This dissertation investigates the use of ethanol (EtOH), a potential major contributor to the fuel economy of the future. Ethanol can be derived from both bio-sources (such as corn) and petroleum (such as crude oil). Since EtOH can be a renewable fuel, it is important to fully investigate how Ethanol-fuelled engines perform. An investigation of EtOH and blends of EtOH and other additives is conducted using experimental and numerical techniques in order to paint a clearer picture of HCCI.

The importance of developing internal combustion engines which increase efficiency while decreasing harmful emissions is steadily increasing. An emergence of other energy-providing technologies such as fuel cells and solar power is also changing the landscape of the world's energy economy. However, the reliability and effectiveness of the internal combustion (IC) engine ensure that it will be a key player in our future. One way to further improve upon IC engines is to implement a combustion cycle known as Homogeneous Charge Compression Ignition (HCCI) which has the potential to reduce fuel consumption while simultaneously drastically reducing emission of nitric oxides (NOx) and particulate matter (PM), two products of combustion known to be harmful to human health and the environment.

HCCI is premixed, like spark ignition (SI) engines, and compression ignited, like a Diesel engine. The premixed fuel and air mixtures are unusually lean (stoichiometric ratios around 0.3) which results in low peak temperatures thus limiting the production of NOx. Since the fuel and air in the HCCI engine are premixed, there is no diffusion flame burning (as in a diesel engine) so particulate matter (PM) emissions are also quite low. The lean nature of the combustion process also leads to a decrease in PM since excess hydrocarbons (HC) are not present. This allows for high compression ratios and therefore higher engine efficiencies. Despite the benefits, the HCCI engine has two major obstacles to overcome: low power output (due to lean fuelling) and difficult control (due to the lack of in-cylinder spark plugs or fuel injectors). In addition, research towards understanding how different fuels perform under HCCI conditions is ongoing.