Experimental Study on the Effect of Ethylene on the Detonation Wave Initiation of Coal Powder/oxygen Mixture

doi:10.12382/bgxb.2022.0600

Abstract

Abstract:

The influence mechanism of ethylene on the detonation initiation characteristics of coal powder/oxygen mixture is studied to realize the reliable ignition of the coal powder continuous rotating detonation engine. At the initial pressure of 100kPa, an electric ignition with high energy is used to carry out the direct detonation initiation experiments on the coal powder/oxygen mixture with and without the ethylene. The ignition energy is calculated by measuring the pressure of explosive wave produced via a high-energy electric spark in air. The coal powder/oxygen mixture cannot detonate without ethylene under the action of effective ignition energy of 6.3J. In this energy, if the ethylene with the equivalence ratio of 0.5 is added, the coal powder/oxygen mixture can be successfully initiated. If the effective ignition energy is reduced to 3.6J to made it be lower thanthe critical initiation energy of ethylene/oxygen mixture with an equivalent ratio of 0.5. the detonationcould be onset after adding coal powder. The above studies show that a certain amount of detonable gas (such as ethylene) needs to be added for the dirct detonation initiation of coal powder/oxygen mixture. On the other hand, the addition of coal powder can also broaden the detonation limit of ethylene/oxygen mixture. The results of this study can provide theoretical basis and technical support for the ignition of coal continuous rotating detonation engine.

Key words: powder continuous rotating detonation engine, detonation, coal powder, direct initiation, critical initiation energy, gas-solid two-phase detonation

CLC Number:

O381

LUO Yongchen, XU Han, ZHANG Feng, ZHENG Quan, WENG Chunsheng. Experimental Study on the Effect of Ethylene on the Detonation Wave Initiation of Coal Powder/oxygen Mixture[J]. Acta Armamentarii, 2024, 45(3): 754-762.

Figures/Tables 18

Fig.1 Schematic diagram of experimental setup

Fig.2 Nozzle structure

Fig.3 Operation time sequences for ignition experiment

Fig.4 Mash as a function of rsh/r0 for a spherical explosive wave from ideal point energy source[21]

Table 1 Related parameters related under different ignition energies (C=20μF,p01=101.35kPa)

参数	高点火能量	低点火能量
电压U/kV	14	12
超压p_sh/kPa	1.75	1.15
爆炸波马赫数Ma_sh	1.575	1.405
归一化传播距离r_sh/r₀	1.26	1.52
激波能量E_sh/J	6.3	3.6

Table 2 Proximate analysis of coal sample

成分	总水分	挥发分	灰分	固定碳
质量分数/%	1.13	3.48	0.61	95.91

Table 3 Test conditions

工况	案例	燃料	氧化剂	E_sh/J	当量比
工况	案例	燃料	氧化剂	E_sh/J	煤粉	C₂H₄	全局
无乙烯氛围下煤粉-氧气点火实验	1	煤粉	氧气	3.6	0.5	0	0.5
	2	煤粉		3.6	0.7	0	0.7
	3	煤粉		6.3	0.5	0	0.5
	4	煤粉		6.3	0.7	0	0.7
在乙烯氛围下,采用高于临界起爆能量的点火能量对煤粉-氧气进行点火实验	5	C₂H₄	氧气	6.3	0	0.5	0.5
	6	煤粉+C₂H₄		6.3	0.2	0.5	0.7
	7	煤粉+C₂H₄		6.3	0.5	0.5	1.0
	8	煤粉+C₂H₄		6.3	0.8	0.5	1.3
	9	煤粉+C₂H₄		6.3	1.0	0.5	1.5
在乙烯氛围下,采用低于临界起爆能量的点火能量对煤粉-氧气进行点火实验	10	C₂H₄	氧气	3.6	0	0.5	0.5
	11	煤粉+C₂H₄		3.6	0.2	0.5	0.7
	12	煤粉+C₂H₄		3.6	0.5	0.5	1.0
	13	煤粉+C₂H₄		3.6	0.8	0.5	1.3
	14	煤粉+C₂H₄		3.6	1.0	0.5	1.5

Fig.5 Pressure curve of coal powder/oxygen ignition experiment without ethylene(Esh=6.3J,Case 3)

Table 4 Coal powder/oxygen ignition experiment results without ethylene

案例	E_sh/J	GER	现象
1	3.6	0.5	无反应
2	3.6	0.7	无反应
3	6.3	0.5	无反应
4	6.3	0.7	无反应

Fig.6 Pressure-time curve of successful detonation initiation of ethylene/oxygen with the equivalence ratio of 0.5 (Esh=6.3J, Case 5)

Fig.7 Initiation energy at different equivalence ratios of C2H4/O2 at the initial pressure of 100kPa[23]

Fig.8 Pressure-time curve of successful detonationinitiation of coal powder/oxygen with the global equivalence ratio of 1.5 under high ignition energy with ethylene (Esh=6.3J,Case 9)

Fig.9 v/vC-J and p/pC-J of coal powder/oxygen at different global equivalence ratios with ethylene(Esh=6.3J)

Table 5 Experimental results of ignition of coal powder/oxygen at different global equivalence ratios with ethylene under high ignition energy(Esh=6.3J)

案例	GER	v/v_C-J/%	p/p_C-J/%	直接点火
5	0.5	92.6	90.9	Yes
6	0.7	86.8	95.9	Yes
7	1.0	86.7	98.2	Yes
8	1.3	90.3	97.7	Yes
9	1.5	88.6	100.0	Yes

Fig.10 Pressure-time curve of unsuccessful detonation initiation of ethylene/oxygen with the equivalence ratio of 0.5(Esh=3.6J, Case 10)

Fig.11 Pressure-time curve of successful detonation initiation of coal powder/oxygen with the global equivalence ratio of 1.5 under low ignition energy with ethylene(Esh=3.6J,Case 14)

Fig.12 v/vC-J and p/pC-J of coal powder/oxygen at different global equivalence ratios with ethylene (Esh=3.6J)

Table 6 Experimental results of ignition of coal powder/oxygen at different global equivalence ratios with ethylene under low ignition energy(Esh=3.6J)

案例	GER	v/v_C-J/%	p/p_C-J/%	直接点火
10	0.5			No
11	0.7	82.9	94.4	Yes
12	1.0	86.4	98.5	Yes
13	1.3	82.7	97.0	Yes
14	1.5	87.1	98.9	Yes

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