Among others, blow-out of flame and oscillatory combustion are important unstable phenomena of flame. In the first place of this article, it is pointed out that the blow-out limit isremarkably affected by the occurrence of oscillatory combustionafter some typical examples of blow-out are mentioned about. The second part of this article deals with combustion noise.Since the oscillatory combustion is the main cause of combustion noise, it is separately discussed in the last part of this paper. Firstly, a simple theory is presented regarding how theoscillation can be self-excited. From its view point, an explanation is given as to why some proposed measures are effiicient to suppress the oscillation. Secondly, Some examples of method milding the oscillation are presented.
