АКУСТИЧНА ПОМІТНІСТЬ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ З СИЛОВОЮ УСТАНОВКОЮ, ЩО МІСТИТЬ ЕЛЕКТРОДВИГУН І ПОВІТРЯНИЙ ГВИНТ

2020 ◽  
pp. 81-94
Author(s):  
В. В. Руденко ◽  
В. П. Чернолихова
Keyword(s):  
Power Plant ◽  
Electric Motor ◽  
Acoustic Radiation ◽  
Spectral Characteristics ◽  
Experimental Studies ◽  
Noise Spectrum ◽  
Acoustic Characteristics ◽  
Acoustic Signature ◽  
Constant Pitch ◽  
Static Conditions

The presence in operation of many prototypes of UAVs with propeller propellers, the use of such devices at relatively low altitudes and flight speeds makes the problem of reducing the noise generated during UAV flights urgent both from the point of view of acoustic visibility and ecology.The main source of the UAV's acoustic signature is its power plant, which includes the engine and propeller.The tasks of this work, the solution of which requires the implementation of experimental studies, include the determination of the power, spatial and spectral characteristics of the acoustic fields of propeller driven power plants of UAVs with an electric drive. The propeller is one of the main sources of acoustic radiation produced by the power plant. The influence on the acoustic characteristics of the power plant was investigated: changes in the diameter of the propellers with a constant pitch, changes in the number of blades and the number of revolutions (peripheral speeds of the propeller). The possibility of reducing the noise produced by the propeller by changing the nature of the noise spectrum was considered. The rotor rotation noise, especially of its five first harmonics, is one of the most noticeable parts in the noise spectrum of a propeller engine installation. Therefore, a hypothesis was considered and put into practice to reduce the acoustic signature of UAVs by reducing the noise of these components due to their shift to the region of higher frequencies, at which sound vibrations in the air decay faster. A comparison technique is proposed. The measurements were carried out under static conditions, in the KhAI anechoic chamber. Note that the propellers involved in the experiments operated at Reynolds numbers (Re0.75 <1*105), which can significantly affect its aerodynamic and acoustic characteristics. An empirical formula was obtained for the 11 × 6" «Aero-naut» propeller, which makes it possible to estimate the noise produced by this propeller when designing for a given flight mode in a given direction. The possibility was considered in the future to have a database of frequently used propellers. The contribution of harmonic noise components was considered propeller in the direction of its radiation. The contribution of the brushless electric motor to the intensity of acoustic radiation of the UAV power plant is determined. It is noted that the main contribution to the noise of a power plant with a brushless electric motor is made by the propeller. At the same time, the noise of a brushless electric motor can significantly increase in the range of 2 ... 3 kHz with wear of rolling bearings.

АКУСТИЧНА ПОМІТНІСТЬ БЕЗПІЛОТНИХ ЛІТАЛЬНИХ АПАРАТІВ З СИЛОВИМИ УСТАНОВКАМИ НА БАЗІ ПОРШНЕВИХ ДВИГУНІВ

2020 ◽  
pp. 62-80
Author(s):  
В. В. Руденко ◽  
И. В. Калужинов ◽  
Н. А. Андрущенко
Keyword(s):  
Control System ◽  
Internal Combustion Engine ◽  
Power Plants ◽  
Combustion Engine ◽  
Spectral Characteristics ◽  
Experimental Studies ◽  
Internal Combustion ◽  
Detection Range ◽  
Acoustic Signature ◽  
Static Conditions

The presence in operation of many prototypes of UAVs with propeller propellers, the use of such devices at relatively low altitudes and flight speeds makes the problem of noise reduction from UAVs urgent both from the point of view of acoustic imperceptibility and ecology.The aim of the work is to determine a set of methods that help to reduce the visibility of UAVs in the acoustic range. It is shown that the main source of noise from the UAV on the ground is the power plant, which includes the engine and the propeller. The parameters of the power plants influencing the processes that determine the acoustic signature of the UAV were investigated. A comprehensive analysis of the factors affecting visibility was carried out. The power plants include two-stroke and four-stroke engines, internal combustion and two-blade propellers. The use of silencers on the exhaust of the internal combustion engine was considered. The spectral characteristics of the acoustic fields of the propeller-driven power plants for the operating sample of the UAV "Eco" were obtained. The measurements were carried out in one-third octave and 1/48 octave frequency bands under static conditions. The venue is the KhAI airfield. Note that the propellers that were part of the power plants operated at Reynolds numbers (Re0,75<2*105), which can significantly affect its aerodynamic and acoustic characteristics. It is shown that when choosing a UAV control system, one should take into account the fact that two-stroke piston engines are the dominant source in the noise of propeller-driven control systems in the absence of a hood and mufflers in the intake and exhaust tracts. The use of a four-stroke internal combustion engine significantly reduces the noise of the control system. In the general case, the position of the boundaries of the zone of acoustic visibility of a UAV at the location of the observer is determined by the ratio between the intensity of acoustic radiation perceived by the observer from the UAV and the intensity of sound corresponding to the natural acoustic background and depends on the degree of manifestation of acoustic effects accompanying the propagation of sound in a turbulent atmosphere - the refraction of sound waves. Absorption and dissipation of acoustic energy. The calculation and comparison of the UAV detection range was carried out taking into account the existing natural maskers.The results of experimental studies are presented that allow assessing the degree of acoustic signature of the UAV. A set of measures aimed at reducing the intensity of the acoustic signature of the UAV in various regions of the radiation spectrum has been determined.

