Procedure to Estimate the In-Duct Sound Power in the High Frequency Range With Non-Plane Waves

2012 ◽  
Author(s):  
Antti Hynninen ◽  
Mats Åbom
Keyword(s):  
Plane Wave ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Plane Waves ◽  
Low Frequency ◽  
Sound Power ◽  
Combustion Engines ◽  
Duct Systems ◽  
Acoustic Characterization ◽  
Wave Range

The acoustic characterization of fluid machines, e.g., internal combustion engines, compressors, or fans is of great importance when designing the connected duct systems and its silencers. For machines connected to large ducts where also the non-plane wave range is important, for instance large diesels and gas turbines, a suitable way to characterize the source is to determine the sound power under reflection free conditions. For the low frequency plane wave range in-duct sound power can be measured with the widely used two microphone method. The goal of this study is to investigate how, starting from the two-microphone approach, a suitable wall mounted microphone configuration can be defined and used to estimate the propagating in-duct sound power also beyond the plane wave range. For this purpose an acoustic source test-rig was built and numerical simulations were also conducted. The in-duct sound power from monopole, dipole, and quadrupole source types was determined using twelve wall mounted microphones and cross-spectra averaging methods. The in-duct results were compared against sound power measured using the reverberation room method (ISO 3741). Based on the simulations and the experimental results the best microphone positions and weighting factors were determined.

The Acoustical Impedance at the Junction of Non-Coaxial Cylindrical Ducts

1992 ◽  
Vol 11 (4) ◽  
pp. 114-123 ◽  
Author(s):  
Keith S. Peat
Keyword(s):  
Plane Wave ◽  
Cross Section ◽  
Plane Waves ◽  
Low Frequency ◽  
Evanescent Waves ◽  
Wave Analysis ◽  
Cross Sectional ◽  
Low Frequencies ◽  
Duct Systems

At low frequencies, only plane waves can continuously propagate along uniform ducts, but evanescent, non-planar waves arise from discontinuities in the duct cross-section. The effect of these evanescent waves can be considered as an acoustical impedance to the propagation of plane waves. It is then possible to increase the accuracy of low frequency plane-wave analysis of duct systems with cross-sectional discontinuities, by inclusion of these impedance corrections. This paper considers the derivation of the acoustical impedance at the junction of non-coaxial circular ducts, a common feature within silencer systems.

Acoustic Source Characterization for Prediction of Medium Speed Diesel Engine Exhaust Noise

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Antti Hynninen ◽  
Mats Åbom
Keyword(s):  
Plane Wave ◽  
High Frequency ◽  
Low Frequency ◽  
Sound Power ◽  
Frequency Range ◽  
Engine Exhaust ◽  
Medium Speed ◽  
Exhaust Duct ◽  
Source Data ◽  
Wave Range

To achieve reliable results when simulating the acoustics of the internal combustion engine (IC-engine) exhaust system and its components, the source characteristics of the engine must be known. In the low frequency range only plane waves propagate and then one-port source data can be determined using, for example, the acoustic multiload method. For the medium speed IC-engines used in power plants and ships, the exhaust duct noise often needs to be analyzed up to 10 kHz, i.e., far beyond the plane wave range, and it is then more appropriate to use acoustic power to characterize the source. This power should ideally be measured under reflection-free conditions in the exhaust duct. The results from an earlier study showed that a suitable way to characterize the source for any frequency is to determine the in-duct sound power by extending the plane wave formulation with frequency band power weighting factors. The aim of this study is to apply this high frequency range method in situ to a real test engine. Another aim is to define, theoretically, how to combine the source data in the low frequency plane wave range with those in the high frequency nonplane wave range using a source sound power formulation.

https://elibrary.ru/item.asp?id=44369782&pf=1

2020 ◽  
Author(s):  
QI CHEN ◽  
◽  
JINTAO SUN ◽  
JIANYU LIU ◽  
BAOMING ZHAO ◽  
...  
Keyword(s):  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Nonequilibrium Plasma ◽  
Combustible Mixture ◽  
Combustion Engines ◽  
Combustion Chemistry ◽  
Microwave Radio ◽  
Different Types ◽  
Gas Molecules ◽  
Ignition And Combustion

Plasma-assisted ignition and combustion, widely applied in gas turbines, scramjets, and internal combustion engines, has been considered as a promising technique in shortening ignition delay time, improving combustion energy efficiency, and reducing emission. Nonequilibrium plasma can excite the gas molecules to higher energy states, directly dissociate or ionize the molecules and, thereby, has the potential to produce reactive species at residence time and location in a combustible mixture and then to efficiently accelerate the overall pyrolysis, oxidation, and ignition. Previous studies have demonstrated the effectiveness of plasma-assisted combustion by using direct current, alternating currant, microwave, radio frequency, and pulsed nanosecond discharge (NSD). Due to the complicated interaction between plasma and combustion in different types of plasma, detailed plasma-combustion chemistry is still not well understood.

scholarly journals Cogeneration Supporting the Energy Transition in the Italian Ceramic Tile Industry

2021 ◽  
Vol 13 (7) ◽  
pp. 4006
Author(s):  
Lisa Branchini ◽  
Maria Chiara Bignozzi ◽  
Benedetta Ferrari ◽  
Barbara Mazzanti ◽  
Saverio Ottaviano ◽  
...  
Keyword(s):  
Ceramic Tile ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Industrial Process ◽  
Energy Transition ◽  
Production Cycle ◽  
Combustion Engines ◽  
Total Consumption ◽  
Average Value ◽  
Ceramic Tile Production

Ceramic tile production is an industrial process where energy efficiency management is crucial, given the high amount of energy (electrical and thermal) required by the production cycle. This study presents the preliminary results of a research project aimed at defining the benefits of using combined heat and power (CHP) systems in the ceramic sector. Data collected from ten CHP installations allowed us to outline the average characteristics of prime movers, and to quantify the contribution of CHP thermal energy supporting the dryer process. The electric size of the installed CHP units resulted in being between 3.4 MW and 4.9 MW, with an average value of 4 MW. Data revealed that when the goal is to maximize the generation of electricity for self-consumption, internal combustion engines are the preferred choice due to higher conversion efficiency. In contrast, gas turbines allowed us to minimize the consumption of natural gas input to the spray dryer. Indeed, the fraction of the dryer thermal demand (between 600–950 kcal/kgH2O), covered by CHP discharged heat, is strictly dependent on the type of prime mover installed: lower values, in the range of 30–45%, are characteristic of combustion engines, whereas the use of gas turbines can contribute up to 77% of the process’s total consumption.

