Experimental Characterization of Noise Sources for Duct Acoustics

1989 ◽  
Vol 111 (1) ◽  
pp. 108-114 ◽  
Author(s):  
A. G. Doige ◽  
H. S. Alves
Keyword(s):  
Source Parameters ◽  
Control Valve ◽  
Industrial Applications ◽  
Centrifugal Fan ◽  
Acoustic System ◽  
Noise Sources ◽  
Load Impedance ◽  
Source Impedance ◽  
Electrical Analogy ◽  
Piping Systems

Many industrial applications involving the acoustics of ducting or piping systems require an improved description of noise sources, so that a better prediction and evaluation of system performance can be achieved. Some examples are (a) the computer simulation of intake and exhaust muffler performance, (b) the control of pressure pulsation in fluid piping systems due to control valve flow noise or reciprocating compressors, and (c) predicting pressure fluctuations in heating and air-conditioning system ductwork due to various types of fans or blowers. This paper describes two applications of a well-known linear electrical analogy for obtaining experimentally the internal acoustical source impedance and the strength of the source, both parameters which are independent of the acoustic system load impedance. Two methods are compared, one which utilizes direct measurement of source impedance with the source inactive, and a two-load method from which the source impedance is calculated from measured pressures, with the source in operation. Various applications are presented using a speaker, compressor, engine, and centrifugal fan as noise sources connected to different load impedances. Comparisons are made to highlight the relative merits of these two approaches and to demonstrate the degree of accuracy that can be obtained in predicting noise levels in any arbitrary linear acoustic system, using the measured source parameters. The methods are simple in concept and in application, and while they do not often describe the physical nature of noise sources, they do offer a way to bypass the much more difficult problem of modelling the source theoretically.

Experimental Assessment of the Dynamic Behavior of Polyolefin Thermoplastic Hot Melt Adhesive

2018 ◽  
Author(s):  
Raffaele Ciardiello ◽  
Andrea Tridello ◽  
Luca Goglio ◽  
Giovanni Belingardi
Keyword(s):  
Failure Modes ◽  
Industrial Applications ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Dynamic Tests ◽  
Cohesive Failure ◽  
Static Tests ◽  
Piping Systems ◽  
The Many ◽  
Hot Melt

In the last decades, the use of adhesives has rapidly increased in many industrial fields. Adhesive joints are often preferred to traditional fasteners due to the many advantages that they offer. For instance, adhesive joints show a better stress distribution compared to the traditional fasteners and high mechanical properties under different loading conditions. Furthermore, they are usually preferred for joining components made of different materials. A wide variety of adhesives is currently available: thermoset adhesives are generally employed for structural joints but recently there has been a significant increment in the use of thermoplastic adhesives, in particular of the hot-melt adhesives (HMAs). HMAs permit to bond a large number of materials, including metal and plastics (e.g., polypropylene, PP), which can be hardly bonded with traditional adhesives. Furthermore, HMAs are characterized by a short open time and, therefore, permit for a quick and easy assembly process since they can be easily spread on the adherend surfaces by means of a hot-melt gun and they offer the opportunity of an ease disassembling process for repair and recycle. For all these reasons, HMAs are employed in many industrial applications and are currently used also for bonding polypropylene and polyolefin piping systems. In the present paper, the dynamic response of single lap joints (SLJ) obtained by bonding together with a polyolefin HMA two polypropylene substrates was experimentally assessed. Quasi-static tests and dynamic tests were carried out to investigate the strain rate effect: dynamic tests were carried out with a modified instrumented impact pendulum. Relevant changes in the joint performance have been put in evidence. Failure modes were finally analysed and compared. A change in the failure mode is experimentally found: in quasi-static tests SLJ failed due to a cohesive failure of the adhesive, whereas in dynamic tests the SLJ failed due to an interfacial failure, with a low energy absorption.

scholarly journals Pneumatic Actuator Controlled by Proportional Valve. Experimental results

2021 ◽  
Vol 286 ◽  
pp. 04010
Author(s):  
Valentin Nicolae Cococi ◽  
Constantin Călinoiu ◽  
Carmen-Anca Safta
Keyword(s):  
Control Valve ◽  
Industrial Applications ◽  
Experimental Results ◽  
Pneumatic Actuator ◽  
Proportional Valve ◽  
Controlled Systems ◽  
Automation Systems ◽  
Simulation Results ◽  
The Mathematical Model ◽  
Fire Ignition

In nowadays the pneumatic controlled systems are widely used in industrial applications where valves must be operated, where there is a fire ignition risk, or in different automation systems where a positioning action is desired. The paper presents the experimental results of a pneumatic actuator controlled by a proportional control valve. The goal of the paper is to compare the experimental results with the numerical simulation results and to improve the mathematical model associated with the experiment.

