Actuation efficiency of nanosecond repetitively pulsed discharges for plasma-assisted swirl flames at pressures up to 3 bar

Abstract

This study analyzes different strategies of plasma actuation of premixed swirl flames at pressures up to 3 bar. A wide range of applied voltages and pulse repetition frequencies (PRF) is considered, resulting in different combinations of nanosecond repetitively pulsed (NRP) discharge regimes, NRP glow and NRP spark discharges. Electrical characterization of the discharges is performed, measuring voltage and current, and deposited energy and power are evaluated. The effectiveness of the plasma actuation is assessed through images of OH* chemiluminescence from the flame. From these images, the distance of the center of gravity of the flame to the burner plate is evaluated, with and without plasma actuation. The results show that strategies which involve a high percentage of NRP sparks are effective at improving flame anchoring at atmospheric pressure, while they are detrimental

Non-equilibrium plasma for ignition and combustion enhancement

“…On the other hand, if the shock waves are too strong, they may destabilize the combustion. This was recently discussed in [180], where at pressures above 2 bar, it was found that spark NRPD (with strong gas heating and shock wave generation) were less efficient than glow NRPD (promoting a chemical effect), for flame anchoring. 6 Plasma-assisted detonation Detonation refers to a supersonic regime of combustion.…”

“…However, the effect of sub-breakdown electric fields on flames (e.g., [155][156][157][158][159]161]) is also commonly considered as a PAC process. The end goals of PAC studies can be grouped into three categories: (1) increase the flammability limits [47,112,[164][165][166]171], (2) stabilize the combustion [172][173][174][175][176][177]179,180], and (3) enhance the burning properties (e.g., burning velocity, soot or pollutant emis-sions. .…”

“…For all listed condition, the PAC strategies have been successful in enhancing the combustion. Even thought not always quantified, the electric power applied was in the range of the percent of the thermal power released by combustion (see for example [166,172,180]). Note that this electric power does not account for the efficiency of the electric source, as it is usually measured close to the electrodes.…”

Investigation of the effects of passive pre-chamber nozzle pattern and ignition system on engine performance and emissions

“…Overly strong distortion, however, could result in localized extinction -particularly at leaner mixtures. 51 Faster flame development should benefit PC ignition as a greater fraction of the fuel-air mixture was consumed within the PC volume before it can be pushed out through the nozzles due to pressure buildup. Moreover, the benefit should be more pronounced with larger internal PC volumes as the effect of wall quench became less pronounced.…”

Numerical analysis of turbulent flame enhancement by nanosecond repetitively pulsed plasma discharges

“…An emerging solution to enable flame stabilization, suitable to a wide range of combustion applications, is to locally generate a plasma [2,3]. Among the various possible types of discharges to enhance combustion [4,5], the Nanosecond Repetitively Pulsed (NRP) discharges [6] succeeded to stabilize ultra-lean premixed flames on several laboratory-scale hydrocarbon-air flames [6,7] but also in test rigs representative of a gas turbine environment at atmospheric [8,9] and high pressure [10,11]. This technique is very efficient because the energy consumption of the plasma is typically less than 1% of the power released by the flame.…”