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Microwave Spark Plug for Very High-Pressure Conditions
Abstract
This paper presents an improved microwave plasma (microplasma) spark plug for an ignition system at 2.45 GHz. The internal transformation networks of these spark plugs generate very high voltage at one frequency on the one hand, and support the plasma after ignition on the other. Using this network, plasma ignition and sustainment are possible at high-pressure conditions. This novel spark was optimized with regard to the requirements for fully automated production, as well as very good performance. For this, multiphysics fi eld simulations were performed to optimize the electrical performance, and to monitor the temperature at different sections of the spark plug. This presentation focuses on the spark plug development optimization, including the simulation results, and realization of the initial hardware.
... The presented construction of Fig. 5 is very nice to transfer in a mass production. Over time, detailed multiphysics simulations to this construction were published on the special international spark plug conference [5], [15]. ...
... The first associated field simulations of this design have already been published at the international spark plug special conference [5], [15]. The field simulation (HFSS from Ansys) of the ignition is presented in Fig. 8. ...
Upcoming gasoline engines should run with a larger number of fuels beginning from petrol over methanol up to gas by a wide range of compression ratios and a homogeneous charge. In this article, the microwave (MW) spark plug, based on a high-speed frequency hopping system, is introduced as a solution, which can support a nitrogen compression ratio up to 1:39 in a chamber and more. First, an overview of the high-speed frequency hopping MW ignition and operation system as well as the large number of applications are presented. Both gives an understanding of this new base technology for MW plasma generation. Focus of the theoretical part is the explanation of the internal construction of the spark plug, on the achievable of the high voltage generation as well as the high efficiency to hold the plasma. In detail, the development process starting with circuit simulations and ending with the numerical multiphysics field simulations is described. The concept is evaluated with a reference prototype covering the frequency range between 2.40 and 2.48 GHz and working over a large power range from 20 to 200 W. A larger number of different measurements starting by vector hot-
measurements and ending by combined working scenarios out of hot temperature, high pressure and charge motion are winding up the article. The limits for the successful pressure tests were given by the pressure chamber. Pressures ranged from 1 to 39 bar and charge motion up to 25 m/s as well as temperatures from 30° to 125°.
... Such fast S11-switchings are necessary for plasma applications to shift from the ignition frequency to the frequency best suited to drive the plasma load. Probably the best known example for such applications with the highest speed performance for this shift is the RF spark plug [5]. The Application with the requirement for absolute lowest production cost is the plasma lamp, e.g. ...
An atmospheric-pressure air microplasma is ignited and sustained in a 25 µm wide discharge gap formed between two co-planar gold electrodes. These electrodes are the two ends of a microstrip transmission line that is microfabricated on an Al2O3 substrate in the shape of a split-ring resonator operating with a resonant frequency of 895 MHz. At resonance, the device creates a peak gap voltage of ~390 V with an input power of 3 W, which is sufficient to initiate a plasma in atmospheric pressure air. Optical emission from the discharge is primarily in the ultraviolet region. In spite of an arc-like appearance, the discharge is not in thermal equilibrium as the N2 rotational temperature is 500–700 K. The intrinsic heating of the Al2O3 substrate (to 100°C) causes a downward shift in the resonant frequency of the device due to thermal expansion. The temperature rise also results in a slight decrease in the quality factor (142 > Q > 134) of the resonator. By decreasing the power supply frequency or using a heat sink, the microplasma is sustained in air. Microscopic inspection of the discharge gap shows no plasma-induced erosion after 50 h of use.
We report the design, fabrication and characterization of two microwave-excited microplasma sources based on coaxial transmission line resonators (CTLR). The sources are capable of generating electric fields of ~106 V m−1 at 900 MHz and 2.45 GHz. These devices can self-ignite helium or argon discharges in a wide pressure range including atmospheric pressure. The gas temperature in an argon discharge open to atmospheric air is ~400 K. Using air as a dielectric, the working gases can be passed through the CTLR, resulting in the formation of plasma jets suitable for surface treatments. The device efficiency on transferring the input power into the plasma is 50–85% depending on the gas used. No thermal damage or electrode erosion has been observed in the devices.