Pressure Fluctuations Around Steam Control Valve: Steam Experiments and CFD Calculations

2007 ◽  
Author(s):  
Ryo Morita ◽  
Fumio Inada
Keyword(s):  
Power Plant ◽  
Pressure Fluctuations ◽  
3D Structure ◽  
Flow Characteristics ◽  
Control Valve ◽  
Working Fluid ◽  
Complex Flow ◽  
Piping Systems ◽  
The Difference ◽  
Complex Flow Structure

In some cases, a steam control valve (figure 1) in a power plant causes large vibrations in piping systems that can be attributed to pressure fluctuations generated in the valve under the partial-valve-opening (middle-opening) condition. For the maintenance and the management of the plant, the valve system needs to be improved to prevent the onset of hydrodynamic instabilities. However, in the case of the steam control valve, it is difficult to understand the flow characteristics in detail experimentally because the flow around the valve has a complex 3D structure and becomes supersonic (M>1). For these reasons, the details of the flow around the valve are not fully understood before, and CFD simulations are required to understand the underlying complex flow structure associated with the valve. In our previous researches, a mechanism of the pressure fluctuations in the middle opening condition, named “rotating pressure fluctuations”, were clarified and a suppression shape were developed by experiments and CFD calculations. However, as we used air as a working fluid in our previous researches instead of steam that is used in the power plant, we couldn’t consider effects of condensation and difference of change of the state quantities between air and steam. In this report, we have conducted steam experiments and CFD calculations by original code to clarify the effects of the difference of the fluids. As a result, in the middle opening condition, we have observed spike-type pressure fluctuations and their rotation in the experiment, and valve-attached flow and local high-pressure region in the CFD result. These results indicate the pressure fluctuations observed in steam experiments and CFDs are the same as rotating pressure fluctuations observced in air researches.

Experimental determination of the tonal noise sources in a centrifugal fan

2006 ◽  
Vol 295 (3-5) ◽  
pp. 781-796 ◽  
Author(s):  
Sandra Velarde-Suárez ◽  
Rafael Ballesteros-Tajadura ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Experimental Determination ◽  
Centrifugal Fan ◽  
Tonal Noise ◽  
Noise Sources

Guide for Selecting Pressure Control Valves With Actuators Used in Pipeline Applications

2010 ◽  
Author(s):  
Jack Broyles ◽  
Roger Shirt
Keyword(s):  
Selection Criteria ◽  
Large Diameter ◽  
Control Valve ◽  
Pressure Control ◽  
Industrial Applications ◽  
Performance Criteria ◽  
Effective Control ◽  
Critical Threshold ◽  
Control Valves ◽  
Selection Strategies

This paper will discuss guidelines for the selection of pressure control valves (PCV) with electro-hydraulic actuators for use in liquid petroleum pipelines. The performance criteria for PCVs functioning in pipeline pressure control applications are distinct from those used in other industrial applications. Also, PCVs required for large diameter petroleum pipeline represent a relatively small number of total control valve applications. For these reasons, general practitioners of control valve selections, typically engineers at EPCs, commonly apply selection strategies that are effective in other industrial applications, but tend to be less so in pipeline applications. This paper will discuss control valve selection criteria including Critical Threshold Capacity, Effective Control Region and Valve Gain Band. Actuator selection criteria discussed in this paper includes Torque Requirements, Speed of Response, and Positioning Resolution.

Experimental Characterization of the Influence of Auxiliary Devices on the Noise Generated by Industrial Centrifugal Fan and Correlation to the Geometrical and Fluid Dynamic Parameters

2011 ◽  
Author(s):  
M. Cadorin ◽  
M. Pinelli ◽  
E. Podeschi ◽  
F. Pompoli ◽  
A. Zanardi
Keyword(s):  
Fluid Dynamic ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Dynamic Parameters ◽  
Experimental Characterization ◽  
Noise Sources ◽  
Additional Noise ◽  
Centrifugal Fans

In recent years, the aerodynamic noise generated by centrifugal fans is receiving increasing attention because of strict environmental noise level restrictions and customer demands. The noise generated by fans is due to aerodynamic sources and to other several sources, such as, for instance, by the fan drive, by bearings and gearing, and, when present, by the inverter. Additional noise sources can be also due to structural resonance effects induced by periodic forces associated with the blade passing frequency or vortex shedding. Usually, these additional noise sources are dominated by aerodynamic noise generated by the fan, in particular when the intake and outlet of the fan are free. On the other side, if fan intake and outlet are ducted, the additional sources can relevantly contribute to overall sound generation. In this paper, an experimental characterization of the noise generated by industrial centrifugal fans when both inlet and outlet are ducted is presented. To do this, an experimental facility has been design and set up, and the sound power measured by means of the procedures outlined in the ISO 3746 international standard. A number of different type of centrifugal fan (straight-, forward- and backward blade) in different working conditions were tested, resulting in 133 different runs. These amount of data were then processed and a general formula for fan noise estimation obtained as a function of the geometrical and fluid dynamic parameters is derived. Moreover, specific coefficients with respect to blade geometry for the determination of the A-weighted frequency spectrum are presented. Finally, auxiliary devices or other features, such as inverter, thickness of the casing, acoustic insulation, electric motor shaft, are analyzed and some general rules to estimate their influence on sound power level quantified.

Impact of Blending Ratio and Thermal Treatment on the Mechanical Behaviour of Polyethylene/Polypropylene Blends

2008 ◽  
Author(s):  
Abdel-Hamid I. Mourad
Keyword(s):  
Thermal Treatment ◽  
Mechanical Behaviour ◽  
Industrial Applications ◽  
Pressure Vessels ◽  
Weight Percentage ◽  
Performance Requirements ◽  
Wide Range ◽  
Piping Systems ◽  
And Performance ◽  
Pp Blends

In the recent years, blending of different polymers is receiving increasing attention from researchers for various reasons including the possibility of creating a material or product for new and more industrial applications to meet specific processing and performance requirements that cannot be satisfied by a single component. Polyethylene (PE) and polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications such as piping systems in pressure vessels and pipelines. The main objective of this work is to study the effect of the thermal treatment/aging and PE/PP blending ratio (composition range) on the mechanical behaviour (tensile and hardness) of PE, PP and PE/PP blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 weight percentage were prepared via injection molding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however thermal aging hasn’t affected the hardness showing a good correlation with the tensile properties.

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