scholarly journals Acoustic Source Data for Medium Speed IC-Engines

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antti Hynninen ◽  
Raimo Turunen ◽  
Mats Åbom ◽  
Hans Bodén
Keyword(s):  
High Frequency ◽  
Internal Combustion Engines ◽  
Low Frequency ◽  
Acoustic Source ◽  
Ic Engine ◽  
Source Characteristics ◽  
Medium Speed ◽  
Source Data ◽  
Exhaust Noise ◽  
Ic Engines

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.

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.

Acoustic Modelling and Measurements of Engine Mufflers

1998 ◽  
Vol 5 (1) ◽  
pp. 27-38
Author(s):  
Samir N.Y. Gerges ◽  
Márcio R. Kimura ◽  
J.L. Bento Coelho
Keyword(s):  
Internal Combustion Engines ◽  
Transmission Loss ◽  
Noise Source ◽  
Internal Combustion ◽  
Industrial Applications ◽  
Combustion Engines ◽  
Acoustic Modelling ◽  
Exhaust Noise ◽  
Ic Engines ◽  
Diesel Motors

Most buildings such as hospitals, hotels, governmental offices, data processing rooms, etc, are equipped with internal combustion engines, diesel motors and generators to supply energy in emergencies. These same IC engines are used for industrial applications, building services and transportation. Exhaust noise are the predominant noise source with most internal combustion engines and thus exhaust systems incorporating mufflers have been designed to reduce the noise. This paper describes the analysis of several configurations of mufflers and also presents comparisons between the results for the transmission loss obtained by numerical modelling (FEM), Transfer Matrix Method (TMM) and measurements.

scholarly journals Multi-parametric investigation of the volcano-hydrothermal system at Tatun Volcano Group, Northern Taiwan

2012 ◽  
Vol 12 (7) ◽  
pp. 2259-2270 ◽  
Author(s):  
S. Rontogianni ◽  
K. I. Konstantinou ◽  
C.-H. Lin
Keyword(s):  
Hydrothermal System ◽  
High Frequency ◽  
Linear Method ◽  
Low Frequency ◽  
Fluid Circulation ◽  
Magma Body ◽  
Local Seismicity ◽  
Source Characteristics ◽  
Magmatic Gases ◽  
Northern Taiwan

Abstract. The Tatun Volcano Group (TVG) is located in northern Taiwan near the capital Taipei. In this study we selected and analyzed almost four years (2004–2007) of its seismic activity. The seismic network established around TVG initially consisted of eight three-component seismic stations with this number increasing to twelve by 2007. Local seismicity mainly involved high frequency (HF) earthquakes occurring as isolated events or as part of spasmodic bursts. Mixed and low frequency (LF) events were observed during the same period but more rarely. During the analysis we estimated duration magnitudes for the HF earthquakes and used a probabilistic non-linear method to accurately locate all these events. The complex frequencies of LF events were also analyzed with the Sompi method indicating fluid compositions consistent with a misty or dusty gas. We juxtaposed these results with geochemical/temperature anomalies extracted from fumarole gas and rainfall levels covering a similar period. This comparison is interpreted in the context of a model proposed earlier for the volcano-hydrothermal system of TVG where fluids and magmatic gases ascend from a magma body that lies at around 7–8 km depth. Most HF earthquakes occur as a response to stresses induced by fluid circulation within a dense network of cracks pervading the upper crust at TVG. The largest (ML ~ 3.1) HF event that occurred on 24 April 2006 at a depth of 5–6 km had source characteristics compatible with that of a tensile crack. It was followed by an enrichment in magmatic components of the fumarole gases as well as a fumarole temperature increase, and provides evidence for ascending fluids from a magma body into the shallow hydrothermal system. This detailed analysis and previous physical volcanology observations at TVG suggest that the region is volcanically active and that measures to mitigate potential hazards have to be considered by the local authorities.

scholarly journals Modelling of the thermal cycle of a gas engine using AVL FIRE Software

2010 ◽  
Vol 141 (2) ◽  
pp. 105-113
Author(s):  
Wojciech TUTAK ◽  
Arkadiusz JAMROZIK
Keyword(s):  
Thermal Cycle ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Control Engineering ◽  
Ic Engine ◽  
Gas Engine ◽  
Combustion Models ◽  
Crank Angle ◽  
Ic Engines ◽  
And Control

Paper presents results of modelling gas engine thermal cycle using AVL FIRE and KIVA 3V software. There are described three combustion models used in software. KIVA and FIRE software are used in Institute of Internal Combustion Engines and Control Engineering for analysis of thermal cycle of IC engines. FIRE software gives many possibilities with many combustion models. All used combustion models are dependent on turbulence of flow field before ignition. Comparison of modelling results of thermal cycle of IC engine is presented in paper. Pressure, temperature, heat release and turbulence parameters variations in function of crank angle as well as spatial distribution of above mentioned quantities at selected crank angles were determined.

