| 1. |
- Engström, Anders, et al.
(författare)
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COMPUTER-SIMULATION OF DIFFUSION IN MULTIPHASE SYSTEMS
- 1994
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Ingår i: Metallurgical and Materials Transactions. A. - 1073-5623 .- 1543-1940. ; 25:6, s. 1127-1134
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Tidskriftsartikel (refereegranskat)abstract
- A general model to treat multicomponent diffusion in multiphase dispersions is presented. The model is based on multicomponent diffusion data and basic thermodynamic data and contains no adjustable parameters. No restriction is placed on the number of components or phases that take part in the calculations, as long as the necessary thermodynamic and kinetic data are available. The new model is implemented into the DICTRA software, which makes use of THERMO-CALC to handle the thermodynamics. The model is applied to carburization of Ni alloys and heat treatment of welded joints between dissimilar materials. In both cases, the diffusion is accompanied by carbide formation or dissolution. A good agreement between experiments and calculations is found, despite the fact that no adjustable parameters are needed.
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| 2. |
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| 3. |
- Florén, Anders, et al.
(författare)
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Swedish Iron Before 1900
- 1993
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Ingår i: Ironmaking in Sweden and Russia. - Uppsala : Historiska institutionen, Uppsala universitet. - 9150609610 ; , s. 7-42
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
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| 10. |
- Johansson, Carin, et al.
(författare)
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Development of a lightweight wooden joist floor with high impact noise insulation
- 1994
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:1, s. 67-79
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the results of a project for the development of a lightweight wooden joist floor. The work has been carried out by the optimization of each of the variables which are important for sound insulation and has resulted in the construction of a framing of joists which has good impact sound insulation, small dimensions, can be constructed in a simple way at low cost and can be assembled in an easy and safe way. Forty-five different constructions and combinations were tested in the laboratory. The optimal construction was finally tested in several blocks of flats. In order for the construction to meet the Swedish Building Standards for sound insulation, the impact noise index Ii must not exceed 63 dB. The final construction had an index Ii of 52 dB in the laboratory and 53–58 dB in the field, and was thus approximately 10 dB better that the standard limit for impact noise between adjoining flats. The total weight of the construction is only 60 kg/m2 and the total thickness is 342 mm. Furthermore the framing of joists is economical and practical to manufacture in factories, is easy to transport without deformation and is easy to install in the building on the site.
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| 16. |
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| 17. |
- Johansson, Örjan, et al.
(författare)
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Source characterization of the lower front-end of a diesel engine
- 1996
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 49:4, s. 383-404
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Tidskriftsartikel (refereegranskat)abstract
- The lower front end of a diesel engine is a major noise source. Describing the source mechanisms of this area is problematic as it consists of a rotating torsional vibration damper in front of the timing transmission cover and the oil sump. This experimental study focuses on the acoustic interaction phenomena between the damper and the structure behind it. To describe the source mechanisms a test series of different modifications by conventional lead wrapping technique is performed. The vibration behaviour of each substructure is determined by operational deflection shape measurements and the source strength for each modification is determined by near-field sound intensity measurements. The results show the contributions from different substructures and describes the interference effects due to coherent radiation. It is concluded that the radiation is dominated by the timing transmission cover structure behind the damper. At some frequencies though, the torsional vibration damper in combination with the timing transmission cover behind it, causes the high radiation. This effect is mainly due
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| 18. |
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| 19. |
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| 21. |
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| 22. |
- Tingvall, Bror, et al.
(författare)
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Noise emissions from snowmobiles
- 1994
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Ingår i: Noise - quantity and quality. - Poughkeepsie, NY : Noise control foundation. ; , s. 407-410
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Konferensbidrag (refereegranskat)
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| 23. |
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| 24. |
- Villarroel, Grover Zurita, et al.
