Activities in the Laboratoire de Combustion et de Détonique ( UPR9028 du CNRS )

1. GDR-E Franco-Italien Activities in the Laboratoire de Combustion et de Détonique (UPR9028 du CNRS) Kick off meeting, 10 November 2005 Orléans • Detonations of CnHm/H2/N2/O2 mixtures • (H.N. Presles, D. Desbordes) • Modeling of Turbulent premixed flames H2-air • (M. Champion) • Non premixed swirl stabilized flames CnHm/H2/air • (J.M. Most) • Auto ignition of H2-CH4 mixtures in engines • (M. Bellenoue)

2. Hydrogen hazardsRecent results (1) : Detonability of H2/O2/N2 mixtures as a function of : - mixture ratio : 0,21 ≤ Φ ≤ 2,4 - nitrogen dilution : (H2-O2) 0 ≤ β=N2/O2 ≤ 3,76 (H2-air) - initial pressure : 0,2 bar ≤ P0 ≤ 1,5bar - initial temperature : 293K ≤ T0 ≤ 473K • Dilution of H2-O2 mixtures (Φ=1) with - O2 (towards lean mixtures ) - N2 (towards H2-air mixtures) => in each case detonability of initial mixture is maintained for large parameter variation i.e.: 0,5 ≤ Φ ≤ 1 and 0 ≤ β=N2/O2 ≤ 1 • Detonability is mainly controlled by ρ0 : higher ρ0 = higher detonability • A T0 increase (293K ≤ T0 ≤ 473K) induces : - a large increase of H2-air mixtures detonability - a low decrease of H2-O2 mixture detonability

3. Hydrogen hazards Recent results (2) : • Detonability of stoichiometric CH4/H2/O2/N2mixtures: with 0 ≤x ≤ 1 and 0 ≤ β ≤ 3,76 at P0 = 1bar and T0 = 293K ; 473K Binary CH4-H2-air mixture: => β = 3,76 : x = 1 (H2-air) high detonability x = 0 (CH4-air) low detonability • detonability controlled by the heaviest fuel: The replacement of 20% in moles of CH4 by H2does not change the mixture detonability => Valid for other CnHm/H2 mixtures

4. Hydrogen hazards Recent results (3) : • Study of the Deflagration-to-Detonation Transition in tube of stoichiometric H2/O2/N2 mixtures: • Characterization of TDD obtained from flame acceleration in obstacles laden tubes (inner diameter d and blockage ratio BR=0.5) • When N2 dilution is increased the run up distance to obtain a detonation (LDDT) is increased Scaling law: LTDD can be scaled with the caracteristic detonation cell size : λ = f ( Φ, β, P0 ) • LTDD ~ 36 (± 1) . λfor d/λ > 1

5. Hydrogen hazardsCurrent Studies : • Safety of propulsion nuclear reactor :Reduction of the detonability of H2-air mixtures by N2 injection. (TECHNICATOME contract) • Operational safety of fuel cells shiped on satellite : Explosion risk of H2-O2 mixtures under 70bar. (SAFT contract)

6. Hydrogen hazards Projects : • Effect of concentration gradients in H2-air mixtures on : - Inflammability - Deflagration Propagation Regimes - Deflagration-to-Detonation Transition - Detonation Propagation Regimes

7. Theoretical study of turbulent O2-H2 turbulent flame adjacent to a wall • The flow of reactive mixture is a stagnating turbulent flow , impinging on a solid wall and the intensity of turbulence is low. • Chemistry is represented by a 3-step reduced global mechanism. • Mean chemical rate are calculated through a 2 or 3 dimensional PDF • Specific properties of H2 are taken into account.

8. Effects of H2 additionon a Non-PremixedSwirl Stabilized CH4 Flame Fabio Cozzi Laboratorio di Combustione PoliMI-LC Politecnico di Milano, Milano, Italy 3 month stay –April to July 2005 in Poitiers Jean-Michel Most Laboratoire de Combustion et de Détonique LCD , UPR 9028 du CNRS ENSMA, Poitiers, France

9. Motivations • Why use Hydrocarbon+H2 fuels blend? • small % of H2 should improve flame stabiliy at very lean condition allowing the NOx emission reduction, • high % of H2 to reduce CO2 emission. • MHV, LHV fuels from biogass or crude oil refinery by-products contains some % of H2 • Which is the impact of fuels mixture on flame stability, pollutant emissions and soot formation? • The combustion of Hydrocarbon+H2 is still scarcely understood. Objectives • Experimental study of the effect of H2 addition to an overall lean CH4 swirl stabilized diffusion flame. • Flame structure and flow field modifications • Flame stability • Pollutant emission • Compare the results obtained on different burner geometry. • PoliMI 20 kW non-premixed burner (laboratory) - PIV, LDV, Rayleigh Scattering, ... • LCD 40 kW non-premixed burner (industrial) - ICCD (2D spontaneous emission), PLIF, PIV, LDV.

