scholarly journals Simulations and Experimental Investigations on the Acoustic Characterization of Centrifugal Pumps of Different Specific Speed

2019 ◽  
Vol 4 (3) ◽  
pp. 16
Author(s):  
Christian Lehr ◽  
Andreas Linkamp ◽  
Daniel Aurich ◽  
Andreas Brümmer
Keyword(s):  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Dipole Source ◽  
Experimental Investigations ◽  
Acoustic Excitation ◽  
Centrifugal Pumps ◽  
Transmission Parameters ◽  
Acoustic Characterization ◽  
Specific Speed

Subject of discussion are simulations and experimental investigations on the acoustic characterization of three single stage centrifugal pumps of different specific speed. In operation, these pump-types generate pressure pulsation at blade passing frequency, primarily due to rotor-volute-interaction. In order to determine the acoustic excitation it is necessary to know about the pumps’ acoustic transmission parameters. In this paper, a one-dimensional numerical model for transient time-domain simulation is presented, which takes into account the pump geometry as well as the volutes’ structural behaviour by means of the local effective speed of sound. Numerical results for the transmission characteristics of the three different pumps are shown in terms of scattering matrices and evaluated against parameters calculated from measurement results. The experimental analyses are carried out using dynamic pressure sensors in both the suction and the discharge pipe. Assuming solely plane wave propagation, the complex acoustic field on each side is evaluated independently. The so called “two source” method is then used to determine the transmission parameters of the pumps in standstill for a range of frequencies experimentally. Subsequently, the acoustic excitation at varying rotational speed is evaluated by means of measurements at the pumps in operation and presented as monopole and dipole source types for cavitation-free conditions.

Experimental Characterization of a Remoting System for Dynamic Pressure Sensors

2005 ◽  
Author(s):  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Gabriele Sonni
Keyword(s):  
Shock Tube ◽  
Combustion Chamber ◽  
Operating Temperature ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Measurement Point ◽  
Experimental Characterization ◽  
Temperature Capability ◽  
Lower Operating Temperature

Concerning measurements with dynamic pressure sensors, one of the most interesting aspects is the influence of a remoting system interposed between the sensor and the measurement point. This mounting system, once correctly characterized, allows one to use the same sensor for different measurement points, reducing the total number of sensors used. In addition, in all the applications involving high temperatures (e.g. combustion chamber), a remoting system allows the use of cheaper dynamic pressure sensors with lower operating temperature capability. A remoting system for dynamic pressure sensors made up by a remoting duct, between the sensor and the measurement point, followed by a damping duct has been characterized for different tube lengths. Tests were carried out with two kinds of sources: a diaphragm-less shock tube for the first set of tests and an acoustic speaker for the second. Results are here reported and commented.

Flow and Dipole Source Evaluation of a Generic SUV

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Jonas Ask ◽  
Lars Davidson
Keyword(s):  
Strouhal Number ◽  
Mesh Generation ◽  
Recirculation Zone ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Dipole Source ◽  
Generation Process ◽  
Source Terms ◽  
Side Window ◽  
High Level

