Date of Award


Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeff Naber

Advisor 2

Scott Miers

Committee Member 1

David Shonnard

Committee Member 2

Thomas Wallner


The 2007 U.S. Renewable Fuel Standard (RFS2) requires an increase in the use of advanced biofuels up to 36 billion gallons by 2022. Higher carbon number alcohols, in addition to cellulosic ethanol and synthetic biofuels, could be used to meet this demand while adhering to the RFS2 corn-based ethanol limitation. Alcohols of carbon numbers 2 through 8 are chosen based on their chemical and engine-related properties.

Blend comparison metrics are developed from automotive industry trends, consumer expectations, U.S. fuel legislation, and engine requirements. The metrics are then used to create scenarios by which to compare higher alcohol fuel blends to traditional ethanol blends. Each scenario details an overall objective and identifies chemical and engine-related properties that are crucial to meeting that objective as fuel criteria.

Fuel blend property prediction methods are adopted from literature and used to calculate both linear and non-linear properties of multi-component blends. Possible combinations of eight alcohols mixed with a gasoline blendstock are calculated and the properties of the theoretical fuel blends are predicted. Blends that meet all of a scenario’s criteria are identified as suitable blends.

Blends of higher carbon number alcohols with gasoline blendstock are identified as optimal blends for each scenario if they meet all of the scenario’s criteria and maximize either energy content, knock resistance, or petroleum displacement. Optimal blends are tested in a spark-ignition engine. The effect of higher carbon number alcohols as a fuel component on engine performance and emissions is examined.

Results suggest that combustion properties of blends of alcohols with carbon numbers from two to six are similar to those of the reference fuel at low and medium engine loads. Properties of blends of alcohols with carbon numbers from two to four are similar to those of the reference fuel even at high loads. However, due to their reduced knock resistance, the suitability of longer chain alcohols, specifically C5 and longer, as blending agents at increased levels is questionable.