10. 8 mm 36 mm Swirled air flow Fuel CNRS-LCD PoliMI-LC Different quarl geometries are available Burner Head 25° Burner Configuration Maximum Input Thermal Power: 40kW Air: Swirled air (tang & axial inlet) Fuel: CH4+H2 (0% up to 20% H2) Fuel injection: axial Burner Configuration Maximum Input Thermal Power: 20kW Air: Swirled air (tang & axial inlet) Fuel: NG+H2 (0% up to 100% H2) Fuel injection: axial/radial

11. PoliMI-LC vs LCD Flame f~0.7, S~0.8 Fuel = 100% CH4 40 kW f~0.7, S~1 Fuel = 100% GN (~90% CH4) 20 kW PoliMI-LC LCD texp= 1 s texp= 0.02 s

12. PIV Field of View 100% GN 50% GN + 50% H2 20% GN+80% H2 100% H2 f=0.71 f=0.44 f=0.28 f=0.17 PoliMI-LC: Effect of H2 addition Unfiltered Flame Spontaneous Emission • The blue zone of the flame (CH* emission) decreases in size • The blue zone moves towards the burner head • A central yellow plume is clearly observable • At 100% H2 the flame has a reddish color likely due to H2O

13. PoliMI-LC: Experimental Results Effects of H2 addition • Flame Stability increases (burner can operate at overall leaner condition). • NOx and CO emissions increase as H2 increases from 0% to 80%. • Increase in Soot formation (qualitatively). • Fuel jet penetration increases. Changing fuel injection configuration • The yellow plume disappeared. • CO emission increases (as compared to axial injection). • NOx emission decreases (as compared to axial injection).

14. LCD: Spontaneous Emission (1/3) Operating Conditions: S=0.8, f ~ 0.7, Thermal Power = 40 kW. (F# 4.8, texp=1/25 s) 0 % H2 10 % H2 20 % H2 Hydrogen addition up to 20% by volume induces small changing in the visible flame shape!

15. LCD: CH*, OH* Chemiluminescence Operating Conditions: S=0.8, f ~ 0.7, Thermal Power = 40 kW. ICCD, average of 200 frames, texp=15 ms CH* (430 nm) OH* (310 nm) 0 % H2 20 % H2

16. LCD: CH*, OH* Chemiluminescence Operating Conditions: S=0.8, f ~ 0.7, Thermal Power = 40 kW. ICCD, average of 200 frames, texp=15 ms CH* (430 nm) • Filtered spontaneous emission images highlight small changing in the flame shape. • H2 addition shorten the regions CH* of OH* emission. • The distribution of reaction zone (based on CH* and OH* emission) appears to be spatially more uniform. OH* (310 nm) 0 % H2 20 % H2

17. LCD: Spontaneous Emission (2/3) Operating Conditions: S=0.4, f ~ 0.7, Thermal Power = 40 kW. (F# 2, texp=1/50 s) 0 % H2 10 % H2 20 % H2 Hydrogen addition up to 20% by volume induces small changing in the visible flame shape!

18. LCD: CH*, OH* Chemiluminescence Operating Conditions: S=0.4, f ~ 0.7, Thermal Power = 40 kW. ICCD, average of 200 frames, texp=15 ms CH* (430 nm) 0 % H2 20 % H2 • Filtered spontaneous emission images highlight small changing in the flame shape. • The distribution of the reaction zone (based on CH* emission) appears to be spatially more uniform.

19. LCD: Spontaneous Emission (3/3) Operating Conditions: S>0.8, f ~ 0.7, Thermal Power = 20 kW. (F# 2, texp=1/350 s) 0 % H2 20 % H2 40 % H2 Hydrogen addition of 40% by volume induces a significant change in the visible flame shape!

20. LCD: Conclusions • The existing LCD burner has been set up to burn CH4+H2 fuel mixture. • Several Filtered and Unfiltered image of the spontaneous flame emission has been collected under different experimental condition. Effects of H2 addition up to 20% by volume (40 kW) • Small effect on the visible flame shape. • Qualitatively: no relevant changes in burner stability (when using the quartz quarl). At f=0.7 no change in the minimum swirl number before flame blow-off (S~0.15). THIS SWIRL STABILIZED FLAME IS VERY STABLE! NEGLIGIBLE EFFECTS OF 20% H2 ADDITION ON A SWIRL STABILIZED DIFFUSION FLAME !??