Plasma Assisted Ignition and Combustion

1. Plasma Assisted Ignition and Combustion S.M.Starikovskaia, A.Yu.Starikovskii

2. Plan of the Talk 1. Introduction: why nonequilibium PAI/PAC? 2. Typical schemes for PAI/PAC experiments; general results 3. PAI kinetics: experiments and modeling 4. Perspectives Physics of Nonequilibrium Systems Laboratory

3. “Fast flow” ignition (Mintoussov, Starikovskii, 2005) Physics of Nonequilibrium Systems Laboratory

4. Plasma: equilibrium or nonequilibrium? Physics of Nonequilibrium Systems Laboratory

5. Scheme of H2-O2 Combustion Physics of Nonequilibrium Systems Laboratory

6. Comparison of the Reaction Rates E/N=100-300 Td Kd=10-10-10-8 cm3/s Physics of Nonequilibrium Systems Laboratory

7. Possible Mechanisms for PAI/PAC • Radical mechanism • Ion mechanism • Mechanism with excited species: • electronic, vibrational excitation Physics of Nonequilibrium Systems Laboratory

8. Complexity of the object Physics of Nonequilibrium Systems Laboratory

9. Scheme 1a: Discharge + Flow, Quasistationary System A) Fast Flows (M>1) Physics of Nonequilibrium Systems Laboratory

10. Hypersonic MW ignition Lebedev P., Klimov A., Proc.of WSMPA, 1999, IVTAN, Moscow, P.142 Physics of Nonequilibrium Systems Laboratory

11. Hypersonic MW ignition Scheme of experimental setup for hypersonic MW ignition (a) and the timeline of operation of experimental setup (b). Pressures and temperatures as well as times of discharge and fuel injection are marked in the scheme Esakov I I, Grachev L P, Khodataev K V, Vinogradov V A and Van Wie D M Efficiency of propane-air mixture combustion assisted by deeply undercritical MW discharge in cold high--speed airflow 44th AIAA Aerospace Sciences Meeting and Exhibit (Reno, Nevada, USA, 9---12 January 2006) AIAA-2006-1212 Physics of Nonequilibrium Systems Laboratory

12. Scheme 1b: Discharge + Flow, Quasistationary System B) Slow Flows (1-10 m/s) Physics of Nonequilibrium Systems Laboratory

13. Discharge Development in the Gas Flow.U = 25 kV, timp = 25 ns, Propane-Air, f = 0.7 Dt = 0.3 ns tmax = 20 ns Mintoussov E I, Pancheshnyi S V and Starikovskii A Yu Propane-air flame control by non—equilibriumlow-temperature pulsed nanosecond barrier discharge. 42nd AIAA Aerospace Sciences Meeting and Exhibit (Reno, Nevada, USA, 5—8January 2004) AIAA-2004-1013 Physics of Nonequilibrium Systems Laboratory

14. Bluff-body nozzle with ns discharge Galley D, Pilla G, Lacoste D, Ducruix S, Lacas F, Veynante D and Laux C O Plasma-enhanced combustion of a lean premixed air-propane turbulent flame using a nanosecond repetitively pulsed plasma. 43rd AIAA Aerospace Sciences meeting and Exhibit (Reno, Nevada, USA, 10--13 January 2005) AIAA-2005-1193 Physics of Nonequilibrium Systems Laboratory

15. Discharge enhanced flame stabilization The improvement of liftoff jet velocity as a function of normalized co-flow speed. Here SLis a laminar flame speed. SECD is a single electrode corona discharge, USRD is a ultra-short repetitively pulsed discharge Kim W, Do H, Mungal M G and Cappelli M A Flame stabilization enhancement and NOx production using ultra short repetitively pulsed plasma discharges. 44th AIAA Aerospace Sciences Meeting and Exhibit (Reno, Nevada, USA, 9-12 January 2006) AIAA-2006-560 Physics of Nonequilibrium Systems Laboratory

16. Ignition of a gas flow by RF discharge Flow temperatures in transverse RF discharge in air flow at different pressures and mass flow rates. RF power is 200~W Chintala N, Meyer R, Hicks A, Bao A, Rich J W, Lempert W R and Adamovich I V 2005 Nonthermal ignition of premixed hydrocarbon--air flows by nonequilibrium radio frequency plasma. J.Propulsion and Power 21(4) 583-90 Physics of Nonequilibrium Systems Laboratory

