Ionization Current Sensing

SUMMARY

Ion current measurements give information on the combustion in the cylinders of an internal combustion engine in run time, cycle by cycle. Ion sense has been used in gasoline engines for many years for detection of knock and misfire, combustion stability and for air to fuel ratio estimation. However, the use of ion sense in industrial gas engines has been limited, despite the potential of ion sense.

The objective with the project is to investigate which combustion process information that can be retrieved using ion sense applied to industrial lean burn engines using pre-chambers for the ignition in which case the spark plug is encapsulated in the pre-chamber.

Experiments show that ion current measured in the pre-chamber can successfully be used to retrieve information from the in-cylinder combustion process. It is possible to detect misfire and to some extent knock. It is also possible to optimize the ignition and hence minimize emissions and optimize the performance by using the ion current measured in the prechamber.

A statistical signal processing approach to use more than one ion current feature in the estimation of combustion parameters was evaluated on a heavy duty gas engine. By using more than one feature the performance of in cylinder air to fuel ratio estimation was improved.