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Ultraclean Low Swirl Combustion

Lawrence Berkeley National Laboratory

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Laboratory UCLSB prototype with 5 cm internal diameter, firing at a rate of 15 kilowatts. This burner is made entirely out of plastic components to showcase its unique lifted flame feature.
Laboratory UCLSB prototype with 5 cm internal diameter, firing at a rate of 15 kilowatts. This burner is made entirely out of plastic components to showcase its unique lifted flame feature.

Technology Marketing Summary

Burners are used in industry for a wide range of applications including water heaters, power generators, oilers, and HVAC systems. Parallel consumer applications include gas-fired home water heaters, heating systems, and clothes dryers. Natural gas is more efficient and less expensive than electricity and is the current and future fuel of choice. However, conventional gas burners emit oxides of nitrogen (NOx) creating ozone in the lower atmosphere due to incomplete fuel combustion and high temperature operation.


Robert Cheng at Lawrence Berkeley Laboratory originally developed a weak swirl burner as a better way to stabilize flame for scientific study. As with many purely scientific investigations, the resulting device is a better performer than those commercially available. The new burner produces almost no NOx, the chemical responsible for ozone in the lower atmosphere. The shape and temperature of the flame are responsible for the improvement, but the actual result will be device dependent. The simplicity of the new design eliminates device scaling and tolerance problems thereby aiding manufacturability. The design could replace most medium and small scale burners with flame temperature requirements below 2,600deg.F.

Market Driver: NOx is responsible for the dirty brown air over most U.S. cities. More than 100 U.S. cities have unsafe ozone levels that exceed federal health standards. Many cities are considering limiting installation of new conventional gas burners. Government energy-saving incentives and pollution control regulations like those for efficient lighting and auto emissions should cause the market to grow at a rapid pace.

  • SAFETY: Broad operating range of the fuel-to-air ratio limits risk of blow-off and flashback
  • FUEL EFFICIENCY: Improved fuel efficiency dependent on application
  • NOx EMISSIONS: Ultra-low NOx emissions
  • OZONE PRODUCTION: Ultra-low NOx means ultra-low ozone production.
  • MANUFACTURABILITY: Low tolerance parts, Reynolds number scaling not necessary
Applications and Industries
  • Commercial HVAC Systems
  • Industrial Boilers
  • Distillation Columns
  • Water Heaters
  • Furnaces
  • Clothes Dryers
  • Power Generators
More Information

Ultralean Low-swirl Combustion in the News

Ultraclean Low-swirl Combustion Will Help Clear the Air

Ultra-Low Emissions Low-Swirl Burner

Ultra-Clean Low Swirl Combustion L2M 10 Years Later


Scaling and Development of Low -swirl Burners for Low Emission Furnaces and Boilders, Proceedings of the Combustion Institute, Volume 28, 2000/pp. 1305–1313

Laboratory Investigation of an Ultralow NOx Premixed Combustion Concept for Industial Boilders, Proceedings of the Combustion Institute, Volume 29, 2002/pp. 1115–1121

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 5,879,148
Mechanical swirler for a low-NO.sub.x, weak-swirl burner
Disclosed is a mechanical swirler for generating diverging flow in lean premixed fuel burners. The swirler of the present invention includes a central passage with an entrance for accepting a feed gas, a flow balancing insert that introduces additional pressure drop beyond that occurring in the central passage in the absence of the flow balancing insert, and an exit aligned to direct the feed gas into a combustor. The swirler also has an annular passage about the central passage and including one or more vanes oriented to impart angular momentum to feed gas exiting the annular passage. The diverging flow generated by the swirler stabilizes lean combustion thus allowing for lower production of pollutants, particularly oxides of nitrogen.
Lawrence Berkeley National Laboratory 03/09/1999
Technology Status
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To: Shanshan Li<>