Analysis and Experimental Investigation of Pressure Oscillation in the Combustion Chamber of a Subscale Solid Rocket Motor

This study aims to predict pressure oscillation in a full scale solid rocket motor from the measured data of a subscale one. Therefore, the oscillatory pressure in a subscale solid engine was measured using accurate and high resolution sensors and data acquisition system. The importance of this study is due to the roll of pressure fluctuations into the motor on generating vibrations in structure of the motor and its payload. The frequency of pressure oscillation in a solid rocket motor changes around the acoustic mode frequency which has inverse relation with the length of the motor combustor. Therefore, in the short-length motors the high frequency oscillations occur. In other words, a data acquisition equipment for a subscale solid rocket motor must be have high accuracy and resolution. In the present work, a piezoelectric pressure transducer and an accurate data acquisition system have been used. The frequency of pressure oscillation of the subscale motor was measured around 10 kHz that indicating coincidence of the acoustic mode frequency of vortex shedding and shows a good agreement with calculation using the existing analytical relation. In the end, the analysis of data was performed using proper signal processing tools such as FFT of oscillatory signals