A poluição sonora urbana, em especial a gerada por motocicletas com escapamentos modificados, afeta indistintamente a saúde de toda população de diversas maneiras e tende a aumentar, ao contrário da emissão de gases, que vem se reduzindo ao longo dos anos. Com o objetivo de conter o ruído gerado pelo tráfego urbano, vários países desenvolvem procedimentos, leis e ações mitigatórias como barreiras acústicas e asfaltos fonoabsorventes, porém há grande quantidade de motocicletas, veículo tipicamente de alto potencial de incômodo e ruidoso, que circulam com sistemas de escapamento adulterados e emitem ainda mais excesso de ruído. A inspeção veicular é ferramenta importante no controle de emissões de gases poluentes de veículos em uso, mas falha em restringir aqueles que ultrapassam os limites legais de ruído e, somado a isto, há o agravante de o condutor submeter-se a poluição sonora que ele mesmo produz. A fiscalização de rua surge como alternativa de controle ambiental, mas algumas vezes é contestada por ser subjetiva ou por faltar uma metodologia simples, confiável e eficaz. Buscou-se então compreender a relação entre o aumento do nível sonoro da motocicleta com escapamento modificado ao circular no trânsito e a emissão sonora medida na condição de inspeção, o chamado ruído parado, para trazer subsídios à formação de métodos mais eficazes de fiscalização e controle. Para isto foram avaliadas motocicletas quanto à emissão de ruído em circulação e ruído parado e os resultados obtidos apontam que os escapamentos modificados possuem nível sonoro muito mais elevado que os originais, com forte correspondência entre os dois métodos de medição. Esta poluição sonora atinge de modo particularmente intenso os profissionais, motoboys, que modificam suas motocicletas, pois eles se submetem a todos os fatores que favorecem a perda auditiva por excesso de ruído. Outras questões surgiram em paralelo ao tema principal e foram brevemente avaliadas para se compor o quadro geral, como o nível sonoro de escapamentos não originais avaliados segundo os procedimentos de homologação, a contribuição que a motocicleta traz ao ruído urbano e que resultados estes trazem quanto ao torque e potência da motocicleta. Estes estudos indicaram que a motocicleta modificada contribui fortemente para a poluição sonora urbana, afetando principalmente o condutor e sem trazer ganhos efetivos em termos de potência e dirigibilidade. / The urban noise pollution, in particular the one produced for motorcycles with tampered exhaust systems, affects indistinctly the health of all people in many ways and tends to grow up, in opposite to gaseous emissions, that is getting down through years. With the goal of mitigate noise generated from urban traffic, many countries develop procedures, laws and actions as acoustic barrier and phono absorbent asphalt, but there are still a great amount of motorcycles, typically a high annoying and noisy vehicle, running with tampered mufflers and producing excessive noise. In use vehicle inspection is an important tool on gaseous emissions control but fails to restrain excessive noise, a problem that get worse up due the rider is subjects him/herself to the own sound pollution. Roadside control comes as an alternative but sometimes is rejected as subjective or due a lack of a simple, easy, trustable method. This research looks for the relationship between increased sound level of modified motorcycles in traffic and noise emission in inspection mode, also known as stationary noise, to bring subsidies to develop more efficient control methods. For this, it were evaluated motorcycles for traffic and stationary noise emission and the results point that modified exhaust systems have a very higher sound level than original mufflers, with strong relationship between these two measurement methods. This sound pollution affects in a very special mode the professionals, called in Brazil motoboys, which modify their motorcycles, because they subjected themselves to all factors for noise-induced hearing loss. Other questions come in parallel to the main focus and were briefly studied in order to compound the whole picture as sound level of replacement mufflers according homologation procedures, the motorcycle contribution to the urban sound pollution and the results for power and torque. These studies point to that modified motorcycles strongly contribute to urban noise, affecting especially the driver and with no effective gain in engine power and motorcycle handling.

This master´s thesis describes design and optimalization of the exhaust mainfold and an effective muffler for BMW 320i E30 car. This car is equipped with 6 cylinder engine M20B20. The construction is carried out with regard to the rules laid down by FAS Czech Republic. I used theoretical knowledge and Lotus Engine Simulation software in this thesis.

This master´s thesis describes design and optimalization of the exhaust mainfold and an effective muffler for BMW 320i E30 car. This car is equipped with 6 cylinder engine M20B20. The construction is carried out with regard to the rules laid down by FAS Czech Republic. I used theoretical knowledge and Lotus Engine Simulation software in this thesis.

