A lean premixed swirling combustor was constructed. The data of frequency of instable fluctuation

amplitude and distribution of pressure oscillation and the response of heat release from varying equivalent ratio were applied to obtain the nonlinear development of combustion instability from stability to limit cycle. A thermoacoustic network model with low orders was utilized to analyze the oscillating solutions for the experiments. The results from the experiments show that a typical nonlinear process can describe the root mean square of pressure oscillation and heat release response with the increasing equivalent ratio

and the flame has significantly different structures in different states. The results indicate that the frequency error between the calculation and experiment is less than 1% when the equivalent ratio is less than 0.7

while the frequency error is 13% when the equivalent ratio is greater than 0.7.