Vol 1, No 1 (2014)
- Year: 2014
- Published: 22.06.2014
- Articles: 10
- URL: https://dynvibro.ru/dynvibro/issue/view/104
Full Issue
Articles
High frequency noise suppression of the automobile exhaust system
Abstract
The paper presents the decision for the question of the excessive catalytic collector high frequency noise in the automobile engine exhaust system. The high level noise has been observed under the idle state engine condition. In order to understand the causes of the high catalytic collector noise emission the research of its vibroacoustic internals has been performed. An experimental stand for the acoustic and vibration response on broadband dynamic excitation tests has been created. The power of the acoustic noise, emitted by the catalytic collector and vibration distribution of its surface have been defined. It was found that the catalytic collector surface has the low acoustic impedance in the high frequency range. The surface vibration damper design has been developed. A special material, so called metal rubber, has been used to damp the vibration. The main advantage of this material is the temperature tolerance, quite useful for the engine exhaust system unit. The use of the damper has allowed to reduce the structure-born noise of the catalytic collector.
Key words: catalytic collector; structure-born noise; automobile; acoustic power; acoustic impedance; metal rubber
6-11
Experimental and numerical flow noise modeling of flow channelsin hydraulic components
Abstract
Acoustic parameters of HN emission by perforated sleeve-dissector in outlet flow are investigated in details.
Experimental and numerical research of influence of flow channel configuration of perforation holes on flow noise density is done. Acoustic characteristics of different forms of channelslike diffuser, confusor and cylinder are studied. It is shown, that the most rational form of channel is cylinder, which have the minimal flow coefficient.
12-16
Effect of connected system on gas pressure controllers’ stability
Abstract
In the paper the influence of dynamic performances of pipe systems connected to the control valve on system stability is studied through mathematical modeling and experimental work. Dynamic interaction between typical pressure control valves and up- and downstream pipelines is investigated. Stability criteria are derived in the form of requirements for input impedances of pipes connected. The best and the worse boundary conditions are deduced for each type of controllers. The best boundary conditions ensure stability even in a case of zero damping of the poppet. The worse boundary conditions determine maximum damping required to keep stability in any other system. To meet the requirements received, effective measures are suggested for each type of the control valve on the basis of special corrective devices (compensators) of the acoustic filter type. A scheme, parameters and location of the devices are determined by the type and parameters of the valve.
17-23
Dynamics of tank propellant head control system
Abstract
In the paper the impact of the axial acceleration factor on dynamic characteristics of the pressure controls of the gas pillow of liquid-propellant rocket’s fuel tank is considered. Frequency responses are defined. Possible applications of the developed model are proposed.
Key words: pilot operated gas pressure controller, axial acceleration factor, control system dynamics, gain and phase frequency responses
24-27
Vibroacoustic loads reduction in pipe systems of gas distribution stations
Abstract
In the present paper the model of the pressure reducing valve with silencer is created in Matlab. The model is used for determining, how seated valve opens, outlet pressure and acoustic power level with downstream silencer fitted at outlet of it. The flow areas optimization of multi-stage silencer is completed. The impact of different design parameters on acoustic characteristics of the system is investigated by modeling and experiments. As a result of the paper the design of silencer, which reduces noise to 30 dBA, is created.
Key words: Pipeline system; gas distribution station; pressure regulator; noise; silencer
28-33
Noise and vibration protection of roof boiler equipped house
Abstract
The roof mounted boiler house is one of the perspective kinds of autonomous heat supply. Boiler houses are located on the building roofs or on a special substructure, mounted over the roof. New apartment blocks are usually equipped with the roof mounted boiler houses thanks to the high cost effectiveness of this solution. However, vibration isolation is often neglected when boilers are installed directly to the substructure. As a result, residents of the upper floor apartments suffer from the constant noise exposure. Experimental studies of various boiler equipment operation modes were conducted in order to determine the main sources of noise and their frequency spectrum. It was shown that the main source of the noise increase in residential areas was the boiler combustion process. The noise has a structural character. The vibration protection system, based on the rope isolators (VMT), has been developed in order to reduce the noise levels in residential areas. We have carried out necessary calculations, taking into account the weight of the boiler, the water in it and all associated elements. Also, the isolator samples were a statically tested. The vibration protection system implementation provides the achievement of sanitary noise norms in residential areas.
Key words: Noise; isolator; vibration protection system; vibration; roof boiler
34-42
On linear and nonlinear trajectory tracking control for nonholonomic integrator
Abstract
This paper presents two different kinds of trajectory tracking control strategies for the nonholonomic integrator known in literature as Brockett system. The first strategy presents a time-varying linear feedback control law and the second strategy is based on State Dependent Ricatti Equation (SDRE) method. Numerical simulation results indicated that both methods can be successfully used for control of the nonholomic integrator.
Keywords: Brockett integrator, Hamilton – Jacobi – Bellman equation, SDRE method.
43-48
Experimental investigation of air supply in combined pump unit
Abstract
It’s well known erosion caused by cavitation leads to increased wear of details. Investigation of erosion place of origin is intensive and complex problem. Therefore using of simple methods of cavitation diagnosis is very actual. One of these methods is vibroacoustical diagnosis which take into account not only noise occurred due to working process but also pressure pulsation of working fluid and vibration of system components. Noise measurement may locate their source thereby determine the most acoustically loaded details of the investigated unit.
This paper describes some questions of cavitation influence on external acoustic field in combined pump unit. We proposed the method for cavitation diagnosis in combined pump unit. This method is based on measurement of external acoustic field. This method showed high accuracy and ease of use. The experimental studies have established a connection between pulsation characteristics of the pump unit and an external acoustic field.
Key words: pump unit, combined air, cavitation, erosion acoustic visualization
49-54
Simulations of pipe line system with pres-sure pulsation damper
Abstract
The method of pipeline system dynamics with pressure pulsation damper are developed. The method is based on the solving differential equation system of interaction between solid and oscillating fluid in the pipeline and pressure pulsation damper. Solution was done for steady-state oscillations.It is actual for aircraft pipelines, pipes of power plants, mobile machines and pipes of stationary processing machines.
55-60
Сharacteristics calculation procedure for the nonlinear hydraulic chains with pulsating working media
Abstract
The article describes a technique developed by the authors to calculate the static and dynamic errors of the hydraulic chains caused by nonlinear averaging pressure pulsations. Given an example of calculating the deviation of the engine automatic control chain characteristics due to the influence of pressure fluctuations at the output of the fuel pump gear.
Keywords: Nonlinear hydraulic chain, pressure fluctuations, error, calculation method, engine, regulator, startup characteristic, deflection of the characteristics
61-68