Suppression of Combustion Instability by Controlling Spray Properties in Liquid-Fueled Combustors

摘要

This paper describes an experimental investigation of 'slow' active control of combustion instabilities by changing the liquid fuel spray properties. Such control approach whose characteristic time is generally much longer than that of the period of the unstable oscillations needs 'one time' variation of control inputs in response to changes in engine operating conditions. Using two types of fuel injectors that can produce large controllable variation of fuel spray properties, this study examined the dependence of acoustics-combustion process coupling, i.e., the driving of combustion instabilities upon liquid fuel spray droplet size, which affects the characteristic combustion time and, thus, the coupling between the acoustics and the combustion process. It was demonstrated that changing the spray characteristics significantly damps the instabilities. The results of this study strongly suggest that 'slow' active control of the fuel spray droplet sizes with advanced injectors in real engines could be used to prevent the onset of detrimental combustion instabilities.