Extending Lean Operating Limit and Reducing Emissions of Methane Spark-Ignited Engines Using a Microwave-Assisted Spark Plug

Figure 7

The percent change in carbon-monoxide (CO) emissions and total unburned hydrocarbon (THC) emissions with 1600 mJ of microwave-enhanced ignition from emissions with spark-only ignition. Addition of microwave energy decreases the amount of CO and THC at leaner conditions. A decrease in THC is expected under lean operation with the microwave because more cycles are complete combustion.