Microwave-generated plasma in air under standard conditions

Hagen, J.; Venot, Y.; Zhang, Ying; Wiesbeck, W.

doi:10.1109/27.940954

“…Table 1 shows the Q-factors for our cavity for all initiators. They are twice to ten times higher than in the previously cited microwave studies [18,21]. This results in less input power needed to reach the electric field for breakdown between the initiators.…”

Section: Cavity Quality Factors For All Initiatorsmentioning

confidence: 70%

“…As seen in the literature [21], we need an electric field density of the order of E = 777 to 1800 kV/m to reach breakdown in air at ambient conditions. With numerical simulation with an input power of 100 W, as seen in Figure 2, we checked that initiators (1) and (2) reach this order of magnitude in electric field density (V/m) in the gap between the initiators, prior to manufacturing of the cavity and the initiators.…”

Section: The Cavitymentioning

confidence: 99%

“…In the internal combustion engine community, the results of microwave plasma having positive effects on flame stability and decreasing the lean ignition limit, led to a wide range of studies on plasma assisted combustion and ignition [15,16]. In the automotive industry, the Quarter-Wave Coaxial Cavity Resonator (QWCCR) [12,[17][18][19][20][21] is a technology that has been extensively investigated as a potential new igniter. This coaxial line, short-circuited on one side and open on the other, is capable of creating a plasma at the tip of the inner conductor in air for pressures above 1 bar.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A versatile set-up to study plasma/microwave sources for liquid fuel ignition

Fragge

¹

,

Sokoloff

²

,

Rouzaud

³

et al. 2020

Eur. Phys. J. Appl. Phys.

View full text Add to dashboard Cite

Motivated by the high demand for an alternative, more reliable, high energy ignition source to facilitate the re-ignition of lean-burn combustion chambers which are necessary to reduce pollutant emissions, a new set-up has been designed to study plasma / microwave sources. The use of a waveguide-based resonant cavity leads to very low power plasma ignition. An example in this paper shows that a plasma at atmospheric pressure can be maintained with less than 2 W input power. Such a performance is possible using the large variety of possible adjustments (resonance frequency, different kind of initiators,…) that this versatile set-up offers. To illustrate the wide range of possible studies, another example is given and discussed : Minimum ignition energy for an ethanol droplet stream with aluminum and stainless steel initiators. The results show that the initiator material and its surface quality have an influence on the minimum ignition energy, especially for large gaps. Depending on the gap size we can get down to under 10 W entering the cavity to ignite the droplet stream.

show abstract

“…Although apparently independent from the research performed at West Virginia University, 2.45 GHz QWCCRs were constructed and pressure tested in Germany [31,32]. Their results confirmed formation of plasma at pressures up to 6 atm with power levels of 30-300 W. The data show a trend requiring an increase in power with an increase in pressure.…”

Section: History Of the Qwccr Ignitermentioning

confidence: 89%

Electromagnetic design of a novel microwave internal combustion engine ignition source, the quarter wave coaxial cavity igniter

Pertl

¹

,

Smith

²

2009

Proceedings of the Institution of Mechanical Engineers, Part D:

View full text Add to dashboard Cite

New ignition sources are needed to operate the next generation of lean highefficiency internal combustion engines. A significant environmental and economic benefit could be obtained from these lean engines. Towards this goal, the quarter wave coaxial cavity resonator (QWCCR), igniter was examined. A brief overview of the QWCCR's history is presented, followed by an electromagnetic analysis of the resonator. Microwave and radiofrequency gas breakdown at atmospheric and higher conditions are reviewed briefly. The presented analysis focuses on geometric and material parameter relations compared with performance characteristics, such as resonator quality factor and developed tip electric field which initiates a single-electrode high-pressure microwave gas breakdown. Conductor surface losses, dielectric losses, and radiation losses of the device are considered in the analysis, for which parameters of a prototype QWCCR were chosen for construction and evaluation of a resonator. Improved designs allowed successful integration of a QWCCR into a Briggs and Stratton engine. Given the capability of precise control, high power, and high energy delivery, and the opportunity for further optimization, the QWCCR has the potential to deliver more energy per ignition than a conventional spark plug and thus should be considered for application as a lean ignition source.

show abstract

“…QWCCRs were constructed and pressure tested in Germany (Von Hagen 2001, Linkenheil 2004. Their results confirmed formation of plasma at various pressures up to 6 atmospheres with power levels of 30 to 300 W. The data shows a trend requiring an increase in power with an increase in pressure.…”

Section: Continuation Of These Experiments By Mcintyre's Thesis Work mentioning

confidence: 99%

Prospects of lean ignition with the quarter wave coaxial cavity igniter

Pertl¹

1

0

View full text Add to dashboard Cite

New ignition sources are needed to operate the next generation of lean high efficiency internal combustion engines. A significant environmental and economic benefit could be obtained from these lean engines. Toward this goal, the quarter wave coaxial cavity resonator, QWCCR, igniter was examined. A detailed theoretical analysis of the resonator was performed relating geometric and material parameters to performance characteristics, such as resonator quality factor and developed tip electric field. The analysis provided for the construction and evaluation of a resonator for ignition testing. The evaluation consisted of ignition tests with liquefied-petroleum-gas (LPG) air mixtures of varying composition. The combustion of these mixtures was contained in a closed steel vessel with a precombustion pressure near one atmosphere. The resonator igniter was fired in this vessel with a nominal 150 W microwave pulse of varying duration, to determine ignition energy limits for various mixtures. The mixture compositions were determined by partial pressure measurement and the ideal gas law. Successful ignition was determined through observation of the combustion through a view port. The pulse and reflected microwave power were captured in real time with a high-speed digital storage oscilloscope. Ignition energies and power levels were calculated from these measurements. As a comparison, these ignition experiments were also carried out with a standard non-resistive spark plug, where gap voltage and current were captured for energy calculations. The results show that easily ignitable mixtures around stoichiometric and slightly rich compositions are ignitable with the QWCCR using the similar kinds of energies as the conventional spark plug in the low milli-Joule range. Energies for very lean mixtures could not be determined reliably for the QWCCR for this prototype test, but could be lower than that for a conventional spark. Given the capability of high power, high energy delivery, and opportunity for optimization, the QWCCR has the potential to deliver more energy per unit time than a conventional spark plug and thus should be considered be as a lean ignition source.

show abstract

Microwave-generated plasma in air under standard conditions

Cited by 8 publications

References 2 publications

A versatile set-up to study plasma/microwave sources for liquid fuel ignition

A versatile set-up to study plasma/microwave sources for liquid fuel ignition

Electromagnetic design of a novel microwave internal combustion engine ignition source, the quarter wave coaxial cavity igniter

Prospects of lean ignition with the quarter wave coaxial cavity igniter

Contact Info

Product

Resources

About