The self-excited thermoacoustic instability behavior of a premixed hedge combustor with an elbow-connection or T-shape supply system

The self-excited thermoacoustic instability (SETAI) frequently occurs in combustion equipment, leading to intense mechanical vibration, big noise and flame instability. SETAI poses a substantial challenge to the advancement of combustion technology, chiefly due to its complex mechanism. Our previous research has demonstrated that altering the premixed chamber length upstream of furnace can impact the interaction between heat release and sound pressure oscillations, which potentially enables SETAI control. However, supply duct is generally not straight, and changing the premixed section is impractical and unsafe. This paper aims to investigate the influence of introducing elbows and adjusting the supply duct length preceding the premixing stage on SETAI behavior. The goal is to offer guidance for the safe and convenient control of SETAI. Finds reveal that incorporating an elbow in the premixed chamber or changing its position does not affect sound wave propagation along the duct’s center axis within a low frequency regime when maintaining a constant total equivalent length. In systems with both separate and premixed sections, the oscillation pattern is determined by the total time required for acoustic propagation throughout the entire supply system. Consequently, modifications to either of these lengths can impact SETAI.