Experimental Study On The Thermoacoustic Instability In The Premixed Rijke Combustor

With the improvement of environmental requirements, premixed poor combustion gas turbines has been widely used in industry. But the thermoacoustic instability causes bad effects like noise and vibration during its work process. Using the Rijke tube as a study object this thesis studied the thermoacoustic instability phenomenon by the mathematical derivation and experiments.First we clarified the discovery of thermoacousitic phenomenon and the development of the corresponding theory, especially the difference between the line and nonline thermoacoustic theory. These provided the theoretical basis for our expriments. Besides, we introduced the research development of the thermoacoustic application.We designed and built a premixed-combustion Rijke-tube thermoacoustic instability experimental setup, including the fuel import system, combustion, temperature measurement system and pressure measurement system. The difficulty of our experiments was the pressure signal acquisition. We developed a high-speed continuous real-time data collection program to avoid the signal distortion.The mathematical derivation on the thermoacoustic vibration frequency of a Rijke tube was carried out by adopting Separation of Variables. Neglecting the high-order trace, we got the linear analytical solution of thermoacoustic vibration frequency. A tube with 40 mm in diameter and 1066 mm in length and a square tube with 82mm in width and 1540mm in length was used in the experimental setup and we obtained the thermoacoustic vibration frequency. The results show that the analytical solutions of thermoacoustic vibration frequency agree well with the experimental data.A Rijke tube with 40 mm in diameter and 1066 mm in length was used in the experimental setup. The flame was located at the quarter of the tube. Changing the equivalent ratio and combustion power, we studied the influence of thermoacoustic domino effect on the pressure field and temperature field, got the change trend of some parameters such as thermoacoustic instability intensity, frequency and temperature. The results show that on the thermoacoustic instability intensity and temperature the influence of equivalent ratio and combustion power is huge, but on the frequency the influence of them is little.