A Novel Way to Enhance the Spark Plasma-Assisted Ignition for an Aero-Engine Under Low Pressure

Abstract

Finding a new ignition strategy for ignition enhancement in a lean-burn combustor has always been the biggest challenge for high-altitude, long-endurance unmanned aerial vehicles (UAVs). It is of great importance for the development of high-altitude, long-endurance aircraft to improve the secondary ignition ability of the aero-engine at high altitude where the ignition capability of the aero-engine igniter rapidly declines. An innovative ignition mode is therefore urgently needed. A novel plasma-assisted ignition method based on a multichannel discharge jet-enhanced spark (MDJS) was proposed in this study. Compared to the conventional spark igniter (SI), the arc discharge energy of the MDJS was increased by 13.6% at 0.12 bar and by 14.7% at 0.26 bar. Furthermore, the spark plasma penetration depth of the MDJS was increased by 49% and 103% at 0.12 bar and 0.26 bar, respectively. The CH* radicals showed that the MDJS obtained a larger initial spark kernel and reached a higher spark plasma penetration depth, which helped accelerate the burning velocity. Ignition tests in a model swirl combustor showed that the lean ignition limit was extended 24% from 0.034 to 0.026 at 25 m/s with 20 °C kerosene and 17% from 0.075 to 0.062 at 12 m/s with −30 °C kerosene maximally. The MDJS was a unique plasma-assisted ignition method, activated by the custom ignition power supply instead of a special power supply with an extra gas source. The objective of this study was to provide a novel multichannel discharge jet-enhanced spark ignition strategy which would help to increase the arc discharge energy, the spark plasma penetration depth and the activated area without changing the power supply system and to improve the safety and performance of aero-engines.

Numerical study on spark characteristics and evolution of plasma jet igniter

“…However, traditional igniters are difficult to meet the development needs of aero-engines to achieve stable ignition in the face of complex operating conditions due to the disadvantages of insufficient ignition energy, long excitation time and high brightness [1]. The novel aero-engine plasma igniter has developed thermal-effect-based spark plug ignition, chemical-effects-enhanced nanosecond pulsed plasma igniter [2,3], and the plasma spark jet igniter, which combines thermal, chemical and transport effects [4,5], is considered to be one of the most potential ignition methods. Compared with other igniters the plasma jet igniter has the advantages of high discharge energy, resistance to soot, and enhanced effect on combustion especially during ignition [6], thus it has been widely studied and applied in the aerospace field [7][8][9].…”

Multi-physics modeling of a spark plasma jet igniter

“…summarized as three categories [1]: the thermal effects, the chemical effects, and the transport effects. There exist several kinds of igniter types, for example, the thermal-effect-based spark plug igniter, the chemical-effects-enhanced nanosecond pulse plasma igniter [2,3], and the plasma spark jet igniter [4,5], etc.…”

An Optical Method to Characterize Streamer Variability and Streamer-to-Flame Transition for Radio-Frequency Corona Discharges

“…Currently, internal combustion engines need to comply with severe regulations concerning fuel economy and pollutant emission. Focusing on spark ignition (SI) engines, actual trends to obtain a cleaner and more efficient combustion are turbocharging, water injection, high exhaust gas recirculation (EGR) dilution, and lean combustion [1][2][3][4][5]. Because of all these features, it is critical to ensure an effective ignition able to start a robust combustion; conventional spark plugs show their limits [6,7] and an excessive cycle-to-cycle variability (CCV) is linked to the use of conventional igniters in these conditions.…”