Experimental Study on Accelerative Characteristics of Syngas Laminar Premixed Flames

doi:10.12068/j.issn.1005-3026.2024.09.015

Abstract

Abstract:

A systematic investigation on accelerative characteristics of syngas laminar premixed flames is conducted using the visual experimental platform of constant volume combustion chamber. The decoupling control of self?instability is realized by adjusting the equivalence ratio and oxygen?nitrogen ratio of gas mixture， allowing for an analysis of flame acceleration stages， onsets， and acceleration exponents. Three distinct stages of laminar flame propagation outwardly are identified， namely quasi?steady， transitional acceleration， and saturated acceleration. The order of four onsets is as follows： crack branching≈transitional acceleration<uniform cellularity≈saturated acceleration. The acceleration exponents in saturated acceleration stage are in the range of 1.1~1.2， showing independent on Lewis number and density ratio. The results indicate that the flame intrinsic instability can have a significant promotion on the onset of laminar flame acceleration， while it does not affect the flame acceleration strength in saturated acceleration stage.

Key words: flame accelerative propagation, onset, acceleration exponent, laminar premixed flames, syngas

CLC Number:

TK 91

Hao-ran ZHAO, Gang LI, Jin-hua WANG, Zuo-hua HUANG. Experimental Study on Accelerative Characteristics of Syngas Laminar Premixed Flames[J]. Journal of Northeastern University(Natural Science), 2024, 45(9): 1334-1341.

Figures/Tables 9

Fig.1 Schlieren images of flame propagation （p=0.3 MPa，φ=0.8,Tad=2 000 K）

Table 1 Experimental conditions and relative parameters

V_CO/V $H 2$	p/MPa	T/K	φ	T_ad/K	Le_eff	σ	Ma
65/35	0.3	353	0.6~1.0	2 000	0.92~1.03	5.09	2.10~3.46
65/35	0.3	353	1.0	1 600~2 500	≈1	4.19~6.11	2.32~5.26
65/35	0.5	353	0.6~1.0	2 000	0.92~1.03	5.09	2.06~3.51
65/35	0.5	353	1.0	1 600~2 400	≈1	4.19~5.91	2.34~4.78
15/85	0.3	353	0.6~1.0	2 000	0.72~1.08	5.06	-0.93~4.11
15/85	0.3	353	1.0	1 600~2 400	≈1	4.18~5.88	2.12~5.94

Table 1 Experimental conditions and relative parameters

V_CO/V $H 2$	p/MPa	T/K	φ	T_ad/K	Le_eff	σ	Ma
65/35	0.3	353	0.6~1.0	2 000	0.92~1.03	5.09	2.10~3.46
65/35	0.3	353	1.0	1 600~2 500	≈1	4.19~6.11	2.32~5.26
65/35	0.5	353	0.6~1.0	2 000	0.92~1.03	5.09	2.06~3.51
65/35	0.5	353	1.0	1 600~2 400	≈1	4.19~5.91	2.34~4.78
15/85	0.3	353	0.6~1.0	2 000	0.72~1.08	5.06	-0.93~4.11
15/85	0.3	353	1.0	1 600~2 400	≈1	4.18~5.88	2.12~5.94

Fig.2 Flame propagation stages under different Lewis numbers and density ratios

Fig.3 Critical flame radii under different effective Lewis numbers

Fig.4 Critical flame radii under different density ratios

Fig.5 Experimental results of critical Peclet numbers

Fig.6 Empirical fitting formula of critical Peclet numbers of syngas

Fig.7 Evaluation of acceleration exponent model

Fig.8 Acceleration exponents under different Lewis numbers and density ratios

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