To be able to predict the sound pressure level emitted by a exhaust system one must be able to describe the source. The source in the form of an engine can linearly be described as a source strength and a source impedance. An IC-engine can acoustically have a non-linear part meaning that the source characteristics have a dependency on the load. The first part of this work investigates through simulation's in GT-Power how these characteristics are affected by the load connected to the source. The Second part of the work combines the source characteristics with simulations of a muffler and compares to different methods of getting the pressure at the outlet of the exhaust. The first method is direct simulation of the muffler in COMSOL Multiphysics and the second is a transfer matrix based calculation. How sensitive the results at the outlet are to changes in the source impedance is also tested. It is concluded that using five loads for the multiload method in the form of five different lengths on the pipe connecting the engine and muffler works when the pipe have the same length as would be seen in reality. Furthermore, the pipe lengths should have a small range, 100 mm between largest and smallest pipe length giving good results. The source characteristics were at least above 1000 RPM stable enough as to not significantly change the sound pressure level at the outlet. / För att kunna modellera ljudtrycket som avges från ett avgassystem behöver man kunna beskriva källan. Källan i form av en bränslemotor kan linjärt beskrivas som en källstyrka och en källimpedans. En bränslemotor kan dock ha en akustisk ickelinjär del vilket medför att källan kan vara beroende utav vilken last i form av ljuddämpare den är kopplad till. Första delen av detta arbete undersöker genom motorsimuleringar i GT-Power hur lasten påverkar källkarakteristiken. Den andra delen av arbetet kombinerar källkarakteristiken med simuleringar av ljuddämparen och jämför olika metoder för att få ljudtrycket vid utloppet av avgassystemet. Den första metoden för detta är direkt simulering av ljuddämparen i COMSOL Multiphysics där källkarakteristiken inkluderas och den andra metoden är transfermatris baserad. Det testas också hur känsligt ljudtrycket vid utloppet av ljuddämparen är för variationer i impedansen. För källkarakteristiken används fem laster per uträkning och slutsatsen dras att lasten i form av röret mellan motor och ljuddämpare samt ljuddämparen bör vara så lik som möjligt det riktiga systemet. Utöver det dras slutsatsen att en liten variation i det kopplande rörets längd ger bättre resultat och att en variation mellan största och minsta röret på 100 mm ger bra resultat. Till sist dras slutsatsen att för varvtal över 1000 RPM är källkarakteristiken tillräckligt stabil för att ge stabila resultat vid utloppet av ljuddämparen, medans under 1000 RPM kan det vara stabilt nog men här är validering viktigare.

Dans les systèmes d'échappement automobile, les sources de bruit d'origine aéro-acoustique représentent une partie importante du contenu fréquentiel, objectivement et subjectivement identifiable. De robustes procédures de tests ont été mises en place mais la simulation du contenu du bruit n'a pas encore fait ses preuves dans les processus de développement au quotidien. Cette thèse montre que le bruit aéro-acoustique provenant de sources type dipôle est dominant pour ce qui concerne les systèmes automobiles. La simulation des écoulements à l'origine de ces bruits spécifiques combinée avec les outils de calculs acoustiques classiques est très lourde voir tout simplement impossible. Le but de cette thèse est d'analyser la loi d'échelle pour des modèles de sources compactes, permettant de déterminer l'émission de la puissance acoustique selon différentes configurations géométriques "simples" et généralement répandues (par ex. tube perforé, diaphragme placé dans un tube…) basées sur des données empiriques. Il est démontré à l'aide de simulations que son utilisation est simple et que la précision de ces modèles de sources est satisfaisante si l'on ne s'écarte pas trop des géométries déjà analysées. / On automotive exhaust systems aero acoustic noise is a dominant and critical noise content, which is clearly objectively and subjectively detectable. Robust test procedures are established but the simulation of this noise content has not gained ground in the real life development processes. This thesis shows that the dominating characteristic of the aero acoustic noise of automotive systems is dipole noise. The simulation of these specific noise sources with classical computational areo acoustics is very cumbersome or even just impossible. The aim of the thesis is a review of the scaling law approach for compact source models, enabling the determination of the sound power emission of discret configurations based on empirical data. Application simulations show that the use of these source models is simple and that the accuracy is acceptable within the geometry limits analysed.

This thesis deals with the complex analysis of dynamic characteristics of the exhaust system and the transmission of noise from exhaust system to the vehicle. In the first part is performed modal analysis, which is compared to experimentally measured data. Modal analysis of the complete exhaust system is made with focusing on the influence of temperature of the exhaust system. There is also performed an analysis of noise transmission from exhaust system to the car cockpit.

