Electrical Waveform Analysis of Spark Discharge for Monitoring Conditions Inside Prototype Prechambers

Using renewable fuels like hydrogen in internal combustion engines requires new combustion strategies and ignition systems like pre-chamber sparkplugs. This necessitates novel measurement and monitoring techniques to gain insights into the phenomena arising from the use of new fuels and components. For understanding the phenomenon of pre-chamber ignition, it is important to observe how sparks behave inside them. The spark-elongation under certain conditions inside a particular pre-chamber, its location at a given time during discharge, and the flow conditions during spark discharge are all significant factors in gaining insight into this phenomenon. However, such information is difficult to obtain from inside a pre-chamber due to the difficulty of gaining optical access. In such cases, the electrical waveform analysis could prove useful. During this study, the electrical parameters are used to calculate the spark length, providing information about the igniting volume inside a pre-chamber during the spark discharge. This was achieved by modifying the Kim and Anderson equation to meet the specific requirements of the study, which involved correlating it to the optical spark length obtained in a spark wind tunnel test bed under conditions similar to those in an engine. This modified equation was then used to calculate the spark length inside different prototype pre-chambers and sparkplug to compare and contrast the conditions. Information about the flow conditions inside the pre-chamber was also obtained from the spark length, given that the surrounding flow influences spark elongation. This methodology was first validated in the spark wind tunnel test bed before pre-chambers were tested in the engine. Testing different prototype pre-chambers provided valuable insights into the flow conditions, demonstrating the technique's effectiveness in understanding the factors that make a pre-chamber design suitable for a particular fuel and set of conditions, and why it is less effective in other situations. This study proves that electrical waveform analysis is a key tool for monitoring the performance of prototype pre-chambers designed for renewable fuels, such as hydrogen.