Experimental and Computational Investigations of Spark Ignition Engine Performance

Abstract

This paper describes a comprehensive experimental and numerical project implemented in a third-year applied thermodynamics course. In the project, students experimentally investigate the performance of a single-cylinder spark ignition (SI) and then develop a numerical model for the same engine which accounts for non-isentropic and finite-duration heat release effects. Using the experimental data and numerical model, students investigate the impact of compression ratio and spark timing on a variety of engine performance parameters such as peak pressure, power, and efficiency. The project has some unique learning outcomes. First, students are able to compare the performance of a real SI engine to the Otto cycle model studied in class. Second, they gain experience applying concepts from thermodynamics, heat transfer and numerical methods to develop a realistic numerical model for the actual engine. In the development of the model, the constants needed for closure of the model and system of equations must be obtained empirically from the experimental data. This experience provides students with valuable insight into the inner workings of commercial simulation software packages where closure models are often developed from experimental data. The paper concludes with suggestions of additional tasks and refinements that can be incorporated into this project to capture real-world effects such as heat losses during the combustion process. In addition, challenges in the implementation of this project and hurdles encountered by students are also discussed along with some suggestions to counter these issues.