Activation and Control of Autoignition in HCCI Engines Using Volumetrically-Distributed Ignition of As-Produced Single-Walled Carbon Nanotubes

The discovery that nanostructured materials exhibit properties different than their bulk materials provided many exciting opportunities with technological applications. One such opportunity is the observed ignition of the single-walled carbon nanotubes (SWCNTs) with an ordinary camera flash. In this paper, light-activated ignition characteristics of the as-produced SWCNTs (50 wt% iron nanoparticle content) with a camera flash are presented. The primary objective of this work is to use nanostructured materials as means for distributed (or volumetric) ignition and improved combustion in propulsion systems. Important examples are homogeneous-charged compression ignition (HCCI) engines, liquid rocket fuel sprays, and enhanced flame stabilization in gas turbine engines. The idea was originally proposed by the author in April 2003 and the first patent filed in July 2004 following a series of initial investigations. Based on these and additional tests, this new ignition method is now considered as a potential enabling technology for volumetric and distributed ignition of liquid fuel sprays or gaseous fuel-air mixtures with the lowest incident power intensity possible. This means remote and spatial ignition within any desired and adjustable region defined by the shape of the light from a pulsed light source. Average intensities in between 10 to 150 W/cm₂ are required for ignition of SWCNTs. This is a factor of 80 less than cases where lasers (pulsed and continuous wave (cw)) are used in coal particles. Results acquired in a premixed gaseous fuel-air mixture in a cylindrical combustion chamber, comparing a spark plug with the light-activated distributed ignition of SWCNTs, confirmed the patented concept and showed a truly on-demand activation of the autoignition process for HCCI engine applications. Faster fuel-air mixture burn rate reaching up to a factor of 3 has been demonstrated for distributed ignition under lean mixture as compared with a conventional spark ignition system.