Infrared-excitation for Improved Hydrocarbon Fuels' Combustion Efficiency - Concept and Demonstration 2010-01-1953
This paper describes an innovative concept of using infrared (IR) excitation to help hydrocarbon fuels burn in internal combustion engines at a possible higher efficiency. In organic chemistry, hydrocarbons are known to be infrared-active and absorb photons in 3 - 20 μm wavelengths causing molecular vibrations that lower activation barrier and thus increase oxidation rate during combustion. As a result, IR-excited fuel becomes more combustible in engine, helping getting closer to the ideal of constant-volume combustion for higher cycle efficiency. Prototype IR-emitters were made from selective transition metal oxides with a spectral luminance in 3 - 16 μm wavelengths. The IR-excitation effect was demonstrated by testing at an engine lab of MTU (DaimlerChrysler Off-Highway) on its 8V4000M63 model heavy-duty diesel engine for marine applications, showing a 6% reduction in fuel consumption. IR-excitation effect on flame structure was validated at Purdue University in a counterflow methane-air diffusion flame experiment, in which species concentrations for H₂, O₂, N₂, CH₄, CO, CO₂, C₂H₂, and C₂H₄ across the flame were measured using sampling and gas chromatography, while NO concentrations were measured using chemiluminescence analysis. The experimental results indicate the IR-excitation makes fuel burn faster and helps reduce fuel consumption by 6% and peak CO and NO emissions by about 15%. In addition, the results from an EPA FTP-75 test with the IR-emitters installed on a Ford F-350 light-duty diesel truck show a 5% improvement in fuel economy and about 38% reduction in both HC and CO emissions, while NOx and PM (particulate matter) emissions remain about the same, but the amount of SOF (soluble organic fraction) of diesel particulates emissions decrease by 10%. Though the preliminary tests seem to prove the concept, more evidence and works are required before a conclusion on the efficacy of IR-excitation can be made and commercial value realized.