Doctoral Dissertations

Date of Award

12-1997

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Mechanical Engineering

Major Professor

Jeffrey Hodgson

Committee Members

Robert Bodenheimer, Ke Nguyen, Masood Parang

Abstract

Alcohols (methanol and ethanol) have been identified as having the potential to improve air quality when used to replace conventional gasoline. This potential is primarily due to the different organic species that are emitted by alcohol-fueled engines. The use of "near neat" alcohols gives greater benefits than fuels containing lower levels of alcohol, but neat alcohols present a significant cold starting problem.

The primary objective of this study was to develop a rich combustor device which will extend the cold start range of alcohol fueled engines to -30°C while reducing cold start emissions. In support of this objective a software model was developed which includes the thermodynamic operation of the device as part of a vehicle, considering engine parameters, vehicle parameters, and driving cycle requirements.

The analytical portion of this project consists of developing the software model. To understand the design and operating variables of the combustor, the model simulates operation of the combustor. The model predicts the output composition using the shifting equilibrium approach. The model includes engine and vehicle parameter inputs which will allow the simulation of a driving cycle. Chemical kinetics are not considered.

The experimental portion of this project includes design, fabrication, and testing of the rich combustor device(s). The combustor design and installation takes into consideration all the criteria for proper vehicle operation such as requirements for actuating, shutdown, and phase-out of the device at different operating conditions. Because of the availability of cold temperature testing capabilities, including an engine dynamometer, and an engine identical to the engine in the test vehicle, the task of vehicle integration could logically be combined, to a great extent, with the testing and development of the prototype. We used the dynamometer driving the engine as a pump to test the combustor while the issues of fit, interfaces, and control were concurrently addressed. With this capability, a parallel approach allowed many of the problems associated with vehicle integration to be addressed early in the development of the combustor.

The development of the rich combustor was primarily targeted toward methanol; however, the device functions equally well using ethanol.

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