Laser ignition is a potential ignition tectmotogy to achieve reliable lean burn ignition in high brake mean effective pressure (BMEP) internal combustion engities. The technology has the potential to inctease btake thertnat ejficiency and t educe exhaust emissions. This submission reports on engine testing of a Catetpittar G35I6C stationary natural gas fueled engine with thtee types of ignition apptoaches; (i) nonfueted etecttic ptechamber ptug with etecttodes at the base of the prechamber, (ii) nonftteled laser ptechatnber plug with laser spark in the middle of the prechamber, atid (Hi) open ctiatnber plug with laser spark in the main chamber. In the second configuration, a stock twtifueted prechamber plug was modified to incorporate a sapphire window and a focusing lens to fot m a laser ptechamber plug. A 1064 nm Q-switched Nd;YAG laser was used to cteate la.ser .ipatks. For these tests, a single cylinder of the engine was tetrofitted with the taser plug while the remaining cylinders were tun with cottventional electric ignition system at basetine ignition titning of 24 deg befóte top dead center (BTDC). The petformances of the thtee plugs were compated in terms of itidicated mean effective pre.ssures (IMFP), mass burn fraction duration attd coefficient of variation (COV) oflMEP, and COV of peak pres,sure location. Test data show compatable petformance between electric and la.ser ptechatnber plugs, albeit with a lower degree of variability in engine s petformance for electric prectiamber ptug compated to the laser prechamber plug. The open chamber plug exhibited poorer variability in engine perfotmanee. All results ate di.sctissed in the cotite.xt of prechctmber atid engitte fluid mechatiics.
Multimode silica step-index optical fibers are examined for use in planar laser-induced fluorescence (PLIF) for combustion diagnostics using ultraviolet (UV) laser sources. The multimode step-index fibers are characterized at UV wavelengths by examining their energy damage thresholds and solarization performance. The beam quality achievable with large clad step-index multimode fibers is also studied. Emphasis is placed on simultaneously achieving high output energy and beam quality (low output M(2)). The use of multimode fibers to deliver UV pulses at 283 nm for PLIF measurements of OH radicals in a Hencken burner is demonstrated. The fiber delivery capability of UV light will benefit combustion diagnostics in hostile environments, such as augmentor and combustor rigs.
Laser ignition is a potential ignition technology to achieve reliable lean burn ignition in high brake mean effective pressure (BMEP) internal combustion engines. The technology has the potential to increase brake thermal efficiency and reduce exhaust emissions. This submission reports on engine testing of a Caterpillar G3516C stationary natural gas fueled engine with three types of ignition approaches: i) non-fueled electric prechamber plug with electrodes at the base of the prechamber (i.e., conventional ignition), ii) non-fueled laser prechamber plug with laser spark in the middle of the prechamber, and iii) open chamber plug with laser spark in the main chamber. In the second configuration, a stock non-fueled prechamber plug was modified to incorporate a sapphire window and a focusing lens to form a laser prechamber plug. A 1064 nm Q-switched Nd:YAG laser was used to create laser sparks. For these tests, a single cylinder of the engine was retrofitted with the laser plug while the remaining cylinders were run with conventional electric ignition system at baseline ignition timing of 24 degree before Top Dead Center (BTDC). The performances of the three plugs were compared in terms of Indicated Mean Effective Pressures (IMEP), Mass Burn Fraction Duration and Coefficient of Variation (COV) of IMEP, and COV of Peak Pressure Location. Test data show comparable performance between electric and laser prechamber plugs, albeit with a lower degree of variability in engine’s performance for electric prechamber plug compared to the laser prechamber plug. The open chamber plug exhibited poorer variability in engine performance. All results are discussed in the context of prechamber and engine fluid mechanics.
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