This paper presents a microplasma ignition at 2.45GHz for various applications as well as
spark plugs, plasma beams, low and high pressure lamps by using a three stage impedance transformer.
The presented transformation network generates a very high voltage.
Using this network, plasma ignition and sustainment are possible
under atmospheric pressure, low pressure or even under very high pressure conditions.
It could be shown in different tests that this concept holds true for power levels varying between
10W to 200W, offering various advantages for a variety of plasma applications at 2.45GHz.
This paper presents a microwave plasma (microplasma) ignition at 2.45GHz for spark plugs and other applications such as plasma beams as well as low and high pressure lamps. A novel transformation network is introduced, generating the very high voltage required for the ignition. Using this network, plasma ignition and sustainment are possible under atmospheric pressure, low pressure or even under very high pressure conditions. It could be shown in different tests that this concept holds true for power levels varying between 10W to 200W, offering various advantages for a variety of plasma applications at 2.45GHz. This presentation focuses on the spark plug application, including a test engine.
A plasma system based on microstrip technology was developed for the generation of atmospheric pressure microplasmas. A discharge gap was placed between the striplines and the ground plane on the transverse cross section in the direction of microwave propagation. This microstrip structure permits the concentration of electric fields at the discharge gap, which is confirmed by a computer simulation using the three-dimensional simulation code based on the finite-difference time-domain method, and can produce atmospheric pressure plasmas even in air. The microplasmas were sustained in the discharge gap (width: 0.2 mm, length: 6 mm) at a microwave power of 1 W. The experimentally measured rotational temperature of nitrogen molecules was 800 K, indicating these plasmas to be nonthermal plasmas. This plasma system will provide a portable microplasma system utilizing a small semiconductor microwave source and a large-scale atmospheric pressure nonthermal plasma using the array configuration.
This paper presents the fundamentals of a microplasma ignition and a patented coaxial system for ignition at atmospheric pressure with low RF power. The idea is to transform the voltage of the RF signal by a transformer and a resonator. Due to the fact that this coaxial structure realizes a very high impedance transformation, a microplasma at 2.45 GHz can be ignited and sustained with a 50 W microwave source. With this concept a magnitude of 30 MVm-1 is realized at the electrode, which sufficiently increasing the kinetic energy of the free electrons to ionize air and resulting in a plasma sphere with a diameter of 6 mm.
Gasoline direct injection (GDI) is one of the future engine concepts offering a significant increase in efficiency of automotive engines. In this technique, the gasoline spray is directly injected into the combustion chamber, which yields a strongly inhomogeneous air-gasoline mixture. Hence, it is difficult to maintain reliable ignition using a conventional spark-plug. In this paper, a novel spark-plug based on a coaxial microwave resonator is presented. First, the design of the resonator is described. Then its capability of generating plasma in the pressure range up to 5 bar (3750 torr) is evaluated. Finally, some results of gasoline ignition experiments in a combustion chamber are presented.
Holger Heuermann, Aachen University of Applied Sciences; High Frequency Technology
- Prof
- Dr
- Ing
Prof. Dr.-Ing. Holger Heuermann, Aachen University of Applied Sciences; High Frequency Technology; 52066 Aachen
Alternative ignition system based on microwave plasma " , part of the book: Advanced ignition systems for gasoline engines, Expert Verlag
- H Heuermann
- A Sadeghfam
- T Finger
H. Heuermann, A. Sadeghfam and T., Finger, " Alternative ignition system based
on microwave plasma ", part of the book: Advanced ignition systems for gasoline
engines, Expert Verlag, ISBN 978-3-8169-3190-4, pp. 95-103, 2013.
Torsten Finger, Aachen University of Applied Sciences; High Frequency Technology
- M Eng
M.Eng. Torsten Finger, Aachen University of Applied Sciences; High Frequency
Technology; 52066 Aachen