LED-assisted ignition for lean-burn IC engines

We plan to propose an LED-assisted ignition technique for lean-burn internal combustion engines. It has been known for decades that lean fuel/air mixture is difficult to ignite than the stoichiometric mixture. The proposed technology is based on enhancing chemical reactivity of fuel-air mixtures by non-equilibrium optical pumping of reaction intermediates from ground state to the electronic excited states. Due to high reactivity at the electronic excited state, we anticipate that the conventional spark plug will be able to initiate the ignition at fuel-air ratios that are impossible to ignite without the optical augmentation. We will take advantage of the recently rapid development in commercial high-power LEDs in the ultra-violet (UV) range and construct high-power LED arrays to specifically excite optical transitions for combustion intermediates such as OH radicals. Compared with the sophisticated ignition systems such as laser, microwave, or plasma jet, the LED-assisted lean-burn ignition is much simple, inexpensive, and does not require a complicated supporting system. The objective of the Phase I study is to provide proof-of-concept for the proposed technique. We will at first demonstrate the feasibility of the LED-assisted ignition by measuring ignition delay of a variety of fuel-air mixtures with a shock tube instrument. Ignition delays will be determined by pressure monitor and chemiluminescence measurements with or without LED illumination. To understand the experimental results and offer kinetic insight into further investigation, numerical simulation with chemical kinetic modeling will also be performed in the Phase I study. We will then design and construct a LED-assisted ignition device for an Aerodynes Miniature Internal Combustion Engine (MICE) generator for portable electrical power, and evaluate the performance of this device via advanced optical diagnostic tools and emission measurements. The tasks of the Phase I program will be: 1) Measure ignition delays for the n-heptane/air and methane/air mixtures at different mixing ratios 2) Perform chemical kinetic modeling for comparison with the shock-tube measurements 3) Design and build an LED-assisted ignition device for a 300W Aerodynes MICE generator 4) Demonstrate the LED-assisted ignition on the MICE device . For the Phase II study, we plan to collaborate with Professor Wai Chengs research group at Massachusetts Institute of Technology (MIT). A compact LED-assisted ignition device for a gasoline IC engine will be developed and evaluated at MIT engine test facility. Technical issues related to the application of this device in IC engines, such as timing control of LED during engine cycles, introducing the LED light close to spark plug, and cleaning optical window inside combustion chamber, will be carefully investigated in the Phase II study.