Current engines and combustors run at high temperature, which leads to problems of engine knocking, soot and NOx emissions, and difficulty in combustion control. On the other hand, low-temperature combustion and fuel oxidation below 1000 K is typically too inaccessible or unstable to be used for engines and fuel processing. The novelty of the present invention is that by using oxygen-rich oxidizer stream and non-equilibrium plasma — which creates new chemical species such as singlet oxygen, ozone, ions, and intermediate radicals — stable, low-temperature cool flames and flameless combustion can be established to enable fast, low-temperature fuel oxidation in a broad range of pressures (0.1 to 50 atm). Due to the low flame temperature (500 K to 900 K), no soot emissions and no NOx emissions are formed in the cool flames and flameless combustion region. Moreover, the new cool flame regime allows rapid fuel (gasoline, diesel, and jet fuel) decomposition and partial oxidation to form clean and valuable small-molecule fuels such as C2H4, CH2O, CH3HCO, and CH4 at low cost and high efficiency.

A new method using non-equilibrium plasma discharge in an oxygen-rich combustion environment to establish low-temperature cool flame and flameless combustion with zero emissions was invented. The new low-temperature combustion technology can be used to achieve simultaneous efficiency increase and emission reduction by enabling control of engine knocking in a gasoline engine; control of ignition in HCCI, RCCI, and highly fuel-stratified advanced gasoline and diesel engines; low-temperature combustion in low-emission gas turbine engines; and low-temperature fast fuel cracking and processing. It includes a new process to establish a new low-temperature flame and combustion regime to accelerate fuel oxidation and processing without producing emissions. Cool flames and flameless combustion with peak flame temperature below 700 K was observed at low pressure (0.1 torr) and 1 atm for different transportation fuels with flow residence time below 10 ms. No soot emissions were observed.

This work was done by Yiguang Ju of Princeton University Engineering Quad for Johnson Space Center. Princeton University elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

Princeton University
4 New South Building
NJ 08544.

Refer to MSC-26029-1

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This article first appeared in the June, 2018 issue of Tech Briefs Magazine.

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