Abstract
In this study, the effect of flame intrinsic instability on the flame structural characteristics of hydrogen/air mixtures premixed at various equivalence ratios were experimentally investigated from the macroscopic and microscopic perspectives, respectively. The correlation degree and the relative deformation degree were defined to quantitatively study the global flame structural characteristics. Peak detection was used to capture the characteristic length of the flame and fast Fourier transform was adopted to study the components of the fluctuation of the flame front. The results show that with the development of flames, the wrinkles in the flame front increase and the correlation degree of the flame decreases. The relative deformation degree of the flame first decreases and then increases. When the equivalence ratio is 0.6, the average characteristic length initially exhibits an increasing trend, followed by a decreasing trend. The average characteristic length scale gradually increases, and the growth rate gradually decreases when the equivalence ratio ranges from 0.70 to 0.99. With the increase in the wavenumber, the amplitude of the corresponding disturbance exhibited an increasing trend followed by a decreasing one. With the development of the flame, the maximum amplitude of the disturbance shows a reverse trend, i.e., first decreasing and then increasing. The disturbances with smaller wavelengths could be further developed.
Highlights
The automotive industry is a pillar of the national economy, and it is the crystallization of human wisdom and a main driver of macroeconomic growth and stability, which significantly promotes the development of human civilization
Extensive research efforts have been devoted to the experimental investigation of the feasibility of using pure hydrogen as fuel in the internal combustion engine, and the results showed a significant increase in the thermal efficiency of the engine
The effect of flame intrinsic instability on the flame structural characteristics of hydrogen/air mixture were investigated under atmospheric pressure and temperature
Summary
The automotive industry is a pillar of the national economy, and it is the crystallization of human wisdom and a main driver of macroeconomic growth and stability, which significantly promotes the development of human civilization. The flame in the internal combustion engine with gasoline as fuel is an expanding flame; the research on laminar premixed combustion is of great significance to the understanding of combustion mechanism and the study of turbulent combustion [11,12]. The flame surface begins to become unstable and this results in the exponential growth of the flame radius over time, rather than monotonous growth [20] For this reason, the effect of flame intrinsic instability attracts the attention of researchers, and it is always considered in combustion models [21]. In order to study the effect of the flame intrinsic instability on the flame structure, fractal geometry and statistical theory are important means of quantifying the cellular structure. The structure of flame front in the near ignition electrodes region was systematically analyzed
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