and others. The background and significance of the technologies, as well as their applicability in production are presented. The combination of additive manufacturing with forming processes is carried out with a dual purpose: to expand the area of application of additive manufacturing and overcome its limitations associated with low productivity, metallurgical defects, surface roughness and lack of dimensional accuracy; new application of traditional forming processes.

High heat generation in the hydrodynamic wedge is one of the main factors limiting application of pad journal bearings as bearings for rotors of aircraft gas turbine engines. The goal of the research is to study the influence of the oil supply method on the bearing thermal state and to determine the design factors reducing the bearing temperature. The study was carried out with the use of bearings with diameters of 100…320 mm with different design of the oil supply: through oil dispensing grooves in the pads, through oil nozzles in the inter-pad space, using lead-in chamfers for the pads, with oil bypass channels. The tasks posed were solved by using volumetric geometric models with the tools of computational fluid dynamics in the ANSYS CFX package in which differential equations describing the model are solved by the finite element method. The patterns of temperature and pressure distribution over the surface of the lower, most loaded bearing pad were obtained for various options of oil supply and different geometry of bearing pads; values of the bearing load carrying capacity, maximum pressure in the working gap, the oil mass flow through the elements of the oil supply; dependences of the bearing static performance on the distance between the shaft and nozzles. Oil supply through oil dispensing grooves made in pads is a factor that negatively affects the bearing thermal state, which is associated with so-called “locking” of the working gap. It is shown that implementation of oil supply through the space between the pads is more efficient. The use of a lead-in chamfer with plain inserts simplifies oil supply to the working gap. The design solutions described make it possible to reduce the maximum oil temperature in the bearing by 3…6 degrees Celsius.

Parts of rolling bearings lubricated with low-viscosity fluids are subject to intense wear of the working surfaces. The bearing life cycle under these conditions depends on the wear rate of the friction surfaces. Therefore, it is important to establish the relationship between the wear rate, the change in the clearances and the duration of work. This paper presents the results of wear tests for rolling ball bearings. After the tests the radial and axial clearances were measured, their changes and the duration of operation were analyzed. Having determined the path of friction, the wear rates of the bearings were calculated based on the values of changes in the radial and axial clearances. The wear rate of the bearing on the axial and radial clearances was plotted against the reduced (equivalent) load. The obtained dependences were approximated with a confidence of at least 98%. The obtained analytical expressions allow us to perform express calculations for changes in the bearing clearances. This will make it possible to forecast the bearing service time, taking into account the wear of the working surfaces under specified conditions, while ensuring correct functioning of the support assembly.