Multi-Walled Carbon Nanotubes (MWCNTs) bonded with Ferrocene particles as ignition agents for air-fuel mixtures

Abstract

The potentials and characteristics of a new ignition system for air-fuel mixtures are discussed. This ignition method (referred to as photo-thermal ignition) is based on light exposure of Multi-Walled Carbon Nanotubes (MWCNTs), bonded with other nano-Structured Materials (nSMs), (collectively referred here as “nanoignition agent”), using a low-consumption camera flash. Here, Ferrocene, an organometallic compound, was used as the nSMs.Results from, and benefits of, this new ignition method are compared with a conventional spark-plug-initiated ignition used in automotive engines.The main objective of this research is to demonstrate ignition feasibility of mixtures of both gaseous and liquid fuels with air under high pressures using the photo-thermal ignition (PTI) phenomenon. Specifically, the ignition and subsequent combustion characteristics of gaseous air-fuel mixtures at different air-fuel ratios were investigated by means of light exposures of nano-ignition agents (nIAs) after they are mixed with air-fuel mixtures.Analysis of the acquired data showed that for the range of air-fuel ratios tested, the photo-thermal ignition with a flash lamp resulted in a higher peak chamber pressure when compared to those obtained with a conventional spark ignition system. Heat release rate analysis showed that shorter ignition delays and total combustion durations for the Photo-thermal ignition are achieved. Comparative percent reduction of these values for photo-ignition ranges from 20% to 50% for LPG and methane, whereas values up to 70% were observed for the hydrogen. The positive impact of the photo-thermal ignition appears to be primarily at the ignition delay period of the combustion. With liquid fuels, photo-thermal ignition was capable to ignite mixtures as lean as a relative air-fuel ratio of 2.7 while the spark ignition was incapable to initiate combustion. Additionally, tests with the liquid gasoline injection highlighted that the combustion process with a higher “residence mixing time” exhibited higher peak pressures and shorter ignition delay times.High-speed camera images were used to capture images of the light emission during the combustion process in visible range, allowing investigation of the ignition processes. In particular, the results showed that the photo-thermal ignition process of the air-fuel mixtures with nano-ignition agents led to a spatially-distributed ignition followed by a faster consumption of the air-fuel mixture with no evidence of any discernible flame front formation or propagation.