(författare)
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Ethanol-powered engine noise emissions : experimental study of combustion pulse characteristics
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Alcohol fuels are recognized as superior to petroleum fuels from the viewpoint of environmental safety and pollution. Alcohols are one of the most promising substitutes for the conventional petroleum fuels. The main problem, besides economy, with its applications being its low reactivity. The low reactivity leads to increased ignition difficulties and it also affects flame spreading and combustion. To improve the ignition properties ignition improvers can be used. The aim of this research report was to investigate the noise radiation from a modified 11 liter diesel engine running in ethanol conditions. In order to identify the noise sources on the combustion engine measurements were carried out of Combustion pulse characteristics, Sound intensity radiation, Sound pressure levels and Running modes (RMA). The vibrations of the engine mounts have also been studied through transfer functions analyses of the engine mounts.
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| 25. |
- Villarroel, G. Zurita, et al.
(författare)
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Reconstruction of cylinder pressure time trace on a six-cylinder engine from acceleration measurements.
- 1998
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Ingår i: Proceedings of ISMA 23. - Leuven : Katholieke universiteit. ; , s. 331-337
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Konferensbidrag (refereegranskat)abstract
- In diesel engines the combustion pressure waveform represents an ideal tool for detecting combustion anomalies. The cylinder pressure signal contains a lot of information about the condition of the engine and the combustion efficiency. It can also be used as identification of mechanical wears in the cylinders. There are growing demands for condition monitoring of diesel engines, and therefore the reconstruction of the cylinder pressure using a non-disruptive, externally mounted acceleration transducers measurements will be an aid in this work. Unfortunately the pressure is not easily measurable outside a laboratory environment, simple methodologies are therefore requested. This paper describes the theory and applications of "Time Domain Technique" [1] and the non-linear filtering technique known as Complex Cepstrum to reconstruction of the cylinder pressure
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| 26. |
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| 27. |
- Wu, L., et al.
(författare)
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A study of the initial decay rate of two-dimensional vibrating structures in relation to estimates of loss factor
- 1997
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 206:5, s. 663-684
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to obtain a better understanding of the process of the initial decay of energy in relation to the estimates of damping loss factor; to investigate the spatial variation of the initial decay rate in order to obtain more reliable estimates of damping loss factor from the decay rate method; and to compare the spatial averages and spatial variation of damping loss factor between the decay rate method and the power input method. The initial decay rate of energy was experimentally investigated on uniform plates. The energy mean free path time was introduced as a factor to characterize the lower limit of a decay interval for fitting an initial decay slope, and to determine the initial point of a decay curve. It is concluded that the initial decay slopes can sometimes be determined within a very short decay interval (e.g., less than 10 dB) provided that the corresponding time interval is larger or much larger than the energy mean free path time. Additionally. the effect of the direct field on the initial decay can be ignored provided that the response point is far enough from the drive point. An analysis of the spatial variation of initial decay rate showed that an increase in the number of modes per band, and light and moderate damping can reduce the spatial variation. High damping may increase the spatial variation. For a frequency band with more modes, fewer response points need to be used to obtain a stable estimation of spatial variance. It was confirmed that the damping loss factor determined from the decay rate method was in general in good agreement with the power input method. The comparison of the spatial variances of damping loss factor between the two methods showed that the decay rate method gives a more reliable estimate of the damping loss factor of the plates. It is concluded that the decay rate method is to be preferred to the power input method when determining the damping loss factor of a system.
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| 28. |
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| 29. |
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| 30. |
- Wu, Lie, et al.
