Modeling and designing for acoustic and pressure drop of perforated tube in the path of unsteady compressible flow

Abstract: 
Perforated elements are widely used in silencers. Two important parameters in these geometries are their acoustic and hydrodynamic performance. The main purpose of silencers is to reduce the sound, but the pressure drop in them is inevitable. This research presents modeling of a perforated path for unsteady compressible flow to predict acoustic and hydrodynamic behaviors.
publication venue:
Khwarizmi International Conference on Science and Technology, Iran, 2024

Experimental and numerical investigation of transmission loss in a zero-flow silencer

Abstract: 
To evaluate the acoustic performance of the muffler at zero flow, different methods of determining transmission loss (TL) were studied. Numerical and experimental approaches were used to calculate TL. The numerical method employed was the Herschel-Quincke tube method (case 1) COMSOL simulation (case 2) and ANSYS simulation (case 3). The experimental approach utilized the transfer matrix method with the aid of software developed by the B&K software (case 4) and the sound card with MATLAB software (case 5) was used to calculate TL. Furthermore, the mesh independence of numerical methods and the uncertainty of the experimental method were examined. Results were evaluated between 20 and 1900 Hz, which is an appropriate frequency range for TL calculations According to the results, the equivalent TL for cases 1 to 5 is approximately 5.81 dB, 5.35 dB, 5.21 dB, 4.08 dB, and 3.77 dB, respectively. Based on the findings, it can be concluded that the equivalent TL of ANSYS and COMSOL simulations was similar, and COMSOL simulation results in an 8% lower equivalent TL than the case 1 approach. Similarly, the equivalent TL of experimental calculation methods indicates that the case 5 approach has a 7.5% lower equivalent TL than the case 4 approach.
publication venue:
Amirkabir Journal of Mechanical Engineering (Amirkabir J Mech Eng), 2024

Evaluation commercialization challenges and resolutions in SMEs using ML-FCM (case study: Sanat Prozheh Toos)

Abstract: 
Commercialization of innovative products in small and medium-sized enterprises (SMEs) faces many challenges. In this study, the factors related to the existing challenges and resolutions are identified with the help of the multi-layer fuzzy cognitive mapping (ML-FCM) method. The most effective criterion is introduced by examining the centrality. Also, the challenges and the existing resolutions to overcome these challenges are specified, and the most effective ones are determined. The present study addresses the practical experience of Sanat Prozheh Toos Company, which operates in the design and production of mechanical noise pollution control equipment (e.g., Silencers). The data is collected based on the organization's documents and experts' opinions. Research findings confirm that among the challenges of commercialization of innovative products associated with the case study, management challenge has the highest degree of effectiveness and centrality; moreover, among the ways of overcoming these challenges, organizational integration has the highest degree of centrality. Thus, the findings provide policy and management suggestions for SMEs policymakers and managers in commercializing advanced technologies.
publication venue:
Journal of Systems Thinking in Practice, 2023

Production method and analysis of the acoustic and mechanical properties of soft polyurethane foam reinforced by nano-alumina particles

Abstract: 
Reduction of unwanted noises is an important issue in the current societies regarding their potential negative impact on the mental and physical health of the peoples. Researchers are trying to find a new method to reduce the damage of this unwanted sound. Accordingly, the use of sound absorbing materials with appropriate acoustic properties has increased in the recent years. In this article, the production of polyurethane foam explained first and sound absorption coefficient of pure PUF has been measured. In order to improve the mechanical and acoustical properties of polyurethane foam, various quantities of Nano-Alumina powder is added to the structure of the foam. The effects of this additive material on the acoustic and mechanical properties of the foam are then measured. In this work, for the first time, the mechanical, physical and acoustical properties of the polyurethane foam improved by Nano-Alumina are studied. Finally, the change of the sound absorption coefficient of the produced composite material is analyzed based on the mechanical and physical experimental results. The sound absorption coefficient of this foam is then measured using two microphone method with Impedance tubes
publication venue:
Modares Mechanical Engineering, 2016

Analysis of unsteady compressible flow into the shock-tube filled with porous material

Abstract: 
The characteristics method and the two-step Lax-Wendroff numerical method are used to analyze the different cases of unsteady compressible flow into the shock-tube. Initially the schemes ability is evaluated by comparing the predicted results with experimental ones. Then, an oscillation in density is imposed on right-hand side of shock-tube and its effect on the whole domain is analyzed. Charging and discharging processes into/or from an opened end pipe are studied for different boundary conditions using method of characteristics. Two suddenly and gradually opening boundary conditions for inlet and outlet ends are applied and it is found that instantly end opening is a suitable assumption for any charging processes, but it is not suitable for discharging one. Finally, analysis of the unsteady compressible fluid flow into a shock-tube filled by lining material or porous media is investigated.
publication venue:
International journal of industrial engineering and production management, 2006

N-junction modeling in perforate silencers for internal combustion engines

Abstract: 
In this work, boundary conditions of the T-junctions in engine silencers are modeled by the Constant Pressure Model (CPM) and the Pressure Loss Model (PLM). Initially, the mean flow velocity through the ducts is assumed to be zero. Two Benson CPM and Corberan CPM approaches are employed in perforate silencers simulation. For the silencer with more than one perforated pipe, in which N-branch junctions are formed, it is possible to apply the Benson CPM approach. Finally, when the mean flow velocity through the ducts is non-zero, the shortcoming of the CPM model and the ability of the PLM model in describing the T-junctions are shown
publication venue:
SCIENTIA IRANICA, 2005

Modelling of exhaust system silencers in internal combustion engines

Abstract: 
Perforated elements are widely used in silencers. Two important parameters in these geometries are their acoustic and hydrodynamic performance. The main purpose of silencers is to reduce the sound, but the pressure drop in them is inevitable. This research presents modeling of a perforated path for unsteady compressible flow to predict acoustic and hydrodynamic behaviors.
publication venue:
Khwarizmi International Conference on Science and Technology, Iran, 2024

Modeling of n-branch junctions and upstream acoustical excitation in the silencers of internal combustion engines

Abstract: 
In this work, boundary conditions of T-junctions in engine silencers are modeled by constant pressure model (CPM) and pressure loss model (PLM). The mean flow velocity through the ducts is zero. Two Benson CPM and Corberan CPM approaches are employed in perforate silencers simulation. For the silencer with more than one perforated pipe which appears as Nbranch junctions, it is possible to apply the Benson CPM approach. The upstream excitation as a boundary condition is modeled by two single pure tone (harmonic) and white noise perturbations. It is shown that white noise perturbation bring enough accuracy. On the other hand-it spends much shorter time than single pure tone perturbation
publication venue:
JOURNAL OF SCHOOL OF ENGINEERING, 2005

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