The Effect of a TiO ₂ Coating with the Addition of H ₂ Gas on Emissions of a Small Spark-Ignition Engine 2014-32-0034

This study looks at the application of a titanium dioxide (TiO₂) catalytic nanoparticle suspension to the surface of the combustion chamber as a coating, as well as the addition of hydrogen gas to a four-stroke spark-ignited carbureted engine as a possible technique for lowering engine-out emissions. The experiments were conducted on two identical Generac gasoline powered generators using two, four and six halogen work lamps to load the engine. One generator was used as a control and the second had key components of the combustion chamber coated with the catalytic suspension. In addition to the coating, both engines were fed a hydrogen and oxygen gas mixture and tested at low, medium and high loads.

Using an unmodified engine as a control set, the following three conditions were tested and compared: addition of hydrogen only, addition of coating only, and addition of hydrogen to the coated engine. Operating the engines on standard gasoline in a laboratory, emission gases were transferred via a heated line to be analyzed by an FTIR. Overall, the experimental results showed that at medium load the TiO₂ coating provided up to a 18% reduction of hydrocarbons (HC) and up to 20% reduction of oxides of nitrogen (NO_X) depending on the respective load. At the highest load, the addition of hydrogen to the TiO₂ coated engine resulted in comparable carbon monoxide emissions relative to the control engine while also providing a reduction of 5-20% of both NO_X and HC.