(författare)
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Analysis of initial decay rate in relation to estimates of loss factor and equivalent mass in experimental SEA
- 1996
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Ingår i: Proceedings of ISMA 21. - Leuven : Katholieke Univ. Leuven. ; , s. 187-198
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Konferensbidrag (refereegranskat)abstract
- The initial decay rate for single and coupled plates is studied in relation to the consistency of the loss factors between the energy and decay methods. It is confirmed that a shorter decay range of the first 10 dB decay, rather than two larger decay intervals from 0 to -30 dB or from -5 to -35 dB, gives a much better agreement between the methods. Mean free path time is introduced to facilitate the selection of the initial decay interval and the initial point of reverberation decay. It is found, in general, that to obtain a small spatial variation of the initial decay rate, at least four modes per band are needed. The repeatability of the associated loss factor can be made within +/-1 dB with 95 percent confidence level. In addition, the initial decay rate is applied to investigate the property of equivalent mass. It is verified experimentally that the strong coupling has a significant influence on initial decay rate and equivalent mass. It is shown that the equivalent mass has to be used for the estimation of total energy of a complex subsystem where only a limited number of measurement points can be selected and only a part of the subsystem can be accessible for the measurement. It is also explained why the equivalent mass can be larger than the actual mass for a complex subsystem.
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| 31. |
- Wu, Lie, et al.
(författare)
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Applicability of the experimental statistical energy analysis to an engine structure
- 1995
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Ingår i: Proceedings of the 1995 Noise and Vibration Conference : [SAE Noise & Vibration Conference and Exposition, Traverse City, Michigan, May 15 - 18, 1995]. - Warrendale, Pa. : Society of Automotive Engineers, Incorporated. - 1560916664
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Konferensbidrag (refereegranskat)abstract
- TheStatisticalEnergyAnalysis (SEA) method has been shown to be a powerful predictive tool of structural-acoustic design. However, there are many difficulties when the method is applied to an engine structure. It is because: 1) the engine structure is so complicated that both the internal and coupling loss factors have to be determined in situ by measurements; and 2) the general matrix inversion to calculate the loss factors, with the power injection method, can not simply be used as it produces many negative and unreliable results. The problems are attacked with several new approaches, which include using the equivalent mass, the selective geometric averaging, the consistency and reciprocity relationships, the back estimation technique and the coupling damping. Finally, an experimental validation is done. It shows that the obtained SEA model generally can predict the vibration tendency ofthe engine structure when damping and isolation treatments are applied. It is also concluded that the drive points should be selected in places as far as possible from the coupling lines and one or two drive points for each subsystem may be enough in engineering practice.
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| 32. |
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| 33. |
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| 36. |
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| 37. |
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| 38. |
- Zurita-Villarroel, Grover, et al.
(författare)
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Multivariate analysis of engine noise and exhaust emissions from an ethanol-fueled diesel engine
- 1997
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Ingår i: Proceedings of the 1997 noise and vibration conference. - Warrendale, Pa. : Society of Automotive Engineers, Incorporated. - 0768000122
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Konferensbidrag (refereegranskat)abstract
- The engine manufacturers have to meet more and more stringent regulations on both noise and exhaust emissions in the future requiring extensive optimization of all parameters of the engine. Soft modeling with statistically designed experiment (SDE) and Multivariate Analysis (MVA) can be an aid in this work. The analyses are based on cylinder pressure data, engine data and exhaust emissions data, with all measurements performed simultaneously. The effects of changes in fuel quality, load, speed, and injection timing on combustion noise and exhaust emissions were investigated using SDE and MVA. The engine was a modified 6-cylinder, direct-injection diesel engine running on ethanol. The paper demonstrates the applicability of experimental design and multivariate methods for modeling and minimization of noise and exhaust emissions.
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| 39. |
- Zurita-Villarroel, Grover, et al.
(författare)
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Reconstruction of the cylinder pressure from vibration measurements for prediction of exhaust and noise emissions in ethanol engines
- 1999
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Ingår i: Proceedings of the 1999 Noise and Vibration Conference. - Warrendale, Pa : Society of Automotive Engineers, Incorporated. - 0768004101
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Konferensbidrag (refereegranskat)abstract
- There are growing demands for condition monitoring of IC engines, and therefore any method in order to improve the performance of the engines ought to be evaluated. This paper proposes a new approach for the prediction and optimisation of noise and exhaust emissions in IC engines. The idea is to reconstruct the cylinder pressure from vibration measurements on the engine surface by using the complex cepstrum method. The reconstructed cylinder pressure is further used as input in multivariate models, based on cylinder pressure, for estimating noise and exhaust emissions. This paper demonstrates the applicability of the method for modelling of noise and exhaust emissions.
