Dynamic Model of Ignition Circuit for Spark Ignition Engines

Photo of Dyamon Jones, Emily Mrizek, Clayton Rogers, Orlando Salmon Students: Dyamon Jones, Emily Mrizek, Clayton Rogers, Orlando Salmon

Sponsor: The University of Texas Society of Automotive Engineers

Date: Spring 2012

Requirements:
The team was assigned the task of deriving transient response equations that model the ignition system. These equations must have low error, quick response, and recirculated exhaust range capability. The simulation should not exceed an error of 30% when compared to experimental data.

Problem:
Exhaust Gas Recirculation (EGR) is a technique to reduce automotive emissions. By perfecting the timing of the spark ignition, EGR can become more efficient, and NOx emissions can be decreased. This project will aid in taking the next steps to improving the ignition process. Principle transient response equations that model the ignition system must be determined and compared to real world data. These equations should be suitable for deployment in to the engine control unit.

Solution:
The model of the ignition circuit used to predict the transient response of the voltage and current in the spark gap, shown above, was used to derive the 2nd order differential equation for the ignition circuit. An EXCEL spreadsheet was created to solve this equation numerically to predict the energy deposition at the spark gap. The model allows a range of 0% to 25% of EGR and multiple hydrocarbon fuels, which increases its versatility. The model was benchmarked against previous experimental data, and was found to match within 26%.

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