Acoustic Characteristics of a Gas Turbine Exhaust Model

1974 ◽  
Vol 96 (3) ◽  
pp. 181-184 ◽  
Author(s):  
J. R. Cummins
Keyword(s):  
Gas Turbine ◽  
Acoustic Radiation ◽  
Flow Path ◽  
Scale Model ◽  
Temperature Ratio ◽  
Acoustic Characteristics ◽  
Gas Turbine Exhaust ◽  
Acoustical Data ◽  
Turbine Exhaust

To investigate the sources of acoustic radiation from a gas turbine exhaust, a one-seventh scale model has been constructed. The model geometrically scales the flow path downstream of the rotating parts including support struts and turning vanes. A discussion and comparison of different kinds of aerodynamic and acoustic scaling techniques are given. The effect of the temperature ratio between model and prototype is found to be an important parameter in comparing acoustical data.

USE OF GROOVED SURFACES TO IMPROVE HYDRODYNAMIC, CAVITATION AND ACOUSTIC CHARACTERISTICS OF WINGS AND ELEMENTS OF VANE PROPULSION SYSTEMS (REVIEW)

2021 ◽  
Vol 2 ◽  
pp. 3-17
Author(s):  
A.L. SUKHORUKOV
Keyword(s):  
Computational Models ◽  
Acoustic Radiation ◽  
Hydrodynamic Cavitation ◽  
Propulsion Systems ◽  
Acoustic Characteristics ◽  
Flow Parameters ◽  
Turbulent Transition ◽  
Grooved Surface ◽  
Propeller Blades ◽  
Laminar Turbulent Transition

The paper reviews the use of grooved surfaces and sawtooth (chevron) edges to control the flow parameters of the wings, propeller blades and elements of vane propulsion systems operating in both gaseous and liquid media. Particular attention is paid to the physical mechanisms of improving the hydrodynamic, cavitation and acoustic characteristics under the influence of a grooved surface. These mechanisms are associated with a change in the flow structure in the region of the laminar-turbulent transition, the peculiarities of the occurrence of cavitation and acoustic radiation in the region of the outgoing edges. The results of the verification of computational models describing the behavior of the flow taking into account the laminar-turbulent transition, the use of which is necessary for studying flows near a grooved surface, are presented.

scholarly journals Determination of inductances for pulsating current traction motor

2021 ◽  
Vol 2 (1(58)) ◽  
pp. 40-43
Author(s):  
Sergey Goolak ◽  
Viktor Tkachenko ◽  
Svitlana Sapronova ◽  
Oleksandr Spivak ◽  
Ievgen Riabov ◽  
...  
Keyword(s):  
Electric Motor ◽  
Reactive Power ◽  
Country Of Origin ◽  
Experimental Studies ◽  
Active Power ◽  
Nonlinear Dependence ◽  
Power Losses ◽  
Electrical Parameters ◽  
Traction Motor ◽  
Pulsating Current

The object of research is a pulsating current traction motor. To improve the accuracy of its mathematical model, it is necessary to use the values of the parameters that are determined in experimental studies of the electric motor. In particular, it is important to use in the model of the electric motor inductance obtained experimentally. A method is proposed for calculating the inductance of the armature winding, main poles, additional poles and compensation winding and the total inductance of the traction motor armature circuit. The calculations are based on the results of the indirect inductance measurement method, in which the electrical values of various modes of power supply of the electric motor windings are directly measured, and the inductances are determined by auxiliary calculations. The inductances of the traction motor armature circuit have a non-linear dependence on the current flowing through them. The main difference of the study is that the measurements of the electrical parameters required for calculating the inductance are carried out over the entire range of operating currents of the windings. The essence of the proposed technique is to measure the active power in the armature winding, the winding of the main and additional poles, and the compensation winding, as well as in the armature circle as a whole when they are supplied with alternating current. According to the obtained values of active power losses and phase displacement, the corresponding reactive power losses are determined, with the help of which the inductances of the motor windings are calculated. Approbation of the methodology for calculating the conduction inductance for an electric motor of a pulsating current NB-418K6 (country of origin Russia), is used on electric locomotives of the VL80T and VL80k series (country of origin Russia). A scheme for measuring electrical parameters necessary for calculating inductance is proposed. The graphical dependences of the inductance on the armature current, built on the basis of calculations, confirmed the hypothesis about the nonlinear dependence of these inductances on the armature current. For further application of the results obtained in the simulation of the operation of the traction electric motor NB-418K6, a polynomial approximation of the total inductance of the armature circuit was performed.