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| 40. |
- Zurita-Villarroel, Grover, et al.
(författare)
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Wavelet transform analysis of measurements of engine combustion noise
- 1997
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Ingår i: Proceedings of the 1997 noise and vibration conference. - Warrendale, Pa. : Society of Automotive Engineers, Incorporated. - 0768000122
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Konferensbidrag (refereegranskat)abstract
- Wavelet transform analysis is capable of revealing aspects of data that other techniques miss; such aspects are trends, and discontinuities in higher derivates. This method can often compress or de-noise a signal without any appreciable degradation and it provides accurate information on the localization of energy content in time and frequency. The wavelet transform method has been applied to the analysis of combustion noise and piston slap in order to identify the effects on the engine structure vibration. The experimental results showed that combustion noise and piston slap were successfully detected from the acceleration signals picked up by external transducers in the outer wall of an in-line, 6-cylinder diesel engine.
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| 41. |
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| 42. |
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| 43. |
- Ågren, Anders, et al.
(författare)
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Experimental study of repeatability errors in 3D sound intensity measurements in narrow frequency bands
- 1994
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Ingår i: Applied Acoustics. - 0003-682X .- 1872-910X. ; 43:2, s. 95-111
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Tidskriftsartikel (refereegranskat)abstract
- When investigating the 2D or 3D intensity of complex ‘real life’ noise sources, rather than the intensity normal to a surface, to obtain more detailed information about the radiated sound field great care has to be taken both in measuring and in interpreting the results. In this study it is shown that in measurements of 3D intensity for fixed points and in narrow frequency bands, large errors can be expected for a well-defined simple source if the positioning is imprecise and for a complex source even if the positioning device and the probe are of highest quality. Comparisons have been made between a two-microphone and a six-microphone probe, hand-held and robot-controlled. The comparisons show that, except for the case of an ideal measurement with a simple source and a high-precision robot, significant errors can be expected for all the tested measurement cases. The measurements also show that the positioning of the microphone is of major importance for the repeatability accuracy. The accuracy obtained with a 3D-probe is notably better than with a 1D-probe. The errors when measuring the complex source with a robot-controlled 3D-probe, however, are still so high, especially for the non-dominant directions, that interpretations have to be made with great care. Under non-ideal measurement conditions, the errors are found to be exponentially dependent upon the sound field pressure/intensity relationship (the pI-index).
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| 48. |
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| 49. |
- Ågren, Anders, et al.
(författare)
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Noise reduction of diesel engines with internal stiffeners
- 1997
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Ingår i: Noise Control Engineering Journal. - : Institute of Noise Control Engineering (INCE). - 0736-2501 .- 2168-8710. ; 45:1, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- In recent years there has been an increased interest from truck manufacturers in reducing the noise from internal combustion engines through stiffening solutions like bearing beams, ladder frames, and bedplates. This paper presents a short literature review of experiences published on the topic. Results of an experimental study of engine modifications with a bearing beam, a ladder frame, and an isolated oil sump are presented as well. The beam and the frame were designed so that they can be installed together without vibration propagating connections and to give high stiffness in the areas where they are most effective. The study was performed on a relatively light 9-liter six-cylinder diesel engine with an engine block of deep skirt type. The influence of the engine modifications was investigated through measurements of sound intensity, sound pressure, running modes, internal and external vibrations, and mobility. The results show that a ladder frame effectively reduces the noise from a deep skirt engine and that the reductions are substantially increased by isolation of the oil sump. The results also show where the components of the ladder frame are effective and that a bearing beam can be an unsuitable solution for deep skirt engines as resonances are shifted to higher frequencies that can be more effectively transferred and radiated.
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