Accurately predicting both average flow quantities and acoustic sources at the front window of today’s ground vehicles are still a considerable challenge to automotive companies worldwide. One of the most important aspects in terms of obtaining not only trustworthy results but also the most tedious one and therefore perhaps overlooked, is the control and outcome of the mesh generation process. Generating unstructured volume meshes suitable for large eddy simulations with high level representation of geometrical details is both a time consuming and an extremely computer demanding activity. This work investigates two different mesh generation processes with its main aim to evaluate their outcome with respect to the prediction of the two dominating dipole sources in a temporal form of the Curle’s equation. Only a handful of papers exists that report a high level representation of the vehicle geometry and the aim of predicting the fluctuating exterior noise sources. To the author’s knowledge no studies have been conducted in which both these source terms are evaluated quantitatively against measurements. The current paper investigates the degree to which the amplitude of these two source terms can be predicted by using the traditional law-of-the-wall and hex-dominant meshes with isotropic resolution boxes for a detailed ground vehicle geometry. For this purpose, the unstructured segregated commercial FLUENT finite volume method code is used. The flow field is treated as incompressible and the Smagorinsky–Lilly model is used to compute the subgrid stresses. Mean flow quantities are measured with a 14 hole probe for 14 rakes downstream of the side mirror. The dynamic pressure sensors are distributed at 16 different positions over the side window to capture the fluctuating pressure signals. All measurements in this work were conducted at Ford’s acoustic wind tunnel in Cologne. All three simulations accurately predict the velocity magnitude closest to the window and downstream of the mirror head recirculation zone. Some variations in the size and shape of this recirculation zone are found between the different meshes, most probably caused by differences in the detachment of the mirror head boundary layer. The Strouhal number of the shortest simulation was computed from the fundamental frequency of the drag force coefficient. The computed Strouhal number agrees well with the corresponding results from similar objects and gives an indication of an acceptable simulation time. The dynamic pressure sensors at 16 different locations at the vehicle side window were also used to capture the levels of the two dipole source terms. These results are compared with the three simulations. With the exception of three positions, at least one of the three simulations accurately captures the levels of both source terms up to about 1000 Hz. The three positions with less agreement as compared with measurements were found to be in regions sensitive to small changes in the local flow direction.

scholarly journals Development and Characterization of a Low-Cost Sensors System for an Acoustic Test Bench

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6663
Author(s):  
Ciro Moreno-Ramírez ◽  
Carmen Iniesta ◽  
Alejandro González ◽  
José Luis Olazagoitia
Keyword(s):  
Test Bench ◽  
Mechanical Design ◽  
Dynamic Pressure ◽  
Low Cost ◽  
Pressure Sensors ◽  
Acquisition System ◽  
Sampling System ◽  
Thermoacoustic Engines ◽  
And Control

Existing acoustic test benches are usually costly devices based on proprietary designs, sensors, and acquisition devices. In this paper, a low-cost test bench for acoustic purposes is introduced. The design of the test bench takes into account not only the low-cost mechanical design, but also uses low-cost sensors and control boards. This test bench has been designed for a range of signals compatible with those used by thermoacoustic engines, but it can be useful for applications with similar requirements. Taking advantage of an auxiliary pressure reference, low-cost unidirectional differential pressure sensors can be used to significantly increase the accuracy of the sampling system. The acoustic and mechanical design and development are presented along with the sampling system and the sensors arrangement implemented. Both the sensor and sampling system are evaluated by comparison with a high-fidelity sound acquisition system. An unexpected effect on the time error values distribution of the low-cost acquisition system is found and described. Finally, the errors introduced by the system and the sensors in terms of time and pressure sampling are characterized. As a result, the low-cost system’s accuracy has been satisfactory assessed and validated for the conditions expected in thermoacoustic experiments in terms of frequency and dynamic pressure.

Numerical and Experimental Investigations on a Centrifugal Pump With and Without a Vaned Diffuser

2004 ◽  
Author(s):  
G. Pavesi ◽  
G. Ardizzon ◽  
G. Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Pressure Sensors ◽  
Wake Flow ◽  
Experimental Investigations ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaned Diffuser ◽  
Return Channel ◽  
The Impact

Extensive research on centrifugal pumps was designed to investigate the impact of a diffuser on flow field instabilities and the noise generated by these instabilities. Activity was based upon a coupled use of measurements and 3D fully-viscous, unsteady computations. The test model was a seven-blade pump-turbine, used as a pump. Fitted with a vaneless diffuser, and two vaned diffusers with twenty-two adjustable, guide-diffuser vanes, and a return channel with eleven continuous vanes. Diffusers were equipped with eight pressure sensors in the adjustable guide-diffuser vanes, and nineteen pressure taps in the continuous vanes. To establish a link between the flow field structure and acoustic radiation, flow velocity was measured in the vaneless part of the diffuser. Piezoelectric transducers, placed flush with the wall, were used to measure pressure fluctuation inside the blade channels. Signal analysis was carried out in the frequency domain. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage, and destabilized jet-wake flow in the passage. This instability caused a periodic fluctuation at the discharge of the impeller. Fluctuations were found to be coherent from blade to blade, and to possess a rich harmonic content. Numerical analyses did not fully confirm these results.

