COMBUSTION INSTABILITY FREQUENCY MODE SHIFT OF H2/CH4 RATIO AND COMBUSTOR LENGTH IN A MODEL GAS TURBINE

摘要

Recently, the interests for energy depletion and rapid climate change have emerged around the world. Alternative and sustainable fuels (called clean fuel) and gas turbine using the fuel are the appropriate method to solve the problems. However, combustion instability is another problem for fuel-lean combustion to reduce exhaust emission in gas turbine combustor using gaseous fuel. For this reason, there are many research groups studying about combustion instability characteristics of various fuel composition. However there are not enough studies about reason of instability mechanism such as mode transition. In this paper, experimental studies on the combustion instability characteristics at various composition were conducted in a partially premixed model gas turbine combustor. The fuel composition composes of H2 and CH4. To figure out the combustion characteristics of various test conditions, combustor length, heat load and H2/CH4 ratio were selected. NOx emission was not affected with varying combustor length and high H2 ratio and heat load affect the high NOx emission. On the other hand, instability frequency was affected on combustor length because the combustion zone was narrow. Furthermore, combustion instability mode shift phenomenon occurred at high H2 content and it was confirmed that the combustion instability frequency was longitudinal mode of the combustor. The results are would be attributed to key parameters for the combustor design and operation conditions.