In search for quieter engines there is a need for a better understanding of the acoustic properties of engine intake and exhaust system components. Besides mufflers which have the purpose of reducing pressure pulses originating from the internal combustion (IC) engine, there are many components in a modern car exhaust and intake system, e.g., air-filters, coolers, catalytic converters, particulate filters - all having an effect on the pressure pulses or sound field in the system. In this work the focus is on the turbocharged IC-engine where both, sound scattering (reflection and transmission) and sound generation from automotive turbochargers are studied. In addition, sound reflection from an open ended pipe, such as the tailpipe of an IC-engine exhaust is investigated.             Accurate and efficient methods to fully characterize turbochargers by measuring the acoustic two-port have been developed.  Compared to earlier work, a number of modifications are suggested for improving the quality of the results. A study on three different automotive turbochargers is also presented, including data for sound scattering for both the compressor and turbine. The results for the transmission of sound, which is of interest for the ability of a turbocharger to reduce noise coming from the engine, is plotted for all tested cases against a dimensionless frequency scale (Helmholtz-number). This makes it possible to generalize the result in order to draw conclusions about the behavior for any turbocharger.              The sound generation was also studied and three different methods to estimate the sound power are suggested. The methods were used to investigate sound generation at different operating points and identify source mechanisms for a turbocharger compressor.             An accurate method for measuring the reflection of plane acoustic waves from a pipe termination in a duct with hot gas flow has been developed and tested. Representing the acoustical conditions at an exhaust tail-pipe, the data obtained is important for effective modeling of exhaust systems. The experimental results of the reflection coefficient were compared with Munt`s theory on flow duct openings. The measurements were carried out for air jet velocities up to Mach 0.4 and for flow temperatures up to 100°C in order to study temperature effects on the reflection properties. It was concluded, that the experimental results agree well with the Munt theory.

Sverige och EU har man som mål att halvera energianvändningen fram till 2050 och det arbetet måste starta nu. Det är 15 miljoner kvm byggyta som måste halvera sin energianvändning varje år och i 40 år framåt. Redan idag är 70 % av alla hus till 2050 byggda, vilket innebär att även om vi skulle bygga passivhus fram tills dess skulle det inte räcka för att nå målet. Det är alltså en stor utmaning att halvera energianvändningen till 2050. En jämförelsestudie har genomförts mellan två värmeåtervinningssystem. Frånluftssystem med värmeåtervinning och från- och tilluftssystem med värmeåtervinning. Med hjälp av resultaten av genomförda projekt från två olika fastighetsägare har slutsatser kunnat dras. Slutsatserna är underlag till parametrar som påverkar valet av värmeåtervinningssystem. För att veta vad som är lämpligt har intervjuer genomförts med sakkunniga personer, fastighetsbolags energiansvariga, leverantörer samt konsulter.  Utifrån de intervjuer som genomfördes har uppfattning uppkommit om att alla har olika synpunkter och värderingar vid val av ventilationssystem samt att det är många faktorer som spelar roll vid val av ventilationssystem. I rapporten intervjuas två av Stockholms största fastighetsbolag: Stockholms Hem och Svenska Bostäder. Både fastighetsbolagen genomförde ett ”pilotprojekt” där man utfört prövning och utveckling av nya tekniska system. Syftet med pilotprojektet var att göra ett underlag för framtida projekt. De båda fastighetsbolagens val av ventilationssystem var situationsanpassade. Stockholms hem valde att använda sig av FX pga. affärsmässiga skäl samt utformningen av fastigheterna. Svenska Bostäder utförde större projekt där man totalrenoverade fastigheter, och därmed använde sig av FTX pga. klimatmässiga skäl. / Sweden has alongside with EU set a up goal to reduce the usage of energy with 50 % by 2050, a goal that Sweden to start working towards today/now. It is 15 million square meters of building space that needs to decrease its use of energy every year in 40 years. 70 % of all the buildings that are meant to be build in Sweden by 2050 are already made today, this strongly implicates that we will not be able to reach the goal even if the remaining 30% are strictly passive houses. It will be a demanding challenge to reduce the energy usage to half of its current state. A comparison has been made between two studies on waste heat recovery system, specifically the exhaust system with heat recovery and exhaust and supply air with heat recovery. A conclusion has be drawn from results of the two studies that were made. The conclusions are the main source for the parameters affecting the choice of waste heat recovery system. In order to know what was suitable for the goal, Interviews were made with experienced staffs, a property company, energy managers, contractors and consultants. Based on the interviews made, we concluded that all the parties had different views and standards when selecting a ventilation system, since there are many factors that play major roles in different areas. “Stockholms Hem” and “Svenska Bostäder” which is Two of Stockholm’s leading real estate companies were interviewed for this report. The two companies conducted a “pilot project” where they performed the investigation and development of new established technical systems. The pilot project was meant to be a base for future projects. The company’s choice of ventilation system was adapted after the situation. “Stockholms hem” chaose to use the an exhaust air heat pump due to business related reason and the design of the building, whereas “Svenska bostäder “ implemented major projects that renovated properties thus they chose an exhaust supply air heat exchange system due to climate reasons.

