Ammonia (NH3) and hydrogen (H2) are considered as the leading candidates among all green fuels. However, NH3 combustion is characterized by low burning rates compared to conventional fuels and which requires H2 or natural gas (NG) addition to achieve desirable stabilization. Our hypothesis is that the increased reaction rates achieved via transient plasma improve the overall burning rate of NH3, thus, reducing the requirement for adding NG or H2. This is important since the availability, transport, storage, and use of H2 presents significant challenges. We report the use of nanosecond pulsed transient plasma (NPTP) to improve the ignition of carbon-free fuels including NH3 and H2. This transient nanosecond plasma generates highly reactive radical species such as atomic oxygen, atomic hydrogen, and NH* radicals that accelerate the combustion rates of both ammonia and hydrogen, providing stable combustion and eliminating greenhouse gas emissions. Our results show the following: 1.) Transient plasma enables higher NH3:H2 ratios that support stable combustion than with conventional spark. 2.) With transient plasma, the maximum engine power increases with the addition of ammonia but decreases with conventional spark. 3.) Transient plasma enables further reduction of CO2 with ammonia than conventional spark under lean methane conditions. It should be noted that, in addition to eliminating CO2, NH3 and H2 do not produce particulate matter (i.e., soot). This approach also enables substantially reduced carbon emissions with NH3:CH4 and H2:CH4 blends.

Transient plasma-enhanced combustion of carbon-free fuels for reduced greenhouse gas emissions

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