Date of Award

Fall 2021

Document Type

Open Access Thesis

Department

Mechanical Engineering

First Advisor

Sang Hee Won

Abstract

Combustion has been the primary source for energy production, whether it be from coal, oil, or natural gas, for a very long time. With increasing population and therefore an increased demand for energy, efficiency is becoming a concern. In order to increase efficiency, engines have been downsized and compression ratios have been increased. In doing so, problems have arisen such as knock and low speed pre-ignition. To better understand these problems, an investigation into how fuels ignite at higher pressures is necessary. Real fuels are comprised of multiple components that exhibit significant variations in their own physical and chemical characteristics. Examining these characteristics of real fuels in real world applications has proved to be quite challenging due to the complexity associated with multi-component and multiphase combustion processes. The creation of a novel device to mimic the behavior of reciprocating engines is necessary to gather a fundamental understanding of these fuel properties and their impacts on multiphase combustion processes. The objective of this study is to develop a well-defined experimental platform that can provide high-quality measurements for both gas- and multi-phase ignition processes. Accordingly, a rapid compression expansion machine (RCEM) has been developed and its performance has been comprehensively evaluated. The RCEM is composed of a pneumatically driven actuator, cam, and combustion chamber. The actuator pneumatically pushes a cam that guides the piston to compress the combustion chamber. Pressure time-history profiles have been measured and used to evaluate the compression time for characterizing the polytropic compression behaviors. Considering the relevance to the gasoline fuels, n-Heptane has been used as the primary fuel for this research, which represents the lighter components within an ethanol free fuel. This study summarizes technical challenges in developing a well-defined RCEM, along with experimentally observed ignition behaviors of both gas-phase and multi-phase mixtures.

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