1-hexene autoignition control by prior reaction with ozone

• 1-hexene was reacted with ozone to produce a fuel of increased ignition quality.
• Varying the fraction of 1-hexene reacted with ozone was used to control autoignition.
• Chemical analysis suggested ozonide formation in the fuel.
• Chemical kinetic calculations suggested ozonide was responsible for advancing ignition.

The autoignition timing of 1-hexene was controlled in a Homogeneous Charge Compression Ignition (HCCI) engine by reacting the fuel with ozone-containing air prior to its combustion. The experiments were conducted in a single cylinder research engine instrumented with a cylinder pressure sensor. The fuel was chemically characterised using Nuclear Magnetic Resonance (NMR) spectroscopy before and after its reaction with ozone. The NMR analyses showed that this preliminary reaction produced several oxygenated products within the fuel, and was likely to have resulted in the formation of ozonide molecules having a peroxidic structure with several oxygen molecules in series. To understand how this would affect the ignition reactions, the ignition process was modelled numerically using a single-zone chemical kinetic reactor model. The modelling suggested that peroxide molecules decomposed during the compression of the reactants in the engine and advanced ignition timing by promoting early decomposition of the fuel through the formation of radicals.