Flame Stability and Geometric Analysis of Ultrasonically Excited LJIC Combustion

Historically, liquid jet in crossflow systems have been used in applications where relatively large amounts of liquid must be rapidly entrained into rapid air streams. Often, such applications are directly concerned with the stability and flame characteristics fuel mixtures injected into combustion engines. The demands for injection systems to provide larger amounts of fuel, which break up in significantly smaller time scales, and have less variability throughout flow conditions have increased as engine technology has become more advanced. The present work leverages previous observations that solid obstructions in the flow path of the liquid fuel can assist with each of those goals. More recently, this technology has advanced with the addition of ultrasonic excitation of the liquid jet through the inclusion of piezoelectric devices in the obstruction itself. The present work seeks to investigate the effects that ultrasonic excitation has on flame characteristics, including resistance to lean blowout and apparent flame speed. Investigation of the effects has shown significant positive benefit to the use of ultrasonic excitation on flame stability, with reductions in minimum stable global equivalence ratio as high as 20%, with a corresponding increase in effective flame speed as measured from the measured flame brush angle.