Optimal Knock Sensor Spatial Locations of In-line Combustion Engines : A Case Study of Scania Engines

Sammanfattning: In recent years, there has been a growing interest in utilizing knock sensors as a diagnostic tool for providing valuable insights into the combustion process. These sensors have demonstrated their potential to offer information regarding crucial parameters such as the start of combustion, heat release rate, misfire events, and valve events. Furthermore, knock sensors can also serve as virtual sensors for cylinder pressure estimation.  The placement of knock sensors plays a crucial role in ensuring their precision in identifying and capturing the target vibrations. Unwanted noise from various sources, such as accessory drives, can interfere with the sensor signal. Therefore, careful consideration must be given to the spatial location of the knock sensor to accurately observe the targeted vibrations while mitigating the impact of noise vibrations.  This thesis presents an experimental study conducted on six cylinder in-line combustion engines provided by Scania, with the aim of determining the optimal locations for mounting knock sensors on the engine. The primary objective is to effectively detect combustion, misfires, and valve events. Through comprehensive testing and analysis, this thesis seeks to identify the most suitable positions for knock sensor installation to maximize the accuracy and reliability of the observed data.  The study found that misfire events can be effectivley detected in all cylinders using two sensors. The best locations for misfire detection were on the intake manifold and the cold side of the cylinder walls. For valve event detection, optimal positions were identified on the engine top, cylinder head, and intake manifold. Combustion detection was most successful on the cold side of the cylinder head, specifically near cylinder 6. These findings are limited to the tested conditions and require careful interpretation.