Ignition of hydrogen-air mixtures under volumetric expansion R. Mével a , b , J. Melguizo-Gavilanes c and D. Davidenko d 7th International Conference on Hydrogen Safety - Hamburg, GER a Center for Combustion Energy b Department of Automotive Engineering, Tsinghua University c California Institute of Technology (GALCIT) d The French Aeropace Lab - ONERA Monday September 11, 2017 � ��� � �������� ���� Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 1 / 29 ���(-� 8ORDO��4NRSJSTSF�O���I�RJDR��NE��FDINOLOH���84�� �8���D��JN��I�RJDR ����-� �O��L�4NRSJSTSF�O���FDINOLOH���6�� ���SODKIOLM����FEFN��I�0 JN��I�RJDR ������ ����-��MF �NJUF�RJS�����FEFN�� �ORSEOD ������ ���(-���JNDFSON��NJUF�RJS�����JNDFSON��95����.� ��NEJ��9�SJON�L���CO��SO�JFR���JUF�MO�F��/.����.�� /12�/��ORSEOD ���(�� ����-��MF �NJUF�RJS��� P�JNDJP�L��FRF��DI�FNHJNFF� ���)-��IOTR�NE�AOTNH���LFNSR�PL�N�����EFF ����-�/FNSF���O��/OMCTRSJON�1NF�H����RJNHIT��TNJUF�RJS� 1W�MPLF-� 2L�MF� JN�/I�NNFL� �JSI� :CRS�DLFR 8�JN��FRF��DI��OPJDR �JHI�PF��O�M�NDF��F�DSJNH��LO��RJMTL�SJONR ��FMJWFE��L�MFR�JN�STCFR��NE�DI�NNFLR 0F�L�H��SJON�SO�EFSON�SJON�S��NRJSJON 2L�MF��L�RIC�DK�JN�ST�CTLFNS�DI�NNFL��LO� �OS�RRJTM��FLF�RF�JN�SIF�MODIFMJD�L�DONUF�RJON� O��CJOM�RR
Introduction outlines Introduction 1 Methodology and calculation procedure 2 Results and discussion 3 Conclusion 4 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 2 / 29
Introduction Importance of unsteadiness Formation of expansion waves SW-obstacle SW diffraction Expansions can be formed in complex pipelines Important for shock ignition and industrial safety Simulations by Prof. H. Hornung Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 3 / 29
Introduction Importance of unsteadiness Re-initiation behind a decaying shock wave (1) Detonation direct initiation 2-D images 1-D simulations 1.8 1.6 ZND 1.4 Shock pressure p / p 3 1.2 1 t = 6.5 µ s t = 9.0 µ s 0.8 2 0.6 1 0.4 0.2 0 20 40 60 80 100 120 140 160 Distance t 14.4 s t 16.6 s Bach et al., 1969 Ng and Lee, 2003 SW velocity decreases much below D CJ before re-initiation occurs Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 4 / 29
Introduction Importance of unsteadiness Re-initiation behind a decaying shock wave (2) Detonation diffraction 2-D simulations Velocity along the axis 1.0 0 1.0 2.0 0.9 0.8 3.0 2.5 D a / D CJ 0.7 3.5 0.6 3.75 0.5 4.15 0.4 100 150 200 250 x a SW velocity decreases much below D CJ before re-initiation occurs Results from Arienti and Shepherd, 2005 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 5 / 29
Introduction Importance of unsteadiness Reaction in expanding flows (1) Lagrangian particles Particle path Temperature profile 6 140 1 120 2 4 3 4 100 5 ~ ~ T 6 t 7 80 8 2 9 60 10 40 1 2 3 4 5 6 7 8 9 10 0 40 60 80 100 120 140 160 300 350 400 450 500 ~ ~ t r As the SW decays, ignition delay-time increases and the reaction is eventually quenched Results from Eckett et al., 2000 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 6 / 29 ��C�9�/2�2����:�6�����CCC 1/:0�725� ��5�1��� ��/9��16�,70�/�����������1�������/��������������0��1������6���/:0�725����������:����������/�/79/09��/��6�����CCC 1/:0�725� ��5�1�������:� 6������2D 2�7 ��5��� �����.���������������� ��C�9�/2�2����:�6�����CCC 1/:0�725� ��5�1��� ��/9��16�,70�/�����������1�������/��������������0��1������6���/:0�725����������:����������/�/79/09��/��6�����CCC 1/:0�725� ��5�1�������:� 6������2D 2�7 ��5��� �����.����������������
Introduction Importance of unsteadiness Reaction in expanding flows (2) Ignition dynamics Particle path Energy equation analysis a ) 50 40 40 30 30 20 t 20 10 10 0 1 10 0 –10 0 50 100 150 200 11 12 13 14 y w Chemical energy release vs unsteadiness Results from Arienti and Shepherd, 2005 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 7 / 29
