Analýza vibrací a hluku studentské formule
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Tato práce se zabývá hlukem a vibracemi na voze studentské formule konstruované a vyrobené studenty na Technické univerzitě v Liberci v roce 2017. Po sezóně bylo jasné, že je potřeba začít hledat příčiny hluku a vibrací, protože je hluk omezen pravidly a vibrace jsou obecně na voze nežádoucí. Emise hluku prvního vozu byla blízká stanovenému limitu, proto by bylo dobré odhalit zdroje hluku. To je důležité, aby se mohly buď eliminovat, nebo využít nějakých řešení pro jeho snížení a tím i hladší průběh technické přejímky.Na začátku se vycházelo z předpokladu, že největším zdrojem hluku bude motor. Ostatní zdroje budou významně nižší. Pro zjištění těchto zdrojů bylo provedeno několik měření ve firmě VÚTS. Jako první bylo provedeno měření za účelem zjištění reálných hodnot podle metodiky pravidel (venku na asfaltové ploše s mikrofonem v definované poloze). Zde bylo bohužel zjištěno, že formule překročila při určitých režimech limit pravidel. Dále bylo změřeno hlukové pole kolem formule, abychom viděli místa, kde má formule největší hodnoty hluku, kvůli dalšímu vyhodnocování. Po té byly pořízeny snímky z mikrofonního pole. Na těch jsou už vidět předpokládaná místa s největším hlukem. Poslední měření pro identifikaci zdrojů bylo provedeno pomocí mikrofonů v místech největší intenzity zvuku akcelerometrů na motoru i v rámu, s měřením otáček motoru pomocí proudové sondy.Z tohoto měření jsou vyhodnoceny zdroje hluku. Potvrdil se předpoklad, že dominantní je hluk od motoru. Dále je vidět, že výfuk neplní dostatečnou tlumící funkci. Proto jsou navrženy optimalizace pro další generace formule. Například by byla vhodná lepší konstrukce výfuku, nebo je možnost využití zakrytování motoru karoserií s pohltivou pěnou.Reálné snížení hluku bude možné ověřit po dokončení nové formule a opětovném měření v podobných podmínkách. Na závěr byly změřeny doplňkové psychoakustické veličiny pro porovnání zvuku, který vydává formule.
This work deals with noise and vibrations on a car formula designed and produced by students at the Technical University in Liberec in 2017. After the season, it was clear that there is a need to start looking for the causes of noise and vibrations because the noise is limited by rules and the vibrations are generally on the car undesirable. The noise emissions of the first car were close to the legal limit, so it would be good to detect the sources of noise. This is important to either eliminate them or to use some solutions to reduce them and thus make the process of technical acceptance smoother.Initially, it was assumed that the engine would be the biggest source of noise. Other resources will be significantly lower. Several measurements were made in VÚTS for these sources. Measurements were first made to determine the real values according to the rules methodology (outside on the asphalt surface with the microphone). Unfortunately, it was found that the formula exceeded the rule limit for certain modes. We also measured the noise field around the formula to see where the formula has the highest noise value for further evaluation. Pictures were then taken from the microphone field. On these are already seen the predicted places with the greatest noise. The latest measurement for resource identification was performed using microphones at the highest sound intensities and accelerometers on both the engine and the frame, with engine speed measurement using a current probe.From this measurement noise sources are evaluated. The assumption was made that the motor noise was dominant. Furthermore, it can be seen that the exhaust does not fill up with sufficient damping function. Therefore, optimization is proposed for the next formula generation. For example, a better exhaust design would be appropriate, or the possibility of using a foam-absorbing bodywork engine.Real noise reduction will be possible after completion of the new formula and re-measurement under similar conditions. Finally, supplementary psychoacoustic quantities were evaluated to compare the sound produced by the formula.
This work deals with noise and vibrations on a car formula designed and produced by students at the Technical University in Liberec in 2017. After the season, it was clear that there is a need to start looking for the causes of noise and vibrations because the noise is limited by rules and the vibrations are generally on the car undesirable. The noise emissions of the first car were close to the legal limit, so it would be good to detect the sources of noise. This is important to either eliminate them or to use some solutions to reduce them and thus make the process of technical acceptance smoother.Initially, it was assumed that the engine would be the biggest source of noise. Other resources will be significantly lower. Several measurements were made in VÚTS for these sources. Measurements were first made to determine the real values according to the rules methodology (outside on the asphalt surface with the microphone). Unfortunately, it was found that the formula exceeded the rule limit for certain modes. We also measured the noise field around the formula to see where the formula has the highest noise value for further evaluation. Pictures were then taken from the microphone field. On these are already seen the predicted places with the greatest noise. The latest measurement for resource identification was performed using microphones at the highest sound intensities and accelerometers on both the engine and the frame, with engine speed measurement using a current probe.From this measurement noise sources are evaluated. The assumption was made that the motor noise was dominant. Furthermore, it can be seen that the exhaust does not fill up with sufficient damping function. Therefore, optimization is proposed for the next formula generation. For example, a better exhaust design would be appropriate, or the possibility of using a foam-absorbing bodywork engine.Real noise reduction will be possible after completion of the new formula and re-measurement under similar conditions. Finally, supplementary psychoacoustic quantities were evaluated to compare the sound produced by the formula.
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hluk, vibrace, formule SAE, měření a opatření ke snížení hluku, noise, vibration, formula SAE, measurements and precaution against noise