Investigation of the ammonia-methane-air laminar burning characteristics at high temperatures and pressures

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作   者：

Zhou Q.;  Tian J.;  Zhang X.;  Cui Z.;  Ye M.;  Wang Q.;  Yang H.;  Shu D.; 

作者机构：

Dalian University of Technology; 

关键词：

Markstein length;  Reaction order;  Laminar burning velocity;  Temperature exponent;  CVCC;  Flame instability; 

期刊名称：

Fuel: A journal of fuel science

i s s n：

0016-2361

年卷期：

2024 年 365 卷 Jun.1 期

页   码：

1.1-1.17

页   码：

摘   要：

? 2024 Elsevier LtdNowadays, ammonia is considered a potential carbon-free fuel. However, the research on the combustion characteristics at high temperatures and pressures which has significance to the research of real engine in-cylinder combustion is little. In this study, the Laminar Burning Velocity (LBV) and Markstein Length (Lb) of NH3-air at high temperature and high pressure were investigated within a constant volume combustion chamber, and methane with various energy ratios was introduced for comparative analysis, as well as the reaction order and temperature exponent were calculated. Furthermore, flame instability in spherical expansion flames has also been studied in depth. The results show that when initial temperature (Tu) = 450 K, the reaction order of ammonia ranges from 1.32 to 1.48, when Tu = 500 K, the reaction order of ammonia ranges from 1.24 to 1.41. The temperature exponent is calculated between 1.88 and 2.68, when Tu from 400 K to 550 K. In the range of Tu from 400 K to 500 K, initial pressure (p) from 0.5 MPa to 1.5 MPa, Φ from 0.8 to 1.3 and methane energy ratio (ECH4) from 0 to 0.8, increasing Tu and ECH4, decreasing p all have the potential to increase the LBV. Notably, the optimal equivalence ratio shifts from 1.1 to 1.0 with the increase of ECH4. The Lb is unaffected by variations in temperature, decreasing with increasing pressure but increasing with increasing equivalence ratio. As the ECH4 increases, Lb increases within 0.8 < Φ < 1.0, but decreases within 1.1 < Φ < 1.3. As the p and ECH4 increase, the hexagonal structure of the flame surface by an increasing trend, indicating an increase in hydrodynamic instability, while the temperature has little effect on this instability. In addition, as the equivalence ratio increases, the hydrodynamic instability first increases and then decreases. With an increase in Tu, Φ, and ECH4, the thermal diffusive instability is slightly weakened, and the response to pressure is not significant. Lower flame velocity of ammonia, and decreasing Tu, increasing the p, and decreasing ECH4 enhances the effect of buoyancy on the flame, which becomes more pronounced as the flame develops.