No abstract

In the digital stage of world development, information is constantly expanding its facets. That is why the exchange of information is a leading component of constant change in life. Although humanity is gradually moving to the use of electronic technology, acoustic information still plays a key role in information circulation. This applies to official communication in public institutions up to the highest level, business contacts in commercial structures and private communication between people. The process of transmitting information in acoustic form has dangerous consequences. The use of appropriate devices, such as directional acoustic microphones or technical intelligence acoustic antennas, which may be outside the scope of the information activity, makes it possible to obtain unauthorized information that should not reach third parties. Therefore, the task of detecting and protecting information leakage channels, including acoustic ones, is gaining a new degree of importance every day. The protection of the premises or building, where acoustic information regularly circulates, provides a set of organizational and technical measures and means of protection of information circulation, taking into account the peculiarities of the location and arrangement of the object. This study involves the study of the dependence of the level of the acoustic signal on ways to prevent leakage of information through the acoustic channel, which includes vibration noise by means of technical protection and coverage of improvised materials (shielding) of enclosing structures of information activities (OID). The experiment determines the degree of influence of density, sound-absorbing properties of materials and their combinations on acoustic oscillations, the source of which is in the OID. The object of the study was a basic room, where the enclosing structures are walls with windows and doors, ceiling and floor. It is also worth noting that the acoustic signal measurements were not performed in complete silence, which directly affected the accuracy of the results. This step was taken in order to best reproduce the conditions in which criminals often work.

Self-oscillations are one of the common problems in the complex automatic system, that can occur due to the features of the workflow and the design of the governor. The development of digital control systems has made it possible to damp self-oscillations by applying complex control laws. However, for hydromechanical systems, such way is unacceptable due to the design complexity and the governor cost. The objective of this work is to determine the parameters of the hydromechanical free turbine speed controller, ensuring the absence of self-oscillations during ground tests of the turboshaft engine with a hydraulic dynamometer. The TV3-117VM engine (Ukraine) with the NR-3VM regulator pump (Ukraine) was selected as the object of the study. However, self-oscillations can also occur in any modifications of the TV3-117 engine with any NR-3 regulator pump. The results of the research may be of interest to engineers and scientists who investigate the dynamics of automatic control systems for similar engines. The paper analyses the nonlinear features of the empirical characteristics of the FTSC leading to self-oscillations of the engine speed. The authors propose the mathematical model of the automatic control system dynamics, which takes into account all the features of the engine and regulator pump. It is shown that the load characteristics of the water brake and the helicopter main rotor can differ significantly. Research of the dynamic characteristics of the TV3-117VM engine was carried out. The analysis showed a good agreement between the calculation results and the field test results, and made it possible to determine the parameters of the controller, which lead to self-oscillations during test. Two cases are considered. The first case includes ground tests of the engine with a water brake; the second case—flight tests of the engine as part of the helicopter’s power plant. The data obtained make it possible to develop recommendations for adjusting the hydromechanical governor without testing it on the engine.

In connection with increasing intensification of the working process in a gas turbine engine and increasing requirements for economy, the problem of defining and monitoring the main parts lifetime is becoming more vital. Modern algorithms of the monitoring systems are based on taking into account the levels of part temperature and total equivalent stress throughout the flight cycle. Thermal and stress-strain states of the critical zones of the main parts are determined on the basis of information received from the sensors installed in the engine gas path. Turbine disks are located in the internal cavities of the engine and are cooled by air from the compressor. However, in some designs, the disk cavity can be separated from the place of cooling air bleed by several stages of non-contact labyrinth seals, which will lead to some delay in changing the parameters of the cooling air flow when changing the engine operating mode. It has been observed that if this situation is not taken into account, it can lead to significant errors (more than 40%) in determining the lifetime for the peripheral zone of the disk. At the same time, this error is minimal for the hub and the middle zone of the disk, and the existing monitoring algorithms can be used.

In modern aircraft engine technology, there is a tendency to replace the mechanical drive of external gear fuel pumps with an electric one. This significantly reduces the integral energy consumption for pumping fuel (kerosene). On the other hand, in order to reduce the dimensions of the structure, it is reasonable to increase the rotation speed of the pumping unit gears. The above considerations make it advisable to study the problems that may arise in the design of pumping units. Analysis of the existing designs of external gear fuel pumps shows that the flow processes in the meshing zone have a significant impact on the pump performance and lifetime. Incorrect truss plate geometry and the compensation system lead to an increase in the velocities when opening and closing the cavity in the meshing zone, which causes intense cavitation. To understand the causes and factors which influence this phenomenon, it is necessary to study the fluid flow behavior in the meshing zone gaps. High-speed cameras are used to experimentally study the flow behavior. However, this approach gives only a qualitative result but does not allow for determining the absolute values of pressure and load in terms of the angle of rotation. Nevertheless, high-speed surveying can be used as a basis for fluid flow model verification. In this paper, the model of the fluid flow in a high-pressure external gear pump was proposed. The verification of the simulation results for HDZ 46 HLP 68 oil operation was carried out according to the results of experimental data visualization. The influence of rotation speed on the position of cavitation zones was revealed and confirmed by operational data. The analysis of the flow process in meshing for kerosene as a working fluid was carried out.