Date of Thesis

12-17-2015

Thesis Type

Masters Thesis (Bucknell Access Only)

Degree Type

Master of Science in Mechanical Engineering

First Advisor

Peter Stryker

Abstract

Currently there is increased interest in knock testing aviation reciprocating engines as engine manufacturers, fuel producers, and government certification bodies support the transition to unleaded fuels mandated by the Environmental Protection Agency (EPA). However, no industry standard knock detection methodology exists that can be used to unite these activities. Therefore, the American Society of Testing and Materials (ASTM) Referee knock detection method was compared to other cylinder pressure based knock detection methods commonly used outside of the aviation industry to further the effort of defining an aviation standard knock detection methodology. These methods were compared across the operating range of a Lycoming IO-360 engine using unleaded fuel. While the ASTM Referee method accurately detected knock in this particular general aviation engine, it exhibited sensitivity to non-knock related factors and therefore may not be suitable for engines of a different design. The other knock detection methods did not exhibit this sensitivity because a high pass filter was applied to the combustion pressure signal. For these reasons, the ASTM Referee method cannot be recommended as a standard knock detection methodology over the other knock detection methods. However, by adding a high pass filter to the ASTM Referee method, the sensitivity to non-knock related factors was eliminated. Lastly, several operational limits were identified that could independently reduce the occurrence of knock in this type of engine when using unleaded fuel.

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