scholarly journals EFFICIENT ACOUSTIC COMPOSITE PANELS BASED ON GRAPHITE

2021 ◽  
Vol 6 (4) ◽  
pp. 82-90
Author(s):  
E. Fanina
Keyword(s):  
Experimental Studies ◽  
Three Dimensional ◽  
Sound Field ◽  
Fire Retardant ◽  
Pyramidal Cells ◽  
Sound Insulation ◽  
Composite Panels ◽  
Thin Membrane ◽  
Reverberation Time ◽  
Acoustic Characteristics

A set of experimental studies is carried out to determine the acoustic characteristics of three-dimensional panels of fixed thickness made of carbon-based composite material installed in the opening between the reverberation chambers. Sound insulation indices are determined when they are excited by a diffuse sound field in wide frequency ranges. The reverberation time in model chambers with different partition configurations is calculated. The optimal configuration of the partition with pyramidal cells to reduce the reverberation time in the rooms is determined. The use of graphite in the form of thin membrane applied to various surfaces can significantly reduce the sound pressure levels in the room and increase the sound insulation indices of air noise. In addition to thin membrane, graphite can be used as an additive in composite materials for sound insulation purposes. It is shown that the characteristics of such panels are quite universal. The measured acoustic characteristics of composite panels are compared with similar characteristics of traditional materials. It is determined that the composition belongs to the I group of fire-retardant efficiency and can be recommended for use as a fire-retardant material. The developed acoustic material is an effective absorbing agent that solves problems in architectural acoustics, echo cancellation in construction and architecture. Similar to metamaterials, natural and artificial graphites allow to solve these problems with small volumes and masses using simple and inexpensive technologies.

scholarly journals THE STUDY OF ACOUSTIC CHARACTERISTICS OF THE PERFORATED AND HOMOGENOUS PLATES WITH SIMILAR GEOMETRICAL DIMENSIONS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 79-82
Author(s):  
Valery Kirpichnikov ◽  
Lyudmila Drozdova ◽  
Alexei Koscheev ◽  
Ernst Myshinsky
Keyword(s):  
Resonant Frequency ◽  
Acoustic Radiation ◽  
Perforated Plate ◽  
Acoustic Characteristics ◽  
Resonant Frequencies ◽  
Perforated Plates ◽  
Resonance Frequencies ◽  
Flexural Vibrations ◽  
Geometrical Dimensions

The resonance frequencies of the flexural vibrations, input vibration excitability and acoustic radiation of the homogeneous and perforated plates were investigated. It is established that the average reduction range of the lower resonant frequency of flexural vibrations of the tested plates with the holes virtually coincides with the predictive estimate. The levels of the input vibration excitability of the perforated plate at the lower resonant frequencies exceeded the levels at the corresponding frequencies of the homogeneous plates greater than the calculated value. The levels of resonance acoustic radiation of the perforated plate were significantly less than of the homogeneous one.

Diagnostics of Advanced Power Intensive Power Sources Based on the Acoustic Spectroscopy Method

2021 ◽  
pp. 121-127
Author(s):  
E.M. Petrenko ◽  
V.A. Semenova
Keyword(s):  
High Reliability ◽  
Methodological Approach ◽  
Spectral Characteristics ◽  
Experimental Studies ◽  
Mechanical Action ◽  
Mean Value ◽  
Spectroscopy Method ◽  
Power Sources ◽  
Acoustic Spectroscopy ◽  
Noise Diagnostics

Objective of this article is to develop a method for lithium chemical current sources diagnostics, which would ensure high reliability in assessing their technical state (primarily, the discharge degree) close to potentially achievable introduction of the acoustic spectroscopy method. Today, microcalorimetric studies and methods of impedance and noise spectroscopy make it possible to predict the lithium chemical current sources service life. However, implementation of the microcalorimetric studies result requires a lot of time accompanied by using stationary and large-size equipment, which is practically impossible in the autonomous conditions. Application of the impedance spectroscopy method provides satisfactory results only with high degrees of discharge. In the range of 0--30 %, it is very difficult to determine the discharge degree, since noticeable alteration in the correlate within its deviation from the mean value is missing. In this regard, it is proposed in order to provide diagnostics of the lithium chemical current sources in the region of initial degrees of discharge to introduce the noise diagnostics method. In order to increase reliability of the diagnostic estimates, it is advisable to use acoustic spectroscopy as a physically independent method in diagnosing the state of lithium chemical current sources. Results of the preliminary measurements analysis confirm the prospects of using the acoustic spectroscopy method in assessing the current state of primary lithium chemical current sources. Experimental studies of the lithium chemical current sources response to acoustic (mechanical) action made it possible to determine a set of parameters characterizing the proposed methodological approach. This provided a possibility to search for correlation dependences of the lithium chemical current sources spectral characteristics on the degree of their discharge. This makes it possible to use the method of acoustic spectroscopy in prompt and reliable diagnostics of the primary current sources in the region of low discharge degrees

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