Introduction Importance of unsteadiness Previous work on reacting expanding flows Lundstrom and Oppenheim, Eckett et al., Arienti and Shepherd, Radulescu and Maxwell 20.0 10.0 5.0 ∼ a) c) e) 2.0 T 1.0 0.5 b) d) f) 0.2 10 1 10 3 10 5 10 7 10 -1 ∼ t 1-step chemical models were used Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 8 / 29
Introduction Goals of the study Purpose of the study Investigate the effect of volumetric expansion on the chemical kinetics of hydrogen-air mixtures Approach Chemistry : detailed reaction model Flow : simple reactor model to describe expansion Scope : perform detailed kinetics analyses Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 9 / 29
Methodology and calculation procedure outlines Introduction 1 Methodology and calculation procedure 2 Results and discussion 3 Conclusion 4 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 10 / 29
Methodology and calculation procedure Problem definition Specific volume behind a decaying SW P s , f , T s , f P o , T o P s , T s P o , T o P vN , T vN P o , T o U s U s U s v vN v s v s , f U s ( t = t f ) = U crit U s ( t > 0) < D CJ U s ( t = 0) = D CJ s t > 0 t = 0 t = t f Gas expands behind SW as time progresses Chemical reactions do not take place at constant pressure or volume... cooling needs to be considered Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 11 / 29
Methodology and calculation procedure Mathematical formulation (1) Three forms for the rate of SW velocity decrease Linear : U S ( t ) = D CJ − α t Exponential : U S ( t ) = D CJ exp ( − β t ) Power law : U S ( t ∗ ) = D CJ ( t ∗ ) − δ α , β , and δ are adjusted so that ∆ T / τ through isentropic expansion is the same Linear : α (∆ T ) = D CJ − U S (∆ T ) Exponential : β (∆ T ) = ln ( D CJ / U S (∆ T )) Power law : δ (∆ T ) = ln ( D CJ / U S (∆ T )) ln ( 2 ) Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 12 / 29
Methodology and calculation procedure Mathematical formulation (2) Final time of simulation D CJ − U crit S Linear : t f , Lin = α (∆ T ) ln ( D CJ / U crit ) S Exponential : t f , Exp = β (∆ T ) � 1 / δ (∆ T ) � D CJ Power law : t ∗ f , Pw = U crit S When SW becomes an acoustic wave ( M ∼ 1 ) Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 13 / 29
Methodology and calculation procedure Calculation procedure Numerical routine including the following steps Calculate D CJ Calculate P vN and T vN for U S = D CJ Calculate τ Th at P vN and T vN using a CP reactor Calculate P S (∆ T ) using the isentropic relationship for a given ∆ T Calculate the corresponding U S (∆ T ) Calculate the shock decay rates coefficients : α , β and δ Calculate t f (or t ∗ f ) for all decay rates Construct time vector in the range [0, t f ] Calculate shock velocity, U S , corresponding to each element of the time vector Calculate P S ( t ) corresponding to each value of U S ( t ) Calculate specific volume, ν , starting from P vN and T vN , and considering an isentropic expansion Calculate τ Th with the volume vs. time option (VTIM) Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 14 / 29
Results and discussion outlines Introduction 1 Methodology and calculation procedure 2 Results and discussion 3 Conclusion 4 Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 15 / 29
Results and discussion Reaction model Reaction model validation (1) Shock tube data Petersen 2003 Hidaka Skinner-Schott 1000 0.0001 1000 1E-005 Delay*[O 2] (m ol.s.dm -3) 1E-006 D elay tim e (µs) Delay tim e (µs) 1E-007 100 1E-008 100 1E-009 Φ = 1 ; XAr = 0,955 ; P5 = 101 kPa Φ = 2 ; XAr = 0,9 ; P5 = 507 kPa 1E-010 Φ = 1,03 ; XAr = 0,9847 ; P5 = 101 kPa Φ = 1 ; XAr = 0,9925 ; P5 = 375 kPa Φ = 0,25 ; XAr = 0,97 ; P5 = 101 kPa Φ = 1,47 ; XAr = 0,955 ; P5 = 101 kPa Φ = 0,5 ; XAr = 0,98 ; P5 = 375 kPa Φ = 1 ; XAr = 0,94 ; P5 = 101 kPa 10 1E-011 5 6 7 8 9 10 5 6 7 8 9 2 4 6 8 10 12 (1.104/T5) (K-1) (1.104/T5) (K-1) (1.104/T5) (K-1) Good agreement Mével et al. (7th ICHS) Ignition of H2-Air under volumetric expansion 16 / 29
Recommend
More recommend