17. Scheme 2 (PAI): pulsed discharge + ignition. No flow! Physics of Nonequilibrium Systems Laboratory

18. 3) Volume repetitive nanosecond discharge U=-11 kV, t=25 ns, Gate=1 ns, f=40 Hz Dl=300-800 nm Physics of Nonequilibrium Systems Laboratory

19. Typical behavior of electric field Physics of Nonequilibrium Systems Laboratory

20. How does it works: decrease of ignition delay time (PAI) Autoignition Plasma-assisted ignition Physics of Nonequilibrium Systems Laboratory

21. Comparison of experiments and numerical modeling: CH4-C5H12 mixtures Physics of Nonequilibrium Systems Laboratory

22. Kinetics of Plasma Assisted Ignition at Elevated Temperatures S.M.Starikovskaia, N.L.Aleksandrov, S.V.Kindusheva, I.N.Kosarev, A.Yu.Starikovskii

23. Experimental setup for plasma ignition Physics of Nonequilibrium Systems Laboratory

24. Setup for nanosecond Electrical Measurements Physics of Nonequilibrium Systems Laboratory

25. Scheme of the experiment Physics of Nonequilibrium Systems Laboratory

26. Parameters Varied in Experiments • Mixture composition CH4/C2H6/C3H8/C4H10/C5H12 - O2 – Ar (90%) • Temperature 950-2000 K • Pressure 0.2-1.0 atm Physics of Nonequilibrium Systems Laboratory

27. Parameters Controlled in Experiments • Velocity of the Shock Wave (T5, P5) • IR Emission of CO2 at 4.21 mm (T5) • Emission of OH at 306 nm (tign) • Emisison of CH at 431 nm (tign) • Distribution of potential along the gap (E/N) • Electrical current (energy input) Physics of Nonequilibrium Systems Laboratory

28. Shift of the ignition delay time Physics of Nonequilibrium Systems Laboratory

29. Particles, responsible for Ignition, are… Atoms? Ions? Vibrationally excited species? Radicals? Electronically excited states? Physics of Nonequilibrium Systems Laboratory

30. Typical evolution of electric field and current (CH4:O2:Ar; T5=1450 K, n5=6x1018 cm-3) Physics of Nonequilibrium Systems Laboratory

31. The peak E/n for C2H6-C5H12-containing mixtures Physics of Nonequilibrium Systems Laboratory

32. Specific energy input Physics of Nonequilibrium Systems Laboratory

33. Composition of the mixtures Physics of Nonequilibrium Systems Laboratory

34. Scheme of the Discharge Description Physics of Nonequilibrium Systems Laboratory

35. Typical densities of active species produced by the discharge vs E/n: C2H6, C5H12 Physics of Nonequilibrium Systems Laboratory

36. Kinetics in the discharge Physics of Nonequilibrium Systems Laboratory

37. Densities of active species produced by the discharge in CH4:O2:Ar vs n5 Physics of Nonequilibrium Systems Laboratory

38. Densities of active species produced by the discharge: all mixtures Physics of Nonequilibrium Systems Laboratory

39. Kinetics of the ignition: reaction rates (T5=1530 K, n5=5x1018 cm-3) Physics of Nonequilibrium Systems Laboratory

40. Kinetics of the ignition: kinetic curves (T5=1530 K, n5=5x1018 cm-3) Plasma assisted ignition is characterized by: – slow increase of gas temperature – developed kinetics of intermediates – partial fuel conversion during induction time Physics of Nonequilibrium Systems Laboratory

41. PAI: Radical Mechanism Physics of Nonequilibrium Systems Laboratory

42. Sensitivity analysis Physics of Nonequilibrium Systems Laboratory

43. Comparison of Experiments and Numerical Modeling: All Mixtures Physics of Nonequilibrium Systems Laboratory

44. Experimental conditions: temperature Physics of Nonequilibrium Systems Laboratory

45. Experimental conditions: densities Physics of Nonequilibrium Systems Laboratory

46. Reduction of the ignition delay time Physics of Nonequilibrium Systems Laboratory

47. Direction of the research Physics of Nonequilibrium Systems Laboratory

48. Comparison of experiment (CH*) and calculations (CH) Physics of Nonequilibrium Systems Laboratory

49. Kinetics of the ignition: kinetic curves for C2H6-containing mixture Physics of Nonequilibrium Systems Laboratory

50. Development of surface nanosecond discharge at high pressures Optimization: electrode system HV pulse width HV pulse amplitude Measurements: current and voltage energy input time/space/wavelength resolved emission electric field electron density gas temperature radicals Physics of Nonequilibrium Systems Laboratory