Fuzzy Synthetic Evaluation of Flame Combustion Stability Based on Time Frequency Analysis and Higher­Order Statistics

L.I. Jie1, L.I.U. Shi1, L.E.I. Jing1, B.A.I. Xiang2, C.H.E.N. Wei2, D.O.N.G. Xue2, W.A.N.G. Neng2 and

X.U. Wei2

1. Innovative Research Team of ‘ Program for Changjiang Scholars and Innovative Research Team in University’ , North China Electric Power University, Beijing 102206, China,

   leejay1986@163.com

2. School of Energy and Power Engineering, North China Electric Power University, Beijing 102206,

China

ABSTRACT

The physical and chemical mechanisms of flame combustion are complex and flame stability is difficult to evaluate accurately. A synthetic evaluation method for the stability of flame combustion using fuzzy synthetic judgment is proposed which is based on the extraction of flame radiation characteristic parameters from measured data. A series of combustion conditions with various fuel/air ratios have been investigated. Flame radiation luminance fluctuating information is acquired on low­cost flame detection device. Power spectrum of frequency domain and bi­spectral information of phase domain are derived from time domain signals based on fast fourier transform (fft) and higher order statistics based upon wavelet de­noising methodology. The time frequency characteristics and the features of the bi­spectrum under various combustion conditions are qualitatively analysed, and the characteristic parameters which reflect time domain, frequency domain and phase domain respectively are extracted. A mathematical model for comprehensive fuzzy evaluation has been constructed, and a stability index system for the evaluation of flame combustion established. It is demonstrated that this method is feasible and effective, and that the evaluated results can be used as a support tool for process engineers for improving combustion conditions.

Keywords stability of flame? time frequency analysis? bi­spectrum? fuzzy synthetic evaluation