Optimum Probe Design for Precise TDC Measurement Using a Microwave Technique

The microwave method has advantages, such as a high degree of precision and dynamic measurement capability, for measuring TDC (Top Dead Center) in an engine. However, there are marked discrepancies between the calculation from a simplified model and experiments. Especially in the indirect-injection diesel engine, the concept of this method is not generally understood and the probe design for this method has not been established. It has been experimentally clarified that these discrepancies result mainly from the structure of the main chamber in the indirect-injection diesel engine and the measuring method of the sharpness of a microwave resonance. An optimum probe design for measuring TDC is proposed. A simple laboratory engine simulator is also proposed to simplify determination of the design parameters.