EFFECT OF GLOBAL ACCELERATION IN THE ACOUSTIC RESPONSE OF PREMIXED FLAME AND ANALYSIS OF ACOUSTIC INSTABILITY OF COMBUSTION CHAMBER

Abstract

The aim of this present paper is the experimental analysis of the effect of global acceleration in the response function of premixed flame and acoustic instability of combustion chamber. The global acceleration is an addition term in the Navier- Stokes momentum equation governing the dynamics of heat source. Global acceleration occurs due to acoustic field in the acoustic duct. In this experimental study, the response function is calculated for two cases. In the first case, response function is obtained in the absence of acoustic duct excluding global acceleration term. On the other hand, in the second case, response function is obtained in the presence of acoustic duct including global acceleration term with various flame locations. The response function measured over a range of acoustic excitation of varying amplitude of frequencies. The measurement of response function with and without duct in this experiment due to maximum forcing as .The obtained response function behaves similarly to the prediction by linear kinematic theory at low amplitude forcing { < 0.3} of acoustic velocity excitation. The phase of response function remains closely to linear at low forcing frequencies, regardless of the forcing amplitude. The air flow rate varies from 5 lpm to 8 lpm and fuel flow rate varies from 0.12 standard liters per minute to 0.3 standard liters per minute this corresponds to a variation of the equivalence (Ф) ratio from 0.65 to 0.9. Four loud speakers are used to excite the flame at a particular frequency range from 150to 500 Hz.