Abstract
We developed a semiconductor microwave system to improve the ignition process in a combustion system. Under atmospheric pressure conditions, large plasma was successfully ignited by a 2.45 GHz microwave, and it is characterized in comparison with standard spark plug ignition and laser ignition. The size of the microwave power source was also effectively reduced with the minimal size (100 × 60 mm2) that could fit in the palm of a hand. We then prototyped a microwave plug with a diameter of 4 mm, which is smaller than the standard spark plugs for passenger cars. The design and electric field strength are discussed in detail. Combustion experiments were conducted using a motorcycle engine and an actual light vehicle, and significant fuel efficiency improvement was experimentally obtained. We investigated the wear of the plug caused by continuous operation, and efficiently improved the endurance by swinging the resonance frequency between 2.4 and 2.5 GHz. In a passenger car engine experiment using a flat panel igniter, significant fuel efficiency improvement was confirmed. Further failure analysis revealed that the ceramic was severely damaged by a large current surge.
Highlights
Ignition is the most important part of the combustion process
There are multiple variations of the ignition process spark plug and microwave discharge igniter (MDI) depending on the energy input
Regardingthe thedevelopment developmentofofMDI, MDI, we developed one that is smaller than smallRegarding we developed one that is smaller than thethe smallest est spark diameter used in gasoline-powered vehicles
Summary
Ignition is the most important part of the combustion process. Optimal emission control during ignition is indispensable for reducing CO2 and exhaust-gas emissions [1]. Most of the ignition in a combustion system, such as spark plug and laser ignition, locally generates a high-temperature heat source. Those represented by the spark plug generate heat transfer losses through cylinder walls [8,9] Laser ignition solves this problem by moving the flame kernel away from the combustion chamber [10,11]. Stable ignition requires high voltage, high-energy heat source breakdown, plasma initialization, flame kernel development, and flame propagation physicochemical processes. We are developing a compact ignition source with a novel structure that initiates the breakdown by microwaves instead of a high-voltage source, sustains the expansion of the kernel, and stabilizes the ignition by further input of microwaves [16–20].
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