La sonorité de l’échappement joue un rôle significatif sur le confort acoustique des occupants, ainsi que sur le caractère du véhicule. L’étude proposée porte sur la problématique industrielle suivante : « Description et quantification de la transmission du son entre la bouche d’échappement et l’intérieur du véhicule ». Physiquement la transmission sonore entre l’échappement et l’intérieur du véhicule s’effectue en trois étapes : Propagation des ondes sonores de la canule à la surface extérieure du véhicule et conversion en énergie vibratoire (1) ; Le bruit structurel se propage de la peau extérieure du véhicule à l’habillage intérieur (2) ; La surface intérieure du véhicule rayonne de l’énergie dans l’air à l’intérieur (3). Dans l’état de l’art proposé, la méthode de sous-structuration vibro-acoustique Patch Transfer Functions (PTF) est considérée comme une alternative viable à la problématique proposée. Cependant, avant d’appliquer la méthode sur un véhicule complet, la problématique suivante devait être résolue : « Caractérisation expérimentale d’un sous-système par des mesures sur un système couplé ». Ce manuscrit propose une méthode originale pour mesurer des fonctions de transfert d’un système découplé, sur la base de la réponse d’un système couplé. En raison de la nature mal posée du problème inverse, une méthode originale de régularisation a été proposée. La méthode a été validée pas des essais numériques, puis par un test physique. / Exhaust noise has a significant impact on acoustic comfort and the sound identity of a vehicle brand. The present study focuses on the: “Description and quantification of the sound transmission from the exhaust outlet into the interior of a vehicle”. Physically the noise propagation from the exhaust pipe to the cabin consists of three steps: The sound waves propagate through the air from the exhaust outlet to the external skin of the vehicle (1); the external skin vibrates and transmits its vibration to the internal skin (2); the internal skin radiates sound in the passengers’ cabin (3). The Patch Transfer Functions method, which is based on the framework of dynamic substructuring, allows for the consideration of this complex problem as simpler subproblems that consist of subsystem interactions. Yet the application of the method to a full vehicle requires addressing the problem: “Characterization of Patch Transfer Functions of a subsystem by means of measurement on a coupled system”. This dissertation presents an original inverse method for the measurement of Patch Transfer Functions. In industrial structures, this in-situ characterization is generally the only possible measurement method. Yet, due to the ill posed nature of the problem, the inversion process is difficult. An original regularization method is proposed. The method is tested through numerical simulations, and is validated with an experimental setup.

A number of experimental and theoretical studies, performed in the field of technical flow duct acoustics are presented in this thesis. The acoustical methods treated are implemented on turbocharged IC-engines and engine gas exchange system components. A new method based on the well-known two-load technique has been developed. The method was applied to characterise the source data of various piston-engines with non-linear behaviour including a 6 cylinder turbo-charged truck diesel engine. The source characterisation results were compared to the results obtained using the linear two-load technique. It was demonstrated that the new non-linear multi-load technique gives improved results when the source is slightly non-linear. The use of active one-port models has been tested to characterize an air terminal device (ATD) as a source of flow generated noise. In order to predict the noise generation at different operating points of the device a scaling law was derived and verified. In the experimentally derived scaling law a flow speed dependence of 3 was found for the narrow band spectra, corresponding to a dipole-like behavior of the source in the plane wave range. The proposed technique was validated successfully and the results indicated a good prediction of in-duct sound generation by the air terminal device. Sound reflection from hot flow duct openings has been investigated experimentally. The reflection coefficient was measured for flow temperatures up to 500 ºC and jet velocities up to 108m/s. The results have been compared with famous Munt’s theory. It was concluded that at low Mach number and Helmholz number cases the results agree well with the Munt’s model. This was the first experimental validation of the theory for hot flow conditions. Experimental procedures to determine the sound transmission through automotive turbo-charger compressors were developed and described in detail. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed. Current wave action models developed in CMT for computation of the gas exchange processes in I.C. engines have been implemented to determine the acoustic wave transmission through the turbo- compressor. The models are validated with the experimental data and the results are presented for different operating conditions of a Volvo passenger car turbo-compressor. / QC 20100809