Investigation of exhaust chamber resonance for single-cylinder Formula SAE based engines

Abstract

Noise pollution is a factor that affects many people in their day to day lives. One of the more prevalent forms of noise is generated from passenger vehicles. With this in mind, vehicle manufacturers design and stringently test their mufflers that are bound for vehicles to ensure they provide the optimum characteristics needed to lower noise to suitable levels. In addition, these manufacturers continue to be proactive in researching improved methods of the design and build aspects of their vehicles, so it is common to see large production companies sponsoring development and racing events. One such event is the Formula SAE competition. This competition series is aimed at university students who design, build, and race their vehicle against other universities globally. Formula SAE is designed to provide students with valuable experience in a range of topics as both static and dynamic events occur and are judged. Consequently, the competition has evolved into more than just a racing series, it also includes business presentations, costing reports, and design judging. With more Formula SAE teams moving to single-cylinder engines, noise suppression is becoming an important issue from the exhaust noise characteristics of the large engines available today. As part of the competition, performance is judged based on set criteria for engine noise emissions at different engine speeds. Many teams struggle with this aspect of the competition, where a fail in this test commonly leads to crude forms of noise suppression being quickly added to the vehicle, which in turn usually results in lowering performance. If a team cannot pass the noise tests, then subsequently they are not allowed to enter any of the dynamic events. This thesis aims to compare theoretical results with measured values for different configurations of exhaust chambers. Inline exhaust chambers have been selected as the topic of interest due to the low-frequency exhaust characteristics of single-cylinder engines suiting the attenuation characteristics of this style of silencing device. The outcome of this research should provide figures and values for future Formula SAE teams to work with in their initial muffler and chamber design. By having this data available, selection of correct parameters will be a more straight-forward process and should assist in building a muffler that will be more assured of passing noise tests at competition.