Low-energy non-thermal plasma ignition, also referred to as transient plasma ignition, can significantly improve fuel efficiency and reduce emissions by enabling stable ignition in gasoline engines at high-pressure, high-exhaust gas recirculation (EGR), and/or ultra-lean conditions.  

In lean-burn gasoline engines, dilution is done with air or with EGR, however, this dilution reduces the energy density of the in-cylinder charge, which reduces the engine’s peak power.  Although peak power can be recovered with turbocharging, the combination of dilution and intake pressure boost makes ignition increasingly difficult.  Traditional ignition methods can ignite this mixture if the energy per discharge is significantly increased, but this causes accelerated electrode wear as well as fatigue throughout the ignition system. 

TPS’s novel transient plasma ignition system is a solution that does not cause accelerated wear and fatigue, while simultaneously enabling dilute burn combustion to reduce harmful emissions and improve fuel economy.  High-voltage low-energy nanosecond pulses are used to produce a non-thermal plasma, which requires much lower average power and is substantially more efficient compared to the equilibrated or quasi-equilibrated plasmas commonly generated by AC and RF discharges.

The spark from a traditional spark ignition system heats a zone of combustible mixture to a temperature where radicals are thermally generated and grow in number such that chemical reactions rapidly proceed and generate heat faster than heat transfer can cool the zone.  TPS’s strategy is to generate the radicals directly in a non-thermal plasma rather than squander the energy in the less efficient and slower thermal generation approach.  As a result, the induction time for the TPS approach is much less compared to thermal ignition methods, and therefore less energy is needed to generate heat more quickly and the mixture can be leaner.

The TPS ignition system is designed to be retrofitted to existing engines by following the same form factor of systems already on the market.

References

1. Sjöberg, M., Zeng, W., Singleton, D., Sanders, J. et al., "Combined Effects of Multi-Pulse Transient Plasma Ignition and Intake Heating on Lean Limits of Well-Mixed E85 DISI Engine Operation," SAE Int. J. Engines 7(4):1781-1801, 2014.

2. D. Singleton and M. A. Gundersen, “Transient Plasma Fuel-Air Ignition,” IEEE Transactions on Plasma Science, Issue 99, 27 May 2011.

3. D. Singleton, S J. Pendleton, and M. A. Gundersen, “The role of non-thermal transient plasma for enhanced flame ignition in C2H4-air,” J. Phys. D: Appl. Phys. 44 (2011) 022001.

4. T. Shiraishi, T. Urushihara, “Fundamental Analysis of Combustion Initiation Characteristics of Low Temperature Plasma Ignition for Internal Combustion Gasoline Engine”, SAE International, 2011-01-0660.

5. T. Shiraishi, T. Urushihara, and M. A. Gundersen, “A trial of ignition innovation of gasoline engine by nanosecond pulsed low temperature plasma ignition,” J. Phys. D: Appl. Phys. 42 135208 (2009).

6. Cathey, C., T. Tang, T. Shiraishi, T. Urushihara, A. Kuthi, and M. A. Gundersen, “Nanosecond Plasma Ignition for Improved Performance of an Internal Combustion engine”, IEEE Trans on Plasma Sci., Dec. 2007.

7. S. M. Starikovskaia, “Plasma assisted ignition and combustion,” J. Phys. D: Appl. Phys., vol. 39, no. 16, pp. R265–R299, Aug. 2006.

8. Wang, F., J. B. Liu, J. Sinibaldi, C. Brophy, A. Kuthi, C.Jiang, P. Ronney, M. A. Gundersen, “Transient plasma ignition of quiescent and flowing air/fuel mixtures,” IEEE Transactions on Plasma Science, 33:844-849, 2005.

9. K. Packham, “Lean-burn engine technology increases efficiency, reduces NOx emissions,” Power topic #7009, Technical information from Cummins Power Generation 

10. Danaiah P., Ravi Kumar P, Vinay Kumar D., “Lean Combustion Technology for Internal Combustion Engines: a Review”, Science and Technology 2012, 2(1): 47-50