Acoustic Characterization of Marine Sediments

1997 ◽  
Author(s):  
Anatoliy N. Ivakin ◽  
Darrell R. Jackson
Keyword(s):  
Marine Sediments ◽  
Acoustic Characterization

Low temperature acoustic characterization of PMN single crystal

2017 ◽  
Vol 122 (8) ◽  
pp. 084103 ◽  
Author(s):  
E. Smirnova ◽  
A. Sotnikov ◽  
S. Ktitorov ◽  
H. Schmidt
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Acoustic Characterization

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

Acoustic characterization of silica nanoparticle-impregnated Kevlar fabric

2021 ◽  
pp. 004051752110238
Author(s):  
Oluwafemi P Akinmolayan ◽  
James M Manimala
Keyword(s):  
Transmission Loss ◽  
Silica Nanoparticle ◽  
Air Gap ◽  
Thin Plates ◽  
Residual Porosity ◽  
Ballistic Performance ◽  
Number Of Layers ◽  
Structural Applications ◽  
Acoustic Characterization

Silica nanoparticle-impregnated Kevlar (SNK) fabric has better specific ballistic performance in comparison to its neat counterparts. For multifunctional structural applications using lightweight composites, combining this improved ballistic functionality with an acoustic functionality is desirable. In this study, acoustic characterization of neat and SNK samples is conducted using the normal-incidence impedance tube method. Both the absorption coefficient and transmission loss (TL) are measured in the 60–6000 Hz frequency range. The influence of parameters such as number of layers of neat or treated fabric, percentage by weight of nanoparticle addition, spacing between fabric layers, and residual porosity is examined. It is found that while absorption decreases with an increase in nanoparticle addition for frequencies above about 2500 Hz, increasing the number of layers shifts peak absorption to lower frequencies. By introducing an air-gap behind the fabric layer, dominant low-frequency (1000–3000 Hz) absorption peaks are obtained that correlate well with natural modes of mass-equivalent thin plates. Examining the influence of residual porosity by laminating the SNK samples reveals that it contributes to about 30–50% of the total absorption. Above about 1500 Hz, 3–5 dB of TL increase is obtained for SNK samples vis-à-vis the neat samples. TL is found to increase beyond that of the neat sample above a threshold frequency when an air-gap is introduced between two SNK layers. With an increase in the weight of nanoparticle addition, measured TL tends to be closer to mass law predictions. This study demonstrates that SNK fabric could provide improved acoustic performance in addition to its ballistic capabilities, making it suitable for multifunctional applications and could form the basis for the development of simplified models to predict the structural acoustic response of such nanoparticle–fabric composites.

scholarly journals Acoustic Characterization of Some Steel Industry Waste Materials

2021 ◽  
Vol 11 (13) ◽  
pp. 5924
Author(s):  
Elisa Levi ◽  
Simona Sgarbi ◽  
Edoardo Alessio Piana
Keyword(s):  
Thermal Characteristic ◽  
Environmental Benefits ◽  
Acoustic Properties ◽  
Physical Parameters ◽  
Industry Waste ◽  
Acoustic Characterization ◽  
Minimization Procedure ◽  
The Difference ◽  
By Products

From a circular economy perspective, the acoustic characterization of steelwork by-products is a topic worth investigating, especially because little or no literature can be found on this subject. The possibility to reuse and add value to a large amount of this kind of waste material can lead to significant economic and environmental benefits. Once properly analyzed and optimized, these by-products can become a valuable alternative to conventional materials for noise control applications. The main acoustic properties of these materials can be investigated by means of a four-microphone impedance tube. Through an inverse technique, it is then possible to derive some non-acoustic properties of interest, useful to physically characterize the structure of the materials. The inverse method adopted in this paper is founded on the Johnson–Champoux–Allard model and uses a standard minimization procedure based on the difference between the sound absorption coefficients obtained experimentally and predicted by the Johnson–Champoux–Allard model. The results obtained are consistent with other literature data for similar materials. The knowledge of the physical parameters retrieved applying this technique (porosity, airflow resistivity, tortuosity, viscous and thermal characteristic length) is fundamental for the acoustic optimization of the porous materials in the case of future applications.

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