Seismic source characteristics from explosion-generated P waves

1968 ◽  
Vol 58 (6) ◽  
pp. 1833-1848 ◽  
Author(s):  
Lynn D. Trembly ◽  
Joseph W. Berg
Keyword(s):  
High Frequency ◽  
Transfer Functions ◽  
Low Frequency ◽  
Seismic Energy ◽  
Seismic Source ◽  
Propagation Path ◽  
P Waves ◽  
Nuclear Explosions ◽  
Source Characteristics ◽  
The Earth

ABSTRACT Signals from nuclear explosions were used to calibrate seismograph stations (near-regional, regional, and teleseismic ranges) by determining the transfer functions of the lumped source-propagation path-receiver systems. Recorded signals other than those used for calibration purposes were used to derive the characteristics of the sources. It was found that source functions could be derived from distant signals when the frequencies of the output signals were reliably related to the source. For the output data used in this research, the low-frequency cutoff was 0.2 cps at all stations and the high-frequency cutoffs were 4.0, 3.0, and 2.0 cps at the near-regional, regional, and teleseismic distances, respectively. The low-frequency cutoff was due mainly to the recording instruments, and the high-frequency cutoffs were due to the attentuation of the seismic energy by the Earth. The most reliable results were obtained when three half-cycles of the observed output signals (first arrivals) were used. When explosions in granite were used as calibration sources, the energies derived for explosions in tuff, alluvium, and dolomite media were 88, 65, and 12 per cent of the respective “observed” source energies.

Noise Reduction of Low-frequency Exhaust Noise for Medium-Speed Engine Using End Reflection Effect

2021 ◽  
Vol 45 (7) ◽  
pp. 615-621
Author(s):  
Seongjong Park ◽  
Bongman Jin ◽  
Daehee Lee ◽  
Heesung Lee ◽  
Dongyeon Lee ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Reflection Effect ◽  
Medium Speed ◽  
Medium Speed Engine ◽  
Exhaust Noise ◽  
Speed Engine

Wave Rotor Design Procedure for Gas Turbine Enhancement

2008 ◽  
Author(s):  
Ludeˇk Pohorˇelsky´ ◽  
Pranav Sane´ ◽  
Tomas Rozsas ◽  
Norbert Mu¨ller
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Exchange Process ◽  
Design Procedure ◽  
Internal Combustion ◽  
Wave Rotor ◽  
Ic Engine ◽  
Analytical Algorithm ◽  
Ic Engines

This paper presents an analytical design procedure for pressure wave machines, also known as wave rotors, to enhance gas turbines and internal combustion (IC) engines in a topping or bottoming cycle. The advantage of using a wave rotor for improving the performance of gas turbines or internal combustion engines is that it uses a pressure and enthalpy exchange process. Employing pressure or even shockwaves for the energy transfer, no mechanical parts like pistons or blades are necessary inside the chamber (channel) that houses the process, which increases the air pressure delivered to the combustor of a gas turbine or cylinder of an internal combustion (IC) engine. The wave rotor has found fair success in its application to IC engines. Research and development continues for both, applications in IC engines and its originally envisioned application in gas turbines. Here an analytical 1-D algebraic wave model is realized by utilizing shockwave theory and linear gas dynamic principles to model the process in a 4-port wave rotor, with five wave reflections in the low pressure part for better gas scavenging. Using this analytical model, a comprehensive design space has been investigated and documented in performance maps. From this, conclusions and recommendations are drawn for performance and geometry optimization. The analytical algorithm has been validated using a 1-D commercial code GT-POWER and 2-D CFD code FLUENT. While here the interest is mainly in steady state operation, the analytical algorithm also models transient processes.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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