Wyniki wyszukiwania - BazTech

1

Model wibroakustyczny bariery dźwiękochłonnej przy ruchomym zaburzeniu akustycznym

Błażejewski A., Kamiński K., Krzyżyński T.

TTS Technika Transportu Szynowego

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2013

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R. 20, nr 10

1977--1986, CD

PL

Praca prezentuje sposób modelowania wzajemnego oddziaływania fali akustycznej oraz ciał sprężystych. Zjawisko takie ma miejsce na drodze, po której poruszają się pojazdy, a wzdłuż niej znajdują się obiekty, takie jak bariery dźwiękochłonne. Do opisu poszczególnych zagadnień zastosowano model propagacji fali akustyczny w powietrzu w postaci równania falowego oraz model odkształceń w ciałach liniowo-sprężystych opisany równaniami teorii sprężystości. Sprzężenia obu modeli dokonano poprzez odpowiednie sformułowanie właściwych każdemu ze zjawisk warunków brzegowych na powierzchniach interakcji. Zastosowano metodę elementów skończonych do rozwiązania odpowiednich równań w celu wyznaczenia rozkładu pola akustycznego oraz drgań bariery. Wyniki symulacji przedstawiono dla wybranych konfiguracji konstrukcji oraz materiałów bariery, a także częstotliwości wymuszenia.

EN

Paper presents the case of the acoustic wave and linear elastic solids interaction modeling. The phenomenon happens on a road, where vehicles moves and along the road objects in the form of noise barriers exists. In order to describe respective problems, the model of acoustic wave propagation in air in the wave equation form and the model of linear elastic solid deformations in the linear theory of elasticity equations form are applied. Both models are coupled by properly formulated boundary conditions for surfaces where phenomena interacts each other. The finite element method is used to solve respective equations in order to calculate acoustic field distribution and noise barrier vibration. The simulation results are presented for chosen barrier constrictions and materials as well different frequency excitation.

2

Adaptation of engine vibration characteristics for diagnostics of mechanical defects

Komorska I., Górnicka D.

Silniki Spalinowe

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2011

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R. 50, nr 3

EN

An engine vibration and noise signal being applied for the engine combustion assessment contains also information on: a valve clearance, head gasket damage and wearing out of elements of a vehicle driving system. As the engine mileage increases the wearing out of driving system elements also increases, and in consequence the characteristics of vibration and noise generated by individual sub-assemblies are changing. Diagnosing of defects can be performed on the grounds of the model-based vibroacoustic signal by comparing the measured signal with this model. However, this model should be adapted after each changes of driving system elements and after each engine overhaul. Thus, it should be easily and fast automatically identifiable. The problem of changing vibration characteristics was illustrated on the example of the new Ford Fiesta engine and Fiat Punto engine of a considerable mileage (400 000 km). Time histories and vibration spectra for the engine in a good working condition and for the engine with the damaged exhaust valve were presented. Methods of generating the base model and its identification were proposed.

PL

Sygnał drgań i hałasu silnika jest wykorzystywany do oceny spalania w silniku ale niesie też informacje o luzie zaworowym, uszkodzeniu uszczelki głowicy i zużyciu elementów zespołu napędowego pojazdu. W miarę wzrostu przebiegu silnika rośnie zużycie elementów układu napędowego, a co za tym idzie, zmieniają się charakterystyki drgań i hałasu generowane przez poszczególne podzespoły. Diagnozowanie uszkodzeń można przeprowadzać na podstawie modelu bazowego sygnału wibroakustycznego przez porównanie sygnału zmierzonego podczas eksploatacji silnika z tym modelem. Jednak model ten powinien ulec adaptacji po każdorazowej wymianie elementów zespołu napędowego i każdym remoncie silnika. Musi więc być łatwo i szybko identyfikowalny, najlepiej w sposób automatyczny. Problem zmiany charakterystyk drganiowych przedstawiono na przykładzie drgań nowego silnika Ford Fiesta i silnika Fiat Punto o znacznym przebiegu (400 tys. km). Przedstawiono przebiegi czasowe i widma drgań dla silnika sprawnego i z wypalonym zaworem wylotowym. Zaproponowano metody generowania modelu bazowego i jego identyfikacji.

3

Utilising the resonance frequency of the engine vibration sensor in diagnostics of the exhaust valve leakage

Komorska I.

Journal of KONES

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2010

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Vol. 17, No. 2

209-216

EN

A vibroacoustic signal of an internal combustion engine contains several diagnostic information, which are -for the most part - not utilised since they require complex processing methods in order to separate useful data and to eliminate disturbances. The way of analysis ofsuch complex signal depends on the diagnostic aim. It is a rich source of information not only concerning the combustion process, but also various mechanical defects occurring in the driving system (valves, clutch, gearbox). Wear of elements as well as small mechanical defects cause the adaptation of the control system to new parameters. Thus, in many cases these adaptive systems can be masking mechanical defects. Burning out of exhaust valves or an improper valve clearance are examples of such defects. The method of diagnostics of leakages in a system: exhaust valve - cylinder, on the basis of measuring the vibration signal of the engine head is proposed in the paper. The results of the analysis of the engine vibration signal under conditions of a defected exhaust valve and an increased valve clearance are presented. The active diagnostic experiment was performed on the engine of Fiat Punto 1.2. During road tests the vibrations acceleration signal was recorded as well as certain auxiliary signals used for a synchronisation and identification of engine timing. The natural acceleration of vibrations in the resonance frequency range of the piezoelectric sensor was utilized. The vibration signal was pre-processed i.e. filtered, synchronously averaged and windowed. Satisfying diagnostic results of the valve defect or the improper valve clearance were obtained on the basis of the analysis of the engine vibration acceleration signal envelope. The signal measures explicitly indicating the valve condition were determined. The method, after certain modifications, can be applied for the on-line valve diagnostics.

4

The diagnostic model proposition of the engine vibration signal

Komorska I.

Journal of KONES

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2008

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Vol. 15, No. 2

191-197

EN

Vibroacoustic signal of reciprocating engine carries diagnostic information that is not efficiently used because of complicated signal processing methods for separation of useful components and noise elimination. The measured vibrations are a mixture of periodic waves due to the rotating components and transient waves due to the reciprocating components of the engine and pressure forces. Engine vibrations may be described in several ways depend on the diagnostic purpose. For detecting non-uniform cylinder operation, for instance, the methods for rotating machines can be considered. Many transients occur in vibration signal of the combustion engine like exhaust and inlet valve operations, fuel injection, combustion, piston slap. To analyze them the time-frequency methods can be used. Diagnosing of some damages, like valve clearance changing or valve burning, can be done using the diagnostic model. This model should be rather simple and sensitive to mentioned damages. In modelling two approaches can be considered. The first one is based on the real physical parameters of the system. The second one is making the abstractive statistical model of signal with abstractive parameters. In the paper the autoregressive model is proposed. Identifying model is finding periodically time-varying coefficients of the equivalent filter. All the damages in the system make changes of the coefficients. The model presented in the paper is illustrated with the signal of spark ignition combustion engine.