IMPROVEMENT OF NOISE SILENCER ARMORED VEHICLE KRAZ “BASTION” APPLICATION OF THE GAS SCREEN

2019 ◽  
pp. 11-16
Author(s):  
Volodymyr Fedorov ◽  
Vasyl Yanovsky ◽  
E. M. Mazur
Keyword(s):  
Internal Combustion Engines ◽  
Gas Flow ◽  
Visual Masking ◽  
Internal Combustion ◽  
External Noise ◽  
Angle Of Incidence ◽  
Combustion Engines ◽  
Sound Waves ◽  
Armored Vehicle ◽  
Gas Screen

Ukraine has been fighting for five years in the east with the Northern Neighbor and for much more time striving for NATO membership. Under these circumstances, the ongoing improvement of military technology. Creation of modern armored cars is topical. One of the important requirements for them – high masking properties. In addition to visual masking there is also sound. In this case, it means reducing the external noise of armored cars. The source of noise and ways to reduce them is a lot. One of the most powerful sources of armored car noise is the noise of the release system, the noise of the bedroom. This type of noise is reduced by means of silencers. The latter are diverse in terms of designs, principles of operation, frequency characteristics and acoustic efficiency. The increase of the acoustic efficiency of silencer noise of the car internal combustion engines was proposed using a gas screen, which until now was used only in aircraft engineering. The essence of the proposal is to create around the outlet branch muffler gas flow, the speed of which is higher than the speed of the outflow of bedrooms. Due to this, the sound waves contained in the sleeping bags will not be able to go into the environment, passing through an additional gas stream, and they will fall onto a special sound absorbing plate. Correspondingly, the sponges will be reflected from this plate and will go to the environment. In this work, for example, the KrAZ Armored Vehicle “Bastion” shows the projected increase in the acoustic efficiency of the existing silencer through the use of a gas screen for the speed of the armored vehicle 45, 50, 75 and 85 km / h. At the same time, the dependence of the difference in speeds of artificially created gas flow and the beds in the muffler of noise from the angle of incidence of sound waves in the flow of bedrooms was calculated. Also shown is the dependence of the angle of incidence of sound waves on the frequency of the latter. Improvement of the existing muffler noise of the internal combustion engines through the use of a gas screen is projected to reduce the external noise of the KrAZ “Bastion” car at 4-6 dB in the range of 45-85 km / h. Keywords: armored vehicle, internal combustion engine, silencer, exhaust gases, noise, noise source, acoustic efficiency, gas screen.

scholarly journals IMPROVEMENT OF MUFFLER S DESIGN FOR REDUCTION OF THE LEVEL OF SOUND PRESSURE ON SMALL TRACTORS OPERATORS

2021 ◽  
Author(s):  
M. I. Podolsky ◽  
◽  
I. Y. Lilevman ◽  
O. Y. Lilevman ◽  
O. Y. Kedrovsky ◽  
...  
Keyword(s):  
Internal Combustion Engines ◽  
Gas Flow ◽  
Sound Pressure ◽  
Internal Combustion ◽  
Pressure Level ◽  
Combustion Engines ◽  
Sound Waves ◽  
Exhaust Gases ◽  
Noise Absorption ◽  
Made In

Noise background, as an important factor in the working conditions of agricultural operators, has a direct impact on human health and productivity. This topic is especially relevant for small tractors, which in most cases are not equipped with cabs. One of the main means of reducing the sound pressure on the operator are the mufflers of exhaust gases, which mainly have a labyrinth-absorbing type of action. The paper proposes a fundamental approach to the design of the muffler by the criterion of reflection and scattering of sound waves with the verification of efficiency by computer simulation. The purpose of research: - to improve the working conditions of operators of small tractors that are not equipped with cabs, by reducing the sound pressure level from internal combustion engines; - to improve the noise-absorbing properties of mufflers of exhaust gases of engines with observance of requirements to manufacturability of process of their manufacturing; - to develop a structural scheme of the exhaust gases muffler based on the results of preliminary modeling and analysis of the trajectory of the gas flow in the cavity of its working part. Methods. Determination of the sound pressure level of the engine of a small tractor by mathematical (computer) modeling of the behavior of the exhaust gas flow in the muffler cavity in different frequency ranges. Results. The article analyzes the main sources of noise during the operation of agricultural machinery with internal combustion engines (ICE). On the basis of literature sources and methods, their separate degree of influence on the complex picture of noise pollution of the working space of the operator of a small tractor is established. A comparative analysis of the efficiency of mufflers, created on the generally accepted principles and approaches to the design of such devices. According to the results of previous tests, shortcomings and limitations in the application of design concepts were identified, an additional analysis of external causes and factors was made, and adjustments were made to the method of creating muffler designs. An alternative design approach to the creation of internal combustion engine mufflers of small tractors is proposed and computer modeling of the processes of sound pressure distribution and sound waves in their cavity is performed. Conclusions. 1. A layout diagram of the design of the exhaust muffler, containing a resonator chamber and a shell module, which is made in the form of a three-stage ribbed diffuser of oscillations of the exhaust flow pulses with an additional surface layer of the vibration absorber. The parameters of the exhaust flow of exhaust gases of a typical diesel engine of a small tractor with a capacity of 24 hp are calculated. (pressure - 11652 Pa, acceleration – 90-105 m / s2, frequency - 1950-3300 Hz), which performed computer simulations of the process of gas movement in the muffler cavity of the proposed layout. Optimal design parameters were selected to ensure the maximum possible noise absorption with a body diameter of 150 mm and a length of 600 mm. The calculated sound pressure when working at the crankshaft speed (1700-2000) rpm does not exceed 72 dB. At the same time, the design of the muffler is made in compliance with the requirements for economic feasibility, manufacturability and in accordance with the capabilities of industrial production. A further direction of research is the manufacture of an experimental sample of the muffler and testing for the efficiency of its noise absorption in the conditions of operation of small tractors.

scholarly journals Combined noise shield with integrated solar panels

2021 ◽  
pp. 47-53
Author(s):  
Elena Lezhneva ◽  
Katerina Vakulenko
Keyword(s):  
Urban Environment ◽  
Internal Combustion Engines ◽  
Residential Buildings ◽  
Chemical Compounds ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Sound Waves ◽  
Solar Panels ◽  
Engineering Structures ◽  
Solar Batteries

The article is devoted to the assessment of the noise load of road transport on the environment of large cities. Goal. The goal is to develop engineering structures to neutralize harmful substances from internal combustion engines, display and absorb sound waves, ensure road safety and improve energy efficiency. Methodology. The experience of European countries on the use of noise protection screens with integrated solar batteries is presented. The types and design features of solar panels are presented. Results. A model of a combined noise protection barrier with integrated solar batteries is proposed. This screen can be used to protect the urban environment from noise, sound waves and chemical compounds of internal combustion engines. Originality. The combined noise barrier with integrated solar panels is an engineering structure consisting of a foundation, sound-absorbing, sound-reflecting modules and solar cells, which differs in that it has a Y-shaped profile equipped with metal perforated modules filled with sound-absorbing material (polymers of organic origin , composite materials, mineral fibers, etc.) and sound-reflecting transparent or translucent modules, installed on a foundation made of photocatalytic concrete, and the energy obtained from the solar panels is transferred to street lights, which are installed on the foundation of the screen. Practical value. The invention can be used to protect against noise, sound waves and chemical compounds of exhaust gases of internal combustion engines of urban environment, residential buildings and pedestrian areas.

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