Purdue University researchers are developing pre-chamber technology for automobiles to replace conventional spark plugs and enable more reliable ultra-lean combustion. In the pre-chamber approach, a tiny chamber—a pre-chamber—is filled with a mixture of fuel and air. The mixture ignites, producing combustion, and specialized nozzles in the bottom of the chamber release the hot combustion products in the form of powerful jets, which penetrate into the main chamber and cause ignition.

Compared with traditional spark ignition, this method provides a large surface for multiple-site ignition and fast flame propagation and enhances the overall combustion efficiency. Both passive and active pre-chambers are being considered.

For the former, the main-chamber mixture is pushed into the pre-chamber by compression stroke through the tiny holes; and for the latter, additional fueling is supplied to the pre-chamber to facilitate leaner operation of the main combustion chamber.

Ultra-lean combustion technologies are seen as a potential solution to meet stringent emission regulations including NO_x. However, ultra-lean combustion has serious challenges, including misfires as a result of poor ignition. Such misfires and difficulties in ignition can lead to cycle-to-cycle variability, rough operation, reduction in efficiency, and increase in unburned hydrocarbon emissions.

The Purdue pre-chamber technology looks to ignite ultra-lean fuel/air mixtures, which may not be able to ignite using current pre-chamber technologies.

Sequences of images showing the jet (produced from pre-chamber on the top) penetrating into the main chamber and igniting the main-chamber mixture.

Li Qiao, an associate professor of aeronautics and astronautics in Purdue’s College of Engineering, said the technology her team is working with already has been used in large bore natural gas engines and in some F1 racing cars because of its superior performance, but it is new to passenger car gasoline engines.

The auto industry is feeling the pressure to optimize these engines because of the competition from electric vehicles. Several automotive engine companies have started exploring pre-chamber technology for passage cars.

—Li Qiao

Qiao is currently collaborating with industry on design and optimization of passive and active pre-chambers for gasoline engines.

Qiao and her team have performed tests at Purdue’s Herrick Laboratories and Maurice J. Zucrow Laboratories, the largest academic propulsion lab in the world.

Qiao and the team are working with the Purdue Research Foundation Office of Technology Commercialization to patent their technology. They are looking for additional partners.

Resources

• S Biswas, L Qiao “Apparatus and methods of operating a combustion engine”, US Patent App. 15/795,937