Analysis Technique to Determine the Underlying Wave Structure of Combustion Instabilities From Surface Mounted High Response Static Pressure Sensors

Screech is an acoustic combustion instability that drives pressure oscillations much greater than normal combustion turbulent fluctuations. Discrete Fourier Transforms (FTs) are commonly utilized to analyze high resolution pressure sensor data. This isolated sensor analysis approach provides valuable frequency information, but since sensors are usually not located at peak amplitudes, resultant waves may be rotating and maximum amplitudes may be difficult to determine. Understanding the underlying counter-traveling or counter-rotating resultant wave structure is useful to develop screech mitigation strategies and necessary to quantify the impact of fuel schedule or geometry changes. A screech wave analysis methodology (SWAM) is developed for transverse, longitudinal, and complex modes. Typically, only two or three sensors are located in a transverse plane and in a longitudinal plane. The SWAM approach utilizes all the sensors in an analysis plane to provide an integrated sensor analysis. SWAM results are evaluated based upon exact wave solutions, and demonstrated with test data.