A phenomenological model capable of predicting the hollow structure of the stabilization zone of a lifted jet flame with and without external acoustic excitation is developed. Excitation with proper combination of frequency and amplitude, both amplification and suppression of the flow turbulence and flame stabilization can be achieved. Amplification excitation shifts the lifted flame upstream and suppression shifts downstream. By careful comparison of the natural, amplification and suppression cases, it is found that the integral length scale and the probability of the presence of a flammable premixture, the F probability, in the stabilization zone of the jet flame are the key parameters of the stabilization behavior. The model extends the traditional turbulent flame speed concept by explicitly incorporating the local large turbulent length scale, the turbulent fluctuating velocity and the F probability in the model. The model is tested against the experimental measurements, and the predicted results of the flame zone structure agree well with the measurement for both excited and unexcited cases. The mechanism of excitation on flame stabilization is further explained by the turbulent flame speed in terms of changing the local length scale, mean and fluctuation velocities, the mixture fraction, and the F probability.
|Number of pages||11|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|Publication status||Published - 1996 Apr|
All Science Journal Classification (ASJC) codes
- Mechanical Engineering