Self exciting oscillation in gas fired appliances leads to abnormal combustion noise which is focused in this work. For studying this phenomena and modeling abnormal combustion noise a simple hand made instrument was made. Then the property of fundamental parts of unit is studied and also some practical methods for reducing the loud noise are given. These methods are based on modification of the fundamental parts of unit. The mathematical model of this phenomenon is illustrated and also the stability criteria for the unit based on this model is given. Then the effect of changing excitation point in this phenomenon is studied and finally the experimental stability diagram based on modification on fuel/air ratio is given.
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Author: Mohsen Mohebbi
Source: Blekinge Institute of Technology
Contents
1 Notation
2 Introduction
3 Modeling of Abnormal Combustion Noise
3.1 Experiment Equipment
3.2 Performing Abnormal Combustion Noise
4 Frequency Domains
4.1 Determination of Frequency Oscillation
4.2 Measuring Resonance Frequency of Combustion Chamber
4.3 Calculating Resonance Frequency
5 Difference between Resonance Problem and Abnormal Combustion Noise
6 Some Simple Ways for Reducing Combustion-Drive Oscillation 18
7 Role of Flame
8 Transfer Function
8.1 Transfer Function of the Combustion Chamber 23
8.2 Frequency Response Function Development for Combustion
Chamber 23
8.3 Transfer Function of Flame 26
9 Build up of Self Excited Oscillation
10 Starting of Self Excited Oscillation
10.1 Stability Criteria for Feedback Loop 32
11 Effect of Burner Inserting Depth
12 Modification of the Flame
13 Conclusion
14 References
Appendices
A Modification of (Fuel/Air) ratio when the combustion chamber
length is 610 millimeter
B Modification of (Fuel/Air) ratio when the combustion chamber
length is 910 millimeter