Calculation of Acoustic Efficiency of Exhaust Silencers for Automotive Internal Combustion Engines

2021 ◽  
pp. 41-47
Author(s):  
Vladimir Tupov ◽  
O. Matasova
Keyword(s):  
Acoustic Waves ◽  
Internal Combustion Engines ◽  
Combustion Engine ◽  
Control Point ◽  
Plane Waves ◽  
Exhaust System ◽  
Internal Combustion ◽  
Combustion Engines ◽  
Exhaust Noise ◽  
Insertion Losses

Insertion losses as the main characteristic that mathematically describes the acoustic efficiency of a noise silencer has been considered. This characteristic shows the reduction of noise generated by its source, in particular by the internal combustion engine’s exhaust system, at the control point as a silencer use result. Has been presented a mathematical description of the insertion losses, and have been considered parameters necessary for calculating this characteristic. Has been demonstrated the analytical dependence of impedance for the sound emission by the exhaust system’s end hole from the coefficient of acoustic waves reflection by this hole. The performed analysis of the widely used formulas for calculating the coefficient of sound reflection by the end hole has showed their insufficient accuracy for project designs performing. Have been proposed calculation dependences providing high accuracy for calculations of the reflection coefficient modulus, and the attached length of the channel end hole without a flange in the entire range of the existence of plane waves in it. It has been shown that the end correction of this hole at ka = 0 is 0.6127, and not 0.6133, as it was mistakenly believed until now in world acoustics. Has been proposed a method for calculation the exhaust noise source internal impedance. This method more accurately, in comparison with the already known ones, describes the acoustic processes in the internal combustion engine’s exhaust manifold, thanks to increases the accuracy of calculation the silencer acoustic efficiency, that allows develop the silencer at the early stages of the design of an automotive internal combustion engine.

scholarly journals A design tool for the performances comparison of innovative energy systems for naval applications

2019 ◽  
Vol 113 ◽  
pp. 02005
Author(s):  
D. Rattazzi ◽  
M. Rivarolo ◽  
T. Lamberti ◽  
L. Magistri
Keyword(s):  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Energy Systems ◽  
Design Tool ◽  
Pollutant Emissions ◽  
Combustion Engines ◽  
Wide Range ◽  
Storage Technologies ◽  
Market Solutions ◽  
And Storage

This paper aims to develop a tool for the performances comparison of innovative energy systems on board ships, both for concentrated and distributed generation applications. In the first part of the study, the tool database has been developed throughout a wide analysis of the available market solutions in terms of energy generation devices (i.e. fuel cells, internal combustion engines, micro gas turbines), fuels (hydrogen, natural gas, diesel) and related storage technologies. Many of these data have been collected also thanks to the laboratory experience of the authors’ research group on different innovative energy systems. From the database, a wide range of maps has been created, correlating costs, volumes, weights and emissions with the installed power and the operational hours required, given by the user as input. The tool highlights the best solution according to the different relevance chosen by the user for each key parameter (i.e. costs, volumes, emissions). In the second part, two different case studies are presented in order to underline how the installed power, the different ship typology and the user requirements affect the choice of the best solution. It is worth noting that the methodology has a general value, as the tool can be applied to both the design of new ships, and to the retrofit of already existing ships in order to respect new requirements (e.g. more and more stringent normative in terms of pollutant emissions in ports and restricted areas). Furthermore, the database can be easily extended to other generation and storage technologies.

scholarly journals AUTOMOBILE INTERNAL COMBUSTION ENGINE PRESSURE CHARGING AND GAS-GUIDE LOW FREQUENCY NOISE REDUCTION USING ACTIVE SOUND SOURCES

Akustika ◽  
2019 ◽  
Vol 34 ◽  
pp. 118-122
Author(s):  
Andrey Vasilyev
Keyword(s):  
Noise Reduction ◽  
Internal Combustion Engines ◽  
Acoustic Pressure ◽  
Combustion Engine ◽  
Low Frequency ◽  
Internal Combustion ◽  
Frequency Noise ◽  
Combustion Engines ◽  
Sound Sources ◽  
Automobile Engines

Pressure charging devices in different types of internal combustion engines is allowing to achieve a number of advantages: engine power and fuel effectiveness increasing, exhaust gases toxic reduction etc. Pressure charging systems may be classified by the different parameters. For the time being turbo-supercharger is the most popular unit of serial automobile engines pressure charging. But it has some negative properties. Therefore using of dynamic (acoustic) pressure charging devices is promising solution. Analysis of existing acoustic pressure charging systems is carried out. The perspectives of using of active sound emitters for acoustic pressure charging are described. Theoretical issues of automobile engines active acoustic charging are discussed. Construction of active charging system is suggested. Multifunctional approach to automobile internal combustion engines pressure charging and low frequency intake and exhaust noise reduction is suggested. The results described in this paper may be useful for further development and application of internal combustion engines with improved consumer’s and ecological characteristic.

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